EP0031838A1 - Materiau composite renforce avec des fibres et articles formes - Google Patents

Materiau composite renforce avec des fibres et articles formes

Info

Publication number
EP0031838A1
EP0031838A1 EP80901403A EP80901403A EP0031838A1 EP 0031838 A1 EP0031838 A1 EP 0031838A1 EP 80901403 A EP80901403 A EP 80901403A EP 80901403 A EP80901403 A EP 80901403A EP 0031838 A1 EP0031838 A1 EP 0031838A1
Authority
EP
European Patent Office
Prior art keywords
fibers
matrix
cement
particles
ultra fine
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP80901403A
Other languages
German (de)
English (en)
Inventor
Zoltan FÖRDÖS
Hans Henrik Bache
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Aalborg Portland AS
Original Assignee
Aalborg Portland AS
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Aalborg Portland AS filed Critical Aalborg Portland AS
Publication of EP0031838A1 publication Critical patent/EP0031838A1/fr
Withdrawn legal-status Critical Current

Links

Classifications

    • E—FIXED CONSTRUCTIONS
    • E04—BUILDING
    • E04C—STRUCTURAL ELEMENTS; BUILDING MATERIALS
    • E04C5/00—Reinforcing elements, e.g. for concrete; Auxiliary elements therefor
    • E04C5/07—Reinforcing elements of material other than metal, e.g. of glass, of plastics, or not exclusively made of metal
    • C—CHEMISTRY; METALLURGY
    • C03—GLASS; MINERAL OR SLAG WOOL
    • C03C—CHEMICAL COMPOSITION OF GLASSES, GLAZES OR VITREOUS ENAMELS; SURFACE TREATMENT OF GLASS; SURFACE TREATMENT OF FIBRES OR FILAMENTS MADE FROM GLASS, MINERALS OR SLAGS; JOINING GLASS TO GLASS OR OTHER MATERIALS
    • C03C25/00—Surface treatment of fibres or filaments made from glass, minerals or slags
    • C03C25/10—Coating
    • C03C25/1025—Coating to obtain fibres used for reinforcing cement-based products
    • C—CHEMISTRY; METALLURGY
    • C03—GLASS; MINERAL OR SLAG WOOL
    • C03C—CHEMICAL COMPOSITION OF GLASSES, GLAZES OR VITREOUS ENAMELS; SURFACE TREATMENT OF GLASS; SURFACE TREATMENT OF FIBRES OR FILAMENTS MADE FROM GLASS, MINERALS OR SLAGS; JOINING GLASS TO GLASS OR OTHER MATERIALS
    • C03C25/00—Surface treatment of fibres or filaments made from glass, minerals or slags
    • C03C25/10—Coating
    • C03C25/24—Coatings containing organic materials
    • C03C25/26—Macromolecular compounds or prepolymers
    • C—CHEMISTRY; METALLURGY
    • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B14/00—Use of inorganic materials as fillers, e.g. pigments, for mortars, concrete or artificial stone; Treatment of inorganic materials specially adapted to enhance their filling properties in mortars, concrete or artificial stone
    • C04B14/38—Fibrous materials; Whiskers
    • C04B14/42—Glass
    • C—CHEMISTRY; METALLURGY
    • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B20/00—Use of materials as fillers for mortars, concrete or artificial stone according to more than one of groups C04B14/00 - C04B18/00 and characterised by shape or grain distribution; Treatment of materials according to more than one of the groups C04B14/00 - C04B18/00 specially adapted to enhance their filling properties in mortars, concrete or artificial stone; Expanding or defibrillating materials
    • C04B20/10—Coating or impregnating
    • C—CHEMISTRY; METALLURGY
    • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B26/00—Compositions of mortars, concrete or artificial stone, containing only organic binders, e.g. polymer or resin concrete
    • C04B26/02—Macromolecular compounds
    • C—CHEMISTRY; METALLURGY
    • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B28/00—Compositions of mortars, concrete or artificial stone, containing inorganic binders or the reaction product of an inorganic and an organic binder, e.g. polycarboxylate cements
    • C—CHEMISTRY; METALLURGY
    • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B40/00—Processes, in general, for influencing or modifying the properties of mortars, concrete or artificial stone compositions, e.g. their setting or hardening ability
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02W—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO WASTEWATER TREATMENT OR WASTE MANAGEMENT
    • Y02W30/00—Technologies for solid waste management
    • Y02W30/50—Reuse, recycling or recovery technologies
    • Y02W30/91—Use of waste materials as fillers for mortars or concrete

Definitions

  • Fiber- reinforced composite materials and shaped articles Fiber- reinforced composite materials and shaped articles .
  • the present invention relates to new developments in composite materials and shaped articles comprising reinforcing fibers .
  • cement-bound materials containing fibers of alkali-resistant glass show a considerable reduction in their strength properties over prolonged periods . It would be desirable to obtain generally better strength properties in glass fiber-reinforced cement-bound materials , both with respect to early strength and with respect to the preservation of the strength .
  • the present invention relates to systems which provide a suitable contact zone around reinforcing fibers , in particular silicate-con - taining fibers such as glass fibers and mineral fibers, in fiber-rein forced composite materials , so as to obtain conditions at the fiber surface which chemically and/or mechanically will protect the fibers and, hence, improve the properties of the fiber- reinforced compo- site materials .
  • reinforcing fibers in particular silicate-con - taining fibers such as glass fibers and mineral fibers
  • Such systems comprise fibers which, prior to their incorporation in the matrix, have been provided with a contact zone coating of a special type, in particular comprising an inor ⁇ ganic or organic coating, typically a coating of a polymer, optio ⁇ nally with a special kind of ultra fine particles incorporated therein or binder matrices in which such special fine particles have been incorporated, and in particular a combination of these two systems .
  • a further measure according to the invention comprises establishing chemical conditions at the. fiber surface which will serve to poison catalysts which are known to be involved in the chemical deteriora- tion of the fibers .
  • the systems of the invention are of importance, not only in con ⁇ nection with glass fibers, but generally in connection with any type of reinforcing fiber which might be subject to chemical and/or mechanical attacks in the surroundings in which it is arranged in a composite material and/or where the provision of a special kind of fine particles at the fiber-matrix interface results in improved performance of the resulting composite material.
  • the contact zone around reinforcing fibers comprises ultra fine silica particles or a coherent structure formed from such particles, or, expressed in another manner, the fiber-matrix interface comprises such particles .
  • ultra fine silica is intended to designate SiOarea-rich particles having a specific surface of 50,000 - t r 2
  • a preferred product of this type is produced as a by-product in the production of ferrosilicium and silicon metal in electrical furnaces and comprise particles in a particle- size range from about 50 A to about 0.5 ⁇ , typically in the range from about 200 A to about 0.5 ⁇ , the partic ⁇ les being spherical particles of silica of amorphous character and having a high degree of reactivity.
  • the partic ⁇ les being spherical particles of silica of amorphous character and having a high degree of reactivity.
  • OM particles partially dissolve with reprecipitation of solid in the dis ⁇ solved phase so as to form a coherent structure of particles , bound together by reprecipitated material.
  • Other- ultrafine SiO 2 ⁇ containing particles may be used for the purpose of the present invention, such as particles prepared by other vapour phase processes such as combustion of silicon tetrachloride with natural gas to form hydrogen chloride and silicon dioxide vapour, or particles prepared as a sol by neutralizing sodium silicate with acid by dialysis, by electrodialysis , or by ion exchange.
  • a list of commercial silica sols . is given in R.K. Her (in “Surface and Colloid Science” , editor
  • Ultra fine silica shows a number of unique advantages in a contact zone or, expressed in another manner, as a component of an interface between a reinforcing fiber and the matrix in which t the fiber is embedded.
  • factors contributing to the deterioration of the glass fiber are, such as mentioned above, partly of mechanical and partly of chemical cha ⁇ racter:
  • the mechanical deteriorating factors may be mentio ⁇ ned the tendency to surface damage (microcracking) due to contact between the glass fibers and sharp particles of the cement-based matrix, including sharp cement particles or calcium hydroxide crystals formed during the curing of the cement paste, the tenden ⁇ cy to formation of icrocracks being increased as soon as any deformation under load of the matrix takes place so as to displace the glass fiber (even when this is in microscopic degree) in the matrix.
  • the strength and toughness of materials depend on the fracture toughness which is a measure of the energy required to open a crack.
  • the fracture toughness in connection with fiber pull-out is, according to "Modern Oxide Materials” edited by B . Cockayne and D . W. Jones, Academic Press, London and New York, 1972, article by B . Harris, "Oxides in Composites"
  • w f is the volume concentration of fibers
  • ⁇ is the bond strength
  • 1 is the critical fiber length (1 being proportional to the fiber strength, the fiber diameter, and the reciprocal of the bond strength)
  • d is the fiber diameter
  • a coating containing the spherical, unsharp ultra fine silica particles serves to fill voids in the matrix at the fiber surface which might otherwise be subject to precipitation of sharp crystals , and in particular, thereby serves to avoid the formation of microcracks and to fill up existing microcracks to function as a barrier against intrusion of any crystal growth which might tend to establish a stress field in the glass fiber.
  • a contact zone around a glass fiber and comprising a high density of ultra fine silica particles , or a coherent structure formed from such particles may tend to serve as a surface jacket which will contribute to a homogeneous distribution of the forces applied on the glass fiber surface under loading of the matrix and tend to take over part of the load which the unjacketed glass fiber would otherwise have had to bear alone. From a chemical point of view, the high reactivity of the ultra fine silica particles , and their high
  • OMPI solubility in alkaline solutions will tend to form a chemical micro- environment around the glass fibers which will shield the glass fibers against excessive alkaline influence from the curing cement matrix.
  • the condi- tions established through the presence of the silica dust will tend to show a lower alkalinity around the glass fibers, and the capabi ⁇ lity of the ultra fine silica particles to form a coherent unitary structure during the conditions under which the cement matrix cures will tend to build up a more rigid micro-jacket around the glass fibers which will not only enhance the above-mentioned load distribution effect, but will also function to establish static condi ⁇ tions in the glass fiber environment which will substantially shield against migration of alkaline material against the fiber in the final cured matrix.
  • amorphous ultra fine silica particles are readily reactive with calcium hy ⁇ droxide solution to form calcium silicate hydrate.
  • calcium silicate hydrate may form an amorphous gel, and in general, the solid structure consti ⁇ tuted by the solidified calcium silicate hydrate will become stronger and stronger with time.
  • the above- discussed contact zone which chemically and mechanically protects reinforcing fibers in a matrix and enhances the utilization of the strength of reinforcing fibers is obtained by providing reinforcing fibers with a surface coating which establishes controlled bond strength between the fibers and the matrix to obtain controlled sliding of the fibers in the matrix, and providing ultra fine silica particles in the contact zone adjacent to the fiber surface, either by including the ultra fine silica par ⁇ ticles in the surface coating, or by providing, in the matrix in which the fibers are to be incorporated, homogeneously dispersed ultra fine silica particles or a coherent unitary structure formed from such homogeneously dispersed ultra fine particles , or by a combination of these measures .
  • the reinforcing fibers which are provided with a coating may typi- cally be glass fibers such as discussed above .
  • the glass from which the fibers are made may be any glass type suitable for fiber production, such as type A, E , C, S, or the so-called "alkali- resistant glass” .
  • the glass fibers to be coated may be in the form of single fila ⁇ ments , or they may be fiber bundles (a fiber bundle of glass fibers typically comprises about 200 filaments of a diameter of about lO ⁇ . Between these filaments , there is only little space, the average inter-filament distance being 1 - 3 ⁇ ) , or they may be rovings made from about 30 - 60 bundles .
  • Application of a coating on single filaments or bundles may be combined with the filament or bundle production process or may be performed as a subsequent operation in that the fibers or bundles are passed through a suitable sizing or coating bath which optionally contains ultra fine silica particles . When the ultra fine silica particles are included in the bath, the bath should have a viscosity adapted to permit silica particles from the bath to be entrained with the glass fiber filaments or bundles .
  • a surface layer which shields the fibers against the surroundings and, in the matrix in which the fibers are later incorporated, integrate in the contact zone around the fibers and contribute to the above-mentioned mechanical and (especially when ultra fine silica particles are included) chemical protection of the fibers .
  • Potential notch effects* caused by small defects (cavities or microcracks) in the glass surface may be minimized as the sizing or coating, optionally containing the ultra fine silica particles, covers the cavities or microcracks such as described above and constitutes a barrier against chemical and mechanical intrusion .
  • the amount of ultra fine silica particles to be incorporated in the sizing is preferably adapted to the viscosity of the sizing bath in such a manner that the resulting coating of the fibers includes ultra fine silica corresponding to complete coverage of the surface with a single layer of ultra fine silica particles, but it is , of course, also possible to use such a concentration and/or viscosity that several layers of silica dust particles are applied, or to apply less than what would correspond to complete coating of the fibers with the ultra fine silica particles .
  • the sizing may be performed in the normal way, that is , by passing the newly formed glass fiber filament or bundle through a sizing bath and thereafter drying and curing in hot air.
  • the sizing mate ⁇ rial may be any of the conventionally used sizing products suitable for glass fibers that are to be used as reinforcement, for example starch-oil sizes or polymer dispersions, but the sizing is typically performed to an extent which leaves a thicker coating on the fiber surface than normal sizing, typically a coating of a thickness of the order of 1 - 3 ⁇ .
  • the size with which the ultra fine silica may be applied may be any size for coating inorganic reinforcing fibers .
  • suitable sizings are stated on page 207 of "The Manu ⁇ facturing Technology of Continuous Glass Fibers" , K.L.
  • the coating with polymer which optionally contains ultra fine silica may be performed in any suitable manner and at . any suitable stage, including as a primary coating which substitutes the sizing, or as a coating performed after the sizing.
  • the polymer which is used for the coating may be any suitable polymer, and as examples of polymers may be mentioned the following: - Thermosetting plastics such as a phenolic resin, epoxide resin, melanine, polyurethane, polyester, polycarbonate, or polysulphide , or copolymers of these, thermoplastics such as poly vinyl chloride, polyethylene, polypro ⁇ pylene, polymethylmethacrylate, polystyrene, polyamide, or copoly ⁇ mers of these, and elastomers such as rubber (latex, butadiene (BR) , chloroprene
  • BR butadiene
  • CR aery late- butadiene rubbers
  • ABR aery late- butadiene rubbers
  • IIR isobutylene-isoprene rubbers
  • NBR nitrile-butadiene rubbers
  • NCR nitrile-chloroprene rubbers
  • PBR pyridine-butadiene rubbers
  • SBR styrene-buta- diene rubbers
  • SCR styrene-chloroprene rubbers
  • SIR styrene-isoprene rubbers
  • Coatings of inorganic materials such as sulfur or - e.g. when the reinforcing fibers are to be incorporated in an organic polymer matrix and a certain stiffness of the jacketing around the rein- forcing fibers is desirable - waterglass (sodium, .potassium, and lithium silicate) are also within the scope of the invention . Also these coatings may contain ultra fine silica particles in accordance with the principles discussed above.
  • ultra fine silica particles by sizing or coating glass fibers in a manner known per se and thereafter spraying or dusting the ultra fine silica onto the fibers while the size or the coating is still wet, or passing the wet fibers through
  • PI a powder of the ultra fine silica particles , and, preferably, there ⁇ after apply a further layer of coating so that the ultra fine silica is retained in the layer between the last coating and the size or the first coating.
  • the application of a polymer coating in accordance with the above- mentioned principles may be performed in any manner suitable for applying a polymer in fluid state on the fibers .
  • Examples of appli ⁇ cation methods are passage of the fibers through a bath of molten or dissolved polymer, spraying of molten or dissolved polymer on the fibers, rolling of polymer on the fibers, brushing of the poly ⁇ mer on the fibers , etc.
  • silicate fibers in particular glass fibers, to be incor ⁇ porated in alkaline matrices, in particular cement matrices, are additionally protected against corrosion by incorporating, in the contact zone around the fibers , catalyst poisons inhibiting the chemical deterioration of the fibers .
  • Catalyst poisons which may be incorporated in accordance with this aspect of the invention .to improve the chemical environment of glass fibers are, e. g. hydroxi- des or salts of Cu + , Be 2+ , Al 3+ , Zr 4+ , Li + , Mg 2+ , Fe 3+ , Th 4+ ,
  • Catalyst poisons may be introduced into the contact zone around the silicate fibers by incorporation in the matrix material, e. g. , in the form of a solution containing the catalyst poison used, or in the surface coating material, but a more effective incorporation of catalyst poisons may be obtained by a pre-treatment of the glass fibers in a salt solution bath at 150 - 300°C .
  • ultra fine silica particles may be applied on the fibers at the same time, the ultra fine silica particles being incorporated in the salt bath .
  • a surface coating, optionally containing ultra fine silica, on fibers such as glass fibers by performing the sizing or coating on single filaments and/or bundles and/or rovings makes it possible to produce filament bund- les from coated filaments , in other words filament bundles in which the voids between the filaments contain polymer and optionally ultra fine silica particles (which bundles can then, if desired, be subjected to a further application of surface coating optionally containing ultra fine silica particles on the bundle surface) , and to produce rovings in which the voids between the filament bundles comprise polymer and optionally ultra fine silica particles, including rovings in which there is polymer, and optionally ultra fine silica, both in the voids between the bundles and in the voids between the filaments in each single bundle, if desired, with a further coating, optionally containing ultra fine silica, applied on the roving surface.
  • bundles or rovings can be made in which substantially only the surface of the bundle or the roving has a surface coating, or rovings can be made of filament bundles of separately coated filaments , but without coating in the voids be- tween the bundles .
  • Metal oxide acylates is a group of metal organic compounds described, e.g. , in British Patents
  • Metal oxide acylates are interesting for use as sizing or coating materials because they will tend to react chemically with active sites on the glass surface or with water bound to the glass surface. Once chemically bound to glass fibers , metal oxide acylates will result in considerable improve ⁇ ments of the chemical resistance of the glass fibers and also improvements of the resistance of the glass fibers against mechanical damaging.
  • a surface coating comprising a metal oxide acylate may, at the same time, function as an adhesive for ultra fine silica particles according to one of the aspects of the present invention .
  • metal oxide acylates are aluminum oxide acylates, iron oxide acylates, magnesium oxide acylates, etc. , but quite generally, any metal oxide acylate or (mixed metal) oxide acylate or any mixture of metal oxide acylates may be used and will exhibit its inherent properties (which are often to some degree associated with the inherent properties of the metals involved or their oxides and soaps-) when applied on fiber products .
  • reinforcing fibers which can also advantageously be subjected to such treatmen are any other mineral fibers , such as other silicate- containing fibers , e . g. , stone wool or slag wool fibers, Wollastonite fibers, asbestos fibers , high temperature fibers , steel fibers, whiskers, including inorganic non-metallic whiskers such as graphite and - ⁇ 2 ⁇ 3 whisk* 21* - 3 ' reinforcing plastic fibers, such as polypropylene fibers and nylon fibers and aromatic polymer fibers such as PRD and Kevlar fibers , and cellulose fibers .
  • other mineral fibers such as other silicate- containing fibers , e . g. , stone wool or slag wool fibers, Wollastonite fibers, asbestos fibers , high temperature fibers , steel fibers, whiskers, including inorganic non-metallic whiskers such as graphite and - ⁇ 2 ⁇ 3 whisk* 21* - 3
  • ultra fine silica may also be incorporated in the plastic material proper by being incorporated in the starting material from which the fibers (or the films which are fibrillated into fibers) are made .
  • Glass fibers and other fibers are also used for the production of reinforcing mats (non- woven felts) and reinforcing webs prepared, for example, of woven rovings, and it is within the scope of the present invention to apply a coating, optionally comprising ultra fine sihca particles, on such mats or webs .
  • a coating optionally comprising ultra fine sihca particles
  • This can be done by optionally dispersing the ultra fine silica particles in a suitable adhesive or polymer, e.g. of the sizing or coating type discussed above, and applying, e.g. spraying or brushing, the adhesive or polymer dispersion on the mat or web to be treated.
  • the mats or webs may be made from fibers already coated in the manner described above.
  • Fiber coating which secures, when the fibers are incorporated in their respective matrix, fiber sliding with controlled bond strength may be due to sliding between the fibers and the coating, or be ⁇ tween the coating and the matrix, or may be due to internal large deformation in the coating.
  • the coating should be designed so as to obtain a degree of sliding which is suitable for the particular fiber in the particular matrix, in order to obtain a bond strength below the value where the composite material will tend to become brittle due to a too high mechanical locking in the bonding interface, vide the explanation given above.
  • the controlled sliding of the fibers in the matrix will be governed by the rheological ' properties of the coating. The rheological properties of the coating depend on the chemical identity of the coating material.
  • the coating may be made as a homogeneous phase (e . g. a polymer) , or as a composite by introducing fine particles which serve to stiffen the system .
  • the ultra fine silica particles which are orders of magnitude smaller than the fiber diameter constitute an interesting material also from the point of view of their filler capacity in this regard, apart from their other advantages as discussed above.
  • the fibers treated in the manner described above may be incor- porated in a matrix in the same manner as similar untreated fibers are incorporated, and such methods are well-known to the skilled art worker.
  • Some important methods of incorporating fibers in cement- bound matrices are described in "Fibera ⁇ nerede, cement- baserede materialer" by Zoltan F ⁇ rdos , publication no . 08/02/1979 from CtO Cementfabrikkernes tekniske Oplysnings sparkler, R ⁇ rdals- vej 44, 9100 Aalborg, Denmark.
  • Fibers which have been treated in the form of filaments , filament bundles , or rovings to apply a coating of ultra fine silica particles may be chopped in a manner
  • OMPI known per se so a to obtain single fibers, or they may be used for filament winding or other purposes where continuous lengths thereof are required. Also, milled fibers coated in the manner described above may be made, for use for their special purposes . It will be understood that also fiber combinations such as are often used in practice, e. g. , combinations of inorganic fibers with cellu ⁇ lose fibers and/or wollastonite, may also be coated in accordance with the principles discussed above.
  • the matrices reinforced with the specially treated fibers may be cement-based matrices such as matrices based on Portland cement, (including Rapid cement) , and these matrices may be cement paste, mortar, concrete, and special matrices such as low porosity cement and a particular matrix which is described in greater detail below and which contains , in itself, a homogeneous dispersion of ultra fine silica.
  • Other types of cement which may be used alone or in combination with other cements in the matrix are aluminate cement, sulphate-resistant cement, white cement, sand/chalk cement, and mixed cements (puzzolan, slag cement) etc.
  • matrices in which the fibers of the present invention may be used are matrices in which both inorganic and organic binders are used.
  • organic matrices are the well-known plastics which are normally reinforced with, e.g. , silicate-containing fibers such as glass fibers .
  • the applied coating comprising .ultra fine silica particles on the reinforcing fibers will be of advantage, for example with respect to protection of the fibers against microcracking, both during the incorporation in the matrix and during the earlier manipulation of the fibers , and the micro"roughness" conferred by the ultra fine silica particle will tend to increase the anchoring of the fibers in plastic matrices .
  • plastic fibers which are to be incorporated in inorganic matrices are improved with respect to their dispersibi ⁇ ty and their anchoring in the final inorganic matrix by incorporation of ultra fine silica, the ultra fine silica coating being applied in any of the manners described above, or ultra fine silica being incorporated in the plastic material proper.
  • polyolefin fibers which may be prepared by stretching a polyolefin film, preferably a polypropylene film, in a ratio of at least 1 : 15 to obtain a film thickness of 10 - 60 m and fibrillating the stretched material, or, as expressed through their properties , polyolefin fibers , especially polyethylene fibers , having a tensile strength of at least 4000 kp/cm , a modulus of elasticity of at least
  • Fibers of this type are described in German Patent Application No. P 28 19 794.6 and US Patent Application Serial No . 902,920 of
  • ultra fine silica in an inorganic binder matrix such as a cement matrix in adequate amounts, for example in an amount corresponding to at least 1 - 5 per cent by volume, calculated on the inorganic binder, preferably an amount of ultra fine silica of the order of at least 10 per cent by volume, calculated on the inorganic binder, and using measures to obtain a homogeneous dispersion of the ultra fine silica particles, a unique matrix comprising densely packed inorganic binder particles and homogeneously dispersed ultra fine silica particles or a coherent structure comprising such particles is obtained.
  • This particular type of matrix is described in International Patent Apphcation No . PCT/DK/00047 and in Danish Patent Apphcation No . 1945/80 and may be defined, in its broadest sense, as a matrix comprising
  • the dense packing substantially being a packing corre- sponding to the one obtainable by gentle mechanical influence on a system of geometrically equally shaped large particles in which locking surface forces do not have any significant effect
  • Shaped articles comprising such matrices may be prepared by com ⁇ bining the particles A (which, as mentioned above, are suitably ultra fine silica particles) and particles B (which, as mentioned above, are suitably cement particles), a liquid, and a surface- active dispersing agent, the amount of particles B substantially corresponding to dense packing thereof in the resulting composite material with homogeneously packed particles A in the voids betwee the particles B , the amount of Kquid substantially corresponding to the amount necessary to fill the voids between the particles A and the particles B , and the amount of surface active dispersing agent being sufficient to fully disperse the particles in a low stress field of less than 5 kg/cm 2 , preferably less than 100 g/cm 2 , and mecha ⁇ nically mixing the ingredients , optionally together with additional bodies C, until a viscous to plastic mass has been obtained, and thereafter, if desired, combining the resulting mass with additional bodies C by mechanical means to obtain the desired distribution of such additional bodies , and finally
  • the additional bodies C incorporated either during the preparation of the mass or by mechanical means after the viscous to plastic mass has been obtained, or both, are typically compact bodies such as sand and stone or reinforcing fibers of any of the above types , and the additional bodies which are optionally incorporated during the casting may typically be fibers , or fiber webs, nets or bands or bundles, or they may be reinforcing steel bars or rods.
  • the reinforcing fibers or bars or rods incorporated during the casting may be pre-stressed.
  • additional compact- shaped bodies are incorpo- rated which are stronger than ordinary sand and stone used in ordinary mortar or concrete, e . g. bodies of refractory grade bauxite .
  • the dispersing agent used in the preparation of this particular type of matrix is adapted to the particular combination of particles A and B .
  • the dispersing agent is typically a so-called concrete superplasticizer, one superplasticizer which, has been found useful being an alkaH or alkaline earth metal salt of a highly condensed naphthalene sul- phonic acid/formaldehyde condensate, of which typically more than 70 per cent consist of molecules containing 7 or more naphthalene nuclei, the alkali or alkaline earth metal salt preferably being a sodium or calcium salt.
  • One concrete superplasticizer product of this type is commercially available under the trade mark "Mighty" .
  • Such superplasticizer is , according to the principles of the present invention , typically used in the range of 2 - 4 per cent, calculated on the total weight of the inorganic binder, typically Portland cement, and the ultra fine silica.
  • Other concrete superplasticizers are also useful, such as appears from Example 8 below.
  • a suitable dispersing agent is sodium tripolyphosphate , such as appears from Example 5 below.
  • the binder matrices obtainable according to this aspect of the invention may, depending on the relative amount of ultra fine silica used, show either a homogeneous distribution of ultra fine silica particles present in a concentration which is less than corresponding to dense packing thereof, or a homogeneous distribution of the ultra fine silica particles in dense packing.
  • the strength and density are generally increased.
  • the mechanical fixation of the incorporated reinforcing fibers is increased by one or several orders of magnitude, as the claims to dimensions of roughness and wave configuration of the fibers to obtain " echani- chal locking" are moved 1 - 2 orders of magnitude down, which means that mechanical locking is obtained with fibers which are one to two orders of magnitude finer than hitherto, including glass fibers and other fine inorganic fibers .
  • the materials may be shape from a mass with plastic to viscous consistency by simple shear deformation without any exchange of material with the surroundings This makes it possible to prepare high quality products of much more complicated shape and larger size than hitherto, and makes it possible to obtain anchoring of components - and of special interest fibers of any of the abovementioned types - which could not satis ⁇ factorily (or which could not at all) be introduced in corresponding high quality matrices prepared in the traditional manner. Due to the possibility of shaping the articles in question in a "gentle" way in a low stress field, incorporated fibers (which may be of any of the types discussed above) may, in contrast to what happens in any known art processes which might approach dense packing in ultra fine particle systems , substantially retain their geometric identity during the shaping.
  • the mixture obtained when using the abovementioned process for producing superplasticized cementbased pastes will, due to the low water content, typically a water content corresponding to a weight ratio between water and cement, e.g. , Portland cement, of 0.12 to 0.30, preferably 0.12 to 0.20, have a very "dry" appearance du ⁇ ring the mixing stage until it converts into the viscous-plastic state .
  • the incorporation of reinforcement fibers into such a mass may , depending upon the nature of the reinforcing fibers , be performed in the initial mixing stage, or when the viscous to pla ⁇ stic consistency has been obtained.
  • the working examples illustrate the preparation of the above-men- tioned special type of superplasticized inorganic binder matrix containing ultra fine sihca.
  • Examples 1 - 9 illustrate various pro ⁇ perties of such a matrix with either densely packed or not densely packed, but still homogeneously distributed, ultra fine sihca. par ⁇ ticles
  • examples 10 - 14 illustrate fiber-reinforced composite materials incorporating such matrices .
  • the special matrices comprising homogeneously dispersed and preferably densely packed ultra fine sihca particles i RE-
  • OMPI are excellently suited for fixation of reinforcement bodies, and, in particular, for fixation of ultra fine fibers and whiskers .
  • these special, very strong and dense cement-silica materials call for high quality rein- forcement, such as especially ultra fine high strength fibers and whiskers, to create tough, strong cement materials of a hitherto unattainable high quality.
  • due to the strongly improved fiber bond in these special matrices a pronounced tendency to brittleness is experienced due to the above-mentioned lack of sli- ding between the fiber and the matrix adjacent to crack openings .
  • an important aspect of the present invention is to overcome these problems by reinforcing the special strong, dense silica-ce ⁇ ment materials with high strength fibers, threads, rods, and whis ⁇ kers carrying a coating which results in that the said reinforcing elements are capable of shding in the matrix with controlled bond strength .
  • the above-men ⁇ tioned principles comprising coating of fibers and other reinforcing bodies used in ordinary cement products (concrete, mortar, fiber- cement materials , etc. ) are utilized and further developed to pro ⁇ quiz high quality, effectively reinforced cement- sihca materials .
  • fiber coating ensuring shding with controlled bond strength may be obtained in that shding takes place between the fiber and the coating, between the coating and the matrix, or due to internal large deformation in the coating.
  • the shding established is either controlled interface shding or controlled film deformation .
  • this aspect of the invention comprises a composite material, or a shaped article, comprising a special matrix as defined above, reinforcing bodies embedded in the matrix, and a contact domain surrounding the reinforcement bodies and com- prising a material which is different in composition from as well the matrix as the reinforcement body .
  • reinforcing bodies are suitably fibers of the types discussed above, in particuler high strength fine fibers or whiskers of glass , Al 2 O , or carbon, etc.
  • the contact domain is suitably a coating comprising a polymer or sizing material of any of the types discus ⁇ sed above, or a waxy polymer material such as paraffin wax, etc .
  • the preparation of the coated reinforcing bodies for this purpose is performed in any suitable way, e.g. , in any of the ways dis- cussed above.
  • the shding to obtain controlled bond strength is obtained by suitable adaption of the rheological properties of the coating, to obtain fiber-coating shding, or coating-matrix shding, or film deformation, such as discussed above .
  • the rheological pro ⁇ perties of the coating can be adjusted by the incorporation of ultra fine sihca in the coating, such as discussed above, and when the reinforcing bodies are fiber bundles or rovings, the coating may be applied on each of the single filaments, or the bundle or roving may have a common exterior coating of a sufficient thickness and strength to avoid intrusion of any matrix material so that controlled shding between the single filaments in the bundle or roving is se ⁇ cured by avoiding any crystal growth in the interspace between the single filaments .
  • - ⁇ U REA fibers will normally be preferred as the fiber reinforcement.
  • coarser units such as glass fiber bundles or rovings, or a combination thereof, as the main reinforcement, possibly combined with finer units such as single filaments as "anti-crack" reinforcement.
  • coarser units such as glass fiber bundles or rovings, or a combination thereof
  • finer units such as single filaments as "anti-crack” reinforcement.
  • Combinations of this type are glass fiber bundles or rovings as main reinforcement and glass filaments, and/or cellulose fibers, and/or mineral wool fibers, as the "anticrack" reinforcement.
  • the length of the fibers may typically be 2 - 4 cm, but in principle, and depending upon the character of the fiber reinforcement, much longer units, or webs or bands thereof, may be used.
  • Fig. 1 shows a scanning electron microscopy (SEM) photo (magnifi ⁇ cation 3000 x) of a fracture surface of an autoclaved sample of ordinary cement matrix with an embedded E glass fiber filament. It will be noted that the fiber surface is completely rough and dete ⁇ riorated, which is due to attack on the glass .
  • SEM scanning electron microscopy
  • Fig. 2 shows an SEM photo, magnification 3000 x, of a fracture surface of an autoclaved sample of superplasticized cement-silica matrix with a content of ultra fine sihca particles of 25% by weight, with embedded uncoated E glass filaments . It will be noted that the fiber has been protected in the special matrix so that there is hardly any chemical or physical deterioration of the fiber filaments visible .
  • Fig. 3 shows an SEM photo, magnification 3000 x, of uncoated E glass filaments in a fiber bundle incorporated in the same matrix
  • Fig. 4 is a drawing made on the basis of an SEM photo of a 30 ⁇ thick polypropylene fiber at a rupture surface of a polypropylene fiber-reinforced ultra fine silica/cement specimen prepared as de- scribed in Example 10.
  • the fiber is intimately embedded in the very dense matrix and is fixed in the matrix with a bond strength which is higher than the bond strength obtainable in any ordinary cement matrix, but the fiber is capable of shding in the matrix, and the bond strength is controlled to a level below the critical maximum at which the composite material becomes brittle.
  • Fig. 5 is a graph showing bending strength ⁇ character, referring to maximum load, for specimens of the special ultra fine silica/cement matrix (with substantially dense packing of the sihca) with fiber reinforcement, partly at an early stage (e) , and partly after sto ⁇ rage (s) , as a function of the fiber content in % by weight.
  • the exact experimental conditions relating to the materials in question and the values plotted in Fig. 5 appear from Examples 11, 12, 13, and 14.
  • "EF” designates E glass fibers (uncoated)
  • ARF designates alkali- resistant glass fibers (uncoated)
  • PPF designates polypropylene fibers of the type illustrated in Fig. 4.
  • the abscissa unit for the lighter polypropylene fibers in Fig. 5 is different from the units for the glass fibers so that the same distance from origon corresponds to substantially the same fiber volume of the respective fibers .
  • the same distance from origon corresponds to substantially the same fiber volume of the respective fibers .
  • E glass fiber-reinforced samples showed very high early strength even at relatively low contents of fiber reinforcement. However, during storage, the strength decreases to substantially constant values which, although high compared with ordinary fiber- reinfor- ced matrices , are considerably lower than the early strength values .
  • Portland cement Specific surface (Blaine) about 3300 cm /g (Portland basis 5.78) . Density 3.12 g/cm
  • Aluminous cement SECAR 71 Specific surface (Blaine) 3630 cm /g
  • Ultra fine sihca Ultra fine spherical SiO 2 -rich particles .
  • Fine fly ash from power plants (0007): Fine spherical particles , part of which are hollow. Specific surface (Blaine) 5255 cm /g. Density approximately 2.4 g/cm 2
  • MICRODAN 5 Fine chalk (average diameter about 2 ⁇ , density 2.72 g/cm ) .
  • Quartz sand, finely ground Specific surface (Blaine) 5016 cm /g
  • Bauxite Refractory grade calcined bauxite
  • a so-called concrete superplasticizer sodium salt of a highly condensed naphthalene sulphonic acid/formaldehyde condensate, of which typically more than 70% consist of molecules containing 7 or more naphthalene nuclei. Density about
  • Polypropylene fibers Fibers prepared as described in Example 15.
  • E glass fibers Bundles of E glass fibers, filament diameter about 10 ⁇ , length 12 mm,
  • Alkah-resistant fibers Bundles of "CEMFIL” (trademark of Fiberglass Ltd. ) , filament diameter about 10 ⁇ , length 12 mm.
  • the binder To obtain a dense packing of the binder, about 32 per cent by volume of the fine powder (ultra fine sihca) and about 68 per cent by volume of the coarse powder (Portland cement) was used. In order to avoid dilution of the binder, relatively coarse sand without fines under 1/4 mm was used. In the coarse materials gap grading was utilized (the composition does not contain any material between 4 and 8 mm) , and the sand/course aggregate ratio was adapted in order to obtain a dense structure with minimum binder volume. In consideration of the dense packing, the amount of binder (Portland cement plus ultra fine sihca) was reasonably low (533 kg/ ) . The dosage of "Mighty" permitted the obtain ent of a very soft, easily cast concrete with low water content (water /powder ratio 0.19 per weight) . (Later experiments have indicated that the amount of water may be kept considerably lower for concrete to be cast with
  • Coarse aggregate, sand, cement and ultra fine sihca were dry-mixed in a 50 hter paddle mixer for 5 minutes . Thereafter, part of the water (about 2000 grams of the total 3500 grams) was admixed, and mixing was continued for 5 minutes . Concomitantly with this , a solution of 472.5 grams of "Mighty" powder in 1000 grams of water was prepared by shaking for 5 minutes on a shaker mixer. The "Mighty" solution and the remaining about 500 grams of water were added to the mixture (the last water was used for washing the container containing the "Mighty” solution to ensure that the entire amount of "Mighty” was utilized) .
  • Fresh concrete The concrete was soft and easily workable .
  • the consistency of the concrete was determined by measuring the spreading cone (DIN 1048 Ausbreit-Mass , 20 cm cone, diameter 13 - 20 cm) .
  • the spreading measure was 27 - 30 cm .
  • the content of air was measured (1.5%) .
  • Casting 16 concrete cylinders having the dimension stated above were cast from each batch .
  • the specimens were vibrated for 10 - 20 seconds on a vibrating table (50 Hz) .
  • the heat-cured specimens were removed from the water bath after 20 hours and cooled for about 1 hour in water at 20 C, whereafter they were demolded, and their density was determined by weighing in air and submersed in water, respectively. Part of the specimens were thereafter subjected to strength testing etc.
  • a single specimen was autoclaved for about 96 hours under the conditions stated above, whereafter it was cooled and demolded and weighed in air and submersed in water for determination of density whereafter it was subjected to mechanical testing.
  • Density, sound velocity, dynamic modulus of elasticity, compressive strength and stress/strain curve were determined.
  • the compressive strength was determined on a 500 tons hydrauhc press .
  • the sound velocity was about 5.2 km/sec .
  • the dynamic modulus of elasticity was about 68,000 MPa.
  • Quartz sand 1 - 4 mm 2763 g
  • the mixing was performed in a kneading machine with planetary movement, using a mixing blade.
  • the following procedure was foUowed : 1) Dry mixing of sand, cement + filler for 5 minutes .
  • the mortar mixtures in Series 1, 2, and 3 behaved like a highly viscous fluid and were cast in cylindrical molds on a standard vibrating table (50 Hz) . The casting time was about 1 minute. The specimens (in closed molds) were cured in water at 20°C. The mortar mixtures in Series 4 (double size) were considerably softer.
  • pw The density of water.
  • pc The density of cement.
  • the volume ratio j varies from 0.44 with the extremely fine sihca particles via 0.74 for the material with a filler which is only a httle finer than cement, to 0.84 for the reference mortar in which the fiher is cement. This is in complete conformity with experience from packing of large particle systems . The same is expressed in another form in the two last rows . It is interesting to note that the so-called water/cement ratio (weight ratio between water and cement) would be as low as 0.12 for the sihca cement system if sihca had the same density as cement, versus 0.20 for a pure cement, in spite of the fact that this volume (0.20) is extremely low and only obtainable with a high dosage of superplasticizer.
  • the amount of Mighty in the above materials is high such as ap ⁇ pears from the below ratios :
  • the ratio sihca to Portland cement + sihca was varied between 0, 10, 20, 30, 40, and 50 per cent by volume.
  • the amount of water was adapted so that the fresh concrete obtained had substantially the same consistency (as measured by spreading cone) as in Example 1.
  • the mixing and casting procedures were as in Example 1.
  • the volume of fine powder (cement + ultra fine sihca) was the
  • the water demands that is, the amount of water used in the var ⁇ ious mixes in order to obtain the specified consistency, were ascer ⁇ tained by trial mixing.
  • the water demands appear from the table.
  • the right hand column states the volume of water in relation to the volume of cement + ultra fine sihca.
  • the mixing was performed in a kneading machine with planetary movement using a mixing blade .
  • the foUowing procedure was fol ⁇ lowed for batches with Mighty:
  • the consistency was considered to be of the desired value for dia ⁇ meters of about 14 cm after 10 strokes and of 16 cm after 20 stro ⁇ kes .
  • the water demand was determined by inter- polation from tests with too much water (too large a diameter) and too httle water (too small a diameter) .
  • Sodium tripolyphosphate has a beneficial influence on mixes of aluminous cement and ultra fine sihca, but is without any effect
  • the foUowing components were different:
  • the volume of the fine powder was kept constant at about 1160
  • the mixing was performed as described in Example 5.
  • the consis ⁇ tency was soft.
  • the experiments demonstrate a very high strength of the binder matrix.
  • the fracture went through the quartz particles which means that the strength level can be considerably increased by using a stronger . sand material, such as illustrated in Example 7.
  • the results demonstrate the possibility of replacing part of the Portland cement with a different powder of a fineness like that of cement or somewhat finer (fly ash and finely ground sand) .
  • FinaUy the results demonstrate the possibility of utilizing an altered cement grain size distribution, in this case demonstrated by replacing 1/3 of the ordinary white Portland cement with a finely ground white Portland cement.
  • Coarse aggregate, cement and Mighty powder were dry -mixed in a 50 hter paddle mixer for 5 minutes . Thereafter, the ultra fine sihca was admixed, and mixing was continued for 10 minutes . The water was added, and the mixing was continued for approx. 10 minutes .
  • the concrete was soft and easily workable.
  • the closed molds for the cylinders were submersed in water at 60°C and cured for 5 days .
  • the slabs were covered with plastic film and cured one day at 20 C in air after which they were submersed in water at 60 C and cured for 4 days .
  • the specimens were demolded and stored in air at 20°C and approx. 70% relative humidity until testing (testing was performed within a period of 30 days subsequent to the heat treatment) .
  • Density, sound velocity, dynamic modulus of elasticity, compressive strength and stress/strain curve were determined for the 6 concret cylinders (stress/strain curves were determined for two specimens only) .
  • Lomar-D A concrete superplasticizer of the same composition as Mighty, produced by Diamond Shamrock Chemical Company, N. Jersey, USA .
  • Betokem A sulphonic acid formaldehyde condensate based on naphthalene and hgnosulphonate
  • the superplasticizer-amounts were determined so that the content of dry matter was at least 82 g per mixture. A somewhat greater dosage was used with Betokem and Sikament.
  • the foUowing components were different:
  • the mixing was performed in a kneading machine with planetary movement, using a mixing blade.
  • the foUowing procedure was foUowed:
  • the water demands that is, the amount of water used in the various mixes in order to obtain the specified consistency, were ascertained by trial mixing.
  • the water demands appear from Table VI below.
  • the consistency was evaluated by measuring the spreading of a co of the material formed by pouring the material into a 5 cm high br cone mould with bottom diameter 10 cm and upper diameter 7.1 cm on a flow table with brass surface for use in testing hydrauhc cem (ASTM C 230-368) and removing the mold.
  • the diameter of the mat was evaluated by measuring the spreading of a co of the material formed by pouring the material into a 5 cm high br cone mould with bottom diameter 10 cm and upper diameter 7.1 cm on a flow table with brass surface for use in testing hydrauhc cem (ASTM C 230-368) and removing the mold. The diameter of the mat
  • OM rial was measured a) immediately subsequent to removal of the mold, b) after 10 strokes, and c) after 20 strokes .
  • the consistency was considered to be of the desired value for dia- meters of about 12 cm after 10 strokes and of 14 cm after 20 strokes .
  • Water demand (including water in the superplasticizer solution) ex ⁇ pressed in grams of water per batch and in relation to the total amount of fine powder (cement + ultra fine sihca) on a weight basis , the volume of fine powder being the same in all of the mixes
  • the experiments can be compared with the experiments in Example 5, series 1, table IV .
  • Sand, cement, and sihca amounts are the same as in that example, the ultra fine sihca and the cement, however, originating from later batches .
  • Another difference is that in Exampl 5, Mighty powder was used and was dissolved immediately prior to mixing, whereas in the present experiment a Mighty solution delivered from the manufacturer was used. It wiU be noted that the water demand in aU cases with high dosage of superplasticizer was low, ranging from 500 g in Example 5 to 600 - 650 g for Melment in the present experiment, corresponding to water/powder ratios of 0.15 - 0.19 by weight.
  • the foUowing components are used:
  • the amounts of sand, cement and Mighty used are the same as the amounts used in Example 6.
  • the water amount was also the same as in Example 6, whereas the water amount in the mortar with sihcon carbide was considerably higher. This was due to the fact that the sihcon carbide sand had very sharp edges and therefore required a more easUy flowable silica/cement paste and/or a larger amount (by volume) of paste.
  • the mixing was performed in a kneading machine with planetary movement, using a mixing blade.
  • the foUowing procedure was foUowed:
  • Fiber-reinforced specimens were prepared with the foUowing com ⁇ position :
  • the cement plus the ultra fine sihca were dry mixed for 5 minutes with a mixing blade .
  • the fibers were added to the dough whUe mixing with the mixing hook, and thereafter, the mixing was continued for 5 minutes .
  • the material was covered with plastic film.
  • the extruded strings which had a length of 1 - 2 meters, were cut in lengths of about 20 cm and stored in a moist box at 20°C for about 24 hours . Thereafter, they were subjected to various types of storing:
  • ⁇ - designates the formal maximum tensUe stress in bending at which the matrix cracks (break in the stress/ strain curve)
  • a.- designates the formal maximum tensUe stress at maximum load.
  • E is the modulus of elasticity before crack of the matrix
  • ⁇ - designates the tensUe strength.
  • RReellaattiive humidity % 100 100 aut. 100 100 aut. water aut.
  • Fig. 6 shows a diagram of bending stress versus deflection of one of the specimens from Experiment 3 cured at 20 C for 7 days . Thickness 10.6 mm. As ordinate is shown the formal bending stress and as abscissa deflection. Until fracture of the matrix, the plate was very stiff. Hereafter, the load was largely carried by the fibers , and the specimen was able to carry an excess load of 57% while it was deflected 1 mm measured over a length of about 60 mm .
  • Fig. 7 is a stress/strain diagram for the specimen made according to Experiment 1, cured at 80 C for 1 day, and the specimen made according to Experiment 2, cured at 80 C for 1 day, respectively, in tension .
  • the material was very stiff untU cracks occurred in the matrix.
  • the load was carried by. the fibers .
  • the testing was performed by differential calorimetry, the specime being cooled down to -50°C. Only very httle freezable water was determined, viz. 5 mg per gram of specimen freezing at between -40 and -45 C. A material showing such properties must be desig- 10 . nated as absolutely resistent to frost attack.
  • Fiber- reinforced specimens were prepared with the foUowing composition : -20
  • Tests specimens were prepared by extrusion in the same manner as described in Example 10. Thereafter, the specimens were stored at 100% relative humidity at 20°C .
  • Extruded test specimens were prepared and tested in the same manner as described in Example 11, but with 12 mm polypropylene fibers .
  • the compositions were as foUows :
  • the values plotted in Fig. 5 to show the development of the strength properties of the polypropylene-reinforced special matrix during storage were the 7 and 28 days' values for the 1% reinfor- cement with 12 mm fibers from Table X, the 7 and 28 days' values for the 2% reinforcement with 6 mm fibers from Table IX, and the 28 and 90 days' values for the 3% reinforcement with 6 mm fibers from Table IX.
  • ⁇ E values plotted in Fig. 5 are the values from Experiments Nos . 4, 5, and 6.
  • Example 13 The procedure described in Example 13 was repeated, this time with alkah-resistant glass fibers .
  • the composition was as foUows : Experiment No.
  • the polypropylene used was GWE 23 from ICI with melt index of 3 g/10 minutes measured according to DIN MFI 230/2.16.
  • the polypropylene was ex ⁇ truded into a blown tubular film at an extruder temperature of 180 - 220 C, and the tubular film was cooled with cooling air at 18 - 20 C and cut into two film bands .
  • the film was pas ⁇ sed through a hot air oven with an air temperature of 180°C and an air velocity of 25 m/second.
  • the film was stretch - ed in a ratio of 1: 17.
  • the film was heat- stabilized by passing a hot air oven with an air temperature of 180°C and an air velocity of 25 m/sec , the film velocity being about 90 m/sec.
  • the thickness of the film was then 20 ⁇ .
  • the film was fibriUated to form fibers of from 2 to 30 dtex by means of a Reifenhauser FI-S-0800-03-01 fibriUator with 13 needles per cm in each of two consecutive staggered needle rows placed with the same distance as the interval between two needles .
  • Example 10 The fibers used in Examples 11 and 12 were pre ⁇ pared in the same manner, but with an additionel corona treatment as described in GB Patent Apphcation No . 2,026,379.

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Abstract

Dans des materiaux composites comprenant une matrice organique et/ou inorganique, p. ex. une matrice de ciment, des corps de renforcement tels que des fibres sont entoures par un domaine de contact consistant en un materiau dont la composition est differente de celle de la matrice et de celle de la fibre. Le domaine de contact comprend un materiau tel qu'un polymere qui donne une capacite de glissement a la fibre dans la matrice de maniere a obtenir une resistance de liaison controlee entre le corps de renforcement et la matrice, et/ou le domaine de contact comprend des particules de silice ultrafine. Les particules de silice ultrafine assurent une protection chimique des fibres de verre. La matrice est, particulierement, une matrice de ciment/silice ultrafine ou les particules de ciment sont entassees de maniere dense et la silice ultrafine est disposee de maniere homogene et est de preference entassee sensiblement de maniere dense dans les vides entre les particules de ciment. Une telle matrice est preparee a partir d'une boue de tres faible teneur en eau au moyen d'un superplastifiant de beton. La protection des fibres de silicate contre la deterioration est obtenue en incorporant un poison de catalyseur.
EP80901403A 1979-07-13 1981-02-09 Materiau composite renforce avec des fibres et articles formes Withdrawn EP0031838A1 (fr)

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GR68707B (fr) * 1978-10-25 1982-02-02 Owens Corning Fiberglass Corp
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