Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
  • B29C70/00—Shaping composites, i.e. plastics material comprising reinforcements, fillers or preformed parts, e.g. inserts
  • B29C70/04—Shaping composites, i.e. plastics material comprising reinforcements, fillers or preformed parts, e.g. inserts comprising reinforcements only, e.g. self-reinforcing plastics
  • B29C70/06—Fibrous reinforcements only
  • B29C70/10—Fibrous reinforcements only characterised by the structure of fibrous reinforcements, e.g. hollow fibres
  • B29C70/16—Fibrous reinforcements only characterised by the structure of fibrous reinforcements, e.g. hollow fibres using fibres of substantial or continuous length
  • B29C70/22—Fibrous reinforcements only characterised by the structure of fibrous reinforcements, e.g. hollow fibres using fibres of substantial or continuous length oriented in at least two directions forming a two-dimensional [2D] structure
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
  • B29C70/00—Shaping composites, i.e. plastics material comprising reinforcements, fillers or preformed parts, e.g. inserts
  • B29C70/04—Shaping composites, i.e. plastics material comprising reinforcements, fillers or preformed parts, e.g. inserts comprising reinforcements only, e.g. self-reinforcing plastics
  • B29C70/28—Shaping operations therefor
  • B29C70/40—Shaping or impregnating by compression not applied
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
  • B29C70/00—Shaping composites, i.e. plastics material comprising reinforcements, fillers or preformed parts, e.g. inserts
  • B29C70/04—Shaping composites, i.e. plastics material comprising reinforcements, fillers or preformed parts, e.g. inserts comprising reinforcements only, e.g. self-reinforcing plastics
  • B29C70/28—Shaping operations therefor
  • B29C70/40—Shaping or impregnating by compression not applied
  • B29C70/42—Shaping or impregnating by compression not applied for producing articles of definite length, i.e. discrete articles
  • B29C70/46—Shaping or impregnating by compression not applied for producing articles of definite length, i.e. discrete articles using matched moulds, e.g. for deforming sheet moulding compounds [SMC] or prepregs
  • B29C70/465—Shaping or impregnating by compression not applied for producing articles of definite length, i.e. discrete articles using matched moulds, e.g. for deforming sheet moulding compounds [SMC] or prepregs and impregnating by melting a solid material, e.g. sheets, powders of fibres
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
  • B29C70/00—Shaping composites, i.e. plastics material comprising reinforcements, fillers or preformed parts, e.g. inserts
  • B29C70/04—Shaping composites, i.e. plastics material comprising reinforcements, fillers or preformed parts, e.g. inserts comprising reinforcements only, e.g. self-reinforcing plastics
  • B29C70/28—Shaping operations therefor
  • B29C70/40—Shaping or impregnating by compression not applied
  • B29C70/42—Shaping or impregnating by compression not applied for producing articles of definite length, i.e. discrete articles
  • B29C70/46—Shaping or impregnating by compression not applied for producing articles of definite length, i.e. discrete articles using matched moulds, e.g. for deforming sheet moulding compounds [SMC] or prepregs
  • B29C70/48—Shaping or impregnating by compression not applied for producing articles of definite length, i.e. discrete articles using matched moulds, e.g. for deforming sheet moulding compounds [SMC] or prepregs and impregnating the reinforcements in the closed mould, e.g. resin transfer moulding [RTM], e.g. by vacuum
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
  • B29C70/00—Shaping composites, i.e. plastics material comprising reinforcements, fillers or preformed parts, e.g. inserts
  • B29C70/04—Shaping composites, i.e. plastics material comprising reinforcements, fillers or preformed parts, e.g. inserts comprising reinforcements only, e.g. self-reinforcing plastics
  • B29C70/28—Shaping operations therefor
  • B29C70/40—Shaping or impregnating by compression not applied
  • B29C70/50—Shaping or impregnating by compression not applied for producing articles of indefinite length, e.g. prepregs, sheet moulding compounds [SMC] or cross moulding compounds [XMC]
  • B29C70/52—Pultrusion, i.e. forming and compressing by continuously pulling through a die
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
  • C08J5/00—Manufacture of articles or shaped materials containing macromolecular substances
  • C08J5/04—Reinforcing macromolecular compounds with loose or coherent fibrous material
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
  • C08L77/00—Compositions of polyamides obtained by reactions forming a carboxylic amide link in the main chain; Compositions of derivatives of such polymers
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29K—INDEXING SCHEME ASSOCIATED WITH SUBCLASSES B29B, B29C OR B29D, RELATING TO MOULDING MATERIALS OR TO MATERIALS FOR MOULDS, REINFORCEMENTS, FILLERS OR PREFORMED PARTS, e.g. INSERTS
  • B29K2077/00—Use of PA, i.e. polyamides, e.g. polyesteramides or derivatives thereof, as moulding material
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29K—INDEXING SCHEME ASSOCIATED WITH SUBCLASSES B29B, B29C OR B29D, RELATING TO MOULDING MATERIALS OR TO MATERIALS FOR MOULDS, REINFORCEMENTS, FILLERS OR PREFORMED PARTS, e.g. INSERTS
  • B29K2277/00—Use of PA, i.e. polyamides, e.g. polyesteramides or derivatives thereof, as reinforcement
  • B29K2277/10—Aromatic polyamides [Polyaramides] or derivatives thereof
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29K—INDEXING SCHEME ASSOCIATED WITH SUBCLASSES B29B, B29C OR B29D, RELATING TO MOULDING MATERIALS OR TO MATERIALS FOR MOULDS, REINFORCEMENTS, FILLERS OR PREFORMED PARTS, e.g. INSERTS
  • B29K2711/00—Use of natural products or their composites, not provided for in groups B29K2601/00 - B29K2709/00, for preformed parts, e.g. for inserts
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
  • C08J2377/00—Characterised by the use of polyamides obtained by reactions forming a carboxylic amide link in the main chain; Derivatives of such polymers
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
  • C08K7/00—Use of ingredients characterised by shape
  • C08K7/02—Fibres or whiskers
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
  • C08L61/00—Compositions of condensation polymers of aldehydes or ketones; Compositions of derivatives of such polymers
  • C08L61/04—Condensation polymers of aldehydes or ketones with phenols only
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
  • C08L61/00—Compositions of condensation polymers of aldehydes or ketones; Compositions of derivatives of such polymers
  • C08L61/04—Condensation polymers of aldehydes or ketones with phenols only
  • C08L61/06—Condensation polymers of aldehydes or ketones with phenols only of aldehydes with phenols
• • 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
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
  • Y10T442/00—Fabric [woven, knitted, or nonwoven textile or cloth, etc.]
  • Y10T442/20—Coated or impregnated woven, knit, or nonwoven fabric which is not [a] associated with another preformed layer or fiber layer or, [b] with respect to woven and knit, characterized, respectively, by a particular or differential weave or knit, wherein the coating or impregnation is neither a foamed material nor a free metal or alloy layer

Definitions

• the present invention relates to the use of high-fluidity polyamide for the impregnation of reinforcement materials in the form of fabric of industrial fabrics for the manufacture of composite materials.
• the field of the invention is that of composite materials and their manufacturing processes.
• thermosetting resins In the field of high-performance materials, composites have taken a prominent place, due to their performance and the weight gains they allow.
• the best known high-performance composites to date are obtained from thermosetting resins, the use of which is limited to low to medium series applications, mainly in aeronautics, motor sports, and in the best cases, presenting manufacturing times of about fifteen minutes, for example, during the manufacture of skis.
• the cost of these materials, and / or the manufacturing time make them difficult to compatible with mass use.
• the use of thermosetting resins often involves the presence of solvents and monomers. Finally, these composites are difficult to recycle.
• thermoplastic matrix composites An answer, compared to the manufacturing times, is given by thermoplastic matrix composites.
• Thermoplastic polymers are generally known for their high viscosity, which constitutes a brake with regard to the impregnation of reinforcement materials, generally composed of very dense multifilament beams. It results from the use of thermoplastic matrices available on the market, a difficulty of impregnation requiring either prolonged impregnation times or significant application pressures. In most cases, the composite materials obtained from these matrices may have microvoids and non-impregnated areas. These microvids cause mechanical properties drop, premature aging of the material and delamination problems when the material consists of several layers of reinforcements. This phenomenon of loss of mechanical properties is also accentuated when the cycle times for the manufacture of composite articles decrease.
• Another problem frequently encountered with polymer matrix composite materials is their resistance to aging, and more particularly to hygrothermal aging.
• the diffusion of water within the composite materials causes a significant change in certain physical characteristics such as, for example, the glass transition temperature or swelling of the matrix.
• a modification at the matrix / fiber interfaces can also be observed, generally with an irreversible character.
• This aging is manifested by a degradation of the mechanical performances, in particular the resistance to breakage. It is then necessary to oversize the parts, which leads to an increase in weight and significant additional cost.
• the objective of the present invention is therefore to remedy these drawbacks by proposing a composite article that can be manufactured with short cycle times while having good use properties, such as good mechanical properties and good resistance to wear. hygrothermal aging.
• the Applicant has unexpectedly discovered that the use of novolac resin in polyamides of high fluidity for the manufacture of composite articles made it possible to obtain articles having not only good mechanical properties, such as, in particular, rigidity, resistance at break, impact resistance, and fatigue behavior, even when manufactured with shorter cycle times than those usually used, and without any other treatment, but also good resistance to hygrothermal aging.
• This makes it possible to provide a composite material which has both the advantage of reducing manufacturing costs, the use of tools implementing shortened cycle times, and also sufficient durability for structural applications.
• These composite articles have in particular a very good maintenance of mechanical properties after hygrothermal aging, particularly compared to conventional composite polyamide articles.
• the articles according to the invention have in particular the advantages of rigidity, lightness, and recyclability, and a good surface appearance.
• the invention firstly relates to a method of manufacturing a composite article comprising at least:
• the present invention also relates to a composite article comprising at least one reinforcing fabric and a polyamide matrix comprising from 5 to 50% by weight of novolac resin.
• Said polyamide matrix preferably having a melt viscosity ⁇ of between 1 and 50 Pa.
• fabric is meant a textile surface of yarns or fibers possibly joined together by any method, such as, in particular, gluing, felting, braiding, weaving or knitting. These fabrics are also referred to as fibrous or filamentary networks.
• wire is meant a monofilament, a continuous multifilament yarn, a spun yarn, obtained from a single type of fiber or several types of fibers in intimate mixture. The continuous wire can also be obtained by assembling several multifilament yarns.
• fiber is meant a filament or a set of cut, cracked or converted filaments.
• the yarns and / or reinforcing fibers according to the invention are preferably chosen from among the yarns and / or the fibers of carbon, glass, aramids, polyimides, flax, hemp, sisal, coir, jute, kenaf and / or their mixture. More preferably, the reinforcement fabrics consist solely of yarns and / or reinforcing fibers chosen from among the yarns and / or the fibers of carbon, glass, aramids, polyimides, flax, hemp, sisal, coir, jute, kenaf and / or their mixture.
• These fabrics are preferably a grammage, that is to say the weight per square meter, between 100 and 1000 g / m 2 .
• a composite article according to the invention may comprise several reinforcing fabrics of different nature or not.
• the polyamide according to the invention has a melt viscosity ⁇ of between 1 and 50 Pa.s. This viscosity can be measured using a plane-plane rheometer with a diameter of 50 mm, under a shear stripping analysis ranging from 1 to 160 s -1.
• the polymer is in the form of a film with a thickness of 150 ⁇ m. , granules or powder.
• the polymer is brought to a temperature of 25 to 30 ° C. above its melting point, and the measurement is then carried out.
• the molecular weight (Mn) of the polyamides is preferably greater than 8000, more preferably between 8000 and 20000, having sufficient mechanical properties and a certain resistance during the different shaping processes. Semi-crystalline polyamides are particularly preferred.
• the polyamides may be chosen from the group comprising the polyamides obtained by polycondensation of at least one aliphatic dicarboxylic acid linear with an aliphatic, cycloaliphatic, arylaliphatic diamine (MXD) or between at least one aromatic dicarboxylic acid and an aliphatic, cycloaliphatic or aromatic diamine, the polyamides obtained by polycondensation of at least one amino acid or lactam on itself, or their mixture and (co) polyamides.
• MXD aliphatic dicarboxylic acid linear with an aliphatic, cycloaliphatic, arylaliphatic diamine
• the polyamide of the invention is especially chosen from the group comprising polyamides obtained by polycondensation of at least one aliphatic dicarboxylic acid with an aliphatic or cyclic diamine such as PA 6.6, PA 6.10, PA 6.12, PA 12.12, PA 4.6, MXD. Or between at least one aromatic dicarboxylic acid and an aliphatic or aromatic diamine such as polyterephthalamides, polyisophthalamides, polyaramids, or their mixture and (co) polyamides.
• the polyamide of the invention may also be chosen from polyamides obtained by polycondensation of at least one amino acid or lactam on itself, the amino acid being able to be generated by the hydrolytic opening of a lactam ring such that, for example PA 6, PA 7, PA 11, PA 12, or their mixture and (co) polyamides.
• Polyamides of high fluidity can in particular be obtained by controlling their molecular weight during their synthesis, in particular by the addition before or during the polymerization of polyamide monomers, chain length-changing monomers, such as in particular diamines, dicarboxylic acids. , monoamines and / or mono carboxylic acids. It is also possible to add multifunctional compounds to the polymerization.
• Polyamides according to the invention may also be obtained by mixing, in particular melt, polyamides with chain length-changing monomers, such as in particular diamines, dicarboxylic acids, monoamines and / or mono carboxylic acids.
• chain length-changing monomers such as in particular diamines, dicarboxylic acids, monoamines and / or mono carboxylic acids.
• composition of the invention may also comprise copolyamides derived in particular from the above polyamides, or mixtures of these polyamides or (co) polyamides. It is also possible to use, as high-flow polyamide, a star polyamide comprising star macromolecular chains and, where appropriate, linear macromolecular chains.
• the star-structured polyamide is a polymer comprising star macromolecular chains, and optionally linear macromolecular chains.
• the polymers comprising such star macromolecular chains are for example described in the documents FR2743077, FR2779730, EP0682057 and EP0832149. These compounds are known to exhibit improved fluidity over linear polyamides.
• the star macromolecular chains comprise a core and at least three branches of polyamide.
• the branches are linked to the heart by a covalent bond, via an amide group or a group of another nature.
• the core is an organic or organometallic chemical compound, preferably a hydrocarbon compound optionally comprising heteroatoms and to which the branches are connected.
• the branches are polyamide chains.
• the polyamide chains constituting the branches are preferably of the type obtained by polymerization of lactams or amino acids, for example of the polyamide 6 type.
• the polyamide star structure according to the invention optionally comprises, in addition to star chains, linear polyamide chains.
• the ratio by weight between the quantity of star chains and the sum of the quantities of star and linear chains is between 0.5 and 1 inclusive. It is preferably between 0.6 and 0.9.
• the star-shaped polyamide that is to say comprising star macromolecular chains, is obtained by copolymerization of a monomer mixture comprising at least:
• R1 is a hydrocarbon radical comprising at least 2 carbon atoms, linear or cyclic, aromatic or aliphatic and which may comprise heteroatoms,
• A is a covalent bond or an aliphatic hydrocarbon radical which may comprise heteroatoms and comprising from 1 to 20 carbon atoms,
• Z represents a primary amine function or a carboxylic acid function
• Y is a primary amine function when X represents a carboxylic acid function, or Y is a carboxylic acid function when X represents a primary amine function,
• n an integer from 3 to 8.
• carboxylic acid means carboxylic acids and their derivatives, such as acid anhydrides, acid chlorides, amides or esters.
• the polymerization reaction is advantageously carried out until the thermodynamic equilibrium is reached.
• the monomer of formula (I) may also be mixed with a polymer in the course of an extrusion process.
• the polyamide with star structure is obtained by melt blending, for example using an extrusion device, a polyamide of the type obtained by polymerization. lactams and / or amino acids and a monomer of formula (I). Such methods of obtaining are described in patents EP0682070 and EP0672703.
• the radical R 1 is either a cycloaliphatic radical such as the tetravalent radical of cyclohexanonyl, or a radical 1, 1, 1-triylpropane, 1, 2,3-thylpropane.
• radicals R1 suitable for the invention mention may be made, by way of example, of the trivalent radicals of phenyl and cyclohexanyl, which may or may not be substituted, the tetravalent diaminopolymethylene radicals with a number of methylene groups advantageously between 2 and 12, such as the radical from EDTA (ethylene diamino tetracetic acid), octovalent radicals of cyclohexanonyl or cyclohexadinonyl, and radicals derived from compounds derived from the reaction of polyols such as glycol, pentaerythritol, sorbitol or mannitol with acrylonitrile.
• EDTA ethylene diamino tetracetic acid
• octovalent radicals of cyclohexanonyl or cyclohexadinonyl radicals derived from the reaction of polyols such as glycol, pentaerythritol, sorb
• radical A is preferably a methylene or polymethylene radical such as ethyl, propyl or butyl radicals or a polyoxyalkylene radical such as the polyoxyethylene radical.
• the number m is greater than or equal to 3 and advantageously equal to 3 or 4.
• the reactive function of the multifunctional compound represented by the symbol Z is a function capable of forming an amide function.
• the compound of formula (I) are chosen from 2,2,6,6-tetra- ( ⁇ -carboxyethyl) -cyclohexanone, trimesic acid, 2,4,6-th- (aminocaproic acid) -1,3,5-thazine and 4-aminoethyl-1,8-octanediamine.
• the monomer mixture at the origin of the star macromolecular chains may comprise other compounds, such as chain limiters, catalysts.
• the following compounds are not necessarily part of the monomer mixture at the origin of the star structure. but may be added to the synthesis or after: additives, such as light stabilizers, heat stabilizers, and lubricants.
• composition according to the invention preferably has from 50 to 95% by weight of polyamide, relative to the total weight of the composition, preferably from 75 to 90%.
• Novolac resins are generally condensation products of phenolic compounds with aldehydes or ketones or their derivatives such as ketal or hemiketal functions. These condensation reactions are generally catalyzed by an acid or a base.
• the polyamide according to the invention may comprise one or more types of different novolac resin.
• Novolac resins generally have a degree of condensation of between 2 and 15.
• the phenol compounds can be chosen alone or as a mixture from phenol, cresol, xylenol, naphthol, alkylphenols, such as butylphenol, terbutylphenol, isooctylphenol, nitrophenol, phenylphenol, resorcinol or biphenol A; or any other substituted phenol.
• aldehyde is formaldehyde.
• others may be used, such as acetaldehyde, paraformaldehyde, butyraldehyde, crotonaldehyde, glycoxal, and furfural.
• ketone it is possible to use acetone, methyl ethyl ketone or acetophenone.
• the resin is a condensation product of phenol and formaldehyde.
• the novolac resins used advantageously have a molecular weight of between 500 and 3000 g / mol, preferably between 800 and 2000 g / mol.
• the polyamide composition comprises from 5 to 50% by weight of novolac resin, more preferably from 10 to 25% by weight, relative to the total weight of the composition.
• the percentage by weight is represented with respect to the total weight of the composition.
• the polyamide composition according to the invention comprising novolac resin is especially used as a matrix, in particular by granulation, calendering, extrusion in the form of a film, grinding, injection, molding, injection molding, pressing, and others.
• the impregnation step of the polyamide composition of the invention and the reinforcing fabric can be carried out in various ways, according to various possible methods. It is perfectly possible to impregnate one or more reinforcing fabric.
• the melt polyamide composition may be injected into a molding chamber comprising at least one or more reinforcing fabrics.
• the interior of the molding chamber is at a temperature of roughly 50 0 C above the melting point of said polyamide. It is then possible to cool the molding chamber and the article obtained to finally recover said article.
• This process is also known as the thermoset process for resin transfer molding (RTM), which consists in injecting resin into a closed mold in which reinforcing fibers have been previously placed. This process can be carried out under pressure.
• RTM resin transfer molding
• the composite article according to the invention may also be produced by bringing one or more reinforcing fabrics into contact with the powder of a polyamide as defined above, in particular of the fine powder, and the said impregnation is carried out. by melting the polyamide at a temperature equal to or greater than that of the melting point of the polyamide, optionally under pressure.
• the composite article of the invention can also be made by pultrusion. This technique generally involves drawing through a heated die one or more continuous yarns and fibers so as to impregnate it with a molten thermoplastic resin to obtain a rod or finished or semi-finished article.
• the article After impregnation of the reinforcing fabric with the polyamide, the article is obtained by solidification of the matrix.
• the cooling can advantageously be carried out rapidly so as to avoid significant crystallization of the polyamide, in particular to maintain the properties of the article.
• the cooling may especially be carried out in less than 5 minutes, more preferably less of a minute.
• the mold may for example be cooled by a cold fluid circuit. It is also possible to transfer the composite article to a cold mold, possibly under pressure.
• the polyamide composition and / or the composite article according to the invention may also comprise all the additives normally used in polyamide-based compositions used for the manufacture of articles.
• additives include thermal stabilizers, UV stabilizers, antioxidants, lubricants, pigments, dyes, plasticizers, reinforcing fillers, and impact-modifying agents.
• Additives to improve the quality of the polyamide reinforcing fabric interfaces can also be used. These additives may for example be incorporated into the polyamide composition, incorporated into the threads and / or fibers of the reinforcing fabric, present on the threads and / or fibers of said fabric, or else deposited on the reinforcing fabric. These additives may be coupling agents such as those of aminosilane or chlorosilane type, or fluidizing or wetting agents, or their combination. Reinforcing fillers may be incorporated in the polyamide composition. These fillers may be chosen from fibrous fillers, such as short glass fibers, for example, or non-fibrous fillers such as kaolin, talc, silica, mica or wollastonite. Their size is generally between 1 and 25 microns. Sub-micron or even nanometric charges may also be used, alone or in addition to other charges.
• the present invention relates to an article obtainable by the method of the invention.
• the article may in particular be a polyamide-based composite article comprising a reinforcing fabric, in which the polyamide has a melt viscosity ⁇ of between 1 and 50 Pa ⁇ s.
• the articles according to the invention preferably comprise between 25 and 70% by volume of reinforcing fabric with respect to the total volume.
• the composite articles preferably have a reinforcement ratio of 50% by volume with a tensile stress greater than 480 MPa and an elastic modulus of greater than 20 GPa (for a void ratio typically between 0 and 2%).
• the articles of the invention may be finished or semi-finished articles which may also be called prepregs.
• prepregs it is possible to thermoform composite articles in the form of plates to give them a defined shape after cooling.
• the invention thus relates to composite articles or preforms that can be obtained by the method according to the present invention.
• the articles of the invention may also be sandwich type structures having a core inserted between two skins.
• the composites of the invention can be used to form the outer layers, by associating them with a core type honeycomb or foam type.
• the layers can be assembled by chemical or thermal bonding.
• Composite structures according to the invention can be used in many fields such as aeronautics, automotive, energy, electrical industry, sports and leisure industry. These structures can be used to make sports articles such as skis or to achieve various surfaces such as special floors, partitions, vehicle bodies, or billboards. In aeronautics these structures are used in particular at fairings (fuselage, wing, empennage). In the automobile, they are used for example at floors, supports such as rear shelves, or at the level of structural parts.
• PA C2 high fluidity polyamide 6.6 having an IV viscosity index of 97 and a mass Mw of 11,200.
• PA 3 polyamide 6 .6 high fluidity having an IV viscosity index of 97, modified by addition of 10% by weight of novolac resin.
• PA 4 high fluidity polyamide 6.6 having a viscosity index IV of 97, modified by addition of 20% by weight of novolac resin.
• the reinforcements used in the examples are in the form of glass fabric preforms, cut to the dimensions required for the manufacture of the plates, that is to say 150 ⁇ 150 mm or 200 ⁇ 300 mm.
• the reinforcing fabric used is a fiberglass fabric (0 ° -90 °) of Synteen & Luckenhaus origin from a roving of 1200 tex, having a basis weight of 600 g / m 2 .
• the various polymers considered are used in powder form for the most fluid, if not in film form.
• the powders are obtained by cryogenic grinding, either in dry ice or in liquid nitrogen.
• the films are made by extrusion of granules on a twin-screw Leistritz extruder 34 and L / D 34 equipped with a flat die and a smoker (extruder output 10 Kg / h, screw speed 250 rpm; temperature of 270 ° C. for PA 6.6).
• the spacing of the lips of the die is about 300 ⁇ m for a width of 30 cm with a call speed of 3.2 m / min on rolls regulated at 115 ° C: the films obtained have a thickness that varies between 160 and 180 ⁇ m (coils 280 mm wide).
• the polymer films are cut into sheets of 150x150 mm or 200x300 mm, from the previously obtained coils. It is the same for reinforcement fabrics.
• Composite parts are produced using a Schwabenthan (Polystat 300A) temperature-controlled double-plate hydraulic press: hot plates (heating resistors) and cooled trays (circulation). of water).
• a metal mold with a print size of 150 mm x 150 mm or 200x300 mm is used.
• a metal frame is introduced into the mold in which is placed a preform consisting of an alternating stack comprising 6 sheets of glass cloth and between each is a sheet of polymer, or uniformly distributed powder, the two outer layers being sheets of glass cloth.
• the temperature of the platens of the press is previously mounted either at 250 0 C for PA 6 or 290 0 C for PA 6.6 before the introduction of the preform. At this temperature, the pressure is applied between 1 and 50 bar and maintained at this value; degassing is done quickly. The assembly is maintained at the same temperature and pressure, without degassing. Again, it is then carried out a series of degassing, then a maintenance always at the same temperature and pressure. The mold is then transferred to the cooled platen device and maintained at a pressure of between 1 and 50 bar.
• the composite parts thus obtained have a dimension of 150 ⁇ 150 mm or 200 ⁇ 300 mm and a thickness of about 2 mm.
• a cycle of 5 minutes under an average pressure of 15 to 50 bar was carried out: 1 min. under 15 bar, then 1 min at 50 bar, then 2 min at 50 bar). This time corresponds to the total duration of the cycle between the temperature setting of the mold and the cooling under pressure (1 min.).
• the sheets 150x150 mm or 200x300 mm are cut to obtain samples of dimensions 150x20x2 mm.
• a first series of samples are characterized just after manufacture (sample placed in a sealed envelope, in order to keep them in a dry state RHO).
• a conditioning treatment can also be carried out according to the ISO1110 standard "plastic / polyamide / accelerated packaging of test pieces": state said RH50.
• the equilibrium water content is obtained by conditioning the composite parts with a cycle of 10 days, at 70 ° C. under a residual humidity RH of 62%.
• the 3-point bending tests at room temperature are carried out on parallepipedic specimens (150x20x2 mm), according to ISO standard No. 14125, on a ZWICK 1478 machine: 64 mm center distance, 5 mm / min crosshead speed. Young's elastic modulus E (GPa) and maximum stress ⁇ max (MPa) values are measured and calculated. Direct tensile tests at room temperature are carried out on parallepipedic specimens (250x25x2mm), according to ASTM D3039 / D3039M on a ZWICK 1478 machine: traverse speed of 1 to 5 mm / min. The elastic modulus values of Young E (GPa) and peak stress ⁇ max (MPa) are measured and calculated.
• the tensile failure mode is much more abrupt than in the case of polyamides without novolac resin.
• Example 3 The samples prepared according to Example 3 were subjected to hygrothermal aging.
• a first type of aging was carried out by immersion in water at 65 ° C. for 65 days (see “AMOCO” test).
• test pieces After aging, the test pieces are reconditioned: removal of the adsorbed water by treatment of the test pieces at 90 ° C. under vacuum for 24 h, then stabilization at RH 50 by conditioning with a cycle of 10 days, at 70 ° C. under a residual humidity RH of 62%.
• the 3-point bending tests at room temperature are carried out on parallepipedic specimens (150x20x2 mm), according to ISO standard No. 14125, on a ZWICK 1478 machine: 64 mm center distance, 5 mm / min crosshead speed. Young's elastic modulus E (GPa) and maximum stress ⁇ max (MPa) values are measured and calculated.
• a second type of aging was carried out by immersion in water at 80 ° C. for 8 days (accelerated test).
• test pieces were either tested as such or reconditioned by removal of the adsorbed water: treatment at 80 ° C. under vacuum for 24 hours (RHO).
• the 3-point bending tests at room temperature are carried out on parallepipedic specimens (150x20x2 mm), according to ISO standard No. 14125, on a ZWICK 1478 machine: 64 mm center distance, 5 mm / min crosshead speed. Young's elastic modulus E (GPa) and maximum stress ⁇ max (MPa) values are measured and calculated.

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