Liquid composition for filament winding, its process of polymerization, use and object obtained following polymerization of composition

Abstract

The present invention relates to a liquid composition for filament winding comprising a monomer, a (meth)acrylic polymer and at least an initiator. In particular the present invention relates to a liquid composition for filament winding comprising a monomer, a (meth)acrylic polymer and at least one initiator or two initiators that have a different half life time, its process of polymerization, a system for the process of polymerization and an object obtained. The present invention also relates to a process for manufacturing thermoplastic composites, mechanical parts or structural elements made of composite material and to mechanical parts or structural elements made of composite material obtained via the process using such a liquid composition. The thermoplastic composite is a hollow body, and more preferably an axisymmetric hollow body.

Description

LIQUID COMPOSITION FOR FILAMENT WINDING, ITS PROCESS OF POLYMERIZATION, USE AND OBJECT OBTAINED FOLLOWING POLYMERIZATION OF COMPOSITION[Field of the invention]

[0001] The present invention relates to a liquid composition for filament winding comprising a monomer, a (meth) acrylic polymer and at least an initiator.

[0002] In particular the present invention relates to a liquid composition for filament winding comprising a monomer, a (meth) acrylic polymer and at least one initiator or two initiators that have a different half life time, its process of polymerization, a system for the process of polymerization and an obj ect obtained.

[0003] The present invention also relates to a process for manufacturing thermoplastic composites, mechanical parts or structural elements made of composite material and to mechanical parts or structural elements made of composite material obtained via the process using such a liquid composition. The thermoplastic composite is a hollow body, and more preferably an axisymmetric hollow body.[Prior art]

[0004] Thermoplastic polymers are materials that are widely used today in several fields and applications, for example in the construction, aeronautic, automobile or railway sectors, where they are part of mechanical parts.

[0005] These mechanical parts that have to withstand high stresses during their use are widely manufactured from composite materials. A composite material is a macroscopic combination of two or more immiscible materials. The composite material consists of at least one material which forms the matrix, i. e. a continuous phase that ensures the cohesion of the structure, and a reinforcing material.

[0006] The purpose of using a composite material is to obtain performance qualities that are not available from each of its constituents when they are used separately. Consequently, compositematerials are widely used in several industrial sectors, for instance building, automotive, aerospace, transport, leisure, electronics, and sports notably due to their better mechanical performance (higher tensile strength, higher tensile modulus, higher fracture toughness) and their low density, in comparison with homogeneous materials.

[0007] To allow and facilitate recycling, it is preferred to use thermoplastic polymers also in composite materials, instead of thermoset materials.

[0008] Thermoplastic polymers consist of linear or branched polymers, which are usually not crosslinked. The thermoplastic polymers are heated in order to mix the constituents necessary for manufacturing the composite material and are cooled to set the final form. The problem of these molten thermoplastic polymers is their very high viscosity. In order to prepare a polymeric composite material based on thermoplastic polymer, a liquid composition or liquid thermoplastic polymer composition, commonly known as a "syrup", is used to impregnate the reinforcing material, for example a fibrous substrate. Once polymerized, the thermoplastic polymeric composition constitutes the matrix of the composite material.

[0009] At the time of impregnation, when preparing polymeric composites, the viscosity of the impregnation syrup must be controlled and adapted so as not to be too fluid or too viscous, so as to impregnate correctly each fibre of the fibrous substrate. When the impregnation or wetting is partial, depending on whether the syrup is too fluid or too viscous, either so called "dry" zones, i. e. non- impregnated zones, or zones in which larger drops of polymer form on the fibres, which are the cause of the creation of bubbles, respectively appear. These "dry" zones and these bubbles give rise to the appearance of defects in the final composite material, which are the cause, inter alia, of a loss of mechanical strength of the final composite material.

[0010] Also especially in case of filament winding when the obj ect is made by several layers of impregnated fibrous material, a shrinkage of the volume while polymerizing for obtaining a thermoplastic matrix, yields to defects in the structure. Thesedefects consist of a certain porosity and delamination between the respective layers.[Oil] A liquid composition or syrup comprising a (meth) acrylic monomer and a (meth) acrylic polymer is described in the document W02014 / 013028. The polymerization of the monomer (s) is achieved with radical generating initiator (s) or initiating systems comprising radical generation initiator system (s). For both documents benzoyl peroxide is used in the examples.

[0012] The document WO2014 / 174098 discloses a liquid (meth) acrylic syrup. The syrup comprises an initiating system comprising an accelerator, an organic aldehyde, one peracid and one liquid peroxy compound. The polymerization time in the examples of this document is hours or several dozens of minutes.

[0013] The document W02020 / 007919 discloses a fiber reinforced polymer tube. The tube is made by filament winding process which comprises a thermoset epoxy resin, but also polyesters, polyurethane or polyvinyl ester resins.

[0014] The document US2018 / 0265659 discloses a tow prepreg, composite material reinforced pressure vessel and its method of producing. The matrix resin is epoxy and in the method a filament winding step is included.

[0015] The document WO2018 / 115342 discloses a liquid composition that comprises a (meth) acrylic polymer, a (meth) acrylic monomer and two initiators (Inil) and (Ini2). The document does not disclose preparing thermoplastic composites by filament winding, neither a process for manufacturing a thermoplastic composite by filament winding.

[0016] The document WO2019 / 170666 discloses a precursor composition for acrylic thermoplastic composites. The composition comprises two initiators ( Inil) and ( Ini2 ), initiator ( Inil) is activated by absorption of radiation and the initiator ( Ini2) is activated by heat.

[0017] The document W02019 / 102145 discloses a liquid composition for application of SMC moulded thermoplastic composites. The composition comprises beside a (meth) acrylic polymer and a(meth) acrylic monomer either one or both contain a carboxylic acid function, also a maturation agent.

[0018] The document CN115534283 discloses a wound thermoplastic pipe and its manufacturing method. The method requires the step of impregnating a continuous fiber with a prepolymer containing a photoinitiator or / and a free radical initiator, then winding on a core tube and initiating polymerization by irradiation with an ultraviolet light lamp.

[0019] It is not suggested in any of these documents that a liquid (meth) acrylic composition with thermal initiator (s) is suitable for preparing thermoplastic composites by filament winding, neither a process for manufacturing a thermoplastic composite by filament winding.[TECHNICAL PROBLEM]

[0020] The aim of the invention is thus to remedy at least one of the drawbacks of the prior art.

[0021] An obj ective of the present invention is to have a liquid composition comprising a monomer, a (meth) acrylic polymer and at least one initiator for having a composition that can be polymerized fast and to a sufficient conversion while preparing thermoplastic composites by filament winding. By a sufficient conversion is understood that at least 10% of the monomers have been polymerized during filament winding step, preferably at least 15%. By fast is understood that the partly polymerization takes place in less than 60minutes, preferably less than 50min, even more preferably less than 40min and advantageously less than 30min.

[0022] An obj ective of the present invention is also to have a system and a method for polymerizing a liquid composition comprising a monomer, a (meth) acrylic polymer and at least one initiator to a sufficient conversion.

[0023] Another obj ective of the present invention is to use a liquid composition comprising a monomer, a (meth) acrylic polymer and at least one initiator for a method for manufacturing thermoplastic composites by filament winding, preferably the thermoplasticcomposite is a hollow body, and more preferably an axisymmetric hollow body.

[0024] Still another obj ective of the present invention is to propose a composition, a system and a method for preparing thermoplastic composites by filament winding, preferably the thermoplastic composite is a hollow body, and more preferably an axisymmetric hollow body.

[0025] Still another obj ective of the present invention is to propose a composition, a system and a method for preparing thermoplastic composites obj ect by filament winding, preferably the thermoplastic composite obj ect is a hollow body, and more preferably an axisymmetric hollow body, for obtaining an obj ect that can be recycled, has a low porosity and reduced delamination. By low porosity is understood that it is less than 10 vol%, preferably less than 5 vol%. By reduced delamination is understood that there are less zones with delamination.[BRIEF DESCRIPTION OF THE INVENTION]

[0026] It has been discovered, that a liquid composition (LC1) comprisinga) a (meth) acrylic polymer (Pl),b) a (meth) acrylic monomer (Ml), andc) at least one initiator ( Inil),said liquid (meth) acrylic syrup having a dynamic viscosity of between 10 mPa*s and 10 000 mPa*s at 25°C, ) is suitable for preparing thermoplastic composites by filament winding, preferably the thermoplastic composite is a hollow body, and more preferably an axisymmetric hollow body, having low porosity and reduced delamination.

[0027] It has also been discovered that a liquid composition (LC1) comprisinga) a (meth) acrylic polymer (Pl),b) a (meth) acrylic monomer (Ml), andc) at least two initiators ( Inil) and (Ini2);said liquid (meth) acrylic syrup having a dynamic viscosity of between 10 mPa*s and 10 000 mPa*s at 25°C, is suitable for preparing thermoplastic composites by filament winding, preferably the thermoplastic composite is a hollow body, and more preferably an axisymmetric hollow body, having low porosity and reduced delamination.

[0028] It has been discovered as well that process for manufacturing thermoplastic composites by filament winding, preferably the thermoplastic composite is a hollow body, and more preferably an axisymmetric hollow body composite parts by a process comprising the following steps:i) impregnating fibers or fibrous substrate with the liquid composition (LC1) comprisinga) a (meth) acrylic polymer (Pl),b) a (meth) acrylic monomer (Ml), andc) either at least one initiator ( Inil) or at least two initiators (Inil) and ( Ini2);said liquid (meth) acrylic syrup having a dynamic viscosity of between 10 mPa*s and 10 000 mPa*s at 25°C, ii) polymerizing at least a part of the liquid composition (LC1) during winding on a mandrel,yields to thermoplastic composite which is a hollow body, and more preferably an axisymmetric hollow body, having low porosity and reduced delamination, in comparison to a process where not partly polymerization takes place during winding.

[0029] It has also been discovered, that method ( 100 ) for manufacturing a hollow body, preferably an axisymmetric hollow body, comprising a layer of composite material, said process comprising the following steps:- optionally a step of providing ( 105) fibers or fibrous material,- optionally a step of providing ( 110 ) a liquid composition (LC1) comprisinga) a (meth) acrylic polymer (Pl),b) a (meth) acrylic monomer (Ml), andc) either at least one initiator (Inil) or at least two initiators (Inil) and ( Ini2);said liquid (meth) acrylic syrup having a dynamic viscosity of between 10 mPa*s and 10 000 mPa*s at 25°C;- a step of impregnating ( 120 ) a fibrous material with the liquid composition (LC1) comprisinga) a (meth) acrylic polymer (Pl),b) a (meth) acrylic monomer (Ml), andc) either at least one initiator ( Inil) or at least two initiators (Inil) and ( Ini2);said liquid (meth) acrylic syrup having a dynamic viscosity of between 10 mPa*s and 10 000 mPa*s at 25°C;- a step of winding ( 130 ) the impregnated fibrous material around a mandrel, said winding being carried out for a winding duration tl; anda step of heating (140 ) the wound fibrous material at a temperature Th, said heating being carried out for a heating duration t2 to polymerize a part the (meth) acrylic monomer (Ml) of the liquid composition (LC1);yields to thermoplastic composite which is a hollow body, and more preferably an axisymmetric hollow body, having low porosity and reduced delamination, in comparison to a process where heating takes place during winding.

[0030] Moreover, it has also been discovered that a composite part obtained by the manufacturing method, is having a significantly lower porosity and reduced delamination.Brief description of drawings

[0031] The foregoing and other obj ects, features and advantages of the present invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings in which:Figure 1 represents a flowchart of the method according to an embodiment of the invention.Figure 2 represents a schematic view of an embodiment of the system ( 1).[DETAILED DESCRIPTION]

[0032] According to a first aspect, the present invention relates to a liquid composition (LC1) suitable for preparing thermoplastic composites by filament winding, preferably the thermoplastic composite is a hollow body, and more preferably an axisymmetric hollow body, said composition comprising:a) a (meth) acrylic polymer (Pl),b) a (meth) acrylic monomer (Ml), andc) at least one initiator ( Inil),said liquid composition (LC1) is having a dynamic viscosity of between 10 mPa*s and 10 000 mPa*s at 25°C.

[0033] According to a second aspect, the present invention relates to a liquid composition (LC1) suitable for preparing thermoplastic composites by filament winding, preferably the thermoplastic composite is a hollow body, and more preferably an axisymmetric hollow body, said composition comprises:a) a (meth) acrylic polymer (Pl),b) a (meth) acrylic monomer (Ml), andc) at least two initiators (Inil) and (Ini2),said liquid composition (LC1) is having a dynamic viscosity of between 10 mPa*s and 10 000 mPa*s at 25°C.

[0034] According to a third aspect, the present invention relates to the use of a liquid composition (LC1) for for manufacturing thermoplastic composite parts by filament winding.

[0035] According to a fourth aspect, the present invention relates to a system ( 1) for preparing thermoplastic composites by filament winding, preferably the thermoplastic composite is a hollow body, and more preferably an axisymmetric hollow body, said system ( 1) comprises:a fiber spool (s) ( 10 ),impregnation means (20 ) for impregnating the fibers ( 15) with liquid composition (LC1),a mandrel (30 ),heating means (40 ), andoptionally temperature controlling means (50 ).

[0036] According to a fifth aspect, the present invention relates to process for manufacturing thermoplastic composites by filament winding, preferably the thermoplastic composite is a hollow body, and more preferably an axisymmetric hollow body composite parts by a process comprising the following steps:i) impregnating fibers or fibrous substrate with the liquid composition (LC1) according to the first or second aspect, ii) polymerizing at least a part of the liquid composition (LC1) during the winding on a mandrel.

[0037] According to a sixth aspect, the present invention relates to a method ( 100 ) for manufacturing a thermoplastic composite, preferably a hollow body, preferably an axisymmetric hollow body, comprising a layer of composite material, said method or process comprising the following steps:- optionally a step of providing ( 105) fibers or fibrous material,- optionally a step of providing ( 110) the liquid composition (LC1) according to the first or second aspect;- a step of impregnating ( 120) a fibrous material with the liquid composition (LC1);- a step of winding (130 ) the impregnated fibrous material around a mandrel, said winding being carried out for a winding duration t1; and- a step of heating ( 140 ) the wound fibrous material at a temperature Th, said heating being carried out for a heating duration t2in order to polymerize a part the (meth) acrylic monomer (Ml) of the liquid composition (LC1).

[0038] The term " fibrous substrate" as used refers to several fibres, uni directional rovings or continuous filament mat, fabrics, felts or nonwovens that may be in the form of strips, laps, braids, locks or pieces.

[0039] The term " (meth) acrylic" as used refers to any type of acrylic or methacrylic monomer.

[0040] The term "PMMA" as used refers to homo- and copolymers of methyl methacrylate (MMA), the weight ratio of MMA in the PMMA being at least 70 wt% for the MMA copolymer.

[0041] The term "monomer" as used refers to a molecule that can undergo polymerization.

[0042] The term "polymerization" as used refers to the process of converting a monomer or a mixture of monomers into a polymer.

[0043] The term "thermoplastic polymer" as used refers to a polymer that turns to a liquid or becomes more liquid or less viscous of soft when heated and that can take on new shapes by the application of heat and pressure. This applies also for slightly crosslinked thermoplastic polymers that can be thermoformed when heated above the softening temperature.

[0044] The term "polymer composite" as used refers to a multicomponent material comprising several different phase domains, among which at least one type of phase domain is a continuous phase and in which at least one component is a polymer.

[0045] The term "initiator" as used refers to a compound that can start / initiate the polymerization of a monomer or monomers.

[0046] The term "half life time" t1 / 2 as used refers to the time needed for an initial amount of initiator to decrease concentration in half. This time is a function of the temperature.

[0047] By the abbreviation "phr" is meant weight parts per hundred parts of composition. For example Iphr of initiator in the composition means that 1kg of initiator is added to 100kg of composition.

[0048] By the abbreviation "ppm" is meant weight parts per million parts of composition. For example lOOOppm of a compound in the composition means that 0. 1kg of compound is present in 100kg of composition.

[0049] By saying that a range from x to y in the present invention, it is meant that the upper and lower limit of this range are included, equivalent to at least x and up to y.

[0050] By saying that a range is between x and y in the present invention, it is meant that the upper and lower limit of this range are excluded, equivalent to more than x and less than y.

[0051] The liquid composition (LC1) or (meth) acrylic syrup according to the invention comprises a (meth) acrylic monomer (Ml) or a mixture of (meth) acrylic monomers (Ml) and (Ml+x), a (meth) acrylic polymer (Pl) and at least one initiator (Inil).

[0052] According to a first preferred embodiment the liquid composition (LC1) comprises one initiator ( Inil).

[0053] According to a second preferred embodiment the liquid composition (LC1) comprises at least two initiators ( Inil) and ( Ini2 ).

[0054] According to a third preferred embodiment the liquid composition (LC1) comprises more than two initiators.

[0055] The dynamic viscosity of the liquid composition or (meth) acrylic syrup is in a range from 10 mPa*s to 10000 mPa*s, preferably from 20 mPa*s to 7000 mPa*s and advantageously from 20 mPa*s to 5000 mPa*s and more advantageously from 20 mPa*s to 2000 mPa*s and even more advantageously between 20mPa*s and 1000 mPa*s. The viscosity of the syrup can be easily measured with a Rheometer or viscosimeter. The dynamic viscosity is measured at 25°C. If the liquid (meth) acrylic syrup has a Newtonian behaviour, meaning no shear thinning, the dynamic viscosity is independent of the shearing in a rheometer or the speed of the mobile in a viscometer. If the liquid composition has a non-Newtonian behaviour, meaning shear thinning, the dynamic viscosity is measured at a shear rate of Is-1at 25°C.

[0056] The liquid composition (LC1) or (meth) acrylic syrup according to the invention, for impregnating the fibrous substrate, especially comprises a (meth) acrylic monomer or a mixture of (meth) acrylic monomers, a (meth) acrylic polymer and either at least one initiator ( Inil) or at least two initiators ( Inil) and ( Ini2 ).

[0057] As regards the liquid composition (LC1) of the invention it comprises a (meth) crylic monomer (Ml), a (meth) acrylic polymer (Pl) and either at least one initiator ( Inil) or at least two initiators ( Inil) and ( Ini2 ). Once polymerized the (meth) acrylicmonomer (Ml) is transformed to a (meth) acrylic polymer (P2) comprising the monomeric units of (meth) acrylic monomer (Ml).

[0058] The quantity of either the at least one initiator ( Inil) or the at least two initiators ( Inil) and ( Ini2 ) together in the composition is at least 0. Iphr relative to the sum of (meth) acrylic monomer (Ml) and (meth) acrylic polymer (Pl). Preferably the quantity of either at least one initiator ( Inil) or at least two initiators ( Inil) and ( Ini2) together in the composition is at least 0. 12 phr, more preferably at least 0. 15phr, even more preferably at least 0.17phr and advantageously at least 0. 2phr relative to the sum of (meth) acrylic monomer (Ml) and (meth) acrylic polymer (Pl).

[0059] The quantity of either at least one initiator ( Inil) or at least two initiators ( Inil) and ( Ini2 ) together in the composition is at most 15phr of relative to the sum of (meth) acrylic monomer (Ml) and (meth) acrylic polymer (Pl). Preferably the quantity of either at least one initiator ( Inil) or at least two initiators ( Inil) and ( Ini2 ) together in the composition is at most 12phr, more preferably at most lOphr, even more preferably at most 8phr and advantageously at most 5phr relative to the sum of (meth) acrylic monomer (Ml) and (meth) acrylic polymer (Pl).

[0060] The quantity of either at least one initiator ( Inil) or the at least two initiators ( Inil) and ( Ini2 ) together in the composition is between 0. Iphr and 15phr relative to the sum of (meth) acrylic monomer (Ml) and (meth) acrylic polymer (Pl). Preferably the quantity of either at least one initiator ( Inil) or the at least two initiators ( Inil) and ( Ini2 ) together in the composition is between 0. 12phr and 12phr, more preferably between 0.15phr and lOphr, even more preferably between 0. 17phr and 8phr and advantageously at most between 0. 2phr and 5phr relative to the sum of (meth) acrylic monomer (Ml) and (meth) acrylic polymer (Pl).

[0061] As regards the (meth) acrylic monomer (Ml), the monomer is chosen from acrylic acid, methacrylic acid, alkyl acrylic monomers, alkyl methacrylic monomers, hydroxyalkyl acrylic monomers and hydroxyalkyl methacrylic monomers, and mixtures thereof.

[0062] Preferably, the (meth) acrylic monomer (Ml) is chosen from acrylic acid, methacrylic acid, hydroxyalkyl acrylic monomers,hydroxyalkyl methacrylic monomers, alkyl acrylic monomers, alkyl methacrylic monomers and mixtures thereof, the alkyl group containing from 1 to 22 linear, branched or cyclic carbons; the alkyl group preferably containing from 1 to 12 linear, branched or cyclic carbons.

[0063] Advantageously, the (meth) acrylic monomer (Ml) is chosen from methyl methacrylate, ethyl methacrylate, methyl acrylate, ethyl acrylate, methacrylic acid, acrylic acid, n-butyl acrylate, isobutyl acrylate, n-butyl methacrylate, isobutyl methacrylate, cyclohexyl acrylate, cyclohexyl methacrylate, isobornyl acrylate, isobornyl methacrylate, hydroxyethyl acrylate and hydroxyethyl methacrylate, and mixtures thereof.

[0064] According to a preferred embodiment, at least 50% by weight and preferably at least 60% by weight of the (meth) acrylic monomer (Ml) is methyl methacrylate.

[0065] According to a first more preferred embodiment, at least 50% by weight, preferably at least 60% by weight, more preferably at least 70% by weight, advantageously at least 80% by weight and even more advantageously 90% by weight of the monomer (Ml) is a mixture of methyl methacrylate with optionally at least one other monomer.

[0066] As regards the (meth) acrylic polymer (Pl), mention may be made of polyalkyl methacrylates or polyalkyl acrylates. According to a preferred embodiment, the (meth) acrylic polymer is polymethyl methacrylate (PMMA).

[0067] The term "PMMA" denotes a methyl methacrylate (MMA) homopolymer or copolymer or mixtures thereof. Preferably the (meth) acrylic polymer (Pl) comprises at least 50% by weight of methyl methacrylate (MMA).

[0068] According to one embodiment, the methyl methacrylate (MMA) homo- or copolymer comprises at least 70%, preferably at least 80%, advantageously at least 90% and more advantageously at least 95% by weight of methyl methacrylate.

[0069] According to another embodiment, the PMMA is a mixture of at least one homopolymer and at least one copolymer of MMA, or a mixture of at least two homopolymers or two copolymers of MMA witha different average molecular weight, or a mixture of at least two copolymers of MMA with a different monomer composition.

[0070] The copolymer of methyl methacrylate (MMA) comprises from 70% to 99.7% by weight of methyl methacrylate and from 0.3% to 30% by weight of at least one monomer containing at least one ethylenic unsaturation that can copolymerize with methyl methacrylate.

[0071] These monomers are well known and mention may be made especially of acrylic and methacrylic acids and alkyl (meth) acrylates in which the alkyl group contains from 1 to 12 carbon atoms. As examples, mention may be made of methyl acrylate and ethyl, butyl or 2 -ethylhexyl (meth) acrylate. Preferably, the comonomer is an alkyl acrylate in which the alkyl group contains from 1 to 4 carbon atoms.

[0072] According to a first preferred embodiment, the copolymer of methyl methacrylate (MMA) comprises from 80% to 99.7%, advantageously from 90% to 99.7% and more advantageously from 90% to 99.5% by weight of methyl methacrylate and from 0.3% to 20%, advantageously from 0.3% to 10% and more advantageously from 0.5% to 10% by weight of at least one monomer containing at least one ethylenic unsaturation that can copolymerize with methyl methacrylate. Preferably, the comonomer is chosen from methyl acrylate and ethyl acrylate, and mixtures thereof.

[0073] The weight-average molecular mass of the (meth) acrylic polymer (Pl) should be high, which means greater than 50 000 g / mol and preferably greater than 100 000 g / mol.

[0074] The weight-average molecular mass can be measured by size exclusion chromatography (SEC).

[0075] The (meth) acrylic polymer is fully soluble in the (meth) acrylic monomer or in the mixture of (meth) acrylic monomers. It enables the viscosity of the (meth) acrylic monomer or the mixture of (meth) acrylic monomers to be increased. The solution obtained is generally called a " syrup" or "prepolymer". The dynamic viscosity value of the liquid (meth) acrylic syrup is between 10 mPa. s and 10 000 mPa. s. The viscosity of the syrup can be readily measured with a rheometer or a viscometer. The dynamic viscosity is measured at 25°C.

[0076] Advantageously, the liquid (meth) acrylic syrup contains no additional voluntarily added solvent.

[0077] With regard to the two initiators (Inil) and (Ini2), the initiators generate radicals that initiate the monomer (s) to start a radical polymerization of the monomer in order to form the polymer chains by propagation.

[0078] Preferably the initiators ( Inil) and (Ini2) are activated by heat.

[0079] The heat activated initiators ( Inil) and ( Ini2 ) are preferably radical initiators.

[0080] The radical initiators ( Inil) and ( Ini2) can be chosen from peroxy group comprising compound or azo group comprising compounds and preferably from peroxy group comprising compound.

[0081] Preferably the peroxy group comprising compound comprises from 2 to 30 carbon atoms.

[0082] Preferably the peroxy group comprising compound is chosen from diacyl peroxides, peroxy esters, peroxydicarbonates, dialkyl peroxides, peroxyacetals, hydroperoxide or peroxyketale.

[0083] Preferably, if two initiators are present in the liquid composition (LC1), the two initiators ( Inil) and ( Ini2 ) have at any given temperature Ti different half -life times ti / 2.

[0084] Still more preferably the second initiator ( Ini2 ) has at a given temperature Ti a half -life time ti / 2that is at least two times of the half -life time ti / 2of the first initiator ( Inil). Even more preferably the second initiator (Ini2 ) has at a given temperature Ti a half -life time ti / 2that is at least three times, advantageously four times, more advantageously five times, still more advantageously six times of the half -life time ti / 2of the first initiator ( Inil).

[0085] Preferably the temperature Ti is between 20°C and 160 °C, more preferably between 40 °C and 140 °C and advantageously between 50 °C and 130 °C.

[0086] More preferably, the first initiator ( Inil) has a half -life time ti / 2 of 1 hour at a temperature between 40 °C and 90 °C, still more preferably between 45°C and 80 °C and even more preferably between 50°C and 75°C.

[0087] More preferably, the second initiator ( Ini2 ) has a half - life time ti / 2 of 1 hour at a temperature of at least 70 ° C, still more preferably of at least 75 ° C.

[0088] More preferably, the second initiator ( Ini2 ) has a half - life time ti / 2 of 1 hour at a temperature between 70 ° C and 150 ° C, still more preferably between 75 ° C and 140 ° C and even more preferably between 75 ° C and 130 ° C.

[0089] Preferably the dif ference of the temperature for a given half life time between the initiator ( Ini2 ) and ( Inil ) is at least 5K. This means if for a half time ti / 2of Ihour the temperature of ( Ini l ) is 75 ° C, that the temperature of ( Ini2 ) for a half time ti / 2of Ihour is at least 80 ° C.

[0090] Preferably the dif ference of the temperature for a given half life time between the initiator ( Ini2 ) and ( Ini l ) is at most 50K. This means if for a half time ti / 2of Ihour the temperature of Inil is 50 ° C, that the temperature of Ini2 for a half time ti / 2of Ihour is at most 100 ° C.

[0091] More preferably the dif ference of the temperature for a given half time life between the initiator ( Ini2 ) and ( Ini l ) is between 5K and 50K and more preferably between 6K and 40K and even more preferably between 7K and 30K.

[0092] The initiators ( Ini2 ) and ( Ini l ) are chosen from diisobutyryl peroxide, cumyl peroxyneodecanoate, di ( 3 -methoxybutyl ) peroxydicarbonate, 1, 1, 3, 3 -Tetramethylbutyl peroxyneodecanoate, cumyl peroxyneoheptanoate, di -n-propyl peroxydicarbonate, tert - amyl peroxyneodecanoate,, di - sec-butyl peroxydicarbonate, diisopropyl peroxydicarbonate, di ( 4 - tert -butylcyclohexyl ) peroxydicarbonate, di - ( 2 - ethylhexyl ) -peroxydicarbonate, tert -butyl peroxyneodecanoate, di -n-butyl peroxydicarbonate, dicetyl peroxydicarbonate, dimyristyl peroxydicarbonate, 1, 1, 3, 3 -tetramethylbutylperoxypivalate, tert -butyl peroxyneoheptanoate, tert - amyl peroxypivalate, tert -butyl peroxypivalate, di - ( 3, 5, 5 -trimethylhexanoyl ) -peroxide, dilauroyl peroxide, didecanoyl peroxide, 2, 5 -dimethyl - 2, 5 -di ( 2 - ethylhexanoylperoxy) -hexane, 1, 1, 3, 3 - tetramethylbutyl peroxy- 2 - ethylhexanoate, tert - amyl peroxy- 2 - ethylhexanoate, dibenzoyl peroxide, tert -butyl peroxy- 2 -ethylhexanoate, tert -butyl peroxydiethylacetate, tert -butylperoxyisobutyrate, 1, 1 -di - ( tert -butylperoxy) - 3, 3, 5 -trimethyl cyclohexane, 1, 1 -di ( tert - amylperoxy) cyclohexane, 1, 1 -di - ( tert -butylperoxy) - cyclohexane, tert -amyl peroxy- 2 -ethylhexylcarbonate,, tert - amyl peroxyacetate, tert -butyl peroxy-3, 5, 5 - trimethylhexanoate, 2, 2 -di - ( tert -butylperoxy) -butane, tert -butyl peroxyisopropylcarbonate, tert -butyl peroxy- 2 -ethylhexylcarbonate, tert - amyl peroxybenzoate, tert -butyl peroxyacetate, butyl 4, 4 -di ( tert -butylperoxy) valerate, tert -butyl peroxybenzoate, di -tert - amylperoxide, dicumyl peroxide, di - ( 2 -tert -butyl -peroxyisopropyl ) -benzene, 2, 5 -dimethyl - 2, 5 -di - ( tert -butylperoxy) -hexane, tert -butylcumyl peroxide, 2, 5 -dimethyl - 2, 5 -di ( tert -butylperoxy) hexyne - 3, di - tert -butyl peroxide, 3, 6, 9 -triethyl - 3, 6, 9 - trimethyl - 1, 4, 7 - triperoxonane,,, 2, 2 ' - azobis -isobutyronitrile (AIBN), 2, 2' - azodi - ( 2 -methylbutyronitrile ), azobisisobutyramide, 2, 2 ' - azobis ( 2, 4 -dimethylvaleronitrile ), 1, 1 ' -Azodi (hexahydrobenzonitrile ), or 4, 4 ' - azobis ( 4 - cyanopentanoic ).

[0093] Preferably the initiator ( Ini l ) is chosen from cumyl peroxyneodecanoate, di ( 3 -methoxybutyl ) peroxydicarbonate, 1, 1, 3, 3 -tetramethylbutyl peroxyneodecanoate, cumyl peroxyneoheptanoate, di -n-propyl peroxydicarbonate, tert - amyl peroxyneodecanoate, di - sec -butyl peroxydicarbonate, diisopropyl peroxydicarbonate, di ( 4 - tert -butylcyclohexyl ) peroxydicarbonate, di - ( 2 - ethylhexyl ) -peroxydicarbonate, tert -butyl peroxyneodecanoate, di -n-butyl peroxydicarbonate, dicetyl peroxydicarbonate, dimyristyl peroxydi carbonate, 1, 1, 3, 3 - tetramethylbutylperoxypivalate, tert -butyl peroxyneoheptanoate, tert - amyl peroxypivalate, tert -butyl peroxypivalate, di - ( 3, 5, 5 - trimethylhexanoyl ) -peroxide, dilauroyl peroxide, didecanoyl peroxide, 2, 5 -dimethyl -2, 5 -di ( 2 -ethylhexanoylperoxy) -hexane or 1, 1, 3, 3 - tetramethylbutyl peroxy- 2 -ethylhexanoate.

[0094] Preferably the initiator ( Ini2 ) is chosen from tert - amyl peroxypivalate, tert -butyl peroxypivalate, di - ( 3, 5, 5 -trimethylhexanoyl ) -peroxide, dilauroyl peroxide, didecanoyl peroxide, 2, 5 -dimethyl - 2, 5 -di ( 2 - ethylhexanoylperoxy) -hexane, 1, 1, 3, 3 - tetramethylbutyl peroxy- 2 - ethylhexanoate, tert - amyl peroxy- 2 - ethylhexanoate, dibenzoyl peroxide, tert -butyl peroxy- 2 -ethylhexanoate,, tert -butyl peroxydiethylacetate, tert -butylperoxyisobutyrate, 1, 1 -di - ( tert -butylperoxy) - 3, 3, 5 -trimethyl cyclohexane, 1, 1 -di ( tert - amylperoxy) cyclohexane, 1, 1 -di - ( tert -butylperoxy) - cyclohexane, tert -amyl peroxy- 2 -ethylhexylcarbonate, tert - amyl peroxyacetate, tert -butyl peroxy-3, 5, 5 - trimethylhexanoate, 2, 2 -di - ( tert -butylperoxy) -butane, tert -butyl peroxyisopropylcarbonate, tert -butyl peroxy- 2 -ethylhexylcarbonate, tert - amyl peroxybenzoate, tert -butyl peroxyacetate, butyl 4, 4 -di (tert -butylperoxy) valerate, tert -butyl peroxybenzoate, di - tert - amylperoxide, dicumyl peroxide, di - (2 - tert -butyl -peroxyisopropyl ) -benzene, 2, 5 -dimethyl - 2, 5 -di - ( tert -butylperoxy) -hexane, tert -butylcumyl peroxide, 2, 5 -dimethyl - 2, 5 -di ( tert -butylperoxy) hexyne - 3, di - tert -butyl peroxide or 3, 6, 9 -triethyl - 3, 6, 9 -trimethyl - l, 4, 7 - triperoxonane.

[0095] I f two initiators are present in the liquid composition (LC1 ), the weight ratio between the two initiators ( Ini2 ) and ( Ini l ) is between 1 / 10 and 10 / 1, preferably between 1 / 5 and 5 / 1 and more preferably between 1 / 4 and 4 / 1.

[0096] Preferably the initiator ( Inil ) is chosen from peroxydicarbonates. Preferably the initiator ( Ini l ) has a maximal storage temperature of 20 ° C or less.

[0097] More preferably the initiator ( Ini l ) has following general formula ( 1 ):

[0098] wherein Ri and R2 each present and alkyl group, that could be linear, branched or cyclic, or a combination of the three, having at least 6 carbon atoms, preferably 8 carbon atoms and more preferably at least 10 carbon atoms. Advantageously the groups Ri and R2 each have between 10 and 30 carbon atoms and more advantageously between 10 and 20 carbon atoms. The groups Ri and R2 can be different or identical.

[0099] In a first preferred embodiment the initiator ( Inil) is chosen from di (4 -tert -butylcyclohexyl ) peroxydicarbonate, dicetyl peroxydicarbonate and dimyristyl peroxydicarbonate.

[0100] Even more preferably, if two initiators are present in the liquid composition (LC1), the initiator (Inil) is chosen from di (4 -tert -butylcyclohexyl ) peroxydicarbonate, dicetyl peroxydicarbonate and dimyristyl peroxydicarbonate and initiator (Ini2) is chosen from benzoyl peroxide, t-butylperoxy 2 -ethylhexanoate, dilauroyl peroxide, 2, 5-dimethyl-2, 5-di (2 -ethylhexanoy 1 peroxy) hexane and didecanoyl peroxide.

[0101] In a first even more preferred embodiment the initiator ( Inil) is chosen from di (4 -tert-butylcyclohexyl) peroxydicarbonate.

[0102] The initiator (Ini2) in this first even more preferred embodiment is chosen from benzoyl peroxide, t-butylperoxy 2 -ethylhexanoate, dilauroyl peroxide and didecanoyl peroxide.

[0103] In a second even more preferred embodiment the initiator ( Inil) is chosen from dicetyl peroxydicarbonate.

[0104] The initiator ( Ini2) in this second even more preferred embodiment is chosen from benzoyl peroxide, t-butylperoxy 2 -ethylhexanoate, dilauroyl peroxide and didecanoyl peroxide.

[0105] In a third even more preferred embodiment the initiator ( Inil) is chosen from dimyristyl peroxydicarbonate.

[0106] The initiator ( Ini2 ) in this third even more preferred embodiment is chosen from benzoyl peroxide, t-butylperoxy 2 -ethylhexanoate, dilauroyl peroxide and didecanoyl peroxide

[0107] In order to conserve a dynamic viscosity of the liquid composition or (meth) acrylic syrup, also that it allows good impregnation of the fibrous substrate if necessary, and to conserve the thermoplastic properties of the matrix obtained after polymerization of the fibrous substrate impregnated with liquid composition (LC1), the compounds of the syrup are incorporated in the following mass percentages:

[0108] The (meth) acrylic monomer (s) (Ml) in the liquid composition (LC1) or (meth) acrylic syrup are present in proportions of between 40% and 95% by weight, preferably between 40% and 90% by weightand advantageously between 45% and 85% by weight of the composition comprising (meth) acrylic monomer (s) (Ml) and (meth) acrylic polymer (Pl) •

[0109] The (meth) acrylic polymer (s) (Pl) in the liquid composition (LC1) or (meth) acrylic syrup are present in a proportion of at least 5% by weight, preferably at least 10% and advantageously at least 15% by weight of the composition comprising (meth) acrylic monomer (s) (Ml) and (meth) acrylic polymer (Pl).

[0110] The (meth) acrylic polymer (s) (Pl) in the liquid (meth) acrylic composition are present in a proportion of not more than 50% by weight, preferably not more than 40% and advantageously not more than 30% by weight of the composition comprising (meth) acrylic monomer (s) (Ml) and (meth) acrylic polymer (Pl).

[0111] All the optional additives and fillers are added to the liquid (meth) acrylic syrup before the impregnation and or polymerization.

[0112] The liquid composition according to the invention can comprise optionally as well activator for polymerization.

[0113] The polymerization activator or accelerator is chosen from tertiary amines such as N, N-dimethyl-p-toluidine (DMPT), N, N-dihydroxyethyl -p-toluidine (DHEPT), organic-soluble transition metal catalysts or mixtures thereof.

[0114] Advantageously the liquid (meth) acrylic composition contains no metal based catalysts. No metal comprising additives as activators for catalytically accelerate the polymerization reaction are added to liquid (meth) acrylic composition according to the invention. These concerns especially tin based compounds as tin chloride.

[0115] The content of the activator with respect to the (meth) acrylic monomer (Ml) of the liquid (meth) acrylic composition is from lOOppm to 10000 ppm (by weight), preferably from 200ppm to 7000 ppm by weight and advantageously from 300ppm to 4000 ppm.

[0116] As regards the process for manufacturing the liquid composition or (meth) acrylic syrup, a first step consists in preparing a first syrup comprising the (meth) acrylic monomer (Ml) or mixture of (meth) acrylic monomers and a (meth) acrylic polymer(Pl). The initiators (Ini2) and (Inil) are then added to the syrup, in the proportions indicated above to conserve a dynamic viscosity of between 10 mPa*s and 10 000 mPa*s, at 25°C.

[0117] Preferably the (meth) acrylic polymer (Pl) is added to the (meth) acrylic monomers and solubilized.

[0118] The initiator ( Inil) is added or initiators ( Ini2 ) and (Inil) can be added together or apart one after the other. If added apart the order is not of importance.

[0119] Preferably the initiator ( Inil) or initiators ( Ini2 ) and ( Inil) are added at a temperature Tadd below 50 °C, more preferably below 40 °C, advantageously below 30 °C and more advantageously below 25°C.

[0120] The liquid composition according to the invention, detailed in previous paragraphs, can be used for impregnating fibres or fibrous substrate or for manufacturing thermoplastic parts or manufacturing composite parts, especially for preparing thermoplastic composites by filament winding, preferably the thermoplastic composite is a hollow body, and more preferably an axisymmetric hollow body.

[0121] As regards the fibers or fibrous substrate, mention may be made of several fibres, uni directional rovings or continuous filament mat, fabrics, felts or nonwovens that may be in the form of strips, laps, braids, locks or pieces. The fibrous material may have various forms and dimensions, either one-dimensional, two-dimensional or three-dimensional. A fibrous substrate comprises an assembly of one or more fibres. When the fibres are continuous, their assembly forms fabrics.

[0122] The one-dimensional form corresponds to linear long fibres. The fibres may be discontinuous or continuous. The fibres may be arranged randomly or parallel to each other, in the form of a continuous filament. A fibre is defined by its aspect ratio, which is the ratio between the length and diameter of the fibre. The fibres used in the present invention are long fibres or continuous fibres. The fibres have an aspect ratio of at least 1000, preferably at least 1500, more preferably at least 2000, advantageously atleast 3000 and more advantageously at least 5000, even more advantageously at least 6000, more advantageously still at least 7500 and most advantageously at least 10 000.

[0123] The two-dimensional form corresponds to nonwoven or woven fibrous mats or reinforcements or bundles of fibres, which may also be braided. Even if the two-dimensional form has a certain thickness and consequently in principle a third dimension, it is considered as two-dimensional according to the present invention.

[0124] The origins of the fibrous material may be natural or synthetic. As natural material one can mention plant fibres, wood fibres, animal fibres or mineral fibres.

[0125] Natural fibres are, for example, sisal, jute, hemp, flax, cotton, coconut fibres, and banana fibres. Animal fibres are, for example, wool or hair.

[0126] As synthetic material, mention may be made of polymeric fibres chosen from fibres of thermosetting polymers, of thermoplastic polymers or mixtures thereof.

[0127] The polymeric fibres may consist of polyamide (aliphatic or aromatic), polyester, polyvinyl alcohol, polyolefins, polyurethanes, polyvinyl chloride, polyethylene, unsaturated polyesters, epoxy resins and vinyl esters.

[0128] The mineral fibres may also be chosen from glass fibres, especially of E, R or S2 type, carbon fibres, boron fibres, basalt fibres or silica fibres.

[0129] The fibrous substrate of the present invention is chosen from plant fibres, wood fibres, animal fibres, mineral fibres, synthetic polymeric fibres, glass fibres and carbon fibres, and mixtures thereof.

[0130] Preferably, the fibrous substrate is chosen from mineral fibres.

[0131] The fibres of the fibrous substrate have a diameter between 0.005 pm and 100 pm, preferably between 1 pm and 50 pm, more preferably between 5 pm and 30 pm and advantageously between 10 pm and 25 pm.

[0132] Preferably, the fibres of the fibrous substrate of the present invention are chosen from continuous fibres (meaning that the aspect ratio does not necessarily apply as for long fibres) forthe one-dimensional form, or for long or continuous fibres for the two-dimensional or three-dimensional form of the fibrous substrate.

[0133] According to another additional aspect, the invention relates to a polymeric composite material comprising a thermoplastic (meth) acrylic matrix and a fibrous substrate used as reinforcement, in which the fibrous substrate consists of long fibres, said composite material being characterized in that the thermoplastic (meth) acrylic matrix is obtained after polymerization of said fibrous substrate impregnated with said liquid composition (LC1) according to the invention.

[0134] Another aspect of the present invention is a process for manufacturing thermoplastic composites by filament winding, preferably the thermoplastic composite is a hollow body, and more preferably an axisymmetric hollow body composite parts by a process comprising the following steps:i) impregnating fibers or fibrous substrate with the liquid composition (LC1),ii) polymerizing at least a part of the liquid composition (LC1) during winding on a mandrel.

[0135] The process can comprise an additional heating step.

[0136] To polymerize at least a part of the liquid composition (LC1) means a part the (meth) acrylic monomer (Ml) of the liquid composition (LC1) is polymerized, meaning that the conversion of the monomer of the liquid composition (LC1) is at least 10%, preferably at least 15%.

[0137] The at least partly polymerization of the liquid composition (LC1) that has impregnated the fibers or fibrous substrate during the process for manufacturing during step ii), takes place at temperature between 40 °C and 140 °C, preferably between 50 °C and 130 °C. In a first preferred embodiment the temperature is between 50°C and 100 °C, in a second preferred embodiment the temperature is between 60 °C and 100 °C and in a third preferred embodiment the temperature is between 60 °C and 110 °C. The polymerization step ii) is more or less isotherm. By isotherm is meant in the present invention that the temperature during polymerization is kept in aninterval of ΔT of 30K, preferably 20K of the polymerization temperature and comprises no temperature ramps, where the temperature is for example decreased during polymerization or increased at the end and the difference of temperature during polymerization is more than 30K. For example the impregnated the fibrous substrate is heated up to 70 °C on the mandrel and the temperature at the end does not exceed 90°C. Or for example the impregnated the fibrous substrate is heated up to 70°C and the temperature during the at least polymerization step stays inside an interval of 20K: between 60°C and 80 °C or also between 65°C and 85°C.

[0138] Advantageously the temperature during polymerization is kept in an interval of ΔT of 28K, more advantageously of 26K, even more advantageously of 24K, still more advantageously of 22K and most advantageously of 20K.

[0139] As regards the system ( 1) for preparing thermoplastic composites by filament winding that comprises fiber spool (s) ( 10 ), impregnation means (20 ) for impregnating the fibers ( 15) with liquid composition (LC1), a mandrel (30 ), heating means (40 ), and optionally temperature controlling means (50 ).

[0140] Preferably the system one fiber spool or several fiber spools. There could be from one fiber spool up to 100 fiber spools. Usually the system ( 1) comprises between 1 and 50 spools.

[0141] In a first preferred embodiment the system ( 1) comprises between 1 and 40 spools. In a second preferred embodiment the system ( 1) comprises between 2 and 40 spools.

[0142] The impregnation means (20 ) of the system ( 1) comprises for example a bath or a die or impregnation head.

[0143] The heating means (40) the system ( 1) is preferably chosen from infrared heating means.

[0144] The optional temperature controlling means (50 ) of the system ( 1) is preferably a temperature sensor.

[0145] As regards the process step (105) for providing fibers or fibrous material, it can be done for example by means a fiber spool ( 10 ). There could be one fiber spool or several fiber spools. Forexample, two fiber spools ( 10 ) are shown in the system ( 1) of figure 2.

[0146] There could be from one fiber spool up to 100 fiber spools. Usually there are between 1 and 50 spools.

[0147] In a first preferred embodiment there are between 1 and 40 spools.

[0148] In a second preferred embodiment there are between 2 and 40 spools.

[0149] As regards the process step (110) for providing the liquid composition (LC1), it can be done for example by means of a conduct. Said conduct delivers the liquid composition (LC1) to the impregnation means, which is for example a bath (20 ) in the system ( 1) of figure 2.

[0150] As regards the process step (120) for impregnating the fibres or fibrous substrate, it comprises a step of impregnating the fibrous substrate with the liquid composition (LC1).

[0151] This impregnation step ( 120 ) take place with the help of impregnation means (20 ). It for example can take place in a bath or a die or impregnation head.

[0152] If the viscosity of the liquid composition (LC1) at a given temperature is slightly too high for the impregnation process, it is possible to heat the syrup so as to have a more liquid syrup for sufficient wetting and correct and complete impregnation of the fibrous substrate.

[0153] As regards the process step (130) of winding the impregnated fibrous material around a mandrel, said winding being carried out for a winding duration ti, and a at least partly polymerization of the liquid composition (LC1) takes place during winding on a mandrel. The winding duration ti could be from 5min up to several hours. This duration ti depends on the thickness and the size of the thermoplastic composite.

[0154] Preferably the winding takes place for a winding duration ti in order to obtain a thickness between 1mm and 100mm of the thermoplastic composite. Preferably the thickness is between 1 and100mm. In a first more preferred embodiment, the thickness is between 5mm and 100mm. In a second more preferred embodiment the thickness is between 10mm and 100mm. In a third more preferred embodiment the thickness is between 10mm and 80mm. In a fourth more preferred embodiment the thickness is between 20mm and 80mm.

[0155] The winding takes place layer by layer around the mandril until achieving the aimed for thickness.

[0156] As regards the process step (140) of heating the wound fibrous material at a temperature Th, said heating being carried out for a heating duration t2to polymerize a part the (meth) acrylic monomer (Ml) of the liquid composition (LC1). The temperature Thcorresponds also to the polymerization temperature. The heating duration t2is in the same range as the winding duration t2or longer. By longer is meant that once the winding is finished when the final thickness has been achieved, the surface of the impregnated fibrous material around a mandrel is still heated.

[0157] The heating duration t2could be from 5min up to several hours.

[0158] The heating of the heating step (140 ) is made by heating means (40 ). Preferably the heating means (40 ) is chosen from infrared heating means.

[0159] The distance di between the heating means (40 ) and the surface (60 ) of the mandrel or the upper most zone is at least 10mm. The distance di is between 10 mm and 500 mm and depends also on the power of the heating means (40 ). Usually the distance di is between 10 mm and 500 mm. Preferably the distance di is between 20mm and 300mm.

[0160] The temperature Th is chosen on function of the initiator (Inil). The temperature Th is preferably above the temperature half-life time t1 / 2of 10 hours of initiator (Ini1). The temperature Th is preferably below the temperature half-life time t1 / 2of 0.1 hours of initiator (Ini1).

[0161] In a first preferred embodiment the temperature Th is between the temperature half-life time t1 / 2of 10 hours of initiator (Ini1) and the temperature half-life time t1 / 2of 0.1 hours of initiator (Ini1).

[0162] In a second preferred embodiment the temperature Th is above the temperature half-life time t1 / 2of 1 hours of initiator (Ini1).

[0163] In a third preferred embodiment the temperature Th is between 10 °C under the temperature half-life time t1 / 2of 1 hours of initiator (Ini1) and 15°C above the temperature half-life time t1 / 2of 1 hours of initiator (Ini1).

[0164] The partly polymerization of the liquid composition (LC1) that has impregnated the fibers or fibrous substrate due to the heating step (140 ) takes place at temperature Th between 40 °C and 140 °C, preferably between 50°C and 130 °C. In a first preferred embodiment the temperature Th is between 50 °C and 100 °C, in a second preferred embodiment the temperature Th is between 60 °C and 100 °C and in a third preferred embodiment the temperature Th is between 60°C and 110 °C. The polymerization is more or less isotherm. By isotherm is meant in the present invention that the temperature Th during polymerization is kept in an interval of ΔT of 30K preferably 20K of the polymerization temperature and comprises no temperature ramps, where the temperature is for example decreased during polymerization or increased at the end and the difference of temperature during polymerization is more than 30K. For example the impregnated the fibrous substrate is heated up to 70 °C on the mandrel and the temperature at the end does not exceed 90 °C. Or for example the impregnated the fibrous substrate is heated up to 70 °C and the temperature during the at least polymerization step stays inside an interval of 20K: between 60 °C and 80 °C or also between 65°C and 85°C.

[0165] Advantageously the temperature Th during polymerization is kept in an interval of ΔT of 28K, more advantageously of 26K, even more advantageously of 24K, still more advantageously of 22K and most advantageously of 20K.

[0166] To polymerize a part the (meth) acrylic monomer (Ml) of the liquid composition (LC1) means that the conversion of the monomer (Ml) of the liquid composition (LC1) that has impregnated the fibrous material is at least 10%, preferably at least 15%. This ratio of conversion applies to monomer (Ml) of the overall manufactured hollow body.

[0167] In a first preferred embodiment the conversion of the monomer (Ml) of the liquid composition (LC1) is at least 20%.

[0168] In a second preferred embodiment the conversion of the monomer (Ml) of the liquid composition (LC1) is at least 30%.

[0169] In a third preferred embodiment the conversion of the monomer (Ml) of the liquid composition (LC1) is at least 40%.

[0170] In a fourth preferred embodiment the conversion of the monomer (Ml) of the liquid composition (LC1) is at least 50%.

[0171] In a fifth preferred embodiment the conversion of the monomer (Ml) of the liquid composition (LC1) is at least 60%.

[0172] In a sixth preferred embodiment the conversion of the monomer (Ml) of the liquid composition (LC1) is at least 70%.

[0173] In a seventh preferred embodiment the conversion of the monomer (Ml) of the liquid composition (LC1) is at least 80%.

[0174] In a eighth preferred embodiment the conversion of the monomer (Ml) of the liquid composition (LC1) is at least 90%.

[0175] In a tenth preferred embodiment the conversion of the monomer (Ml) of the liquid composition (LC1) is at least 95%.

[0176] In an eleventh preferred embodiment the conversion of the monomer (Ml) of the liquid composition (LC1) is at least 99%.

[0177] As said before the winding takes place layer by layer around the mandril until achieving the aimed for thickness, so it could be the depending on the respective layer that the conversion of the monomer (Ml) is different. For instance, in a more outer layer the conversion can be less as this layer was heated a shorter time than a more inner layer that was longer exposed to the heating means. There could be a gradient of conversion throughout the thickness of the wounded partly polymerized composite material.

[0178] Preferably the winding step ( 130) and the heating step ( 140) take place at least partly parallel. The heating could begin before the winding on the mandril or begin at the same time as the winding or could begin after the first wound fibrous material is already present on the mandril. The heating could also be stopped shortly before the winding is finished. The heating could also be continued after the winding is finished and the aimed thickness obtained.

[0179] As regards the optional process step (150) of controlling the temperature Th on the surface (60 ) of the mandrel, said controlling takes place by using temperature controlling means (50 ) as for example a temperature sensor.

[0180] By on surface (60 ) of the mandrel, is meant the upper most zone. At the very beginning of the winding step ( 130 ) it is mostly the mandrel itself as the wound fibrous material does not cover the whole mandrel yet. This is for example the case in figure 2, where only a part of the mandrel is covered by the impregnated fibrous material. As the winding continues the wound fibrous material does cover the whole mandrel and the thickness increase layer by layer and the upper most zone are then the outermost layers of the wound fibrous material.

[0181] The controlling is required if it is not given that the temperature Th stays inside the upper and lower limits for the temperature as defined before.

[0182] As regards the optional process step (160) of adapting, this step is only made, if during the controlling step ( 150 ) the temperature Th should not stay inside the upper and lower limits as defined before.

[0183] The adapting can be done either by changing the rotating speed vrof the mandril during the winding step ( 130) or changing the distance di between the heating means (40 ) and surface (60 ) of the mandrel or by changing the power of the heating means (40 ).

[0184] If the temperature Th should become too low, either the rotating speed vrof the mandril during the winding step ( 130 ) is lowered as well or the distance di between the heating means (40 ) and surface (60 ) of the mandrel is decreased or by the power of the heating means (40 ) is increased.

[0185] If the temperature Th should become too high, either the rotating speed vrof the mandril during the winding step ( 130 ) is increased as well or the distance di between the heating means (40 ) and surface (60 ) of the mandrel is increased or by the power of the heating means (40 ) is reduced.

[0186] The adapting can also be done by a combination of two or more of the just describes possibilities.

[0187] In a f irst preferred embodiment the adapting is that the rotating speed vrof the mandril is changed during the winding step ( 130 ).

[0188] In a second preferred embodiment the adapting is that the distance di between the heating means ( 40 ) and surface ( 60 ) of the mandrel or most upper zone is changed.

[0189] In a third preferred embodiment the adapting is that the power of the heating means ( 40 ) is changed.

[0190] As regards the optional process step (170) of curing, this step is only made, if the conversion of the monomer (Ml ) is not suf f icient high. This takes place if the conversion of the monomer (Ml ) is less than 90 %.

[0191] In a f irst preferred embodiment the curing step ( 170 ) takes place if the conversion of the monomer (Ml ) is less than 95%.

[0192] In a second preferred embodiment the curing step ( 170 ) takes place if the conversion of the monomer (Ml ) is less than 98 %.

[0193] second preferred embodiment the curing step ( 170 ) takes place if the conversion of the monomer (Ml ) is less than 99%.

[0194] The curing ( 170 ) can for example take place in an oven.

[0195] The temperature Tcduring the curing step ( 170 ) is higher that the temperature Th during the heating step ( 140 ).

[0196] The curing step ( 170 ) takes place at temperature Tcbetween 60 ° C and 145 ° C, preferably between 60 ° C and 135 ° C. In a f irst preferred embodiment the temperature Tcis between 60 ° C and 110 ° C, in a second preferred embodiment the temperature Tcis between 65 ° C and 105 ° C and in a third preferred embodiment the temperature Tcis between 70 ° C and 110 ° C.

[0197] Preferably the curing step ( 170 ) takes place if at least two initiators ( Ini l ) and ( Ini2 ) are present in the liquid composition (LC1).

[0198] More preferably the curing step ( 170 ) takes place if the initiator ( Ini2 ) has at a given temperature Ti a half-life time t1 / 2that is higher than the one of the first initiator (Ini1) present in the liquid composition (LC1).

[0199] Still more preferably the curing step ( 170 ) takes place if the second initiator ( Ini2 ) has at a given temperature Ti a half -life time ti / 2that is at least two times of the half - life time ti / 2of the f irst initiator ( Ini l ).

[0200] A first preferred method ( 100 ) for manufacturing thermoplastic composite comprises the steps of impregnating ( 120 ), winding ( 130 ) and heating ( 140 ).

[0201] A second preferred method ( 100 ) for manufacturing thermoplastic comprises the steps of providing ( 105 ) f ibers, providing ( 110 ) the liquid composition (LC1 ), impregnating ( 120 ), winding ( 130 ) and heating ( 140 ).

[0202] A third preferred method ( 100 ) for manufacturing thermoplastic composites comprises the steps of providing ( 105 ) f ibers, providing ( 110 ) the liquid composition (LC1 ), impregnating ( 120 ), winding ( 130 ) and heating ( 140 ).

[0203] A fourth preferred method ( 100 ) for manufacturing thermoplastic composites comprises the steps of providing ( 105 ) f ibers, providing ( 110 ) the liquid composition (LC1 ), impregnating ( 120 ), winding ( 130 ), heating ( 140 ) and curing ( 170 ).

[0204] A fifth preferred method ( 100 ) for manufacturing thermoplastic composites comprises the steps of providing ( 105 ) fibers, providing ( 110 ) the liquid composition (LC1 ), impregnating ( 120 ), winding ( 130 ), heating ( 140 ), controlling( 150 ) and curing ( 170 ).

[0205] A sixth preferred method ( 100 ) for manufacturing thermoplastic composites comprises the steps of providing ( 105 ) fibers, providing ( 110 ) the liquid composition (LC1 ), impregnating ( 120 ), winding ( 130 ), heating ( 140 ), controlling( 150 ), adapting ( 160 ) and curing ( 170 ).

[0206] A seventh preferred method ( 100 ) for manufacturing thermoplastic composites comprises the steps of providing ( 105 ) f ibers, providing ( 110 ) the liquid composition (LC1 ), impregnating ( 120 ), winding ( 130 ), heating ( 140 ), controlling ( 150 ) and adapting ( 160 ).

[0207] After the process or method ( 100 ) for manufacturing a thermoplastic composite, but also mechanical or structured parts or products, there can additionally be the step of post forming. Thepost forming includes bending, compressing as changing the form of the composite part.

[0208] As regards the use of the mechanical parts made of composite material thus manufactured, mention may be made of sport applications, energy applications, transport applications, notably transport of liquids and gases, storage application, notably storage of liquids and gases applications.

[0209] The invention relates as well to an obj ect obtained with liquid composition or by process or method ( 100 ).

[0210] The obj ect is a mechanical part made of composite material or comprising composite material.

[0211] The mechanical part made of composite material is especially a shaft, a tube, pipe or a vessel.

[0212] In a first preferred embodiment the mechanical part made of composite material is especially a material for storage vessel.

[0213] In a second preferred embodiment the mechanical part made of composite material is especially a high pressure storage vessel.Description of Figures

[0214] Figure 1 represents a flowchart of the method ( 100) according to an embodiment of the invention. It includes the optional steps surrounded by dashed lines and the essential steps surrounded by full lines.

[0215] Figure 2 represents a schematic view of an embodiment of the system ( 1), including fiber spools (10 ), fibers (15), impregnation means (20 ), a mandrel (30 ), heating means (40 ) and temperature controlling means (50 ). In figure 2 the winding step (130 ) has just begun as the surface (60 ) of mandrel (30 ) is not even completely covered with the impregnated the fibers (25). The mandrel rotates with a rotating speed vrand furthermore the distance di is shown between the heating means (40 ) and the surface (60 ).[Methods]

[0216] Conversion of methyl methacrylate as (Ml) is measured by gas chromatography. A sample is cut from the obtained obj ect, weighted and extracted. The extraction takes place with THF. The ratio of monomer is measured from the extracted solution of the sample by gas chromatography.

[0217] The weight-average molecular weight may be measured by size exclusion chromatography (SEC). The chromatography column is calibrated with PMMA standards having a molecular weight between 402g / mol and 1 900 000 g / mol. The average molecular weight is expressed in g / mol for the number and average molecular weight Mn and Mw respectively. For the measurement, the concentration is lg / L.

[0218] The viscosity of the liquid composition comprising at least the components a) and b) is measured with a Brookfield viscosimeter at 23 °C, according to ISO 2555: 2018 " Plastics — Resins in the liquid state or as emulsions or dispersions — Determination of apparent viscosity using a single cylinder type rotational viscometer method".

[0219] The porosity and delamination in the obj ect are both evaluated by tomography. X ray based tomography is used.[Examples]

[0220] First step: preparation of a liquid composition (LC1)

[0221] A liquid composition is prepared by dissolving 20% by weight of the PMMA (BS520, a copolymer of MMA comprising ethyl acrylate as comonomer) as (Pl) in 80% by weight of methyl methacrylate as (Ml), which is stabilized with HQME (hydroquinone monomethyl ether).

[0222] To this liquid composition are added different initiators (Inil) only or mixtures of two different initiators (Inil) and (Ini2). As initiators ( Inil) or ( Ini2 ) are used di (4 -tert-butylcyclohexyl ) peroxydicarbonate (P16 - Perkadox® 16 from the company Akzo Nobel) and benzoyl peroxide (BPO - Perkadox® CH50X from the company Akzo Nobel.

[0223] Second step: partly polymerization of a liquid composition by filament winding.

[0224] Carbon fibers coming from spools were impregnated in a bath comprising the liquid composition prepared in step 1 and wound ona mandrel. For the exemplified process during the winding an infrared source heated the to 65°C to start polymerization. For a comparative process no heating was applied during the winding. After 1 hour the obtained wounded composites was recovered.

[0225] Third step: curing - The recovered obj ects was put in an oven at 80°C for 2 hours.

[0226] The obtained obj ects were evaluated for porosity and delamination with the aid of tomography. The symbol: -- signifies elevated relative presence of that characteristic. The symbol: oo signifies intermediate presence of that characteristic. The symbol: ++ signifies low presence of that characteristic.[Tableau 1]

[0227] Table 1 compositions and results at 110 °C

[0228] The heating during the winding which yields to polymerization reduces significantly the porosity and the delamination of the obtained obj ect. Comparative example 1 has a higher porosity and delamination.

Claims

CLAIMS1. A liquid composition (LC1 ) suitable for preparing thermoplastic composites by f ilament winding, preferably the thermoplastic composite is a hollow body, and more preferably an axisymmetric hollow body, said composition comprises:a) a (meth) acrylic polymer ( Pl ),b) a (meth) acrylic monomer (Ml ), andc ) at least one initiator ( Ini l ),said liquid composition (LC1 ) is having a dynamic viscosity of between 10 mPa* s and 10 000 mPa* s at 25 ° C.

2. The liquid composition (LC1) according to claim 1, characterized in that composition comprises at least two initiators ( Ini l ) and ( Ini2 ).

3. The liquid composition (LC1) as claimed in claim 1 or 2, characterized that the quantity of at least one initiator ( Ini l ) or the quantity of the at least two initiators ( Ini l ) and ( Ini2 ) together in the composition is between 0. Iphr and 15phr relative to the sum of (meth) acrylic monomer (Ml ) and (meth) acrylic polymer ( Pl ).

4. The liquid composition (LC1 ) according to claim 2 or 3, characterized in that the initiator ( Ini l ) or two initiators ( Ini l ) and ( Ini2 ) have at any given temperature T1 dif ferent half - life times ti / 2.

5. The liquid composition according to any of claims 1 to 4, characterized in that the initiator ( Ini l ) or two initiators ( Ini l ) and ( Ini2 ) are chosen from diacyl peroxides, peroxy esters, peroxydicarbonates, dialkyl peroxides, peroxyacetals, hydroperoxide or peroxyketale.

6. The liquid composition according to any of claims 1 to 5, characterized in that the initiator ( Ini l ) or the two initiators( Ini l ) and ( Ini2 ) are chosen from diisobutyryl peroxide, cumyl peroxyneodecanoate, di ( 3 -methoxybutyl ) peroxydicarbonate, 1, 1, 3, 3 -Tetramethylbutyl peroxyneodecanoate, cumyl peroxyneoheptanoate, di -n-propyl peroxydicarbonate, tert - amyl peroxyneodecanoate,, di - sec -butyl peroxydicarbonate, diisopropyl peroxydicarbonate, di ( 4 - tert -butylcyclohexyl ) peroxydicarbonate, di - ( 2 - ethylhexyl ) -peroxydicarbonate, tert butyl peroxyneodecanoate, di -n-butyl peroxydicarbonate, dicetyl peroxydicarbonate, dimyristyl peroxydicarbonate, 1, 1, 3, 3 - tetramethylbutylperoxypivalate, tert -butyl peroxyneoheptanoate, tert - amyl peroxypivalate, tert -butyl peroxypivalate, di - ( 3, 5, 5 - trimethylhexanoyl ) -peroxide, dilauroyl peroxide, didecanoyl peroxide, 2, 5 -dimethyl - 2, 5 -di (2 - ethylhexanoylperoxy) -hexane, 1, 1, 3, 3 - tetramethylbutyl peroxy- 2 -ethylhexanoate, tert - amyl peroxy- 2 - ethylhexanoate, dibenzoyl peroxide, tert -butyl peroxy- 2 - ethylhexanoate, tert -butyl peroxydiethylacetate, tert -butyl peroxyisobutyrate, 1, 1 -di - ( tert -butylperoxy) - 3, 3, 5 - trimethylcyclohexane, 1, 1 -di ( tert amylperoxy) cyclohexane, 1, 1 -di - (tert -butylperoxy) - cyclohexane, tert -amyl peroxy- 2 - ethylhexylcarbonate,, tert amyl peroxyacetate, tert -butyl peroxy- 3, 5, 5 - trimethylhexanoate, 2, 2 -di - ( tert -butylperoxy) -butane, tert -butyl peroxyisopropylcarbonate, tert -butyl peroxy- 2 - ethylhexylcarbonate, tert - amyl peroxybenzoate, tert -butyl peroxyacetate, butyl 4, 4 -di (tert -butylperoxy) valerate, tert butyl peroxybenzoate, di - tert - amylperoxide, dicumyl peroxide, di - ( 2 - tert -butyl -peroxy isopropyl ) -benzene, 2, 5 -dimethyl - 2, 5 - di - ( tert -butylperoxy) -hexane, tert -butylcumyl peroxide, 2, 5 - dimethyl - 2, 5 -di ( tert -butylperoxy) hexyne - 3, di - tert -butyl peroxide, 3, 6, 9 - triethyl - 3, 6, 9 - trimethyl - 1, 4, 7 - triperoxonane, 2, 2 ' - azobisisobutyronitrile (AIBN), 2, 21- azodi - ( 2 - methylbutyronitrile ), azobisisobutyramide, 2, 2 ' -azobis ( 2, 4 - dimethylvaleronitrile ), 1, 1 ' -Azodi (hexahydrobenzonitrile ), or 4, 4 ' - azobis ( 4 - cyanopentanoic ).

7. The liquid composition according to any of claims 1 to 6, characterized in that initiator ( Inil ) is chosen from cumylperoxyneodecanoate, di ( 3 -methoxybutyl ) peroxydicarbonate, 1, 1, 3, 3 - tetramethylbutyl peroxyneodecanoate, cumyl peroxyneoheptanoate, di -n-propyl peroxydicarbonate, tert - amyl peroxyneodecanoate, di - sec -butyl peroxydicarbonate, diisopropyl peroxydicarbonate, di ( 4 - tert -butylcyclohexyl ) peroxydicarbonate, di - ( 2 - ethylhexyl ) -peroxydicarbonate, tert butyl peroxyneodecanoate, di -n-butyl peroxydicarbonate, dicetyl peroxydicarbonate, dimyristyl peroxydicarbonate, 1, 1, 3, 3 - tetramethylbutylperoxypivalate, tert -butyl peroxyneoheptanoate, tert - amyl peroxypivalate, tert -butyl peroxypivalate, di - ( 3, 5, 5 - trimethylhexanoyl ) -peroxide, dilauroyl peroxide, didecanoyl peroxide, 2, 5 -dimethyl - 2, 5 -di ( 2 - ethylhexanoylperoxy) -hexane or 1, 1, 3, 3 - tetramethylbutyl peroxy- 2 -ethylhexanoate.

8. The liquid composition according to any of claims 2 to 6, characterized in that the initiator ( Ini2 ) is chosen from tert amyl peroxypivalate, tert -butyl peroxypivalate, di - ( 3, 5, 5 - trimethylhexanoyl ) -peroxide, dilauroyl peroxide, didecanoyl peroxide, 2, 5 -dimethyl - 2, 5 -di ( 2 - ethylhexanoylperoxy) -hexane, 1, 1, 3, 3 - tetramethylbutyl peroxy- 2 - ethylhexanoate, tert - amyl peroxy- 2 - ethylhexanoate, dibenzoyl peroxide, tert -butyl peroxy- 2 -ethylhexanoate,, tert -butyl peroxydiethylacetate, tert -butyl peroxy isobutyr ate, 1, 1 -di - ( tert -butylperoxy) - 3, 3, 5 - trimethylcyclohexane, 1, 1 -di ( tert - amylperoxy) cyclohexane, 1, 1 - di - ( tert -butylperoxy) - cyclohexane, tert - amyl peroxy- 2 - ethylhexylcarbonate, tert -amyl peroxyacetate, tert -butyl peroxy- 3, 5, 5 - trimethylhexanoate, 2, 2 -di - (tert -butylperoxy) - butane, tert -butyl peroxyisopropylcarbonate, tert -butyl peroxy - 2 -ethylhexylcarbonate, tert - amyl peroxybenzoate, tert -butyl peroxyacetate, butyl 4, 4 -di ( tert -butylperoxy) valerate, tert butyl peroxybenzoate, di - tert - amylperoxide, dicumyl peroxide, di - ( 2 - tert -butyl -peroxy isopropyl ) -benzene, 2, 5 -dimethyl - 2, 5 - di - ( tert -butylperoxy) -hexane, tert -butylcumyl peroxide, 2, 5 - dimethyl - 2, 5 -di ( tert -butylperoxy) hexyne - 3, di - tert -butyl peroxide or 3, 6, 9 - triethyl - 3, 6, 9 - trimethyl - 1, 4, 7 - triperoxonane.

9. The liquid composition according to any of claims 1 to 8, characterized in that the (meth) acrylic polymer (Pl) comprises at least 50% by weight of methyl methacrylate (MMA).

10. The liquid composition according to any of claims 1 to 9, characterized in that 50% by weight of the (meth) acrylic monomer (Ml) is methyl methacrylate.

11. Use of the liquid composition according to any of claims 1 to 10 for manufacturing thermoplastic composite parts by filament winding.

12. A system ( 1) for preparing thermoplastic composites by filament winding, preferably the thermoplastic composite is a hollow body, and more preferably an axisymmetric hollow body, said system ( 1) comprises:fiber spool (s) (10 ),impregnation means (20 ) for impregnating the fibers ( 15) with liquid composition (LC1) according to any of claims 1 to 10, a mandrel (30 ),heating means (40 ), andoptionally temperature controlling means (50 ).

13. The system according to claim 12, characterized in that it comprises temperature controlling means (50 ).

14. The system according to any of claims 12 to 13, characterized in that the heating means (40) is chosen from infrared heating means.

15. A process for manufacturing a thermoplastic composite by filament winding, preferably the thermoplastic composite is a hollow body, and more preferably an axisymmetric hollow body, by a process comprising the following steps:i) impregnating fibers or fibrous substrate with the liquid composition (LC1) according to any of claims 1 to 10,ii) polymerizing at least a part of the liquid composition (LC1) during the winding on a mandrel.

16. The process according to claim 14, characterized in that the process comprises a heating step.

17. The process according to claims 14 or 15, characterized in that the conversion of the monomer (Ml) of the liquid composition (LC1) during the polymerizing step is at least 10%.

18. The process according to claim 14 or 15, characterized in that the temperature during step ii) is between 40 °C and 140 °C.

19. The process according to any of claims 15 to 17, characterized in that the temperature during step ii) is between 50 °C and 100 °C.

20. The process according to any of claims 15 to 17, characterized in that the temperature during step ii) is between 60 °C and 110 °C.

21. The process according to any of claims 15 to 20, characterized in that the temperature during step ii) is isotherm, meaning that the temperature during polymerization is kept in an interval of AT of 20K.

22. The process according to any of claims 15 or 21, characterized in that the thermoplastic composite is a hollow body, preferably an axisymmetric hollow body.

23. The process according to any of claims 15 to 21, characterized in that the process comprises an additional heating step.

24. A method ( 100 ) for manufacturing a thermoplastic composite, preferably a hollow body, more preferably an axisymmetrichollow body, comprising a layer of composite material, said process comprising the following steps:optionally a step of providing ( 105) fibers or fibrous material,optionally a step of providing ( 110) the liquid composition (LC1) according to any of claims 1 to 10;a step of impregnating ( 120) a fibrous material with the liquid composition (LC1) according to any of claims 1 to 10; a step of winding (130 ) the impregnated fibrous material around a mandrel, said winding being carried out for a winding duration t1; anda step of heating (140 ) the wound fibrous material at a temperature Th, said heating being carried out for a heating duration t2in order to polymerize a part the (meth) acrylic monomer (Ml) of the liquid composition (LC1);optionally a step of controlling ( 150 ) the temperature TH; optionally a step of adapting ( 160 ),optionally a step of curing ( 170 ).

25. The method according to claim 24, characterized in that the heating ( 140 ) is carried out with heating means (40 ), preferably the heating means (40 ) is chosen from infrared heating means.

26. The method according to claim 24, characterized in that the conversion of the monomer (Ml) of the liquid composition (LC1) that has impregnated the fibrous material is at least 10%.

27. The method according to claim 24, characterized in that the conversion of the monomer (Ml) of the liquid composition (LC1) that has impregnated the fibrous material is at least 90% 28. The method according to claim 24, characterized in that the temperature Th is between 40°C and 140 °C, preferably between 50°C and 130 °C.

29. The method according to any of claims 24 to 28, characterized in that the method ( 100 ) comprises the step of curing ( 170).

30. The method according to any of claims 24 to 28, characterized in that the method ( 100 ) comprises the step of controlling ( 150 ) the temperature.

31. The method according to any of claims 24 to 30, characterized in that the method ( 100 ) comprises the step of step of adapting ( 160 ).

32. The method according to any of claims 24 to 30, characterized in that the method ( 100 ) comprises the steps of providing ( 105 ) fibers, providing ( 110 ) the liquid composition (LC1 ), impregnating ( 120 ), winding ( 130 ), heating ( 140 ), controlling( 150 ) and curing ( 170 ).

33. The method according to any of claims 24 to 30, characterized in that the method ( 100 ) comprises the steps of providing ( 105 ) fibers, providing ( 110 ) the liquid composition (LC1 ), impregnating ( 120 ), winding ( 130 ), heating ( 140 ), controlling( 150 ), adapting ( 160 ) and curing ( 170 ).

34. The method according to any of claims 24 to 33, characterized in that the fibers are provided by means a fiber spool ( 10 ).

35. The method according to claims 34, characterized in that there are between 2 and 40 spools.

36. The method according to any of claims 24 to 35, characterized in that the winding duration t1is from 5min up to several hours.

37. The method according to any of claims 24 to 35, characterized in that the winding duration t1is chosen in order to obtain a thickness between 1mm and 100mm of the thermoplastic composite.

38. The method according to any of claims 24 to 37, characterized in that the step of heating ( 140 ) the wound fibrous material ata temperature Th is made by heating means (40 ) chosen from infrared heating means.

39. The method according to any of claims 24 to 38, characterized in that in the step of heating (140 ) the wound fibrous material at a temperature Th, the distance d1between the heating means (40 ) and the surface (60 ) of the mandrel or the upper most zone is at least 10mm.

40. The method according to any of claims 24 to 38, characterized in that in the step of heating (140 ) the wound fibrous material at a temperature Th, the distance d1between the heating means (40 ) and the surface (60 ) of the mandrel or the upper most zone is between 20mm and 300mm.

41. The method according to any of claims 24 to 40, characterized in that in the step of heating (140 ) the wound fibrous material at a temperature Th, said temperature Th is between the temperature half -life time t1 / 2of 10 hours and the temperature half -life time t1 / 2of 0. 1 hours of initiator (Ini1) of the liquid composition (LC1).

42. The method according to any of claims 24 to 40, characterized in that in the step of heating (140 ) the wound fibrous material at a temperature Th, said temperature Th is between 10 °C under the temperature half -life time t1 / 2of 1 hours of initiator ( Ini1) and 15°C above the temperature half -life time t1 / 2of 1 hours of initiator ( Ini1) of the liquid composition (LC1).

43. The method according to any of claims 24 to 42, characterized in that the temperature Th is between 40 °C and 140 °C, preferably between 50°C and 130 °C.

44. The method according to any of claims 24 to 42, characterized in that the temperature Th during the step of heating ( 140 ) the wound fibrous material is between 50°C and 100°C or between 60 °C and 100 °C or between 60 °C and 110 °C.

45. The method according to any of claims 24 to 44, characterized in that the temperature Th during polymerization is kept in an interval of ΔT of 28K, more advantageously of 26K, even more advantageously of 24K, still more advantageously of 22K and most advantageously of 20K.

46. The method according to any of claims 24 to 45 characterized in that the conversion of the monomer (Ml) of the liquid composition (LC1) that has impregnated the fibrous material is at least 10%, preferably at least 15%.

47. The method according to any of claims 24 to 45, characterized in that the conversion of the monomer (Ml) of the liquid composition (LC1) is at least 60%.

48. The method according to any of claims 24 to 47, characterized in that the step of controlling ( 150 ) the temperature Th takes place by using temperature controlling means (50 ), as for example a temperature sensor.

49. The method according to any of claims 24 to 48, characterized in that the step of adapting ( 160 ) is done either by changing the rotating speed vrof the mandril during the winding step ( 130 ) or changing the distance d1between the heating means (40) and surface (60) of the mandrel or by changing the power of the heating means (40 ).

50. The method according to any of claims 24 to 48, characterized in that the step of adapting (160 ) is done by changing the rotating speed vrof the mandril during the winding step ( 130 ).

51. The method according to any of claims 24 to 48, characterized in that the step of adapting (160 ) is done by changing the distance d1between the heating means (40 ) and surface (60) of the mandrel.

52. The method according to any of claims 24 to 48, characterized in that the step of adapting ( 160 ) is done by changing the power of the heating means ( 40 ).

53. The method according to any of claims 24 to 52, characterized in that the step of curing ( 170 ) takes place in an oven.

54. The method according to any of claims 24 to 52, characterized in that during the step of curing ( 170 ) the temperature Tcduring the curing step ( 170 ) is higher that the temperature Th during the heating step ( 140 ).

55. A mechanical part made of composite material or comprising composite material obtained via the process as claimed in claims 24 to 54.

56. The part as claimed in claim 56, said part being a shaft, a tube, pipe or a vessel or storage vessel or high pressure storage vessel.

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