Patent application title: METHOD FOR THE MANUFACTURING OF YARNS FROM RECYCLED CARBON FIBERS
Gualtiero Sepati (Palazzolo Sull'Oglio, IT)
Giacinto Cornacchia (Rotondella, IT)
Flavio Caretto (Roma, IT)
Domenico Antonio Matera (Roma, IT)
Sergio Galvagno (Roma, IT)
Sabrina Portofino (Roma, IT)
Stefano Dotti (Dalmine, IT)
AGENZIA NAZIONALE PER LE NUOVE TECNOLOGIE, L/ENERG E LO SVILUPPO ECONOMICO SOSTENIBILE (ENEA)
UNIVERSITA DEGLI STUDI DI BERGAMO
IPC8 Class: AD01G1100FI
Class name: Textiles: manufacturing textile product fabrication or treatment
Publication date: 2014-09-04
Patent application number: 20140245577
A method for the manufacturing of textile products in the form of a yarn,
web or tow starting from recycled carbon fibers in the form of tuft,
cloth or the like, comprising the steps of: • (a) discontinuous
cutting of the fibers to obtain dimensionally homogeneous fibers of
selected length; • (b) enzyming of the fibers cut in step (a),
wherein the latter are additioned with one or more substances; •
(c) blending of the fibers treated in step (b) with auxiliary fibers;
• (d) double carding of the blended fibers obtained in said step
(c); and • (e) feeding a pair of wicks to a spinning machine.
1. A method comprising the steps of: (a) discontinuous cutting of the
fibers, carried out so as to obtain fibers of a minimum length equal to
about 30 mm and substantially dimensionally homogeneous; (b) enzyming of
the fibers cut in step (a), wherein the latter are additioned with one or
more substances; (c) blending of the fibers treated in step (b) with
auxiliary fibers; and (d) parallelizing of the blended fibers obtained in
said step (c), which parallelizing is carried out by a carding with a
plate-fitted card, or by double carding, always with plate-fitted cards
(carding segments); which is a method of manufacturing semi-finished
products starting from recycled carbon fibers in the form of tuft, cloth
or the like.
2. The method according to claim 1, wherein between said steps (a) and (b) it is provided an intermediate step of opening the fiber tuft or cloth, preferably carried out by a rag-grinding unit.
3. The method according to claim 1, wherein in said step (b) fibers are additioned with an antistatic substance, a substance with sliding power and/or with a substance suitable to give adhesive properties to the fibers.
4. The method according to claim 1, wherein said auxiliary fibers are one or more fibers selected from the group consisting of: thermoplastic fibers of polyester, PEEK, co-PES, co-PA, PP, PE, PS, PVA type; natural fibers, of cotton, hemp, linen type; metallic fibers; glass fibers and aramid fibers.
5. The method according to claim 1, wherein said step (d) provides a double carding operation.
6. The method according to claim 1, wherein said step (d) provides as output the obtainment of a semi-finished product in the form of a film.
7. The method according to claim 1, wherein said step (d) provides as output the obtainment of a semi-finished product in the form of a web.
8. The method according to claim 1, wherein in said step (c) organic, soluble or thermolabile fibers are used as auxiliary fibers, and wherein, downstream of said spinning step, it is provided a further step of removing the auxiliary fibers, based on a chemical, thermal or physical action.
9. The method according to claim 1, wherein downstream of said step (d) the following steps are provided: (e) pre-spinning for the obtainment of wicks; and (f) spinning in a spinning machine fed with pairs of wicks obtained in said pre-spinning step (e).
10. The method according to claim 9, wherein downstream of said spinning step it is provided a step of coupling plural wick strands (double feeding) and/or a step of twisting the yarn.
11. The method according to claim 1, wherein downstream of said step (d) it is provided a step of cohesioning the film with a cohesioning material.
12. The method according to claim 11, wherein downstream of said cohesioning step it is provided a step of longitudinal cutting in the direction of the film, to make a web or tow.
13. A semi-finished product obtained by the method of claim 1.
14. The semi-finished product according to claim 13, which is in the form of a web.
15. An apparatus comprising: a cutting unit, apt to carry out a discontinuous cutting of the fibers so as to obtain dimensionally substantially homogeneous fibers of a minimum length equal to about 30 mm; an enzyming unit for enzyming the fibers cut in said cutting unit, wherein the latter are additioned with one or more substances; a blending unit for blending the fibers treated in said enzyming unit with auxiliary fibers; and a parallelizing unit for parallelizing the blended fibers obtained in said blending unit, which parallelizing unit comprises a plate-fitted card; which is an apparatus configured to manufacture semi-finished products starting from recycled carbon fibers in the form of tuft, cloth or the like.
16. The apparatus according to claim 15, wherein said cutting unit comprises means for adjusting the length of the fibers being output, preferably obtained by an adjustment of the cutting pitch, of the cutting rate and/or of the fiber feed rate.
17. The apparatus according to claim 15, comprising an opening unit for opening the fiber tuft or cloth, interposed between said cutting and enzyming units and preferably comprising a rag-grinding unit.
18. The apparatus according to claim 15, wherein said parallelizing unit comprises a double carding unit.
19. The apparatus according to claim 18, wherein a single carding unit comprises, in sequence: a pair of feed cylinders; an inletting cylinder and a doffing cylinder, arranged so as to act synergistically on the fibrous mass; a drum suitable for making the fibers elementary; a plurality of carding systems apt to open and parallelize the fibers; an unloading cylinder; a film-detaching means associated to said unloading cylinder; and preferably a drawing system.
20. The apparatus according to claim 15, wherein said double parallelizing unit is apt to provide as output a semi-finished product in the form of a web.
21. The apparatus according to claim 15, comprising, downstream of said parallelizing unit; a pre-spinning unit; and a spinning unit comprising a spinning machine fed with pairs of wicks obtained in said pre-spinning unit.
22. The apparatus according to claim 15, comprising means for coupling plural yarn strands and/or for twisting the yarn, arranged downstream of said spinning unit.
23. The apparatus according to claim 15, comprising a cohesioning unit with a cohesioning material for the forming of a film, arranged downstream of said parallelizing and drawing unit.
24. The apparatus according to claim 23, comprising a cutting unit arranged downstream of said cohesioning unit.
TECHNICAL FIELD OF THE INVENTION
 The present invention refers to a method for the manufacturing of a semi-finished product starting from recycled carbon fibers, in particular a semi-finished product suitable for the subsequent obtainment of a yarn or of a so-called "tow".
 The high ratio between mechanical properties and weight causes Carbon Fiber-Reinforced Plastics (CFRPs) to be ever more successful, in terms both of variety of applications and of volumes of sale.
 However, though it is true that composite materials using reinforcement carbon fibers and the related technical fabrics are increasingly considered as the materials of the future, the problem of disposal of components manufactured therewith at the end of their service life has not yet been posed nor addressed adequately.
 For instance, to date CFRP and CF yarn manufacturing waste disposal occurred in a dump or by incineration. However, such solutions are very onerous, from both an economical standpoint and an ecological one.
 Moreover, a few CFRP recycling techniques have been devised, some with the aim of separating the resin from the fibers, leaving the latter as intact as possible. An example in that sense is provided by WO 2003/089212, describing a CFRP incineration method aimed to remove the plastic matrix and recover fibers contained therein. With said process the recycled fibers obtained as output retain about the 80% of the mechanical properties of original fibers present in the composites treated. In general, fibers recovered with this method, taken individually, retain a fair part of the starting physical properties, but appear entangled and possibly contaminated by other materials and dusty residues. In addition, since waste undergoes a grinding treatment before being processed, fiber length is extremely variable.
 Moreover, the problem of the effective re-use of recycled fibers in an industrial field, i.e. of the manufacturing of semi-finished products directly usable in a primary production chain, remains anyhow open. In this connection, besides the afore-mentioned drawbacks there should also be considered:
 the excessive fragility of recovered carbon fibers, which causes the industrial processing systems to be too invasive, breaking up, until pulverizing, a significant part of the carbon fibers treated;
 the remarkable susceptivity of the fibers themselves to electrostatic phenomena, making their processing particularly difficult;
 the electrical conductivity of the fibers at issue, posing the need to safeguard processing apparatuses and machines from the risk of short circuits; and
 the risks in terms of salubrity and safety, associated to the dispersion of such short fibers in the work environment.
SUMMARY OF THE INVENTION
 Therefore, the technical problem set and solved by the present invention is to provide a method for the manufacturing of semi-finished products starting from recycled carbon fibers, overcoming the drawbacks mentioned above with reference to the known art.
 Such a problem is solved by a method according to claim 1 and by an apparatus according to claim 15.
 Preferred features of the present invention are the subject of the dependent claims.
 It will be understood that, in the present context, by "recycled" carbon fibers are meant fibers recovered from other applications, in particular both pre-treated at the end of the service life of a finished product, and virgin fibers discarded from other processings.
 The invention allows to obtain, starting from recovered carbon fibers, semi-finished products suitable for the manufacturing of new finished quality products. In particular, the method and the apparatus of the invention make the recovered fibers, with a particularly reduced length, suitable for spinning processes, overcoming the workability problems mentioned above with reference to the known art and enabling the manufacturing of finished textile manufacts of various kinds, thereby fostering recovered fibers reintroduction on the market.
 In the semi-finished products obtained with the invention, carbon fibers are in a shape substantially aligned, or anyhow have a main direction of orientation, and discontinuous, i.e. there are various fiber segments, aligned with ends overlapped. Thanks to the method and apparatus of the invention, the fibers in the semi-finished product have a degree of alignment comparable with that of virgin fibers. As is known, fiber alignment along the direction of the stress enables to enhance the performance contribution of the fibrous phase itself.
 An example of privileged industrial application of the semi-finished products obtained with the invention is the manufacturing of reinforcement members of composite materials.
 In particular, reinforcement fabrics can be manufactured which are able to optimally adjust to complex-shape molds, giving to the composite an adequate resistance even in zones with a very strong radius of curvature.
 In the known art, such complex shapes are obtained starting from yarns of virgin and continuous carbon fiber, which are subjected to a lengthening process until attaining a yarn comprised of randomly broken filaments, referred to as SBCF (Short Broken Carbon Fiber). Thus, relative motions among the filaments themselves are allowed. This technology, however, entails the limitation of a scarce predictability in fibers lengths, and of the increase in production expenses, due to the remarkable cost of yarns of virgin carbon fiber.
 Instead, as mentioned above, in the semi-finished product of the invention the fibers are already in discontinuous form. Therefore, the resulting fabric exhibits a "pseudo-ductility", similar to that of metals, which greatly facilitates the formability of complex-shape components, by accelerating lay-up operations and remarkably reducing wrinkling in the reinforcement of the composite material.
 Therefore, the method of the invention allows to attain substantially the same features of discontinuity and alignment of the known virgin fiber yarns, but at a remarkably reduced cost and with a good control of fiber length.
 Moreover, pre-forms obtained starting from the method of the invention can effectively be dimensionally stabilized by organic or inorganic yarns.
 Furthermore, association with suitable thermoplastic yarns allows to enhance some properties of the CFRPs manufactured with such pre-forms, such as, e.g., tenacity and flame-retardant aptitude.
 As mentioned above, the fibers recovered and made workable with the method of the invention are usable at a cost remarkably lower than with the use of virgin carbon fiber, though providing comparable performances.
 The invention enables a remarkable cost reduction, both on the economical and the environmental sides, also since it avoids having to dispose of in a dump, or send to incineration, CFRP products or waste, or waste from the processing of yarns and manufacts of virgin carbon fiber.
 In a preferred variant embodiment, the semi-finished product of the invention is subjected to a spinning processing with discontinuous cutting.
 In another preferred variant embodiment, the semi-finished product of the invention is hot-cohesioned by application of additives, or cohesioning materials in general, to obtain as output a web or tow.
 The yarn, web or tow obtained downstream of such processings has physical-mechanical performances adequate to a use in the field of functional textile manufacts, which may also be utilized as reinforcement for composite materials having a polymeric matrix. Moreover, as already mentioned above, the textile manufacts, being manufactured from aligned and discontinuous carbon fibers, exhibit interesting features in term of drapeability.
 Other advantages, features and operation steps of the present invention will be made apparent in the following detailed description of some embodiments thereof, given by way of example and not for limitative purposes.
BRIEF DESCRIPTION OF THE FIGURES
 Reference will be made to the figures of the annexed drawings, wherein:
 FIG. 1 shows a schematic flowchart illustrating a sequence of processing/treatment steps of a preferred embodiment of the method according to the present invention;
 FIG. 2 shows a block schematic depiction of a preferred embodiment of apparatus carrying out the method of FIG. 1;
 FIG. 3 shows a schematic depiction of a possible implementation of a carding sequence of the method of FIG. 1;
 FIG. 3A shows an example of "tandem-card" carding used in the method of FIG. 1;
 FIG. 4 shows a force/elongation diagram relative to the mechanical properties of a yarn obtained with the method of FIG. 1; and
 FIG. 5 shows a schematic depiction of a possible implementation of a spinning device of the method of FIG. 1.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
 Referring initially to FIG. 1, it shows a sequence of steps according to a preferred embodiment of the method of the invention for the manufacturing of semi-finished products starting from recycled carbon fibers.
 Correspondingly, FIG. 2 shows a preferred embodiment of an apparatus specifically suitable for the carrying out of the above-mentioned method, apparatus generally denoted by 100.
 In the present embodiment of method and of apparatus, these work on carbon fibers as provided as output by the method of which at the aforecited WO 2003/089212, incorporated herein by this reference. In particular, in the present example recovered carbon fibers, initially in the form of tuft or cloth, are considered.
 In general, as mentioned hereto, the method and the apparatus of the invention are suitable to the treatment of carbon fibers recovered from the recycle of composite materials or waste from the processing of virgin carbon fibers.
 Thus, referring to FIGS. 1 and 2, in a first step of cutting the recovered carbon fibers are cut, so that the length of the starting fibers be gauged and that those therefore be substantially homogeneous from a dimensional standpoint. In particular, the tuft/cloth of recovered fibers is laid over a feed system 101, preferably automatic and, e.g., of conveyor belt type, and sent to a rotary cutter 102 or to an equivalent cutting unit.
 Preferably, the pitch of the blades of the cutter 102, their cutting rate and/or the fiber feed rate are adjustable so as to allow a corresponding adjustment of the length of the cut fibers being output.
 The minimum length of the carbon fibers that can be treated with the method and the apparatus considered herein is, downstream of the cutting step, of about 30 mm. Accordingly, there is a considerable increase in the amount of carbon fibers that can be spun.
 In general terms, the fibers being output from said cutting step have a length comprised in a range of about 30-60 mm.
 Cut fibers are then collected, preferably always by an automatic extraction system 103 and, e.g., of conveyor belt type, and fed to an opening unit 104 for opening the tufts/cloths, so as to blend the fibrous blanket for a first time. To this end, the device 104 is typically a rag-grinding machine or carding willow.
 Thus the fibrous mass is refined, obtaining also a first step of partial parallelizing of the fibers.
 In a subsequent enzyming step, the fibrous mass is inlet--preferably by mechanical and/or pneumatic transport means and/or--into a hopper 105 of an enzyming unit 106. In the latter, the fibrous mass is sprayed by nozzles, which nebulize a (typically water-emulsified) product having a twin power: the product fosters fiber sliding and abates electrostatic charge. In this step, there may also be envisaged the applying of a substance which improves the adhesive properties of the carbon fiber, as is the case for virgin fibers on which a substance, generally of epoxy type, referred to as "sizing" is deposited.
 The enzyming step is of remarkable significance, as it provides fibers more mechanically protected, more slidable and less electrostatic for the subsequent treatment and processing steps.
 The fibrous mass is then subjected to a step of blending with auxiliary fibers in a suitable unit 107. In this case as well, the fibrous mass can be automatically fed to the blending unit 107, by a conveyor belt or an equivalent means.
 The percentage of auxiliary fibers added to the mass of carbon fibers being input can be variable and adjustable, depending on the processing specifications and in particular on the textile manufact that is to be obtained as output, so as to obtain a homogeneous material able to guarantee even distribution of reinforcement carbon fibers in the semi-finished end product.
 Auxiliary fibers may be of organic nature, as well as of inorganic nature. By way of a non-limiting example there are reported as auxiliary fibers, e.g.: thermoplastic fibers of polyester, PEEK, co-PES, co-PA, PP, PE, PS, PVA type; natural fibers of cotton, hemp, linen type; metallic fibers, glass fibers and aramid fibers.
 The auxiliary fibers may have a supporting function for the subsequent steps, in particular a spinning step which will be introduced below, and/or also give specific functional properties to the semi-finished product that is output and to the fabric or manufact manufactured therewith.
 The blended fibrous mass is then subjected to a parallelizing operation in a suitable unit 108. In a particularly preferred embodiment, such parallelizing step is a (preferably double) carding step, carried out in a suitable carding machine, at the output of which just a carded material, definable as film or web, is obtained.
 A preferred embodiment of said carding unit 108 is shown in FIG. 3. Referring to this latter figure, the fibers of a length of 30-60 mm are fed to the carding unit 108. The fibrous material transits through a pair of feed cylinders 1, which pinch the blanket being input and pass it to an inletting cylinder 2, working synergistically with a doffing cylinder 3, the latter preferably placed below the inletting cylinder 2 and at a distance therefrom dictated by the specific production needs. The doffing cylinder 3 has the task of parallelizing and adjusting the fibrous mass brought onto the inletting cylinder 2.
 A drum 4 rotates clockwise and has clothing points (with a special profile ensuring maximum holding of the fibers) tilted in the same sense of the motion (i.e., the points work in the positive sense of the motion). To be able to make fibers elementary, in order to have them set for carding and therefore for a further parallelizing, disentangling the same from tangles or thickenings yet unopened or compact, it is necessary that the clothing be particularly thick (about 600 points/in2) and have a working angle of about 25°.
 A carding segment 5--interchangeable according to the grade of the material treated (processing scraps or fibers recovered from CFRP)--has the purpose of parallelizing the fibers even more, reducing their mass, uniformly distributing them on the drum 4, thereby facilitating the task of the actual carding.
 The carding action, enabling the feed and the partial parallelizing of the fibers, is increasingly ensured by the further carding sectors 6, 8, 10 and 12 set at an adjustable distance from the drum 4; such a distance or adjustment will be all the more narrow the more the fiber output zone is approached (as an indication, 25 to 12 thousandths of inch). The drum 4, thanks to its large diameter and its rate, creates a centrifugal force that enables fibers, on the one hand, to be held by the clothing, and, on the other hand, to be carded by the carding sectors themselves. The clothings exhibit a point thickness progression toward the outlet, carrying out a gradually more marked parallelizing of the fibers.
 Each carding sector, therefore, has a more intense action depending on the number of points per square inch and on the tilt of the same points with respect to those of the drum 4. Between one sector and the other one there are open slits 7, 9 and 11, preferably of 10-20 mm of width, each of which--by a special profile called "presser or tegolino"--is able to separate the fraction of short fibers (or broken fibers) and the carbon dust generated during the carding step, dust which would prove damaging for the subsequent processings. A suction system guarantees removal of these particles, making more compact and even the material on the drum.
 Another carding system 13, of a typology analogous to the segment 5, but with a clothing with thinner and thicker-populated points, set at the outlet of the drum 4, enables a further parallelizing of the fibers, by disentangling the last possible fibrous thickenings. As to fiber transit, fibers held on the clothing of the clockwise-rotating drum 4 pass on an unloading cylinder 14. The latter rotates counterclockwise, and has points which grab the fibers, holding them by friction, condensing them thereon due to the big difference in peripheral velocities of the two bodies.
 Unloading of carded material occurs thanks to a film-detaching device 15 working synergistically with the unloading cylinder 14. When being output from the device 15, the semi-finished product is in the form of a compact film of fibers.
 The film thus obtained could be collected and set aside for a new carding step utilizing the same process, thereby obtaining the above-mentioned double carding. Such operation might be carried out by a "tandem card" carding system, known per se and shown by way of example in FIG. 3A. The cards of this latter system have to be fitted like the preceding card, described and reported in FIG. 3. Thus, the fiber will not be stressed and therefore reduced in length, or torn by drawing systems traditionally used in short fiber spinning systems.
 The film being output from the single or double carding step is comprised of fibers by now well-parallelized, and could be forwarded to intermediate finishings in the form in which it is manufactured.
 The carding by carding segments or plates is specifically suitable to be able to process short fibers having a high ultimate strength, but fragile like carbon ones are, even when blended with other fibers, be them natural, organic and inorganic.
 In a variant embodiment, said film is entrained to a very simple and reduced drawing system 16, thereby undergoing a drawing step. The drawing system 16 operates a reduction, or condensation, of the fibrous bundle in order to obtain as output of the same drawing system a fibrous web. Being output from such a drawing system 16, the semi-finished product is in the form of a web.
 The use of a large-diameter cylinder 4 with clothings of special rubbers, or equivalent means apt to guarantee the abatement of electrostatic charges, fosters drawing.
 The preparation to the spinning is carried out in a unit 109, through the use of a very simple and reduced drawing system which preferably enables the fibers to be drawn by a twisting system, forming a thin web, or wick.
 The wick thus obtained is set on special supports apt to the unwinding of the same wick. Such supports are an integral part of a feed system for the feeding of a cylinder spinning machine 110 or of an equivalent device.
 Referring to FIG. 5, wicks are inlet by a relevant double funnel, ensuring both the centering and an even feeding. In the preliminary and central zone of the drawing system there are special contrivances enabling the sliding of the fibers, without having them piling up or floating or condensing. A double pair of cylinders ensures the right tension and preliminary drawing with partial opening of the wicks themselves, wicks which again transit into a separator individually inletting the two fiber bundles into the main drawing system, where the actual drawing occurs. At the output, fibers are reunited by twisting, obtaining an even and strong yarn (Siro-spun® system) which will in turn be returned by the ring-ringlet combination for winding. Collecting occurs according to the traditional method of spindle winding, with particular care to the selection of the spinning geometry, the ring, the traveller and the rotation rate thereof.
 The yarn being output from the spinning machine 110 will be collected on suitable supports, apt to facilitate yarn unwinding for further processings. The operations subsequent to spinning require yarns with a good ultimate strength and a determined size (count). The yarn could then be subjected to two- or plural-strand coupling and be subjected to twisting, or be coupled and twisted with other typologies of yarns or filaments having specific properties selected depending on the purpose to which the end product will be intended for. The yarn thus obtained could in turn be twisted again in order to obtain a simple-twist thread or a cord (twist of plural twisted threads).
 On the basis of a second variant, corresponding to the left-side branch of FIGS. 1 and 2, it is had a step of forming a fiber blanket, more or less light-weight and uniform (according to the final weight that is to be reached) as if it were a film; there follows a cohesioning step, and finally a step of cutting in the longitudinal direction, obtaining as output a web or tow.
 As to the film-forming step, this is carried out in a relevant device 111 by using a cohesioning material, e.g. a thermoplastic material, a resin or a combination thereof, in the form of fibers or liquid or solid additives. Thus, it is obtained just a fiber film that is then continuously fed to an activation unit 112, suitable to activate the cohesioning material and therefore to bring about the actual cohesion of the web. E.g., when the cohesioning material is a thermoplastic, a heating unit will be resorted to.
 Thus, a semi-finished product is obtained which, cut e.g. in a thread-shaped or web-shaped manner in a unit 113, represents a valid alternative to the twisted yarn obtained with the first variant embodiment described above.
 The yarn, tow or web provided by the above-described apparatus and method can be managed as standard semi-finished products of continuous fiber, and therefore can undergo subsequent weaving processes with optional subsequent pre-impregnation.
 Such semi-finished products allow the design and manufacturing of novel materials having selected properties of strength, ductility and/or tenacity, even with respect to the different directions, concomitantly optimizing the use of the single components, both in mechanical and quantitative terms. Therefore, it is evident that a composite thus manufactured, properties being equal, is also lighter in weight than a traditional material.
 A particular application of the auxiliary fibers consists in the supporting of the spinning for the obtainment of 100% carbon fiber yarns; an example consists in the cotton that may be used as support fiber during the spinning step and after, when the manufact (thread or web) has been manufactured, it may be removed by acid attack, leaving the carbon fiber fabric unaltered. The same may hold true for the use of soluble or thermolabile auxiliary fibers. A particular application may be the use of thermoplastic-type auxiliary fibers soluble in the polymeric matrix of the end composite, enabling to increase the tenacity of the end manufact.
 It will be understood that the devices and the units of the above-described apparatus 100 are equipped with means, per se known, suitable to prevent the carbon fiber, particularly conductive electrically and statically, from damaging related electrical parts, control systems and/or safety devices. Hoods, shields, protections, wirings and the like are the most common known precautions for performing this task.
 Some experimental results attained on an end product (the yarn), containing 40% by weight of recovered carbon fibers are discussed hereinafter, purely by way of a non-limiting example.
 Table 1 reports the average features of tensile strength of the carbon fibers recovered by the thermal treatment of which at WO 2003/089212 and utilized for the manufacturing of a yarn following the preferred embodiment of the method discussed above.
 The characterizations of the individual filaments have been carried out on two test lengths (10 and 40 mm), with 20 test pieces per each length according to standard ISO11566:1996 ("Carbon fibre--Determination of the tensile properties of single-filament specimens").
TABLE-US-00001 TABLE 1 Filament Young's Ultimate Test length diameter modulus strength [mm] [μm] [GPa] [MPa] 10 4.7 255 (±111) 2723 (±669) 40 4.7 268 (±58) 2603 (±1368)
 Recycled composites consisted of epoxy resin reinforced with carbon fibers of ToraycaT800s type (Intermediate modulus, high tensile strength fiber), with the following features declared: Tensile Modulus: 294 GPa; Tensile Stress: 5880 s MPa; Filament Diameter: 5 μm.
 The diagram of FIG. 4 reports the physical-mechanical dynamometric properties of the end product (the yarn), containing 40% by weight of recovered carbon fibers, blended with auxiliary thermoplastic fibers.
 Determination of carbon fiber content of the obtained yarn was carried out by tests performed with differential scanning calorimetric analyses and with thermogravimetric analyses.
 FIG. 4 demonstrates that the features of the individual yarn obtained are fully satisfactory and that they enable to manufacture textile manufacts of various typology, to be used, inter alia, as reinforcement for composite materials.
 Always from FIG. 4, it is inferred that the physical-mechanical features of the yarn are all the more performing the more the yarn itself is twisted.
 The present invention has been hereto described with reference to preferred embodiments thereof. It is understood that other embodiments might exist, all falling within the concept of the same invention, as defined by the protective scope of the claims hereinafter.
Patent applications in class TEXTILE PRODUCT FABRICATION OR TREATMENT
Patent applications in all subclasses TEXTILE PRODUCT FABRICATION OR TREATMENT