WO2019194761A2

WO2019194761A2 - Thermoplastic prepreg production method

Info

Publication number: WO2019194761A2
Application number: PCT/TR2018/050612
Authority: WO
Inventors: Elcin CAKAL SARAC; Deniz KORKMAZ; Egemen BILGE
Original assignee: Kordsa Teknik Tekstil A.S.
Priority date: 2017-10-20
Filing date: 2018-10-19
Publication date: 2019-10-10
Also published as: TR201716208A2; WO2019194761A3

Abstract

The present invention relates to a thermoplastic prepreg production method which is developed in order to be used as structural and visual material in all industrial fields, mainly aviation, defense industry, medical, marine and automotive, and which enables thermoplastic resin to be impregnated into non-crimp dry fabric formed by weaving yarn (A) layer (matrix) manufactured from at least unidirectional reinforcing fiber with yarn (B) layer manufactured from at least unidirectional polymeric fiber. The layers forming the non-crimp fabric are formed by including the meltable thermoplastic yarn (C) in weft and warp direction into the system. The objective of the present invention is to enable the resin used in prepreg application to impregnate more into the non-crimp dry fabric manufactured by weaving method compared to the conventional applications. In other words, the objective of the present invention is to provide a thermoplastic prepreg method which provides the wettability of the fabric produced with a yam (A) manufactured from reinforcing fibers.

Description

THERMOPLASTIC PREPREG PRODUCTION METHOD

Field of the Invention

The present invention relates to a thermoplastic prepreg production method which is developed in order to be used as structural and visual material in all industrial fields, mainly aviation, defense industry, medical, marine and automotive, and which enables thermoplastic resin to be impregnated into non-crimp dry fabric formed by a yarn (A) layer (matrix) that is manufactured from at least unidirectional reinforcing fibers and a yam (B) layer manufactured from at least unidirectional polymeric fibers. The layers forming the non-crimp fabric are formed by including the meltable thermoplastic yarn (C) in weft and warp directions into the system.

Background of the Invention

The prepregs are divided into two main categories, namely thermoset and thermoplastic. The thermoplastic prepreg is a structure comprised of thermoplastic resin impregnated yarns manufactured from reinforcing fibers. The thermoplastic prepregs are very popular today due to their lightweight, recycling potential, and resistance against corrosion properties.

Today, the resin used in thermoplastic prepreg production is applied as powder, film or granule. The thermoplastic prepregs that are obtained are then transformed into composite material which is the final product with production methods such as, thermoforming, compression molding via heat and pressure or overmolding.

In thermoplastic prepreg production, materials such as polyamides (PA) (polyamide 6 (PA6), polyamide 6,6 (PA66), polyphthalamide (PPA)), polyphenylene sulfide (PPS), polysulfone (PSU) polyarylenethersulfone, polyolefines (polyethylene (PE), polypropylene (PP) etc.), polyimide (PI), polyesters, preferably such as polyethylene terephthalate (PET) or polybutylene terephthalate (PBT), polyether ether ketone (PEEK) can be used.

Manual or automatic methods are preferred in feeding the resin in powder, film and granule form to the system. Especially powder and granule applications used in thermoplastic prepreg production cause homogenization problem in distributing resin, difficulty in using optimum raw material, and high amount of waste occurring during production.

Thermoplastic prepreg production is performed with discontinuous or continuous methods. In both discontinuous and continuous methods, even in case of feeding the resin in powder form is automatic, the thermoplastic resin/reinforcing fiber ratio cannot be applied in the desired accuracy. Variations occur in the powder amounts used in unit area. In case it is supplied in granule form, since resin particles sizes are too big, accumulations occur since homogenous melting cannot be achieved on the thermoplastic prepreg. The impregnation of the resin in the fiber structure is not easy due to same reason. In other words, the resin cannot penetrate into the structure comprised of yam manufactured from reinforcing fiber homogenously.

United States Patent Document no US5445701, an application known in the state of the art, discloses a thermoplastic resin method in form of film. However, this method is expensive, as well as difficulties in supplying the film compatible with the thermoplastic material can be experienced.

In United States Patent Document no US20140030582, an application known in the state of the art, the wall thickness of the thermoplastic prepregs of the present invention can be manufactured in range of 0.3 and 6.0 mm. The said invention can function in a limited field since it is not for thermoplastic prepregs with bigger wall thickness. United States Patent Document no US5464684, an application known in the state of the art, discloses a production method of the polyamide based hybrid yarn. In this method, thermoplastic yarn and reinforcing yam are produced by mixing with each other by air application. Depending on the complexity of the yarn mixing process and application of twisting process on carbon fiber which is very brittle, causes decrease of the linear strength of the carbon fiber.

Summary of the Invention

The objective of the present invention is to enable the resin used in prepreg application to impregnate more into the non-crimp dry fabric manufactured by weaving method compared to the conventional applications. In other words, the objective of the present invention is to provide a thermoplastic prepreg method which provides the wettability of the fabric produced with a yam manufactured from reinforcing fibers.

Another objective of the present invention is to provide a thermoplastic prepreg production method which enables to apply more accurate amount of resin to the non-crimp dry fabrics comprising reinforcing yam and thermoplastic yam and also to provide more easily processing of them.

The most important advantage of the invention is to allow production of non crimp fabrics used in thermoplastic prepreg production in standard weaving machines or hand looms without requiring multiaxial textiles production machine.

In non-crimp fabrics produced with the inventive method, since there is no crimp present in weave structure produced with standard methods, higher mechanical strength values in unit area can be achieved. Detailed Description of the Invention

The “Thermoplastic prepreg application method” developed to fulfill the objectives of the present invention is illustrated in the accompanying figures, in which:

Figure 1 is the view of the non-crimp fabric used for unidirectional thermoplastic prepreg manufactured with the inventive thermoplastic prepreg application method.

Figure 2 is the detailed view of the non-crimp fabric produced in weaving machine with the inventive thermoplastic prepreg application method.

The components shown in the figures are each given reference numbers as follows:

A. Reinforcing yam

B. Thermoplastic yam (matrix)

C: Meltable thermoplastic yarn

For example, unidirectional thermoplastic prepreg is obtained in a way disclosed in the invention after including meltable thermoplastic yam into the system in weft and warp direction as it is seen in Figure 2 in order to keep the unidirectional stmcture manufactured from thermoplastic yam used in first and last layer of the non-crimp fabric and the stmcture manufactured from unidirectional reinforcing yarn used in middle layer together shown in Figure 1.

The inventive uni-directional, biaxial, triaxial or multiaxial thermoplastic prepreg production method enables resin to be impregnated into the fabric homogenously and deeply in resin impregnation process realized in order to reinforce the non crimp fabric which is manufactured, and comprises the steps of

- Obtaining reinforcing yam and thermoplastic yarn used in production of non-crimp fabric by using weaving machine, Weaving with meltable thermoplastic yam (C) in weft and warp direction in order to combine thermoplastic yarn (B) and reinforcing yarns (A) determined in thermoplastic prepreg design in fabric production process, Placing unidirectional layer comprising thermoplastic yam (B) on lower and/or upper surface of each one of the unidirectional layers manufactured with reinforcing yarn (A),

At least one layer being comprised of at least two layers such that it will comprise a layer including“unidirectional reinforcing fibers”,

Increasing the temperature of the non-crimp fabric above the softening point or melting point of the thermoplastic yarn,

Applying pressure (0-100 bar) on the non-crimp fabric at this temperature, Applying pre-tensioning (0-5 g/tex) on the non-crimp fabric at this temperature,

Enabling the meltable thermoplastic yarn (C) used for combining the structure with the thermoplastic resin (B) used in yarn form as a matrix to penetrate between the fibers of reinforcing yam (A) by melting within the fabric,

Applying temperature and pressure for a time in range of 2-120 minutes, Obtaining the ready to use final product by cooling until it reaches a temperature below glass transition temperature (T_g) of the resin without pressure or under pressure.

In the said invention, the thermoplastic yarns used in forming the non-crimp fabric is used in form of a thermoplastic yam (B) selected from a group comprising polyamides (such as polyamide 6 (PA6), polyamide 6,6 (PA66), polyphthalamide (PPA) ), polyphenylene sulfide (PPS), polysulfone (PSU) (such as polyethersulfone (PES), polyary lenethersulfone), polyarylenesulfide, fluoropolymer, polyacetal, polikarbonat, styrenic polymer, polyolefins (such as polyethylene (PE), polypropylene (PP)), polyimide (PI), polyetherimide, polyesters preferably polyethylene terephthalate (PET) or polybutylene terephthalate (PBT), polyether ether ketone (PEEK), polyether ketone (PEK), or combinations thereof.

In the said invention, as reinforcing yam (A) used in forming the non-crimp yam, a material selected from the group comprising glass fiber, carbon fiber, aramid fiber, natural fiber, or a combination thereof is used.

It is preferred that the thermoplastic yam (C) used in weft and yarn direction in order to keep the weave together is from the same material as the resin (thermoplastic yarn (B)) used as matrix.

The term “non-crimp fabric” used in the invention is defined as a system comprised of two or more unidirectional fiber layers, and formed by holding these layers together by weaving with a yam manufactured from thermoplastic polymer. When the angles of the layers comprising unidirectional reinforcing fiber are considered, the prepregs comprised of non-crimp fabrics can be unidirectional, biaxial, triaxial or multiaxial.

The term“dtex” used in the invention is the weight in grams per 10.000 meters yarn.

In the inventive thermoplastic prepreg production method, the resin being in form of yarn manufactured from thermoplastic fiber enables the amount of resin/reinforcing fiber ratio in the thermoplastic prepreg to be adjusted easily.

In the present invention, the wall thickness of the thermoplastic prepregs which are the final products formed by penetrating the resin into the non-crimp yam is adjusted to be in range of 0.25 and 8 mm. The wall thickness of the thermoplastic prepregs comprising single layer reinforcing fiber depends on the type of the used reinforcing yam, areal weight of fabric and the pressure which is applied. The wall thickness of the thermoplastic prepregs manufactured from weave fabric obtained by holding the system comprising at least“single layer reinforcing yam” and produced as at least two layers together with a thermoplastic yarn manufactured from generally the same polymer as the resin used as the matrix depends on the number of the used unidirectional fiber layers, type of the reinforcing yam, areal weight of the non-crimp fabric and the pressure that is applied.

The present invention comprises application of 0-100 bars, preferably in range of 1-40, of pressure on the resin in step of heating of the resin.

In the present invention, the cooling of the resin penetrating into the reinforcing yarns of the non-crimp fabric is carried out under 0-100 bars of pressure, preferably in range of 1-40 bars of pressure.

In the present invention, the weight of the thermoplastic resin is in range of 10% to 90%, preferably 30% to 70% of the weight of the yam manufactured from reinforcing fibers.

In a preferred embodiment of the invention, in order to enable unidirectional (UD) thermoplastic prepreg production, unidirectional and single layered reinforcing yarns (A) and layers comprising thermoplastic yarn (B) on lower and/or upper surface of the said layer are used as matrix.

In a preferred embodiment of the invention, in order to enable biaxial thermoplastic prepreg production, biaxial and two layered reinforcing yarns (A) and layers comprising thermoplastic yam (B) on lower and/or upper surfaces of the said layers are used.

In a preferred embodiment of the invention, in order to enable triaxial thermoplastic prepreg production, triaxial and three layered reinforcing yams (A) and layers comprising thermoplastic yam (B) on lower and/or upper surfaces of the said layers are used.

In a preferred embodiment of the invention, in order to enable multiaxial thermoplastic prepreg production, minimum quadraxial and four layered reinforcing yams (A) and layers comprising thermoplastic yam (B) on lower and/or upper surfaces of the said layers are used.

The inventive thermoplastic prepregs can be used as structural and visual material in all industrial fields, mainly aviation, defense industry and automotive. The final product that is obtained is the semi-product called as the thermoplastic prepreg or organosheet.

In thermoplastic prepreg production, discontinuous or continuous methods can be used. The main principle used in both methods is to apply pressure (0-100 bars) at a temperature above softening or melting point of the thermoplastic resin, and to enable the resin to be impregnated into the reinforcing fibers in this way. Cooling process is applied after temperature and pressure is applied for a determined time between 2 minutes and 120 minutes. Cooling process can be applied without pressure or under pressure (0-100 bar) depending on the stmcture of the polymer. The cooling temperature is below the glass transition temperature (T_g) of the resin. The machine in which the inventive thermoplastics are produced can be heated up to 450°C depending on the structure of the plastic. The temperature range that can be used in cooling process is between 25°C and 200°C. The wall thickness of the inventive thermoplastic prepregs is in range of 0.25 mm to 8mm. The applications known in the state of the art cannot provide the resin to be homogenously impregnated into the fibers. On the other hand, in the inventive method, since the resin is used in yam form, the resin/reinforcing fiber ratio can be accurately adjusted. In summary, with the newly developed method, resin homogenization in amount is provided before starting the process. In order to provide the resin/reinforcing fiber ratio homogenously in a desired ratio in everywhere, the different dtex, different filament diameter and number of yam produced from thermoplastic fibers can be used. With the thermoplastic yarn application, increasing in plastic surface area and regular material orientation enable the resin to be melt more easily relative to especially the powder and granule applications. Therefore, product with higher quality can be obtained in a machine with lower accuracy. At the same time, the defects related to areal weight of resin that can occur during application are prevented.

The thermoplastic resins used as matrix in the non-crimp fabric application are applied in form of yam (B) on different layers of the fabric. The yams manufactured from reinforcing fibers (glass, carbon, aramid, natural fiber, etc.) are applied in single layer or different layers of the fabric in the same way, and the obtained hybrid structure is enabled to be appropriate for thermoplastic prepreg production. Two or more kinds of reinforcing yams (A) can be used in hybrid fabrics. For example, carbon, glass and thermoplastic yarn (B) can be used in the same weaved non-crimp fabric.

Within the scope of the inventive method, non-crimp fabrics used in thermoplastic prepreg production comprising reinforcing yam (A) and thermoplastic yarn (B) are enabled to be produced in standard weaving machines or hand looms without requiring multiaxial textiles production machine. Therefore, there is no extra process step required during powder, film or granule coating applied for conventional thermoplastic prepreg production, and thus the production is carried out faster without investing in extra machinery.

In the non-crimp fabrics in order to obtain the inventive thermoplastic prepregs, since there is no crimp structure where the fibers of the weave fabrics produced with standard method come on top of each other, higher mechanical strength values in unit area can be achieved. In production of thermoplastic prepregs, non-crimp fabrics comprising reinforcing yarn (A) and thermoplastic yarn (B) can be processed in more accurate resin amounts, and they can be processed more easily. The thermoplastic composite structure which is the end product can easily reach the resistance values desired to be acquired with the design of fabric layers. By means of the non-crimp fabric types that are designed differently, thermoplastic prepregs with different mechanical features can be obtained. By this means the composite structure can be varied compatible with the field of use of the end user. The non-crimp fabric application is suitable for being used in wide range of application fields since it allows placing the reinforcing yam in different axes.

Claims

1. A thermoplastic prepreg material production method characterized by the steps of

a) obtaining a non-crimp fabric by weaving at least two layered structure comprising reinforcing yams (A) and meltable thermoplastic yarns (B) as matrix with meltable thermoplastic yarns (C) used in weft and yam direction for keeping the stmcture together,

b) impregnating resin into the layer(s) of the said non-crimp fabric comprising reinforcing fiber by means of applying pressure in range of

0-100 bars on the said non-crimp fabric in process of melting or softening the said meltable thermoplastic yams (B and C),

c) applying pressure in range of 0-100 on the said resin impregnated non-crimp fabric, cooling the said thermoplastic yarns to a temperature below glass transition temperature.

2. A thermoplastic prepreg production method according to any one of the preceding claims, characterized in that the said meltable thermoplastic yarns (B and C) are from same type of material and comprised of polyamide, polyolefin, polyether ketone, polyether ether ketone, polyimide, polyetherimide, polyaryleneketone, polyarylene sulfone, polyarylene ether sulfone, polyarylene sulfide, fluoropolymer, polyacetal, polycarbonate, styrenic polymer, polyester or combinations thereof.

3. A thermoplastic prepreg production method according to any one of the preceding claims, characterized in that the said reinforcing yams (A) used in forming the said fabric is manufactured from a material selected from the group including glass, carbon, aramid or natural fiber, or a combination thereof.

4. A thermoplastic prepreg production method according to any one of the preceding claims, characterized in that the layer comprised of the said reinforcing yarns and the layers comprised of the said meltable thermoplastic yams are unidirectional.

5. A thermoplastic prepreg production method according to any one of the preceding claims, characterized in that the said unidirectional layers comprised by the said non-crimp fabric is obtained as unidirectional, biaxial, triaxial or multiaxial by weaving them with different angles to each other.

6. A thermoplastic prepreg production method according to any one of the preceding claims, characterized in that the layers of the said fabric comprising the said unidirectional reinforcing yarns (A) are formed of same kind or hybrid yarns.

7. A thermoplastic prepreg production method according to any one of the preceding claims, characterized in that the ratio of the weight of the yams comprising thermoplastic yam (B and C) in the said structure to the weight of the reinforcing yam (A) is at least 10%.