PRE-PREG AND COMPOSITE PRODUCTS COMPRISING FIBERS AND A LIQUID CRYSTAL THERMOSET PRECURSOR

Abstract

A pre-preg product, such as a tape or sheet suitable for forming a composite having reinforcement fibers and a liquid crystal thermoset (LCT) precursor is provided. Further aspects of the invention are directed to a method for preparation of the pre-preg product and to composite products based on the pre-preg product.

Claims

1. Pre-preg product, such as a tape or sheet suitable for forming a composite, comprising reinforcement fibers and a liquid crystal thermoset (LCT) precursor that is a reactive precursor capable of forming an LCT upon reaction, wherein said pre-preg product is obtainable by a pultrusion process wherein an arrangement of the reinforcement fibers is moved through the melt comprising the liquid crystal thermoset (LCT) precursor.

2. Pre-preg product according to claim 1, wherein the LCT precursor has a director n that is substantially oriented along the longitudinal axis of the nearest reinforcement fiber.

3. Pre-preg product according to claim 1, wherein the LCT precursors have an orientational order parameter <P.sub.2> of between 0.1 and 1.

4. Pre-preg product according to claim 1, wherein the reinforcement fibers are selected from the group consisting of carbon fibers, fiber glass, aramid fibers, ceramic fibers, polybenzimidazole (PBI) fibers, polybenzoxazole (PBO) fibers, carbon nanotube fibers and combinations thereof.

5. Pre-preg product according to claim 1, wherein the liquid crystal thermoset (LCT) precursor is a liquid crystal thermoset (LCT) oligomer, optionally comprising a liquid crystal backbone selected from the group consisting of an ester, an ester-imide and an ester-amide, wherein at least 95 mol % of the monomers present in the backbone of the oligomer are aromatic.

6. Pre-preg product according to claim 5, wherein the LCT oligomer has a backbone having at least one structural repeat unit selected from the group consisting of ##STR00005## wherein Ar is an aromatic group.

7. Pre-preg product according to claim 5, wherein the LCT oligomer has a number average molecular weight (M.sub.n) of 1,000-13,000.

8. Pre-preg product according to claim 5, wherein the LCT oligomer has a phenylacetylene, phenylmaleimide, or nadimide end-cap.

9. Pre-preg product according to claim 5, wherein the LCT oligomer has a self-reactive end-group selected from the group consisting of ##STR00006## wherein R is independently one or more hydrogen, alkyl groups containing six or less carbon atoms, aryl groups containing six or less carbon atoms, aryl groups containing less than ten carbon atoms, lower alkoxy groups containing six or less carbons, lower aryloxy groups containing ten or less carbon atoms, fluorine, chlorine, bromine or iodine, and; wherein rings A and B are independently a 6-membered aryl or heteroaryl, optionally fused to an aryl or heteroaryl; X is independently O, C(O), OC(O), C(O)O, S, NR.sub.1, C(O)NR.sub.1 or NR.sub.1C(O); R.sub.1 is independently one or more alkynyl, alkyl, alkenyl, aryl, heteroaryl, cycloalkyl, heterocyclyl, halo, or haloalkyl and R.sub.2 is independently hydrogen, hydroxyl, alkyl, aryl, heteroaryl, cycloalkyl, or heterocyclyl.

10. Method for preparation of the pre-preg product according to claim 1, comprising impregnating an arrangement of reinforcement fibers with the liquid crystal thermoset (LCT) precursor, wherein said impregnation comprises a pultrusion process wherein the arrangement of reinforcement fibers is moved through the melt comprising the liquid crystal thermoset (LCT) precursor to obtain an impregnated reinforcement fiber arrangement, and said method optionally further comprises moving the impregnated reinforcement fiber arrangement through a heated die to obtained a shaped impregnated fiber arrangement and subsequently cooling to obtain the pre-preg product.

11. Method according to claim 10, wherein the melt is at a temperature of between 200 and 400 C.

12. Pre-preg laminate product based on a plurality of stacked pre-preg products according to claim 1, wherein the longitudinal axis of the reinforcement fibers of a first pre-preg product that is stacked on a second prep-preg product are oriented in a different direction than the longitudinal axis of the reinforcement fibers of the second pre-preg product.

13. Composite product that is based on a plurality of pre-preg products according to claim 1, wherein at least part of the pre-preg products are covalently bound.

14. Method for the production of a composite product according to claim 13, further comprising laying and heat setting of the pre-preg products.

15. Method according to claim 11, wherein the melt is at a temperature of between 250 and 350 C.

Description

EXAMPLE 1

[0084] A pre-preg was prepared by drawing a roving of T600 carbon fibers through a die containing molten LCT precursor (resin:fiber ratio 3:7).

[0085] An X-ray diffraction pattern was recorded and is shown in FIG. 3, wherein the fiber axis is vertically oriented. The X-ray diffraction pattern shows that the LCT precursor is highly aligned parallel to the fiber direction.

[0086] The intensity distribution indicates long-range orientation order of the LCT within the carbon fiber bundle. The intensity versus azimuthal angle (chi) plot of the X-ray diffraction pattern (FIG. 4) enables one to determine the orientational order parameter, <P.sub.2>, where <P.sub.2> is the average value of the second Legendre polynomial defining the orientation of the LCT molecular axes relative to the fiber direction. In this particular example, <P.sub.2>=0.79.