Method for treating reinforcing fibre and method for producing a reinforced composite article from the treated fibre

Abstract

The present invention relates to a reinforced composite material and a method for its production. The composite material comprises at least one cured resin having a reinforcing material. Preferably the reinforcing material is a plurality of glass fibers which are treated such that the properties of the interphase substantially surrounding each fiber are substantially equivalent to those of the bulk cured resin. The fiber treatment may be selected from the group consisting of a polymeric coating, a hydrophilic surface coating, a surface coating of a free radical inhibitor, or a reduction in the total surface area of the fibers. The reinforced composite material of the invention provides improved long-term mechanical properties compared to traditional glass fiber reinforced materials.

Claims

1. A reinforced composite material, comprising: i) a plurality of hydrophilic surface-modified reinforcing glass fibers, wherein the hydrophilic surface-modified reinforcing glass fiber comprises a reinforcing glass fiber modified with a hydrophilic surface coating comprising: a) a first coating of a vinyl functional silane coupling agent; and b) a second coating of the product of a vinyl functional silane coupling agent reacted with a polyol; ii) at least one cured polyester resin; and iii) at least one interphase defined by the at least one cured polyester resin adjacent to the at least one hydrophilic surface-modified reinforcing glass fiber of the plurality of hydrophilic surface-modified reinforcing glass fibers; wherein the at least one interphase has one or more properties substantially equivalent to those of the bulk at least one cured polyester resin, selected from the group consisting of: strength, flexural toughness, brittleness, density, cross-link density, chemical resistance, molecular weight, and degree of crystallinity.

2. The reinforced composite material of claim 1, wherein the at least one cured polyester resin is an at least one cured unsaturated polyester resin.

3. The reinforced composite material of claim 1, wherein the at least one cured polyester resin is an at least one cured hydrophilic, unsaturated polyester resin.

4. The reinforced composite material of claim 1, wherein the polyester of said at least one cured polyester resin has less than 33% w/w of monomer content.

5. The reinforced composite material of claim 4, wherein the monomer content of said polyester is between 5 to 30% w/w.

6. The reinforced composite material of claim 1, wherein the vinyl functional silane coupling agent of the first coating is independently selected from the group consisting of methacryloxypropyl-trimethoxysilane, vinylbenzylaminoethylaminopropyl-trimethoxysilane, and vinyl-tris(acetoxy) silane.

7. The reinforced composite material of claim 1, wherein the reinforcing glass fiber of the plurality of hydrophilic surface-modified reinforcing glass fibers has a length of between 100 and 1000 microns.

8. The reinforced composite material of claim 1, wherein the at least one cured polyester resin is provided by reacting a polyol with an acid, wherein: i) the polyol comprises propylene glycol, methyl propanediol, neopentyl glycol, or diethyleneglycol; ii) the acid comprises terephthalic acid, isophthalic acid, fumaric acid, or 1,4-cyclohexane diacid; and iii) said at least one cured polyester resin comprises a saturated to unsaturated acid ratio of between 1.2:1 to 2:1.

9. The reinforced composite material of claim 1, wherein the at least one cured polyester resin has flexural toughness greater than 3 Joules when tested in a standard flexure test, the test piece having dimensions 100 mm in length, 15 mm in width and 5 mm in thickness.

10. The reinforced composite material of claim 1, wherein the reinforced composite material has flexural toughness greater than 3 Joules for up to 5 years.

11. The reinforced composite material of claim 1, wherein the reinforced composite material comprises one or more of the following: i) a flexural modulus of greater than 3.5 GPa; ii) a flexural stress of greater than 120 MPa; or iii) an elongation at break of greater than 2%.

12. The reinforced composite material of claim 1, wherein the hydrophilic surface-modification of the reinforcing glass fibers: a) reduces catalyzation of resin polymerisation in the interphase when compared to a fiber not treated; or b) reduces embrittlement of said interphase when compared to a fiber not treated.

13. The reinforced composite material of claim 1, wherein the vinyl functional silane coupling agent of the second coating is independently selected from the group consisting of methacryloxypropyl-trimethoxysilane, vinylbenzylaminoethylaminopropyl-trimethoxysilane, and vinyl-tris(acetoxy) silane.

Description

EXAMPLES

(1) The present invention will now be described with reference to the following examples which should be considered in all respects as illustrative and non-restrictive.

(2) Treatment of a Glass Fibre with a Hydrophilic Surface Coating

(3) 1. E-glass fibres were cut to an average fibre length of 3400 micron and then milled to an average length of 700 micron. 2. The milled glass fibres were cleaned using boiling water, with a strong detergent and with powerful agitation. The detergent was then rinsed from the fibres. 3. 1% w/w of methacryloyloxypropyltrimethoxysilane (Dow Z-6030) was suspended in water at pH 4 and the fibres added to the suspension. The resulting mixture was stirred vigorously at room temperature for 60 minutes. 4. The liquid was then drained from the glass fibres, leaving them still wet with the mixture. 5. The Z-6030-treated fibres were then redispersed in water at a pH of 7. 6. Separately, a solution of Z-6030 was reacted with trimetholylpropane (TMP) in the presence of a tin catalyst (eg tributyl tin) for 15-20 minutes at 110-120 C. to form a Z-6030-TMP adduct having a viscosity of about 1200-1500 cP. Methanol is evolved during the reaction. 7. The Z-6030 treated fibres were then reacted with the Z-6030-TMP adduct to provide a hydrophilic treated fibre. This was achieved by dispersing the Z-6030 treated fibres in water and adding the Z-6030-TMP adduct to the water at a concentration of about 2-3 wt % of fibres. The mixture was stirred together for approximately 10 minutes. The fibres were then separated and then centrifuged to remove excess water. The wet fibres were then dried, initially at 30 C. for 3-4 hours, and then heated to between 110 and 125 C. for 5-7 minutes. 8. Separately, an emulsion of polymer was prepared having 200 parts polymers, 100 parts acetone and 16.6 parts water. Preferably the polymer is a hydrophilic resin such as an unsaturated polyester. 9. The hydrophilic treated fibres were then compounded with the emulsified resin until evenly distributed in the rations of about 93 w/w % fibres and 7 w/w % emulsion. 10. The compounded fibre-emulsion mixture was then added to the base resin at approximately 10-45% fibre-emulsion to 90-55% resin.

(4) Table 1 provides flexural strength data for cured clear casts of the commercially available Derakane epoxy vinyl ester resin 411-350 (Ashland Chemicals). These test panels were prepared according to the manufacturers specifications and the resulted in flexural modulus averages about 3.1 GPa, the flexural stress at yield averages about 120 MPa, and the elongation at break averages between about 5 to 6%.

(5) Table 2 shows similar test panels to those of Table 1 but having been thermally aged. Panels are thermally aged by heat treatment at 108 C. for two hours follows by controlled cooling to below 40 C. over about 2 hours. As can be seen, within experimental error, the flexural modulus and flexural stress are about the same post aging. However, the elongation at break has approximately halved, meaning that the panels have substantially embrittled with accelerated aging.

(6) TABLE-US-00001 TABLE 1 Flexural strength data for cured (un-aged) clear casts of Derakane 411-350 Epoxy Vinyl Ester Resin. Flexural Modulus Flexural Stress at Elongation at Composite (GPa) Yield (MPa) Break (%) Test Panel 1 2.98 112 4.9 Test Panel 2 3.12 119 5.7 Test Panel 3 3.11 123 5.6 Test Panel 4 3.28 132 6.0

(7) TABLE-US-00002 TABLE 2 Flexural strength data for aged clear casts of Derakane 411-350 Epoxy Vinyl Ester Resin. Flexural Modulus Flexural Stress at Elongation at Composite (GPa) Yield (MPa) Break (%) Test Panel 5 3.30 117 3.0 Test Panel 6 3.40 121 3.1 Test Panel 7 3.10 131 4.1 Test Panel 8 3.20 123 3.6 Test Panel 9 3.20 127 4.2

(8) Table 3 provides flexural strength data for aged cured clear casts of Derakane epoxy vinyl ester resin with various polymer additions (discussed below). As can be seen, the resulting flexural modulus averages about 3.3 GPa, the flexural stress at yield averages about 135 MPa, and the elongation at break averages between about 5 to 7%. Comparing the elongation data between Tables 2 and 3 it can be seen that the various polymer additions have substantially reduced aged embrittlement.

(9) TABLE-US-00003 TABLE 3 Flexural strength data for aged clear casts of Derakane 411-350 Epoxy Vinyl Ester Resin having 12-15 wt % of a polymer additive. Flexural Modulus Flexural Stress at Elongation at Composite (GPa) Yield (MPa) Break (%) Test Panel 10 + 3.20 132 6.7 polymer 1 Test Panel 11 + 3.20 131 4.9 polymer 2 Test Panel 12 + 3.30 136 5.7 polymer 3 Test Panel 13 + 3.50 140 6.0 polymer 4 Test Panel 14 + 3.60 146 6.6 polymer 5

(10) The polymers provided in the tables are the condensation products of a polyol and a diacid. The polyol's and diacid's comprising each polymer are provided in Table 4. These polyesters are generally prepared by heating approximately equimolar amounts of diol and acid at temperatures in excess of about 200 C. for periods of about 4 to about 12 hours. Most of the unsaturation is present as fumarate diester groups. These polyesters have acid numbers in the range of from about 15 to about 25. (The acid number is the milligrams of potassium hydroxide needed to neutralize one gram of sample).

(11) A 3-liter, round-bottomed flask equipped with a paddle stirrer, thermometer, an inert gas inlet and outlet and an electric heating mantle. The esterification reactions were conducted in 2 stages. The first stage was reacting the saturated acids in excess glycol, and the second stage was carried out with the addition of the unsaturated acids and remaining glycols. The reactor vessel was weighed between the stages and glycols were added if needed to compensate for any losses. The mixture was heated to between 150 and 170 C. such that water was liberated and the condenser inlet temperature was greater than 95 C.

(12) During the next 2-3 hours the temperature of the mixture was raised to 240 C. The mixture was then cooled to 105 C. and blended with inhibited styrene. The final polyester resin contained 80 percent by weight of the unsaturated polyester and 20 percent styrene.

(13) TABLE-US-00004 TABLE 4 Polyesters used to modify the Derakane base resin in Tables 3 and 5. ratio of saturated to Polymer polyol diacid unsaturated acids Polymer 1 propylene glycol 4 terephthalic acid 2 3:2 moles, MP-diol 1.5 moles, isophthalic moles acid 1 mole, fumaric acid 2 moles Polymer 2 diethylene glycol 5.5 terephthalic acid 3 3:2. Also, a 0.5M excess moles moles, fumaric acid 2 glycol was maintained at moles the commencement of the second stage Polymer 3 diethylene glycol 6 1,4-cyclohexane 4:3 moles, MP-diol 1.5 diacid, fumaric acid moles Polymers 4 Nuplex 316/ and 7 Terephth 50/50 blend Polymer 5 neopentyl glycol 6.25 1,4-cyclohexane 3:2 moles, propylene diacid 4.5 moles, glycol 2 moles fumaric acid 3 moles Polymer 6 diethylene glycol 1,4-cyclohexane 3:2 diacid 3 moles, fumaric acid 2 moles Polymer 8 neopentyl glycol 6.25 1,4-cyclohexane 4:3 moles, propylene diacid 4 moles, glycol 1 mole fumaric acid 3 moles

(14) Table 5 provides flexural strength data for Derakane epoxy vinyl ester resin having the stated ratios of resin to glass fibre (in brackets) wherein the glass fibre is treated only with the Z-6030 coupling agent.

(15) TABLE-US-00005 TABLE 5 Flexural strength data for aged Z-6030 treated glass fibres in Derakane 411-350 epoxy vinyl ester resin. Flexural Modulus Flexural Stress at Elongation at Composite (GPa) Yield (MPa) Break (%) Test Panel 15 6.20 124 0.87 (2.3:1) Test Panel 16 6.70 129 0.70 (2:1) Test Panel 17 7.50 135 0.63 (1.9:1) Test Panel 18 8.10 142 0.60 (1.7:1) Test Panel 19 9.00 149 0.58 (1.6:1)

(16) Table 6 shows flexural strength data for aged test panels of Derakane epoxy vinyl ester resin having about 12-15 weight % of a polymer additive as described above and 45-50 weight % of a treated glass fibre according to the present invention.

(17) TABLE-US-00006 TABLE 6 Flexural strength data for aged Derakane 411-350 epoxy vinyl ester resin having 12-15 wt % of a polymer additive and 47 wt % of treated glass fibre Flexural Modulus Flexural Stress at Elongation at Composite (GPa) Yield (MPa) Break (%) Test Panel 20 + 6.10 136 2.6 polymer 5 Test Panel 21 + 6.20 133 2.2 polymer 6 Test Panel 22 + 5.90 129 2.9 polymer 6 Test Panel 23 + 6.00 134 3.1 polymer 7 Test Panel 24 + 6.20 135 3.4 polymer 8
according to the present invention, wherein the treatment comprises the hydrophilic surface coating and the emulsified polymer.

(18) In the comparison of the flexural data provided in Table 5 and Table 6, it can be seen that the test panels 20-24 according to the present invention have significantly improved the elongation at break for aged panels, providing a reduction in aged embrittlement.

(19) Table 7 provides flexural strength data for aged test panels of Derakane epoxy vinyl ester resin having the stated ratios of resin to glass fibre (in brackets) wherein the glass fibre is treated with a monomer deficient resin. Test panel 25 is uncoated and panels 26 to 28 are coated. Panels having the coated glass fibre show significantly improved toughness.

(20) TABLE-US-00007 TABLE 7 Flexural strength data for aged test panels of Derakane 411-350 epoxy vinyl ester resin having a polymer treated glass wherein the polymer is a monomer deficient resin. Flexural Modulus Flexural Stress at Elongation at Composite (GPa) Yield (MPa) Break (%) Test Panel 25 6.20 124 0.87 (2.3:1) Test Panel 26 3.80 120 4.0 (5:1) Test Panel 27 3.50 115 4.0 (5:1) Test Panel 28 3.60 118 4.0 (5:1)

INDUSTRIAL APPLICABILITY

(21) The present invention is useful in a wide variety of industries, including: construction, automotive, aerospace, marine and for corrosion resistant products. The reinforced composite material of the invention provides improved long-term mechanical properties compared to traditional glass fibre reinforced materials.

(22) Although the invention has been described with reference to specific examples, it will be appreciated by those skilled in the art that the invention may be embodied in many other forms.