Study On Processes And Properties Of Continuous Woven Roving Reinforced Polyurethane Composites

The high chemical reactivity of isocyanate with water in the atmosphere can result in a number of side reactions during the process which increasing difficulties in the development of woven roving reinforced polyurethane composites, compared with the general thermosetting composites, the type and length of fiber used in fiber reinforced polyurethane composites remains to be widened. The main selection of reinforcing materials in domestic and others countries were short fiber, long fiber, carpet which impregnated in short time, but the use of continuous fiber fabric as a reinforcing material with superior properties, continuous fiber fabric should be developed as a reinforcing material of Polyurethane Composites. Therefore, the study of polyurethane composites manufacture technology is a very important task, the paper explores the feasibility of using hand lay-up(HL), compression molding(CM) and vacuum infusion(VI) molding process to manufacture E-glass fiber woven roving reinforced polyurethane composites as well as the mechanical properties and electrical properties by the three different molding process.In this paper, selecting modified PEG/TDI and modified PEG/MDI polyurethane as the matrix resin to manufacture polyurethane composites. At 25℃, initial viscosity of modified PEG/TDI polyurethane was 85 mPa·s, modified PEG/MDI polyurethane was 229 mPa·s, from the viscosity-time curve, we can see that the fluidity of both two types polyurethane can meet the three different molding process requirements.For both modified PEG/TDI and modified PEG/MDI polyurethane, coefficient of variation (CV) about mechanical properties of composites manufactured by the three process were below 8%. Narrow CV showed repeatability of the experimental results. It also demonstrated that HL, CM and VI processes have feasibility and stability in manufacturing E-glass fiber woven roving reinforced modified PEG/TDI and modified PEG/MDI polyurethane composites. On mechanical properties, there hadn't any phenomenon of foaming appeared during using the three different process manufacture modified PEG/TDI and modified PEG/MDI polyurethane composites. The flexural properties and tensile properties also significantly increased compared with neat polyurethane. For the modified PEG/TDI polyurethane composites, the VI composite gained better flexural and tensile properties than HL and CM composites, it showed that the higher fiber content, the greater flexural strength and flexural modulus. For the modified PEG/MDI polyurethane composites, higher polyurethane mass fraction of HL composite lead to greater bending strength than that CM and VI composite. But the CM and VI composites had superior flexural modulus, which is attributed to the relatively high fiber mass content in CM and VI process. The tensile properties of VI process modified PEG/MDI polyurethane composites is superior to HL and CM composites.On electrical properties, the fiber mass content of composites influences the polarization of the material, higher fiber mass content will reduce polarization, impact dielectric constant of materials. Moreover, because of the presence of glass fiber, the heat and energy consumption of materials reduced. Higher fiber mass content leads to lower dielectric loss. Therefore, using HL, CM, VI process obtained the modified PEG/TDI and modified PEG/MDI polyurethane composites lead the surface resistivity and volume resistivity decreased, the resistance rate decreased with fiber mass content increases. Ascribe to the existence of woven roving in the modified PEG/TDI and modified PEG/MDI polyurethane composites, thermal conductivity increased and the time of "carbon tracking" required was extend, the carbonized component was also reduced, the composites gained greater arc resistance than neat polyurethane.