Structure And Performance Of Fiber Reinforced Silicone-containing Polyarylacetylene Composites

Silicone-containing polyarylacetylene (PSA) is a newly organic-inorganic hybrid thermosetting resin. A rigid structure of PSA is formed through high cross-linking reaction of arylalkynyl in PSA. The cured PSA has excellent heat-resistance. However, the inherent brittleness of the cured PSA is severe that influences the application in structural materials. Meanwhile, the low polarity of PS A declines the adhesion of PSA and fibers, and affects the mechanical property of fiber reinforced PSA composites. The attempt to improve the property of PSA by blending was carried out in this paper.Benzoxazine has some fascinating characteristics, such as molecular designability of flexibility, good thermal and mechanical properties. Firstly, four kinds of benzoxazines were synthesized to modify PSA. The properties of the modified PSA blended with benzoxazines (PSA/BZs) were studied by gel time, rheological behavior, dynamic mechanical analysis (DMA) and thermogravimtry analysis (TGA). A unidirectional T700carbon fiber (T700CF) reinforced PSA/BZs composites were prepared. The results show that the mechanical property of the PSA blended with benzoxazines with propargyl group are better than that PSA blended benzoxazines with terminal acetylene. However, the thermal performance of the PSA decreases with the increase of the benzoxazines content in PSA. The temperature of the cured PSA at the mass loss of5%(Td5) and the residual yield at800℃are599℃and84.9%, respectively. The Td5of the modified PSA decreases to589℃. The effect of addition of benzoxazines into PSA on the thermal stability of PSA is limited. However, the flexural property and interlaminar shear strength (ILSS) of the T700CF/modified PAS composites increase by16%(to1700MPa) and16%(to78MPa), respectively. The results show that the benzoxazines blended into PSA could enhance the interface adhesion between carbon fiber and PSA matrix. The glass transition temperature (Tg) of the T700CF/PSA/BZs composites does not display before500℃, and the storage modula of the composites increase with increase of the benzoxazines content in PSA under room temperature.Nickel acetylacetone and triphenylphosphine was used to catalyze the cure reaction of PSA and could reduce the cure temperature of PSA. The longer the shelf time of the impregnant of PSA with catalyst was, the lower the catalytic activity and the higher the cure temperature of the prepreg of the PSA was. However, the catalytic activity in the curing is still effective. Adding catalyst into the PSA matrix does not influence the mechanical property of T300carbon fiber plain cloth reinforced the catalyst-added PSA composite at room temperature or300℃. The flexural strength of the T700CF reinforced the PSA, catalyst-added PSA and PSA blended with benzoxazines composites retain62.7%,66.9%and47.4%at470℃, respectively.The curing behavior, shrinkage, surface energy, elements on surface, coefficient of thermal expansion (CTE) and morphology of microcrack of the PSA and PSA blended with benzoxazines matrices composites were studied to illustrate the possibility of improvement for PSA. P-appe, a benzoxazine with propargyl group reduces the surface energy of the cured PSA, increases the adhesion of fiber and resin matrix and decreases the CTE of the cured PSA so that the elimination of the microcrack of the fiber reinforced PSA composites occurs.Finally, the changes of the functional groups of the PSA and modified PSA were investigated with FTIR in situ monitoring during heating. The relationship of viscosity of PSA and temperature and time were also studied. The results show that the viscosity of PSA decreases remarkably with addition of P-appe. The lower viscosity of PSA is propitious to be used in resin transfer molding (RTM) process. The2.5D T300fabric reinforced PSA composites were prepared by RTM. The longitudinal flexural strength and ILSS of the modified PSA matrix composites increase by34.3%and57.1%, respectively.