Abstract
In this study, 2-(Diphenyl phosphino)ethyltriethoxysilane, (DPPETES) was blended with pristine epoxy or modified epoxy (DGEBA) to form a novel ladder-like phosphorus-containing polysilsesquioxane. Furthermore, by changing the blending ratio of phosphorus-containing polysilsesquioxane (PSSQ) to epoxy or modified epoxy, a series of nanocomposites have been prepared. The nanocomposites were predicted to exhibit excellent thermal stability. FT-IR, ATR, and XRD were used to characterize the reactivity and structure of the nanocomposite in this study. The cured hybrid composite structures of epoxy and modified epoxy with DPPETES and TEOS were investigated by 29Si-NMR. DSC, TGA, and LOI were utilized to analyze the thermal property of the nanocomposite in this study. Moreover, the thermal degradation kinetics and activity energy of curing have been calculated to confirm the high performance thermal properties. Moreover, the optical properties, morphology, physical properties etc. will be discussed. The optimum curing agent and the optimum DPPETES contents were also investigated. In this study, the polysilsesquioxanes particles were uniform dispersed at the molecular level in epoxy resin and that the sizes of polysilsesquioxanes particles were less than 100 nm. DDM was the optimum curing agent. The silicon atoms with different degrees of condensation were presented in epoxy system and modified epoxy system. The characterizations demonstrated that Q3 and Q4 structures were more dominated than T3 structure in epoxy system. However, the T3 structure was more dominated than Q3 and Q4 structure in modified epoxy system. From the kinetics analysis of curing reaction, the activation energies of curing of modified epoxy were higher than that in epoxy system and the optimum DPPETES content of curing reaction was 6 wt%. This study also found that either blended or chemical modified nanocomposites show excellent thermal properties. The nanocomposites of epoxy system (blending) possess excellent flame retardant property (LOI 30). The nanocomposites of modified epoxy (chemical modification) also exhibit excellent thermal stability properties including high char yield (30wt%), IPDT (955.19), low rate of degradation and high activation energy of degradation. The activation energies of degradation also increased with DPPETES contents. This study reveals that the optimum DPPETES content is 9 wt%. The XRD patterns show that the chain entanglement resulted in various nanocomponents were amorphous structure, and possessed high optical transparency. The UV/VIS measured for nanocomposites reveal no absorbance in the range of 450~800 nm, it possesses excellent optical transparency. This transmittance may be used as a criterion for identifying the formation of a homogeneous phase.