| Organic-inorganic hybrid composites are normally considered to be a new generation of high-performance materials due to the combination of the advantages of inorganic materials with those of organic polymers. Polyhedral oligomeric silsesquioxane(POSS) was a new class of three-dimensional cage-like hybrid materials, contained an inorganic Si-O-Si core surrounded by organic groups. It possessed excellent properties such as symmetrical homogeneity, heat retardant,environmental safety as well as good compatibility, etc. Now, it is becoming one of the increasingly popular topics.In POSS technology, various kinds of reactive or polymerizable POSS molecules have been employed to polymers by grafting, blending, copolymerization or cross-linking in order to afford organic-inorganic composites. The addition of the POSS derivatives into polymeric materials can result in dramatic improvements in polymer properties, which include, but are not limited to, increase the mechanical properties, flame retardance thermal stability and the three-dimensional network structure, etc.In the present dissertation, octaphenyl polyhedral oligomeric silsesquioxane(OPS)was synthesized by the hydrolytic condensation reaction of phenyltrichlorosilane in benzene solvent. Then, phosphorus-containing trisilanol POSS was obtained from TPOSS after the corner-opening reaction of OPS. After that, different content of TPOSS and DPTPOSS were mixed with RTV to investigate the comprehensive properties of these composites, respectively. Three aspects of the main results obtained in this paper were included as follows:(1) OPS, TPOSS and DPTPOSS were successfully synthesized by the hydrolysis condensation reaction, corner-opening reaction and the condensation reaction,respectively. A combination of nuclear magnetic resonance(NMR), Fourier transform infrared(FTIR) spectroscopy, X-ray diffraction(XRD), scanning electron microscopy(SEM), and thermogravimetric analysis(TGA) were used to characterize the structure and properties of three types of POSS.(2) The composites which contained POSS was obtained by incorporation TPOSS into RTV via physical blending. Properties of RTV/TPOSS composites such as tensile strength, swelling behavior, thermal stability, flame retardance and LOI were researched and compared. The results showed that TPOSS was beneficial for forming the effective three-dimensional networks in RTV. Tensile tests revealed that the tensile strength of RTV/TPOSS-3 was 20% higher than that of pure RTV. As 9% of TPOSS was added, the lowest horizontal and vertical burning rate was obtained, decreased by65.8% and 41.4%, respectively. And the highest residue and LOI value was also acquired, increased 27.5% and 4%, respectively.(3) The RTV/DPTPOSS composites were prepared and analyzed by the similar way as presented in step(2). The performance was compared with that of RTV/TPOSS composites. Results showed that DPTPOSS/RTV composites were more conducive to increase the effective three-dimensional networks and the tensile strength. However,the thermal stability performance was slightly lower than the same mass fraction of TPOSS modified RTV. RTV/DPTPOSS-9 composites exhibited better flame retardant efficiency than RTV/TPOSS-9. The horizontal and vertical burning rate reduced by83.9% and 39.5%, respectively. The LOI was increased of 5.2% compared with that of pure RTV. Additionally, it is worthy to note that with the addition of DPTPOSS, the smoke emission reduced. It showed that DPTPOSS as a P-Si based composite flame retardance possessed good flame retardant effect when the addition of DPTPOSS was small, and it can also be used as a coupling agent to improve the compatibility between the substrate and the inorganic filler. |
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