| Phenolic resin (PF) is a kind of widely used adhesives. With the development of aerospace, automobile and electronics industry, people put forward new requirements on the properties of phenolic resin adhesive, so the modified phenolic resin adhesive becomes an important research direction. Polyborosiloxane is a kind of high temperature resistant material, which can be used to improve the thermal stability of the modified polymers. In this paper, we synthesized several polyborosiloxanes containing phenylene units (PBSP) and polytitanoborosiloxanes (TiBSi), and used them to modify PF, aiming to improve the heat resistance and adhesive properties of PF. The main contents of this paper include:(1) PBSPs were synthesized through direct polycondensation from phenyltrimethoxysilane (PTMOS), boric acid (BA) and hydroquinone (Ph(OH)2) in diethylene glycol dimethyl ether. The PBSPs obtained were characterized by gel permeation chromatography (GPC), FT-1R spectroscopy, NMR and TGA. GPC and TGA characterization indicated that when the molar ratio of H3BO3, PTMOS and Ph(OH)2 was 1:2:0.25, the molecular weight and residual rate of the PBSPs were the highest. The Mn was 1668 and the char yield at 800℃ in N2 was 75.09%. The FT-IR and NMR characterization showed that B element was introduced into the molecular structure by forming B-O-Si linkages. At the same time B-O-B and Si-O-Si linkages were also formed.By curing the PBSP-1 with PF under several different mass ratios, PBSP-modified phenolic resins (PBSP/PF) were prepared. The PBSP/PF cured was characterized by shear test, TGA, FT-IR, scanning electron microscope (SEM). The results of shear test and TGA indicate that when the mass ratio of PBSP and PF was 1.5:1, the residual rate of the PBSP/PF at 800℃ was the highest, while the tensile strength remains unchanged. From SEM, we can see that the cured PBSP/PFs exhibited sea-islands morphology. PBSP/PF ceramics were also characterized by FT-IR spectroscopy, Raman,29Si MAS NMR, 11B MAS NMR and EDX. EDX analysis indicates that four elements in the ceramics. That is Si, B,O and C, SiBOC ceramics were formed.(2) TiBSi was synthesized through polycondensation from linear PF, a polyborosiloxane, and a butyl titanate chelate, which was formed by adding acetylacetone into tetrabutyl titanate. The TiBSi obtained were characterized by GPC, FT-IR spectroscopy and TGA. The analysis results indicated that the amount of tetrabutyl titanate had little influence on the molecular weight, thermal weight loss and structure of TiBSi.By curing the TiBSi with phenolic resin (PF) under several mass ratios, TiBSi-modified phenolic resins (TiBSi/PF) were prepared. The cured TiBSi/PF was characterized by shear test, TGA, FT-IR and SEM. The results of shear test and TGA indicated that the tensile strength were all improved a lot than pure PFs, the most increasing by nearly 60%, while the residual rate of the TiBSi/PF at 800℃ was improved only a little. TiBSi/PF ceramics were also characterized by FT-IR spectroscopy, Raman,29Si MAS NMR, 11B MAS NMR and EDX. EDX analysis indicates that five elements in the ceramics. That is Ti, Si, B,O and C. The structures are mainly built by SiO4, B-O-Si, TiO2 and Si-O-C units. |
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