Studies on Polysiloxane-based Alicyclic Episulfide Resin |
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Authors: | Xiaokang Lan Chengyuan Shang Wei Huang Yunzhao Yu |
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Institution: | 1. Institute of Chemistry, Chinese Academy of Sciences , Beijing, P.R. China;2. Graduate University of Chinese Academy of Sciences , Beijing, P.R. China;3. Institute of Chemistry, Chinese Academy of Sciences , Beijing, P.R. China |
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Abstract: | The polysiloxane-based alicyclic episulfide resin (PSCER) was synthesized through substitution of oxygen atoms in 1,3-bis2-(3{7-oxabicyclo4,1,0]hepyl})ethyl]-tetramethyldisiloxane with sulfur atoms using potassium thiocyanate (KSCN) as the reagent. The product was purified by column chromatography, and the by-products were isolated. It was found by 1H-NMR and 13C-NMR that the by-products were cycloolefins formed by desulfurization of the episulfide groups. PSCER was unstable; desulfurization took place easily, especially at high temperatures. The PSCER resin could not be cured with methylhexahydrophthalic anhydride (MeHPPA). When m-phenylenediamine or isophorondiamine was used as curing agent, PSCER showed a higher reactivity compared with the parent epoxide. However, the reactivity of the alicyclic episulfide was much lower than the polysiloxane based aliphatic episulfide for the steric hindrance of the six member ring. Desulfurization took place upon curing of the alicyclic episulfide resin, therefore the cured resin showed poor mechanical properties. Thermal stability of cured PSCER resin was also poor on account of low bonding energy of C-S and crosslinking density. |
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Keywords: | Alicyclic episulfide polysiloxane desulfurization stability reactivity |
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