| Silicone rubber is a kind of polymer material, combining properties of in-organics andorganics. It is widely used in modern industry with favorable performances of environmentalinert, heatproof stability, electric insulation, permeability and the like. With the developmentof science and technology, superior performances of silicone rubber are required. In order toconform to the requirement of Hygienic Standard of EU Food Contact Materials, we chosevinyl hydroxyl silicone as a novel structure control agent to decrease volatiles from the rubber.Simultaneously, adhesive property and resistance to yellowing were modified by adding TS,which was synthesized with hydrogen-containing silicone oil and TAIC in our laboratory. Themain investigation on preparing high temperature vulcanized silicone rubber was presented inthis study. The main content was concluded as following:(1) The main components of high temperature vulcanized silicone rubber is consisted ofsilicone rubber, fortifier, constitution controller and vulcanizator. Through experimentalcomparisons, composites containing100phr methyl vinyl silicone rubber as matrix,40phr sil-icon dioxide as filler,5phr hydroxyl silicone oil and0.6phr DBPH were determined to formthe formulation. Among them, hydroxyl silicone oil acts as constitution controller and DBPHas vulcanizator. We also investigated the preparation process of this gross rubber.(2) TS was synthesized according to addition reaction of Si-H from hydrogen siliconeoil and TAIC under Platinum catalyst. Optimum preparing condition of TS is presented below.2g TAIC was slowly dropped into6g hydrogen silicone oil(hydrogen content1.1%) at thedropping rate of10-15min-1under stirring rate at500rï¹'min-1at temperature between60-70℃. The carbon-carbon double bonds from TS can increase radical and activecross-linked points for the high temperature vulcanized silicone rubber. Strength of the rubberis, therefore, enhanced with the increase of cross-linking density attributed to the high proba-bility of coupling crosslink. SEM photographs shows that the destroyed mode of spicing in-terface between gross rubber and nylon board was from the interface failure to mixed failureand then to cohesive failure. These phenomena indicate that TS containing–NCO groups canremarkably improve the cohesion mechanical. Partial reducible hydrogen left from Si-H addi-tion reaction effectively inhibits the rubber from yellowing causing by oxidization of impuri- ties. As the additive content of prepared TS is3phr, the hardness of Shor A, tensile strength,tear strength, elongation at break, cohesion strength and whiteness was51.5°,7.8MPa,17.5KN/m,420%,2.2MPa and75%, respectively.(3) Vinyl hydroxyl silicone oil was used as a novel constitution controller for this hightemperature vulcanized silicone rubber. Because-CH=CH2group participated in the curingreaction of silicone rubber. In addition, low molecular volatile emerging from the oil whenheated was suppressed due to hydrogen bonding interaction between silicone oil hydroxylgroups and silica hydroxyl groups in surface, thus decreased volatile from silicone rubber.While the additive content of vinyl-hydroxyl silicone oil was7phr, optimum performances ofthe silicone rubber were attained. The stiffness of the vulcanized rubber was52°, as well astensile strength8.0MPa, tear strength21.5KN/m, elongation at break475%. Volatile mattercontent and extractive content was respectively decreased to0.3%and1.62%. Hygiene indexreached the Health Standard of EU2002/72/EC. |
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