Abstract
The role of Aerosil silicas, A90, R812, R812s on the complex dynamic viscosity η* of methyl-vinyl polysiloxane MVQ at processing temperature 80°C was analyzed based on experiments with a torsional rheometer Rubber Process Analyzer RPA. The influence of surface area and surface activity on the Payne’s effect was determined by oscillating rheometer Ares G2. The decrease in complex modulus G* by increasing strain for silicas R812, R812s was mostly due to the breaking down of filler-filler networking, the modification of surface led to better processability resulting in the increase of tensile strength TS, from 0.42 MPa unfilled silicone to 9.31 MPa MVQ containing R812. Higher surface activity of silica A90 caused a decrease in filler networking due to a better filler-polymer interactions, which resulted in the increase of the percentage of non-covalent crosslinks determined for samples treated with ammonia. The decrease of static water contact angle θ of silicone rubber after incorporation of A90 was observed. Influence of allylisobutylPOSS on curing, crosslink density, static and dynamic behavior of silicone rubber was considered.
Highlights
Polysiloxane “silicone” rubber is an elastomer containing siloxane bond of (Si-O) molecular structure as the main chains [1]
Surface covering with hexadimethylsilazane (HDMS) reduced the amount of silanol groups on the silica surface causing the decrease of the oil absorption parameter (OAP) for both hydrophobic silicas
In this paper three different silicas varied in surface area and surface characteristics were applied as reinforcement for peroxide cured silicone rubber MVQ
Summary
Polysiloxane “silicone” rubber is an elastomer containing siloxane bond of (Si-O) molecular structure as the main chains [1]. The synergistic effect between divinyl-hexa[(trimethoxysilyl)ethyl]POSS and fumed silica on thermal stabilities and mechanical properties of room temperature vulcanized (RTV) silicone rubbers was observed [13]. Three types of chemical reactions are possibly during peroxide curing, the crosslinking of methyl-vinyl silicone rubber MVQ, the polymerization of POSS molecules containing unsaturated >C=C< functional groups, the grafting reaction between POSS and polymer. In particular the influence of silica properties such as surface area, structure and surface activity and POSS grafting on the reinforcement mechanism, and Payne’s effect [17] were analyzed. The influence of production method, rubber type and the presence of additives such as solid particles on the hydrophobic properties and water contact angles of room temperature vulcanizing RTV silicone was observed [18], coatings containing silica filler indicated lower water contact angles. The effect of silica surface modification on the hydrophobic performance and air permeability of MVQ methyl-vinyl silicone elastomer was evaluated
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