The effects of gamma irradiation on RTV polysiloxane foams

The present work involves the investigation of ionizing radiation effects on silica filled poly (dimethyl siloxane) foam vulcanized at room temperature. In order to better predict aging effects in these materials, it is important to understand the influence of irradiation on structural-rheological property relationships. Polysiloxane foams were subjected to moderate doses of gamma irradiation in an inert atmosphere and characterized by thermal (DSC and TGA), chemical (FT-IR, NMR, Mossbauer, mass spectroscopy, EPR, solvent swelling), microscopy (SEM and AFM), and mechanical (uniaxial compressive load) techniques. Radiation exposure induced cross-linking reactions that predominated over chain scission reactions for the dose range investigated. No long-lived radiation-induced radicals were detected and the porous structure of the irradiated foam remained unchanged. Radiation exposure resulted in gas evolution, decrease in crystallization levels, slight changes in chemistry, and decrease in the molecular weight between cross-links, thereby hardening the foam.

[1]  P. Flory,et al.  Statistical Mechanics of Cross‐Linked Polymer Networks I. Rubberlike Elasticity , 1943 .

[2]  B. Patterson,et al.  Mössbauer, NMR and ATR-FTIR spectroscopic investigation of degradation in RTV siloxane foams , 2007 .

[3]  A. R. Skinner,et al.  Physical & thermal properties of model polysiloxane rubbers: impact of crosslink density and tin concentration , 2002 .

[4]  A. Whittaker,et al.  NMR study of the gamma radiolysis of poly(dimethyl siloxane) under vacuum at 303 K , 2002 .

[5]  Andrew K. Whittaker,et al.  Radiation chemistry of poly(dimethyl siloxane) , 2000 .

[6]  R. Maxwell,et al.  Gamma radiation induced effects on silica and on silica–polymer interfacial interactions in filled polysiloxane rubber , 2006 .

[7]  M. Patel,et al.  Chain dynamics in foamed polysiloxane materials: Influence of the tin catalyst phase on material properties , 2014 .

[8]  A. Bueche.  An investigation of the theory of rubber elasticity using irradiated polydimethylsiloxanes , 1956 .

[9]  Claudia Sarmoria,et al.  Modelling molecular weight changes induced in polydimethylsiloxane by gamma and electron beam irradiation , 2008 .

[10]  E. L. Warrick,et al.  Effects of Radiation on Organopolysiloxanes , 1955 .

[11]  N. Billingham,et al.  Impact of thermal ageing on the tin catalyst species in room temperature vulcanised polysiloxane rubbers , 2004 .

[12]  P. Flory,et al.  STATISTICAL MECHANICS OF CROSS-LINKED POLYMER NETWORKS II. SWELLING , 1943 .

[13]  Wei Huang,et al.  A study on radiation resistance of siloxane foam containing phenyl , 2002 .

[14]  C. M. Roland,et al.  Crystallization of polydimethylsiloxane end-linked networks , 2000 .

[15]  A. Miller,et al.  Radiation Chemistry of Polydimethylsiloxane.1 I. Crosslinking and Gas Yields , 1960 .

[16]  C. G. Delides.  The protective effect of phenyl group on the crosslinking of irradiated dimethyldiphenylsiloxane , 1980 .

[17]  S. Chinn,et al.  Compression set in gas-blown condensation-cured polysiloxane elastomers , 2010 .

[18]  A. Bueche.  Interaction of polydimethylsiloxanes with swelling agents , 1955 .

[19]  A. Labouriau,et al.  Mössbauer and NMR characterization of tin octoate: Neat and residues in RTV foams , 2006 .

[20]  L. Mullins.  Effect of Stretching on the Properties of Rubber , 1948 .

[21]  A. Charlesby,et al.  Changes in silicone polymeric fluids due to high-energy radiation , 1955, Proceedings of the Royal Society of London. Series A. Mathematical and Physical Sciences.

[22]  R. Maxwell,et al.  The effects of γ-radiation on the thermal, mechanical, and segmental dynamics of a silica filled, room temperature vulcanized polysiloxane rubber , 2003 .

[23]  A. Bueche,et al.  Swelling and elasticity of irradiated polydimethylsiloxanes , 1959 .

[24]  Ahmed Ali Basfar,et al.  Hardness measurements of silicone rubber and polyurethane rubber cured by ionizing radiation , 1997 .

[25]  S. Lee,et al.  Method for Estimating the Chemical Crosslink Densities of Cured Natural Rubber and Styrene-Butadiene Rubber , 1994 .

[26]  K. Urayama,et al.  Multiaxial deformations of end-linked poly(dimethylsiloxane) networks. 2. Experimental tests of molecular entanglement models of rubber elasticity , 2001 .

[27]  A. Whittaker,et al.  Molecular weight changes and scission and crosslinking in poly(dimethyl siloxane) on gamma radiolysis , 2001 .