Study On Preparation And Performance Of Addition Type Liquid Silicone Rubber Foam

Liquid silicone rubber materials have excellent high and low temperature resistance,electrical insulation,aging resistance,biocompatibility and other properties,and are widely used in high-speed rail,automotive,mother and child,medical,cable and other fields.With the frequent occurrence of fire,people pay more and more attention to the flame retardant composites.Since the combustion decomposition products of silicone rubber are Si O₂,CO₂,H₂O,etc.,which have minimal environmental pollution,the preparation of liquid silicone rubber flame retardant foam is of great research significance.In this paper,vinyl silicone oil(Vi-PDMS)as the base rubber,hydrogen-containing silicone oil(PMHS)as the cross-linking agent,hydroxy silicone oil(Hy-PDMS)as the foaming additive,silica as the reinforcing filler,and nitrogen and phosphorus flame retardants were added,and the dehydrogenation and condensation reaction occurred under the action of platinum catalyst to prepare the liquid silicone rubber flame retardant foam material.The effects of each component on the comprehensive performance of the additive liquid silicone rubber foam were investigated by electronic tensile machine,mass spectrometer,scanning electron microscope(SEM),rotational rheometer,horizontal and vertical combustion instrument,limiting oxygen index instrument,Fourier infrared spectrometer(FTIR),and thermogravimetric analyzer(TGA).(1)The optimal formulation was derived by studying the effects of the amounts of the basic components catalyst,Hy-PDMS,silica,PMHS,Vi-PDMS and the viscosity of Vi-PDMS on the mechanical properties and pore morphology of the additive liquid silicone rubber foam.The results showed that the increase of catalyst dosage accelerated the reaction speed of vulcanization and foaming,accelerated the formation of three-dimensional network structure,and increased the tensile strength of the samples.Hy-PDMS and PMHS were two important factors to regulated the matching of foaming reaction and cross-linking reaction,and the foaming multiplicity of the samples has reached 1.88 times and the permanent deformation in compression was as low as 3.4%when the matching of foaming reaction and cross-linking reaction was better.The 25%compressive stress test and tensile test showed that the addition of silica was beneficial to the improvement of the mechanical properties of the samples,and it was observed by SEM test that the addition of silica helped to form more dense and fine bubble pores.In addition,the addition of a certain amount of low-viscosity Vi-PDMS increased the vinyl content of the system,which was increased the cross-link density of the system and improved its mechanical properties,and also effectively reduced the viscosity of the rubber,which was conducived to the subsequent preparation of flame retardant silicone rubber materials by adding more other fillers.(2)By studyed the effects of flame retardant addition on the mechanical properties,rheological properties,flame retardant properties,pore shape and thermal stability of the additive liquid silicone rubber flame retardant foam,we prepared liquid silicone rubber flame retardant foam products with excellent overall performance.The rheological test showed that the non-Newtonian index of silicone rubber was less than 1,which was a pseudoplastic fluid.Through compression stress tested and tensile tested,it could be obtained that the mechanical properties of the products increased firstly and then decreased with the increase of flame retardant,and the mechanical properties were best when the addition amount is 50 phr,and the oxygen index of the sample reached 28.2%at this time,and the combustion grade of the sample reached V-0 grade according to the vertical combustion test standard.The analysis of TGA and FITR showed that the flame retardant started to decomposed at about 300?,and almost completely decomposed at600?,when Si-O has not yet decomposed,which showed the high temperature resistance of the main chain of silicone rubber,and the addition of flame retardant made the overall thermal stability of silicone rubber products worse,but the flame retardant performance was improved.