Preparation And Research Of Properties Of Silicone Sealant

One-component room temperature vulcanized silicone?RTV-1?was widely used in electronics,construction,transportation,machinery,aviation,medical and other industries.The use of catalyst in the preparation of RTV-1 can easily lead to instability of product quality and serious environmental pollution.In order to modify RTV-1 by self-made self-crosslinking?-silane coupling agent,which can avoid the use of catalyst in the preparation process and obtain the finished product with better overall performance.The?-chloromethyltrichlorosilanewasusedasrawmaterialtoobtain?-chloromethyltrimethoxysilane by alkoxylation.The structure was characterized by FT-IR and¹H NMR,which proved the existence of methoxy;?-chloromethyltrimethoxysilane was functionalized to obtain?-aminoethylaminomethyltrimethoxysilane??-792?,?-bis?aminoethyl?aminomethyltrimethoxysilane,?-methylacryloyloxymethyltrimethoxysilane??-570?,?-indolylmethyltrimethoxysilane??-590?and there were characterized by FT-IR,¹H NMR,¹³C NMR,which proved the existence of amino groups,ethylene groups,ester bonds and thiol groups,respectively.The hydroxy-terminated polydimethylsiloxane?PDMS?were modified by?-silane coupling agents and?-silane coupling agents,which showed that?-792,?-bis?aminoethyl?aminomethyltrimethoxysilane,?-570,?-590 owned different degrees of self-catalytic effect,while?-silane coupling agent does not,because the?-silane coupling agent silicon atoms and non-hydrolyzable groups only one methylene?-CH2-?,the distribution of the electron cloud of the hydrolyzed group can easily affect the removal of the hydrolyzed group,while the amino group is a strong electron donating groups,the acyloxy groups and the thiol groups are medium electron donating groups,so the time of the dry time of the?-aminosilane coupling agent is the most fast.The results showed that the cross-linking degree of rubber sample cross-linked by?-silane coupling agents were high than the?-silane coupling agents because Si-OH content was lower by FT-IR.TG showed that the heat resistance of PDMS autocatalytic cross-linked by?-silane coupling agent was obviously better than cross-linked by?-silane coupling agent,the temperature of 10%heat mass loss for the sample cross-linked by?-792,?-bis?aminoethyl?aminomethyltrimethoxysilane,?-570,?-590 were 402?,436?,465?,and 492?,respectively.The reason was that the PDMS crosslinked by?-silane coupling agent had a higher degree of cross-linking and cross-linked network;the temperature of 10%heat mass loss for the high-viscosity sample were 362?,365?,513?,and 495?,respectively.The heat resistance of high-viscosity samples were also higher than the low-viscosity samples.The reason for the high-viscosity PDMS had a large molecular weight,a long molecular chain,and more energy for breaking the molecular chain.The crosslinked PDMS samples were compounded by 500 parts by mass of PDMS,200parts by mass of fumed silica,300 parts by mass of simethicone and homemade?-silane coupling agent and self-purchased?-silane coupling agent.The oil resistance test results showed that the mass change rate and volume change rate of the cross-linked?-silane coupling agent were smaller than that of?-silane coupling agent.The volume change rates of the samples crosslinked by?-792,?-bis?aminoethyl?aminomethyltrimethoxysilane,?-570,?-590 were 1.2%,1.3%,0.8%,and 0.9%,respectively,the rate of change was small,demonstrating that there was no significant swelling or shrinkage in the oil environment;the change rate of tensile strength of rubber samples were 5.5%,5.8%,5.7%,4.4%,and the change rate of elongation at break were 76.5%,80.9%,81.1%,and 85.6%,respectively.It was proved that the tensile strength of the rubber samples impregnated into the engine oil slightly decreases,but the elongation at break increases obviously,because the deformability and the elongation at break increased as the plasticity became stronger.Hydrophobic test results showed that the new type of RTV-1 was hydrophobic material,and the quality of the samples were almost unchanged after immersion in water.When the ratio of filler to PDMS were 0.4 or 0.5,the corresponding static contact angles were 129°and131°,respectively.According to the SEM image,when the ratio of the filler was 0.4,the microstructure of the sealant surface was a uniform distribution of the filler and has a mastoid structure of 2 to 10?m,which was the main reason for the hydrophobicity.