| Due to its unique structure of Si-O-Si main chains,silicone rubber has excellent electrical insulation,weather resistance,hydrophobicity and recovery of hydrophobicity.Therefore,silicone rubber has been widely used in the field of high voltage insulation.However,with the deteriorating environment and the increasing voltage level,silicone rubber tends to suffer from tracking and erosion damage during long-term use,leading to insulation failure.Thus,the security of the power transmission system is seriously threatened.Therefore,it’s of great theoretical significance and application value to study high performance silicone rubber with superior tracking and erosion resistance.In our work,γ-piperazinylpropylmethyl dimethoxysilane（HD-110）with excellent oxidation resistance was selected as the anti-tracking additives.The effect of mixing sequences and content of HD-110 on the tracking and erosion resistance and thermal stability of silicone rubber was investigated,and the suppression mechanism of HD-110 on the tracking and erosion of silicone rubber was also discussed.Then,polysiloxane containing piperazinyl and vinyl was synthesized as anti-tracking additives,and silicone rubber with excellent tracking and erosion resistance,good mechanical properties,water resistance and recovery of hydrophobicity was prepared.The main research contents and results are as follows:（1）γ-Piperazinepropylmethyl dimethoxysilane（HD-110）was introduced into silicone rubber containing platinum catalyst by two different mixing sequences.One sequence was adding HD-110 in the preparation of silicone rubber masterbatch（SR-1）,and the other was adding HD-110 in the preparation of silicone compound（SR-2）.The effect of mixing sequences of HD-110 on the tracking and erosion resistance was investigated.The results showed that HD-110 could significantly improve the thermal stability and tracking and erosion resistance of silicone rubber.Especially,SR-1 could pass the 1A 4.5 grade with the eroded mass ratio of 0.35wt%,which was much less than the 5.34wt%of SR-2.RPA and extraction resistance test revealed that HD-110 could easily condense with the Si-OH groups of silica when it was added in the preparation of silicone rubber masterbatch.This made the dispersion of silica in SR-1 more uniform and promoted the stability of HD-110 in silicone rubber.Therefore,under the continuous elution of conductive solution and the heat stress generated by dry-band arcing,HD-110 was stable enough to enhance the tracking and erosion resistance of silicone rubber.（2）The effects of HD-110 content on the thermal stability,flame retardancy,tracking and erosion resistance of silicone rubber were studied,and the suppression mechanism of HD-110on the tracking and erosion of silicone rubber was investigated by TG-FTIR and SEM-EDX.It was found that HD-110 content had a significant effect on the tracking and erosion resistance,thermal stability and flame retardancy of silicone rubber.When HD-110 content was 2phr,silicone rubber had the best comprehensive performance.Silicone rubber could pass the 1A 4.5 grade and the electrical eroded mass ratio was only 0.35wt%.The temperature of20wt%weight loss(T20)under air and nitrogen atmospheres increased from 489°C and 588°C of the control sample to 531°C and 676°C,respectively,and the residue at 800℃was increased from 47.5wt%and 46.7wt%of the control sample to 69.1wt%,respectively.The control sample burnt completely at the first ignition,whereas silicone rubber with 2phr HD-110 could self fire-extinguish,and formed a compact ceramic layer.TG-FTIR and SEM-EDX results showed that the addition of HD-110 promoted the cleavage of methyl to generate methane,and induced free radical crosslinking reactions to form a compact ceramic barrier,thereby protecting the inner silicone rubber from dry-band erosion and reducing the deposition of free carbon particles.Thus,the tracking and erosion resistance of silicone rubber was improved effectively.（3）Polysiloxane containing piperazinyl and vinyl（PPMVS）was synthesized with HD-110,octamethyl cyclotetrasiloxane（D4）,tetramethyltetravinylcyclotetra-siloxane(ViD4)and hexamethyldisiloxane（MM）under the catalysis of tetramethylammonium hydroxide pentahydrate（TMAH）.The results showed that PPMVS could significantly improve the thermal stability,tracking and erosion resistance of silicone rubber.When PPMVS content was 6phr,the residue of silicone rubber at 800℃under air atmosphere increased from 48.0wt%of control sample to 70.9wt%.Silicone rubber could pass the 1A 4.5 grade with the average eroded mass ratio of 0.47wt%,and had good water resistance.After soaked in water for 3days,silicone rubber could still pass the 1A 4.5 grade.In addition,PPMVS did not deteriorate the curing behavior and mechanical properties of silicone rubber. |
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