Preparation And Properties Of PP/PP-g-VTMS/methyl Silicone Rubber For High Frequency Transmission

With the development of the times,high-frequency transmission technology has been applied to various scenarios in work and life.The realization of this communication technology will rely more on new materials than ever before.This is mainly due to its characteristics of ultra-high frequency transmission,ultra-low delay,and great attenuation,which determines that new materials need to have low dielectric constant and the characteristics of low dielectric loss.At present,low-dielectric,low-loss high-frequency communication materials at home and abroad are mainly polypropylene（PP）-based materials;PP has good electrical insulation properties,mechanical properties,and high cost performance,but under high-frequency transmission conditions,it has higher requirements for its dielectric properties,mechanical properties,and aging resistance.Therefore,the modification of PP to further improve its dielectric properties and thermal decomposition properties has become a focus of research.Based on this,this paper uses PP and vinyl trimethoxy silane（VTMS）for graft modification and uses it as a compatibilizer to study the dielectric properties,mechanical properties,thermal stability and compatibility of PP/polypropylene grafted vinyl trimethoxy silane（PP-g-VTMS）/methyl silicone rubber lay a good foundation for the preparation of special materials for high-frequency transmission.In this paper,an orthogonal design was used to prepare PP-g-VTMS by the melting method,and infrared spectroscopy was used for characterization.At the same time,the dielectric and mechanical properties of PP-g-VTMS were studied.The results show that the best formulation of PP-g-VTMS is 0.1 wt%of dicumyl peroxide（DCP）,6 wt%of VTMS,the molar ratio of styrene（St）and VTMS is1.5:1,the grafting process is the experimental temperature of 180℃,the rotation speed is 50 r/min,the experiment time is 10 min,the grafting rate obtained at this time is 3.54%;through the analysis of infrared spectrogram,the characteristic absorption peak of Si-O bond appears at 1023 cm^-1,indicating that VTMS is grafted onto PP;as the grafting rate increases,the dielectric constant and dielectric loss of PP-g-VTMS first decrease and then increase,and the tensile strength and elongation at break first increase and then decrease.When the grafting rate of PP-g-VTMS was 2.68%,the dielectric constant and dielectric loss of PP-g-VTMS were reduced by 0.43%and 3.9%respectively compared with pure PP.The dielectric properties,mechanical properties,thermal stability,crystallization properties and compatibility of PP/PP-g-VTMS/methyl silicone rubber have been studied.The results show that:（1）The grafting rate of PP-g-VTMS at 2.68%,with the increase of PP-g-VTMS content,the dielectric constant of the composite material first decreases and then increases,the dielectric loss first decreases and then increases and then decreases,the tensile strength first decreases and then increases,and the elongation at break first After rising,the crystallization temperature（T_c）increased from 121.83℃to 123.33℃,and the melting temperature（T_m）decreased from 168.14℃to 166.67℃,crystallinity decreased by 22.13%.At the same time,theβdiffraction peak at 16.0°increased with the content of PP-g-VTMS.The increase of sulphate shows a downward trend,and the crystallinity decreases.（2）With the increase of methyl silicone rubber content,the dielectric constant of the system does not change much.The dielectric loss first increases and then decreases and then increases.At high frequencies,the dielectric loss is reduced by 54.27%compared with pure PP;The tensile strength showed a downward trend,and the elongation at break increased first and then decreased;and the decomposition temperature of the system rose from 347.7℃to 349.81℃;at the same time,the phase of PP and methyl silicone rubber in the system the capacity becomes better.The effect of PP/PP-g-VTMS/methyl silicone rubber on its water resistance,dielectric properties,mechanical properties and crystallization properties in the presence of warm water has been further studied.The results show that as the time of the composite material in water increases,its water absorption rate increases slowly and tends to be stable;its dielectric constant first decreases and then increases,and the dielectric loss first increases and then decreases.At high frequencies,the dielectric constant decreases by 0.59%compared to before warm water treatment.Compared with the warm water treatment,the loss increased by5.5%;the tensile strength first decreased and then increased,and the elongation at break showed an upward trend;at the same time,theαdiffraction peaks at14.0°,16.8°and 18.5°gradually decreased,and the crystallinity decline.