The Effect Of Hot Pressing Molding Conditions On The Properties Of PI/namo-SiO₂ Composite Materials

Polyimide?PI?is a kind of important chemical material with excellent heat resistance,good dimensional stability and dielectric properties,finished product of it has been widely used in the automotive,electronics,aerospace and other fields.But pure polyimide has poor abrasion resistance,low tensile strength,in order to overcome the above shortcomings,to improve its mechanical and tribological properties often by inorganic nanoparticles modified PI,however,the effect of molding conditions on the performance of the PI/SiO₂ composite rarely explored.This paper through the orthogonal test study the influence of compression molding parameters on the different content of SiO₂?0%,5%,10%?of the polyimide/silica?PI/SiO₂?composite material performance,temperature,pressure,holding time and heating rate as the four factors of orthogonal test,the tensile strength,elastic modulus,friction coefficient and wear rate as the evaluation index.Then,considering the experimental evaluation index,the optimum forming conditions of PI/SiO₂ composites with different SiO₂ content were obtained.The results show that for PI/SiO₂ composite with SiO₂ content of 5%,the heating rate is the main factor affecting it's tensile strength,contribute to the improvement of the tensile strength of the low heating rate,pressure is the main factors affecting the elastic modulus,increasing pressure leads to elastic modulus decreased first and then increased;and the temperature is the main factors affecting the friction coefficient and the wear rate,increasing temperature is helpful to improve the friction performance of PI/SiO₂;the comprehensive influence of molding conditions on the properties of PI/SiO₂,the best molding conditions of SiO₂ content of PI/SiO₂ composite material for 5% is: temperature is 380? and the pressure of 2t,holding time 1.5h,the heating rate of 1?/min.The content of SiO₂ increased?10%?,main effecting factors of elastic modulus,friction coefficient and wear rate is heating rate,pressure and holding time;the best molding conditions is: temperature is 370?,pressure is 1t,holding time is 0.5h,the heating rate is 1.5?/min.Compared with PI/SiO₂ composites,the optimum forming conditions of pure PI as follows: temperature is 370?,pressure is 1.5t,holding time is 1.5h,heating rate is 1?/min.The main factors affecting the tensile strength and elastic modulus is holding time,the main factors affecting the friction coefficient and wear rate is the pressure and the heating rate.