Development And Application Of Ultrasonic Assisted Adjustable Tension / Shear Strain Rate Ratio Mixing Device

Nylon 6(PA6),one of the five commonly used engineering plastics,has the characteristics of wear resistance,corrosion resistance,easy processing and forming,and it is widely used in industry.However,nylon 6 has poor dimensional stability,low strength and modulus.The carbon fiber(CF)filling modification of nylon 6 by melt blending is one of the effective methods to achieve its high strength and stability and functional properties such as electrical and thermal conductivity simultaneously.Aiming at the characteristics that CF length and dispersion cannot be achieved at the same time in the CF/PA6 composite material mixing process,an ultrasonic assisted mixing device with adjustable tensile / shear strain rate ratio was developed.And on the basis of this device,the influence of the mixing device structure,material formulation and process parameters on the properties of the blend was studied.The research results have certain theoretical significance and engineering application value.This subject is based on the principle of volumetric transport dominated by normal stress.An ultrasonic assisted adjustable stretching / shear strain rate ratio mixing device was developed.The structure and working principle of the new mixing device were analyzed and introduced.The physical and mathematic model of the blade mixing unit was established.Theoretical analysis found that adjusting the eccentricity of the device can change the tensile and shear strain rates of the mixing unit and the ratio between them.Among them,the tensile strain rate is always dominant.The ultrasonic wave with adjustable power is applied to the direction that is vertical to melt flow,realizing the continuous and effective assistance of ultrasonic waves to the high-temperature and high-pressure melting and mixing process dominated by normal stress.CF / PA6 blends were prepared via this mixing device without adding any additives,and the effects and mechanism of volumetric tensile deformation at different eccentricities on CF length and CF dispersion in CF / PA6 blends were investigated.The effects of CF content(0-40wt%),tensile / shear strain rate ratio,eccentricity(1mm-4mm)and mixing time on the microstructure and properties of CF / PA6 blend were experimentally investigated.The results show that the addition of CF is beneficial to the improvement of the crystalline properties,mechanical properties and electrical conductivity of the blends.Under the action of individual volume tensile deformation,the low content of CF can be uniformly dispersed in the PA6 matrix;a reasonable tensile / shear strain rate ratio can simultaneously obtain a better CF dispersion state and a longer CF average length,obtaining a blend with both excellent mechanical properties and electrical conductivity;The auxiliary effect of ultrasound with adjustable parameters(time / power)on the length and distribution status of CF in the blend was experimentally studied.The research results show that in the experimental research range,ultrasonic assistance greatly avoids the excessive breakage of CF while greatly promoting the dispersion of CF and improving the interface bonding state between CF and PA6 matrix and realizes the high-efficiency and uniform dispersion of high-content CF in the PA6 matrix,which reduces the conductive percolation threshold of the blend;ultrasonic assistance with appropriate time and power will improve the crystalline properties,mechanical properties and electrical conductivity of the blend.This mixing device provides new technologies and equipment for the efficient preparation of fiber-filled or multiphase polymer systems.