Study On The Dry-jet Wet Spinning Process For PMIA Fiber

Poly(m-phenyleneisophthalamide)(PMIA)is an important high performance fiber with excellent heat resistant and good spinnability.PMIA fiber and paper have been widely applied in the fields of industry,military and civilian,especially in the field of high temperature protecting apparel.Dry-jet wet spinning is an important spinning process,which was much easier than wet spinning process to improve the fibers' performance,and it used much less energy compared with dry spinning process.Dry-jet wet spinning would be a rewarding trying in the field of preparing high performance PMIA fibers.Firstly,in this paper the rheological properties of PMIA solutions under different conditions were investigated by ARES-RF-S equipment.The separate and combined effects of solid contents,molecular weight,and temperature and shear rate were analyzed to understand their contribution to the solution's viscosity.We obtained important parameters such as non-Newton index and structural viscosity index.We found that spinning solution was pseudo-plastic fluid,whose viscosity would be increased by increasing temperature and shear rate or decreasing the spinning pressure,concentration or molecular weight.Through Orthogonal analysis,we confirmed molecular weight and solid contents have the greatest effect to the viscosity of spinning solutions.Multiple linear regression equation helped us to find the relationship with viscosity and four factors was Ln?=-33.2550+3.3925LnM+0.0846Ln?+1.6516LnC-1074.6/T.Further,die-swell effect of PMIA solutions was investigated by gravimetric method.We found the influence of length/diameter ratio(L/D),temperature and pressures and shear rate on the die-swell ratio and die-swell activation energy and got the die-swell activation energy under different shear rates and L/D.The experimental data showed that die-swell ratios ranged from 1.1 to 2.8.Increasing the L/D and temperature or decreasing the pressure and shear rate could decrease the die-swell ratios.Research on die-swell made great contribution to designing spinneret,stability of spinning and maintaining quality of fibers.Last but not least,we made a lot of research on dry-jet wet spinning process including coagulation bath,boiling water bath and heat treatment.In this paper,we used breaking strength to characterize the influences on fibers' quality caused by different spinning conditions.It's found that 1cm air gap,30%coagulation bath concentration and 30? bath temperature would improve fiber forming structure.At the stages of coagulation,boiling washing and heat treatment,increasing the extension ratios would improve the fibers' mechanical performance as well.Under the optimal process,the fibers with tenacity of 5.536 cN/dtex,breaking elongation of 45.17%were prepared,and fibers' qualities were better than familiar wet spinning process prepared.