Studies On Preparation Of Poly(Styrene-co-N-phenylmaleimide) And Its Reactive Extrusion Process

In this study,the independent development of the process for the manufacture of poly(styrene-co-N-phenyl-maleimide)(SNPMI),a kind of heat-resistant resin,and the optimal design of the complex reactive extrusion process was focused on.Based on the experimental studies on the mechanism,the kinetics,the reactive extrusion process the thermal imidization of poly(styrene-co-maleic anhydride)(SMA)with aniline and the relationship of the thermal properties and the result polymer composition,a model for the micro kinetics and a model for the macro reactive extrusion process were developed.Based on the-references on the thermal imidization of poly(amide acid)and the polymer composition analysis,the thermal imidization mechanism of SMA with aniline was demonstrated to be a two-stage consecutive reaction(as shown in the scheme below),in which a second-order reversible ring-opening reaction of SMA to produce poly(styrene-co-N-phenyl-maleamic acid)(SNPMA)and a first-order irreversible intrachain ring-closing reaction to form SNPMI were involved. Furthermore,the latter reaction is the controlling step.The effect of the reaction condition,such as the temperature,the solution concentration and the aniline to maleic anhydride ratio(ANL/MAh ratio)etc.,on the imidization rate in the solution reaction system was investigated.It was found that the imdization of SMA was much slower than the imidization of small maleic anhydride molecule.The kinetic parameters within broad reaction temperature range and wide SMA concentration range were determined as k₁^solution=1.10×10⁴e^{-27.100 RT}(1·mol^-1·s^-1), k_-1^solution=7.82×10⁴e^-61,000/RT(s^-1)and k₂^solution=9.49×10⁴e^-65,800/RT(s^-1).The competitive reactions of SNPMA to produce either SMA or SNPMI were investigated by using the TGA-FTIR integrated technology,and the kinetics parameters of the above two reactions in the melt state were determined as k_-1^melt=1.02×10⁵ e^-60,200/RT(s^-1)and k₂^melt=1.12×10⁵ e^-70,200/RT(s^-1).The reactive extrusion process for the direct imidization of the molten SMA was studied,and the influence of operation conditions on it was investigated.It was shown that reducing the temperature,increasing the ANL/MAh ratio or decreasing the SMA throughput helped raising the imidization reaction conversion.However,a higher screw speed led to a shorter fluid residence time in the extruder accompanied with the strenghened mass transfer,especially for the extrusion process with a higher extrusion temperature due to the lower viscosity.The mechanism of the reactive extrusion process for the direct imidization of the molten SMA.was deduced from the experimental phenomena and the product composition.In an extruder,the barrel temperature(>210℃)is much higher than the boiling point(184℃)of the aniline.Accordingly,most of the aniline is vaporized immediately after being fed into the extruder.The aniline in gas phase occupies the unfilled part of the extruder and only little can stay in the liquid phase.Then along with the consumption of the liquid aniline,the aniline in the gas phase will gradually liquidize and react immediately.On the basis of this heterogeneous reactive extrusion process mechanism,a continuous process model was developed.Meanwhile,the efficiency of aniline,a useful concept,was proposed to evaluate the reactive extrusion process.It was found that the vapor pressure increased and the initial aniline in liquid phase decreased when the temperature was raised,and then resulted in a drop of the efficiency of aniline for the gas-liquid mass transfer restriction.It was shown that a higher aniline throughput also led to a lower efficiency of aniline.As a comparison with the above direct reactive extrusion.The thick solution reactive extrusion process for the imidization of the partially amidized SMA was investigated and a continuous process model was developed also.According to the experimental fact and the prediction results of the process model,this thick solution reactive extrusion was considered as a reactive extrusion process in melt state,and both the unreacted aniline in the inlet feed and the aniline producted from the SNPMA-to-SMA reaction will escape. The glass transition temperatures(T_g)of the imidization products of SMA with various compositions were measured by DSC.It is found that the T_g data increase as: SMAg of all the samples follows the Fox equation.It demonstrates that both the introduction of rigid phenyl rings and the presence of hydrogen-bonding interactions have great contribution on enhancement of the thermal properties.Finally,the thermal stabilities of SMA,SNPMA and SNPMI were also investigated.It was shown that a two-stage weight loss exsited during the thermogravity analysis of SNPMA,and the main weight loss of SNPMA was similar with the weight loss of SMA,which is caused by the from-SNPMA-to-SMA ring-closing reaction.Furthermore,the thermal stability of SNPMI is better than that of SMA.For example,in this study,the maximum decomposition temperature of SNPMI is 20℃higher than that of the corresponding SMA。...