Study On Rheological Property And Dissolution Rate Of Supercritical CO₂ In Polymer Solubility

Thanks to the excellent solubility,diffusion and cost advantages of supercritical carbon dioxide,it has become an ideal foaming agent in the forming process of microcellular plastics.While the lack of basic research on the solubility of ScCO₂ in polymer matrix,which set the process parameters in the forming process,the lack of appropriate guidance,to some extent limit the development of microcellular plastics.This paper mainly focuses on rheological properties and dissolution rate of ScCO₂ in polymer melt,and building a high temperature and high pressure magnetic stirring reactor for experimental ScCO₂ dissolution platform,by way of experiments to further clarify the effects of the process parameters on polymer /ScCO₂ solution rheology and dissolution rate so as to get better rheological properties and faster dissolution of ScCO₂ in polymer matrix.The main research results are as follows:1,through the integration of existing schemes,a set of experimental device was designed to dissolve ScCO₂ in the polymer melt,by which constant temperature and pressure can be achieved,to measure the dissolution rate of polymer/ ScCO₂ homogeneous rheological properties and ScCO₂ in the matrix.By using finite element volume method simulation software of Fluent,the size of the conical mixing element of the core measuring component was optimized,and the measurement accuracy of the rheological properties of the polymer/ScCO₂ homogeneous system was improved.2,by using finite element volume method software Fluent,the polystyrene?PS?/ ScCO₂ homogeneous rheological properties affected by different temperature,ScCO₂ content and shear rate were simulated,to further clarify the effects of shear rate,ScCO₂ content,melt temperature and viscosity of the homogeneous body,and found that when the temperature is lower,homogeneous body viscosity decreased with increasing concentration of ScCO₂ is more intense,so in a certain range,the lower the temperature in the machining process,lower CO₂ content and lower shear rate,the viscosity was conducive to more homogeneous melt,which helps in the capillary die stage have a greater pressure drop rate and get a better effect of products.While the increasing of the concentration of CO₂,the nucleation of bubbles can be effectively promoted,there is an optimum range for CO₂ content and a balance point between viscosity and bubble nucleation rate.3,the rheological properties and dissolution rate of ScCO₂ in polymer melt were investigated by means of a platform designed for dissolution.With the change of temperature and shear rate,by measuring the rheological properties of the homogeneous,comparative analysis of simulation and experimental results,found that the increase of melt temperature or shear rate helps to reduce the viscosity of homogeneous body;especially when the temperature is low,the viscosity decreased with increasing concentration of ScCO₂ is more intense,also reflects the experimental study a similar trend;ScCO₂ dissolution experiments performed under different pressure or shear rate conditions in the polymer,found in low pressure or weak shear conditions,slower in the polymer dissolution rate of ScCO₂,with the increase of pressure or shear,per unit time of dissolved ScCO₂ was significantly increased,the foaming material the cell density is bigger,the distribution is more uniform.While promoting the dissolution of ScCO₂ in polymers,the pressure and temperature will affect each other in the actual experimental operation,and it is difficult to affect the other side in the process of regulating the pressure or temperature.Therefore,the experiments proved that the pressure or shear effect can effectively promote the dissolution of ScCO₂ in the polymer,but the application of shear is a relatively simple and stable process.