Study On Cell Morphology And Properties Of Microcellular Polylactic Acid

In recent years,environmental protection has become a top priority with the country putting more emphasis on green development.At the processing technology level,the supercritical carbon dioxide foaming technology has received a lot of attention due to the characteristics of green environmental protection.In the matter of the selection of polymer materials,people pay more attention to degradable,low energy consumption and small environmental pollution polymer materials.Poly(lactic acid)is a kind of typical biodegradable polymer material,based on the extracted from green plants such as potatoes,corn,it also can be degraded completely under the condition of natural environment,and only generates carbon dioxide and water,so it won't cause pollution to the environment,and attracting the attention of more and more researchers.However it is difficult to foam the poly(lactic acid)(PLA)by supercritical carbon dioxide foaming technology,as its low melt strength and poor heat resistance and big shortcomings,such as viscosity,easy to appear bubble and bubble hole collapse phenomenon.In order to reduce the above disadvantageous factors and prepare stable bubble pore structure,high bubble hole density,high foaming ratio of PLA foam material at the same time,in this paper,we used homemade supercritical carbon dioxide autoclave foaming,reasonable regulation of foaming temperature and saturation pressure,saturation time,preparation and research of pure polylactic acid(PLA)and poly(lactic acid)/polycaprolactone foaming material performance.Different bubble pore structure of microporous material with the various performance,in order to in-depth study of pure polylactic acid foaming material performance,in the experiment,first by regulating the foaming process(saturation pressure,saturation time,foaming temperature)was prepared with different bubble pore structure morphology of foamed materials.In the same sufficiently long saturation time,the average bubble size of the pure PLA foam is changed within the range of 2-30 ?m by adjusting the saturation temperature and saturation pressure.When the pressure is constant,the hole size and opening rate increase with the increase of foaming temperature.When the temperature is certain,the pressure increases and the hole size decreases and the opening rate increases.Then quantitative analysis was used to analyze the mechanical effects of bubble size,relative density and porosity on foaming material.However the opening rates of neat polylactic acid foams materials are high,but the mechanical performances are poor,and they are difficult achieving to apply in biological tissue engineering.So this paper also studied polylactic acid/poly caprolactone blend foams next.We prepared PLA/PCL blend foams with the quality ratio of 60/40,70/30,70/30 respectively,the results showed that the quality ratio of 60/40 component of hard foam,while the opening rate is very high,but the pore size is too big and expand ratio is very low,it is difficult to industrial application;And it is difficult to form the opening structure with the mass ratio of 80/20.The foam tensile strength of the PLA/PCL(70/30)mixture was similar to that of the pure PLA foam,but the tensile breaking elongation was significantly larger,and the compression strength decreased with the saturation temperature increasing.