| With the improvement of the environmental protection consciousness of people, thedevelopment of green economy and sustainable development have become necessary inmodern times. In polymer materials field, researchers focus on the polymer materials with thefeatures: less environmental pollution, lower energy consumption, biodegradable, sources thatcan be found in nature world widely. Poly lactic acid(PLA) has both these advantages: greenplant source and biodegradable, so it became one of the hot research spots. Because of thePLA’s heat resistance is poor, and its melt strength is not strong enough. In the process offoaming, the bubble hole prone intend to collapse and merged, all of these factors are goingagainst PLA’s foaming.In order to make a comprehensive and thorough research on the performance of PLAfoam material, which is prepared with good pore structure of the PLA bubble form foammaterial, by adding bubble density, reducing the size of bubble holes and homogenizationbubble size distribution of the holes. This paper according to the characteristics of the highpressure reaction kettle, designing a small porous foaming mold. In the original high pressurereaction kettle we can carry out foaming based on the same conditions (pressure, temperature,saturated time, foaming temperature)under the different formulations polymer materialsresearch.In the experiment, researches use the homemade foam die combination with highpressure the reaction kettle, studying the influence of foam process conditions to pure PLAfoaming structure. The results show that the saturated pressure, saturated temperature,saturated time, foaming temperature, had important effect on the PLA micro porous foammolding. The effect of saturation pressure to the bubble size of the holes after foaming isobvious. As the saturated pressure’s increasing, the bubble size of holes are becoming narrowin distribution and bubble hole diameter average drops. Under the pressure of20MPa, thediameter of bubble hole is an average of8.21μm, bubble hole density is2.49x10~9cell/cm~3. Theaverage bubble hole diameter of the PLA foaming material with saturated temperature’sincreasing rise after the first decline, bubble hole density along with the increase oftemperature saturated first increases then decrease. When under160℃, the bubble diameterhole average is minimum, reaching for10.76μm. When the temperature is too high, PLAmolecular chain rupture, degradation occurred. The viscoelastic properties of foam system change obviously with foam temperature, in low temperature, there are a lot of withoutfoaming area. Along with the foam temperature rises gradually, bubble holes become even,and the bubble hole average diameter becoming lower. The solubility of carbon dioxide inPLA matrix is related with saturated time. Saturated time for1h, average bubble diameterhole is10.76μm, and bubble hole density of1.31x10~9/cm~3.This paper through the control of the size of foam space, studying the influence of thefoaming space, foaming dimension, free foaming and limited foaming to PLA microcellular.The density of the hole decreases with bubble foam space’s increasing. When undergoing freefoaming, the shape of PLA foaming bubble hole is a circle and in limited foaming, the bubblehole is hexagonal. Compared with the free foam, during limited foaming the distribution ofbubble diameter of foam hole is more uniform. At one dimensional foaming, the orientation ofPLA bubble pore structure became more serious with the increase of the foam space. Whencarrying out3D foaming, the structure of the PLA bubble hole is more circular vertically andhorizontally,this shows that in the direction of the multidimensional bubble holes were givenmore consistent growth. |
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