Preparation Of High-Expansion PLA Composite Open-Cell Material And Study On Its Oil Absorption Properties

With the rapid development of modern industry,the problems of industrial waste oil,marine oil spills and domestic oil pollution are becoming more and more serious.Natural inorganic and organic oil-absorbing materials have disadvantages such as low oil absorption rate and poor oil-water selectivity.Oil-absorbing materials such as polypropylene(PP),polyurethane(TPU)and other fiber fabrics that are common in the market have poor reusability,and are difficult to recycle after the oil is saturated,which is likely to cause secondary pollution.How to prepare biodegradable new oil-absorbing materials with high-efficiency circulating oil-absorbing function is a hot research topic at home and abroad.Therefore,this thesis uses polylactic acid(PLA)as a matrix to construct a porous material system for oil-water separation engineering applications,and uses supercritical carbon dioxide(scCO2)foaming technology to prepare PLAbased porous materials with high foaming ratio and high open porosity.The regulation of the cell structure realizes high efficiency and circulating oil absorption function.The relevant research results of this thesis will help expand the application field of scCO2 technology in material processing,and provide a theoretical basis and data support for the green processing technology of new and efficient biodegradable oil-absorbing materials.The main research contents of the thesis are as follows:(1)Preparation of high-expansion PLA porous materials and control of cell structure.Compare the microcellular foaming behavior of pure PLA under different intermittent foaming processes,and optimize the foaming process interval and cell structure.The study found that the sample obtained by high temperature saturation and cooling foaming has a foaming ratio of up to 50.The pressure relief rate has a huge impact on the cell structure of the sample.The pressure relief rate in the foaming reactor mold is increased from 3.83MPa/s to 6.63MPa/s,the expansion ratio is increased by 31%,and the open cell ratio is increased by 18%.As the foaming pressure is reduced from 17.24 MPa to 13.79 MPa,the foaming ratio increases from 27.64 times to 44.58 times.Due to the extremely low open porosity(<10%)and small toughness of the PLA porous material,the oil absorption rate is only 10g/g.(2)Preparation of PLA/PBAT porous material with high open-cell content and study on its oil absorption performance.Simply increasing the foaming ratio of porous materials cannot achieve the purpose of efficient oil absorption,and it is necessary to further increase the internal open porosity of the material.In this part of the study,adding polyoxalic acid/butylene terephthalate(PBAT)as a heterogeneous nucleating agent to the PLA matrix to improve the viscoelasticity of the polymer.The addition of PBAT can effectively improve the shrinkage of the sample under the condition of low foaming pressure.Through the adjustment of PBAT content and foaming process parameters,the highest foaming ratio and open cell ratio of the foamed samples of PLA/PBAT blends can reach 51 times and 77%,respectively.The results of cyclic compression test found that the permanent deformation of the PLA/PBAT blend porous material during cyclic compression is smaller than that of the pure PLA foamed sample.This result is conducive to the realization of the oil absorption function of the foamed sample multiple cycles.The oil absorption test results show that the single maximum oil absorption rate of the PLA/PBAT foamed sample is about 20g/g.(3)Preparation of PLA/PB AT/Talc porous composite material and study on its oil absorption performance.In order to further enhance the melt strength of the PLA matrix and improve the microcellular foaming behavior,this part adds different contents of talc powder(Talc)on the basis of the PLA/PBAT blend to construct a porous composite system.The study found that the addition of 1%to 5%by mass of Talc significantly reduced the domain size of the PBAT dispersed phase in the PLA matrix,and there was no significant agglomeration of Talc particles.The addition of Talc significantly improves the viscoelasticity of the PLA/PBAT blend and increases the crystallinity of the PLA matrix.Microcellular foaming experiments have found that the foaming ratio of composite materials can reach 55 times.As the foaming temperature increases,the open cell ratio of the 3.0 wt.%Talc composite foamed sample increases significantly,up to 81%.The results of cyclic compression experiments show that the compressive strength decreases as the expansion ratio increases,and a high open cell ratio will reduce the compressive strength.Compared with the PLA/PBAT blend foam sample,the permanent deformation of the composite material is reduced by 12%,and the oil absorption rate is increased by 11%.