Advances in Physical Foaming of Biodegradable Polymers
Compared to traditional polymer foam materials,biodegradable polymers have the advantages of being green,environmentally friendly,and sustainable,and are widely used in agriculture,food packaging,and biomedical fields.Biodegradable polymer materials prepared by physical foaming process not only have the above characteristics,but also have the advantages of lightweight,thermal insulation,cushioning and so on.They are potential substitutes for traditional petroleum based polymer foam materials.However,biodegradable polymers generally have limitations such as single molecular chain structure,low melt strength,high preparation cost,and are prone to cell rupture or fusion during physical foaming,resulting in matrix shrinkage and inability to maintain cell structure.This work takes the process mechanism of biodegradable polymer physical foaming as the starting point,classifies different physical foaming methods,and comprehensively elaborates on the characteristics of each category of processes.Subsequently,discussions were conducted on the foaming behavior and parameter relationships of several typical biodegradable polymer materials.The selection criteria for foaming processes and foaming agents for different materials were introduced,and the influence of foaming conditions on expansion rate and cell size was summarized.In addition,corresponding solutions were given to the problems existing in the foaming process of various biodegradable polymers,and the functional applications of biodegradable polymer foam in food packaging,electronic appliances,and biomedical materials were introduced.Finally,the effects of foaming process,polymer crystallization behavior and modification methods on the foaming process of biodegradable polymer were summarized,and the direction and challenges of biodegradable polymer foam in the future development were proposed.
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