The Research On Foaming Agent BIH40and Processing Technology Affect Polymer Chemical Foaming Property

Foaming materials have some advantages, like light weight, heat insulation,sound-proofing, high specific strength, buffering, low cost, etc.. In recent years,Plastics foaming materials are developing very fast and will to be an important branchin modern plastics industry. It has been widely used in industry, agriculture, car,building field, etc.. The traditional foaming plastic—foaming Polystyrene—candestroy atmospheric ozone layer for using Chlorofluorocarbon during formingprocess. The waste can not rot and is difficult to be recycled, which can finally causeserious “white pollution” problem. Now some researchers move their researchattentions to PP and PE polyolefin foaming materials, friendly environmental andbiodegradable foaming materials, like PLA. For their naturally limitation, such as lowmelt strength, it is relatively difficult to be foamed for these above mentionedmaterials. By now, China is still on the threshold stage in their industrial production.This thesis represents the sample crystallization, foaming behaviors and mechanicalproperties of chemical foamed PP, PE and PLA samples. The processing parametersare foaming agent content and different processing conditions, as well as usingdifferent forming methods.BIH40was used as foaming agent and injection molding process was applied tofabricate PP and PE foaming materials. The influence of foaming agent content on thefoaming density, tensile strength and notch impact strength of PP and PE foamingproduct were discussed. Scanning electron microscope (SEM) was used to test thebubble features. Injection molded foaming PP and PE specimens were produced withdifferent expansion ratio, average cell size and cell density through changing thefoaming agent content. Mechanical testing results revealed that the foaming agentcontent could affect the mechanical properties. For example, with the increase ofBIH40, tensile strength, notched impact strength, elongation at break and density ofthe foamed samples decreased compared to that of non-foamed counterpart.Elongation at break of PE of foaming agent at1.0wt.%level increased than otherfoaming samples. The notched impact strength of PP at0.5wt.%foaming agentloading clearly improved than other foaming samples. The comprehensive experimental testing results shown that the foaming product performance was betterwhen the foaming agent content was1.0wt.%.Extrusion molding technology was also used to make PP, PE and PLA extrusionfoaming materials through changing screw speed and BIH40foaming agent content.With the increasing of foaming agent content, cell density gradually increased andcell size constantly enhanced. If the foaming agent continuously increased, somebubbles connected together or collapsed which resulted in worse cell morphology.When the foaming agent content was fixed at1.0wt.%, while screw speed waschanged from16r/min to26r/min, the SEM image and data analysis revealed that thebubble size became smaller, but the cell density increased. Continuously added thescrew speed to42r/min, the foaming phenomena was not good, small bubbles couldbe identified and even partially non-foamed area could be observed in the fracturedcross section. When the foaming agent content was1.0wt.%and the screw speed was26r/min, the foaming morphologies of foamed materials were better. The foamingagent content did not evidently affect the degree of crystallinity of foamed materials,but different screw speed had a certain influence on it. In the PP case, the β crystalhas changed, that is, the degree of crystallinity improved and became higher with5.7%under42r/min compared to that at16r/min.From the above experimental results, when the BIH40foaming agent contentwas1.0wt.%, injection foaming molded PP and PE products with a certainmechanical property and foaming ratio were obtained. At an appropriate screw speed,extruded foaming PP, PE and PLA samples with rather uniform cell morphology onthe fractured surface could be formed. These experimental results and related data canprovide essential practice foundation for foaming PP, PE and PLA in industrialapplications.