Study On The Preparation And Flame Retardant Modification Of PP/POE Microfoamed Composites

Polymer micro-foaming material is a new kind of material which is prepared by physical or chemical foaming method.The inner cell distributes evenly,and the size is about 10-100 micron,and the cell density is more than 10⁷/cm³.Micro-foamed materials have the advantages of light weight,low heat transfer and conductivity,good sound insulation,etc.At the same time,they are superior to non-foamed plastics in some mechanical properties,so their applications in automotive parts and other industrial fields are growing rapidly.In addition to the above advantages,polypropylene?PP?micro-foaming materials have more excellent comprehensive properties,low price and broad application prospects.Polyolefin elastomer?POE?is a thermoplastic elastomer catalyzed by metallocene catalyst for in-situ polymerization of ethylene and butene or octene.It has good toughening effect when added to PP.At the same time,POE has good compatibility with PP and can be well dispersed in PP matrix.POE not only imparts excellent impact resistance,but also POE uniformly dispersed in the PP matrix can also act as a nucleating agent to improve the foaming process of PP.The purpose of this paper is to prepare PP/POE micro-foamed composites,then modify them by flame retardant and characterize their comprehensive properties.The details are as follows:?1?Different ratios of PP and POE were blended to prepare a corresponding foamed substrate,and then the substrate was foamed and injection molded at a suitable temperature by using an azodicarbonamide?AC?foaming agent.We found that the impact strength of the material increased significantly with the addition of POE elastomer,while other mechanical properties decreased gradually with the increase of POE content.Through the study of the cross-sectional morphology,dynamic rheology and crystallization process,it was found that when the content was 10 phr,the cell distribution was uniform and the size was appropriate.Meanwhile,DSC curves showed that adding POE increased the crystallization peak temperature to 117.01°C,increased the crystallization rate and decreased the crystallization simultaneity to 33.1%.These two effects provide good internal conditions for PP foaming.At the same time,the mechanical properties test showed that when POE content was 10 phr,the notch impact strength increased by 158.8%,and other mechanical properties decreased at a low level.Considering comprehensively,when POE content was 10 phr,the foaming properties and mechanical properties of micro-foamed materials were the best.?2?Flame retardant and compatibility modification of PP/POE micro-foamed composites were carried out by using self-made intumescent flame retardant IFR with polypropylene grafted with maleic glycoside?PP-g-MAH?and polyolefin elastomer grafted with maleic anhydride?POE-g-MAH?,respectively.The effect of different compatibilizer content on IFR flame retardant PP/POE micro-foamed composites was studied.Then Nano-CaCO₃ was added to the most suitable component of compatibilizer content to prepare synergistic flame retardant foaming pattern.It was found that the flame retardant and thermal stability of the material can be improved by adding IFR alone.After adding compatibilizer,the distribution of IFR was improved,the vertical combustion grade reaches V-1,LOI rised from 17.2%to 27.3%,and dropping phenomenon disappears.After adding Nano-CaCO₃,the synergistic effect of Nano-CaCO₃ and IFR further increased the vertical combustion grade to V-0 and LOI to 31.2%.At the same time,the addition of Nano-CaCO₃ also significantly improved the mechanical properties and foaming properties of the materials;finally,the foaming mechanism of the above-mentioned micro-foamed composites with excellent flame retardant properties was comprehensively compared,and the flame-retardant PP/POE micro-foamed composites with excellent flame retardancy and foaming properties were obtained.