Study On Structure And Properties Of Micro-foaming POM

Polyoxymethylene (POM) is a highly crystalline plastic, it's molding products have shortcomings of low impact toughness, poor dimensional stability, large notch sensitivity and large shrinkage. Through micro-foaming treatment, we can effectively improve the shortcomings of POM products, also reduce the density and quality, save materials and reduce costs. It will have great significance in lightweight production and utilization of POM products.In this study, low density polyethylene (LDPE) as the carrier and azodicarbonamide (AC) as the foaming agent were used to produce LDPE-AC foaming masterbatch by low temperature extrusion process, and micro-foaming POM materials were prepared by cavity controllable injection foaming molding. The results showed that POM foam had higher cell density and lower cell size by incorporating 0.6wt% AC content. The best foaming effects referring to better cell structure of POM foam achieved when the injection molding temperature was 180?. The existence of micro-pores makes tensile and flexural properties of POM foam have a slight decline; The lower compatibility of the selected LDPE carrier of foaming masterbatch and POM was resulted from the large solubility parameter difference, which further affected the impact properties of POM foam.In this paper, we proposed the use of ethylene-octene copolymer thermoplastic elastomer (POE) as the carrier to prepare POE-AC foaming masterbatch by low temperature extrusion process, and used cavity controllable injection foaming molding to produce micro-foaming POM based on the study of LDPE-AC foaming system. POE played a role of toughening in foaming system. Adding small amount of POE-g-MAH into foaming masterbatch as the compatibilizer in order to increase the compatibility between POM and POE during the injection foaming molding process. The results showed that the number of micro-pores increased with the increasing AC content gradually and all of the pores were closed cell. POM foam reached higher cell density, lower cell size and more evenly cell core by incorporating 1wt% AC content. The density of POM foam decreased 28% when the injection molding temperature was 170?. POE carrier and POE-g-MAH in foaming masterbatch played the role of toughening modification and increasing compatibility, which had large impact on improving the impact performance of the POM foam.In this paper, we also selected a commercial thermo-expandable microsphere Clocell 220DU30 as blowing agent. The expanding behavior of Clocell 220DU30 in POM compounds and the cellular properties of POM foam were investigated. The composition and foaming properties of Clocell 220DU30 were characterized by FTIR and SEM. When adding 2% of 220DU30, the foaming system reached the best state, owing bigger cell density and the best mechanical properties. The best foaming effect with the highest expansion ratio and impact strength achieved when the injection temperature was 190?.