Random Copolymer Polypropylene (pp-r) Processing And Applied Research

Propylene-Ethylene Random Copolymer (PP-R) is very difficult to processing due to its narrow molecular weight distribution, large molecular weight and poor crystallizing properties. In this paper, we carried out systematic research on PP-R's structure and processing properties, and made the foaming research field for PP-R.Through testing the crystallizing properties of PP-R and PP-R/ESI24 blends,it is found that PP-R have a low crystallity and large crystallizing rate, which is resulting PP-R cool slowly and difficult to solidify in pipe production. The crystallity of PP-R/ESI24 blend displayed a non-linear function with the increase of ESI24 content. Little amount of ESI24 could be able to increase PP-R's crystallizing temperatures and nucleating rate significantly.Rheological properties of PP-R were studied with on-line rheometer. Experimental results indicated that PP-R melt had low shear-sensitivity and temperature-sensitivity. It was showed that the modification was an effective means to improve its flowing property in processing.Ethylene-Styrene Interpolymers (ESIs) containing up to about 80wt.% styrene, ESI24 gived an excellent compatibility and good toughening effect to PP-R,and ESI24 could improve the PP-R melt strength and its foaming properties.The mechanic properties of PP-R/ESI24 blend were studied, and a mechanic properties contrast was made with PP-R/POE blends. The results indicated that both ESI24 and POE showed good compatibility to PP-R and could effectively improve the mechanic properties of matrix resin. Moreover, when the contents of two toughening modifiers were controlled in the range of 10% ~20%,the blends displayed opitmal overall mechanic properties, that is, the impact properties of the blends were improved significantly with little loss in tensile properties. ESI24, however, showed better modification effect than POE in improving PP-R's mechanic properties. On one hand, PP-R/ESI24 blends displayed superior impact properties over PP-R/ POE blends. 5% ESI24 could behavior the brittle-tough transition, and 20% ESI24 was essential to make PP-R super-toughened, with an Izod impact strength reaching as high as 828J/m, on the other hand, with the increase of modifiers' contents, PP-R/ESI24 blends showed less loss in tensile properties than PP-R/ POE blends.In this paper, we discussed the effects of ESI24, nucleation agents and processing parameters on the qualities of the final foamed products. Because PP-R resin's crystallity and melt strength is not big enough to stabilize cells in foaming processing, blend with 10% ESI24 could not only increase PP-R's melt strength, but also improve PP-R's flowing properties in processing. Under the content as above, suitable content of nucleation agents, lower die temperature, proper temperature in metering zone, higher screw speed and higher die pressure were quality guarantee for a good foaming products.