The Modification Research Of Polypropylene Packaging Materials

Polypropylene(PP) has been intensively applied in automobile parts and packaging materials because of its lightweight, excellent moisture resistance, good heat-resistance,non-toxic and easy processing. Owing to low transparency and poor impact strength of ordinary polypropylene, application of medicine, food, industrial production and other fields is limited. In this study, a-phase nucleating agent sorbitol derivatives(Millad NX8000K), (3-phase nucleating agent rare earth organic compounds(WBG-M) and their compound nucleating agents were introduced into polypropylene matrix to improve its the transparency and impact strength, which was in order to find the best recipe and obtain high-performance polypropylene packaging materials.Polypropylene powder, main antioxidant 1010, secondary antioxidant 168, stabilizer and a-phase nucleating agent sorbitol derivatives(Millad NX8000K) whose mass fraction was 0, 0.2, 0.25, 0.3, 0.4 and 0.5 wt% was blended, after that, extruded by a single screw extruder and pelletized to prepare samples, which were analyzed by polarized light microscope(PLM), differential scanning calorimetry (DSC), wide-angle X-ray diffraction(WAXD), light transmittance test, haze test, impact strength test and tensile strength test. It was found that when the a-phase nucleating agent increased to 0.25%, the crystallite size of the sample decreased, the crystallinity increased. The transmittance reached a maximum and the haze achieved minimum. The impact strength was higher and the tensile strength was lower than that of pure polypropylene sample due to crystallinity and spherulite size.In this paper, ?-nucleating agent (WBG-M) with mass fraction of 0,0.1, 0.15, 0.2 and 0.25 wt% was blended with polypropylene powder, antioxidant and stabilizer, co-extruded,pelletized and prepared samples to carry out the performance tests. WAXD demonstrated that ?-nucleating agent could induce P crystal to generate effectively. With the increase of the content of ?-nucleating agent, the crystallite size decreased, crystallinity of ? crystal decreased, crystallinity of ? crystal and total crystallinity increased, ? crystal relative content increased. When the addition of (3-nucleating agent arrived at 0.2%, the transmittance of the sample was the smallest and the haze was the largest. When the addition of ?-nucleating agent was 0.25%, impact strength and tensile strength were maximum for the crystallinity.When the content of a-phase nucleating agent (Millad NX8000K) increased to 0.25%,the transmittance reached maximum. It was taken into account that a-nucleating agent was mixed with ?-nucleating agent of different mass fraction. That is, when the content of a-nucleating agent (Millad NX8000K) was 0.25% and the mass fraction of WBG-M was 0.1, 0.15, 0.2 and 0.25 wt% respectively. It was blended with polypropylene to prepare samples which was used to carry out performance test. The results represented that when the content of a-nucleating agent was 0.25% and the content of (3-nucleating agent was 0.2%, the sample contained a crystal and ? crystal at the same time, whose crystal size decreased, the crystallinity of ? crystal increased, the crystallinity of a crystal and total crystallinity decreased, transmittance, impact strength and tensile strength were the maximum and the haze was the minimum,in a word,the optical property and the mechanical property monitored the best.