Polypropylene is a strong competitor to polyethylene terephthalate (PET) blow molding bottles: compared to PET, polypropylene is less expensive, lighter, better heat resistant and lower Moisture permeability; some transparent polypropylene has higher transparency and gloss than PET. Latest Model Fashion Necklace,Platinum Jewelry,Latest Model Necklace Kovtia Jewelry Co.,ltd , http://www.jinh-jewelry.com
Compared with polyethylene terephthalate, polypropylene is 10-30% cheaper and its density is less than PET (0.9 g/cc vs. 1.35 g/cc), so the quality of polypropylene bottles is better than that of poly(p-phenylene). The quality of ethylene glycol dicarboxylate is light. Polypropylene bottles can be hot filled at 100 ° C if juice and jam products are used at such temperatures. In contrast, conventional PET bottles cannot be filled at 76 ° C above the glass transition temperature (however, some enhancement treatments have recently allowed PET to be filled at higher temperatures).
The barrier property of polypropylene to moisture is about 5 times that of PET, but the penetration rate of PP to oxygen and carbon dioxide is about 30 times that of PET. Therefore, PP bottle needs a barrier layer to prevent gas from entering or overflowing. This barrier layer is not required for PET bottles.
In pure state, PP is not as transparent as PET, so PP needs to add transparent additives to make its transparency similar to PET. Compared with PET, PP has low thermal conductivity, so it takes a long time to heat during processing or Cooling PP, so PP bottle production cycle time is 25% longer than PET bottle; nucleating agent can accelerate crystallization during cooling and shorten cycle time, so shortening cycle time can improve transparency.
PP processing temperature range is only 3-5 ° C, while PET processing temperature range is 10-15 ° C; in the production of blow molding bottles, PP preform production line equipment compared to PET preform production line Not so expensive. The main applications include food, beverages and other product containers. The initial disadvantages of many polypropylenes are similar to those of PET - poor transparency, long cycle times, large gas penetration and low impact strength, have been used with clearing agents or nucleating agents, barrier layers and metallocene-based Nucleating agents overcome these shortcomings. Along this line, the performance of polypropylene is further enhanced and the polypropylene market is opened up.