Polypropylene is a strong competitor for polyethylene terephthalate (PET) blown bottle applications: Compared to PET, polypropylene is less expensive, lighter, better heat-resistant filled and lower Moisture permeability; Some transparent polypropylene has a higher transparency and gloss than PET. Women Steel Ring,Antique Steel Ring,Women Antique Steel Ring COYA Jewelry Co., Ltd , http://www.szsteeljewelry.com
Compared to 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. Diethylene glycol dicarboxylate is light in weight. Polypropylene bottles can be hot-filled at 100°C if juice and jam products are used at such temperatures. In contrast, ordinary PET bottles cannot be filled at a temperature above the glass transition temperature of 76[deg.] C. (However, some recent reinforcing treatments have allowed PET to be filled at higher temperatures).
Polypropylene's moisture barrier is about 5 times that of PET, but PP's permeability to oxygen and carbon dioxide is about 30 times that of PET. Therefore, PP bottles require a barrier layer that prevents gas from entering or overflowing. The PET bottle does not require this barrier layer.
In the pure state, PP is not as transparent as PET, so PP needs to add a transparent additive, making it similar to PET in transparency; 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 bottles; nucleating agent can accelerate the crystallization in the cooling process, shorten the cycle time, so shorten the cycle time can improve the transparency.
PP processing temperature range is only 3-5 °C smaller, and 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 drawbacks of many polypropylenes are similar to those of PET - poor transparency, long cycle times, high gas penetration, and low impact strength, which have used clearing agents or nucleating agents, the use of 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.