There are many materials for plastic bottles, and the functions and characteristics of plastic bottles made of different materials are also different. Let's compare PET plastic bottles and PP plastic bottles.
Characteristics: PE is relatively soft and feels waxy. Compared with the same plastic, it is relatively light in weight and has a certain degree of transparency. The flame is blue when burning.
Toxicity: non-toxic and harmless to the human body.
Commercially available high-density polyethylene (HDPE), density 0.945~0.96 g/cm3, melting point 125~137 degrees Celsius;
Linear low-density PE (LLDPE), density 0.925 g/cm3, melting point 120~125 degrees Celsius;
High-pressure low-density PE (HP-LDPE), density 0.918 g/cm3, melting point 105~115 degrees Celsius.
Applications of polypropylene (PP): microwave tableware, basins, plastic buckets, thermos shells, woven bags, etc.
Characteristics: high chemical stability, good hygiene performance, high heat resistance. Microwave tableware can choose plastic products marked with PP.
Toxicity: non-toxic, harmless to the human body.
The polymer can have three stereo structures: isotactic, syndiotactic, and atactic polypropylene. The former two can crystallize, but the latter cannot. The commercially available polypropylene products are basically isotactic structures, with a melting point of 164~170 degrees Celsius, a density of 0.935 g/cm3 for the crystalline part, and 0.851 g/cm3 for the non-clean part.
The biggest disadvantage of PP is that it is easy to oxidize and age. Now it is overcome by adding antioxidants and ultraviolet light absorbers.
Application of polyester (PET): plastic beverage bottles, medicine bottles, cosmetic bottles, oil bottles, and various bottle caps and insulation covers.
Features: good transparency, not easy to break, good chemical stability, suitable for a variety of liquid or solid medicine packaging. It has good shielding against ultraviolet rays.
Toxicity: non-toxic.
PET plastic bottles are the mainstream of beverage packaging. PET plastic bottles should be the dominant force in China's beverage packaging industry. So far, no better or better packaging materials have been found to replace PET plastic bottles. PP bottles are mainly molded in one-step injection stretch blow molding and two-step heating stretch blow molding machines. They have the advantages of transparency, robustness, and heat resistance, and the price is also lower than that of radical materials. They can be stored at 100°C.
Generally, 0.1%-0.4% sorbitol xylene nucleating agent is added to PP plastic bottles, and high-transparency PP plastic bottles can be produced through blowing, blowing, injection, extrusion and other methods. PP plastic bottles have good heat resistance, flexible bottle shape design, and excellent performance in safety, hygiene and taste retention of contents. The price is cheaper than PET, PS, PE and other materials. The application scale of PP plastic bottles in the beverage packaging market has gradually approached PET bottles. The continuous development of modified resins, permeability enhancers and mechanical equipment technology has enabled PP containers to replace glass, PET and PVC containers, and has broad market prospects.
