What are the differences between PE, PP, PO, OPP, and CPE plastic bags?

With the rapid development of the plastic packaging bag industry and innovations in production technology and equipment, the types of raw materials for plastic packaging bags are also constantly increasing, such as PE, PP, PO, and OPP. So what are the differences between plastic packaging bags made of different materials? Which industries are they suitable for? What are the advantages of each material? Today, Shunxingyuan Packaging, a professional flexible packaging manufacturer, will give you a detailed analysis of the differences between PE, PP, PO, and OPP plastic bags.

1. PE Plastic Bags

PE plastic bags are high-molecular organic compounds formed by the polymerization of ethylene. The chemical name of PE is linear polyethylene, which is divided into two types: high-density linear polyethylene, generally called PO (HDPE), and low-density linear polyethylene, generally called PE (LDPE). In fact, low-density linear polyethylene can also be divided into two types: LDPE and LLDPE.

Packaging bag manufacturers usually call LDPE and LLDPE the main and auxiliary materials, but when manufacturing packaging bags, the two materials must be used together. If only the main material is added, the plastic bag will be very sticky; if only the auxiliary material is added, the plastic bag will lack tensile strength.

Polyethylene is recognized worldwide as the best material for food contact. It is non-toxic, tasteless, and odorless, meeting food packaging hygiene standards. Polyethylene film is lightweight and transparent, with properties such as moisture resistance, oxygen resistance, acid resistance, alkali resistance, general airtightness, and excellent heat sealing. It is one of the most widely used plastic packaging bags. Bubble bags and bone bags are made of PE material, which is a combination of LDPE and LLDPE. General-purpose packaging bags used in factories are also PE plastic bags, such as those used for electronics, electrical appliances, hardware, plastics, clothing, and shoes.

PE plastic bags are relatively soft, but their transparency is not as high as other materials, they are relatively hazy, have good tensile strength, and are not easy to burst.

2. PP Plastic Bags

PP plastic bags, commonly known as "hundred-fold bags." Polypropylene is a representative of poly-α-olefins, a thermoplastic resin made by the polymerization of propylene, with propylene as its monomer. Depending on the initiator and polymerization process, polypropylene can be divided into three configurations: isotactic polypropylene, atactic polypropylene, and syndiotactic polypropylene. Isotactic polypropylene easily forms a crystalline state with a crystallinity of over 95% and a molecular weight between 80,000 and 150,000, giving it good heat resistance and solvent resistance; atactic polypropylene is an amorphous, slightly sticky white waxy substance at room temperature, with a low molecular weight of 3,000-10,000, an irregular structure, and a lack of cohesion, so it has limited applications. PP plastic bags are relatively hard, but have higher transparency, but the tensile strength is not very good, and they are prone to bursting.

3. PO Plastic Bags

PO plastic bags are blow-molded from high-density polyethylene (HDPE). They are non-toxic, have a waxy feel, have excellent low-temperature resistance (minimum operating temperature can reach -70～-100℃), good chemical stability, and can withstand corrosion from most acids and alkalis (not resistant to oxidizing acids). They are insoluble in common solvents at room temperature, have low water absorption, and excellent electrical insulation properties. However, polyethylene is sensitive to environmental stress (chemical and mechanical action) and has poor heat aging resistance. The properties of high-density polyethylene vary depending on the grade, mainly depending on the molecular structure and density. Different production methods can yield products with different densities (0.91～0.96g/cm3). Polyethylene can be processed using general thermoplastic molding methods (see plastic processing). PO plastic bags are relatively brittle, the transparency is not high, even hazier than PE plastic bags, somewhat translucent white, and the tensile strength is not very good.

4. OPP Plastic Bags

OPP plastic bags have the best and highest transparency, being the most bright and clear. They have the function of dust prevention and enhancing the value of the packaged product. In sales, they can fully display the products inside, so OPP plastic bags are usually used as the outer packaging for commodity sales, both protecting and beautifying the product. They are widely used in jewelry, jade, stationery, toys, tableware, kitchen utensils, clothing, and other fields. OPP plastic bags are the most brittle, have the highest transparency, but insufficient tensile strength, and are easily prone to bursting.

5. CPE Plastic Bags

CPE plastic bags are commonly used for packaging clothing and electronic products. These bags are generally divided into matte and smooth surfaces, with a comfortable and soft feel. They provide high-end packaging, making products appear more upscale and luxurious.