What is Plastic Polymers

Plastic polymers, or simply plastics, are a class of materials primarily composed of high-molecular-weight polymers that can be molded into shapes under certain temperatures and pressures. Polymers are macromolecular compounds formed by chemical polymerization reactions that link numerous identical or similar small molecules (called monomers). Their molecular chains can reach thousands or even tens of thousands of atoms in length. This unique molecular structure gives plastic polymers their diverse properties.

Common Plastic Raw Materials

Polyethylene is a plastic made from the polymerization of ethylene monomers. Depending on the polymerization method and molecular structure, it can be divided into low-density polyethylene (LDPE), high-density polyethylene (HDPE), and linear low-density polyethylene (LLDPE). LDPE offers excellent flexibility, transparency, and impact resistance, and is primarily used in the manufacture of plastic bags, plastic film, agricultural film, cable insulation, and more. HDPE boasts high strength, hardness, and chemical resistance, and is used in the manufacture of plastic bottles, plastic barrels, pipes, sheet metal, and automotive parts. LLDPE combines the flexibility of LDPE with the strength of HDPE, and is primarily used in the manufacture of film, pipes, and injection molded products.

Polypropylene is a plastic made from the polymerization of propylene monomers. It features low density (one of the lowest densities among commonly used plastics), high strength, high hardness, excellent heat resistance (can be used for extended periods at 100-120°C), and strong chemical resistance. Polypropylene has excellent processability and can be formed through various methods, including injection molding, extrusion, and blow molding. It is widely used in the automotive, home appliance, packaging, textile, and medical device sectors. In the automotive sector, polypropylene is used to manufacture components such as bumpers, instrument panels, and door inner panels; in the packaging sector, it is used to manufacture food packaging bags, beverage bottle caps, and disposable tableware; and in the textile sector, it is used to produce polypropylene fibers for clothing, carpets, and fishing nets.

PVC is a plastic made from the polymerization of vinyl chloride monomer. Depending on the plasticizer content, polyvinyl chlorine can be divided into rigid polyvinyl chloride (UPVC) and flexible polyvinyl chloride (SPVC). Rigid PVC offers high strength, hardness, and chemical resistance, and is primarily used in the manufacture of plastic doors and windows, pipes, panels, and profiles. Soft PVC, with its excellent flexibility and elasticity, is used in the manufacture of wire and cable insulation, plastic film, artificial leather, toys, seals, and more. PVC is relatively inexpensive and widely used, but its processing and use may release harmful gases, which can have certain impacts on the environment and human health. Therefore, its application is subject to certain restrictions.

Polyethylene terephthalate (PET) is a plastic formed by the polymerization of terephthalic acid and ethylene glycol. It features excellent transparency, high strength, impact resistance, chemical resistance, and airtightness. PET is primarily used in the manufacture of beverage bottles (such as mineral water and cola bottles), food packaging film, textile fibers (such as polyester), and films (such as magnetic tape and videotape base films). Due to its excellent recyclability, PET has become one of the most widely recycled plastics.

PS is a plastic made from the polymerization of styrene monomers. It exhibits excellent transparency, insulation, and processability, but is also brittle and has poor impact resistance. Polystyrene is primarily used in the manufacture of foam plastics, disposable tableware, electronic and appliance casings, toys, and decorative items. Among these, expanded polystyrene (EPS) boasts lightweight, thermal and sound insulation properties and is widely used in packaging and building insulation. High-impact polystyrene (HIPS), which enhances its impact toughness by adding modifiers such as rubber, is used in the manufacture of appliance casings and automotive parts.

As a leading supplier of plastic resin raw materials, Fengbai company can supply various kinds of plastic polymers for you, including LLDPE, HDPE, LDPE,PP, PVC, PET, EVA, EAA, ABS, PC,PS,POM,POE,POP,etc. More information about these plastic resin granules or powder, please check the below product list. Of course, if you need some plastic raw materials, please contact us online to get a quote!

  • Common-purpose plastics are high-volume, versatile, and affordable plastics. They primarily include polyethylene, polypropylene, polyvinyl chloride, polystyrene, and ABS resin. They are widely used in packaging, agriculture, construction, daily necessities, electronics, and other fields, and are fundamental to the plastics industry. For example, polyvinyl chloride can be used to make plastic doors and windows, pipes, wallpaper, and toys; polystyrene can be used to make foam plastics, disposable tableware, and electronic and appliance casings; and ABS resin, with its excellent overall properties, is used in automobile dashboards, appliance casings, and toys.
  • Engineering plastics are plastics that exhibit high strength, stiffness, toughness, heat resistance, and corrosion resistance, enabling them to withstand the loads of engineering structures. Common engineering plastics include polyamide (PA, commonly known as nylon), polycarbonate (PC), polyoxymethylene (POM), polyphenylene ether (PPO), and polytetrafluoroethylene (PTFE). Engineering plastics are widely used in the automotive, aerospace, electronics, and machinery industries to manufacture precision components and structural parts. For example, polyamide can be used to manufacture gears, bearings, oil pipes, and seals. Polycarbonate, with its excellent transparency and impact toughness, is used in automotive lampshades, eyeglass lenses, optical discs, and bulletproof glass. Polytetrafluoroethylene, known as the “King of Plastics,” boasts excellent corrosion and high-temperature resistance and is used in chemical equipment linings, seals, and non-stick coatings.
  • Specialty plastics are plastics with specialized properties, such as high- and low-temperature resistance, radiation resistance, flame retardancy, electrical conductivity, and thermal conductivity, designed for specialized applications. These plastics, primarily polyimide (PI), polyetheretherketone (PEEK), polysulfone (PSU), and polyphenylene sulfide (PPS), have low production volumes and high prices. They are widely used in high-end sectors such as aerospace, military, electronics, and medical devices. For example, polyimide can be used to manufacture high-temperature-resistant films, composite materials, and electronic components. Polyetheretherketone, with its excellent high-temperature resistance and mechanical properties, is used in aerospace parts and medical devices.

Thermoplastics generally soften and melt when heated, then solidify and form upon cooling, a process that can be repeated. Due to their excellent processability and recyclability, thermoplastics are widely used in industrial production and daily life. Common examples include polyethylene (PE), polypropylene (PP), polyvinyl chloride (PVC), polystyrene (PS), and polyethylene terephthalate (PET). For example, polyethylene is used to make plastic bags, bottles, and pipes; polypropylene is used to produce automotive parts, appliance housings, and textile fibers.

Thermosetting plastics soften initially during heating and exhibit a certain degree of plasticity. However, as heating increases, the molecular chains undergo cross-linking reactions, forming an insoluble, infusible three-dimensional network structure. Upon cooling, the material solidifies and does not soften or melt even after further heating. Thermosetting plastics have high heat resistance, corrosion resistance and dimensional stability, and are mainly used to manufacture parts with high performance requirements. For example, phenolic resin (PF) can be used to make electrical switches, sockets, brake pads, etc.; epoxy resin (EP) can be used to make coatings, adhesives, composite materials, etc.; unsaturated polyester resin (UPR) can be used to make fiberglass products, artificial marble, etc.

(I) Molecular Chain Structure

The molecular chains of plastic polymers primarily have three types of structures: linear, branched, and cross-linked. Linear molecular chains are long, thin chains with weak intermolecular forces. These plastics typically exhibit good plasticity and solubility, such as polyethylene and polypropylene. Branched molecular chains have numerous branches attached to the main chain, which affect the molecular chain packing density and, in turn, alter the plastic’s density, crystallinity, and other properties. For example, low-density polyethylene has a lower density due to its numerous branches. Cross-linked molecular chains, in which molecular chains are interconnected by chemical bonds, form a three-dimensional network structure. This gives the plastic high strength, heat resistance, and solvent resistance, but poor plasticity. Examples include thermosetting plastics such as phenolic resin and epoxy resin.

(II) Crystallinity

Based on the spatial arrangement of the molecular chains, plastic polymers can be divided into two categories: crystalline and amorphous. Crystalline plastics, such as polyethylene, polypropylene, and polyamide, have molecular chains that are regularly arranged to form a crystal structure, exhibiting high melting points, strength, and hardness. Amorphous plastics, such as polyvinyl chloride, polystyrene, and polycarbonate, have disordered molecular chains and no distinct melting point, but generally exhibit good transparency and toughness. However, most plastic polymers are neither completely crystalline nor completely amorphous, but rather a coexistence of crystalline and amorphous portions, and the degree of crystallinity significantly affects the material’s properties.

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