1. Why General-Purpose Plastics Matter in Industry
General-purpose plastics typically comprise five major families - polyethylene (PE), polypropylene (PP), polyvinyl chloride (PVC), polystyrene (PS) and ABS resin - which together account for roughly 70% of global plastics consumption and form the backbone of the polymer materials industry. They sit at the center of the chemical value chain, linking bulk feedstocks such as petroleum, natural gas, coal and salt to pillar downstream sectors including packaging, construction, home appliances, automotive and agriculture. Thanks to readily available feedstocks, mature processing technologies and low cost, general-purpose plastics have become the highest-volume and most widely used family of synthetic materials.
2. What Are the Upstream Raw Materials of General-Purpose Plastics?
The upstream raw materials fall into three systems:
Petroleum and natural gas - the dominant feedstock route. Crude oil is refined into naphtha, which is cracked in steam crackers to yield basic olefins such as ethylene and propylene. Polymerization of ethylene yields polyethylene, and polymerization of propylene yields polypropylene. Ethane and propane extracted from natural gas can also serve as cracking feedstocks.
Coal - the coal-chemical route. Coal is gasified to synthesis gas, converted into methanol, and then transformed into ethylene and propylene via methanol-to-olefins (MTO) technology for the production of polyethylene and polypropylene. In the carbide route, coal is converted into calcium carbide, which reacts with water to generate acetylene; acetylene then adds hydrogen chloride to form vinyl chloride monomer (VCM), the feedstock for polyvinyl chloride (PVC).
Salt - the chlor-alkali route. The chlor-alkali industry electrolyzes salt to produce chlorine and caustic soda. VCM is manufactured by two routes: the ethylene route, in which ethylene and chlorine first form 1,2-dichloroethane (EDC) followed by thermal cracking to remove hydrogen chloride; and the acetylene route, in which acetylene and hydrogen chloride combine directly. Polymerization of VCM yields PVC. In addition, styrene is produced from benzene and ethylene via ethylbenzene dehydrogenation, acrylonitrile via ammoxidation of propylene, and butadiene is extracted from the C4 fraction of naphtha cracking - these three monomers are the building blocks of polystyrene and ABS resin.
3. Downstream Products and Their Composition
|
Polymer |
Key composition (monomer) |
Typical downstream products |
|
Polyethylene (PE) |
Ethylene homopolymer (LDPE, HDPE); ethylene/α-olefin copolymer (LLDPE) |
Packaging films, plastic bags, blow-molded containers, pipes, crates |
|
Polypropylene (PP) |
Propylene homopolymer or copolymer |
Woven bags, food packaging, automotive bumpers and interior parts, appliance housings, consumer goods |
|
Polyvinyl chloride (PVC) |
Vinyl chloride polymer (typically compounded with plasticizers, stabilizers and other additives) |
Water and drainage pipes, window and door profiles, wire and cable sheathing, artificial leather |
|
Polystyrene (PS) |
Styrene homopolymer (expandable grades: EPS/XPS) |
Insulation boards, foam cushion packaging, transparent consumer goods |
|
ABS resin |
Acrylonitrile-butadiene-styrene terpolymer |
Appliance housings, electronic device casings, automotive interior parts, toys |
