Types and Properties of Common Engineering Plastics
I. Thermoplastic
Polyethylene (PE)
Key Properties: High-density polyethylene (HDPE) is flexible, transparent, and non-toxic; Low-density polyethylene (LDPE) is rigid, wear-resistant, corrosion-resistant, and offers good electrical insulation.
Application Examples: High-density polyethylene: Films, hoses, plastic bottles; Low-density polyethylene: Chemical equipment, pipelines, low-load gears, bearings, etc.
Polypropylene (PP)
Key Characteristics: Strength, hardness, and elasticity exceed those of polyethylene; Low density; Good heat resistance; Excellent electrical insulation and corrosion resistance; Poor toughness; Poor abrasion resistance; Prone to aging.
Application Examples: Flanges, gears, fan impellers, pump impellers, handles, television (recorder) casings, chemical pipelines, containers, medical devices, etc
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Polyvinyl Chloride (PVC)
Key Characteristics: High strength and good corrosion resistance. Flexible PVC exhibits high elongation, yielding soft products with good corrosion resistance and electrical insulation.
Application Examples:Exhaust gas scrubbers, gas/liquid transfer pipes, centrifugal pumps, ventilators, connectors; Flexible PVC: films, raincoats, acid/alkali-resistant hoses, cable sheathing, insulation layers, etc.
Polystyrene (PS)
Key Characteristics: Good corrosion resistance, electrical insulation, and transparency; moderate strength and rigidity; limited heat resistance and abrasion resistance; poor impact resistance; flammable and prone to brittle fracture.
Examples of Applications: Spool tubes, yarn bobbins, thread spools; instrument components, equipment housings; storage tanks, pipes, elbows; lampshades, transparent windows; electrical insulation materials, etc.
ABS Plastic
Key Characteristics: High strength and impact toughness, good wear and heat resistance, high chemical stability and insulation, easy to form, good machinability, poor high/low temperature performance, flammable, opaque.
Examples of Applications: Gears, bearings, instrument panel housings, refrigerator linings, various containers, pipes, aircraft cabin interior panels, window frames, soundproofing panels, etc. Also used for automotive parts such as car bodies, fenders, armrests, and hot air conditioning ducts.
Polyamide (PA) (Nylon)
Key Characteristics:Excellent strength, toughness, wear resistance, corrosion resistance, vibration damping, and self-lubrication. Good formability, non-toxic, odorless. High creep value, poor thermal conductivity, high moisture absorption, significant molding shrinkage.
Application Examples: Nylon 610, 66, 6, etc., for small components (gears, worm gears, etc.); aromatic nylon for high-temperature wear-resistant parts, insulation materials, and space suits.Note: Nylon properties and dimensions change significantly upon water absorption.
Polycarbonate (PC)
Key Properties: High tensile and flexural strength, excellent impact toughness and creep resistance, superior heat and cold resistance, high dimensional stability, high transparency, low water absorption, good electrical insulation and processability, poor chemical stability.
Applications: Insulating components (washers, gaskets, sleeves, capacitors);Instrument housings and protective covers; Signal lights, windshields, canopies, and helmets in aerospace manufacturing
. Polytetrafluoroethylene (PTFE, "Plastic King")
Key Properties: Exceptional chemical resistance, superior high/low temperature performance, low friction coefficient, minimal water absorption, low hardness and strength, limited compressive strength, relatively high cost.
Application Examples: Friction-reducing sealing components, chemical-resistant parts for heat exchangers, and insulating materials for high-frequency or humid environments—e.g., chemical pipelines, electrical equipment, and corrosive medium filters
. Polymethyl Methacrylate (PMMA)
Key Properties:92% light transmittance, half the density of glass, high strength and toughness, UV resistance and atmospheric aging resistance, easy to form, low hardness, poor abrasion resistance, soluble in organic solvents, poor heat resistance and thermal conductivity, high coefficient of thermal expansion
Application Examples: Aircraft canopies, turret observation port covers, instrument lamp covers, optical lenses, bulletproof glass, television and radar display screens, automotive windshields, protective covers for instruments and equipment, etc.
II. Thermosetting Plastics
Phenolic Resin (PF)
Key Characteristics: Moderate strength and hardness, high abrasion and heat resistance, excellent electrical insulation and corrosion resistance, high rigidity, low moisture absorption, minimal deformation, simple molding process, and low cost. Disadvantages include brittleness and poor alkali resistance.
Applications:Plugs, switches, telephones, instrument enclosures, automotive brake pads, internal combustion engine crankshafts, pulleys, silent gears in textile machinery and instruments, acid-resistant pumps for chemical use, daily necessities, etc.
Epoxy Resin (EP)
Key Characteristics: High specific strength, good toughness, heat/cold resistance, corrosion resistance, insulation, waterproofing, moisture resistance, mold resistance, excellent formability, and dimensional stability.Toxic, high cost
Examples of Applications: Plastic molds, precision measuring tools, electrical potting compounds, formulation of aircraft paints, oil tanker paints, can coatings, printed circuit boards, etc.
