Comparison of Tensile Strength of Common Plastics

Tensile strength is a critical mechanical property that determines a plastic's resistance to breaking under tension. It is essential for structural design, material selection, and ensuring product durability. The following data is based on standard test results (ASTM D638 / GB/T 1040) and is divided into two main categories: General Purpose Plastics and Engineering Plastics.

1. General Purpose Plastics

General Purpose Plastics are characterized by high production volume, low cost, and ease of processing. Their tensile strength is generally moderate to low, suitable for light-load applications.

LDPE (Low-Density Polyethylene): Tensile strength ranges from 8–20 MPa. It has a highly branched molecular structure, resulting in a soft and flexible material with poor tensile resistance. It is primarily used for films, plastic bags, and packaging liners.

HDPE (High-Density Polyethylene): Tensile strength ranges from 21–38 MPa. With a more linear structure and higher crystallinity than LDPE, it offers better rigidity and chemical resistance. Common applications include crates, pipes, and household containers.

PP (Polypropylene): General grade tensile strength is 30–40 MPa. It offers a good balance of rigidity and fatigue resistance. When reinforced with 20–30% glass fiber, strength increases to 40–60 MPa. It is widely used in automotive bumpers, appliance housings, and medical trays.

Rigid PVC (Polyvinyl Chloride): Tensile strength ranges from 45–60 MPa, the highest among general plastics. It is rigid, weather-resistant, and flame-retardant, making it ideal for window profiles, pipes, and construction materials.

Flexible PVC: Tensile strength ranges from 10–25 MPa. Plasticizers are added to provide flexibility and elasticity. It is used for wire insulation, seals, and hoses but has a low heat resistance (limited to 60°C).

PS (Polystyrene): Tensile strength ranges from 40–60 MPa. It is rigid and hard but very brittle with low impact resistance. It is suitable for stationery, toy casings, and transparent packaging due to its good surface finish.

ABS (Acrylonitrile Butadiene Styrene): General grade tensile strength is 41–45 MPa. This terpolymer balances rigidity (from acrylonitrile), toughness (from butadiene), and processability (from styrene). Glass fiber reinforcement can increase strength to 60–80 MPa, used in dashboards, phone cases, and washing machine parts.

2. Engineering Plastics

Engineering Plastics exhibit superior mechanical properties, heat resistance, and durability. Their tensile strength is high, suitable for heavy-load and harsh environment applications.

PC (Polycarbonate): General grade tensile strength ranges from 55–75 MPa. It is known for exceptional impact resistance and transparency. With 30% glass fiber reinforcement, strength reaches 80–120 MPa. It is used for automotive headlamps, safety shields, and electronics.

PA6 (Nylon 6): Unmodified tensile strength is 70–85 MPa. It has strong intermolecular hydrogen bonding, providing excellent wear resistance. With 30% glass fiber reinforcement, strength jumps to 180–220 MPa, suitable for gears, bearings, and engine parts.

PA66 (Nylon 66): Unmodified tensile strength is 80–90 MPa. It has a more regular structure than PA6, offering higher strength and heat resistance. Reinforced strength reaches 160–210 MPa, used in transmission components and aerospace fasteners.

POM (Polyoxymethylene / Acetal): General grade tensile strength ranges from 60–75 MPa. It is a high-crystallinity plastic with excellent fatigue resistance and dimensional stability. Reinforced strength is 90–120 MPa, ideal for precision gears and mechanical parts.

PMMA (Acrylic): Tensile strength ranges from 48–70 MPa. While mechanically weaker than other engineering plastics, it offers 92% light transmittance. It is brittle and prone to stress cracking, used in optical lenses and light boxes.

PBT (Polybutylene Terephthalate): Unmodified tensile strength is 50–65 MPa. It has good heat resistance and fast crystallization. With 30% glass fiber reinforcement, strength reaches 120–150 MPa, commonly used in connectors and electrical components.

PPS (Polyphenylene Sulfide): Unmodified tensile strength is 70–80 MPa. It is a high-performance plastic with extreme heat and chemical resistance. With 40% glass fiber reinforcement, strength reaches 130–160 MPa, suitable for aerospace and chemical processing parts.

3. Selection Summary

General Purpose Plastics (8–60 MPa): Choose PP, HDPE, or ABS for cost-effective, light to medium load applications.

Engineering Plastics (48–220 MPa): Choose Glass Fiber Reinforced PA or PPS for heavy-load, high-temperature, or wear-resistant applications.

Reinforcement: Adding glass fibers is the most effective way to increase tensile strength, often improving it by 50% to 200%. Selection should be based on load requirements, operating temperature, and budget.