Table of Physical Properties of Common Plastic Materials

Plastics are polymers and can be categorised into thermoplastics and thermosetting plastics based on their properties in terms of strength and heat resistance. That's the classification that underlies their various industrial uses. This comparison shows you the key physical properties of each of these materials and their performance differences.

Thermoplastics

Thermoplastics are those which can be softened when heated again and then be cut again. It is a feature of their linear or slightly branching polymers, not cross-linked. Thermoplastics tend to be less stiff than thermosetting plastics, and are therefore softer and more malleable for flexible use. But they are a bit coarser than their thermosetting cousins.

Polymer	Density (ρ, kg/m3)	Tensile Strength (σ, MPa)	Elongation (%)	Young's Modulus (E, GPa)	Brinell Hardness Number
Acrylic (metacrylate)	1190	74	6	3	34
Cellulose Acetate	1300	40	10 - 60	1.4	12
Cellulose Nitrate	1350	48	40	1.4	10
Nylon	1160	60	90	2.4	10
Polyethylene	950	20 - 30	20 - 100	0.7	2
Polypropylene	900	27	200 - 700	1.3	10
Polystyrene	1050	48	3	3.4	25
PTFE (fluoropolymer)	2100	13	100	0.3
PVC	1330	48	200	3.4	20

The standard ones are polyethylene (PE), polyvinyl chloride (PVC), and polystyrene (PS), which differ with respect to their mechanical and thermal properties. PE, for example, is prized for being highly chemically resistant and hard, and PVC is used widely in construction due to its resilience and resistance to fire.

Thermosetting Plastics

When thermosetting plastics are moulded, they're subject to a permanent chemical change called curing. This reaction is induced through heat and pressure to produce a highly cross-linked polymer network. Therefore, the thermosets cannot be resoftened or modified after cure, and hence they are more hard and rigid.

Thermosetting plastics tend to be harder and brittle than thermoplastics and can be used for applications with extreme strength that need to resist heat. Epoxy resins, phenolic resins, and urea-formaldehyde, for instance, are used as coatings, adhesives, or electrical insulators.

Polymer	Density (ρ, kg/m3)	Tensile Strength (σ, MPa)	Elongation (%)	Young's Modulus (E, GPa)	Brinell Hardness Number
Acetals, glass filled	1600	58 - 75	2-7	7	27
Epoxy resin, glass filled	1600 - 2000	68 - 200	4	20	38
Melamine formaldehyde, fabric filled	1800 - 2000	60 - 90		7	38
Phenol formaldehyde, mica filled (phenolic)	1600 - 1900	38 - 50	0.5	17 - 35	36
Urea formaldehyde, cellulose filled	1500	38 - 90	1	7-10	51

• 1 MPa = 0.1 GPa = 1 N/mm²
• 1 N/m² = 1 Pa = 10^-6 N/mm² = 1.4504x10^-4 psi

Comparison of Thermoplastics and Thermosetting Plastics

Property	Thermoplastics	Thermosetting Plastics
Thermal Behavior	Softens upon reheating	Irreversible curing
Molecular Structure	Linear or slightly branched	Cross-linked network
Rigidity	Less rigid	More rigid and harder
Brittleness	Flexible and less brittle	Brittle
Recyclability	Recyclable through reheating	Non-recyclable after curing
Common Applications	Packaging, piping, containers	Electrical insulators, coatings