Specific weight, bulk weight and density of plastic
Plastic has become a universal material that is used almost everywhere. It became widely used thanks to its practical advantages. The remarkable strength of plastics has made it possible to replace many more expensive materials.
Specific weight and density of plastics
The density of plastics is much lower than the density of metal, stone and concrete structures. However, only one type of material can compete with plastic in strength — metal. In the process of manufacturing various structures and products, plastic takes different forms and can be stretched and bent well. When certain types of binders are used, plastics can be comparable in strength to wooden structures.
The specific weight of plastic varies depending on the binder used. Thus, the bulk density of polyethylene is 0.9 g/cm³, while the weight of fiberglass plastic will be significantly higher — 1.95 g/cm³.
| Name | Mass of 1 m³ in tonnes | Mass of 1 m³ in kilograms | Specific weight (kg/m³) |
| Weight of 1 m³ of plastic | 0.85 - 1.8 | 850 - 1800 | 850 - 1800 |
Several types of plastics are distinguished depending on their elasticity properties. Their functional characteristics are shown in the table.
| Parameter / type | Rigid | Semi-rigid | Soft |
| Permeability | Impermeable | Affected by gases, vapors, water and air masses | |
| Elasticity | Absent | Low | Very high |
| Resistance to temperature changes | 300 - 400 °C | >70 °C | >50 °C |
| Thermal expansion | Within 25 - 120 · 10⁻⁶ | ||
| Resistance to low temperatures | Very high | Moderate | Low |
| Hardness measurement | 40 HB | 2 - 20 HB | |
| Protection against chemicals | High degree of protection | ||
| Ability to retain heat | They can retain heat well and conduct it poorly | ||
| Electrical conductivity | Used as a dielectric or electrical insulator | ||
| Degree of light permeability | Transmit light well if they are not made with a colored filler | ||
| Ability to retain color | Very high when the correct coloring elements are used (ochre, red lead, etc.) | ||
Based on the data shown in the table, it can be concluded that plastics are resistant to most chemicals. They are often used in the chemical industry to protect structural elements. Particularly resistant plastics include Teflon, polyethylene, polyisobutylene, polystyrene and polyvinyl chloride.
Disadvantages of using plastics
The disadvantages of plastics depend on the particular polymer, fillers and additives. Many plastics are sensitive to high temperatures, are less hard than metals and may support combustion, although flame-retardant and self-extinguishing grades also exist. When plastic structures are used inside or outside residential premises, flammability class, smoke generation and fire safety requirements must be considered.
There is a concept called plastic aging, which means the loss of some material properties during long-term use. In addition, exposure to sunlight and air gradually destroys plastic products and structures. The following causes start the aging process:
- Breakage of the molecular chain of the polymer substance.
- Rearrangement of the molecular structure.
As a result, strength and elasticity decrease, the color changes, and the product becomes brittle. During strong heating, burning or degradation, some plastics can release harmful decomposition products, so operating and disposal conditions should be considered in advance.
Frequently Asked Questions
How much does 1 m³ of plastic weigh?
According to the table, 1 m³ of plastic weighs roughly 850 to 1800 kg. This is a broad range for different plastics; the exact value depends on the polymer, fillers, reinforcement and manufacturing method.
Why do different plastics have such different density?
Plastic is not a single material but a large group of polymers. Polyethylene and polypropylene are usually lighter, while glass-filled, mineral-filled and some engineering plastics are much heavier.
Can an average plastic density be used to calculate the weight of a part?
For a rough estimate, the table range is acceptable. For the weight of a specific part, it is better to know the exact plastic type and multiply the part volume by the density stated in the material datasheet.