What is the Density of Plastics? | The Complete Guide

Hello everybody. Today I’m going to share a deeply researched guide on the density of plastics. So without further ado, let’s get started.

What is the Density of Plastic Materials?

Density is the measurement of mass per unit volume. It is calculated by dividing the material’s mass by volume and is generally expressed in g/cm3. The density of plastics usually varies with temperature changes. It may also change due to absorption of solvent, loss of plasticizers, and change in crystallinity.

Therefore to figure the accurate density of plastic material, certain things need to be taken care of, such as:

• Identifying the material
• Observe and follow the physical changes in the specimen
• Specify the consistency among different Samling specimens
• Specify the average density of a large item
• Calculate the strength weight and cost-weight ratios

How to Calculate The Plastic Density

The density of any object and its substance is found by dividing the object’s total mass by the total volume of the object. However, you might need to use different methods to determine the volume of any object; as far as calculating density is concerned, it will be calculated in the same way by this formula.

There are several methods to determine density, but the below are the most common ones:

• ASTM D1505
• ASTM D792-98
• ISO 1183-2

ASTM D1505

ASTM S1505 testing method uses the Density-gradient technique to determine the density of a material. Here, the material is kept in a liquid column of variable density with glass beads. The material’s relative density to the floats in the column and the density of the glass beads determine the density.

ASTM D792-98

ASTM D792-98 describes the establishment of the specific gravity and density of solid plastics in forms like rods, sheets, tubes, or molded items. There are mainly two methods involved in the process:

• Test Method A – For testing solid plastics in water
• Test Method B – For testing solid plastics in other liquids

ISO 1183-2

The method includes a gradient column technique for establishing the density of extruded plastics or non-cellular plastics in void-free form. Density gradient columns consist of two liquids that consistently increase density in the column from top to bottom.

Below is the chart showing the density values of all mainstream plastics.

Interesting Read – What is Hardness in Plastics? An In-Depth Guide

The Density of Plastics – Minimum and Maximum Values

Disclaimer – All the values mentioned in the table are well researched and come from reliable sources but are shared for knowledge purposes. To get an accurate value for the material you want to work with, you should prefer consulting your material supplier. 

What is the Bulk Density of Plastic Materials?

The bulk plastic density is the weight of material based on a given volume. Bulk density is expressed in three different ways:

• Pounds per cubic foot (lb/cu ft)
• Grams per cubic centimeter (g/cc)
• Kilograms per liter (kg/l)

Bulk densities differ for every plastic material. Therefore, manufacturers measure productivity based on the weight of plastic material processed through their equipment.

Why is Bulk Density of Plastic Materials Important?

Bulk plastic density affects material storage. For example, plastic material is often stored or packed in a specific size container. Although resin pellets of different materials have different bulk densities, similar-sized containers of different materials will possess drastically different weights of material.

Bulk density also affects the sizing of drying equipment. For the drying operations to remain smooth, the required weight of the material must be dried at the right temperature for the correct residence time. Therefore, to ensure the right output of dried material for processing at the right time, the size of the hopper is significant.

Fascinating Read – Melting Point of Plastics | The Ultimate Guide

FAQs 

Below are the frequently asked questions further expanding the topic of plastic density. Let’s have a look.

1. What are the 7 types of plastic?

Ans. Below are 7 types of plastics:

1.  Polyethylene Terephthalate (PET or PETE)
2. High-Density Polyethylene (HDPE)
3. Polyvinyl Chloride (PVC or Vinyl)
4. Low-Density Polyethylene (LDPE)
5. Polypropylene (PP)
6. Polystyrene (PS or Styrofoam)
7. Other.

2. What is the density of a bottle cap made from polypropylene?

Ans. Plastic bottle caps made from polypropylene have a density of 0.92 grams per cubic centimeter, which is lighter than seawater’s average density of 1.027 grams per cubic centimeter, and, therefore, float in seawater.

3. Which is the toughest plastic in the world?

Ans. Polycarbonate is the toughest plastic in the world in terms of impact strength. It is said to be 200 times stronger than glass.

4. Why is density in plastic important?

Ans. Because the bulk densities of all the plastic materials differ, plastic processors often measure productivity based on weight. Therefore, calculating the amount (kilograms or tons) of plastic materials through their equipment matters greatly.

Suggested Read –

• What is Shore Hardness Scale? | The Complete Guide
• 6 Best Plastic Molding Techniques | A Complete Analysis
• What is the Best Glue for Plastic Parts | The Ultimate Guide
• Types of Gates for Injection Molding – A Detailed Guide
• What is Processing and Drying Temperatures of Plastics
• What is Condensation Polymerization? | The Definitive Guide
• Mold Temperature in Plastics | A Complete Analysis
• Food Grade Plastic: The Best Plastics for Food Applications

The Conclusion – 

That was all I had to say about the density of plastic materials. Kindly check the table properly to get an idea about the materials’ density you want to work with. Determining the density can play a crucial role in production and activities; it will be integral for producing quality products and determining the storage costs, which can add a substantial sum to the overall expenses.