The Density Of Plastics | The Complete Guide

Hello everybody. Today I will 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 in plastics 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 solvent absorption, plasticizer loss, and crystallinity change.

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 thing. However, you might need to use different methods to determine the importance of any object; as far as calculating density is concerned, it will be calculated similarly 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 establishing 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. You should prefer consulting your supplier to get an accurate value for the material you want to work with. 

What is the Bulk Density of Plastic Materials?

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 the 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 material weights.

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, the hopper size is significant to ensure the correct output of dried material for processing at the right time.

How Does Plastic’s Density Affect Its Other Properties?

Strength and rigidity: Plastics with a higher density frequently display increased tensile strength and rigidity, making them appropriate for demanding applications. For example, due to its exceptional sturdiness, high-density polyethylene (HDPE) is commonly employed in various industries, such as packaging, automotive parts, and building materials.

Durability: Plastics with a higher density generally exhibit enhanced resistance to wear, abrasion, and impact. This improved resilience makes them perfect for durable products like pipe networks and exterior furnishings.

Thermal Conductivity: Density influences a plastic’s heat transfer capacity. Higher-density materials usually possess more extraordinary thermal properties, enabling them to disperse heat more efficiently. This attribute is advantageous in situations that demand temperature stability, including electronic components and automobile parts.

Buoyancy: Less dense plastics have a lower specific gravity than water, allowing them to float. This characteristic is essential for the design of flotation devices, marine equipment, and water sports gear.

Transparency: Low-density plastics are often more transparent than their high-density counterparts due to the reduced molecular packing. This property is vital for applications that require clear visibility, such as food packaging and eyewear lenses.

Processability: Low-density plastics are generally easier to process, as they have lower melting points and require less energy for molding. Consequently, they are more cost-effective for mass production, particularly in applications where strength and durability are not primary concerns.

Barrier properties: Plastic material density can impact its resistance to gas and moisture permeation. High-density materials generally exhibit superior barrier properties, making them suitable for preserving perishable goods or protecting sensitive electronics.

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.

What are the 7 types of plastic?

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.

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

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.

Which is the toughest plastic in the world?

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

Why is density in plastic important?

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 selecting the storage costs, which can add a substantial sum to the overall expenses.