Density of PET Plastic | The Ultimate Guide

Density of PET

A plastic material’s density is described as the mass per unit volume of a material, generally measured in grams per cubic centimeter (g/cm³) or kilograms per cubic meter (kg/m³).

The density of PET plastic is 1.38 g/cm³ and 1370 to 1455 kg/m3.

PET plastic has a significantly lower density than other commonly used plastics like PVC (1.45 g/cm3) and Polycarbonate (1.2 g/cm3). The reduced density of PET makes it a suitable choice for various applications, including packaging, textiles, and consumer products.

Before diving into PET Density, I would like to clarify how plastic materials’ density is calculated.

What is Density?

Plastic density is a measure of the mass of a substance per unit volume. It is a fundamental physical property that can identify a material and determine its behavior under different conditions.

The density of plastics can be expressed in grams per cubic centimeter (g/cm³) or kilograms per cubic meter (kg/m³).

Regarding plastic materials, density is a critical factor in the selection process. Different types of plastic have different densities, affecting the material’s weight and strength.

The density of a plastic material also determines its ability to float or sink.

This is why plastic water bottles, for example, are made of lightweight materials such as PET, which is low density, so they are easy to carry and can float.

Factors Affecting the Density of PET Plastic

Various factors can influence the PET’s density, such as the manufacturing process, the type of resin utilized, mechanical & physical properties, and any additives incorporated into the material.

The manufacturing process plays a crucial role in determining the density of PET. For example, if the material is stretched during the manufacturing process, it will have a lower density than if it is not stretched.

This is because stretching the material increases its crystallinity, reducing the material’s density.

The type of resin used in the production of PET also affects its density.

Several types of PET resin are available, each with different properties. For example, some resins are designed for specific applications, such as packaging, while others are designed for clothing or consumer goods.

The mechanical properties of PET, such as its tensile strength, modulus of elasticity, and impact resistance, are influenced by the degree of crystallization, which, in turn, is affected by the density of the material.

Higher-density materials generally have a higher degree of crystallization and, thus, exhibit better mechanical characteristics.

Regarding physical properties, PET’s Density can also impact its transparency and optical properties.

Materials with higher density tend to display improved optical clarity and increased transparency, making them well-suited for applications in fields such as packaging, consumer goods, and electronic displays.

At last, additives such as fillers and stabilizers can also affect PET density. These additives are used to improve the general properties of the material, such as its strength or clarity.

However, they can also increase the density of the material, so it’s essential to choose the proper additives for your application.

How Does PET Density Affect its Processing Conditions?

The density of PET plastic can significantly impact its processing conditions, including temperature, pressure, and cooling rate.


The melting point of PET  is around 260°C, and its processing temperature is typically between 220-280°C. A higher processing temperature can result in a lower-density material, as it can affect the degree of crystallization.


The pressure during the processing of PET also plays a role in determining its density. High pressure can result in a denser material, while low pressure can result in a lower-density material.

Cooling rate

The cooling rate during the processing of PET is another important factor that can affect its density. A rapid cooling rate can result in a lower-density material, as it can increase the degree of crystallization. On the other hand, a slow cooling rate can result in a denser material, as it can reduce the degree of crystallization.


PET plastic is a popular material due to its advantageous combination of properties, one of which is its low density. It is essential to have a good understanding of the density of PET when choosing the appropriate material for a specific application.

The density of the material can vary due to factors such as the manufacturing process, the type of resin utilized, and the addition of any additives. With proper knowledge and expert advice, you can select the ideal PET plastic for your project and attain the desired outcome.

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