Understanding the Specific Gravity of Plastics

Introduction

The weight of a material sample divided by the weight of an equivalent amount of water is known as its specific gravity. The density and specific gravity of plastics (relative density) ISO 1183-1 outlines the general test method, similar to the ASTM D792.

Specific Gravity: What is it?

The ratio between the mass density of a substance and that of a reference substance. It carries no units. The specific gravity of plastic films varies depending on the type of plastic—for instance, the particular nylon gravity plastic ranges typically between 1.13 and 1.15. The reference material for plastics is usually water at 60 or 70 degrees Fahrenheit. Specific gravity, as it applies to plastics, is calculated as the density of the plastic divided by the density of water. As a dimensionless unit of measure, it is highly significant in material science to understand the behavior and properties of materials, one of which involves plastics.

Read more: How Symbols Contribute in Understanding Plastics

Significance of Specific Gravity of Plastics 

Why Specific Gravity Matters for Plastics?

It plays an essential role in the use of plastics. It assists in the performance and application of various types of plastics. For instance, plastics with high specific gravity are usually solid and heavy. They are generally used in places where high durability and strength are requested. On the other hand, plastics possess low specific gravity and are lighter. They are usually used in areas of flotation or thermal insulation. Specific gravity can also be applied to separate types of plastics in recycling processes.

Procedure of Specific Gravity of Plastics 

How to Calculate the Specific Gravity of Plastics?

It is determined by dividing the density of plastic by the density of water. This yields a dimensionless number that describes the relative density of the material. The density of plastic depends on temperature. Therefore, it is advisable that the measurement of specific gravity be carried out at constant temperature for proper results. There are different methods to measure the density of plastics, such as using a pycnometer or the displacement method.

Specific Gravity of Plastics Chart

Results

Plastics generally have specific gravities ranging from 0.9 to 2.2, which is less than water’s specific gravity. However, a few plastics, like a few kinds of PVC or PET, may possess higher specific gravity due to the addition of some fillers or additives that increase density. By comparing the specific gravities of different plastics, one may identify the type of plastic used for recycling.

Industrial Applications and Implications

• Specific gravity has massive applications in several vital industries. At the manufacturing stage, it estimates quality and further application in a particular field.
• Specific gravity is used in the recycling industry to sort mixed plastic polymer types and in the design and engineering of plastic products.
• This will also help us understand how to predict their behavior in different working environments. This is especially applicable in industries like automotive and construction.

Conclusion

In the final analysis, understanding specific gravity encompasses many significant issues in diverse areas, from manufacturing to recycling, including product design and environmental impact. The line also supplies several resources and tools that will further facilitate studying. Using these, the professionals concerned can effectively measure and analyze the specific gravity of plastics.

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