It is common knowledge that as important and efficient as metal is, plastics can be equally efficient and valuable as well. Therefore, determining the hardness of plastics is paramount, which is why engineers and quality professionals often consider the properties of plastic as a possible substitution for metal. This article will help you understand how to test plastic’s hardness, which is a requirement for most production processes. So, stick around if you want to know more.
I. What is the Hardness of Plastic?
Have you ever wondered what the hardness of plastic is? Generally, the hardness of any material is its ability to maintain resistance to irreversible indentation. Therefore, the hardness of plastic can be referred to as its ability to preserve itself from perforation by a harder force or body. Plastic hardness helps engineers construct durable industrial parts and consumer products. And its cosmetic effects can be visible, which may also lead to loss of gloss surface when wear occurs on moving parts.
II. Why is Hardness in Plastics so Important?
The primary importance of measuring hardness in plastics is ascertaining the quality of the plastic material before it is infused into the production of industrial components or consumer products. Plastics have become extremely valuable in many products, hence their application in industrial production. Although materials such as metal or copper are typically applicable, plastic also offers inexhaustible qualities. Therefore, hardness in plastics ensures their durability and strength, which further implies a level of quality.
III. What are the Types of Plastic?
As earlier mentioned, the quality of material deployed in any production determines the product’s performance. With plastic products, the type of plastic employed is an essential factor in the product’s performance. There are different types of plastic prevalent in hardness testing. Some are thermos-plastics, Formica, Plexiglas, thermos-polystyrene, cellulose acetate, etc. Similarly, plastic sheets and molded parts are frequently tested for hardness.
IV. How do you Test the Hardness of Plastic?
Hardness testing in plastic saves time and cost because of its simplicity. An external force is applied in hardness testing for plastics to ascertain resistance. The indenter which provides the force is applied to the center of the test sample at a particular pressure till the presser presses into the plastic. The depth of the indenter’s penetration determines the level of hardness. If the indenter penetrates deeply, it is a soft plastic, and vice versa.
V. Methods for Plastic Hardness Testing
Here are the standard hardness testing methods available in the industry.
- Rockwell Hardness Test
This hardness testing method is usually deployed to measure harder materials such as steel, acetal, polymethacrylates, etc. Consequently, it can also be deployed for hardness testing in harder plastics. When using the Rockwell hardness method in plastics, a 6.35mm thick sample is concaved by a steel ball. An initial preload is applied before a bigger load is applied and then removed. The indentation can be read from the scale after a brief period, with the preload still in place. The depth and shape of the concavity and the time taken to complete the test prove the hardness of the material. The Rockwell hardness scales for plastics are typically Rockwell E, M, and R.
- Shore Hardness Test
On the other hand, the Shore hardness test uses a spring-loaded needle for plastic hardness testing. And like other hardness testing methods, a force is applied to the needle. This penetrates the plastic as far as it can, then measurement of the indentation depth estimates the plastic’s hardness. The Shore hardness scales used for measurement are usually Shore A and Shore D.
- Vickers Hardness Test
The Vickers hardness method is similar to the other testing methods. But with Vickers hardness testing, the indenter is diamond-shaped, and measurements can be done when the load is applied on the test sample and after the load is removed from the test sample. Vickers hardness test is designated as HV or DPH (Diamond Pyramid Hardness).
VI. How do you Increase the Hardness of Plastic?
An increase in plastic hardness can be done in the following ways.
By Blending – High-hardness resin can be blended with low-hardness resin to increase overall plastic density.
By Composite Modification – Another way of increasing plastic hardness is by fusing a layer of high-hardness resin on the low-hardness plastic surface. They are typically used for pipes, plates, sheets, and films.
The hardness of Plastic Surface – This is the last method of increasing plastic hardness. Typically for regular plastic products. The hardness is only on the surface, while the inner side of the plastic has no changes.
Conclusion
In a nutshell, plastic hardness testing is crucial to ascertain the different types of plastic material quality. Furthermore, the type of material determines the method to avoid measurement errors and reading errors. The Rockwell hardness test, Shore hardness test, and Vickers hardness test remain your best options for plastic hardness testing. Finally, an increase in plastic hardness can be attained by blending, composite modification, and hardening the plastic surface.