Hardness is defined as a material’s resistance to permanent indentation. It is one of the most measured parameters and often reported on technical data sheets of plastics.

Hardness of ductile materials is essentially a measure of their plastic properties. In the case of yield and tensile strength, a more or less linear correlation between hardness and mechanical strength is often observed.

The magnitude of the hardness value depends not only on the material itself, but also on the test conditions and the measurement method. It means  different hardness measurement methods, the same material measured hardness values are not the same. Therefore, to compare the hardness between the materials, it is necessary to measure the hardness with the same method of measurement.

The hardness of plastics  is often measured by the Rockwell or Shore hardness methods. Both methods provide an empirical hardness value, which do not necessarily correlate with other physical properties. The Rockwell hardness is usually chosen for "harder" materials such as steel, polycarbonate, polystyrene, polymethacrylates and acetal where the creep of the polymer has a lesser effect on the result, whereas the Shore durometer is often preferred for softer materials, such as soft polymers, elastomers, and rubbers.

So how do you change the hardness of the plastic?

1.Add hardness of modified plastics

The hardness of adding modified plastics refers to a modification method for adding hard additives in plastics. The common hardness filling agents are rigid inorganic fillers and fibers.

2.Surface treatment to improve the hardness of plastics

Plastic surface hardness improvement means only to improve the hardness of the appearance of plastic products. The hardness of the interior of the product is unchanged. This is a low cost method for improving hardness.

The modified method is mainly used for shells, decorative materials, optical materials and daily necessities, etc.. The modified method mainly includes two methods:coating and surface treatment.

3.Blending improved hardness of plastics

Plastic blending improvement method, that means in low the hardness resin, mixed with high hardness resin, to improve its overall hardness. The common blend resins are: PS, PMMA, ABS and MF, etc. the modified resins are mainly PE, PA, PTFE and PP.

4.Hardness of compound improved plastics

Plastic composite hardness improvement method, that means in the low hardness of plastic products on the surface of a layer of hardness resin. This method is mainly suitable for extrusion products such as plates, sheets, membranes and tubes. The commonly used composite resins are PS, PMMA, ABS and MF.

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