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about Plastic product hardness

Dec 24, 2018

The hardness of a plastic generally refers to the ability of a plastic material to resist the pressing force of a rigid material, and its numerical value can be considered as a quantitative reflection of the degree of softness and hardness of the plastic. Although plastic hardness does not have an inherent correspondence with other mechanical properties like the hardness of metal materials, hardness is an important indicator of material quality control and product inspection!


E.g:

1. Elastomer plastic raw materials, the hardness of the material directly affects the hand feel of the finished product, the effect of the rubber coating, and through the hardness can indirectly understand the other mechanical properties of the material, such as abrasion performance, tensile properties, curing degree.


2. The strength of plastic parts for automobiles has corresponding requirements. At the same time, many parts must be added with auxiliary materials, which will affect their performance. Therefore, hardness testing is required.


After obtaining the hardness value of the plastic product through testing, how to change the hardness of the product to improve the quality of the product?


1. Mixing can increase the hardness of plastics


An improved plastic mixing method is to mix a high hardness resin in a low hardness resin to increase its overall hardness. Commonly used mixed resins are: PS, PMMA, ABS and MF. The resins to be modified are mainly PE, PA, PTFE and PP.


2. Composite materials improve plastic hardness


A method of increasing the hardness of a plastic composite is to bond a high hardness resin to the surface of a low hardness plastic article. The method is mainly applicable to extruded products such as sheets, sheets, films and pipes. Commonly used composite resins are PS, PMMA, ABS and MF.


3. Increased hardness of plastic surface


This method only involves increasing the hardness of the outer surface of the plastic article, and the hardness inside the product is unchanged. This is a low cost hardness improvement method. The modification method is mainly used for outer casings, decorative materials, optical materials and daily necessities. The modification method mainly includes three methods of coating, plating and surface treatment.


Learn to understand the key points related to the hardness of the above plastic products, then how is the hardness detected?


The common method for detecting hardness can be divided into Shore hardness and Rockwell hardness according to the shape of the detection head. Since the Shore hardness test is the most widely used in the rubber and plastics industries, today we focus on Shore hardness.


Shore hardness is a method of indicating the hardness level of a material, first proposed by the British Albert F. Shore. Commonly used models are Shaw A, C, and D. The general purpose of each model is as follows:


Shaw A type: suitable for testing medium and low hardness plastics, leather, all kinds of rubber, multi-fat, wax and so on.

Shore C: Suitable for testing foam, sponge, microporous materials for shoes, etc.

Shore D: Suitable for testing hard rubber, hard resin, glass, thermoplastic, printing plates, fibers, etc.

When determining the Shore hardness,   the ISO standard, using  Type A and Type D.


      Hardness chart

image

It can be seen from the Shore hardness comparison table that the hardness of the material having a Shore hardness of 90 A or less is measured by the hardness A, and the material of the material higher than 90 A is measured by the D meter. In the early stage of the actual test, the appropriate hardness tester model should be selected according to the hardness of the sample.


welcome to choose our shore hardness tester:

https://www.chinatestequipments.com/tests-on-plastic-raw-materials/hardness-tester/digital-display-shore-hardness-tester.html