Research on wear resistance of safety shoes

Safety shoes are a general term for safety shoes and protective shoes, which are used in the production and work to protect the feet and legs from the injury. According to the Labour department of Hong Kong, 36% of industrial safety accident is caused by stepping on objects, touching objects or objects falling on. As a result, the  foot is hurt, even disabled.

In the process of wearing shoes, the average pressure of the sole contacting with the feet on the ground is 0.4 ~ 0.7 Mpa, and the individual parts can be up to 1.5 Mpa, so the sole will be subjected to a considerable amount of friction. Abrasion is a damage phenomenon, caused by friction. For anti-static shoes, electric insulation shoes and acid and alkali resistant shoes, the sole wear-resisting performance is directly related to the product safety performance and service life. Therefore, it is mandatory to determin the the wear resistance of soles. The wear-resisting performance test is one of the most important routine test items in footwear production, and is also the main technical index to measure the quality of shoes.

The soles of the safety shoes are also called the base, which can be easily divided according to the material:  rubber material outer base and polymeric material outer base. The rubber material has natural rubber or synthetic rubber, and the polymer material has single density polyurethane and double density polyurethane.

The performance requirements of safety shoe sole mainly are good wear resistance, anti-chemical corrosion, heat resistance and oil resistance, but the sole has different performance due to different shoe sole material. With regard to the problems of rubber materials, such as heavy outer base weight, efflorescence and decomposition, the appearance of the safety shoes with the materials of polymer materials changed the situation, and the market share increased continuously. Polymeric material sole usually use polyurethane material for one-time injection molding. Polyurethane material can be used as the sole material for oil safety shoes, acid and alkali safety shoes, electric insulating safety shoes, etc. The sole of the polymer material is wear-resisting 2 ~ 3 times higher than that of ordinary rubber, and light weight (50% ~ 60% of rubber bottom) with good flex.

Safety shoes due to their special wear environment and various protection function requirements have longer service life than normal shoes whose soles are produced by straight stitching or moulding process. However, this kind of soles has the disadvantage of heavy wieght and poor comfortablity.The appearance of two - density polyurethane injection moulding soles further changed the situation.

Double density injection process refers to the process of pressing the molding on the sole, and the outer layer of glue is made of a solid layer by injection, and the inner layer of glue is the foaming layer, forming the double density sole. The outer layer of glue is a solid layer to ensure sufficient physical strength and good wear resistance, as well as good anti-skid and grease resistance. The inner layer of glue is the foaming layer to increase the cushioning performance of the rubber shoes, improve the elasticity, reduce the weight of the rubber shoes, and meet the required performance of labour shoes to the most extent. In addition, the dual-density injection process also has the characteristics of  rubber material saving and a high degree of automation.