Polyester PU Soles

Polyurethane (PU) was used as sole material in 1970s.

The main advantage is that it is hard, flexible, durable and flexible in a large density range.

Therefore, PU has been widely applied in many fields. From outsole to bottom, it occupies 7% of the market share in the bottom market.

The former system used polyesters of dioxic acid. Although polyether PU is still used, most of (83%) sole material is PU of polyester (polyester PU is made of polyester and isocyanate, while polyether PU is polyether and isocyanate).

Because polyester PU has superior physical properties (harder, more wearable, etc.) because of its internal hydrogen bonding ability.

It can also prevent oil and solvent, so it is especially suitable for making protective shoes.

However, the key problem of ester PU shoe soles is that it is susceptible to hydrolysis and microbiological damage. As a result, physical properties are greatly reduced, the quality level shrinks and cracks occur (Figure 1), thus greatly reducing the service life of shoes.

These factors will be more serious in high temperature and high humidity conditions, so in a humid and hot geographical environment, the country is more significant.

At some point, shoes need to be stored (or pported by container ships, and conditions are very bad) for a long time before they reach the terminal consumers. After that, shoes become "new" shoes, and their quality is far from good.

Another problem with ester PU is the poor flexibility at low temperature, because the mild part of adipic acid is easy to crystallize.

So similar materials have great limitations at low temperature.

Because of its special chemical structure, the two polymer technology avoids these problems.

What is a two fatty acid? A combination of pressure, temperature and heterogeneous catalysis can extract two fatty acids from soybean oil or unsaturated fatty acids from Tarot oil.

Two fatty acids are bifunctional molecules that can easily form part of a polymer, such as polyamide and polyester.

Its structure is irregular, contains a large number of isomers, so it is completely amorphous.

It also contains 36 carbon atoms, and the properties of their hydrocarbons make it very difficult for the two polyacid and any polymer containing this substance to be wet by water.

The combination of hydrocarbon characteristics and non crystalline properties enables products to maintain good elasticity even at very low temperatures.

Two fatty acids are used to make PU products, such as artificial rubber, elastic foam, porous foam, paint, adhesive and sealant.

In these applications, the technology of two fatty acids is of high value. It has the following properties: unique combination of hydrolysis / thermal oxidation / UV protection, low temperature flexibility, adhesion, water resistance and impact resistance. In the footwear industry, the application of two polyacid technology is to cope with the serious instability of the ester sole system and its susceptibility to the attack of hydrolytic microorganisms.

If we do not use the esters in the traditional PU system, and use two polyester polyols, two polyfatty acids are not easy to touch the water, plus the closed chamber structure and its high molecular weight characteristics, the results are: better hydrolysis stability, anti microbial invasion characteristics, and longer soles.

Based on the technology of two fatty acids, Uniqema developed a special polyester polyol.

It is part of the Priplast technology range (Priplast is a polyester polyol made from two polycarboxylic acids of 36 carbon). It does not use additives to solve this problem.

Wet aging test (see figures 2 and 3), where water vapor reaches 70 degrees centigrade and 100% relative humidity, the test shows that although the performance has slightly decreased at the beginning, the new PU form exceeds the adipic acid industry standard after short term wet aging.

Compared with the standard, it also maintained good mechanical properties.

From this we think that the life of soles should be raised substantially, and it should probably not only increase two times.

The stability of natural vegetable oils using Priplast is different from traditional additives, because Priplast technology is actually changing the structure of materials, so it has more reliable performance.

In addition, because the product comes from natural vegetable oil, the technology is safe and inexpensive, while ordinary additives are not.

In addition, it comes from the characteristics of plants, which means that it will not be affected by increasing oil prices.

It is also found that this material has many other advantages for making sole materials.

It includes good elasticity, satisfactory compression deformation and elastic properties at low temperature, so it can be widely used in shoe industry.

The material has been applied in some non footwear industries, such as spray coating, adhesives and foam materials.

According to observation, protective footwear is a major market, and the products made with it have been evaluated in many PU systems, and the results are very good.