In recent years the footwear industry has been growing at a constant pace thanks to the high demand for an aesthetic product, in accordance with fashion, and, even so, highly comfortable and durable. The footwear industry can be classified by the type of user, purpose of the footwear, and among other parameters, the material with which it is manufactured.

In this article we will focus on the footwear material known as phylon, a modification of EVA rubber, which by means of a thermoforming and cooling process achieves a less dense material, and, therefore, lighter.

Before going into more detail about phylon, we will focus on EVA rubber to learn about the origin of this new material that is expanding.

EVA rubber is a copolymer formed by the repetition of ethylene and vinyl acetate monomers. The proportion used of these two components will determine the properties and qualities of the material. Generally between 10% and 40% vinyl acetate is used, and the rest is ethylene. The higher the percentage of vinyl acetate, the higher the quality of EVA rubber, since with a small percentage a hard and brittle polymer would be obtained. EVA is a soft plastic that, thanks to its foaming process, is perfect for use as a shoe sole.

The foaming of EVA is done by introducing gas into the polymer. A foaming agent, azodicarboamide being the most common, is introduced into EVA mixture. This, when the mixture is heated, decomposes producing gas that is trapped in the plastic. The gas expands and EVA foam forms.

Once EVA foam is formed, shoe soles or other parts of the shoe can be formed through different methods. One of them, the hot compression process of EVA foam, results in phylon.

Phylon is the most common process for creating soles for sports shoes. This process starts with EVA already expanded, that is, with EVA foam, which contains gas bubbles inside. This foam is introduced into a mold with the design and final shape that the sole will have. The mold closes and it is heated, melting EVA inside allowing the trapped gas to expand further, making it easier for EVA to fill the mold. The mold is cooled and the EVA part is extracted.

The extraction of the phylon part is carried out thanks to the presence of a release agent. This agent is applied by spray gun or brush, providing the necessary lubrication to be able to extract the part without causing superficial damage. In addition, these products are responsible for the appearance and surface feel of the demolded part.

Concentrol’s demolding department has developed a concentrated product to dilute in water for this process. The product CONCENTROL LP IADC-114-43 PHB can be diluted up to 1:100, depending on the working conditions, maintaining a high demolding efficiency and its stability at temperatures over 200ºC.

CONCENTROL LP IADC-114-43 PHB gives parts a glossy finish (figure 1), but with the addition of a Concentrol matting agent, it is possible to achieve a satin or even matte shade (figure 2).


Figure 1: CONCENTROL LP IADC-114-43 PHB            Figure 2: CONCENTROL LP IADC-114-43 PHB

(original)                                                           (Concentrol matting agent)