Main materials for soles manufacturing

1. TR - Thermoplastic rubber

Non-slip material, quite flexible and easily deformable by heat. It tears with the attack of solvents such as acetone and ethyl acetate. The TR (thermoplastic rubber) compounds have as a base a copolymer formed by styrene and butadiene blocks (SBS) that gives the characteristics of vulcanized rubber with the ease of thermoplastic transformation. They are easy materials to process, as well as PVC, and they behave like a SBR vulcanized at room temperature.

They can be subdivided into conventional, gummed and super-gummed.

IDENTIFICATION: when burned, its flame is yellow and emanates a sweet smell of rubber.

2. PU – Polyurethanes

Material similar to PVC, non-slip and opaque. It can offer a wide variety of densities and hardnesses that vary according to its formulation and property modifiers.

IDENTIFICATION: softens and breaks under the tetrahydrofuran action, an organic compound, with an ether-like odor.

3. PVC - Polyvinyl Chloride

Polyvinyl Acetate is a material that glides and has shine. Depending on its formulation and additives it can be rigid or flexible, providing resistance to most chemical reagents. It has good thermal, electrical and acoustic insulation, as well as high durability and resistance.

IDENTIFICATION: softens and breaks under the action of tetrahydrofuran.

4. EXPANDED EVA - Ethylene vinyl acetate

Lightweight material, with a flexible sponge appearance and with low abrasion resistance. Accepts pigmentation of various colors.

IDENTIFICATION: when exposed to the flame, it releases a smell similar to the burned paraffin (candle). Continues burning even when removed from the flame.

5. EVA INJECTED - Ethylene vinyl acetate

Lightweight material that accepts pigmentation of various colors. It is similar to TR, but does not have rubber characteristics.

IDENTIFICATION: The flame of this material emanates acidic smell similar to vinegar.

6. TPU - Thermoplastic Polyurethane

Material of the family of expanded polyurethanes, has different and specific characteristics, providing greater performance to footwear. It confers high tear resistance and flexural fatigue. It reproduces the mold with perfection, it has excellent finish and good resistance to oils and fuels. It is resistant to hydrolysis, easy to process and has good adhesion properties.

IDENTIFICATION: when it burns it shows yellow flame and when it melts it drips.

The proper application of the soles in the footwear responds to previous compatibility tests between the different intervening materials.

7. SBR - Vulcanized rubber

It can be compact (Neolite) or expanded (Porolite), synthetic crepe, lacquered or velvety. Does not suffer the attack of solvents. It has very good resistance to abrasion, but low resistance to thermal aging, as well as the environment and chemical products.

IDENTIFICATION: if we expose the SBR to a flame, after removal it is still burning. The flame is yellow with soot and smells like burnt rubber.

8. ABS - Acrylonitrile Butadiene Styrene

Rigid material, usually cream colored, that suffers the attack of solvents. It has excellent properties of impact resistance, thermal and chemical stability, as well as good processing. It is used in the manufacture of heels.

9. ACRYLIC

Rigid and transparent material that has better solvent resistance than polypropylene.

12. NYLON - Polyamide

Hard, shiny and hard to burn material. It has high performance and minimal humidity absorption. It resists high temperatures and offers superior chemical resistance and toughness.

IDENTIFICATION: in spite of the difficulty to burn it, when it is ignited, it smells like wool or burned hair.

Source: Technical Manual of ASSINTECAL -Brazilian Association of Companies of Components for Leather, Footwear and Manufactures-, elaborated with associated companies and the support of APEX -Exports Promotion Agency-.