Reasons for poor strength of TPE elastomer products

- Aug 07, 2018 -

In the TPE elastomer industry, TPE (Thermoplastic Elastomer) is used as an abbreviation for all thermoplastic elastomers. This is in a broad sense, such as TPU, TPEE, TPV, TPO, etc. are all TPE.

In a narrow sense, TPE is a styrenic thermoplastic elastomer. It is a material obtained by blending and modifying SEBS (Styrene-Ethylene-Butylene-Styrene Block Copolymer-hydrogenated styrene-butadiene-styrene block copolymer) as a substrate. It has the thermoplasticity of plastic and the elasticity of rubber. The TPE looks like a natural, translucent or transparent round or cylindrical particle with a sub-surface effect. The density is generally between 0.9 and 1.1 g/m3.

 TPE elastomer material has poor tear strength, and there are mainly the following possible factors:

1. Problems with TPE material compounding system

(1) Reason analysis:

The type of rubber substrate, the proportion of plastic, the content of oil, etc., all affect the tear strength of the compounded material.

(2) Improvement method

A. Select a SEBS substrate with a high molecular weight and star structure;

B. Appropriately increase the proportion of plastic components (such as PP, PS, LLDPE) if the physical properties of the materials permit;

C. Under the premise of ensuring physical properties, appropriately reduce the amount of oil added;

D. appropriately reducing the amount of inorganic filler powder such as calcium carbonate;

2. TPE material degradation or multiple use performance degradation

(1) Cause analysis

The higher the molding processing temperature, the more the number of processing, and the physical properties of materials including tear strength are deteriorated.

(2) Improvement method

Understand the molding characteristics of the material, use moderate processing temperature; pay attention to control the addition ratio when using the secondary material (generally the maximum amount of secondary material does not exceed 25%)

3. Stress defects

(1) Cause analysis

The product has sharp inner edges or corners, and there is a stress gap, which tends to cause stress concentration. In the event of an external force tensile tear, the tearing of the product begins at these locations.

(2) Improvement method

Try to avoid sharp or abrupt corners when designing products and molds. Design corners as far as possible to reduce stress defects.

Of course, if the SBS-based alloy elastomer can not meet the material tear strength requirements, other molecular chains or substrates of TPE, such as TPV, TPEE, etc., may be considered.