What are the factors that lead to poor toughness of TPE raw material products
Source：德創化工Time：2020-02-22Hits：3705
TPE(Thermoplastic Elastomer) is usually taken as the abbreviation of all thermoplastic elastomers, which is in a broad sense, such as TPU, TPE, TPV, TPO, etc., all belong to TPE.
In a narrow sense, TPE is a styrenic thermoplastic elastomer, which is a blend modified material based on SEBS (Styrene-Ethene-Butylene-Styrene Block Copolymer-Hydrogenated Styrene-Butadiene-Styrene Block Copolymer).
It has the thermoplasticity of plastic and the elasticity of rubber. Its appearance is natural color, translucent or transparent round or cylindrical particles. Its surface is sub-surface effect. Its density is generally 0.9-1.1g/cm.
I. Main Factors Affecting Strength Difference of TPE Products
1. Problems of TPE Material Blending System
The type of rubber substrate, the proportion of plastic and the content of oil will all affect the tear strength of the compound material.
2. TPE material degrades or its performance degrades for many times
The higher the molding temperature, the more the processing times, and many physical properties of materials including tear strength will deteriorate.
3. Stress Defect
The products have sharp inner edges or edges, and there are stress gaps, which easily lead to stress concentration. When an external force is encountered to stretch the tear, the tear of the product usually starts from these positions.
II. Methods for Improving Strength of TPE Products
For the material blending system, it is suggested as follows:
A, selecting SEBS base material with high molecular weight and star structure;
B, under the condition that the material property requirements permit, the proportion of plastic components (such as PP, PS, LLDPE) should be appropriately increased;
C, on the premise of ensuring physical properties, properly reduce the amount of oil added;
D, appropriately reducing the addition amount of inorganic filling powder such as calcium carbonate;
Understand the molding characteristics of materials and adopt moderate processing temperature; When using secondary materials, pay attention to control the addition ratio (generally, the addition amount of secondary materials shall not exceed 25%); When designing products and moulds, sharp or abrupt corners shall be avoided as far as possible, and corners shall be designed in arc shape as far as possible to reduce stress defects.
Of course, if SBS alloy elastomers cannot meet the tear strength requirements of materials, TPE of other molecular chains or substrates, such as TPV and TPEE, can be considered.
