Answer: Usually oil added to rubber is aromatic oil containing benzene ring, which is toxic. Oil added in TPE is generally naphthenic oil or paraffin oil. Such softening oils are usually straight-chain hydrocarbon compounds and are generally non-toxic. As long as it is not put into mouth, it has no side effects just by contacting human body (skin).
Suggestion: Quality of oil used in TPE is good or bad, and inferior oil has a strong odor. It is recommended to choose a low-odor secondary hydrogenated oil.

Answer: Aluminum alloy and stainless steel metals cannot be directly encapsulated with TPE. This is different from TPE|TPR lagging plastics. However, with deepening of application of TPE, more and more products need to use TPE to encapsulate metal. How to encapsulate, there are two ways:

That is, TPE is directly injection-molded onto metal surface without any third medium. However, realization of this type of encapsulation has a great relationship with structure of location where metal parts need to be encapsulated and hardness of TPE.
Metal parts are encapsulated as a whole, or encapsulation structure of metal parts has a large curvature, or there are holes, etc., which will strengthen firmness of TPE-coated metal parts; in addition, the higher hardness of TPE material, the tighter and firmer bonding surface of TPE and metal will be.

In fact, more metal encapsulations are locally encapsulated. In order to ensure firmness of bonding, it is necessary to use an adhesive to achieve this.
Specific bonding process is: first, treat surface of metal parts to clean dust and oil on the surface; then select a suitable adhesive and apply it on the surface of metal parts; after adhesive on the surface of metal part dries, metal part is fixed in mold, TPE is injected onto the surface of metal part to complete bonding and encapsulation.
Analysis: If binder is still liquid, it will be injected into mold, and binder will be removed from surface of metal parts. Binder dries out, but it still needs to be sticky during high temperature molding, and adhesiveness of solvent volatile is not acceptable. It is necessary to evaluate and select a suitable binder. However, it is necessary to select corresponding adhesive according to characteristics of TPE material.

 

Answer: There are three main reasons for cracks in TPE products!

Material is oxidized by air and ozone, resulting in aging and cracking. Some sheet products with low hardness and thin size (especially SBS substrates),
After a few days of exposure to air, cracks appear on the surface!

Some toys that require oil injection, as well as some softer soles of children's shoes, sometimes have cracks in product during processing. Reason for crack is that amount of ink or glue used is too much, or it is accumulated on the surface, but surface of product is corroded and crack is caused. For this reason, according to different TPE|TPR materials, attention should be paid to the selection of adhesives, as well as amount of adhesives and uniformity of surface spraying.

TPE|TPR products are prone to stress concentration and notch effect due to structural design reasons, such as weld lines, uneven product thickness, and structures with obvious angle or radian changes, resulting in product cracks.

Answer: Internal cause is poor material compatibility. External reason is that gate position has a strong shearing effect. Peeling and delamination of gate is mainly caused by insufficient material compatibility and strong shearing effect.
Many TPEs based on SEBS system are alloy materials. If compatibility of system is not enough, in the case of special injection molding products (such as large flow length ratio, high firing rate), it is easy to be in gate position. Skin delamination occurs.
At gate position, because flow direction and rate of melt will change sharply, this shear-like effect is a great test for system uniformity of TPE melt. The greater firing rate and the greater flow-length ratio, the more obvious shearing effect. If compatibility of each component of TPE is not enough, it will easily lead to delamination and peeling of different phase structures and components.
Improvement: TPE compounding system should simplify component allocation ratio and improve compatibility of system. When molding, try to use high pressure and low firing rate. If possible, design a more reasonable position of glue inlet to reduce product flow length ratio.