1. Is the oil exuded from TPE harmful to the human body?
Answer: Usually the oil added to the rubber is aromatic oil containing benzene ring, which is toxic. The oil added in TPE is generally naphthenic oil or paraffin oil. This kind of softening oil is usually a straight-chain hydrocarbon compound, which is generally non-toxic. As long as it is not put into the mouth, it has no side effects if it comes into contact with the human body (skin).
Suggestion: The quality of the oil used in TPE is good or bad, and the inferior oil has a strong odor. It is recommended to choose a low-odor secondary hydrogenated oil.
2. Can TPE|TPR encapsulate metal?
Answer: Aluminum alloy and stainless steel metals cannot be directly encapsulated with TPE. This is different from TPE|TPR lagging plastics. However, with the deepening of the application of TPE, more and more products need to use TPE to encapsulate metal. How to encapsulate, there are two ways:
a. It is directly "encapsulated"
That is, TPE is directly injection-molded onto the metal surface without any third medium. However, the realization of this type of encapsulation has a great relationship with the structure of the metal parts to be encapsulated and the hardness of the TPE.
The metal parts are encapsulated as a whole, or the encapsulation structure of the metal parts has a large curvature, or there are holes, etc., which will strengthen the firmness of the TPE-coated metal parts; in addition, the higher the hardness of the TPE material, the combination of TPE and metal will be made. The face is firmer and firmer.
b. It is encapsulated with adhesive
In fact, more metal encapsulations are locally encapsulated. In order to ensure the firmness of the bonding, it is necessary to use an adhesive to achieve this.
The specific bonding process is: first, treat the surface of the metal parts to clean the dust and oil on the surface; then select a suitable adhesive and apply it on the surface of the metal parts; after the adhesive on the surface of the metal parts is dry, then Fix the metal part into the mold, and inject TPE onto the surface of the metal part to complete the bonding and encapsulation.
Analysis: If the binder is still liquid, put it in the mold for injection, and the binder will be cleaned from the surface of the metal parts. The binder dries out, but it still needs to be sticky during high temperature molding, and the adhesiveness of the solvent volatile is not acceptable. It is necessary to evaluate and select a suitable binder. However, it is necessary to select the corresponding adhesive according to the characteristics of the TPE material.
3. What is the reason for the cracking of TPE|TPR products?
Answer: There are three main reasons for the cracks in TPE products!
a. Fissure
The 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!
b. Solvent action cracks
Some toys that require oil injection, as well as some softer soles of children's shoes, sometimes have cracks in the product during processing. The reason for the crack is that the amount of ink or glue used is too much, or it is accumulated on the surface, but the surface of the product is corroded and the crack is caused. For this reason, according to the different TPE|TPR materials, attention should be paid to the selection of adhesives, as well as the amount of adhesives and the uniformity of surface spraying.
c. Stress cracking
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.
4. What happened to the peeling and delamination of the gate of TPE products?
Answer: The internal cause is poor material compatibility. The external reason is that the gate position has a strong shearing effect. The peeling and delamination of the gate is mainly caused by insufficient material compatibility and strong shearing effect.
Many TPEs based on SEBS system are alloy materials. If the compatibility of the system is not enough, when encountering special cases of injection molding products (such as large flow-length ratio and high firing rate), it is easy to be in the gate position. Skin delamination occurs.
At the gate position, because the flow direction and rate of the melt will change sharply, this shear-like effect is a great test for the system uniformity of the TPE melt. The greater the firing rate and the greater the flow length ratio, the more obvious the shearing effect. If the compatibility of each component of TPE is not enough, it will easily lead to delamination and peeling of different phase structures and components.
Improvement: The TPE compounding system should simplify the component distribution ratio and improve the compatibility of the system. When molding, try to use high pressure and low firing rate. If possible, design a more reasonable position of the glue inlet to reduce the product flow length ratio.
