Application of thermoplastic elastomer in automobile industry

At present, thermoplastic elastomers commonly used in automobiles are mainly divided into four categories: polyolefins (TPO and TPV), polyester (TPEE), polyurethane (TPU) and styrene (TPS).

TPO is the most active TPE used in automobile manufacturing at present, mainly used in automobile bumpers and interior surface materials, in addition, it is used in door and window sealing strips, mudguard, steering gear box sheath, fuel pipes, etc;

TPV material has obvious superior performance, high price, and wide range of promotion and application of the limit value. Its main advantage is to improve the coordination of the external parts of the car. It is mainly used in the safety buckles of advanced passenger cars, waterproof sealing strips of car doors and windows, and sealing strips of car glass guide grooves. In addition, it is also used in the angle type anti-shock, air baffles, and various air supply and water delivery hoses, oil seals, gaskets, etc;

TPEE is mainly used in constant velocity universal joint sheath to meet the requirements of weather resistance, oil resistance and heat resistance. In addition, the steering rack shield, suspension shield and transmission control dust cover manufactured by TPEE blow molding; Connecting shaft sleeve, hand brake pulley, dust seal ring, etc. manufactured by injection molding; The wire harness and cable sheath manufactured by extrusion are widely used in the field of automobile manufacturing;

TPU has excellent wear resistance and bending fatigue resistance, and is widely used in auto parts, such as connecting shaft sleeve, shift lever handle, sealing ring and gasket;

TPS is mainly used on automobile rubber pipes, gaskets and adhesives.

Action mechanism of weather resistant additives for TPE

The photoaging degradation of TPE materials follows the material aging mechanism. TPE materials absorb the energy in the sun to reach the excited state and produce free radicals. The free radicals react with the oxygen in the air to produce peroxides. The peroxides cause the further degradation of the polymer to form peroxides. The free radical chain segments continue to grow, resulting in the reduction of the mechanical properties of the materials, loss of surface gloss, and loss of use value.

How the weather resistant additives play a role in the aging process of TPE materials is further explained by the following reaction mechanism diagram.

The TPE material is irradiated by the ultraviolet light in the sun. Before reaching the excited state, the ultraviolet absorber (UVAbsorber) absorbs the energy of the sun, consumes the heat energy through the transformation of the chemical structure, and prevents the TPE material from reaching the excited state. The absorber needs a certain optical path, so it plays a good role in protecting the interior of the product. When the TPE material produces free radicals under the action of light and heat, the hindered amine light stabilizer (HALS) does not absorb ultraviolet rays, but stops the photoaging process by capturing the free radicals generated by the substrate and preventing it from continuing to produce free radicals. The action mechanism of these two types of light stabilizers is detailed as follows:

UV absorber

A class of organic compounds that can selectively and effectively absorb harmful ultraviolet rays from polymers and have high light fastness, including hydroxybenzophenone, hydroxybenzotriazole, hydroxyphenyltriazine, salicylate, benzoate, cinnamate, oxalanilide. The main absorption mechanism is as follows:

Action mechanism of benzophenone ultraviolet absorbers

Mechanism of benzotriazole ultraviolet absorbers

Action mechanism of triazine ultraviolet absorbers

The difference of absorption spectra of several main UV absorbers is as follows:

Different types of ultraviolet absorbers have limited absorption bands. Acrylates and herbal amides have strong absorption in the short wave band (≤ 350nm). benzophenone absorbers have wide absorption peaks. benzotriazole ultraviolet absorbers have the broadest absorption peaks. Their absorption efficiency is better than that of benzophenone absorbers. Triazines have the strongest ultraviolet absorption peaks and the highest absorption efficiency. In order to achieve the full band absorption required by customers, different kinds of absorbents can be used to cover the full band ultraviolet absorption.

Hindered amine light stabilizer

Action mechanism of hindered amine light stabilizer (HALS): HALS does not directly capture free radicals, but tetramethylpiperidine oxide to capture free radicals. The HALS product with N-alkoxy structure is relatively active and can continue to capture free radicals and transform them into more stable R-R, R-O-R, R-OO-R and other compounds, stopping the process of photoaging, and its efficiency is 2-4 times higher than that of UV absorbers.

HALS light stabilizer is converted into tetramethylpiperidine oxide in the presence of oxygen.

HALS light stabilizer has a good light stability protection on the surface of TPE material. Therefore, the combination of HALS and ultraviolet absorber can achieve a real synergistic effect and give TPE good light stability to the maximum.

Xinxiu Chemical provides a comprehensive weather-resistant solution

Xinxiu Chemical has developed a series of weather-resistant solutions for different TPE materials, such as the combination of benzophenone type absorbent Plastozene 531 and HALS type Plastozene 622, which can achieve good results in polyolefin elastomer (TPO) film products; For example, it can be used to increase the demand of CPVC, TPO and other elastomers in terms of ultra-long term weather resistance by adding the combination of Plasticin 5586 (salicylic acid UVA) and 5583 (hindered amine HALS); For example, the addition of Plasticine 5566 integrates a variety of weather resistance mechanisms and has a good weather resistance effect for polyurethane elastomer (TPU). For example, the ultraviolet absorber Plastozen 5519 and the HALS-type Plastozen 5589 are used together to provide excellent long-term weather resistance for the vehicle TPV sealing guide groove and meet the requirements of its mechanical properties; For example, the synergetic effect of the ultraviolet absorber Plasticin 5523, Plasticin 5544 and Plasticin 622 of HALS provides excellent weather resistance requirements for the flame-retardant polystyrene elastomer TPS.