Anti-aging modification of polypropylene

PP is a resin that is easy to age. Since many products are used outdoors, there is a great demand for anti-aging modification of PP. Polypropylene has good stability under oxygen-free conditions, but due to the existence of tertiary carbon atoms in the polypropylene structure, it is easily degraded by heat, oxygen and light during granulation, storage and use, and even loses its capacity. Excellent comprehensive physical and mechanical properties and use value, which is why the oxidation resistance and aging resistance of polypropylene are worse than polyethylene. In order to inhibit and delay the oxidative degradation of polypropylene and keep the molecular weight of polypropylene unchanged, it is usually necessary to carry out stabilization treatment after the polymerization reaction, before separation, drying and storage. Adding antioxidants in the granulation stage is to improve polypropylene An easy and effective route to antioxidants.

The oxidation aging process of polypropylene proceeds according to the mechanism of free radical chain reaction. Under the action of heat and oxygen, the macromolecular chain of polypropylene is broken, and free radicals are generated. These free radicals further cause the cracking, branching and cross-linking of the entire macromolecular chain, and finally lead to the aging and deterioration of polypropylene. The auto-oxidation of polypropylene includes three processes: chain initiation, chain transfer, and chain termination. During the oxidation process, when the macromolecular chain is broken and degraded, the molecular weight decreases, the melt viscosity decreases, the strength of polypropylene decreases and pulverization occurs. When the macromolecules undergo a cross-linking reaction, the molecular weight increases, the melt fluidity decreases, and embrittlement and hardening occur. Oxidized structures generated during the oxidation process, such as peroxides, reduce the electrical properties of polypropylene and increase the susceptibility to light-induced degradation. Further reactions of this oxidized structure cause macromolecules to break or cross-link.

Glass filled PP
Glass filled PA
Flame retardant HIPS

Flame retardant PC/ABS

Flame retardant PC

The role of antioxidants is to prevent the progress of the automatic oxidation chain reaction of polypropylene, that is, to supply hydrogen to make the free radicals R• and ROO• generated during the oxidation process into RH and ROOH, or to make ROOH into ROH, so as to improve the polymerization. The ability of propylene to resist oxidation and pyrolysis during processing and application.

In order to achieve protection of the polymer from oxidation or to delay the effect of oxidation, the polymer auto-oxidative cycle must be disrupted. A feasible method is to use some special compounds to interfere with the intermediate products participating in the cycle, so that the cycle cannot proceed or the reaction rate is slowed down. There are two types of harmful intermediates in the oxidation cycle, one is free radicals (P•, POO•, PO•, HO•), and the other is hydroperoxide (POOH). Correspondingly, compounds that interact with the two types of intermediates are also divided into two categories: free radical traps (also known as chain-terminating primary antioxidants), and hydroperoxide decomposers (also known as secondary antioxidants). agent). The function of the primary antioxidant is to trap free radicals so that they are no longer involved in the oxidative cycle. The role of secondary antioxidants is to break down hydroperoxides into harmless products


Secondary antioxidants are also known as preventive antioxidants because they break down hydroperoxides without generating free radicals, thus preventing chain branching. It is sometimes necessary to distinguish between equivalent or catalytic hydroperoxide decomposers. Phosphites are the most typical representatives of equivalent hydroperoxide decomposers, which reduce hydroperoxides to the corresponding alcohols and themselves into phosphates

Organosulfur compounds are the second important class of auxiliary antioxidants. They are equivalent hydroperoxide decomposers that convert two molecules of hydroperoxide into alcohols. Sulfur-containing organic acids are hydroperoxide decomposers, and in addition, sulfur dioxide and sulfur trioxide formed at the end of the oxidation reaction are particularly effective hydroperoxide decomposers. Considering the reaction of organic sulfides and sulfides, it is clear that the real effective substances are not these substances themselves, but their oxides


Our categories of modified PP
1) Special material for air conditioner outdoor casing - weather-resistant polypropylene

The outdoor casing of the air conditioner is generally made of galvanized steel plate coated with anti-corrosion paint, which is heavy in quality, complicated in forming and processing, and difficult to master the spraying process. Once the anti-corrosion paint falls off, it will cause large-scale corrosion. Therefore, a large number of weather-resistant PP have been used as outdoor casings in foreign countries recently. my country has also developed the materials for the outdoor casing of air conditioners, and the materials we have developed have been applied to air conditioners such as Haier. The aging life of this product is more than 15 years, which can meet the material requirements of air conditioners.

2) Washing machine drum - glass fiber reinforced polypropylene high-strength and high-toughness PP special material, which has the characteristics of high impact toughness and good fluidity. It is composed of glass fiber and polypropylene resin. It has high strength and high modulus, and can be made Large, harsh use environment and high performance requirements. Since the material uses polypropylene resin as the matrix, it has high cost performance and good processing performance.

3) Special material for refrigerator drawers - filled and toughened polypropylene refrigerator drawers are generally made of HIPS. On the one hand, HIPS is prone to stress cracking under the action of acid, alkali, salt, grease, etc., which affects the service life; on the other hand, the price of HIPS is higher than that of PP , so the development of modified PP instead of HIPS for refrigerator drawers has attracted the interest of material workers, especially in Japan, modified PP has been successfully used in refrigerator drawers


4) Special material for rice cookers and electric cups - high gloss polypropylene, through mineral filling and modification of the matrix PP, changes the crystallization behavior of PP in the injection molding process, effectively improving the surface gloss and hardness of PP, and its surface gloss can be At or close to the effect of high gloss plastics such as PS and ABS, the heat distortion temperature is several tens of degrees higher than that of ABS, and the fluidity is good and the processability is excellent. Because its price is cheaper than high-gloss ABS, it can replace ABS to prepare parts with high decorative appearance, such as rice cooker shells, electric cup shells, water dispenser shells, refrigerators, washing machine panels, etc.


5) Special material for automobile bumper - high-rigidity and super-tough polypropylene