Anti-aging Countermeasures For Polyethylene Shed Film
DATE：2019/9/27 8:57:24 / READ： / SOURCE：This station
Anti-aging countermeasures for polyethylene shed film
The main reason for shortening the service life of polyethylene film is the aging of polyethylene; the main cause of aging of polyethylene is thermal oxidation and photodegradation of polyethylene. In this way, countermeasures against the aging of the polyethylene film can be proposed.
1. Resist the thermal oxidation of polyethylene during molding and use
The addition of an antioxidant to the polymer prevents or retards the oxidation process of the polymer. It has a more prominent effect on polyolefins.
After the addition of the antioxidant, the oxygen absorption process of the polymer is slowed down, and as the concentration of the antioxidant increases, the induction period of the polymer before oxidation is lengthened, thereby delaying the oxidation process of the polymer.
Antioxidants include primary antioxidants, co-oxidants, metal purifiers, and the like. They can destroy the influence of impurities in the carbonyl, peroxy, hydroperoxide and catalyst on the polymer, prevent the degradation of free radicals, and improve the thermal stability of the polymer during molding and use.
(1) Primary antioxidant
Also known as free radical scavengers or chain cleavage terminators, mainly including hindered phenols, amine antioxidants. After they are added to the polymer, the peroxide radicals generated by the degradation process of the polymer can be eliminated and reduced to an alkoxy group or a hydroxyl group; the peroxide is decomposed, thereby terminating the self-oxidation chain reaction of the polymer; A hydrogen atom is used to deactivate the free radicals and no longer cause damage.
(2) Antioxidant
Also known as a hydroperoxide decomposer. It mainly includes phosphite and thioether antioxidants. They can decompose the hydroperoxide produced by the oxidation of the polymer and become an inactive product, thereby preventing the hydroperoxide from autocatalyzing during the degradation of the polymer, unable to continue to initiate new free radicals, and allowing the polymer to Oxidative degradation drops dramatically.
(3) Metal purification
Used to "binding" or complex metal ions, reducing the trace metal ions remaining in the resin to form free radicals, thereby limiting the chain growth of the free radical reaction. In actual use, the accelerated aging of the metal "backsheet" (the metal frame of the greenhouse) and the contact of the shed film can be reduced. It mainly includes anthracene derivatives, anthraquinones, cyclic acyl compounds and the like. However, metal purifications are now rarely used. Because the above antioxidants can also stabilize the catalytic action of the transition metal.
In the polymer stabilizing system, the primary antioxidant and the co-oxidant, or the antioxidant and the light stabilizer, are often used in combination to produce a good stabilizing effect.
The main reason for shortening the service life of polyethylene film is the aging of polyethylene; the main cause of aging of polyethylene is thermal oxidation and photodegradation of polyethylene. In this way, countermeasures against the aging of the polyethylene film can be proposed.
1. Resist the thermal oxidation of polyethylene during molding and use
The addition of an antioxidant to the polymer prevents or retards the oxidation process of the polymer. It has a more prominent effect on polyolefins.
After the addition of the antioxidant, the oxygen absorption process of the polymer is slowed down, and as the concentration of the antioxidant increases, the induction period of the polymer before oxidation is lengthened, thereby delaying the oxidation process of the polymer.
Antioxidants include primary antioxidants, co-oxidants, metal purifiers, and the like. They can destroy the influence of impurities in the carbonyl, peroxy, hydroperoxide and catalyst on the polymer, prevent the degradation of free radicals, and improve the thermal stability of the polymer during molding and use.
(1) Primary antioxidant
Also known as free radical scavengers or chain cleavage terminators, mainly including hindered phenols, amine antioxidants. After they are added to the polymer, the peroxide radicals generated by the degradation process of the polymer can be eliminated and reduced to an alkoxy group or a hydroxyl group; the peroxide is decomposed, thereby terminating the self-oxidation chain reaction of the polymer; A hydrogen atom is used to deactivate the free radicals and no longer cause damage.
(2) Antioxidant
Also known as a hydroperoxide decomposer. It mainly includes phosphite and thioether antioxidants. They can decompose the hydroperoxide produced by the oxidation of the polymer and become an inactive product, thereby preventing the hydroperoxide from autocatalyzing during the degradation of the polymer, unable to continue to initiate new free radicals, and allowing the polymer to Oxidative degradation drops dramatically.
(3) Metal purification
Used to "binding" or complex metal ions, reducing the trace metal ions remaining in the resin to form free radicals, thereby limiting the chain growth of the free radical reaction. In actual use, the accelerated aging of the metal "backsheet" (the metal frame of the greenhouse) and the contact of the shed film can be reduced. It mainly includes anthracene derivatives, anthraquinones, cyclic acyl compounds and the like. However, metal purifications are now rarely used. Because the above antioxidants can also stabilize the catalytic action of the transition metal.
In the polymer stabilizing system, the primary antioxidant and the co-oxidant, or the antioxidant and the light stabilizer, are often used in combination to produce a good stabilizing effect.
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