In order to prevent photoaging of polymers, substances that can inhibit or reduce photodegradation and improve the light resistance of materials are often added to polymers, and these materials are collectively referred to as light stabilizers. The amount of light stabilizer is very small, generally 0.01% to 0.5%. The ideal light stabilizer should have the following conditions: It has good compatibility with the polymer, does not volatilize, does not migrate, is not extracted by solvents and water, and can strongly absorb ultraviolet rays in the wavelength range of 290 to 400 nm or can effectively çŒElimination of the excited molecule's energy or ability to trap free radicals; low absorption of visible light, no contamination of products, good self-stability, no damage by light energy; good thermal and chemical stability, stable processing, not Chemical reactions with other auxiliaries; inexpensive, non-toxic.
Light stabilizers can be divided into four major categories according to their mechanism of action: light shielding agents, ultraviolet absorbers, quenchers, and free radical trapping agents. The following will be introduced separately.
1. Light shielding agents Light shielding agents are substances that reflect and absorb ultraviolet light. After adding a light shielding agent to the polymer material, the product can be shielded from ultraviolet rays and the transmission effect of ultraviolet rays can be reduced. Most light shielding agents are composed of inorganic pigments and fillers such as carbon black, zinc oxide, ultramarine blue, titanium dioxide, and the like. Carbon black is the light shielding material with the highest shielding effectiveness, and the best particle size is 15~25 nm, and the channel black is better than the furnace black. The amount of carbon black is preferably within 2 parts, and the amount is too large, the shielding effect is not increased obviously, on the contrary, the cold resistance and electrical insulation performance are lowered. As an inexpensive, durable, non-toxic light stabilizer, zinc oxide has been widely used in high-density polyethylene, low-density polyethylene, polypropylene and other polymer materials in recent years. The best shielding effect of zinc oxide is 0.11 nm, and the test proves that the shielding effect of 3 parts of zinc oxide is equivalent to that of 0.3 parts of organic light stabilizer.
2, UV absorbers UV absorbers are the most commonly used light stabilizers, they can selectively and strongly absorb high-energy ultraviolet light, and then carry out energy conversion, and ultimately release energy in the form of heat energy or harmless low-energy radiation. Consumption. Currently widely used ultraviolet absorbers are benzophenones and benzotriazoles. Benzophenone light stabilizers are currently the largest and most widely used UV absorbers. These compounds absorb UV light from 290 to 400 nm and have good compatibility with most polymers. Benzotriazole ultraviolet absorbers are characterized by stability and high efficiency. Since it can effectively absorb ultraviolet rays of 300 to 400 nm, it hardly absorbs visible light of 400 nm or more, so that there is no coloring disease.
3. Quenchers Quenchers are also known as quenchers or deactivators. When the polymer is in an unstable “excited state†due to the absorption of ultraviolet light, the quencher can activate the energy from the excited polymer molecules. Eliminate it, return it to the ground state, so as to avoid further decomposition to produce active free radicals. The quencher is mainly an organic complex of nickel, and its UV absorption ability is small, and it is only 5% to 10% of benzophenones. Quenching agents are often used together with benzophenones, benzotriazoles, and other ultraviolet absorbers, and have a good synergistic effect.
4, radical scavenger Free radical scavenger light stabilizers from the chemical structure point of view, there is a steric hindrance effect piperidine derivatives, referred to as hindered amine stabilizer. It is generally believed that the mechanism of action of the free radical scavenger is mainly the capture of free radicals. This function can be simply understood as that when the polymer absorbs ultraviolet light and decomposes to produce an active free radical that leads to an autoxidation reaction, the scavenger captures the active free radical, so that It becomes a stable compound, preventing the oxidation reaction from proceeding. These stabilizers are mainly used for polyolefins, polystyrenes, and polyurethanes, and their stabilizing effect is several times higher than UV absorbers. · The old shoes at home are like this to transform big spikes · Old shoes don't stupidly throw away so that the shoes "open" Put a physical insurance on your shoes · How to clean the matte surface of the shoes? · Breathable, antibacterial, deodorizing socks with it to avoid off shoes ·Sports shoes's little tail actually has these 3 functions you certainly don't ·High-heeled shoes audio sound? 4 coups to ease you learn a few ·How to choose shoes during pregnancy? Flat shoes are not safe What should I do if my shoes become moldy ·Wearing these shoes in the summer will hurt you
Light stabilizers can be divided into four major categories according to their mechanism of action: light shielding agents, ultraviolet absorbers, quenchers, and free radical trapping agents. The following will be introduced separately.
1. Light shielding agents Light shielding agents are substances that reflect and absorb ultraviolet light. After adding a light shielding agent to the polymer material, the product can be shielded from ultraviolet rays and the transmission effect of ultraviolet rays can be reduced. Most light shielding agents are composed of inorganic pigments and fillers such as carbon black, zinc oxide, ultramarine blue, titanium dioxide, and the like. Carbon black is the light shielding material with the highest shielding effectiveness, and the best particle size is 15~25 nm, and the channel black is better than the furnace black. The amount of carbon black is preferably within 2 parts, and the amount is too large, the shielding effect is not increased obviously, on the contrary, the cold resistance and electrical insulation performance are lowered. As an inexpensive, durable, non-toxic light stabilizer, zinc oxide has been widely used in high-density polyethylene, low-density polyethylene, polypropylene and other polymer materials in recent years. The best shielding effect of zinc oxide is 0.11 nm, and the test proves that the shielding effect of 3 parts of zinc oxide is equivalent to that of 0.3 parts of organic light stabilizer.
2, UV absorbers UV absorbers are the most commonly used light stabilizers, they can selectively and strongly absorb high-energy ultraviolet light, and then carry out energy conversion, and ultimately release energy in the form of heat energy or harmless low-energy radiation. Consumption. Currently widely used ultraviolet absorbers are benzophenones and benzotriazoles. Benzophenone light stabilizers are currently the largest and most widely used UV absorbers. These compounds absorb UV light from 290 to 400 nm and have good compatibility with most polymers. Benzotriazole ultraviolet absorbers are characterized by stability and high efficiency. Since it can effectively absorb ultraviolet rays of 300 to 400 nm, it hardly absorbs visible light of 400 nm or more, so that there is no coloring disease.
3. Quenchers Quenchers are also known as quenchers or deactivators. When the polymer is in an unstable “excited state†due to the absorption of ultraviolet light, the quencher can activate the energy from the excited polymer molecules. Eliminate it, return it to the ground state, so as to avoid further decomposition to produce active free radicals. The quencher is mainly an organic complex of nickel, and its UV absorption ability is small, and it is only 5% to 10% of benzophenones. Quenching agents are often used together with benzophenones, benzotriazoles, and other ultraviolet absorbers, and have a good synergistic effect.
4, radical scavenger Free radical scavenger light stabilizers from the chemical structure point of view, there is a steric hindrance effect piperidine derivatives, referred to as hindered amine stabilizer. It is generally believed that the mechanism of action of the free radical scavenger is mainly the capture of free radicals. This function can be simply understood as that when the polymer absorbs ultraviolet light and decomposes to produce an active free radical that leads to an autoxidation reaction, the scavenger captures the active free radical, so that It becomes a stable compound, preventing the oxidation reaction from proceeding. These stabilizers are mainly used for polyolefins, polystyrenes, and polyurethanes, and their stabilizing effect is several times higher than UV absorbers.
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