Wuhan modern heat stabilizer
DATE：2020/12/17 9:22:26 / READ： / SOURCE：This station
Wuhan modern heat stabilizer
1. Definition and requirements
Plastics are degraded due to heat, friction, shear and other physical effects in the molding process, and external conditions such as heat, light and oxygen in the process of use, so that the performance of the products will deteriorate or even lose the use value. In order to inhibit this effect, heating stabilizer should be added. The dehydrochlorination reaction occurs when PVC is heated above 100 ° C. the degradation reaction is accelerated at the molding temperature (above 170 ° C). In addition to dehydrochlorination, the PVC also changes color and crosslinks, which makes the performance worse. Therefore, heat stabilizers must be added to PVC to inhibit the above effects, which can capture hydrogen chloride.
Heat stabilizers are mainly used for PVC, but due to the structural defects of PE, PP and pur, heat stabilizers are sometimes added. The main factors affecting the thermal degradation of PVC are chain structure (branch chain, double bond, allyl chloride, head structure, conjugated double bond and molecular weight, etc.). Of course, oxygen, hydrogen chloride, additives and other external factors also have an impact. Therefore, the heat stabilizer should have the following functions: ① it can absorb or neutralize the hydrogen chloride released in the process of processing and use, and terminate its autocatalytic effect; ② replace the active and unstable chlorine atoms in the molecule to inhibit the dehydrochlorination reaction; ③ carry out double bond addition reaction with the polyene structure to eliminate or slow down the discoloration of the product; ④ prevent the oxidation of the polyene structure; ⑤ prevent the oxidation of the polyene structure And impurities in passivation resin, catalyst residues, end groups, etc.
2. Selection and evaluation of heat stabilizer www.handern.com Plastic sheet extrusion equipment
When choosing a kind of heat stabilizer, it is necessary to evaluate its various properties first, and then analyze and compare on this basis, so as to select a more satisfactory material. Due to many factors affecting the thermal stability, the effects of various stabilizers are quite different, so it is often necessary to use several kinds of stabilizers to achieve satisfactory results. The additives are different from other additives in terms of heat resistance, heat resistance, heat resistance and other properties.
(1) Generally, static and dynamic thermal stability tests are used to judge the heat resistance of heat stabilizers; color and strength tests are carried out in the thermal aging chamber to evaluate whether the heat stabilizers belong to the initial heat-resistant type or the long-term heat-resistant type, and both are required to play a synergistic role. Oxidation is an important factor in the thermal degradation process, so it should be considered to be used together with antioxidants.
(2) It has good weather resistance, such as phosphorous acid, basic lead salt of sulfite, cadmium soap and organotin compounds (except mercaptans). www.handern.com Plastic sheet extrusion equipment
For rigid PVC, judging by discoloration, turbidity increase (transparent products), impact, tensile and bending strength decrease, it is considered that maleate organotin has the best weather resistance for hard transparent products, and basic lead salt has good weather resistance for opaque rigid rigid products, but whitening phenomenon will occur at the same time of aging and coloring. In addition, when used with titanium dioxide, it will turn black under light.
According to the phenomenon of discoloration, stain formation and expansion, stickiness, hardening and cracking, the weathering resistance of barium cadmium / epoxide / phosphite ester composition for transparent products is the best, while the basic lead salt of phosphite or sulphurous acid is the best for opaque PVC.
(3) different molding processes require different additives. When calendering, it is desirable to mix the mixture with plasticizing (gelatinization), non stick rollers (demoulding, lubricity) and no layer sticking phenomenon. When extruding and injection molding, it is desirable to mix the mixture with lubricity, fluidity and easy demoulding. Plasticizing paste requires defoaming and viscosity stability.
Metal soap has good processability and lubricity. Lead soap has good lubricity, low mixing torque value, but slow plasticization; cadmium soap and dibasic lead plasticize faster, and mixing torque value is also low; calcium and barium soap plasticizes fast and mixing: torque value is high, so it is necessary to mix properly. Inorganic lead salt has poor processability and needs to be used together with metal soap or lubricant. Dibutyltin in organotin compounds has good processability, but maleic esters have poor processability, so they will stick to the roller during mixing and need to be used together with lubricants.
(4) The phenomenon that stabilizer or additive precipitates from the mixture and adheres to the surface of roller screw, material wall and mold in the process of sedimentation lamination is also known as pressure precipitation. Adhesive layer is a kind of sticky deposit, which is easy to decompose, pollute and corrode metal surface. Calcium, barium and fatty acid soaps in metal soaps are easy to precipitate. Alumina, silica gel, stearic acid, triphenyl phosphite, anionic or cationic surfactants have the effect of inhibiting the deposition layer, while the organotin stabilizer does not produce the deposition layer. Therefore, it is necessary to select the appropriate formula. www.handern.com Plastic sheet extrusion equipment
(5) Compatibility requires good compatibility of stabilizer in PVC, not easy to exude, no frost and sweat. Exudates can affect the appearance and physical properties of the product (such as mechanical strength, chemical resistance, electrical insulation, optical properties and weather resistance), as well as adhesion, welding, printing and surface decoration.
1. Definition and requirements
Plastics are degraded due to heat, friction, shear and other physical effects in the molding process, and external conditions such as heat, light and oxygen in the process of use, so that the performance of the products will deteriorate or even lose the use value. In order to inhibit this effect, heating stabilizer should be added. The dehydrochlorination reaction occurs when PVC is heated above 100 ° C. the degradation reaction is accelerated at the molding temperature (above 170 ° C). In addition to dehydrochlorination, the PVC also changes color and crosslinks, which makes the performance worse. Therefore, heat stabilizers must be added to PVC to inhibit the above effects, which can capture hydrogen chloride.
Heat stabilizers are mainly used for PVC, but due to the structural defects of PE, PP and pur, heat stabilizers are sometimes added. The main factors affecting the thermal degradation of PVC are chain structure (branch chain, double bond, allyl chloride, head structure, conjugated double bond and molecular weight, etc.). Of course, oxygen, hydrogen chloride, additives and other external factors also have an impact. Therefore, the heat stabilizer should have the following functions: ① it can absorb or neutralize the hydrogen chloride released in the process of processing and use, and terminate its autocatalytic effect; ② replace the active and unstable chlorine atoms in the molecule to inhibit the dehydrochlorination reaction; ③ carry out double bond addition reaction with the polyene structure to eliminate or slow down the discoloration of the product; ④ prevent the oxidation of the polyene structure; ⑤ prevent the oxidation of the polyene structure And impurities in passivation resin, catalyst residues, end groups, etc.
2. Selection and evaluation of heat stabilizer www.handern.com Plastic sheet extrusion equipment
When choosing a kind of heat stabilizer, it is necessary to evaluate its various properties first, and then analyze and compare on this basis, so as to select a more satisfactory material. Due to many factors affecting the thermal stability, the effects of various stabilizers are quite different, so it is often necessary to use several kinds of stabilizers to achieve satisfactory results. The additives are different from other additives in terms of heat resistance, heat resistance, heat resistance and other properties.
(1) Generally, static and dynamic thermal stability tests are used to judge the heat resistance of heat stabilizers; color and strength tests are carried out in the thermal aging chamber to evaluate whether the heat stabilizers belong to the initial heat-resistant type or the long-term heat-resistant type, and both are required to play a synergistic role. Oxidation is an important factor in the thermal degradation process, so it should be considered to be used together with antioxidants.
(2) It has good weather resistance, such as phosphorous acid, basic lead salt of sulfite, cadmium soap and organotin compounds (except mercaptans). www.handern.com Plastic sheet extrusion equipment
For rigid PVC, judging by discoloration, turbidity increase (transparent products), impact, tensile and bending strength decrease, it is considered that maleate organotin has the best weather resistance for hard transparent products, and basic lead salt has good weather resistance for opaque rigid rigid products, but whitening phenomenon will occur at the same time of aging and coloring. In addition, when used with titanium dioxide, it will turn black under light.
According to the phenomenon of discoloration, stain formation and expansion, stickiness, hardening and cracking, the weathering resistance of barium cadmium / epoxide / phosphite ester composition for transparent products is the best, while the basic lead salt of phosphite or sulphurous acid is the best for opaque PVC.
(3) different molding processes require different additives. When calendering, it is desirable to mix the mixture with plasticizing (gelatinization), non stick rollers (demoulding, lubricity) and no layer sticking phenomenon. When extruding and injection molding, it is desirable to mix the mixture with lubricity, fluidity and easy demoulding. Plasticizing paste requires defoaming and viscosity stability.
Metal soap has good processability and lubricity. Lead soap has good lubricity, low mixing torque value, but slow plasticization; cadmium soap and dibasic lead plasticize faster, and mixing torque value is also low; calcium and barium soap plasticizes fast and mixing: torque value is high, so it is necessary to mix properly. Inorganic lead salt has poor processability and needs to be used together with metal soap or lubricant. Dibutyltin in organotin compounds has good processability, but maleic esters have poor processability, so they will stick to the roller during mixing and need to be used together with lubricants.
(4) The phenomenon that stabilizer or additive precipitates from the mixture and adheres to the surface of roller screw, material wall and mold in the process of sedimentation lamination is also known as pressure precipitation. Adhesive layer is a kind of sticky deposit, which is easy to decompose, pollute and corrode metal surface. Calcium, barium and fatty acid soaps in metal soaps are easy to precipitate. Alumina, silica gel, stearic acid, triphenyl phosphite, anionic or cationic surfactants have the effect of inhibiting the deposition layer, while the organotin stabilizer does not produce the deposition layer. Therefore, it is necessary to select the appropriate formula. www.handern.com Plastic sheet extrusion equipment
(5) Compatibility requires good compatibility of stabilizer in PVC, not easy to exude, no frost and sweat. Exudates can affect the appearance and physical properties of the product (such as mechanical strength, chemical resistance, electrical insulation, optical properties and weather resistance), as well as adhesion, welding, printing and surface decoration.
Author：admin