Polyethylene (PE) and polypropylene (PP) are excellent in performance and low in cost, so films, sheets, and various injection molded products are widely used in various industries. In many cases, these products need to undergo secondary processing such as bonding, electroplating, painting, and printing. The emergence of metal/plastic/metal composite laminates and their important significance for the functional requirements of light weight, heat insulation, shock absorption and vibration reduction of cars, aerospace vehicles, and electronic equipment, and how to obtain high surface polarity and good bonding performance The problem of PE and PP sheet coils is to ensure sufficient bonding strength between the metal sheet and the plastic sheet coil.
1 The purpose of surface modification of PE and PP sheet coils. It has been known that there are three types of forces acting on the bonding interface: one is static force, such as the force generated by mechanical engagement and friction; the other is the intermolecular force on the bonding interface, when the adhesive is close to the adhered material. At 0.3-0.5 nm, van der Waals forces will be generated by the effects of dispersion, dipole, and hydrogen bonding; and three are chemical bonding forces. When the adhesive and the adherent material are close to 0.1-0.3 nm, a chemical reaction occurs to form a chemical bond, and the bond becomes sticky. The ability of bond strength to resist media corrosion depends primarily on chemical bonding forces. For PE and PP materials, they have the following features.
(1) PE and PP are composed only of carbon atoms and are non-polar or weakly polar high-molecular materials.
(2) The surface energy is low, and the critical surface tension is only about 31*10<-3 >N/m.
(3) High crystallinity and good chemical stability. And the commonly used molding processing methods will lead to the orientation of the surface layer molecules, increase the crystallinity of the molecule. Therefore, when various types of adhesives act on the surface thereof, it is difficult for the polymer chains and segments to diffuse and entangle, so that a strong adhesive force cannot be formed.
(4) PE and PP itself contain low molecular weight components, and various additives are added during processing. During the molding process, these small relative molecular mass materials will converge toward the surface, coupled with environmental pollution, will form a weak boundary layer with low strength. Therefore, according to the generation of adhesive force and the characteristics of PE and PP, the main purpose of the modification process is:
(1) Polarize the surface of the sheet coil by placing polar groups on the PE and PP. This has three functions. One is the increase of surface activity and surface energy, the other is the increase of intermolecular dipole forces due to the introduction of polar groups, and the third is the increase of binders and the introduction of polar groups. The possibility of forming chemical bonds at the bonding interface.
(2) Increase surface energy. This is mainly due to the increase of the polar component of the surface energy, which improves the wettability of the adhesive with the surface of PE and PP, creating the greatest intermolecular force and chemical force for the close intermolecular contact at the bonding interface. condition. At the same time, the gas adsorbed on the surfaces of PE and PP is eliminated, and the void ratio at the bonding interface is reduced, which provides the conditions for maximum mechanical meshing.
(3) Remove the weak boundary layer of the surface, increase the surface energy, and also avoid the influence of weak boundary layer with poor mechanical properties after bonding.
(4) Improve the surface roughness. It enhances the mechanical engagement on the bonding interface and provides a larger area for the intermolecular physical and chemical interactions at the bonding interface.
2 Modified treatment methods, basic principles and modified adhesive properties In order to obtain PE and PP sheet coils with high surface polarity and good bonding properties, two approaches can be used: First, PE and PP sheet coils For surface treatment, polar groups or polar monomers are formed on the surface layer; second, high-polarity PE, PP grafts, or polymer surface modifiers are mixed with PE and PP first, followed by extrusion. And other methods to manufacture sheet coils.
2.1 Modification of surface of PE and PP sheet coils and their adhesive properties 2.1.1 Surface chemical treatment The use of an acid liquid to strongly oxidize the surface molecules of the plastic to introduce carboxyl, aldehyde, carbonyl, etc. Group. The most typical and most effective one is the sulfuric acid-dichromate treatment liquid. After Briggs et al. treated PE and PP films with sulfuric acid-potassium dichromate solution, the surface O/C ratio increased by more than 20 times, and the bond strength increased significantly. Huang Farong obtained excellent adhesion strength by treating the surface of the PE sheet with sulfuric acid-potassium dichromate solution. The surface topography also changes. On the spherulite surface of PP, the irregular regions between spherulites are preferentially etched to form 10-15 祄 deep holes; on the lamellae, the middle region is etched to form 5 -20 祄 deep seams; After LDPE and HDPE treatment, the surface forms a fine rough morphology.
2.1.2 Surface flame treatment Combustible gas flame is used to instantaneously burn high temperature combustion plastic surfaces. Since the high temperature flame is a plasma, the flame contains excited radicals such as O, NO, NH, OH and CN radicals, ions, neutrons, etc. Oxygen-containing polar groups such as carboxyl, hydroxyl, and carbonyl groups and unsaturated double bonds are formed on the surface by dehydrogenation and oxidation of the plastic surface. The surface changes from non-polar to polar, and the surface energy increases. For PE and PP, the surface energy increased to 50 mJ/m2 and 43.8 mJ/m2, respectively. At the same time, the weak boundary layer of the surface is removed and the surface is also roughened. Huang Farong obtained excellent adhesion strength after flame treatment of the surface of the PE sheet.
2.1.3 Surface hot gases Cyanide air, oxygen, ozone and other gases and PE, PP surface oxidation reaction in a hot state, can make its surface to generate carbonyl, carboxyl, and other polar groups, thereby improving surface wettability and adhesion Connected. After the hot LDPE sheet is treated with ozone, the adhesion strength to the aluminum sheet is very good.
2.1.4 Surface Low-Temperature Plasma Treatment Surfaces of PE and PP are treated with low-temperature plasma containing electrons, ions, radicals, and other ionized gas particles generated by discharge devices such as corona and glow. Since the energy of most of the particles in the plasma is higher than the bond energy of the common chemical bonds in the polymer, when the plasma particles hit the surface of PE and PP, there is enough energy to initiate the break or recombination of various chemical bonds within a certain depth of the plastic surface. . When non-reactive plasmas of hydrogen and inert gas particles are used, they only transfer energy to surface molecules, which activates them to generate radicals that react with each other to form surface cross-linked layers. The wettability and reactivity of the surface are improved, and the weak boundary layer is strengthened. For example, the surface energy after PE treatment with argon plasma is 68.9 mJ/m 2 . When reactive plasmas are used, they will react with the surface by oxidation, nitridation, etc., and generate a large number of active groups on the surface. Oxygen plasma is a representative of this type. It introduces a large number of oxygen-containing groups on the plastic surface, such as carboxyl, carbonyl, hydroxyl, etc., to improve the surface chemical activity, and the surface is etched by oxidative decomposition. After Occhiello et al. treated the PP surface with oxygen plasma, the surface wettability improved. After Novak et al. treated the surface of isotactic PP, the surface energy increased by 30% and the adhesiveness increased.
2.1.5 Surface Irradiation Treatment Surfaces of PE and PP in an atmosphere such as air, chlorine, or SO2 irradiated with a certain intensity of ultraviolet rays, gamma rays, electron beams, X-rays, etc., can cause surface oxidation or cross-linking reactions, thereby increasing the Surface wettability and adhesion. Novak et al. irradiated the isotactic PP surface in the phosphorus oxychloride atmosphere with ultraviolet light, and the surface energy polar component increased from 0.16 mJ/m2 to 16.8 mJ/m2, and the surface energy increased by 53%.
2.1.6 Surface-bonded polar monomers can introduce low-molecular polar groups containing oxygen, nitrogen, etc. on the surfaces of PE and PP by the aforementioned methods. However, when the treated surface is stored in the air, due to decomposition of the oxygen-containing groups and rearrangement of the polar groups inward, the surface energy polar component decreases, the surface energy decreases, and the adhesiveness decreases. The polar monomer introduced by the grafting method is a macromolecule and is covalently bonded to the surface of the matrix. The commonly used polar monomers are: maleic anhydride (MAH), glycidyl methacrylate (GMA), methacrylic acid (MAA), acrylic acid (AA), dibutyl maleate (DBM), acrylate, Acrylonitrile, acrylamide, etc. For this purpose, an active reaction center is generated on the surface of the non-polar sheet coil by the action of external energy such as irradiation treatment, low-temperature plasma treatment, and chemical treatment. According to the surface active radical generation mechanism, there are three ways to graft polar monomers on the surface:
(1) In the coexistence of gas phase, liquid phase or solid phase monomer and sheet coil, the surface is activated by chemical or irradiation, plasma treatment, and reacts with the monomer to form a surface graft copolymer.
(2) The surface of the coil is activated to generate free radicals, which are then contacted directly with the gas or liquid monomer to form a surface graft copolymer.
(3) The surface of the coiled sheet is exposed to air to form peroxides after the activation treatment, and then peroxide polymerization is initiated in the liquid monomer. Jia Wei and others immersed the LDPE sheet in an acrylic acid aqueous solution, and the surface of the sheet was grafted with acrylic acid by co-irradiation with a cobalt source, thereby greatly improving the surface bonding performance of the PE sheet. Yamada et al. immersed the photosensitizer-treated PE plate in an aqueous solution of methacrylic acid MAA, and after irradiation with a high-pressure mercury lamp under a nitrogen atmosphere, the wettability and adhesiveness of the surface of the PE plate onto which the MAA was grafted were greatly improved. Novak et al. treated the surface of isotactic PP in oxygen and then grafted acrylamide onto the surface in nitrogen. The surface energy was 47% higher than that of the untreated one, and was superior to that of corona treatment.
2.1.7 Surface coating treatment A polar group-containing thermoplastic material is applied to a plastic surface by solution or melting, such as coating a film with a chlorinated isotactic polypropylene on the surface of the PP, and other materials. Hot press bonding strength is very good. In order to further improve the adhesion of the coating layer to PP, Tong Yiyi etc. first grafted MAH on isotactic PP and then chlorinated it. Grafting polar groups and chlorine increased the polarity of the coating layer. And adhesiveness. Yang et al. applied a layer of triphenylphosphine or cobalt acetylacetonate to the surface of PP and LDPE, and the bonding strength exceeded the strength of PE and PP itself, and the durability of the bonding strength was good.
2.2 Modification of PE and PP raw materials and their bonding performance 2.2.1 Solid phase grafting of polar monomers Chen Guohua et al. Using water-toluene as the medium for the solid phase of PE initiated by dibenzoyl peroxide (BPO) With the technique of methyl methacrylate, the thermocompression bonding strength between the grafted material and the aluminum foil greatly increased. Liu Cailin et al. used a plate-shaped force chemical reactor developed by Xu Wei et al. to grind at a certain ratio of PP and MAH at room temperature. Under the action of stress, PP was chemically degraded to generate macromolecular radicals, thereby triggering maleic anhydride in PP. Grafting to obtain PP-g-MAH copolymer. This method does not require initiators and solvents, providing a new way for PP solid phase graft modification.
2.2.2 Molten Grafted Polarity The monomer polymer material is subjected to high temperature, high pressure, anaerobic, high shear rate in the molten state, and will generate polymer chain breakage and generate free radicals. This provides a way for PE and PP to graft polar monomers, such as melt-blending with internal mixers and screw extruders. Among them, melt extrusion grafting is particularly suitable for industrial production. It mixes PE or PP with a certain proportion of polar monomer and initiator and then feeds it into the extruder. The PE or PP is prepared by melting, mixing, grafting reaction and molding process. Commonly used initiators include dicumyl peroxide (DCP) and butyl diperoxide (DT-BP). Cheng Weizhuang et al. separately melt-extruded acrylic acid, maleic anhydride, maleic acid, sodium maleate, hydroxypropyl acrylate, and glycidyl methacrylate onto LDPE. The peel strength of the grafted PE and aluminum foil after thermal compression bonding was increased by 1-3 times compared to the ungrafted one. Zhang Yuyi grafted MAH onto LDPE, and the peel strength and shear strength of the graft and steel were more than 10 times higher than that of the ungrafted one. Xu Weibing melt-extruded MAH onto PP. The shear strength of the grafted product after bonding with the aluminum sheet can reach 9MPa. Lin et al. made the PP-g-MAH melt-grafted with an internal mixer to form a sheet and formed a chemical bond when bonded with steel. After the sheet was hydrolyzed, the adhesive strength with steel was further improved. Bongiovanni et al. will melt extrusion-bonded PE-(g-MAH made of film, bonding strength with steel and other materials than oxygen plasma treated PE surface.
In the process of single-cell melt grafting of PP, due to b-fragmentation of the tertiary carbon macro-radicals, the chain cleavage reaction causes PP degradation and the grafting rate is low. For this purpose, dual-cell melt grafting was developed to prepare highly polar PP and PE. For example, PP-g-(GMA-St), PP-g-(MMA-St), and PP-g-(HEMA-St) were prepared by melt extrusion grafting. The carbonyl peak of the graft was compared with that of the non-St. Obviously increased. After a small amount of St is added, St preferentially grafts onto PP to form a stable styrene-based macromolecular radical, and then reacts with GMA, MMA or HEMA, and the reaction rate is much faster than that of GMA, MMA or HEMA.
1 The purpose of surface modification of PE and PP sheet coils. It has been known that there are three types of forces acting on the bonding interface: one is static force, such as the force generated by mechanical engagement and friction; the other is the intermolecular force on the bonding interface, when the adhesive is close to the adhered material. At 0.3-0.5 nm, van der Waals forces will be generated by the effects of dispersion, dipole, and hydrogen bonding; and three are chemical bonding forces. When the adhesive and the adherent material are close to 0.1-0.3 nm, a chemical reaction occurs to form a chemical bond, and the bond becomes sticky. The ability of bond strength to resist media corrosion depends primarily on chemical bonding forces. For PE and PP materials, they have the following features.
(1) PE and PP are composed only of carbon atoms and are non-polar or weakly polar high-molecular materials.
(2) The surface energy is low, and the critical surface tension is only about 31*10<-3 >N/m.
(3) High crystallinity and good chemical stability. And the commonly used molding processing methods will lead to the orientation of the surface layer molecules, increase the crystallinity of the molecule. Therefore, when various types of adhesives act on the surface thereof, it is difficult for the polymer chains and segments to diffuse and entangle, so that a strong adhesive force cannot be formed.
(4) PE and PP itself contain low molecular weight components, and various additives are added during processing. During the molding process, these small relative molecular mass materials will converge toward the surface, coupled with environmental pollution, will form a weak boundary layer with low strength. Therefore, according to the generation of adhesive force and the characteristics of PE and PP, the main purpose of the modification process is:
(1) Polarize the surface of the sheet coil by placing polar groups on the PE and PP. This has three functions. One is the increase of surface activity and surface energy, the other is the increase of intermolecular dipole forces due to the introduction of polar groups, and the third is the increase of binders and the introduction of polar groups. The possibility of forming chemical bonds at the bonding interface.
(2) Increase surface energy. This is mainly due to the increase of the polar component of the surface energy, which improves the wettability of the adhesive with the surface of PE and PP, creating the greatest intermolecular force and chemical force for the close intermolecular contact at the bonding interface. condition. At the same time, the gas adsorbed on the surfaces of PE and PP is eliminated, and the void ratio at the bonding interface is reduced, which provides the conditions for maximum mechanical meshing.
(3) Remove the weak boundary layer of the surface, increase the surface energy, and also avoid the influence of weak boundary layer with poor mechanical properties after bonding.
(4) Improve the surface roughness. It enhances the mechanical engagement on the bonding interface and provides a larger area for the intermolecular physical and chemical interactions at the bonding interface.
2 Modified treatment methods, basic principles and modified adhesive properties In order to obtain PE and PP sheet coils with high surface polarity and good bonding properties, two approaches can be used: First, PE and PP sheet coils For surface treatment, polar groups or polar monomers are formed on the surface layer; second, high-polarity PE, PP grafts, or polymer surface modifiers are mixed with PE and PP first, followed by extrusion. And other methods to manufacture sheet coils.
2.1 Modification of surface of PE and PP sheet coils and their adhesive properties 2.1.1 Surface chemical treatment The use of an acid liquid to strongly oxidize the surface molecules of the plastic to introduce carboxyl, aldehyde, carbonyl, etc. Group. The most typical and most effective one is the sulfuric acid-dichromate treatment liquid. After Briggs et al. treated PE and PP films with sulfuric acid-potassium dichromate solution, the surface O/C ratio increased by more than 20 times, and the bond strength increased significantly. Huang Farong obtained excellent adhesion strength by treating the surface of the PE sheet with sulfuric acid-potassium dichromate solution. The surface topography also changes. On the spherulite surface of PP, the irregular regions between spherulites are preferentially etched to form 10-15 祄 deep holes; on the lamellae, the middle region is etched to form 5 -20 祄 deep seams; After LDPE and HDPE treatment, the surface forms a fine rough morphology.
2.1.2 Surface flame treatment Combustible gas flame is used to instantaneously burn high temperature combustion plastic surfaces. Since the high temperature flame is a plasma, the flame contains excited radicals such as O, NO, NH, OH and CN radicals, ions, neutrons, etc. Oxygen-containing polar groups such as carboxyl, hydroxyl, and carbonyl groups and unsaturated double bonds are formed on the surface by dehydrogenation and oxidation of the plastic surface. The surface changes from non-polar to polar, and the surface energy increases. For PE and PP, the surface energy increased to 50 mJ/m2 and 43.8 mJ/m2, respectively. At the same time, the weak boundary layer of the surface is removed and the surface is also roughened. Huang Farong obtained excellent adhesion strength after flame treatment of the surface of the PE sheet.
2.1.3 Surface hot gases Cyanide air, oxygen, ozone and other gases and PE, PP surface oxidation reaction in a hot state, can make its surface to generate carbonyl, carboxyl, and other polar groups, thereby improving surface wettability and adhesion Connected. After the hot LDPE sheet is treated with ozone, the adhesion strength to the aluminum sheet is very good.
2.1.4 Surface Low-Temperature Plasma Treatment Surfaces of PE and PP are treated with low-temperature plasma containing electrons, ions, radicals, and other ionized gas particles generated by discharge devices such as corona and glow. Since the energy of most of the particles in the plasma is higher than the bond energy of the common chemical bonds in the polymer, when the plasma particles hit the surface of PE and PP, there is enough energy to initiate the break or recombination of various chemical bonds within a certain depth of the plastic surface. . When non-reactive plasmas of hydrogen and inert gas particles are used, they only transfer energy to surface molecules, which activates them to generate radicals that react with each other to form surface cross-linked layers. The wettability and reactivity of the surface are improved, and the weak boundary layer is strengthened. For example, the surface energy after PE treatment with argon plasma is 68.9 mJ/m 2 . When reactive plasmas are used, they will react with the surface by oxidation, nitridation, etc., and generate a large number of active groups on the surface. Oxygen plasma is a representative of this type. It introduces a large number of oxygen-containing groups on the plastic surface, such as carboxyl, carbonyl, hydroxyl, etc., to improve the surface chemical activity, and the surface is etched by oxidative decomposition. After Occhiello et al. treated the PP surface with oxygen plasma, the surface wettability improved. After Novak et al. treated the surface of isotactic PP, the surface energy increased by 30% and the adhesiveness increased.
2.1.5 Surface Irradiation Treatment Surfaces of PE and PP in an atmosphere such as air, chlorine, or SO2 irradiated with a certain intensity of ultraviolet rays, gamma rays, electron beams, X-rays, etc., can cause surface oxidation or cross-linking reactions, thereby increasing the Surface wettability and adhesion. Novak et al. irradiated the isotactic PP surface in the phosphorus oxychloride atmosphere with ultraviolet light, and the surface energy polar component increased from 0.16 mJ/m2 to 16.8 mJ/m2, and the surface energy increased by 53%.
2.1.6 Surface-bonded polar monomers can introduce low-molecular polar groups containing oxygen, nitrogen, etc. on the surfaces of PE and PP by the aforementioned methods. However, when the treated surface is stored in the air, due to decomposition of the oxygen-containing groups and rearrangement of the polar groups inward, the surface energy polar component decreases, the surface energy decreases, and the adhesiveness decreases. The polar monomer introduced by the grafting method is a macromolecule and is covalently bonded to the surface of the matrix. The commonly used polar monomers are: maleic anhydride (MAH), glycidyl methacrylate (GMA), methacrylic acid (MAA), acrylic acid (AA), dibutyl maleate (DBM), acrylate, Acrylonitrile, acrylamide, etc. For this purpose, an active reaction center is generated on the surface of the non-polar sheet coil by the action of external energy such as irradiation treatment, low-temperature plasma treatment, and chemical treatment. According to the surface active radical generation mechanism, there are three ways to graft polar monomers on the surface:
(1) In the coexistence of gas phase, liquid phase or solid phase monomer and sheet coil, the surface is activated by chemical or irradiation, plasma treatment, and reacts with the monomer to form a surface graft copolymer.
(2) The surface of the coil is activated to generate free radicals, which are then contacted directly with the gas or liquid monomer to form a surface graft copolymer.
(3) The surface of the coiled sheet is exposed to air to form peroxides after the activation treatment, and then peroxide polymerization is initiated in the liquid monomer. Jia Wei and others immersed the LDPE sheet in an acrylic acid aqueous solution, and the surface of the sheet was grafted with acrylic acid by co-irradiation with a cobalt source, thereby greatly improving the surface bonding performance of the PE sheet. Yamada et al. immersed the photosensitizer-treated PE plate in an aqueous solution of methacrylic acid MAA, and after irradiation with a high-pressure mercury lamp under a nitrogen atmosphere, the wettability and adhesiveness of the surface of the PE plate onto which the MAA was grafted were greatly improved. Novak et al. treated the surface of isotactic PP in oxygen and then grafted acrylamide onto the surface in nitrogen. The surface energy was 47% higher than that of the untreated one, and was superior to that of corona treatment.
2.1.7 Surface coating treatment A polar group-containing thermoplastic material is applied to a plastic surface by solution or melting, such as coating a film with a chlorinated isotactic polypropylene on the surface of the PP, and other materials. Hot press bonding strength is very good. In order to further improve the adhesion of the coating layer to PP, Tong Yiyi etc. first grafted MAH on isotactic PP and then chlorinated it. Grafting polar groups and chlorine increased the polarity of the coating layer. And adhesiveness. Yang et al. applied a layer of triphenylphosphine or cobalt acetylacetonate to the surface of PP and LDPE, and the bonding strength exceeded the strength of PE and PP itself, and the durability of the bonding strength was good.
2.2 Modification of PE and PP raw materials and their bonding performance 2.2.1 Solid phase grafting of polar monomers Chen Guohua et al. Using water-toluene as the medium for the solid phase of PE initiated by dibenzoyl peroxide (BPO) With the technique of methyl methacrylate, the thermocompression bonding strength between the grafted material and the aluminum foil greatly increased. Liu Cailin et al. used a plate-shaped force chemical reactor developed by Xu Wei et al. to grind at a certain ratio of PP and MAH at room temperature. Under the action of stress, PP was chemically degraded to generate macromolecular radicals, thereby triggering maleic anhydride in PP. Grafting to obtain PP-g-MAH copolymer. This method does not require initiators and solvents, providing a new way for PP solid phase graft modification.
2.2.2 Molten Grafted Polarity The monomer polymer material is subjected to high temperature, high pressure, anaerobic, high shear rate in the molten state, and will generate polymer chain breakage and generate free radicals. This provides a way for PE and PP to graft polar monomers, such as melt-blending with internal mixers and screw extruders. Among them, melt extrusion grafting is particularly suitable for industrial production. It mixes PE or PP with a certain proportion of polar monomer and initiator and then feeds it into the extruder. The PE or PP is prepared by melting, mixing, grafting reaction and molding process. Commonly used initiators include dicumyl peroxide (DCP) and butyl diperoxide (DT-BP). Cheng Weizhuang et al. separately melt-extruded acrylic acid, maleic anhydride, maleic acid, sodium maleate, hydroxypropyl acrylate, and glycidyl methacrylate onto LDPE. The peel strength of the grafted PE and aluminum foil after thermal compression bonding was increased by 1-3 times compared to the ungrafted one. Zhang Yuyi grafted MAH onto LDPE, and the peel strength and shear strength of the graft and steel were more than 10 times higher than that of the ungrafted one. Xu Weibing melt-extruded MAH onto PP. The shear strength of the grafted product after bonding with the aluminum sheet can reach 9MPa. Lin et al. made the PP-g-MAH melt-grafted with an internal mixer to form a sheet and formed a chemical bond when bonded with steel. After the sheet was hydrolyzed, the adhesive strength with steel was further improved. Bongiovanni et al. will melt extrusion-bonded PE-(g-MAH made of film, bonding strength with steel and other materials than oxygen plasma treated PE surface.
In the process of single-cell melt grafting of PP, due to b-fragmentation of the tertiary carbon macro-radicals, the chain cleavage reaction causes PP degradation and the grafting rate is low. For this purpose, dual-cell melt grafting was developed to prepare highly polar PP and PE. For example, PP-g-(GMA-St), PP-g-(MMA-St), and PP-g-(HEMA-St) were prepared by melt extrusion grafting. The carbonyl peak of the graft was compared with that of the non-St. Obviously increased. After a small amount of St is added, St preferentially grafts onto PP to form a stable styrene-based macromolecular radical, and then reacts with GMA, MMA or HEMA, and the reaction rate is much faster than that of GMA, MMA or HEMA.
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