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    Home > Coatings News > Paints and Coatings Market > Coating technology: preparation and properties of UV curable hydrophilic coating

    Coating technology: preparation and properties of UV curable hydrophilic coating

    • Last Update: 2020-04-03
    • Source: Internet
    • Author: User
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    Core tip: preparation and properties of UV curable hydrophilic coating It is suggested that the photosensitive monomer glycidyl methacrylate (GMA) is introduced into the acrylate hydrophilic resin, which makes the film solidified at room temperature and has good hydrophilicity and water resistance The effects of the mole fraction of initiator and chain transfer agent on the molecular weight and dispersion of acrylate copolymer, and the effects of diluent, monomer ratio and GMA mole fraction on the hydrophilicity and water resistance of the film were studied Abstract: photosensitive monomer glycidyl methacrylate (GMA) was introduced into acrylate hydrophilic resin to make the film stable Shenyang steel structure fireproof coating construction expert punde Building Fire Engineering Co., Ltd Recommended introduction: since its establishment, Shenyang punde Construction Fire Engineering Co., Ltd has cultivated a group of professional construction teams with excellent equipment, rich experience and serious responsibility with advanced and scientific management methods and strict engineering quality assurance and after-sales service system It has undertaken a number of fire system installation projects, which has been praised by customers Every idea and special requirement of you will be fully considered by us and fully realized in the construction technology, which will become the cornerstone of our successful long-term development We are looking forward to your invitation, to provide you with quality services and high-quality technical support! All construction coatings have passed ISO9001 Home of coatings: the core of preparation and Performance Research of UV curable hydrophilic coating is to introduce photosensitive monomer glycidyl methacrylate (GMA) into acrylate hydrophilic resin, so that the coating can be cured at room temperature and has good hydrophilicity and water resistance The effects of the mole fraction of initiator and chain transfer agent on the molecular weight and dispersion of acrylate copolymer, and the effects of diluent, monomer ratio and GMA mole fraction on the hydrophilicity and water resistance of the film were studied Abstract: the photosensitive monomer glycidyl methacrylate (GMA) is introduced into the acrylate hydrophilic resin, which makes the film solidified at room temperature and has good hydrophilicity and water resistance The effects of the mole fraction of initiator and chain transfer agent on the molecular weight and dispersion of acrylate copolymer, and the effects of diluent, monomer ratio and GMA mole fraction on the hydrophilicity and water resistance of the film were studied The experimental results show that when the mole fraction of initiator is 1.2% and the mole fraction of chain transfer agent is 2%, the acrylate copolymer with molecular weight of 1300 and molecular weight dispersion of 1.85 can be prepared; When the mole fraction of GMA is 15% (relative to the amount of AA material), the diluent is hydroxypropyl acrylate (HPA), and the mass fraction is 30%, and the mass ratio of AA to HPA is 6:4, the comprehensive properties of hydrophilicity and water resistance of the film are the best, the hydrophilicity angle is 14.2%, and the weight loss rate is 1.61% UV curable coatings are widely used in paper, rubber, plastic and other coating fields due to their advantages of fast curing speed, environmental friendliness, energy saving and low cost Generally speaking, light-sensitive liquid resin can be directly converted into curing resin under UV light at room temperature, and generally does not contain volatile organic compounds With the attention to environmental issues, the research, development and application of this environmental protection "green" process are more and more in-depth and popular Hydrophilic coating is a kind of functional coating developed rapidly in recent years It is mainly used in aluminum and aluminum alloy products, such as the aluminum fins of air conditioning heat exchanger The traditional hydrophilic coating is usually made by baking the hydrophilic resin at 200 ℃ for tens of seconds, then heat curing and cross-linking Although the preparation process is mature and hydrophilic, it consumes a lot of energy, volatilizes a lot of organic solvents and has a poor construction environment The preparation of pure organic hydrophilic coating by UV curing and cross-linking not only takes advantage of the advantages of UV curing but also meets the requirements of hydrophilicity, which has not been reported yet In this paper, a new synthesis method is used Based on the low molecular weight acrylate copolymer, photosensitive monomers are introduced, and then the hydrophilic coating is prepared by light curing and cross-linking The influence of GMA introduction, monomer proportion, active diluent type and content on the hydrophilicity and water resistance of the coating is investigated 1 Experimental part 1.1 experimental raw materials: acrylic acid (AA), hydroxypropyl acrylate (HPA), butyl acetate, glycol monomethyl ether, AIBN, dodecyl mercaptan, tetrabutylammonium bromide, hydroquinone, glycidyl methacrylate (GMA), N-vinyl pyrrolidone (NVP), all of which are analytical pure, Beijing Chemical Reagent Company; Photoinitiator 1173, 1, 6-hexanediol diacrylate (HDDA), industrial grade, dibixi Chemical Trade Co., Ltd 1.2 the synthesis of photosensitive hydrophilic acrylic resin add a certain amount of mixed solvent of butyl acetate and glycol monomethyl ether in four bottle, and raise the temperature to about 70 ℃; dissolve the measured initiator azodiisobutyronitrile and dodecyl mercaptan in the mixed monomer acrylic acid and hydroxypropyl acrylate, and then drop the mixed solution into four bottle within 4-5h for polymerization, and keep the temperature for 2h After the polymerization, the temperature of the system was raised to 105-110 ℃, and a certain amount of GMA, tetrabutylammonium bromide catalyst and hydroquinone were added The reaction lasted for 2.5h, and a photosensitive hydrophilic prepolymer was obtained The specific reaction process is shown in Figure 1 Fig 1 synthesis of photosensitive hydrophilic prepolymer Fig 1.3 preparation of UV curable coating vacuum distillation of photosensitive hydrophilic prepolymer, adding photoinitiator and active diluent, stirring and dispersing evenly Then, the wire rod coater (XB type, Shanghai Standard Instrument Co., Ltd.) was used to coat the surface of the treated aluminum foil, and the hydrophilic coating was prepared by exposing it under the high pressure mercury lamp for 2min 1.4 the infrared spectrum of acrylate prepolymer was characterized by nexus670 Fourier infrared spectrometer of nigolli company of USA; the hydrophilic angle of coating was measured by oca20 contact angle measuring instrument of DataPhysics company of Germany; the viscosity of coating was measured by DV - Ⅲ ultra viscosity instrument of Kuiyuan Scientific Instrument Co., Ltd of Shanghai The water resistance of the coating was characterized by weight loss rate The test of weight loss rate is: immerse the coating in flowing water, take it out 24 hours later, dry it to constant weight at room temperature, cycle it for 3 times, and then weigh the quality of the coating before and after immersion The formula of weight loss s is s = (m0-m1) / M0 (1), in which M0 is the mass before coating soaking and M1 is the mass after coating soaking 2 Results and discussion 2.1 the molecular weight and molecular weight dispersion of acrylate copolymer are copolymerized with 20g acrylic acid and 13.4g hydroxypropyl acrylate The relationship between the molecular weight and molecular weight dispersion of copolymer and the content of initiator and chain transfer agent is shown in Table 1 Table 1 Relationship between initiator and chain transfer agent content in free radical polymerization system, polymerization degree xn of polymer can be expressed as In formula (2), the chain initiation rate constant KP, the chain growth rate constant KD, the chain termination rate constant KT, the chain transfer constant KS, and the polymerization efficiency f are all fixed values Therefore, when the monomer concentration cm is fixed, the polymerization degree xn is only related to the initiator concentration Ci and the chain transfer agent concentration CS It can be seen from table 1 that when the monomer mass is constant and the mole fraction of chain transfer agent is fixed at 1%, the molecular weight of the copolymer decreases from 4300 to about 1000 with the increase of initiator content As the mole fraction of initiator increases, the density of free radicals increases, that is, the active center increases, which leads to the decrease of polymerization degree, molecular weight and molecular weight dispersion However, the content of initiator can not be increased indefinitely, because the polymerization of acrylic acid is a strong exothermic reaction If the content of initiator is too large and the reaction is too fast, it will lead to local overheating and cross-linking of hydroxyl and carboxyl groups of polymer, resulting in white insoluble The molecular weight of the polymer decreased with the increase of the concentration of chain transfer agent When the mole fraction of chain transfer agent is 2%, the dispersion of molecular weight is the smallest Theoretically, one azodiisobutyronitrile decomposes two free radicals, one chain transfer agent terminates one free radical, so the dispersion is the lowest when the concentration of chain transfer agent is twice that of initiator However, the efficiency of the initiator can not reach 1, and free radicals can transfer to solvents, etc., so the dispersion is the smallest when the amount ratio of chain transfer agent to initiator is slightly less than 2 As can be seen in Table 1, when the mole fraction of initiator is 1.2% and the mole fraction of chain transfer agent is 2%, the molecular weight of the copolymer is about 1300 and the molecular weight dispersion is 1.85 2.2 infrared spectrum analysis of acrylate and photosensitive acrylate Fig 2 is the infrared spectrum of acrylate copolymer (a) and photosensitive acrylate oligomer (b) Fig 2 infrared spectrum of acrylate copolymer (a) and photosensitive acrylate oligomer (b) In Figure 2, the characteristic peak of C-O on the carboxyl group of acrylic acid appears at 1731.4cm-1, the characteristic absorption peak of CO on the hydroxypropyl acrylate appears at 1170.1cm-1, and the broad and strong characteristic peak of hydroxyl group appears at 3340.2cm-1, indicating the existence of carboxyl group and hydroxyl group, and the copolymerization of a a and HPA takes place The characteristic absorption peaks of C = C double bond appeared at 1635.9cm-1 and 812.8cm-1 in the b-curve, and there was no characteristic absorption peak of epoxy group at 908cm-1, which indicated that the epoxy group on GMA and the carboxyl group of acrylate had esterification reaction, and the acrylate was grafted with GMA to prepare acrylate resin with double bond 2.3 factors affecting coating performance 2.3.1 diluent because acrylate copolymer contains a large number of hydroxyl and carboxyl groups, the hydrogen bond between polymers is strong, and the viscosity of the system is high, so a certain amount of diluent must be added to adjust the viscosity The active diluents given in Table 2 are HPA, NVP and HDDA The dosage of the three diluents in Table 2 is the same, and the mass fraction is 30% of the coating formula It can be seen from table 2 that the hydrophilic angle of HDDA film is large because it does not contain hydrophilic group Although NVP has good hydrophilicity, it does not have water resistance, and the weight loss rate is too high At the same time, the compatibility of NVP with oligomer is not good, and the color of the film is too deep Therefore, HPA is the best active diluent in this system considering the hydrophilicity and water resistance of the film, the color of the film and the viscosity of the system before the film Table 2 Influence of diluent types on film properties HPA single functional group active diluent only contains one C  C double bond that can participate in curing reaction per molecule, generally with high conversion, low curing speed, low crosslinking density, etc As the active diluent is directly involved in the curing reaction, the amount of diluent will also have a significant impact on the comprehensive performance of the coating The relationship between the amount of HPA diluent and the viscosity, hydrophilicity and water resistance of the coating is shown in Table 3 Table 3 Effect of diluent dosage on hydrophilic angle and water resistance of the film it can be found from table 3 that the smaller the diluent content is, the smaller the hydrophilic angle is When the mass fraction of HPA was 20%, the hydrophilic angle decreased to 13.1 ° Because when the amount of diluent is small, the proportion of hydrophilic resin is large, the density of hydrophilic functional group is increased, especially the carboxyl group is increased, so the hydrophilic angle becomes smaller However, when the mass fraction of HPA is 20%, the viscosity of the coating solution is too high and it is not easy to operate When the HPA content was more than 30%, the weight loss rate of the film increased significantly When the diluent content increased to 50%, the weight loss rate could reach 5.93% This is due to the increase of the amount of single functional group diluent, the decrease of crosslinking density and the decrease of water resistance In comparison, the quality fraction of HPA is 30% 2.3.2 the hydrophilicity of monomer proportion coating is mainly affected by hydrophilic resin, and the hydrophilicity of resin depends on the hydrophilic group on the molecular chain
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