The influence of the polymerization on properties of an ethylacrylate/2-ethyl hexylacrylate pressure-sensitive adhesive suspension

In this paper, the batch suspension copolymerization process for production of microsphere acrylic pressure-sensitive adhesives (PSA) is presented. The effects of different process and chemical parameters on adhesion properties are discussed. The reaction was monitored in-line by using attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopy. Properties of the adhesive suspension (particle size), adhesive (gel phase, molecular weight, glass transition temperature (T_g)) and adhesion properties (tack, peel strength and shear) were determined. The results have shown that reaction kinetics strongly depends on polymerization temperature and initiator concentration. On the other hand, adhesion properties depend mainly on the T_g of the polymer and on the amount of insoluble gel fraction in the adhesive.     

绷带用聚丙烯酸酯乳液型压敏胶的研制

合成了一种绷带用聚丙烯酸酯乳液型压敏胶,测试了乳液的粘度、压敏胶的T型剥离强度、初粘力及持粘力。结果表明:当反应温度为81～85℃、引发剂用量为0．35%～0．45%、复配乳化剂用量为3．8%时,制得的聚丙烯酸酯乳液性能较好;加入一定量的松香乳液,可有效地提高压敏胶的性能。     

The effect of varied monomer composition on adhesive performance and peeling master curves for acrylic pressure‐sensitive adhesives

A group of pressure‐sensitive adhesives were prepared with constant glass transition temperature, using emulsion polymerization. The monomers chosen were butyl acrylate, 2‐ethylhexyl acrylate, and methyl methacrylate, along with a small amount of acrylic acid. The proportion of acrylic acid monomer was held constant for each polymer preparation but acrylic ester monomer levels were varied. The glass transition temperatures of the acrylate copolymers were measured by using differential scanning calorimetry. Drying and weighing the tetrahydrofuran‐insoluble polymer fractions were used to determine the polymer gel fractions. Films of constant coating thickness were applied to poly(ethylene terephthalate) film and adhesive properties (tack and shear) were examined. Peel was examined through the construction of master curves derived from peel tests conducted over a range of temperatures and peel rates. As the 2‐ethylhexyl acrylate content increased, the latex gel fractions were found to increase. With increasing EHA and gel fraction, peel shear was found to increase. When peel force master curves were compared, divergence in peel master curves occurred as peel rates increased where polymers with higher butyl acrylate contents reached greater peel stress values. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 2909–2917, 2004     

Contents Lists and Abstracts from the China Journal “Chemistry and Adhesion”

In order to study the effect of surfactants on the adhesive properties, peel measurements were performed with two series of model polymers of ethylhexylmethacrylate (PEHMA), the first prepared by emulsion polymerization with four anionic surfactants, and the second by post-adding the same surfactants to a surfactant-free latex. Cohesive fracture is observed at low peel rates; the peel strength depends on the bulk mechanical properties and is independent of the emulsifier. A transition to another type of separation occurs at higher peel rates, which seems to be an interfacial failure by visual inspection. Surface analytical studies, however, give evidence that this “interfacial” failure is, in fact, a mixed failure, leaving traces of the polymer on the substrate surface. The peel rate at this transition as well as the peel strength at mixed fracture are influenced by the surfactants. Large differences were observed between the four surfactants as well as between both series of polymers, leading to the conclusion that the surfactants have a different mobility within the film. This is also reflected by a different aging behaviour of the films.     

The Influence of Surfactants on the Peel Strength of Water-based Pressure Sensitive Adhesives

In order to study the effect of surfactants on the adhesive properties, peel measurements were performed with two series of model polymers of ethylhexylmethacrylate (PEHMA), the first prepared by emulsion polymerization with four anionic surfactants, and the second by post-adding the same surfactants to a surfactant-free latex. Cohesive fracture is observed at low peel rates; the peel strength depends on the bulk mechanical properties and is independent of the emulsifier. A transition to another type of separation occurs at higher peel rates, which seems to be an interfacial failure by visual inspection. Surface analytical studies, however, give evidence that this “interfacial” failure is, in fact, a mixed failure, leaving traces of the polymer on the substrate surface. The peel rate at this transition as well as the peel strength at mixed fracture are influenced by the surfactants. Large differences were observed between the four surfactants as well as between both series of polymers, leading to the conclusion that the surfactants have a different mobility within the film. This is also reflected by a different aging behaviour of the films.     

氢化丙烯酸松香/丙烯酸酯复合乳液的制备及其压敏胶的性能

以氢化丙烯酸松香为增黏树脂,将其溶解在丙烯酸酯单体中,预乳化后采用半连续乳液聚合工艺制备了氢化丙烯酸松香/丙烯酸酯复合乳液。研究了氢化丙烯酸松香的用量对单体转化率、凝胶率、溶胶相对分子质量及其分布、乳胶膜的玻璃化温度(Tg)和压敏胶粘接性能等的影响。结果表明,氢化丙烯酸松香对单体聚合具有一定的阻聚作用,随着氢化丙烯酸松香用量的增加,单体转化率、凝胶率及相对分子质量下降,相对分子质量分布变窄。氢化丙烯酸松香的合适用量为8.0%wt,此时压敏胶的初黏力为15#,180°剥离强度为10.6N.25mm-1,持黏力大于120h。     

聚合温度对萜烯基水性丙烯酸酯压敏胶的影响

通过萜烯树脂对乳液型丙烯酸酯压敏胶（PSA）进行改性。用预乳化半连续的方法合成改性丙烯酸酯乳液。考察了聚合温度对乳液的性能、聚合反应过程的转化率及压敏胶力学性能的影响,结果表明：聚合温度为81℃时,所制得乳液的性能最佳、单体的转化率最高及作为压敏胶的初黏力为25#,剥离强度5．64N·25mm^-1,持黏力为36h。同时用GPC、FTIR、DSC及TEM进行微观分析表明：聚合物的平均相对分子质量及相对分子质量分布分别随温度的升高变小变宽,适量的萜烯树脂参与各单体共聚且玻璃化温度为-30．63℃,乳胶粒的直径为200nm。     

乳液型竹纤维素-丙烯酸酯压敏胶制备初探

以提取竹纤维素为交联剂,采用半连续乳液聚合法合成制备竹纤维素-丙烯酸酯乳液型压敏胶。结果表明:聚合体系温度85℃,搅拌速率为150r/min,聚合3h,当软硬单体的体积比4:1,硬单体中甲基丙烯酸与醋酸乙烯酯体积比为1:4,引发剂用量为总量的0.30%,竹纤维素添加量为总质量的0.6%,反应时间为3h,可制备得到性能良好的压敏胶,其黏度为21.3 mPa·s,剥离强度为0.692 N/mm,可为新型竹纤维素基质压敏胶研究提供有益参考。     

Power feed synthesis of pressure-sensitive latex adhesives

Latex particles with the same core composition of poly(MMA-co-ALMA) and different shell compositions of poly(BA-co-AA) were prepared by semibatch emulsion polymerization using ‘power feed’ monomer and chain transfer agent addition methods in the shell layers. The seed stage involved formation of seed particles of 111 nm in diameter with a batch process. After that, two growth stages formed the final particle diameter, d_z = 300 nm measured by dynamic light scattering. The gel content and the molecular parameters of the polymer were determined. The adhesive properties including loop tack, peel force and shear resistance were measured according to the FINAT test methods No. 9, 1 and 8. An evaluation was also made for the relationship between pressure-sensitive properties and molecular parameters. Introducing power feed to semibatch emulsion polymerization had no significant effect on the latex preparations and could improve the final conversion and the colloidal stability. The observed particles were grown without significant secondary nucleation. The power feed methods had no effect on the glass transfer temperature (T_g) of the shell layer also. Emulsion polymerization conducted by positive power feed resulted in the formation of longer primary polymer chains at the beginning than that conducted by negative power feed and standard uniform feed, which caused a very high gel fraction. As pressure-sensitive adhesives prepared by using the positive power feed had the highest gel content and strongest core–shell interaction, they exhibited the highest shear resistance, but the lowest tack and peel force.     

Empirical Modeling of Butyl Acrylate/Vinyl Acetate/Acrylic Acid Emulsion‐Based Pressure‐Sensitive Adhesives

Summary: Butyl acrylate/vinyl acetate/acrylic acid (BA/VAc/AA) emulsion latexes were produced in a semi‐batch mode. The objective was to generate polymers with properties favoring their application as pressure‐sensitive adhesives. The influence of the individual monomer concentrations on final properties such as glass transition temperature (T_g), peel strength, shear strength and tack was investigated. To obtain the maximum amount of information in a reasonable number of runs, a constrained three‐component mixture design was used to define the experimental conditions. Latexes were coated onto a polyethylene terephthalate carrier and dried. Different empirical models (e.g. linear, quadratic and cubic mixture models) governing the individual properties (i.e. T_g, peel adhesion, shear resistance and tack) were developed and evaluated. In the given experimental region, no single model was found to fit all of the responses (i.e. the final properties). However, in all models the most significant factor affecting the final properties was the AA concentration, followed by the VAc concentration.

Shear strength contour lines over the investigated region.     

Optical properties and adhesion performance of optically clear acrylic pressure sensitive adhesives using chelate metal acetylacetonate

Optically clear acrylic pressure-sensitive adhesives (PSAs) with different co-monomers were synthesized. This study employed metal chelate aluminum acetylacetonate and zirconium acetylacetonate as curing agents. The optical properties of the acrylic PSAs were examined by UV–visible spectroscopy and a prism coupler. In addition, the adhesion performance was obtained by assessing the peel strength, the tack, and the shear adhesion failure temperature. The decrease in the adhesion performance may be related to a higher crosslinking density, which also resulted in a higher gel content.     

脲基功能单体对丙烯酸酯PSA乳液性能的影响

以丙烯酸酯类单体为主要原料,将脲基功能单体[MAEEU(甲基丙烯酰胺乙基乙撑脲)]和DAAM(双丙酮丙烯酰胺)引入体系中,采用半连续乳液聚合法制备改性丙烯酸酯PSA(压敏胶)乳液。研究结果表明:MAEEU在乳液聚合后期加入且w(MAEEU)=3%时,PSA乳液的综合性能(如初粘力、持粘力、剥离强度和耐水性等)相对最好;此时PSA的Tg(玻璃化转变温度)从-36.47℃升至-8.95℃,说明在乳液成膜过程中MAEEU和DAAM可发生交联反应,并且交联效果明显;脲基功能单体的使用为提高乳液型PSA性能的研究提供了新的方法 。     

Scale-up of functional properties of pressure-sensitive adhesive from laboratory to industrial plant production: from monomers to label

A waterborne acrylic pressure-sensitive adhesive produced in a commercial plant to label market was successfully developed. In order to reach the required functional properties (i.e. holding time, peel, and loop tack strengths), glass transition temperature, functional monomer content, type of surfactant, and reaction temperature were optimized. A proper balance of wetting and thickening agents content was found taking into consideration their significant unfavorable effect on functional properties.     

On the graft polymerization of styrene and acrylonitrile onto polybutadiene in the presence of vinyl acetate. II. Properties of graft polymers

The properties of the graft polymers of styrene, acrylonitrile, and vinyl acetate onto polybutadiene rubber that were prepared for the modification of graft polymers of styrene and acrylonitrile onto polybutadiene (ABS polymers) by emulsion polymerization up to a high degree of conversion have been studied and discussed. Both the impact strength and notched impact strength of the graft polymers have been found to remarkably increase with a rising quantity of vinyl acetate, in particular, in the case of styrene substitution, whereas in the case of acrylonitrile substitution by vinyl acetate, the two characteristics become noticeably poorer. The effects of the vinyl acetate amount and the type of substituted monomers on bending strength, tensile strength, Vicat softening point, and glass transition temperature of the graft polymers are also clearly different. Furthermore, the properties of the above graft polymers blended with styrene/acrylonitrile copolymers have been studied.     

Preparation and properties of environment-friendly acrylic latex laminating adhesives applied in plastic/plastic composite films

Acrylic latex laminating adhesives (ALLAs) were successfully prepared via a monomer-starved seeded semi-continuous emulsion polymerization with butyl acrylate (BA), methyl methacrylate (MMA), styrene (St), acrylamide (Am), and methacrylate glycidyl ether (GMA) as monomers. Impacts of GMA on the final latex, the dried latex films and the adhesive properties of ALLAs were investigated, respectively. The results indicated that the increase of GMA contents in the pre-emulsion feed has no apparent effect on the final latex average particle size and size distribution, while the gel contents, glass transition temperature (T_g) and water contact angle of the ALLAs gradually increased, and the molecular weight (M_n, M_w) obviously increased. Additionally, as the amount of GMA increased from 0 to 10?wt%, the maximum peel strength of the composite films reached 3.72 N/15mm with 5?wt% GMA contents. When heated to 65?°C, the peel strength of the composite films with 5?wt% of GMA can still maintain an acceptable peel strength (2.51 N/15mm) for application, showing excellent adhesive performance and heat resistance properties.     

Tailoring of energetic groups in acroyloyl polymers

Acryloyl based novel energetic monomers having nitro acrylates and nitro triazole acrylates were synthesized and further used for polymerization. Due to scavanging properties of nitro groups, syntheses of nitro aromatic polymers are not facile at normal conditions. In this regard, we report a simple protocol to synthesize these energetic group embeded acroloyl polymers. These polymers were characterized by FTIR, and NMR spectroscopic techniques. gel permeation chromatography (GPC) technique was employed in order to understand molecular mass of these polymers along with average molecular weight, number average weight and poly dispersity index. Glass transition temperature (T_g) was determined by using DSC analysis. It was observed that with increase in nitro groups in polymers there is a decrease in glass transition temperature. Two steps degradation were depicted in the TGA thermograph in nitro containing polymers. Heat release during this reaction was found up to 951 J/g. Increase in nitrogen content in polymer unit enhanced the heat release of polymers.     

Effect of novel benzoxazine reactive diluent on processability and thermomechanical characteristics of bi‐functional polybenzoxazine

Effects of a monofunctional benzoxazine diluent (Ph‐a) on properties of a bifunctional benzoxazine resin (BA‐a) have been investigated. The BA‐a/Ph‐a mixtures are miscible in nature rendering the properties highly dependent on their compositions. The viscosity of the BA‐a resin can be reduced to one third using only about 10% by weight the Ph‐a diluent. The addition of the Ph‐a resin into the BA‐a resin can also lower the liquefying temperature of the resin mixtures whereas the gel point is marginally decreased. The gel point, which depends on the BA‐a/Ph‐a mixtures and the cure temperature, was determined by the frequency independence of loss tangent in the vicinity of the sol‐gel transition. The relaxation exponent values of the copolymer were found to be 0.24–0.55, which is dependent on the cure temperature. Gel time of the BA‐a/Ph‐a systems decreases with increasing temperature according to an Arrhenius relation with activation energy of 60.6 ± 1.5 kJ/mol. Flexural moduli of the BA‐a/Ph‐a polymers also increase with the Ph‐a mass fraction, however, with the sacrifice of their flexural strength and glass‐transition temperature. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Manipulation of chain transfer agent and cross-linker concentration to modify the performance of fluorinated acrylate latex pressure sensitive adhesive

Abstract

n-Dodecyl mercaptan (DDM) chain transfer agent and 1,6-hexanediol diacrylate (HDDA) cross-linker were used to manipulate latex properties in a monomer-starved seeded semi-continuous emulsion polymerization of butyl acrylate (BA), fluorine monomer dodecafluoroheptyl methacrylate (DFMA) together with acrylic acid (AA) and 2-hydroxyethyl acrylate (HEA). The influences of both DDM and HDDA on the particle size of the latex, as well as on the gel content, thermostability (differential scanning calorimeter and thermal gravimetric analysis), surface properties (X-ray photoelectron spectra (XPS), contact angle analysis and atomic force microscopy), and viscoelasticity (N,N-dimethylacrylamide) of the polymer films were investigated. The results showed that the introduction of DDM and HDDA has no significant effects on the final particle size of the fluorinated pressure-sensitive adhesives (PSA) latexes. XPS analysis indicated that the fluoroalkyl groups had the tendency to enrich on the surface of the film. However, this enrichment of fluorine on the film surface was reduced after the introduction of HDDA, while increased with the addition of DDM. It was also found that the gel content, glass transition temperature (T_g), thermal stability, surface roughness, and modulus (G′, G?) of the fluorinated latex PSA were all increased with the introduction of HDDA. Nevertheless, opposite trends were observed for the latex after the addition of DDM. Finally, the effects of DDM and HDDA on the adhesive properties (i.e. loop tack, peel strength and shear strength) of the fluorinated latex PSA were also evaluated.     

高强度丙烯酸酯乳液型压敏胶的研制

采用多元丙烯酸酯单体共聚、尽可能降低乳化剂浓度、加入适量AA和HMAM作复合自交联剂等措施，制备具有高剥离强度的乳液型压敏胶粘剂。     

The effect of polymer molecular weight and crosslinking reactions on the adhesion properties of microsphere water-based acrylic pressure-sensitive adhesives

In this work, the effect of polymer molecular weight and crosslinking reactions on the end-use properties of the microsphere water-based acrylic pressure-sensitive adhesives (PSA) is presented. Polymer molecular weight and polymer microstructure were regulated using different chain transfer agent (CTA) concentrations and by addition of a diacrylic monomer (MM). The adhesion properties of the synthesized PSAs were characterized via measurements of tack, peel adhesion and shear strength. The results of experiments have shown that the kinetics of suspension polymerization is relatively independent on the amount of CTA and MM. The amount of gel phase in the adhesive was reduced with increasing amount of CTA agent, and gel phase amount may be considered as a function of polymer molecular weight. With a combination of CTA and MM was possible to regulate the amount of formed gel phase in the adhesive, as well sol phase molecular weight. All of the measured adhesion properties strongly depend on molecular weight of the synthesized polymer and on the amount of gel phase. For adhesives synthesized solely with addition of CTA, tack decreased with lower polymer molecular weight and consecutively also with lower amount of gel phase. The same trend was also observed for peel strength measurements, whereas a cohesive failure was observed for adhesives with low amount of gel phase. A maximum value for tack and shear strength was observed at 80 wt% of gel phase. In case of syntheses with a combination of CTA and MM (amount of gel phase in range from 70 to 80 wt%), tack values were distributed in quite narrow range. On the other hand, peel strength values decreased in comparison with adhesives synthesized only with CTA, regardless to the equal amount of gel phase. Poor shear strength was observed for all adhesives synthesized by combination of CTA and MM.