Polyvinyl Acetate and Vinyl Acetate-Ethylene Hybrid Adhesive: Synthesis, Characterization, and Properties

The goal is to develop a hybrid IPN network of polyvinyl acetate (PVAc) and ethylene-vinyl acetate (VAE). In this research work, the vinyl acetate (VAc)/ VAE hybrid emulsion and polyvinyl acetate emulsion (PVAc) were effectively synthesized. Emulsions with various characteristics have been developed by adjusting the weight ratios between the vinyl acetate monomer and the VAE component. The impacts on the mechanical, thermal, and physical properties of the films were investigated using tests for pencil hardness, tensile shear strength, pH, contact angle measurement, differential scanning calorimetry (DSC), and viscosity. When 5.0 weight percent VAE was added, the tensile shear strength in dry conditions decreased by 18.75% after a 24-hour bonding period, the heat resistance decreased by 26.29% (as per WATT 91) and the tensile shear strength decreased by approximately 36.52% in wet conditions (per EN 204). The pristine sample’s results were also confirmed by the contact angle test. The interpenetrating network (IPN) formation in hybrid PVAc emulsion as primary bonds does not directly attach to PVAc and VAE chains. The addition of VAE reduced the mechanical properties (at dry conditions) and heat resistance as per WATT 91. Contact angle analysis demonstrated that PVAc adhesives containing VAE had increased water resistance when compared to conventional PVA stabilised PVAc homopolymer-based adhesives. When compared to virgin PVAc Homo, the water resistance of the PVAc emulsion polymerization was enhanced by the addition of VAE.

Synthesis of Microcrystalline Cellulose—Polyvinyl Alcohol Stabilized Polyvinyl Acetate Emulsion

Polyvinyl alcohol (PVA) colloid stabilized Polyvinyl acetate (PVAc) based wood adhesive has poor performance in highly humid conditions. Currently, the addition of natural fillers in the wood adhesive is one of the most effective ways to enhance the performance of PVAc wood adhesive in highly moist conditions. Microcrystalline cellulose (MCC) are strong renewable, bio-based material and has great potential in a reinforcement of the polymeric matrix. Hence, the present work investigates the applicability of microcrystalline cellulose incorporated 3% and 5% in situ emulsion polymerization PVAc wood adhesives. Effect on physical, thermal and mechanical properties was studied by viscosity, pH, contact angle measurement, differential scanning calorimetry (DSC) and pencil hardness test of films. Emulsions with different proportions of MCC were prepared and the shear strength of the applied adhesive on wood was measured. The viscosity of the adhesives was increased by increasing the concentration of MCC. The mechanical properties like tensile strength of adhesives with MCC were measured by universal tensile machine (UTM). Thermal stability was studied by differential scanning calorimetry (DSC). The tensile shear strength demonstrates that MCC can improve bonding strength as compared to PVAc Homo based adhesive in the wet condition which was validated through a contact angle study. The hardness of PVAc films were also changed positively by the addition of MCC. Here, we studied the effect of the addition of different concentrations of MCC materials in situ polymerization of PVAc on their performance properties.

Polyurethane Hybrid-Based Wood Adhesive: Review

Based on commercially available polyvinyl alcohol (PVA) stabilised polyvinyl acetate (PVAc), emulsion adhesives are neither heat nor moisture-resistant and show weak strength at high relative humidity and high temperatures. Pre- or post-crosslinking is another method used to manufacture a conventional vinyl-based homopolymers or copolymers system with improved water resistance. Vinyl neodecanoate (VeoVa), N-methylolacrylamide (NMA), Methacrylamide, methacrylic acid (MAA), and other self-crosslinking comonomers are typically inserted to produce highly water-resistant vinyl based homopolymers or copolymers. Additionally, organic crosslinkers like glyoxal, glutaraldehyde, citric acid, tartaric acid, and the like, as well as inorganic crosslinkers like acidic metal salts like aluminium chloride, aluminium nitrate, boric acid, and the like, can be used to prepare the highly water-resistant vinyl based homopolymers or copolymers. It is also possible to combine the self-crosslinking comonomers with the organic crosslinkers. Recently, a different hybrid chemistry has been developed that improves lap shear strength, has outstanding water resistance, good durability, and doesn’t require any additional crosslinker agents. Two distinct polymers were combined to develop hybrid polymers. They usually involve mixing an organic polymer with a polymer. There are many capping agents that are used for polyurethanes to produce acrylics that are capped with polyurethane and used as an oligomer in PVAc wood glue. Here, in this paper, we reviewed the different hybrid chemistry based on polyurethane chemistry for wood bonding applications.

State of Research and Trends in the Development of Polyvinyl Acetate-Based Wood Adhesive

Synthetic wood adhesives, consisting of urea-formaldehyde resins (UF), phenol-formaldehyde resins (PF), melamine-formaldehyde resins (MF), and polyurethane resins, are widely used. For UF and MF, most investigations are concerned with reducing free formaldehyde content;for PF, most studies focused on finding new alternative chemicals to replace phenol. These adhesives come under the Carcinogenic, Mutagenic, and Reprotoxic chemicals (CMR) category. Due to global energy issues and dependency on petroleum sources, the focus has shifted to look for alternative and renewable raw material sources for wood adhesives. Conventionally available wood adhesives are polyvinyl alcohol (PVA) stabilized, with drawbacks like poor water resistance, poor heat resistance, low-temperature workability, and it’s based on petroleum resources. Polyvinyl acetate (PVAc) is non-resistant to moisture polymer, and if such adhesive joints are exploited in a moist environment, its strength substantially decreases. Sufficiently moisture-resistant adhesive joints are obtained by modifying PVAc dispersion with special compounds like reactive comonomer, Silanes, and modified PVA. To improve the workability at low temperature, Vinyl acetate (VAc) is copolymerized with specific comonomers like butyl acetate without affecting the performance properties. Here, we aim to present an overview of the research trend of PVAc-based adhesives in the wood industry. The review summarizes the current state of research PVAc-based adhesives.

<i>In Situ</i>Preparation of Core Shell-Polypyrrole /Poly (Acrylonitrile-Co-Vinyl Acetate) Nanoparticles and Their Nanofibers

Poly (acrylonitrile-co-vinyl acetate)/polypyrrole composite particles with uniform size and morphology have been synthesized using one-step polymerization that involves swelling and coating of polypyrrole (PPy) into P (AN-co-VAc) latex nanoparticles. As an initial stage, free radical copolymerization of acrylonitrile (AN) and vinyl acetate (VAc) was synthesized by emulsion polymerization using ammonium persulfate (APS) and dodecyl benzene sulfonic acid salt (DBSA) as a surfactant. P (AN-co-VAc)/PPy composites were obtained first time by in situ addition of the pyrrole into the reaction medium. The electrospun P (AN-co-VAc)/PPy nanofibers were obtained from the nanoparticles with better properties and the effect of PPy on the morphology of nanofibers was studied by scanning electron microscopy (SEM). High degree of homogeneity and molecular order induced by molecular dispersion of polypyrrole on copolymer matrix without phase separation improve the transport properties and stability of polypyrrole, which are critical for high-performance organic electronics.

低黏度高固含量聚醋酸乙烯酯乳液胶黏剂的制备及应用

聚醋酸乙烯酯(PVAc)具有固化速度快、初粘性好的优点,可作为胶黏剂或增稠剂应用于人造板工业。研究以醋酸乙烯酯(VAc)为单体、聚乙烯醇(PVA)为保护胶体,采用半连续乳液聚合法制备低黏度、高固含量聚醋酸乙烯酯乳液,并考察了PVA种类及其他聚合工艺因素对乳液性能的影响。结果表明:PVA种类对乳液性能影响较大。采用激光粒度分析仪、差示扫描量热仪(DSC)等对不同种类PVA合成的乳液进行表征表明:粒径随PVA醇解度增加而明显增大;PVA聚合度对乳液的玻璃化转变温度(Tg)影响较大。以PVA0599为保护胶体制备的PVAc乳液作为木材胶黏剂时,其拉伸剪切强度达8.62 MPa。

高性能水性木工胶粘剂的研制与性能表征

以丙烯酸丁酯、苯乙烯和其他功能单体为主要组分,采用半连续乳液聚合法,制备了一款低黏度苯丙共聚物乳液(SAEP)。通过正交试验法探索了聚乙烯醇种类、钙粉粒径以及固化剂用量对SAEP胶粘剂性能的影响。研究结果表明:采用聚乙烯醇BP17,钙粉粒径为12μm,w(固化剂)=13%时,SAEP胶粘剂的实际开放期能达到70 min以上;SAEP胶粘剂的最大干剪切强度为16.6 MPa,热水浸渍法测得的胶粘剂的湿剪切强度高达7.1 MPa,而反复煮沸法测得的剪切强度也可达5.5 MPa。在相同的配方条件下,与经典的市售EP4乳液相比,SAEP与EP4乳液配制的胶粘剂开放期(“胶液静态流动性判定法”)相当,最大干剪切强度几乎一致,但SAEP胶粘剂具有更高的湿剪切强度。

白乳胶中乙酸乙烯酯及乙酸乙酯的分析

为了同时测定烟用白乳胶中残留单体——乙酸乙烯酯及其杂质乙酸乙酯，考察了萃取溶剂种类和用量、萃取方式、破乳、盐析、色谱柱的极性及有关分析条件对测定结果的影响，建立了用水破乳、正己烷萃取、丁酸乙酯作内标、采用GC同时测定烟用白乳胶中乙酸乙烯酯和乙酸乙酯含量的方法。结果表明：方法的检测限低于0．9μg／g，回收率为77％～82％，RSD〈3％。该方法适合烟用白乳胶中乙酸乙烯酯及乙酸乙酯的定量分析。

乳液型膨胀防火涂料的研究(Ⅰ)——树脂基料对防火涂料性能的影响

研究了以乙丙、纯丙、苯丙和氯偏乳液为成膜基料的乳液型膨胀防火涂料的防火性能和机械性能，结果表明：氯偏乳液涂料具有较好的防火性能，但机械性能不够理想．在乙丙、纯丙和苯丙乳液体系中加入酚醛树脂或三聚氰胺甲醛树脂，可改善发泡层结构。

改性淀粉木材胶粘剂的制备及表征

以过硫酸铵为引发剂,以玉米淀粉、乙酸乙烯酯和丙烯酸丁酯为原料,制备改性淀粉木材胶粘剂,在单因素实验的基础上,进行L_(16)(4~5)正交实验,优化改性淀粉木材胶黏剂的制备条件。结果表明,最佳制备工艺参数为:引发剂浓度11 mmol/L,单体与淀粉质量比为1.0,反应温度70℃,单体乙酸乙烯酯和丙烯酸丁酯的质量比为3∶2,反应时间3 h。在此条件下,接枝率达91.3%,制备的改性淀粉木材胶粘剂性质较佳,各项指标均达到聚乙酸乙烯酯木材胶粘剂化工行业标准HG/T 2727—2010。

PVAc乳胶/改性大豆分离蛋白共混胶黏剂的制备及性能

针对大豆蛋白胶黏剂耐水性差的缺点,用尿素初步改性大豆分离蛋白(SPI),然后与白乳胶(PVAc)共混合成了共混改性大豆分离蛋白胶黏剂。采用正交实验方法考察了大豆蛋白胶与白乳胶质量比、共混时间、交联剂质量分数、交联时间对大豆蛋白胶黏剂剪切粘接强度的影响,确定了优化配比及制备工艺条件,并在此基础上采用正交试验优化了热压参数。结果表明:大豆蛋白胶与白乳胶质量比10∶1,共混时间1h,交联剂质量分数1.0%,交联时间1.5h,热压温度120℃,热压压强1.2MPa,热压时间2min/mm,涂胶量250g/m2时,测得胶黏剂的干态剪切粘接强度为2.01MPa,按照Ⅰ类胶合板标准测得湿态剪切粘接强度为1.04MPa,并对优化配方进行了结构与性能分析。

聚醋酸乙烯酯乳液胶粘剂的改性研究进展

介绍了聚醋酸乙烯酯(PVAc)乳液的特点,并对醋酸乙烯胶粘剂的改性研究的最新状况进行了综述。

NIR光谱法快速测定烟用白乳胶中的乙酸乙烯酯

为了快速分析烟用白乳胶中乙酸乙烯酯的含量,利用近红外(NIR)漫反射光谱仪对70个烟用白乳胶样品进行了扫描,采用顶空气相色谱法法测定了其乙酸乙烯酯含量,根据消除常数法对光谱进行预处理和偏最小二乘法数据拟合,建立了烟用白乳胶中乙酸乙烯酯的NIR预测模型,并对这些模型进行了外部验证。结果表明,乙酸乙烯酯的预测值与GC测定值的平均相对偏差均在5%以内,RSD均<4%。该模型适合用于批量烟用白乳胶中乙酸乙烯酯的快速测定。

胶合板用VAc-BA-MMA-AA四元共聚乳液胶黏剂的制备与表征

为了提高聚醋酸乙烯酯乳液胶黏剂的胶合强度和耐水性能,以醋酸乙烯酯(VAc)、丙烯酸丁酯(BA)、甲基丙烯酸甲酯(MMA)和丙烯酸(AA)为单体原料,采用半连续乳液聚合方法制备胶合板用VAc-BA-MMA-AA四元共聚乳液胶黏剂。利用傅里叶变换红外光谱仪、扫描电镜、热重分析仪等测试手段对乳胶膜的化学结构、表面形貌和热稳定性等进行了分析。结果表明:与VAc均聚乳液相比,四元共聚乳液具有较高的热稳定性,乳胶膜的表面形貌更加规整;四元共聚乳液胶合的杨木三层胶合板的胶合强度达到3.16 MPa,耐水性比用均聚乳液胶合时提高3倍,达到Ⅱ类胶合板的性能标准。

聚醋酸乙烯酯乳液胶粘剂的改性研究

介绍了醋酸乙烯酯-丙烯酸酯多元共聚乳液的合成工艺,讨论了单体组成、乳化剂组成、反应温度等对乳液性能的影响。

BA-VAC共聚乳液胶及其对木材的冷胶合

通过对丙烯酸酯 醋酸乙烯酯共聚乳液胶合成工艺研究 ,分析讨论了各因素对乳液胶质量的影响 ,选择了最佳工艺条件 (聚合温度为 85℃ ,聚合时间 4h ,引发剂 0 4%～0 6 % )及木材冷胶合调制配方。结果表明 :该乳液胶使用方便 ,成膜性好 ,胶合适用范围广 ,对木材冷压胶合后的板材强度可达Ⅰ类胶合板要求 (>0 96 5MPa)。表 7参

D3级耐水聚醋酸乙烯酯乳液胶粘剂的合成

以双氧水（H2O2）/酒石酸（TA）为引发剂、N-羟甲基丙烯酰胺（NMA）和醋酸乙烯酯（VAc）为共聚单体,采用半连续滴加法制备出木材粘接用耐水PVAc（聚醋酸乙烯酯）乳液胶粘剂。研究结果表明：VAc/NMA共聚乳液的粒子呈球状结构,其粒径为700~800 nm;该共聚乳液属于假塑性流体,其常温储存稳定性良好,受热储存时的黏度急剧增大;由该共聚乳液制成的木-木胶接件之干态、湿态剪切强度均随NMA掺量增加而有所提高,当w（NMA）≥2%（相对于共聚乳液总质量而言）时,其浸湿再干燥后的干态剪切强度（均超过8 MPa）达到EN 204—2001标准中D3级指标要求。

水基纸塑复合胶粘剂(BST-7)的研制

研究了水基纸塑复合胶粘剂（ＢＳＴ－７）的配方和性能，讨论了乙烯－醋酸乙烯乳液（ＶＡＥ）品种、增粘树脂品种和用量以及软化剂用量等因素对胶粘剂粘度、胶膜透明度、剥离强度的影响。

乳液型胶粘剂研究进展

综述了近年来乳液型胶粘剂的研究进展,包括组成、合成工艺、性能及应用等。讨论了通过改变单体组成或引发体系、改进聚合工艺、通过共混或化学结合引入其他聚合物的方式改进乳液型胶粘剂性能的方法。展望了未来乳液型胶粘剂的应用和发展前景。

改性淀粉接枝共聚醋丙乳液的制备与表征

以木薯淀粉为主要原料,通过氧化改性使其分子结构发生变化,再与醋酸乙烯酯、丙烯酸丁酯和N-羟甲基丙烯酸酰胺等单体发生接枝共聚反应,制备一种低成本高性能的快速固化乳液胶黏剂,制备的接枝共聚乳液胶黏剂各项性能指标满足国家标准要求。研究了氧化木薯淀粉制备工艺和改性淀粉接枝共聚醋丙乳液工艺,通过试验表明,使用改性淀粉接枝共聚乳液压制的杨木板材,其干/湿状剪切强度均高于行业标准要求,同时在相同工艺条件下使用醋丙乳液压制的杨木板材,接枝共聚效果明显。采用傅里叶红外光谱仪和差示扫描量热仪对制备的接枝共聚乳液的聚合情况和玻璃化转变温度进行分析,结果表明:改性淀粉醋丙乳液在1 735 cm-1处出现酯基CO的强振动吸收峰,在3 483 cm-1处出现了明显的丙烯酰胺中的N—H伸缩振动峰,且在1 155和1078 cm-1等处出现明显的淀粉特征峰,说明该共聚物既有聚合单体特征峰和淀粉特征峰,又有共聚后出现的酯基特征峰,表明木薯淀粉经过氧化改性后与各单体之间发生聚合反应,且接枝共聚乳液的最低成膜温度为18.04℃,表明接枝共聚后的乳液可在常温下快速固化。