Emulsion Semi-Batch Terpolymerization Process Using Hybrid Emulsifiers for Synthesizing New Emulsion Pressure Sensitive Adhesives (EPSAs)

In order to obtain a suitable formulation of designing direct synthesis of acrylic latexes to be used as emulsion pressure sensitive adhesives (EPSA), having high shear resistance together with high peel strength and tack, free radical emulsion polymerization of hard monomers, such as styrene (St), vinyl acetate monomer (VAM), methyl methacrylate (MMA) and butyl methacrylate (BMA), and soft monomers, butyl acrylate (BA) and 2-ethylhexyl acrylate (2-EHA) along with multifunctional monomers, namely acrylic acid (AA), were carried out. The effect of the type of hard and soft acrylic monomers, the type and level of emulsifiers, and the initiator concentration on the emulsion polymer stability and final properties of the EPSA were investigated. The results obtained showed an optimized composition. This composition led to a significant increase in shear strength and peel strength to 909 kPa and 0.45 N/mm, respectively, while the synthesized PSA was still too tacky, 5.5 cm, according to adhesion performance testing. For making this successful balance of the conflicting adhesion properties of PSA, a series of anionic and nonionic emulsifiers were investigated. It was interestingly found out that the hybrid emulsifiers (anionic coupling with nonionic) with the optimized compositions could enhance the stability of the emulsion system and improve the properties of PSA compared with the mono-emulsifier. We also tried to adjust the initiator concentration with the level of the optimized hybrid emulsifier, polyoxyethylene alkyl phenyl ether (K30), dioctyl sulfosuccinate (DOSS), and sodium vinyl sulfonate (SVS) with the ratio 2:1:1, resulting in a highly preferred proportion of the 0.5 part of the initiator versus 1.25 parts of the hybrid emulsifier in terms of the total weight of the monomers.     

Antimicrobial activity,effects on Streptococcus mutans biofilm and interfacial bonding of adhesive systems with and without antibacterial agent

ObjectivesThis study evaluated the antimicrobial activity (by agar disk diffusion test, AD), viability of S. mutans biofilm (VB), and effect on resin-dentin interface (RDI) of six adhesive systems.MethodsThree adhesives containing antibacterial components (Gluma 2Bond (G2B)/glutaraldehyde, Clearfil SE Protect (CSP)/MDPB and Peak Universal Bond (PUB)/chlorhexidine) and the corresponding adhesives with similar composition, but without antibacterial agents (Gluma Comfort Bond, GCB; Clearfil SE Bond, CSB and Peak LC Bond, PLB) were evaluated. AD was determined measuring the extent of halo formation following application of adhesives and control groups (light cured or not) to cultures of four strict anaerobic and four facultative bacteria. For VB, a UA159 biofilm was grown on adhesive-coated hydroxyapatite discs for five days, collected and processed to count the number of viable cells. For RDI analysis, adhesives were applied according to manufacturers' recommendations and teeth were restored with resin composite, sectioned to obtain bonded slices and visualized by SEM.ResultsAn inhibition halo was observed for G2B (strict anaerobic/light cured and not light cured), CSP (strict anaerobic and facultative/light cured and not light cured) and PUB (strict anaerobic and facultative/not light cured). PUB when light cured produced an inhibition halo on L. casei and S. mutans only. G2B and CSP significantly reduced the viability of S. mutans. Adhesives containing antimicrobial compounds had no detectable effect on RDI.ConclusionThe MDPB-containing bonding agent showed better results of inhibition for all oral pathogens tested and a decrease of viability of Streptococcus mutans biofilm, among the adhesives tested.     

UV-固化胶黏剂收缩率的研究

UV-固化胶黏剂固化过程中发生的体积收缩,是影响胶黏剂粘接性能的重要因素．本文分析讨论了UV-固化胶黏剂收缩率的产生原因、影响因素、研究方法,收缩率和收缩应力的关系,以期针对不同的使用需求,找到降低或消除收缩率的有效方法。     

酸性溶剂对水热法合成 ZrW2 O8粉体形貌的影响

以水热法制备负热膨胀性ZrW2 O8粉体,考察酸性溶剂对粉体的合成及性质的影响。对其前驱体进行热重-差热分析,以X射线粉末衍射,扫描电子显微镜对产物结构及形貌进行表征。结果表明当加入的溶剂为HCl 和HNO3混合液时,能够获得结晶良好,纯度高的纳米ZrW2 O8粉体。但随着HNO3量的不断增加,颗粒尺寸逐渐减小,颗粒的形状从棒状转变为类球形。通过原位X射线衍射分析,表明所合成的粉体具有良好的负热膨胀性能。     

Influence of the Chemical Structure of Urethane-Based Thickeners on the Properties of Waterborne Polyurethane Adhesives

To analyse the parameters that influence the thickening mechanism of waterborne polyurethane adhesives, different hydrophobically modified ethoxylated polyurethane based thickeners (HEUR) were used. The thickeners were characterized by proton nuclear magnetic resonance (¹H-NMR) and gel permeation chromatography (GPC). The thickened adhesive solutions were characterized by flow rheology, pH, particle size measurements, solids content, and confocal microscopy. The thickened solid adhesive films were characterized by ATR-IR spectroscopy, parallel plate rheology, dynamic mechanical thermal analysis (DMTA), and differential scanning calorimetry (DSC). The adhesion was measured by a T-peel test of leather/polyurethane adhesive/SBR rubber joints. The addition of the different HEUR thickeners increased the viscosity of the polyurethane dispersion to different degrees. Furthermore, whereas the un-thickened polyurethane dispersion showed a Newtonian rheological behaviour, a shear-thinning rheological behaviour was observed in the thickened dispersions due to thickener-thickener and polyurethane-thickener interactions. The viscosity of the thickened polyurethane adhesive solutions increased with the degree of hydrophobicity and the molecular weight of the thickener. The addition of different thickeners increased the pH values due to the ionic adsorption, which is one of the interactions that contribute to the thickening mechanism of the polyurethane thickeners, besides hydrogen bonding and van der Waals hydrophobic interactions (micelles). The entanglement of the thickened polyurethane adhesives was studied by confocal microscopy. Although the addition of the thickeners did not affect the thermal properties of the polyurethanes, the T-peel strength of leather/adhesive/SBR rubber joints was influenced by the rheological properties of the thickened adhesives.     

碳纤维片材加固胶黏剂的工艺性能改进研究

碳纤维片材加固胶黏剂已广泛应用于混凝土结构加固及改造领域,但对其工艺性能的改进研究一直未能引起足够的重视。本文研究了改性胺类固化剂对环氧树脂类碳纤维片材加固胶黏剂适用期的影响,同时也对触变剂进行了探讨,并提出了判定胶黏剂浸润性的方法。采用自制的固化剂复配得到了适用于不同季节使用的冬夏配方,工艺性能良好。     

Investigation of the Influence of Fillers on the Properties of Poly(vinyl acetate) Adhesives

The properties of poly(vinyl acetate) compositions prepared as potential wood adhesives were investigated. The paper presents the results of the influence of various kinds of inorganic fillers based on calcium carbonate and alumino-silicate and an organic filler, starch, on the adhesive composition properties. The comparison among rheological behavior of the adhesive dispersions concerning the specific role of fillers were made. Mechanical and relaxation properties of the adhesive films could reveal the effect of filler characteristics on the polymer matrix. The significant influences of particle size distribution and specific surface area on the poly(vinyl acetate) adhesive composition were determined, along with other filler characteristics.     

Investigation of the Influence of Fillers on the Properties of Poly(vinyl acetate) Adhesives

The properties of poly(vinyl acetate) compositions prepared as potential wood adhesives were investigated. The paper presents the results of the influence of various kinds of inorganic fillers based on calcium carbonate and alumino-silicate and an organic filler, starch, on the adhesive composition properties. The comparison among rheological behavior of the adhesive dispersions concerning the specific role of fillers were made. Mechanical and relaxation properties of the adhesive films could reveal the effect of filler characteristics on the polymer matrix. The significant influences of particle size distribution and specific surface area on the poly(vinyl acetate) adhesive composition were determined, along with other filler characteristics.     

The Effect of Nanoclay on Melamine-Urea-Formaldehyde Wood Adhesives

Abstract

In this work it has been shown that the addition of small percentages of Na⁺-montmorillonite (Na-MMT) and organic modified-montmorillonite (O-MMT) nanoclay to thermosetting melamine-urea-formaldehyde (MUF) resins appeared to improve, considerably, their performance as adhesives for wood particleboard. X-ray diffraction (XRD) studies indicated that Na-MMT when mixed in small proportions, loses the periodic atomic structure during the curing of MUF resins. This can be interpreted as becoming exfoliated under such conditions. Thermomechanical analysis (TMA) on laboratory MUF-bonded particleboard indicated that small percentages of Na-MMT and O-MMT improved the internal bond strength imparted by the MUF adhesive to the panel, when tested dry and also, more importantly, when tested after 2 h of boiling. The increase in water resistance of the MUF-bonded panel was particularly noticeable. Furthermore, the addition of Na-MMT was shown to increase considerably the resistance of the MUF resin to abrasion. This is important from a wood surface finish point of view.     

混合溶剂法生产6-APA中溶剂回收的工艺模拟

萃取直通法生产6-APA会产生大量含有机溶剂的废水。利用Aspen Plus软件,采用VLLE平衡和NRTL方程,模拟计算了6-APA废水中醋酸正丁酯和正丁醇混合溶剂的回收工艺。考察了理论塔板数、气相采出量等操作参数对产品纯度的影响,获得了优化的模拟条件。结果表明,采用20块理论板,塔顶气相采出量为2600 kg/h时,经分相后得到的有机相产品纯度约为90.4%,其中醋酸正丁酯和正丁醇基本被完全回收,为6-APA工艺废水的处理与利用提供了参考。     

木质生物质在不同溶剂作用下的液化反应研究进展

生物质液化技术可将低品位的固体生物质转化成高品位的液体燃料或化学品,是生物质高效利用的主要方式。首先分析了不同生物质组分液化过程中的机理,在此基础上,以木质生物质液化溶剂的选择为出发点,讨论了水、醇类以及混合溶剂作用下的液化反应,同时比较了催化剂对液化过程及产品组成的影响,指出醇类溶剂液化在液化油产品质量、液化过程分子结构的调控方面具有较大的优势,在高品质液化油、燃油添加剂合成等方面具有较高的应用前景。     

几种红外隐身涂料黏合剂的性能研究

将涂料或树脂在试样板上涂膜,利用傅立叶红外光谱仪分别对液态、固态酚醛树脂、聚氨酯树脂以及Kraton树脂进行红外透过性和成膜性能的研究。发现固态酚醛树脂的成膜性能较差,聚氨酯树脂和液态酚醛树脂的成膜性能较好,但红外透过性一般,Kraton树脂的红外透过性较好,但成膜性能较差,聚氨酯树脂作为红外隐身涂料黏合剂的实用性较大。     

A Review of Certain Recent Work on the Durability of Aluminium Alloy Bonded with Epoxide and Phenolic Adhesives

Single lap joints of aluminium alloy, bonded with a number of structural adhesives, have been aged at 100% or 50% relative humidity (r.h.) at 50°C for up to 10000 hours. The adhesives used have included a simple epoxide and some modified phenolics and epoxides. Whilst joints are not significantly weakened on exposure at 50% r.h., significant weakening occurs at 100% rh. There is an initial fall in strength in the early stages of exposure, but after this period joints remain fairly stable, retaining approximately 40-60% of the strengths they had before exposure. Water diffusion coefficients in the adhesives have been obtained from experiments on the mass uptake of water by films of the adhesives. Water concentration profiles and overall levels of water in adhesive joints have been calculated from diffusion coefficients, and these show that the initial fall in strength is controlled by water diffusing through the adhesive layer. Joint strengths recover significantly when they are dried out. The behaviour of joints can be interpreted by there being ion-pairs at the interface. Water reduces the interionic force by raising the permittivity of the surroundings, and this is reversed when the water is removed.     

A Review of Certain Recent Work on the Durability of Aluminium Alloy Bonded with Epoxide and Phenolic Adhesives

Single lap joints of aluminium alloy, bonded with a number of structural adhesives, have been aged at 100% or 50% relative humidity (r.h.) at 50°C for up to 10000 hours. The adhesives used have included a simple epoxide and some modified phenolics and epoxides. Whilst joints are not significantly weakened on exposure at 50% r.h., significant weakening occurs at 100% rh. There is an initial fall in strength in the early stages of exposure, but after this period joints remain fairly stable, retaining approximately 40–60% of the strengths they had before exposure. Water diffusion coefficients in the adhesives have been obtained from experiments on the mass uptake of water by films of the adhesives. Water concentration profiles and overall levels of water in adhesive joints have been calculated from diffusion coefficients, and these show that the initial fall in strength is controlled by water diffusing through the adhesive layer. Joint strengths recover significantly when they are dried out. The behaviour of joints can be interpreted by there being ion-pairs at the interface. Water reduces the interionic force by raising the permittivity of the surroundings, and this is reversed when the water is removed.     

Synthesis and Characterization of Water-Borne Adhesives Based on 2-Ethylhexylacrylate-butylacrylate Copolymers Functionalized with Acrylic Acid

ABSTRACT

A series of copolymers, based on 2-ethylhexylacrylate (2-EHA) and butylacrylate (BuA), and functionalized with small amounts of acrylic acid (AA) were synthesized by emulsion polymerization techniques and monodisperse latexes were obtained. Their average particle size and particle size distribution were determined by quasi-elastic light scattering and confirmed by transmission electron microscopy. The change in the adhesive properties (peel, shear, and tack) as a function of 2-EHA/BuA ratio was studied. An optimal balance between these three properties was determined at a 2-EHA/BuA ratio 10/90 wt/wt. The influence of the functionalization of these copolymers with AA was also evaluated when the comonomers ratio was kept constant. Good results were found at an AA content of 1 wt%.     

杂交狼尾草碱预处理研究

采用不同碱对杂交狼尾草进行预处理,探讨碱预处理前后杂交狼尾草主要成分含量的变化。利用固态化学预处理方法,研究了氢氧化钠、氢氧化钙、氨水、尿素对杂交狼尾草的预处理。并采用范式纤维洗涤法对碱预处理后杂交狼尾草的纤维素、半纤维素、木质素含量进行了分析。结果表明,碱预处理后的酸性洗涤纤维、中性洗涤纤维、半纤维素含量明显比预处理之前的低。Na OH预处理,Na OH质量分数为8%时,木质素含量最低,为5.28%;Ca(OH)2预处理,Ca(OH)2质量分数为2%时,木质素含量最低,为5.69%;氨水预处理,氨水质量分数为8%时,可使木质素含量最低,为5.12%;尿素预处理,尿素质量分数为6%时木质素含量最低,为4.38%。显然,采用6%尿素处理得到的木质素含量较低。     

Effect of a Gradient in Viscoelastic Properties on the Debonding Mechanisms of Soft Adhesives

The effect of a composition gradient along the thickness in soft adhesive films was investigated. The adhesion properties of bilayer films made from acrylic solutions, one layer being more cohesive and the other more dissipative, were studied by performing probe tack experiments. To understand the mechanisms that determine the bulk and the interfacial contributions to the debonding, tests on different surfaces were carried out. The results show that the presence of a composition gradient can enhance the adhesive properties, particularly on a low-energy surface such as polyethylene. On steel, the presence of the thin layer of a more elastic adhesive in contact with the adherent can influence significantly the debonding mechanism, transforming the fracture from cohesive to adhesive.     

Effect of a Gradient in Viscoelastic Properties on the Debonding Mechanisms of Soft Adhesives

The effect of a composition gradient along the thickness in soft adhesive films was investigated. The adhesion properties of bilayer films made from acrylic solutions, one layer being more cohesive and the other more dissipative, were studied by performing probe tack experiments. To understand the mechanisms that determine the bulk and the interfacial contributions to the debonding, tests on different surfaces were carried out. The results show that the presence of a composition gradient can enhance the adhesive properties, particularly on a low-energy surface such as polyethylene. On steel, the presence of the thin layer of a more elastic adhesive in contact with the adherent can influence significantly the debonding mechanism, transforming the fracture from cohesive to adhesive.     

Controlling Adhesion of Orthodontic Adhesives Through Adjustment of the Interphase Mechanical Properties

Adhesives for ceramic orthodontic brackets are so strong that instances of enamel fracture and bracket fracture have occurred during removal. Our approach to minimize the potential enamel damage was to modify the mechanical properties of the adhesive, a BIS GMA-silica composite, by use of diethyl phthalate which is a common plasticizer. The plasticizer, used in amounts up to 20% of the adhesive weight, significantly decreases the adhesive modulus and tensile strength. One objective of this research is to evaluate plasticizer stability in the adhesive via functional testing in a simulated oral environment. A second objective was to simulate, by use of finite element analysis, clinical loading conditions during orthodontic treatment and removal. The finite element analysis determined the changes in computed stresses due to plasticization. After 25 days in an artificial saliva solution held at 60°C, the bracket removal torque was lower for the 10% plasticized adhesive group than that for the non-plasticized group. The 3-D linear elastic finite element anlaysis found that plasticization should not lead to premature failure when typical treatment loadings were applied. The torsional loading conditions simulating bracket removal reported peak stresses in excess of the plasticized adhesive tensile strength in the corner regions. Thus, modelling of the adhesive as a layer with distinct mechanical properties appears reasonable.