Adhesion properties of soy protein adhesives enhanced by biomass lignin

Soy protein adhesives have great potential as sustainable eco-friendly adhesives. However, low adhesion under wet conditions hinders its applications. The objective of this research was to enhance the water resistance of soy protein adhesives. The focus of this research was to understand the effect of protein to lignin ratio and lignin particle size i.e. large (35.66 μm), medium (19.13 μm), and small (10.26 μm) on the adhesion performance of soy protein adhesives as well as to characterize its rheological and thermal properties. Results showed that the lignin particle size and the protein to lignin ratio greatly affected the adhesion performance of soy protein adhesives. The addition of lignin slightly increased the viscosity, spreadability, and thermostability of soy protein adhesives. The wet strength of soy protein adhesives increased as lignin particle size decreased. Soy protein mixed with small size lignin at a protein to lignin ratio of 10:2 (w/w) at 12% concentration presented the lowest contact angle and the highest wet adhesion strength of 4.66 MPa., which is 53.3% higher than that of 10% pure soy protein adhesive. The improvements in adhesion performance and physicochemical properties of soy protein adhesives by lignin were ascribed to the interactions between protein and lignin. Lignin with smaller particle size increased the wet shear strength of soy protein adhesives because a larger surface area of lignin was available to interact with the protein.     

Recycling of rigid polyurethane foam: Micro-milled powder used as active filler in polyurethane adhesives

Rigid polyurethane (PUR) foams are widely used as heat insulation material in construction industry or for electronic appliances manufacturing. After finishing their life-time, it is necessary to eliminate foam wastes. The aim of this study was to prepare a pair of industrial PUR adhesives of medium viscosity containing recycled rigid PUR foam. Three methods of milling were tested: knife-milling, two-roll milling, and ball-milling. Only two-roll milling gives the PUR micro-powder usable for following adhesives modification. The micro-powder was used as passive filler in PUR adhesives and potential reactivity for polyol pack replacement was studied. Hydroxyl and amine numbers were determined in mixture with virgin polyol. One-component PUR prepolymer adhesive was prepared using various dosages of the micro powder and the tensile strength of bound wood was measured. As additional parameters, also free film adhesive mechanical parameters were tested and particle size distribution of the micro powder was analyzed. Two adhesive formulations were prepared for independent evaluation of the micro powder reactivity. The results showed growing of the mechanical strength of wood bonding with growing dosage of the micro powder.     

Influence of humidity and frequency on the energy dissipation in wood adhesives

In this paper, the frequency dependent energy dissipation of typical wood adhesive under cyclic stress was studied on film adhesive samples. Three moisture-curing one component polyurethane (1C-PUR) adhesives with relative ductile behavior, one melamine formaldehyde (MF) and one phenol formaldehyde resorcinol (PRF) adhesives both with a more brittle behavior were prepared to study the viscoelastic properties at different relative air humidities (RH). Dynamic Mechanical Analysis (DMA) in tensile mode was used to determine loss modulus, storage modulus and loss factor Tan Delta on free standing adhesive films. It has been shown that 1C-PUR adhesives dissipate proportional more of the stored energy than MF and PRF adhesives. Humidity increased the dissipative processes in all PUR adhesives, especially in the polyamide fiber filled adhesive. PRF adhesive is less influenced by humidity. While for all other tested adhesives the dissipative processes generally increased with higher humidity, humidity decreased the damping of the investigated MF adhesive. The influence of the frequency on the energy dissipation is low for all tested adhesives in the investigated frequency range. Further fatigue tests with glued wood samples are needed to confirm the results observed on the free standing adhesive films.     

Effect of using sepiolite silicate + fumed silica mixtures as fillers on the characteristics of solvent-based polyurethane adhesives

Abstract —Both fumed silica and sepiolite have been used as a filler of polyurethane (PU) adhesives. Although effective, the small particle size and the relative high cost of fumed silica are limitations in some applications. Sepiolite is cheaper than fumed silica, but its relatively large particle size facilitates its settling from the adhesive solutions. In this study, the usefulness of using sepiolite + fumed silica mixtures as a filler in solvent-based PU adhesives is demonstrated. The rheological and adhesion properties of the PU adhesive solutions and the rheological and mechanical properties of the PU films (without solvent) were studied. SEM micrographs of PU films showed the morphology and compatibility of the fillers with the PU matrix. The use of sepiolite + fumed silica mixtures inhibited the settlement of the filler from the PU adhesive solutions, increased both the storage and the loss moduli, and improved the rheological and mechanical properties of the PU. On the other hand, the green (immediate) T-peel strengths of roughened styrene-butadiene rubber/PU adhesive joints and plasticized PVC/PU adhesive joints were greatly improved in filled PU adhesives. The effects produced by using fumed silica alone or sepiolite + fumed silica mixtures were very similar, although in general, somewhat more marked in fumed silica-filled PU.     

Synthesis and characterization of waterborne polyurethane adhesives containing different amount of ionic groups (I)

A series of waterborne polyurethanes (WBPU) containing different amount of 2,2‐bis(hydroxymethyl) propionic acid (DMPA) were synthesized using prepolymer mixing process. Relationships between the DMPA content and physical, mechanical, and thermal properties as well as adhesive behavior at different condition were investigated. Stable aqueous dispersions of WBPU were obtained when the DMPA content was more than 10 mol %. At higher DMPA content, the particle size of the WBPU dispersion was lower but the viscosity of the dispersion was higher. Water swelling and tensile strength of the films increased with increasing of DMPA content. The optimum adhesive strength of WBPU adhesives was found to be depended on the DMPA content, pressing temperature, and pressure on adhesion process. The adhesive strength of WBPU adhesives increased with increasing DMPA content. The optimum pressing temperature decreased with increasing DMPA content. The adhesive strength of WBPU adhesives increased with increasing pressure up to 15 kg f/cm² and then leveled off. The optimum pressing temperature of WBPU adhesives samples containing 24.02, 22.05, and 17.05 mol % DMPA was about 100, 120, and 140°C, respectively. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 5684–5691, 2006     

Strength distribution of particles under compression

From time immemorial people dealt with size reduction processes (mill, mineral liberation, etc.). As time has passed industrial units for comminution processes have become larger and more sophisticated, but still they perform with low efficiencies [1], [2] and [3]. The strength of a particle is one of its most crucial characteristics due to the mechanical stresses experienced by each particle within an industrial unit. This is because the final size of particles is mostly dependant on the strength distribution of the raw material [4]. In this present study, the ability of a number of statistical formulations to accurately describe the strength distribution of particles was examined. Additionally, selected equations were analyzed and a general expression including the effect of the material and particle size was developed. A number of approaches to define particle strength were considered, and strength in terms of crushing force was chosen. Particle strength in terms of force and in terms of energy was also compared and found to be size independent. Finally, particle strength in terms of stress was examined and compared to the particle strength in terms of force.The ability to describe the compression strength distribution will significantly improve the accuracy of the comminution processes simulation, design and optimization.     

Evaluation of block shear properties of selected extreme‐pH structural adhesives by short‐term exposure test

Nine structural adhesives with varying pH were selected to examine the effect of adhesive pH on wood–adhesive bond quality. The adhesives evaluated included four highly alkaline phenol–formaldehyde, one intermediate pH phenol–resorcinol–formaldehyde, two acidic melamine–urea–formaldehyde, and two acidic melamine–formaldehyde resins. Block shear specimens were prepared using Douglas‐fir and black spruce wood. The adhesive performance was evaluated by measuring the shear properties (strength and wood failure) of the specimens tested at the dry and vacuum–pressure–redry (VPD) conditions. Adhesive pH, test condition, and wood species showed significant effects on shear properties. The different adhesives performed differently at the dry and VPD conditions. The high‐pH adhesives (phenol–formaldehyde and phenol–resorcinol–formaldehyde) showed similar high wood failures at both test conditions and performed better than the low‐pH adhesives (melamine–formaldehyde and melamine–urea–formaldehyde), especially after the VPD conditioning. The low‐pH adhesives showed high wood failure at the dry condition, but wood failure decreased significantly after VPD conditioning for both species, indicating that the low‐pH adhesives were less durable than the high‐pH adhesives. High‐pH adhesives did not have a negative impact on the strength of the bonded specimens. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

工业木质素在木材胶粘剂中应用的研究进展

工业木质素应用于木材胶粘剂的研究历史很长,但目前仍停留在小试或中试阶段,并没有工业化生产。结合木质素的基本结构和化学改性,综述了其应用于酚醛树脂、脲醛树脂、三聚氰氨甲醛树脂和聚氨酯胶粘剂等常用木材胶粘剂及环保木材胶粘剂中的现状。指出了工业木质素应用于木材胶粘剂未来研究的方向。引用文献26篇。     

Rheology and machining performance of waterborne biopolymer labelling adhesives

Machining performance is one of the most important features of waterborne biopolymer labelling adhesives. Various deformation processes on the labelling machine have been analysed in relation to the rheology characteristics of adhesive materials. It has been shown that satisfactory machining performance requires adhesive materials to have particular properties under both shear and extensional deformations. Flow behaviours of commercial labelling adhesive products were tested over a very wide range of shear rate. Time dependences of the apparent shear viscosity were examined at selected shear rates. An adhesive with a smooth flow behaviour and only slight time dependence tends to perform better on the labelling machine. Results found in this work can be used as guide for rheology assessment in the development of new waterborne biopolymer adhesives.     

微胶囊技术在胶黏剂中的应用

概述了微胶囊的发展历程和结构特征,综述了微胶囊的制备原理及方法,对三种制备微胶囊的方法-化学法、相分离法和物理法进行了比较.介绍了微胶囊的应用及其最新研究进展.用在胶黏剂领域的微胶囊技术进步很快,特别在微胶囊的设计方面,现在可以根据用途提供种类繁多的胶黏剂,以前无法解决的问题,现在通过微胶囊结构的设计,可以得到圆满解决.讨论了微胶囊制备技术在胶黏剂领域的应用,主要探讨了微胶囊厌氧胶黏剂、微胶囊压敏胶黏剂和微胶囊环氧树脂胶黏剂的制备和应用,展望了微胶囊胶黏剂的应用前景.     

可生物降解胶粘剂的研究进展

可生物降解胶粘剂作为一种环保型胶粘剂,将是胶粘剂工业的发展方向之一。重点介绍了聚酯类、聚氨酯(PU)类和聚酰胺(PA)类等可生物降解胶粘剂的发展现状,对影响胶粘剂生物降解的因素和评价方法进行了阐述,并对可生物降解胶粘剂的发展方向作了展望。     

The influence of type and concentration of inorganic pigments on the polyurethane adhesive properties and adhesion of laminates

The introduction of white pigments into an adhesive layer is the new and economically favourable method of obtaining white laminates. In this work studies of the influence of the type and concentration of white pigments in polyurethane adhesive layer of laminates on their whiteness (opacity) and tensile strength are presented. The pigments used were titanium dioxide, zinc white and lithopone. They were added to a polyurethane adhesive in concentrations of 10–20 wt%. In order to determine the applicability of the described solution on an industrial scale, studies of viscosity, rheology and DSC thermograms of adhesives were performed as well as Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) of whitened laminates and leak testing of packaging formed from these laminates. Moreover the morphology of used pigments was analysed by measuring average particle size distribution on a laser diffraction Mastersizer 2000 and on scanning electron microscopy.     

Adhesive distribution related to mechanical performance of high density wood fibre board

In a full-scale mill experiment two groups of high density wood fibre boards were produced. While one group was bonded with a standard melamine reinforced urea-formaldehyde adhesive, a second group was bonded with a modified adhesive yielding systematically improved board properties at identical amounts of adhesive applied. By means of a novel fluorescence-microscopic method using the dye Acriflavine to colour the cured adhesive after board production, adhesive distribution within the industrial produced boards was evaluated and quantified. Very clear differences in the size distribution of the two adhesives were found, leading to the conclusion that a relationship exists between adhesive distribution and mechanical board performance.     

Microencapsulated markers for damage detection in adhesive joints

ABSTRACT

The durability of adhesive bonds is not only affected by the quality of the bonding procedure but also by aging processes which influence the bond performance negatively on a long time scale. Especially the building industry, where safety related joints are increasingly boned with adhesives, demands new quality assurance methods. Therefore, appropriate monitoring techniques for developing cracks or critical stresses are essential.

A new approach for in situ monitoring of transparent/opaque adhesives will be presented in this paper. Microcapsules, filled with special dyes, are embedded into adhesive systems. Upon breakage through cracks or exceedance of certain stress levels within the adhesive seam, the capsules release their liquid cores which leads to a detectable color change and, thus, enables non-destructive condition monitoring of the bond. In order to examine the feasibility of the approach, microcapsules are formed via interfacial polymerization. Microscopy techniques such as optical or scanning electron microscopy allow to study the capsule morphology, shape and dimensions (size and wall thickness) in dependence to the preparation procedure. Thereupon, the durability and release behavior are investigated with thermal analyses (differential scanning calorimetry and thermogravimetric analyses). Atomic force-based nanoindentation measurements give an insight into the size-dependency of mechanical properties like stiffness and burst forces.

Finally, the principle of health monitoring is evaluated by dispersing the prepared capsules in the adhesive systems.

Apart from the experimental examinations, numerical simulations of the crack propagation within the adhesive matrix are performed to demonstrate the effect of different microcapsule sizes and capsule walls on the fracture behavior.

This preliminary study demonstrates the basic feasibility of the approach, but there is still a great need for investigations in order to employ the concept for industrial purposes.     

Effects of Disturbing Parameters on the Stability of Latex and Resorcinol Formaldehyde Latex Based Adhesives

Synthetic cords may be coated with resorcinol formaldehyde latex (RFL)-based adhesives to adhere the cord to the rubber in industrial goods such as tires and conveyor belts. The stability of the adhesive and the stability of its component latex are crucial, both for ideal adhesion and for the homogeneity of the cord surface. Latex is a colloidal polymeric dispersion, which may lose its stability upon mechanical stress or upon interaction with some chemicals that lead to the formation of coagulated polymeric particles. This article reports on the influences of both external mechanical stresses and chemical interactions on RFL adhesives and latex stability, adhesion, and viscosity. High speed mixing, treatment with excess RF, and temperature variations were applied as disrupting parameters.     

Effect of polymerization protocol on the degree of conversion of photo- and dual-polymerized self-etch adhesives

This study investigated the effect of different polymerization protocols on the degree of conversion (DC%) of various photo-polymerized and dual-polymerized self-etch adhesive resins. Five different photo-polymerized (All-Bond Universal, Bisco; G-ænial Bond, GC; Futurabond M+ LC, VOCO; Single Bond Universal LC, 3M ESPE and Peak Universal Bond, Ultradent) and four dual-polymerized self-etch adhesives (Futurabond U, VOCO; Gradia Core SE, GC; Futurabond M+ DC, VOCO and Single Bond Universal DC, 3 M ESPE) were tested. All adhesives were applied on potassium bromide pellets (KBr) following the manufacturer’s instructions. The KBr pellets were divided into 10 experimental groups for the photo-polymerized adhesives and 12 experimental groups for the dual-polymerized adhesives according to the two levels of the study, Level 1: polymerization protocol and Level 2: adhesive system. For the photo-polymerized adhesives, the adhesives were polymerized either at 1 or 10 mm from the KBr pellets. For the photo-polymerized adhesives, the adhesives were photo-polymerized either at 1 or 10 mm distance or polymerized chemically. The DC% of the unpolymerized and polymerized adhesives was assessed using Fourier transform infrared spectroscopy. Data were analyzed using two-way ANOVA to evaluate the effect of polymerization protocol, adhesive system, and their interaction on the DC% of the self-etch adhesives. For the photo-polymerized and dual-polymerized adhesives, one-way ANOVA and Tukey HSD post hoc test was used to evaluate the effect of adhesive system within each polymerization protocol and the effect of polymerization protocol within each adhesive for the dual-polymerized adhesives (p = 0.05). Student t-test was used to compare the effect of polymerization distances within each photo-polymerized adhesive. For both photo- and dual-polymerized adhesives, the polymerization protocol and adhesive system had a significant effect on the DC (p = 0.000). The interaction between the two factors (polymerization protocol and adhesive system) revealed also a significant effect on the DC% of the different adhesives (p = 0.000). Polymerization distance of 1 mm showed significantly higher DC% compared to 10 mm distance. When the dual-polymerized adhesives were left to set chemically, they showed the lowest DC% among all polymerization protocols. DC varied depending on the chemical composition of the self-etch adhesives. The tip of the polymerization device should be positioned as close as possible to the surface to achieve higher DC% of the tested adhesives. Photo-polymerization of the dual-polymerized self-etch adhesives is a mandatory step to improve their DC.     

Skin permeation of buflomedil form adhesive matrix patches

The main objective of this research work was to fabricate and evaluate adhesive matrix-type transdermal patches of buflomedil hydrochloride, employing different ratios of pressure sensitive adhesives (PSAs) by solvent casting technique. The adhesive matrix-type transdermal patches were evaluated by their in vitro physicochemical properties such as thickness, moisture content, weight variation, drug content uniformity, etc. The effects of PSAs ratio, drug loading, and concentration of permeation enhancer were evaluated thoroughly. Ex vivo skin permeation studies with kinetic modeling of adhesive matrix patches were systematically evaluated. Based on the above observations, the best optimized buflomedil hydrochloride-loaded adhesive matrix-type transdermal patch was further characterized by scanning electron microscopy, Fourier transform infrared spectroscopy, X-ray diffraction study, and differential scanning calorimetry analyses. Drug containing adhesive matrix patches showed sustained release property without showing any incompatibility in adhesive matrix system. Hence, adhesive matrix-type transdermal patches of buflomedil hydrochloride can be used as a potential carrier for sustained transdermal delivery of hydrophilic drugs like buflomedil hydrochloride.     

一种无溶剂型双组分聚氨酯胶粘剂的研制

以聚醚多元醇(PPG)、碳化二亚胺-脲酮亚胺改性4,4′-二苯基甲烷二异氰酸酯(MDI-100LL)、多亚甲基多苯基多异氰酸酯(PAPI)和3,3′-二氯-4,4′-二氨基二苯基甲烷(MOCA)为主要原料,制备出一种双组分无溶剂聚氨酯(PU)胶粘剂。研究了PPG对胶粘剂黏度、交联剂对固化速率的影响,并测试了双组分不同配比时胶粘剂的性能。结果表明:采用高相对分子质量的PPG能显著降低胶粘剂的黏度;交联剂含量与固化速率成正比;调节双组分的配比,可以制备出满足不同施工要求的胶粘剂;固化后胶膜的玻璃化转变温度(T_g)达到-45.6℃。     

Preformed particle toughening of epoxy‐based film adhesive systems: The effect of particle size and chemistry

A new family of particulate modifiers was incorporated into an epoxy‐based model film adhesive system and the performance was evaluated. The particulate modifiers were selected to include a range of particle sizes, chemistry, and functionality. Thermal analysis, lap shear, and fracture energy tests were performed to characterize the performance of the adhesives. The mechanisms of failure for the adhesives were analyzed in relation to the particle modifier characteristics. Significant differences were found for mode I fracture energy when comparing adhesively joined composite specimens in cocured and bonded situations. Large preformed particle modified adhesives had nearly the same G_IC values for both cocured and bonded applications, while the G_IC values for the much smaller core‐shell particle modified adhesives differed significantly. All particle modified adhesives provided an improvement in mode II fracture toughness over that of the control such that the laminates failed either in compression (through‐thickness direction) or through delamination of the prepreg plies.     

碳酸钙渣理化性质与流动性分析

采用SEM、XRD等测试手段对碳酸钙渣理化性质进行了分析和表征,并对其流动特性进行了检测。结果表明,碳酸钙渣是由粒径小于120μm的颗粒组成,平均粒径为16.43μm。其主要化学成分是CaO和SiO2,主要晶相为石灰石和石英。流动性试验表明碳酸钙渣流动性不大好,喷流性较强。