Search

Purpose: The silicone modifications of two-component epoxy resin coatings are commonly built on epoxy resins rather than on epoxy curing agents. The silicone-modified epoxy curing agent system is rarely reported yet. This study aims to prepare the polysiloxane (PS)-modified waterborne epoxy coatings based on aqueous curing agents technology. Design/methodology/approach: Waterborne epoxy curing agents with different contents of terminal epoxy PS were synthesized by reacting with triethylenetetramine, followed by incorporating of epoxy resin (NPEL-128) and polyethylene glycol diglycidyl ether. The waterborne epoxy coatings were prepared with the above curing agents, and their performance was investigated through thermogravimetric analysis, scanning electron microscopy, mechanical characterization, gloss measurement, chemical resistance test and ultraviolet (UV) aging experiment. Findings: The results showed that the epoxy coating prepared by silicon-modified curing agent has higher gloss, better chemical resistance and UV resistance than the coating from unmodified curing agent with terminal epoxy PS and commercially available waterborne epoxy curing agent (Aradur 3986), as well as the competitive mechanical properties and heat resistance. Reduced water absorption on fibrous paper was also obtained with the help of silicon-modified curing agent. Originality/value: These findings will be valuable for resin researchers in addressing the modification issues about waterborne epoxy resin and curing agent. [ABSTRACT FROM AUTHOR]

On the basis of searching a large number of literatures, this paper systematically classifies ambient temperaes asphalt mixes from the aspects of material composition and strength formation mechanism; the influencing factors and research progress of various ambient temperature asphalt mixes are introduced; finally, comprehensively compare the performance and characteristics of various ambient temperature asphalt mixes, and put forward prospects for the next research, in order to provide help for engineers to reasonably design ambient temperature asphalt mixes and promote the innovative development of green roads. [ABSTRACT FROM AUTHOR]

Poly(vinyl acetate), PVAc, adhesives are commonly used for wood bonding; however, they are fossil-based and the final products usually do not have a sufficient water resistance for more durable applications. In this study we prepared an adhesive formulation by grafting VAc from chitosan using emulsion polymerization, chitosan- graft -PVAc. Thereby, we could decrease the fossil-based content of the adhesive and at the same time significantly improve the water resistance. Chitosan by itself has very good bonding properties as a wood adhesive, especially regarding water resistance; however, very low solid contents of the adhesive formulation can be achieved due to a very high viscosity of chitosan adhesives. In our chitosan- graft -PVAc adhesives, we explored two chitosan samples with different molecular weights, by using as-received chitosan and hydrolyzing it to a lower molecular weight. The chitosan fractions in the adhesives prepared with a higher molecular weight chitosan were 15, 20 and 25 wt%. However, due to the high viscosity, a solid content higher than 17 wt% could not be achieved for these adhesives. Sufficient bond strengths were achieved when the adhesive was applied in 122 g/m2 solid spread rate. In order to decrease the viscosity, we used hydrolyzed chitosan, with a lower molecular weight, to allow for a higher adhesive solid content, 34 wt%, and for a higher chitosan fraction, 40 wt%. In the adhesive with 40 wt% chitosan and 17 wt% solid content, all VAc was grafted from chitosan. This decreased the molecular mobility of the chains, leading to a lower susceptibility to plastic creep in the adhesive which contributes to the final bond strength. The dry and wet strengths of the specimens bonded with adhesives containing chitosan were higher than the strength of the specimens bonded with the reference PVAc adhesive. [Display omitted] • Wood adhesives are prepared by grafting vinyl acetate from chitosan. • By the introduction of chitosan, the fossil content can be reduced by 40 %. • The water resistance of the PVAc adhesive is improved when chitosan is introduced. • A lower molecular weight chitosan allows for higher chitosan- and solid content. [ABSTRACT FROM AUTHOR]

3D printing technology is widely used in the manufacturing of fine ceramic fields due to its simple operation, rapid molding, and applications in preparation of complex structures. In this paper, the characteristics of different 3D printing technologies in ceramic preparation were reviewed based on the material morphology of 3D printing ceramics. The application and mechanism of binder and dispersant applied in direct ink writing, stereolithography and inkjet printing 3D printing technology of ceramics were introduced, and these additive components of water based and non-water based were summarized and discussed, aiming to provide reference for the preparation of high-performance ceramic samples via 3D printing technology. [ABSTRACT FROM AUTHOR]

In this study the influence of boron acrylates as functional monomer on adhesive and cohesive performance of water-borne pressure-sensitive adhesives coated on bi-orientated polypropylene (BOPP) has been investigated. A series of pressure-sensitive adhesives with different monomer composition was prepared using emulsion polymerization. The monomers were butyl acrylate; methyl methacrylate; acrylic acid; boron acrylate; and multi-acrylate functional boron methacrylate. The adhesive performance was studied at 0, 1.3 and 3.9% of boron acrylate monomer content based on total monomer composition and 1% of multi-acrylate functional boron methacrylate. The adhesives obtained with constant thickness were coated onto a BOPP and evaluated for the performance by measuring the tackiness, peel strength and shear strength on several surfaces including stainless steel, glass, aluminum (Al) and low density polyethylene. Results showed that addition of boron acrylate was slightly increasing the adhesion and cohesion performance on non-polar surfaces. While it did not show any dramatic decrease in the adhesive performance for different surfaces, the decomposition temperature showed increase in TGA analysis. [ABSTRACT FROM AUTHOR]

1,5-Pentamethylene diisocyanate, a novel aliphatic diisocyanate formed from bio-based 1,5-pentamethylenediamine, has been used as a hard segmented material to synthesize polyurethane. In this study, several waterborne polyurethane (WPU) dispersions have been successfully prepared by a prepolymer process from 1,5- pentamethylene diisocyanate poly(polyether) with different NCO/OH ratios and 1,6-hexanediol (HDO)/dimethylol propionic acid (DMPA) molar ratios. The Fourier transform infrared (FTIR) spectra, thermogravimetric analysis, differential scanning calorimetry, X-ray diffraction, and a mechanical tensile test were used to investigate the structures, thermal stability, phase separation, crystallinity, mechanical properties, and adhesive performance of the WPU dispersions. The FTIR results indicate that the degree of hydrogen bonding and the numbers of urea groups increase as the NCO/OH ratio and HDO/DMPA molar ratio increase. Furthermore, the phase separation increases and the thermal stability decreases as the NCO/OH ratio increases or the HDO/DMPA molar ratio decreases. Finally, WPU3.0-2.4 (NCO/OH = 3, HDO/DMPA = 2.4) exhibits a maximum tensile strength and shear strength, pointing to its possible use as an adhesive. These results could provide a very valuable reference for industrial applications of WPU. [ABSTRACT FROM AUTHOR]

Abstract Cu 2 ZnSnS(e) 4 deposited using solution processes has potential for terrawatt-scale deployment. The champion highest efficiency Cu 2 ZnSn(S, Se) 4 cell published in literature is spin-coated using the highly dangerous hydrazine which is an impractically scalable solvent and deposition combination. As an alternative solvent amine-thiol mixtures have shown to complex with a wide range of binary chalcogenides with much lower health risks than hydrazine. Herein we present two further toxicity reductions, first by employing a less harmful amine-thiol pairing and second by using water as a diluting solvent. We exclude extraneous elements from the precursor solution such as halogens and with a sub-micron thickness crystalline absorber achieve an efficiency of 6.8%. With the modified solution deposited by ultrasonic spray pyrolysis, this solution process is scalable, abundant, and relatively non-toxic. Highlights • 6.8% Efficient kesterite solar cell. • Metal oxides dissolved in a water-based solution process. • Deposited by ultrasonic spray pyrolysis. [ABSTRACT FROM AUTHOR]

The stability of polyacrylate and polyester based aqueous dispersions designed for ultrathin coating of extruded plastic films, especially bi-axially oriented polyethylene terephthalate (BOPET), was studied. Also, the effect of the gemini surfactant based defoaming/wetting agent on the properties of the dispersions was examined. The addition of the defoaming/wetting agent resulted in reducing the surface free tension of the polyacrylate and polyester dispersion by 15% and 20%, respectively and the initial foam height by 60% and 15%, respectively. At the same time, the agent addition did not compromise the temperature and pH stability of the dispersions. Such modified dispersion can be utilized for ultrathin coating of plastic film used for packaging, to improve their processability, printability, and metallization. [ABSTRACT FROM AUTHOR]

Core-shell latex-based pressure-sensitive adhesives comprising n-butyl acrylate, styrene and acrylic acid were prepared via two-stage seeded semi-batch emulsion polymerization. d-Limonene (Lim) was used as a renewable chain transfer agent. Adhesive performance was modified by manipulating the microstructure of both the latex particle cores and shells. In the first stage of the polymerization, the concentrations of Lim and divinylbenzene (DVB) crosslinker were varied to alter the core microstructure and thus, the cohesive strength of the adhesive films. The particle shell microstructure was modified in the second stage of the polymerization by varying only the amount of Lim. As a result, a variety of particle microstructures and morphologies were generated. Tack and peel strength decreased with increasing Lim concentration while shear strength showed a maximum at a moderate core Lim concentration of 2 phm. Empirical models were developed using stepwise regression to correlate tack, peel strength and shear strength to Lim concentration in the core/shell and DVB concentration in the core. [ABSTRACT FROM AUTHOR]

Twelve kinds formulation of natural rubber grafted copolymer styrene (NR-g-S) prepared by gamma radiation co-polymerization technique has been carried out. The characteristic of NR-g-S and its water base coating such as molecular structure, particle size, and the properties of latex and its film were evaluated. The results showed that the NR-g-S latex as a water base coating has low viscosity, height strength, good grease resistance, good flexibility, good aging and corrosion resistance on concrete cement and metal. The average particle size is between 270-300 nm, and the bonding between poly-isoprene of NRL and styrene molecules were grafted copolymer

Swelling elastomers are special polymers that increase in volume when exposed to water or oil. They have been successfully deployed in oil and gas wells for isolation of water-producing zones, partial replacement of cementing, slimming down of wells, and so on. Performance appraisal and design modifications cannot be attempted without knowledge of material response under specific field conditions. Results from an experimental investigation are presented here about the behavior of two commercial elastomers, one water swelling and one oil swelling. Of the one-month total testing time, one set of samples (for each elastomer type) was tested under acid for one day, and the other set without any acid exposure. Readings were taken at different stages of swelling to record the variation in volume, thickness, and hardness of elastomer samples. Test parameters were set to match existing conditions in a regional oil well. These results can be used to assess performance of elastomers under given well conditions and for modeling and simulation of seal behavior. [ABSTRACT FROM AUTHOR]

Poly(vinyl acetate) (PVAc) water-resistant glues used in the wood industry and belonging to the class of durability D3 show high resistance to both water and heat compared to the usual PVAc-based thermoplastic products. In conventionally synthesised adhesives this is attained by means of cross-linking (although limited) of the linear polymer chains and moreover by using inorganic salts, such as aluminium chloride. The paper illustrates the limits of these products and presents the prospects in the chemistry of industrial-grade D3-class PVAc adhesives. More in detail, it is shown how the individual roles of both cross-linking agent and aluminium chloride contribute to the occurrence of recurring inconveniences characterising conventional PVAc-D3 glues, which include formaldehyde release during time (mostly related to the curing agent), glueline colouring and indirect staining of wood (both are mostly evident in selected wood species, in the presence of either heat or UV irradiation), acidic pH, and equipment corrosion (related to the presence of aluminium chloride). Understanding those mechanisms has constituted the basis for the development of newly synthesised PVAc-D3 glues, whose characterisation is expressly reported in the present work. Such systems have shown good adhesion to wood surfaces and have exhibited neither corrosive nor chromatic alteration evidences, as well as absence of formaldehyde emissions. All these occurrences were verified by specific tests, such as corrosion on steel, measurements of the formaldehyde content of the dispersion, and emissions from panel boards, and glueline exposure to both temperature and UV irradiation after application in selected wood species. [ABSTRACT FROM AUTHOR]

Herein we disclose a novel formulation of two components water-based adhesive from a natural source, which is designed to glue lignocellulosic surfaces, mainly cork and wood. It is based on the aqueous extraction of liquefied cork, which results from the polyhydric alcohol acid-catalyzed liquefaction of cork dust or granules. The vacuum concentration of the referred extract leads to the first adhesive component, which is then mixed and homogenized with the second one, a curing aliphatic compound. The addition of “cork powder” to the adhesive formulation creates a stable adhesive with good shear strength values. Thus, a methodology for the valorization of cork dust, a hazardous waste, is here outlined. [ABSTRACT FROM AUTHOR]

Acid-converted maize starch (ACS) was quaterized and then sulfosuccinylated in aqueous dispersion of starch to introduce 3-(trimethylammonium chloride)-2-hydroxypropyl (TACHP) and sulfosuccinate (SS) onto its backbones. A series of quaterized and sulfosuccinylated maize starch (QSS) samples with different zeta potentials were derived by altering the molar ratio of TACHP to SS substituents for exploring the influences of TACHP and SS substituents on the adhesion of QSS to viscose fibers and surveying the removability of QSS from sized viscose yarns. A desirable ratio of TACHP to SS was determined for alleviating the adverse impacts of (1) sulfosuccination on the adhesion and (2) quaterization on the removability. The adhesion was determined by a standard method (FZ/T 15001-2008), while the removability was assessed through an oxidant desizing under alkali conditions. It was found that this combined modification was able to alleviate the adverse impacts. The adhesion and removability of QSS were related to its zeta potential, depending on the ratio of TACHP to SS substituents. An increase in the potential favored adhesion, but disfavored removability. Electroneutral QSS had strong adhesion and good removability simultaneously, taking into account adhesion and removability. Furthermore, increasing the modification level at electroneutrality was helpful to the adhesion and removability. [ABSTRACT FROM AUTHOR]

We present a method for the enzyme mediated buildup of protein adhesive layers. The process is based on our autodeposition-like formation of biological coatings. The presented example utilizes the enzymatic destabilization of casein micelles with the aspartic protease chymosin—the same process that is used in cheesemaking. If two adjacent support surfaces with adsorbed enzyme are immersed into a casein dispersion, protein layers will form on both surfaces and eventually form an adhesive layer between them. As a proof of concept, we show that the process works as intended, and that in fact the enzymatic process is the driving force. Several parameters are examined and the resulting layers are investigated via scanning electron microscopy. [ABSTRACT FROM AUTHOR]

The mechanical properties and water impermeability of the developed cool white roof coating based on styrene acrylic copolymer and cement are systematically investigated in the current paper. The coating has good tensile properties, adhesion strength and compliance at low temperature. In particular, the coating possesses excellent water impermeability. The good flexibility and compliance at low temperature result from the low glass transition temperature of the high elastic styrene acrylate copolymer emulsion. Compared with the untreated specimens, after thermal, alkali, water immersion and ultraviolet treatments, the tensile strength of the coating is increased, while its breaking elongation is decreased. In addition, the coating has good artificial accelerated weather resistance in terms of mechanical properties. The excellent water impermeability of the coating stem from the cross-linked nature of the high elastic styrene acrylate copolymer emulsion, the formation of interpenetrating network structures and the Ca 2+ bridging effect. [ABSTRACT FROM AUTHOR]

Grafting of methyl methacrylate (MMA) and styrene (St) onto polychloroprene latex (CRL) was carried out successfully using emulsion polymerization. The chemical structure of the grafted copolymer was characterized using Fourier transform infrared spectroscopy. The compatibilizing effects of the grafted polymer CRL-g-(MMA-co-St) on the CRL/styrene-acrylate emulsion (SAE) blend were investigated using scanning electron microscopy (SEM), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and mechanical testing. The results showed that the mechanical properties of the contained CRL-g-(MMA-co-St) blend improved significantly in comparison to those of the simple CRL/SAE blend. For the contained CRL-g-(MMA-co-St) blend, the maximum tensile strength (6.72 MPa) and the maximum elongation at break (1142.6%) were obtained when the content of SAE was 60% (occupied by the total dry weight). At the same content of SAE, the T-peel and lap shear strengths of the contact adhesive derived from the contained CRL-g-(MMA-co-St) blend were 5.3 N/mm (canvas to canvas) and 1.8 MPa (plywood to plywood), respectively. The grafted copolymer CRL-g-(MMA-co-St) showed a remarkable compatibilizing effect on the CRL/SAE blends by drastically improving their mechanical properties. [ABSTRACT FROM PUBLISHER]

Water borne polyurethane dispersions synthesized using poly caprolactone-isophorone diisocyanate combination and caprolactone-metatetramethyl xylene diisocyanate combination. Thermal stability of the polyurethane dispersions was studied using thermogravimetric technique. The activation energy of decomposition of these polyurethane dispersions was determined by applying classical kinetic models and isoconversional method. Though the classical kinetic models assume constant activation energy for any reaction, the activation energy determined is in good agreement with that obtained via isoconversional analysis. However, the advantage of isoconversional analysis is highlighted compared to classical kinetic models based on the mechanism delineating capacity of isoconversional analysis. The present work compares the thermal stability of the aqueous polyurethane dispersion formed from poly caprolactone-isophorone diisocyanate with caprolactone-metatetramethyl xylene diisocyanate. [ABSTRACT FROM AUTHOR]

Abstract: Bubble pump (BP), an essential component in coffee percolators, is used to drive solar water heating systems and single pressure absorption refrigerators. However, its mass flow rate cannot be readily predicted. Heat input, tube diameter and submergence ratio affect its mass flow rate. BP has the same working concept as air-lift pump, but its flow is complicated due to the condensation of vapour bubbles. Neither curve fitting models, nor air-lift pump models, can predict the mass flow rate with high fidelity. A new model based on the pumping characteristics of BP is presented and verified by a water based setup at atmospheric pressure. Results show that the average errors for the BP with tube diameter of 6–12 mm, and for the BP with submergence ratio of 0.5–0.8 are 13% and 11%, respectively. The BP performance increases when the tube diameter decreases or the submergence ratio increases. [Copyright &y& Elsevier]

Abstract: Polyurethane anionic adhesives were synthesized as waterborne polyurethane dispersions (PUDs) by modified dispersing procedure, using isophorone diisocyanate, dimethylol propionic acid, ethylenediamine as a chain extender and a range of soft segments with various macrodiols proportions. The soft segment was formed by replacing poly(propylene glycol) (PPG) as polyether polyol with polycarbonate diol (PCD), as polyester polyol. The effect of the macrodiols proportions of soft segment on the thermal properties of polyurethane films was measured by thermogravimetry analyses (TGA) and differential scanning calorimetry (DSC) methods. The infrared spectroscopy (FTIR) was used for evaluating the degree of phase separation. The results showed that phase separation between hard and soft segments of poly(ester–urethane) is more significant than of poly(ether–urethane). The phase separation degree of polyurethane dispersion significantly affected the glass transition temperature (T g) and film properties. While the phase separation degree increased, T g proportionally decreased, but the hardness and gloss of the dried films increased, as expected. However, thermal stability was influenced by the molecular weight of used polyols and chemical structure of the polyols, and it was described by the effect of oxygen content, and interaction between the soft and hard segment, and the soft segment composition. The soft segment can be achieved with a proper selection, in order to fine-tune the performance of waterborne polyurethane dispersion, considering certain practical application. [Copyright &y& Elsevier]

Abstract: A waterborne polyurethane coating with reflectivity higher than 95% in the visible wavelength range of 380–750nm has been formulated. The impact of pigment concentration and carboxyl functional dispersing agent percentage on the adhesion of this waterborne polyurethane-based coating to an aluminum substrate is characterized at various pigment weight fractions by peel strength using modified ASTM D 1876-93. The formulated coating was also examined by SEM, UV/vis spectrophotometer with integrating sphere, and ATR–FTIR. Results indicate that the reflectivity of the coating increases with pigment volume concentration while the peel strength decreases. At high pigment-to-binder ratios a change in failure mode from adhesive to cohesive was observed. Further experiments indicate that adhesion increased at high pigment-to-binder ratios due to the presence of carboxyl functional groups of the dispersing agent. The increase in adhesion was identified for the first time and attributed to the interaction of the carboxyl functional groups in the dispersing agent with the aluminum surface. [Copyright &y& Elsevier]

Abstract: This study investigated the utilization of resin impregnated decorative and overlay paper wastes obtained from the edge trimming of partially cured, dried papers as a binder in the manufacture of the light medium density fiberboard (MDF). The light MDF panels were prepared from various mixtures of the softwood fiber and hammer-milled impregnated paper waste, 95/5, 90/10, and 80/20wt%. The results of the experiments showed that the dimensional stability and mechanical properties of the light MDF panels were improved by adding hammer-milled melamine impregnated paper waste. The resin impregnated paper waste could be evaluated as a binder for the manufacturing of the light MDF panels having better dimensional stability and mechanical properties than standard light MDF panels used in interior applications. [Copyright &y& Elsevier]

Abstract: Waterborne polyurethane adhesives are an interesting alternative to the current solvent-borne polyurethane adhesives used in the industry. Different aliphatic waterborne polyurethane dispersions (PUDs) with different solids content were synthesised by reacting isophorone diisocyanate (IPDI) with a polycarbonate derived from hexanediol via the acetone method. The PUDs were characterised by Brookfield viscosity, pH, particle size, transmission electron microscopy (TEM) and solids content measurement. The dry polyurethane films were characterised by ATR-IR spectroscopy, plate–plate rheology, differential scanning calorimetry (DSC) and thermal gravimetry (TGA). Their adhesion was evaluated from T-peel tests of flexible PVC/waterborne polyurethane dispersion/flexible PVC joints and single lap-shear tests of aluminium/waterborne polyurethane dispersion/aluminium joints. The PUDs showed bimodal particle size distribution. The mean particle size of the PUDs decreased by increasing their solids content but the particle size distribution of the PUDs increased by decreasing their solids content. As the solids content increased the Brookfield viscosity of the PUDs increased due to lower mean particle size where particle crowding was favoured, the PUD having 44wt% solids content was an exception (higher particle size but lower polydispersity). On the other hand, the increase in the solids content increased the hard segments content and the degree of phase separation of the polyurethanes. The greater the solids content of the polyurethanes, the lower their glass transition temperatures values and the lower the elastic moduli. Adhesive strength under peel stresses were not affected by the solids content in the polyurethanes but the single lap-shear strength values decreased by increasing the solid contents in the polyurethanes due to lower hard segments content. [Copyright &y& Elsevier]

Purpose – The purpose of this paper is to investigate the effects of the components of whey-protein based aqueous polymer-isocyanate (API) adhesives on the bond strength. Design/methodology/approach – The bond test (according to the JIS K6806-2003 standard), Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM) were used to characterise the whey-protein based API adhesives with various formulations and processing technologies. Findings – The good bond strength of the optimised whey-protein based API adhesive was attributed to the formation of strong chemical bonds in the bondline and to the additions of polyisocyanate, polyvinyl alcohol (PVA) and nano-CaCO3 powder that improved adhesive cohesive strength by either chemical crosslinks or mechanical interlocking. The blending procedures of whey protein, PVA, polyvinyl acetate (PVAc) and p-p-MDI had great impacts on the performances of the whey-protein based API adhesives. Research limitations/implications – SEM micrographs showed that the effects of blending processes on the bond strength, pot life and colour might be attributed to the particle size of hydrophobic p-MDI droplet and p-MDI distribution in the protein-PVA matrix. Practical implications – The study lays the foundations of the formulation design and the processing technology for preparing whey-protein based API adhesives. Originality/value – The effects of the components of whey-protein based API adhesives and the effects of blending processes on the bond strength were investigated by means bond strength evaluation, FTIR and SEM analyses; whey protein is utilised successfully to prepare novel API adhesives for structural uses. [ABSTRACT FROM AUTHOR]

Abstract: Wettability of 6 different wood species commonly used in the woodworking industry in the Mediterranean region was evaluated in this study. The species were Norway spruce (Picea abies Karst.), umbrella pine (Pinus pinea L.), oak (Quercus sp.p.), chestnut (Castanea sativa Mill.) beech (Fagus sylvatica L.) and poplar (Populus sp.p.), and their surfaces were machined according to 3 different processes: planing, sanding and disc-sawing. Measurement of dynamic contact angle and extractives (evaluated by means of GC–MS analysis) were carried out on freshly cut and 24h air exposed surfaces, in order to also evaluate the effect of ageing on wettability. The parameterisation of the contact angle vs. time curves allowed for the systematic statistical elaboration of data, in order to find the relationships existing between the four parameters characterising the dynamic curves and the considered factors (species, machining, ageing). The evaluations evidenced a different influence of these factors on the chosen parameters and hence some of them could be used to reliably assess both wood wettability and the effects of the factors here considered. In general softwoods showed higher contact angles than hardwoods due to the different anatomy and to the presence of resins and terpenes in addition to fatty acids and phenolic compounds, also present in hardwoods. After 24h air exposure a shifting upwards of dynamic contact angle curves was observed but, despite the variation in surface composition, this shifting was imputable to other inactivation factors. Also machining appreciably influenced wettability, and the sanded surfaces were the most wettable as compared to both the planed and the disc-sawn ones. On the other hand, these observed differences diminished after ageing due to the levelling effect of inactivation that overcame surface inhomogeneities. [Copyright &y& Elsevier]

Abstract: Waterborne polyurethane dispersions (PUDs), with possible use as adhesives, derived from polycarbonate diols (PCDs) were evaluated. The influence of the NCO/OH ratio and particle size distribution on the properties of both the aqueous dispersions and dry films were evaluated. The polydispersity of the PUD was increased by increasing its hard segments content. On the other hand, the properties of the PUDs depended on both the NCO/OH ratio and the polydispersity. As the NCO/OH ratio increased, the Brookfield viscosity of the PUDs decreased due to broader particle size distribution. On the other hand, an increase in the NCO/OH ratio decreased the crystallinity of the polyurethane films. Furthermore, the greater the polydispersity the higher the urea hard segment content, the higher the glass transition temperature value and the higher the elastic modulus of the polyurethanes. [Copyright &y& Elsevier]

Abstract: Different amounts of hydrophobically modified ethoxylated urethane-based thickener (HEUR) were added to improve the rheology of waterborne polyurethane adhesives. The thickened solid adhesive films were thermally annealed and characterised by IR spectroscopy, plate–plate rheology, dynamic mechanical thermal analysis (DMTA), differential scanning calorimetry (DSC), and thermogravimetric analysis (TGA). Hydrogen bonds played a key role in the thickening mechanism of polyurethane dispersions containing urethane-based thickener, along with ionic adsorption and micelles formation between hydrophobic groups. The adhesion properties were measured from T-peel test of leather/polyurethane adhesive/vulcanised styrene-butadiene rubber joints. Optimal results were obtained when water in the waterborne polyurethane adhesive (just before joint formation) was removed under open air, while forced air drying impeded the complete removal of water. On the other hand, the thermal annealing did not greatly affect the rheological and thermal properties of the thickened polyurethanes. [Copyright &y& Elsevier]

Abstract: Two series of cross-linkable waterborne polyurethane (WBPU) adhesives were synthesized by a conventional prepolymer process using 2,2-bis(hydroxymethyl) propionic acid (DMPA) (13.85 and 25.00mol%) and hexamethoxymethyl melamine (HMMM) as a hydrophilic agent and cross-linking agent, respectively. Using infrared (IR) and 1H NMR spectroscopy analysis, the cross-linking reaction between DMPA (carboxyl acid salt group) and HMMM (methoxy group) was identified, and it was found that two methoxy groups per HMMM molecule, containing six methoxy groups, participated in the cross-linking reaction. Adhesive strength significantly increased by cross-linking, up to the optimum content of HMMM (molar ratio of HMMM:DMPA=1:2) and then showed a small decrease with excess HMMM. Adhesive strengths of samples containing 25.00mol% DMPA (i.e. S-series) were higher than those of samples containing 13.85mol% DMPA (i.e. P-series). It was found that the optimum pressing conditions for joint values and optimum HMMM content gave the highest failure temperature and thermal stability of adhesives. [Copyright &y& Elsevier]

Abstract: Three poly[(vinyl acetate)-co-N-methylolacrylamide] (VAc–NMA) latex adhesives were synthesized, each containing the same total amount of NMA. In each of the three co-polymerizations, the NMA was fed into the reactor according to a unique feed profile. NMA distribution in the latexes, as determined via both 13C and 15N variable temperature solution nuclear magnetic resonance (NMR) spectroscopy, differed among the three adhesives. When NMA monomer was added via injections (latex I), predominantly surface-NMA (62.7%) was detected, with significant amounts of water-phase NMA (20.8%) and core NMA (16.5%). Delayed NMA injections (latex DI) led to a very high proportion of surface NMA (82.3%) with less core (10.6%) and water-phase NMA (7.1%). A continuous feed of NMA (latex C) gave predominantly core NMA (84.7%), some surface NMA (13.4%) and very little water-phase NMA (1.9%). NMA distribution findings from 15N-NMR and 13C-NMR analyses were consistent. [Copyright &y& Elsevier]

Abstract: Wood adhesives play an essential role in industry, however, many contain significant amounts of toxic components and volatile organic compounds (VOCs) and most are produced from depleting petrochemical resources. We are currently investigating adhesives derived from microbial extracellular polysaccharides for use in the wood products market. Polysaccharides are generally non-toxic, biodegradable, and produced from renewable resources. This study focuses on a new extracellular polysaccharide-based adhesive with performance that may be useful in some wood product applications. The adhesive exhibits improved performance over a previously described bacterial polysaccharide and produces shear strengths on maple substrates of up to 20MPa at 53% relative humidity and 22°C. Full strength was achieved in two days with half strength in 2h. Although shear strength was sensitive to relative humidity, moisture resistance was substantially increased by partial acetylation of the polysaccharide. [Copyright &y& Elsevier]

This study has been conducted to determine the effects of wood pre-treatment on bonding strength of wood materials. To this end, the test samples prepared from Oriental beech (Fagus orientalis lipsky), oak (Quercus petraea liebl.), scotch pine (Pinus sylvestris lipsky) and Toros cedar (Cedrus libani A. Rich) woods materials (based on BS EN 204) were impregnated with Imersol-Aqua (I-A) by short-term, middle-term and long-term dipping methods according to the procedure of ASTM D 1413-76 standards and directions of the manufacturer. After impregnation, shear strength tests (based on BS EN 205) were applied on both sanded and non-sanded connection surfaces jointed by poly(vinyl acetate), Klebit 303 (K303), Kleiberit 305.0, Super-Lackleim 308 (SL308) and polyurethane (PU) (diphenylmethan-4, 4′-diisocyanate) adhesives. For the samples not sanded after impregnation, the highest shear strength was obtained in beech impregnated by the short-term dipping method and bonded with K303 (11.99 N/mm2), whereas the lowest was in pine impregnated by long-term dipping and bonded with K303 (8.078 N/mm2). As for sanded samples after impregnation, the highest shear strength was obtained in beech (12.69 N/mm2) impregnated by short-term dipping and bonded with PU, whereas the lowest was in cedar (8.038) impregnated by long-term dipping with SL308. Accordingly, impregnation affected adhesive bonding strength negatively, whilst bonding surface sanding after impregnation affected adhesive bonding strength positively. To bond after the sanding process of impregnated surfaces is highly recommended to obtain high bonding strength in I-A-impregnated solid wood furniture and solid wood furniture elements. [Copyright &y& Elsevier]

Changes in regulations aiming at reducing the impact that technologies such as coatings, adhesives, cleaners have on the environment is leading to large advances in these end-use technologies. In achieving the required quality of the end product, and irrespective of whether this is in areas such as high solids paints or water-based coatings, solvents keep on playing an important role. At the same time different requirements are set for the solvents employed. The changing role of solvents and the technological benefits solvents are bringing are discussed. It is shown that the computer programme BLENDPRO is an effective reformulation tool which assists in the efficient development of new formulations in these areas. [ABSTRACT FROM AUTHOR]

Nowadays, the majority of adhesives used in particleboards (PB) manufacture are formaldehyde-based. In the present research work a low-cost bioadhesive, based on the combination of thick spent sulfite liquor (TSSL) with wheat flour, was tested for the production of three-layer particleboards, at different conditions (particleboards target density, pressing time, pressing temperature, wood type and binder age). It was possible to produce particleboards with densities ranging from 682 kg m−3 to 783 kg m−3, at pressing temperatures from 180 to 210 °C, and pressing times between 8 and 10 min. All the particleboards produced in these conditions were in accordance with the internal bond strength requirements of standard EN 312 for particleboards type P2 (0.35 N mm−2). The best result (0.69 ± 0.01) N mm−2 was obtained for particleboards pressed for 10 minutes at 200 °C with the recycled wood mix. Regarding resin stability, the particleboards manufactured with the binder, stored for 30 days, presented good internal bond strength ((0.58 ± 0.02) N mm−2), above the requirements of standard EN 312 for particleboards type P2. [ABSTRACT FROM AUTHOR]

Ultrathin silver nanowires (UTAgNWs) are indispensable to achieve transparent conductive films (TCFs) with overall optoelectronic performance exceeding that of the state-of-the-art indium tin oxide films. Impurities in raw UTAgNW products severely impair the optical properties of TCFs. Unfortunately, highly effective and environment-friendly approaches for purification of UTAgNWs are still lacking. Herein, we report the purification of UTAgNWs using deionized water along with a small amount of surfactants as the purifying agent. TCFs coated with the purified UTAgNWs exhibit a light transmittance of 97.9% and a haze of 1.22% at a sheet resistance of 36.3 Ω sq -1 or a light transmittance of 99.8% and a haze of 0.47% at a sheet resistance of 187.3 Ω sq -1 . Both the transmittance and the haze are among the best reported values for AgNW TCFs in the literature. The purification process does not involve any toxic or hazardous chemicals and is both scalable and cost-effective.