Water-based Adhesives Research Articles

Water-based polymer colloids with a branched chain architecture as low-gel pressure-sensitive adhesives

The performance of water-based acrylic pressure-sensitive adhesives was investigated. The latex particles had minimal gel content, typically below a few percent, and the polymer chains exhibited a branched architecture.

Reactive polyurethane hot-melt adhesives with high biogenic carbon content

ABSTRACTThe use of water-based or solvent-based polyurethane adhesives is widely extended in the footwear industry. However, reactive polyurethane hot-melt adhesives (RPHMA) represent a good option to substitute both technologies as they are solvent-free. Their environmental footprint can be further improved with the use of renewable raw materials for their synthesis. A typical RPHMA formulation includes macroglycols and isocyanates as raw materials, both of which are based on petroleum derivatives. Against this background, this work focuses on the development of RPHMAs based on polyols from renewable sources, which considerably improves their content in biogenic carbon. The evaluation of the new adhesives properties was conducted using different experimental techniques such as FTIR, TGA, DSC, CLSM, XRD, plate-plate rheometry, R&B softening point, biogenic carbon content (ASTM D6866–22, method B) and T-peel strength of adhesive joints (EN 1392:2007), before and after aging. The partial substitution of one of the conventional petroleum-based polyols by a bio-based polyol leads to a change in the segmented structure of polyurethane and an increase in the polyurethane thermal resistance and crystallinity. Furthermore, the new adhesives based on reduced fossil content meet the standard quality requirements on adhesive properties for footwear, according to EN 15,307:2015.

Development and formulation of a novel plasticizer-free polyvinyl acetate-based wood adhesive

Amongst water-based emulsion adhesives, polyvinyl acetate (PVAc) emulsion is majorly employed in the non-structural bonding of interior or exterior furniture and joinery industries. However, PVAc emulsion requires plasticizers, which inherently have challenges resulting in deteriorating thermal and mechanical properties. Hence, the present work focuses on formulating a plasticizer-free adhesive by copolymerizing vinyl acetate with butyl acrylate (BA). The physical, thermal, and mechanical properties of BA-incorporated adhesives were analyzed by viscosity, pH, water contact angle, pencil hardness test of films, and differential scanning calorimetry. Optimizing strategy by varying the content of BA was evaluated. The shear strength of the samples on the wood specimen was verified in dry conditions at various intervals, and in wet conditions as per EN 204 standard. The viscosity of the adhesives exhibited a positive shift, as the concentration BA increased. The hardness of PVAc films was also altered positively by the addition of BA. Water contact angle measurement unveiled the hydrophobic nature of BA incorporation. The performance of the newly formulated adhesive tested on dry conditions showed enhanced tensile shear strength, and the values were maximum for 1 wt. % BA sample. Tensile shear strength value measured at dry conditions after 7 d of drying displayed an increment of ∼5.5% on 1 wt. % BA sample, compared to pristine adhesive. Analysis at wet conditions also corroborated enhanced performance with BA incorporation. Hence by optimizing the content of BA, a new concept of PVAc emulsion adhesive without any plasticizer can be formulated, with enhanced water resistance and performance.

Preparation of isocyanate microcapsules by complex coacervation and its application in plywood

ABSTRACT At present, the use of isocyanate adhesives mostly requires the assistance of solvents, which can cause adverse environmental pollution and health effects. The aqueous isocyanate avoids the shortcomings of the solvent, but shortens the working life of the isocyanate. Isocyanate microcapsules can avoid these shortcomings, and can also solidify isocyanate to improve the efficiency of isocyanate use. In this study, microencapsulation technology was used to protect the highly reactive -NCO group, improve the stability of isocyanate, and prolong the working life of isocyanate in water-based wood adhesives. That is, isocyanate microcapsules with gum Arabic/gelatin as shell and isocyanate as core were prepared in oil-in-water emulsion by complex coacervation. In addition, the preparation process was optimized by changing the parameters. Then, the prepared isocyanate microcapsules were characterized and analyzed by Fourier transform infrared spectrometer, Scanning electron microscope, Particle size analyzer, etc. Finally, plywood was prepared by using the prepared isocyanate microcapsules in the wood adhesive. The results showed that, the particle size of isocyanate microcapsules was controllable, and the content of active groups and core in the prepared isocyanate microcapsules can reach a high level. The isocyanate microcapsules extend the working life of isocyanates from about 30 mins to 5 hours, and significantly improve the stability of isocyanates. The bonding strength of the prepared plywood meets the requirements of (Class I plywood) with only 20% -NCO addition.

Concentration effect of DMSO-dry bonding on the stability of etch-and-rinse bonds

ObjectivesTo examine whether lower dimethyl sulfoxide (DMSO) concentrations would affect long-term bond stability of simplified or multistep water-based adhesives to dry-etched dentin. MethodsH3PO4-etched mid-coronal dentin surfaces from human molars were randomly blot- or air-dried for 30 s and pretreated or not with 5 or 50 % (v/v) ethanolic DMSO solutions. Untreated samples served as control. Samples were bonded with a two-step or a three-step etch-and-rinse adhesive. Restored crown segments (n = 5/group) were stored in distilled water for 24 h and sectioned for microtensile bond strength testing. Resin-dentin beams (0.8 mm2) were tested under tension until fracture (0.5 mm/min) after 24 h and one year of storage in artificial saliva at 37 °C. Nanoleakage evaluation and hybrid layer characterization were performed by SEM. Bond strength data was examined by three-way ANOVA followed by the Tukey test (α = 0.05). Results: Dry bonding produced significantly lower bond strengths than conventional wet bonding for both water-based adhesive systems (p < 0.05). DMSO-dry bonding restored bond strengths and reduced nanoleakage levels, regardless of adhesive type or DMSO concentration (p < 0.05). Bond strengths of DMSO-dry bonded samples were not significantly affected by long-term ageing regardless of adhesive type or DMSO concentration (p < 0.05). SignificanceAlthough bonding methacrylate-based resins to etched dentin is normally performed under wet conditions, hybridization of air-dried collagen can outperform conventional wet bonding by employing water-free DMSO solutions with concentrations as low as 5 %. Reduced moisture-related technique sensitivity, higher bonding performance and improved hybrid layer stability may contribute to extend the service life of resin-dentin bonding.

Alternative Fiber-Based Paperboard Adhesion Evaluation with T- and Y-Peel Testing

Due to increased pressure on the availability of wood biomass in the EU and the regulatory attempts to lower CO2 values, where wood-based biomass plays a crucial role in carbon sequestration, the use of cellulose derived from alternative sources is gaining increased interest in the pulp and paper industry as well as in other industries. The processing properties of alternative fiber-based packaging need to be checked in current processing operations with other types of materials and recycling workflows. For example, in the production of folding boxes, after printing other converting properties such as glueability are also of great importance. The adhesive absorption and bonding strength of materials are important as adhesive joints of packaging can interfere with the protective function. In the presented research, three different paperboards produced on a pilot scale from alternative raw material sources were tested. Two paperboards were produced from the alien invasive plants Japanese knotweed and black locust, and one from residual sawdust. The basic paperboard properties were tested regarding paperboard porosity, roughness, z-directional tensile strength, and dynamical behavior regarding liquid interaction (contact angle and liquid penetration dynamic), as water-based adhesives were used in the research. For adhesive joint strength testing, Y- and T-peel adhesion testing was performed on the joint paperboard samples, as still there is no fully standardized method for the evaluation of such fiber-based material properties. The results indicate differences in the penetration dynamics of liquids. This parameter had the highest influence on the peel adhesion strength, while porosity, roughness, and dynamic contact angle were not so significant. Regarding the two adhesive joint tests, the differences in separate materials regarding peel adhesion curves show similar results. However, the Y-peel maximum force values are higher due to the testing setup (in comparison to the T-peel test). The paperboards made from invasive plants showed adhesive joint failures which are more suitable for tamper-proof packaging due to their low surface strength and crack propagation into the fiber structure.

A water-based adhesive with polar recognition both for TPO substrate and WPU coating

Thermoplastic polyolefin (TPO) is widely used in automotive interior materials, but it has long been faced with the challenge of weak adhesion between water-based polyurethane (WPU) coating and substrate. Herein, chlorinated polypropylene (CPP) was grafted by styrene (St) firstly, then a water-based CPP adhesives with polar recognition both for non-polar TPO substrate and polar WPU coating were prepared via phase conversion methods, and the adhesives properties as well as the adhesive mechanism for different polar substrates were investigated. The introduction of polystyrene side-chain has improved the recognition ability of CPP adhesive to non-polar TPO substrate and the interaction force between interfaces. Compared with unmodified CPP adhesive, T-peeling strength of modified one has increased by 35 % and reached 24.2 N/cm, meeting the adhesive requirements of TPO as an automobile interior material. Adhesive mechanism study reveals that polar mutual recognition CPP adhesive plays a bridging role, one end recognizes the non-polar TPO substrate and another end recognizes the polar WPU surface coating, and forms a strong bond between the guest and the host through their respective interfacial force.

Analysis of 10 Phthalate Esters in Water-Based Adhesives by Supercritical Fluid Chromatography-Tandem Mass Spectrometry Combined With Spherical Carbons-Based Dispersion Solid-Phase Extraction.

Spherical carbons have a porous structure and large surface area for adsorption of macromolecules in water-based adhesives. Supercritical fluid chromatography (SFC) can improve selectivity and obtain better separation for phthalate esters (PAEs). The aim of this study was to develop a simple and green method for the simultaneous determination of 10 PAEs in water-based adhesives using SFC-tandem mass spectrometry with dispersion solid-phase extraction by spherical carbons. Separation of PAEs on a Viridis HSS C18 SB column and the parameters affecting the extraction were evaluated. Good accuracy and precision were obtained with the recoveries at 0.5, 2.0, and 10.0 mg/kg ranging from 82.9 to 99.5% and the intra- and inter-day precision less than 7%. The method had excellent sensitivity with limits of detection in the range of 0.015-0.029 mg/kg. In the 10-500 ng/mL concentration range, the linear correlation coefficients of all compounds were between 0.9975 and 0.9995. The method was applied to the determination of 10 PAEs in actual samples. This method is simple and rapid with low solvent consumption and high extraction efficiency. When applied to the determination of PAEs in actual samples, the method is sensitive and accurate and can meet the batch processing requirements for trace PAEs in water-based adhesives. PAEs in water-based adhesives can be determined using inexpensive materials and simple procedures with SFC.

Classification and Zoning of Improved Materials of Weathered Redbed Soil in China Based on the Integrity of Mud Skin

Natural redbeds are widely distributed throughout China. Ecological restoration entails implementing measures according to the local conditions and obtaining local materials, ensuring ecological environment conservation and restoration in a scientific manner. The mud skin of weathered redbed soil is often used to control soil desertification and repair slope, and its integrity is important to measure the repairing effect. However, most of the materials used for the improvement of weathered redbed soil contain harmful chemicals, bear high costs, and aggravate environmental pollution. At present, the knowledge about different kinds of improvement materials for Chinese different zones is unclear. To solve this problem, we considered naturally weathered redbed soil as the raw material, selected 77 kinds of improved materials, and tested the integrity of the natural redbed weathered soil after adding the improved material; then, we compared it with the natural redbed weathered soil with no added materials. Then, we put forth a classification standard for the materials, discussed the driving environmental factors, formulated the suitable zoning of the materials, and defined the improvement effects of different materials on the weathered redbed soil in different regions of China. The results suggested that, for weathered redbed soil, nano water-based adhesives were most suitable for the south-western, north-western, south-eastern, north-eastern, and northern regions of China and can be widely used in other regions as well. Starch was the least suitable material for the north-western, north-eastern, and northern regions of China. The most unsuitable material for South-West China was larch tannin extract; wormwood straw was the most unsuitable for South-East China. The modified material that was not suitable for use in most zones was starch. Thus, our study provides a concrete scientific basis regarding the effectiveness of different materials in addressing natural hazards caused by weathered redbed soil in China.

Antifungal Activity of Water-Based Adhesives Derived from Pineapple Stem Flour with Apple Cider Vinegar as an Additive.

As a byproduct of bromelain extraction procedures, pineapple stem flour is underutilized. Since water glues derived from gelatinization typically have poor mold resistance, this study aims to produce flour-based value-added products, such as mold-resistant water-based adhesives. To address this issue, this study explored the use of apple cider vinegar (ACV) as a low-cost, non-toxic, commercially available antifungal agent to improve the mold resistance of adhesives. Furthermore, laurate flour was produced via a transesterification of the flour and methyl laurate using a K2CO3 catalyst. Both the unmodified flour and the functionalized flour were employed to prepare water-based adhesives. For both flour systems, adding ACV at concentrations of at least 2.0% v/v enhanced the mold resistance of the adhesives and completely inhibited the development of A. niger mycelia for up to 90 days of storage. The adhesives made from the transesterified flour exhibited a higher shear strength for the paper bonding (ca. 8%) than the unmodified ones. Additionally, the ACV additive had no negative effects on the shear strengths of the water-based adhesives. All of the flour-based adhesives developed in this study had a higher shear strength for paper substrates than two locally available commercial water glues.

Insight into the Molecular Weight of Hydrophobic Starch Laurate-Based Adhesives for Paper.

Instead of using finite petroleum-based resources and harmful additives, starch can be used as a biodegradable, low-cost, and non-toxic ingredient for green adhesives. This work employs K3PO4 catalyzed transesterifications of cassava starch and methyl laurate at varying reaction times (1-10 h), resulting in the enhanced hydrophobicity of starch laurates. At longer reaction times, starch laurates having higher degrees of substitution (DS) were obtained. While starch laurates are the major products of transesterification, relatively low-molecular-weight byproducts (1%) were detected and could be hydrolyzed starches based on gel permeation chromatography results. Contact angle measurements confirmed the relatively high hydrophobicity of the modified starches compared with that of native starch. The modified starches were then employed to prepare water-based adhesives on paper (without any additional additives). Notably, the shear strength of the esterified starch adhesives appears to be independent of the DS of esterified samples, hence the transesterification reaction times. Additionally, the shear strength of water-based adhesives (0.67-0.73 MPa) for bonding to paper substrates is superior to that of two other commercially available glues by a factor of 10 to 80 percent.

Influence of epoxy functional silane on the crosslinking process of eucalyptus wood panels using formaldehyde-free acrylate adhesives

ABSTRACT The effect of different amounts of epoxy functional silane (EFS) as a crosslinking agent in the water-based acrylate adhesives was evaluated for the production of eucalyptus wood panels at different curing temperatures (120°C and 140°C). The thermal stability and dynamic analyses (loss and storage moduli) of the acrylate adhesives with EFS were evaluated. The addition of EFS in the acrylate adhesive increased the thermal degradation, storage, and loss moduli. The thermal degradation, bending test, specific mass, and morphology were evaluated in the wood panels. Significant increases in the storage modulus and bending strength of the wood panels with EFS and acrylate adhesive at 140°C were found. These results demonstrate a potential application of EFS in the production of wood panels aiming towards the manufacture of thicker composites.

Supramolecular interaction enabled preparation of high-strength water-based adhesives from polymethylmethacrylate wastes

The preparation of water-based adhesives with high bonding strength for various substrates is challenging. Moreover, to construct a sustainable society, it is highly desirable to develop a cost-effective way to achieve the reuse of plastic wastes. Herein, using polymethylmethacrylate (PMMA) chemicals or wastes as raw materials, water-based adhesives with high bonding strength for various substrates are prepared through a simple one-step hydrolysis strategy. The adhesives possess the maximum bonding strength of 7.1MPa to iron, 4.2MPa to wood, and ∼1.5MPa to plastics. The adhesives have a world-record bonding strength to metal when compared with that of current reported water-based adhesives. Our method is low cost, simple, environmentally friendly, and suitable for large-scale industrial production. More importantly, using plastic wastes as raw materials opens up a new and low-cost way to turn wastes into valuables, which will greatly contribute to construct a sustainable society.

Effect of quartz sand on mechanical properties of waterborne adhesives

In order to study the influence of quartz sand filler on the properties of water-based adhesives. Brinell rotational viscometer and universal testing machine were used to test the mechanical properties of adhesives incorporated with different particle sizes and different dosages. The test results show that when the particle size is greater than 280μm, the quartz sand is easy to sink to the bottom of the glue, which is not conducive to dispersion. When the dosage is constant, the smaller the particle size of quartz sand, the greater the viscosity of the liquid. The addition of quartz sand can significantly enhance the tensile properties of the adhesive after curing and the crack resistance in low temperature environment.

Turn Waste into Valuable: Preparation of High-Strength Water-Based Adhesives from Polymethylmethacrylate Wastes: A Comprehensive Chemical Experiments

Turn Waste into Valuable: Preparation of High-Strength Water-Based Adhesives from Polymethylmethacrylate Wastes: A Comprehensive Chemical Experiments

Toxicological signature for thyroid endocrine disruption of dichlorooctylisothiazolinone in zebrafish larvae.

Dichlorooctylisothiazolinone (DCOIT), which is one of the isothiazolinone preservatives, is applied to water-based adhesives in food packaging. This study investigated the effects of DCOIT on the embryonic growth and thyroid endocrine system using zebrafish. Organism-level (hatchability, survival, and growth), hormone-level (triiodothyronine (T3) and thyroxine (T4)), gene-level (genes associated with the hypothalamus-pituitary-thyroid axis), and microRNA-level (microRNAs related to thyroid endocrine disruption) endpoints were measured. Significant rise in embryonic coagulation and delayed hatching (≥0.3 μg/L), and decreased larval length (30 μg/L) were observed in fish exposed to DCOIT. Lower contents of T3 and T4 were observed after exposure to DCOIT, which was accompanied by the upregulation of genes associated with the thyrotropin releasing hormone and thyroid stimulating hormone and the downregulation of genes associated with the thyroid hormone receptors and deiodination. Strong influence of DCOIT on dre-miR-193b and -499 may be a critical mechanism to inhibit transcription of trαa and trβ, which in turn may affect thyroid hormones and development of the organism. Our findings suggest that hypothyroidism induced by the exposure to DCOIT is potentially associated with genetic and microRNA-level changes, which eventually affects development.

Engineering of open assembly time of water-based polyvinyl acetate (PVAc) wood adhesives by post-addition of additives

Polyvinyl acetate (PVAc) as a thermoplastic polymer is one of the most common wood adhesive types for interior applications. For the processing of water-based PVAc wood adhesives, certain manufacturer-related parameters such as open and closed assembly time must be considered in order to avoid loss in strength properties of the adhesive joint. As for some applications, the maximum open assembly time is too short, this production-related property can be engineered by adding additives to the PVAc wood adhesive. The aim of this study was to prolong the open assembly time by post-adding different additives to the adhesive. The additives used were water, calcium carbonate, D-sorbitol, fumed silica, glycerine, methylcellulose, poly dextrose, urea, wheat flour and wheat starch. Using a simple in-situ determination method, open assembly time was measured. Additionally, the solid content and the rheological behaviour as well as the mechanical properties and the moisture absorption behaviour from dried adhesive films were determined for characterisation of the additive-PVAc adhesive mixture. A preferred additive would only prolong the open assembly time and would have little to no influence on the remaining parameters investigated. This study showed, that with the post-addition of certain additives to the PVAc adhesive, the desired production-related requirements can be adjusted.

Preparation and characterization of water-based wood adhesive using tamarind seed powder

Adhesives are used all over the world to combine the materials together. Due to its extended usage environment conservation authorities emphasize the importance of reducing the volatile organic content in adhesive manufacturing processes. As a solution, researchers are focusing on water-based adhesives instead of adhesives based on organic solvents. The binders that can be dissolved in water are needed to develop such water-based adhesives. In this study the possibility of using tamarind seed powder as a binder was analyzed. Tamarind seed powder can be used to develop an effective water-based wood adhesive with characteristics compatible with commercial glues. By comparing viscosity, fixture time and bond strength, the minimum initial seed powder concentration for an effective glue was identified as 6.25 %(w/v). In terms of the cost, minimal usage of raw material gives an additional advantage. Therefore 6.25% was selected, as it was the glue with minimum seed powder concentration which showed the above parameters compatible with commercial glues. This will be a green light to adhesive industries to reduce human health hazards and environmental hazards. On the other hand, it will be one of the value addition processes for the tamarind seed waste.<strong></strong>

Influence of polymerizable surfactants on the adhesion performance and water resistance of water-based acrylic pressure-sensitive adhesives (PSAs)

The behavior of different polymerizable surfactants was investigated to improve the water-resistance of pressure-sensitive adhesives (PSAs) based on acrylic acid (AA) and n-butyl acrylate (n-BA). Differences in the adhesion properties were found according to the chemical structure and the critical micelle concentration of the polymerizable surfactant, especially when compared to the non-polymerizable reference surfactant (Dowfax 2A1). The polymerizable surfactants with a branched structure resulted in more gel content and higher glass transition temperature in the adhesive. In general, the peel resistance and tack properties decreased with the use of polymerizable surfactants in the PSA formula. However, increased shear resistance was observed with respect to the PSA adhesive synthesized with the reference surfactant. Furthermore, the adhesives made with higher molecular weight polymerizable surfactants resulted in higher shear elastic modulus, shear strength, and deformation energy than the rest of the PSA adhesives. On the other hand, as expected, all the polymerizable surfactants studied contributed to the improved water resistance of the PSA compared to the reference PSA prepared with a conventional surfactant. The covalent bond formed between the polymer and the surfactant limited the migration of the surfactant towards the air-film interface thus reducing the formation of water entry pathways. The polymerizable surfactants with linear molecular structure showed the best water resistance performance.

Estimation of differences and reapplication effect of peel bond strength between silicone-based and water-based adhesives

Statement of problemRetention is essential for maxillofacial prosthesis. Adhesives are commonly used for retention because of their simplicity, availability, and cost-effectiveness. Studies that have estimated the differences in bond strength between the types of adhesives and the impact of reapplication are sparse. PurposeThe purpose of this observational clinical study was to estimate the peel bond strength and reapplication effects of water-based and silicone-based adhesives at 0, 24, and 48 hours. Material and methodsA total of 46 participants were enrolled, with 23 participants in each adhesive test group—water-based and silicone-based adhesive. Silicone elastomeric strips were attached to the ventral aspect of the participants' forearm 5 cm away from the radial styloid prominence. The strength of each adhesive group was tested at 0 hours, and its reapplication effects were evaluated at 24 and 48 hours. The peel bond strength was estimated by using a universal testing machine, and the data were recorded in N/m and statistically analyzed by the independent Student t test and Spearman rho correlation coefficient tests (α=.05). ResultsThe mean ±standard deviation of peel bond strength at 0 hours for silicone-based adhesive (111.5 ±2.5 N/m) was higher than that for water-based adhesive (99.9 ±3.9 N/m) (P<.001). On reapplication, the silicone-based adhesive had a higher peel bond strength (113.5 ±2.8 N/m) than the water-based adhesive (105.2 ±3.0 N/m) (P<.001). The results were statistically significant between the 2 groups at different time intervals (P=.04). ConclusionsThe mean peel bond strength of the silicone-based adhesive was higher than that of the water-based adhesive. The reapplication of adhesives improved the bond strength in both the groups.