Polyurethane Adhesives Research Articles

Bonding of rubber to steel: Effects of hydroxyl-terminated polybutadiene on the adhesion of waterborne polyurethane adhesives

Rubber as a substrate exhibits very different surface physical and chemical characteristics from steel. It still remains challenging to achieve a complete interface stripping of steel while maintaining double-sided adhesion between rubber and steel. Hydroxyl-terminated polybutadiene (HTPB) possesses remarkable low-temperature flexibility that contributes to migration and orientation of molecular chains, and contains abundant C=C bonds that facilitate cross-linking reaction. In this work, the hydroxyethyl acrylate (HEA)-terminated waterborne polyurethane (WPUH) adhesive was prepared by introducing HTPB into polyurethane backbone. The impact of HTPB on the properties of WPUH adhesive was investigated by changing HTPB/poly(tetramethylene ether) glycol (PTMG) molar ratio. The reasons for such change were studied focusing on the structure and bonding mechanism of WPUH adhesive. When rubber and steel were bonded together by WPUH adhesive, the rubber would induce non-polar HTPB segments to approach the bonding interface while the steel would attract the polar carbamate groups to its surface. The adhesion was strengthened by the interfacial interaction once WPUH adhesive wetted two substrates. In addition, the 1,2-isomer C=C bonds of HTPB could undergo free radical polymerization with HEA to form a cross-linked network, which improved the cohesion. This study provides a feasible strategy for achieving the goal of effectively bonding rubber-to-steel without residual adhesive stripping.

Solvent-free synthesis of bio-based non-isocyanate polyurethane (NIPU) with robust adhesive property and resistance to low temperature

Non-isocyanate polyurethane (NIPU) adhesives represent a cutting-edge advancement in adhesive technology, poised to significantly diminish the dependency on isocyanate-based PU within the industry. In the context of the increasing scarcity of petroleum-based resources and the growing imperative for sustainable environmental practices, the pursuit of a comprehensively sustainable, bio-derived non-isocyanate polyurethane (NIPU) adhesive has swiftly become a pivotal area of interest within the scientific research community. In this study, the cashew phenol cyclic carbonate (CPCC) was synthesized through the addition polymerization process involving cashew phenol glycidyl ether (602A) with carbon dioxide (CO2), followed by a curing step utilizing a diamine extracted from biomass-derived oil to produce bio-based NIPU at ambient temperature. The synthesized NIPU adhesive demonstrated remarkable thermal stability and exceptional adhesion to a variety of substrate materials. Notably, the adhesive showcased superior bonding efficacy at ultra-low temperatures, with steel bonding strength reaching up to 7.78 MPa at −37 °C. This study presents an efficient and accelerated synthesis approach for the preparation of bio-based NIPU, offering a significant contribution to the field. Moreover, it provides a valuable reference for future advancements in NIPU adhesive technology, particularly for the applications requiring robust bonding at low-temperature environments.

Organic-Inorganic Hybrid Nanoparticles for Enhancing Adhesion of 2K Polyurethane to Steel and Their Performance Optimization Using Response Surface Methodology.

Automakers are focusing on lightweight vehicles to address fuel economy and emission challenges and are using high-performance materials such as 2K PU-based joints as alternatives to cast iron, steel, and other metals. This study was conducted with the aim of expanding the application of 2K PU and enhancing its compatibility with steel substrates, which are commonly used in the automotive manufacturing industry, through the use of O-I hybrid nanoparticles containing alkoxysilane groups as additives in the 2K PU formulation. At the same time, the simplified process introduced and examined in this study demonstrates its feasibility for industrial-scale applications; the process offers notable advantages in reducing workload and curing time by eliminating cumbersome surface pretreatment steps before applying the 2K PU layer. Two types of commercial SB PU and EB PU were selected to study the mechanism by which O-I hybrid NPs enhance adhesion when integrated directly into the 2K PU formulation. We optimized various input parameters through practical work and modeling using the response surface method. These parameters included the amounts of AFAP precursor, APTES, and butylene glycol (BG) and the mixing ratio of O-I hybrid NPs in the formulations of two commercial PUs. The results show that O-I hybrid NPs significantly enhance adhesion, increasing performance on stainless surfaces by up to 2.35 times compared to pristine EB and SB PU. Notably, the SB PU's performance can improve up to 2.5 times according to the RSM predictions, highlighting the substantial impact of O-I hybrid NPs.

Synthesis and Characterization of Rebondable Polyurethane Adhesives Relying on Thermo-Activated Transcarbamoylation.

Dynamic polymer networks combine the noteworthy (thermo)mechanical features of thermosets with the processability of thermoplastics. They rely on externally triggered bond exchange reactions, which induce topological rearrangements and, at a sufficiently high rate, a macroscopic reflow of the polymer network. Due to this controlled change in viscosity, dynamic polymers are repairable, malleable, and reprocessable. Herein, several dynamic polyurethane networks were synthetized as model compounds, which were able to undergo thermo-activated transcarbamoylation for the use in rebondable adhesives. Ethylenediamine-N,N,N',N'-tetra-2-propanol (EDTP) was applied as a transcarbamoylation catalyst, which participates in the curing reaction across its four -OH groups and thus, is covalently attached within the polyurethane network. Both bond exchange rate and (thermo)mechanical properties of the dynamic networks were readily adjusted by the crosslink density and availability of -OH groups. In a last step, the most promising model compound was optimized to prepare an adhesive formulation more suitable for a real case application. Single-lap shear tests were carried out to evaluate the bond strength of this final formulation in adhesively bonded carbon fiber reinforced polymers (CFRP). Exploiting the dynamic nature of the adhesive layer, the debonded CFRP test specimens were rebonded at elevated temperature. The results clearly show that thermally triggered rebonding was feasible by recovering up to 79% of the original bond strength.

Phase change thermal interface film with bicontinuous and textured filler network for efficient wearable heat dissipation

Wearable thermal management needs to simultaneously meet thermal conductivity, heat storage capacity, stability, flexibility, and economy, but these characteristics constrain each other in the development of phase change thermal interface materials (PhC-TIM). Therefore, relying on the economic bicontinuous structure for fillers’ orientation, a new type of bicontinuous phase change thermal interface material (BPTIM) was designed, which includes thermal storage phase composed of paraffin (PCMs) and flexible molecule styrene–butadiene–styrene (SBS), and thermal conductivity phase composed of adhesive polyurethane (PU) and thermal conductive medium boron nitride (h-BN). In the experiment, shear force generated by stirring and optimized two-phase volume ratio resulted in the stretching and compressing of the thermal conductive phase, promoting the orientation of h-BN and ultimately forming a textured thermal-conductive network in a high PCMs content bicontinuous structure. Moreover, the introduction of SBS had brought bending resistance and thermal stability. These characteristics enabled BPTIMs to significantly reduce the surface temperature of the wearable device by 23 °C. Overall, this design provides a certain reference for the widespread application of PhC-TIM in thermal management of wearable electronic products.

Numerical Investigation of Fracture Behaviour of Polyurethane Adhesives under the Influence of Moisture.

The mechanical behaviour of polymer adhesives is influenced by the environmental conditions leading to ageing and affecting the integrity of the material. The polymer adhesives have hygroscopic behaviour and tend to absorb moisture from the environment, causing the material to swell without applying external load. The focus of the work is to investigate the viscoelastic material behaviour under ageing conditions. The constitutive equations and the governing equations to numerically investigate the fracture in swollen viscoelastic material are discussed to describe the numerical implementation. Phase-field damage modelling has been used in numerical studies of ductile and brittle materials for a long time. The finite-strain phase-field damage model is used to investigate the fracture behaviour in aged viscoelastic polymer adhesives. The finite-strain viscoelastic model is formulated based on the continuum rheological model by combining spring and Maxwell elements in parallel. Commercially available post-cured crosslinked polyurethane adhesives are used in the current investigation. Post-cured samples of crosslinked polyurethane adhesives are prepared for different humidity conditions under isothermal conditions. These aged samples are used to perform tensile and tear tests and the test data are used to identify the material parameters from the curve fitting process. The experiment and simulation are compared to relate the findings and are the first step forward to improve the method to model crosslinked polymers.

Closing the loop of polyurethane adhesives: Acidolysis process optimization

Polyurethane adhesive (PUA) are a specialized application of polyurethanes. Acidolysis of PUA waste yield a recycled polyol with tunable properties. This process was optimized by response surface methodology to predict the domain of parameters where the lowest of viscosity, hydroxyl, and acid values could be achieved. Relationships between temperature, polyurethane-to-polyol, and polyurethane-to-acid ratios, and viscosity, molecular weight, hydroxyl and acid values were established and optimal conditions were validated for a robust process. The polyurethane-to-acid ratio had the most significant influence on the acid value of the product. Hydroxyl value, viscosity and molecular weight were primarily affected by the polyurethane-to-polyol ratio. Using a recycled polyol obtained at 205 °C, a polyurethane-to-polyol ratio of 1.4 kg/kg, and a polyurethane-to-acid ratio of 50 kg/kg, we successfully produced a new adhesive incorporating up to 28 % recycled material. This demonstrated adhesion properties for wood applications on par with those of virgin adhesives, without experiencing crash phenomena.

Plant Design for the Production of Propylene Oxide by Isopropylbenzene 2-phenylpropane, or (1-Methylethyl) Benzene (Cumene)

Cumene is a colorless, volatile liquid with a gasoline-like odor. It’s also known as isopropylbenzene, 2-phenylpropane, or (1-methylethyl) benzene. It’s a natural component of coal tar and crude oil, and it can also be employed in gasoline as a blending component. Cumene hydroperoxide is produced by oxidizing cumene with benzene and propylene in the presence of air. As a result, the cumene hydroperoxide is changed to cumyl alcohol, which is then transformed to propylene without the use of oxygen. Propylene oxide is an organic compound produced through various methods such as the cumene process and the hydroperoxide process. The cumene method is preferred due to its low by-product production and high market value of co-products. The reactive distillation process is a feasible method for producing propylene oxide with high purity and reduced costs. Future work includes optimizing processes, developing new catalysts, and improving efficiency. Propylene oxide has practical applications in the production of polyurethane foams, coatings, adhesives, polyether polyols, and propylene glycols.

Exploring Bio-Based Polyurethane Adhesives for Eco-Friendly Structural Applications: An Experimental and Numerical Study.

In response to heightened environmental awareness, various industries, including the civil and automotive sector, are contemplating a shift towards the utilization of more sustainable materials. For adhesive bonding, this necessitates the exploration of materials derived from renewable sources, commonly denoted as bio-adhesives. This study focuses on a bio-adhesive L-joint, which is a commonly employed configuration in the automotive sector for creating bonded structural components with significant bending stiffness. In this investigation, the behavior of joints composed of pine wood and bio-based adhesives was studied. Two distinct configurations were studied, differing solely in the fiber orientation of the wood. The research combined experimental testing and finite element modeling to analyze the strength of the joints and determine their failure mode when subjected to tensile loading conditions. The findings indicate that the configuration of the joint plays a crucial role in its overall performance, with one of the solutions demonstrating higher strength. Additionally, a good degree of agreement was observed between the experimental and numerical analyses for one of the configurations, while the consideration of the maximum principal stress failure predictor (MPSFP) proved to accurately predict the location for crack propagation in both configurations.

Application of microscale methods to study the heat-induced delamination in engineered wood products bonded with one-component polyurethane adhesives

One-component polyurethanes (1-c-PUR) are commonly used adhesives for the manufacture of cross-laminated timber (CLT). Typically, these adhesives do not govern the mechanical response of CLT under normal service temperatures. However, when subjected to heating from a fire, failures may transition from within the timber to the bond line interphase zones. CLT bonded with 1-c-PUR has been shown to be prone to heat induced delamination (HID), which may compromise its structural performance at elevated temperatures. Thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and dynamic thermo-mechanical analysis (DTMA) were used to study the thermal and thermo-mechanical responses of engineered wood products and components (i.e. adhesives and timber) and their interphase (i.e. bond line). Two commercially available 1-c-PUR adhesive films from the same manufacturer, two timber species (Norway Spruce and Radiata Pine, as sawdust or as veneers), and four different veneer shear lap combinations, were studied. Shear lap specimens bonded with a conventional 1-c-PUR adhesive consistently experienced bond line mechanical failure in DTMA at about 220–240 °C. The same adhesive films tested via DSC and TGA softened at 240–260 °C. Conversely, a different 1-c-PUR adhesive, formulated specifically for enhanced performance at elevated temperature, displayed no detectable softening in DSC and TGA, and shear lap specimens in DTMA consistently failed within the timber; even at elevated temperatures. The presented thermo-mechanical methods allow identification of failure modes and temperatures, whilst the thermal microscale methods (i.e. TGA, DSC, DTMA) assist in understanding the various factors contributing to failures.

Thermal behavior of adhesively bonded timber‐concrete composite slabs subjected to standard fire exposure

AbstractFire tests were performed for the first time on adhesively bonded timber‐concrete composite slabs. The two medium‐scale (1.8 × 1.25 m) slabs were produced by gluing an 80‐mm thick three‐layer cross‐laminated timber (CLT) board to a 50 mm thick prefabricated reinforced concrete (RC) slab with epoxy and polyurethane (PUR) adhesives, respectively. The behavior of the composite slabs under elevated temperature was monitored by (1) observing the burning behavior of the used CLT, for example, charring and delamination and (2) measuring the temperature development at different locations of the CLT slabs, in the adhesive bond between concrete and timber boards, and in RC slabs. It was found that employing a one‐dimensional charring model for pure softwood, as prescribed by Eurocode 5‐1‐2, underestimated the charring depth of CLT due to the delamination effects. Measurements revealed that the average charring rates in the middle layer of CLT panels were approximately 0.65 mm/min, suggesting that the presence of concrete does not significantly affect the thermal behavior of the CLT panel. Delamination within the CLT was observed when its adhesive temperature was around 230°C. It was followed by the free‐fall of delaminated wood plies, which progressed slowly and lasted until the end of the test. At 90 min into the test, the temperatures of epoxy at the nine locations ranged between 55°C and 130°, while that of PUR between 60°C and 100°. The adhesive between concrete and CLT could lose stiffness significantly along the rising of temperature after surpassing of glass transition temperature (58°C for epoxy and 23°C for PUR in this study). The results indicated a high risk of weakening the composite action between the concrete slab and timber board. The measured temperatures of steel rebar were lower than 50°C. However, the concrete temperature reached about 120°C and the concrete cracked due to the distinct thermal expansions between concrete and timber and the rigid constraint of adhesive bond.

Strength and Ultrasonic Testing of Acrylic Foam Adhesive Tape

Adhesive joints are some of the oldest inseparable connections, and were used much earlier than other non-separable connections (e.g., welded, soldered). Adhesives are widely used in the manufacture of vehicles, household appliances, aircraft, and medicine. One disadvantage of adhesive joints is their long bonding time (amounting, for example, to 72 h for polyurethane adhesives used in bus roof bonding), and another is their production of harmful waste. Tapes that are adhesive coated on both sides are increasingly being used to join parts during production. Such tapes have lower strength than traditional adhesives, but their bonding time is much shorter. In addition, the amount of waste remaining after production is minimized. Tapes, like adhesives, dampen vibrations well and seal the materials being joined. The purpose of this study was to evaluate the influence of selected factors on the quality of tape–steel sheet joints and to assess the possibility of testing acrylic tape–steel sheet joints using ultrasonic methods. It was found that the preparation of a surface for bonding has a significant effect on the quality of the joint, and it was confirmed that non-destructive evaluation of the quality of the tested joints by the ultrasonic method is possible. The decibel drop in the height of the first and fifth pulses obtained on the screen of the ultrasonic defectoscope was proposed as an ultrasonic measure. The highest-quality joints were characterized by a measure in the range of 12 dB, lower-quality areas of about 8 dB, and tape-free areas of about 5 dB. At the same time, it was noted that in the case of proper surface preparation, there was cohesive failure of the joint during breakage.

Improving the adhesion of satin XPS to sandstone with customized polyurethane adhesives for sustainable facade cladding and thermal insulation

Six PU adhesives were synthesised with two different polyols (PPG and PEG based) of three molecular weights, namely 400, 1000 and 2000 g mol−1, and MDI, to prepare sandstone-XPS isolating façade panels. The chemical structure, thermal properties, and adhesion properties in the preparation of the panels were evaluated. Both sandstone and XPS are commonly used materials in construction due to their excellent insulating properties, durability, flexibility, water resistance, and aesthetic appeal, making them environmentally attractive. The industry trend is towards using sanded XPS in these panels, as better adhesion is achieved with typical adhesives compared to satin or unsanded XPS. However, this entails waste generation from sanding, a higher panel price and a difference in adhesive consumption from 309 g m−2 to 684 g m−2 for unsanded (or satin) and sanded XPS, respectively. In this study, all prepared panels exhibit good adhesion properties, even those made with satin XPS. Panels prepared from PPG-based adhesives show better adhesion performance than those made from PEG, reaching 0.52 ± 0.07 N mm−2 with the 1000 g mol−1 PPG polyol-based adhesive. These highest adhesion properties are due to the optimal balance of flexible and rigid segments in the polymer material structure. The adhesive maintains its high performance even after harsh temperature and humidity conditions. After accelerated ageing with heat, cold and water, the probes retain between 65 and 71 % of the original tensile strength (0.34 ± 0.03, 0.35 ± 0.07 and 0.37 ± 0.01 N mm−2, respectively). This finding suggests an interesting starting point for cost savings associated with sanding and reduction in XPS waste generation, making them economically and environmentally appealing.

Development of biodegradable bioadhesive nanocomposites reinforced with quantum dots and functionalized carbon nanotubes

A series of photoluminescent nanocomposite polyurethane adhesives were elaborated from a chemoenzymatic prepared diol of caprolactone (PCL-diol) and ethylene glycol with an excess of two different isocyanates: i) hexamethylene (HDI) and (ii) isophorone (IPDI)) diisocyanates. Adhesive formulations were filled with functionalized poly(amido-amine) (PAMAM) carbon nanotubes (f-MWNTs) and carbon quantum dots (CQDTs). Dry swine gut was used as substrate and mechanical tests were performed to explore the performance of the adhesives. The obtained materials were characterized by infrared spectroscopy (FT-IR), energy surface by contact angle, differential scanning calorimetry (DSC), hydrolytic degradation, and mechanical testing under tension, lap shear, T-peel, wound closure, and burst pressure. Among the main results were the formation of covalent bonds between the substrate and the adhesive, and the fact that the mechanical strength of the nanocomposite adhesives was superior to that of the unfilled adhesives. Compatibility of nanocomposites with the substrate was achieved by increasing wettability by the incorporation of both nanofillers. Also, adhesives filled with only CQDTs and with MWNTs-CDQTs combined showed photoluminescence activity under ultraviolet light.

Synthesis of High Mechanical Strength and Thermally Recyclable and Reversible Polyurethane Adhesive by Diels–Alder Reaction

AbstractRecyclability of polyurethane materials is significant to relieve environmental problems caused by damaged polymers. Inspired by plenty of self‐healing properties based on dynamic covalent bonds. A high mechanical strength and thermally reversible polyurethane adhesive are acquired through co‐polymerization of poly‐1,4‐butylene adipate glycol (PBA), soybean oil‐based polyol (MESO), and toluene diisocyanate (TDI) whose linear polymer chains are constructed by Diels–Alder reaction between furfuryl alcohol (FA) and bismaleimide (BMI), named DAPU. Further, the obtained polyurethane adhesives show great recyclability, mechanical performance (Whose tensile strength can reach 91.7 MPa), and appropriate self‐healing ability through the thermally reversible Diels–Alder covalent bonds and hydrogen bonds between urethane groups, which may pave a way for further development of recyclable materials.

Development and Application of a Lignin-Based Polyol for Sustainable Reactive Polyurethane Adhesives Synthesis.

In response to the environmental impacts of conventional polyurethane adhesives derived from fossil fuels, this study introduces a sustainable alternative utilizing lignin-based polyols extracted from rice straw through a process developed at INESCOP. This research explores the partial substitution of traditional polyols with lignin-based equivalents in the synthesis of reactive hot melt polyurethane adhesives (HMPUR) for the footwear industry. The performance of these eco-friendly adhesives was rigorously assessed through Thermogravimetric Analysis (TGA), Differential Scanning Calorimetry (DSC), rheological analysis, and T-peel tests to ensure their compliance with relevant industry standards. Preliminary results demonstrate that lignin-based polyols can effectively replace a significant portion of fossil-derived polyols, maintaining essential adhesive properties and marking a significant step towards more sustainable adhesive solutions. This study not only highlights the potential of lignin in the realm of sustainable adhesive production but also emphasises the valorisation of agricultural by-products, thus aligning with the principles of green chemistry and sustainability objectives in the polymer industry.

Sulfur-modified polyurethane adhesives: Green synthesis process and disassembly-responsive characteristics

Polyurethane adhesives have been widely used in industrial production and daily life for their excellent properties. With the urgent need for social progress, the intelligent responsiveness of polyurethane adhesives has become more and more important. Here, we demonstrate a stimulus-responsive polyurethane adhesive. Starting from the structural design, sulfur (S8) is added into the polyurethane adhesive for the first time using the inverse vulcanized mechanism, and the controllable disassembly response of the polyurethane adhesive under the condition of thermal stimulation is realized. In addition, the stimulus response of the adhesive can also be activated through the permeation process of methoxide anion (CH3O−), and the rapid disassembly response property is displayed in the methanol solution of CH3ONa, to realize the recovery of the bonding substrate. Simultaneously, the implementation of the inverse vulcanized mechanism imparts the adhesive with a diminished water absorption swelling rate and heightened cross-link density. On the surface of the metal substrate, it shows excellent bonding properties, with a lap shear adhesion strength reaching 2.8 MPa. It is worth noting that the adhesive also exhibits excellent underwater durability. After 36 h of underwater soaking treatment, its adhesion can still be maintained at 2.4 MPa. This work reveals the mechanism of rapid disassembly of polyurethane adhesives at the molecular level. By density functional theory (DFT) calculation, it is found that the minimum bond energy of the S-S bond in a polyurethane adhesive system is 134 KJ·mol−1, and the disassembly response can be triggered by heating to 53.79℃. At the same time, the mechanism of the disassembly response induced by CH3O− is further analyzed using an electrostatic potential (ESP) diagram. This work utilizes sulfur (S8) and castor oil (CO) as raw materials, which can be sourced from industrial or agricultural by-products. It breaks away from traditional polyurethane adhesive preparation methods and offers a "green" strategy that can be synthesized through a solvent-free one-pot process, thus providing a new way of thinking about obtaining sustainable polymers from industrial and agricultural by-products.

Eco-Friendly and High-Performance Bio-Polyurethane Adhesives from Vegetable Oils: A Review.

Current petrochemical-based adhesives adversely affect the environment through substantial volatile organic compound (VOC) emissions during production, contributing to air pollution and climate change. In contrast, vegetable oils extracted from bio-resources provide a compelling alternative owing to their renewability, abundance, and compatibility with adhesive formulation chemistry. This review aimed to critically examine and synthesize the existing scholarly literature on environmentally friendly, sustainable, and high-performance polyurethane adhesives (PUAs) developed from vegetable oils. The use of PUAs derived from vegetable oils promises to provide a long-term replacement while simultaneously maintaining or improving adhesive properties. This quality renders these adhesives appropriate for widespread use in various sectors, including construction, automotive manufacturing, packaging, textile, and footwear industries. This review intended to perform a comprehensive assessment and integration of the existing research, thereby identifying the raw materials, strengths, weaknesses, and gaps in knowledge concerning vegetable oil-based PUAs. In doing so, it responded to these gaps and proposes potential avenues for future research. Therefore, this review accomplishes more than merely evaluating the existing research; it fosters the advancement of greener PUA technologies by identifying areas for improvement and innovation towards more sustainable industrial practices by showcasing vegetable oil-based PUAs as viable, high-performance alternatives to their petroleum-based counterparts.

A discussion on the various aspects of the minimum pressing time for polyurethane adhesives

ABSTRACT For many purposes related to the bonding of wood substrates, one-component polyurethane adhesives (1C-PUR) are of great significance. 1C-PUR adhesives are widely used, especially in the cross laminated timber (CLT) production. One major benefit is their ability to be pressed at room temperature. However, not only pressing temperature but also the pressing time is an important economic aspect for manufacturers. Knowing the minimum possible press time offers an economic advantage, however, there have been only few publications on this topic so far. The aim of this work was to investigate and evaluate various aspects of a 1C-PUR adhesive with regard to the minimum pressing time comparing newly developed knowledge-based approaches. The analysis included the strength development of the advanced curing of the adhesive, the development of the final internal bond strength and the minimum required press time for bonded joints to withstand imposed stress. The influence of the wood moisture content and closed assembly time were also investigated. The present study found that closed assembly time had a favourable influence on the required press time period. With immediate testing of the glued joint it also revealed a quicker strength development with lower strength values at a higher wood moisture content.

Biobased Polyurethane Adhesives Derived from Vegetable Oil and Rosin for Flexible Packaging Applications

Biobased Polyurethane Adhesives Derived from Vegetable Oil and Rosin for Flexible Packaging Applications