T-peel Strength Research Articles

Cleaner technologies to minimise the environmental footprint of the footwear bonding process

Advances in cleaner technologies have a critical role in reaching Europe’s climate and environmental goals. More precisely, in the case of the footwear bonding process its environmental impact is mainly related to the VOCs emissions resulting from the use of organic solvents in the most common adhesives used, as well as during the application of some surface treatments such as halogenation. Moreover, the use of raw materials of fossil origin also contributes to its carbon footprint. The aim of this work is to deploy cleaner technologies to minimise the environmental footprint of the footwear bonding process through several approaches at different steps of the process life cycle, also to contribute to footwear circularity. This work focuses on the synthesis and application of reactive hot melt polyurethanes from CO2-based polyols as biobased adhesives, and the study of plasma-based surface treatments (low-pressure plasma and atmospheric pressure plasma) to improve adhesion properties, using styrene-butadiene vulcanised (SBR) rubber as a representative footwear soling material. The influence of CO2-based polyols on the polyurethane structure and the physicochemical effects of the plasma treatments on the rubber surface, as well as the final adhesion properties have been evaluated by means of different experimental techniques. The results showed that the values obtained for the T-peel strength of the adhesive joints studied, with the combination of the application of the plasma surface treatments and the biobased reactive hotmelt, exceed the minimum quality requirements for footwear according to the standardised tests. As a result, the deployment of such cleaner technologies regarding adhesives and surface treatments in the footwear bonding process will contribute to improving footwear carbon footprint and its circularity.

Efficient Physical Mixing of Small Amounts of Nanosilica Dispersion and Waterborne Polyurethane by Using Mild Stirring Conditions

Good dispersion of nanosilica particles in waterborne polyurethane was obtained by mild mechanical stirring when 0.1-0.5 wt.% nanosilica in aqueous dispersion was added. The addition of small amounts of nanosilica produced more negative Z-potential values, increased the surface tension and decreased the Brookfield viscosity, as well as the extent of shear thinning of the waterborne polyurethane. Depending on the amount of nanosilica, the particle-size distributions of the waterborne polyurethanes changed differently and the addition of only 0.1 wt.% nanosilica noticeably increased the percentage of the particles of 298 nm in diameter. The DSC curves showed two melting peaks at 46 °C and 52 °C, as well as an increase in the melting enthalpy. In addition, when nanosilica was added, the crystallization peak of the waterborne polyurethane was displaced to a higher temperature and showed higher enthalpy. Furthermore, the addition of 0.1-0.5 wt.% nanosilica displaced the temperature of decomposition of the soft domains to higher temperatures due to the intercalation of the particles among the soft segments; this led to a change in the degree of phase separation of the waterborne polyurethanes. As a consequence, improved thermal stability and viscoelastic and mechanical properties of the waterborne polyurethanes were obtained. However, the addition of small amounts of nanosilica was detrimental for the wettability and adhesion of the waterborne polyurethanes due to the existence of acrylic moieties on the nanosilica particles, which seemed to migrate to the interface once the polyurethane was cross-linked. In fact, the final T-peel strength values of the joints made with the waterborne polyurethanes containing nanosilica were significantly lower than the one obtained with the waterborne polyurethane without nanosilica; the higher the nanosilica content, the lower the final adhesion. The better the nanosilica dispersion in the waterborne polyurethane+nanosilica, the higher the final T-peel strength value.

Robotised atmospheric plasma treatment to improve the adhesion of vulcanised and thermoplastic rubber materials for a more sustainable footwear

Surface treatment is essential to ensure the resistance and durability of adhesive upper-to-sole joints for footwear. This study investigates robotised atmospheric pressure plasma technology to increase adhesion on styrene-butadiene vulcanised (SBR) and styrene-butadiene-styrene thermoplastic (SBS) rubbers, which constitutes a more sustainable surface treatment as an alternative to solvent-based chemical treatments (i.e., halogenation). In this work, the different parameters such as application speed and distance of the nozzle of the atmospheric plasma system have been optimised and the effects of the plasma treatment on the physicochemical properties in the materials’ surface, roughness, wettability, as well as the adhesion properties have been evaluated by means of different experimental techniques: Fourier Transform Infrared Spectroscopy (FTIR), X-Ray Photoelectron Spectroscopy (XPS), Field Emission Scanning Electron (FESEM), Contact Angles (CA) and Surface Free Energy (SFE) measurements and T-peel strength tests. The results show that the values obtained for the T-peel strength of the reactive hot melt polyurethane adhesive (HMPUR) joints studied exceed the minimum quality requirements for footwear according to standardised tests. In consequence, the optimisation and validation of operating plasma conditions and adhesion properties of rubbers could consolidate atmospheric plasma as a solvent-free alternative for the preparation of footwear soling materials. The great advantage of this technology is its introduction into the production line by fully automating the bonding process with the use of robots.

Biomass upcycling of waste rPET to higher-value new-easy-recyclable microcellular thermoplastic (co)polyamide foams and hot-melt adhesives

Poly(ethylene terephthalate) (PET) is one of the extremely used fossil-based products in the chemical industry, accounting for about 13% of the world's production. Today, most PET waste accumulates in landscapes or the environment, causing severe pollution. From the perspective of sustainability, scientists have tried to recycle waste PET through chemical and mechanical methods. Mechanical recycling offers some limitations because of the properties of the final product decrease from the second cycle. Rather, chemical recycling has attracted much attention because it can selectively convert plastic waste into high-value-added products including fuel, monomer, and refinery feedstock. Therefore, in this study, the chemical depolymerization of PET was investigated experimentally. After successfully deconstructing waste PET into polymerizable N1, N4-bis(6-aminohexyl)terephthalamide (BAHT) monomer, the obtained BAHT was combined with a bioderived dimer fatty acid (DA; renewable content 100%) building block for the synthesis of bio-based thermoplastic (co)polyamides (TPCPAs) via solvent-free melt polycondensation. The obtained TPCPAs underwent a scCO2 foaming process to give the higher value-added microcellular foams. Interestingly, scCO2 foaming has zero formamides, which meets the safety requirements and is suited to commercial uses. Moreover, TPCPA foams showed an excellent shape recovery property and recyclability due to the entangled DA structure. Adhesive tests also show that TPCPAs exhibit a higher Tpeel strength (185.2 N/cm–420.5 N/cm) than commercial PA glues. This strategy to recycle PET into value-added biomass TPCPAs has a promising application prospect.

NOVEL METHOD OF BREAKING DOWN RUBBER MOLECULES USING PEPTIZER AND THE PROPERTIES OF RESULTANT NATURAL RUBBER SOLVENT-BASED ADHESIVE

The huge cost of energy associated with the breaking down of high molecular weight rubber during adhesive production has placed a demand for alternative processing technology. In this study, the use of benzoyl peroxide as a peptizer to lower the molecular weight of natural rubber has been reported. The properties of natural rubber-based solvent adhesive produced by mechanical mastication and peptizer were also compared. Natural rubber (NR) was masticated in a two-roll mill at 80oC for 30 mins and was processed into adhesive using xylene as solvent. Similarly, adhesives were formulated by chemical break down of the heavy natural rubber molecules using benzoyl peroxide as peptizer. The peptizer loading was varied from 0.2 – 1.0 parts per hundred rubber (phr) of rubber at 100oC in a water bath while other compounding additives were kept constants for all samples under study. The adhesives produced were subjected to the following test: viscosity, lap shear test, T-peel test and drying time test. Other properties studied are weathering resistance, heat resistance and effect of moisture on the adhesives bond on different substrates. The result shows that the viscosity of the adhesives increases with increasing peptizer loading and the masticated sample has a viscosity slightly lower than that of 0.8phr and 1.0phr peptizer loading. Furthermore, T-peel test shows that 0.4 phr peptizer loading has a better average T-peel strength for the bonds while the masticated sample had the least average T-peel strength when compared with all samples. The sample with 1.0phr peptizer loading had the least decrease in shear strength while the 0.2 peptizer loading had the maximum decrease in shear strength. Finally, the FT-IR spectra shows similarities in spectra but with difference in the intensity of the peaks, indicating the ability of the benzoyl peroxide to effectively oxidize the natural rubber as compared with the mechanical masticated sample. The peak of 1080 cm-1 in the peptized sample indicates a major difference with the spectra of mechanical masticated sample. Generally, the benzoyl peroxide effectively lowered the molecular weight of the natural rubber which is evident in the viscosity, reduced process time and ease of the adhesive formulation.

Design of asymmetric-adhesion lignin-reinforced hydrogels based on disulfide bond crosslinking for strain sensing application

Soft and elastic polymer hydrogel materials are booming in the fields of wearable biomimetic skin, sensors, robotics, and bioelectrodes. Currently, many researchers are exploring new chemistries for the preparation of hydrogels to improve their performance. In the present study, we design and develop a strategy to prepare lignin reinforced hydrogels based on disulfide bond crosslinking mechanisms, and resultant hydrogels exhibit excellent stretchability, with tensile strain of up to 1085.4%, and high adhesion (with the highest T-peel strength of up to 432.2 N/m to pigskin). The underlying mechanism is based on the disulfide bonds that act as crosslinkers in the as-prepared hydrogel, and they can be easily cleaved and re-formed under mild conditions. Thanks to the presence of lignin, the as-obtained hydrogels also have excellent UV shielding effect. When assembled into a strain sensor, they can output stable and sensitive sensing signals, with gauge factor (GF) of 2.72 (strain: 0–72.8%). Furthermore, a simple and effective strategy to construct asymmetric adhesive hydrogels was adopted, which is based on directional soaking of the top portion of the hydrogel in a high-concentrated calcium chloride solution. The asymmetric hydrogel strain sensor transmits accurate and stable signals without the interference of various contaminants.

Preparation and Characteristic of Polyurethane Powder Adhesives with Heating Resistance Modified by Nanosilica

Polyurethane powder adhesives (PPAs) have a great application prospect in various areas. However, the weakly adhesion property at high temperature greatly hindered its application. In this study, nanosilica as reinforcing agent and dispersing agent has been introduced during the preparation of PPAs. A series of the polyurethane powder adhesives modified by nanosilica were prepared and the influence of adding order of nanosilica on the heat resistance and adhesive strength properties of PPAs has been investigated. The results showed that the T-peel strength of most samples after second heat (heated at 70°C for 24 hours) decreased about 60-80% comparing with the original T-peel strength. However, PPSY only decreased 17.5%, which indicated the nanosilica added after the chain extension reaction, in the prepolymer synthesis could increase the heat resistance performance of polyurethane powder adhesives. It also means the nanosilica was doped between the PU chains keeping the original form as enhancement reagent adding the nanosilica after the chain extension reaction. The excellent heat resistance performance of PPSY could meet the requirements of the industrial gluing in the fields of footwear.

Adhesive and Impact-Peel Strength Improvement of Epoxy Resins Modified with Mono and Diamine Functionalized Elastomers

Epoxy resins are widely applied in the automotive and electronic industries. However, pure epoxy resins are brittle and thus possess poor mechanical properties. Herein, we report a facile method for improving the impact-peel and adhesive strengths of epoxy resins via the incorporation of two different types of polyether amines (monoamine-based and diamine-based prepolymers). A comparative study was performed to investigate the potential advantages of incorporating a prepolymer into an epoxy resin matrix. It was discovered that the incorporation of a diamine prepolymer significantly improved the impact-peel strength of the epoxy resin system at low (-40°C) and room (23°C) temperatures. For 15 wt% adhesive loading, the diamine prepolymer-based epoxy system demonstrated a 130% (low temperature) and 32% (room temperature) higher impact-peel strength than the monoamine prepolymer-based epoxy system. Moreover, the 15 wt% diamine prepolymer-based epoxy system exhibited a significantly improved shear strength (~36 MPa) and T-peel strength (260 N/25 mm) owing to the effectively reduced crack propagation and cohesive interactions between the epoxy molecules. Our results suggest that the modification of epoxy resins with an appropriate amount of mono and diamine-functionalized elastomers provides a novel route for the development of highly efficient adhesive materials for various applications.

Orthogonal experiments and bonding analysis of ultrasonic welded multi-strand single core copper cables

The join demand for multi-strand single core copper cables in battery packs is increasing vigorously for new energy vehicles. In this paper, the influences of ultrasonic welding parameters on the microstructure, gap fraction and T-peel strength of the copper cable joints were studied systematically by orthogonal experiments. Under the optimum combination of parameters (welding time = 0.8 s, pressure = 4 bar, amplitude = 62.4 μm), a contact joint with low gap fraction of 2.07% was obtained and the maximum T-peel force reached 432.9 N. The T-peel fracture characterized by dimples indicates that metallurgical bonding was formed between copper wires, rather than simple mechanical interlock. Furthermore, the electron backscattered diffraction (EBSD) technology was used to analyze grain boundary types and texture evolution during ultrasonic welding. After ultrasonic welding, continuous 〈111〉 texture and lots of large angle grain boundaries (LAGBs) that composed of high-density dislocations and substructure were found in bonding interfaces of copper wires, which indicates that serious plastic deformation has occurred in bonding region. When interfacial temperature of cables joints provides enough energy for dislocations motion and rearrangement, the dislocations and substructure nucleate and grow into equiaxed grains through the process of copper recrystallization under high interfacial temperature, which promotes the formation of new interfaces between the copper wires.

SURFACE AND ADHESION PROPERTIES OF URETHANE ACRYLATE GRAFT COPOLYMERS

A solvent –based adhesive in which a continuous phase includes a solvent for an acrylic based adhesive or a solvent for a urethane based adhesive and wherein adhesive molecules and dissolved in the solvent to form said continuous phase, the adhesive being characterised in in that adhesive molecules include graft polymer where in a major partof the molecule is either acrylic based or urethane based such that the major part is of sufficient size to provide the adhesive molecule with a required solubility in said solvent and wherein a minor part of the molecule is based on the other of said acrylic or urethane thereby providing said molecule with attributes of both acrylic based and urethane based adhesives.Adhesion increased as the content of urethane macromonomers (UMs) increased in graft copolymer. The graft copolymer prepared using a high UM feed for both PMMA and PnBMA showed improved in adhesion compared to the pure methacrylate polymers. The adhesion was better whether for leather and for vinyl. Surface and adhesive properties were improved as the amount of UM content increased in the graft copolymer. Smaller contact angles result giving a surface with a higher surface energy and increase in T-peel strength was observed as the amount of UM content increased in the graft copolymer.

Bio-Inspired Gelatin-Based Adhesive Modified with Waterborne Polyurethane on Click Chemistry

As a non-toxic, highly reactive biomass material, gelatin is wildly used as the component of biomass-based adhesive. However, like most aqueous adhesives, gelatin-based adhesives suffer from long solidifying time or high solidifying temperature due to the low volatility of water, which highly limits the application potential of gelatinbased adhesives. Inspired by the fast adhesion of marine organisms through the formation of chemical crosslinks, herein, a kind of low temperature curable eco-friendly gelatin-based adhesive with good adhesive properties and fast curing at low temperature is developed by introducing clicking chemical Diels-Alder (DA) reaction between blocked waterborne polyurethane (MWPU) and gelatin. The furfuryl glycidyl ether (FGE) and 4-Maleimidophenol (4-HPM) for the DA reaction are grafted on gelatin, and the end-capping of MWPU, respectively. With the addition of MWPU and FGE, the cross-linking degree of gelatin increased, and the adhesion properties of the adhesive were improved. The shear strength and T-peel strength of the modified adhesive reached 0.95 MPa and 1.42 N/mm, respectively, after the curing time of 8 min at 40°C, which can meet the application requirements as adhesive for bio-medical use.

Influence of biobased polyol type on the properties of polyurethane hotmelt adhesives for footwear joints

Polyurethanes, one of the most used polymers worldwide, are strongly dependent of non-renewable fossil resources. Thus, boosting the production of new polyurethanes based on more sustainable raw materials is crucial to move towards the footwear industry decarbonisation. The aim of this study is to synthesise and characterise reactive hotmelt polyurethanes from biomass and CO2-based polyols as bioadhesives for the footwear industry. The influence of biobased polyols on the polyurethane structure, and therefore, on their final properties was analysed by different experimental techniques such us Fourier transform infrared spectroscopy (FTIR), Differential scanning calorimetry (DSC), Thermogravimetric analysis (TGA), Melting viscosity, Softening temperature and T-peel strength test, in order to assess their viability for the upper to sole bonding process. The results obtained indicated that the incorporation of different amounts of the biobased polyols produces changes in the structure and final performance of the polyurethanes. Therefore, adhesion test carried out by the T-peel test 72 h after the upper -to- sole bonding of the sustainable adhesives show high final adhesion values. These sustainable raw materials provide polyurethane adhesives with additional beneficial non-toxicity and sustainable characteristics, without harming their properties during their useful life.

Structure and adhesion properties of waterborne poly(urethane urea)s containing small amounts of different graphene derivatives

Waterborne poly(urethane urea)s (PUDs) containing graphene derivatives with different morphologies and surface polarities were synthesized via in situ polymerization by using the acetone method. Small amounts (0.04–0.30 wt.%) of graphene oxide (GO), graphite nanoplatelets (GP) or milled graphite (MG) were mixed with polyadipate of 1,4-butanediol polyol and added during synthesis of the PUDs. The addition of graphene derivatives changed differently the degree of micro-phase separation of the poly(urethane urea)s (PUs) depending on the balance between the extent of covalent interactions between the surface functional groups on the graphene sheets and the isocyanate groups, and the number of stacked graphene sheets. Whereas MG mainly intercalated between the soft segments showing a typical behavior of nanofiller, GP and, particularly, GO showed different degrees of micro-phase separation due to more net covalent interactions with the poly(urethane urea) chains which caused higher crystallinity. The addition of graphene derivative decreased the glass transition temperature of the hard segments and increased the percentages of associated by hydrogen bond urethane and urea groups, more noticeably by adding GP and MG. Lower temperatures of decomposition and higher amounts of urethane and urea hard domains, and soft domains were found in PU + GO and PU + MG, and they showed an additional structural relaxation at 11–16 °C. PU and PU + GP had higher thermal stabilities than PU + GO and PU + MG and the addition of GP and, more markedly, GO imparted toughening to the poly(urethane urea). The T-peel strength values were higher in the joints made with PUD + GO due to the more net covalent interactions between the surface functional groups on the GO sheets and the poly(urethane urea) chains. On the other hand, the lap-shear strength of the joints made with PUD + MG and, in less extent, with PUD + GP noticeably increased.

Influence of the Surface Chemistry of Graphene Oxide on the Structure-Property Relationship of Waterborne Poly(urethane urea) Adhesive.

Small amounts—0.04 wt.%—graphene oxide derivatives with different surface chemistry (graphene oxide—GO-, amine-functionalized GO—A-GO-, reduced GO—r-GO) were added during prepolymer formation in the synthesis of waterborne poly(urethane urea) dispersions (PUDs). Covalent interactions between the surface groups on the graphene oxide derivatives and the end NCO groups of the prepolymer were created, these interactions differently altered the degree of micro-phase separation of the PUDs and their structure–properties relationships. The amine functional groups on the A-GO surface reacted preferentially with the prepolymer, producing new urea hard domains and higher percentage of soft segments than in the PUD without GO derivative. All GO derivatives were well dispersed into the PU matrix. The PUD without GO derivative showed the most noticeable shear thinning and the addition of the GO derivative reduced the extent of shear thinning differently depending on its functional chemistry. The free urethane groups were dominant in all PUs and the addition of the GO derivative increased the percentage of the associated by hydrogen bond urethane groups. As a consequence, the addition of GO derivative caused a lower degree of micro-phase separation. All PUs containing GO derivatives exhibited an additional thermal decomposition at 190–206 °C which was ascribed to the GO derivative-poly(urethane urea) interactions, the lowest temperature corresponded to PU+A-GO. The PUs exhibited two structural relaxations, their temperatures decreased by adding the GO derivative, and the values of the maximum of tan delta in PU+r-GO and PU+A-GO were significantly higher than in the rest. The addition of the GO derivative increased the elongation-at-break, imparted some toughening, and increased the adhesion of the PUD. The highest T-peel strength values corresponded to the joints made with PUD+GO and PUD+r-GO, and a rupture of the substrate was obtained.

A novel natural rubber pressure sensitive adhesive patch amended with cinnamon oil for preserving bakery product

Novel pressure sensitive adhesive natural rubber (NR-PSA) patch incorporated with cinnamon oil (CO) and xyloglucan (XG) was prepared to study the effects on mechanical properties, antimicrobial activity, thermal stability, release rate, and shelf life extension of banana cake. The mechanical property test revealed that the contents of CO (8, 10, 15, 20, and 40 μL/patch) did not significantly affect both T-peel and shear strength of NR-PSA/cinnamon oil (NR-PSA/CO) patch. However, CO enhanced the T-peel by 50 % compared to the control patch (without CO). The antimicrobial efficacy was verified against Staphylococcus aureus, Escherichia coli, and Aspergillus niger. At 40 μL of incorporated CO, the patch prolonged the storage life of banana cake for 4 days at ambient temperature relative to the control sample. The release of CO from the patch was studied at 75 % relative humidity (RH). The highest release rate was observed at the first 10 days, and slightly increased up to 45 % after 40 days of the test. These findings indicated a potential of using NR-PSA/CO patch to extend the shelf life of bakery products.

Analyses of the Adhesion Interphase of Isotactic Polypropylene Using Hot-Melt Polyolefin Adhesives

The interphase structure and properties of isotactic polypropylene (it.PP) have received much attention in the fundamental science and industrial applications for the improvement of the poor adhesion properties of the it.PP. In this work, we focused on the laminates with it.PP substrates and various ethylene–octene rubber (EOR) hot-melt adhesives with different molecular weights and crystallinities. We prepared laminate samples using EOR with low molecular weight, random copolymerized EOR, and block-like copolymerized EOR as adhesives. We performed T-peel tests of the laminate samples and evaluated their thickness of the interphase with confocal Raman scattering imaging, X-ray refraction contrast imaging, and atomic force microscopic imaging. The laminates with larger interphase thicknesses possessed the larger T-peel strengths, which were relatively consistent with these obtained results among all the measurement methods. It is revealed that the adhesion properties and the interphase thicknesses depended on the crystallinities of the it.PP substrates. These results mean that the interphase would be constructed by not only diffusion of molecular chains but also the crystalline growth and the formation of lamellae interlock in the interphase region.

Preparation and Properties of Biobased, Cationic, Waterborne Polyurethanes Dispersions from Castor Oil and Poly (Caprolactone) Diol

Biobased cationic waterborne polyurethanes (WPUs) were prepared using isophorone diisocyanate (IPDI), N-methyl diethanolamine (N-MDEA), polycaprolactone (PCL) diol, hydrochlotic acid (HCl), and 1,4-butanediol (BDO). To improve the mechanical performance and adhesive strength of the waterborne polyurethane films, different amounts of castor oil (CO) acting as a cross-linking agent were incorporated in the polyurethane structure. The structures of the waterborne polyurethanes were assessed by Fourier-transform infrared spectroscopy (FTIR). The combination of CO had a positive effect on the dispersion and stability properties of WPUs. WPUs containing higher content of CO demonstrated a remarkable enhancement in homogeneity among particles. The stable aqueous dispersion was obtained even when N-MDEA loading was as low as 3.2 wt%; a bonus of this low hydrophilic moiety was the excellent adhesive strength, whose T-peel strength could reach up to 36.8 N/25 mm, about 114% higher than that of WPU (17.2 N/25 mm) without any CO content. The elongation at break of CO7.40%-WPU was 391%. In addition, the fracture mechanism of the waterborne polyurethane films transformed from the brittle failure to the ductile fracture. The experiment results showed the CO-modified WPUs displayed excellent film-forming property, flexibility, and adhesion, which can be employed for constructing the eco-friendly, biodegradable, cationic, waterborne polyurethanes.

Adhesive Wet Metallization on TiO2-Coated Glass

In this study, a process for wet metallization on glass substrate involving adhesive electroless plating (ELP) is developed by integrating two material innovations. The first involves functionalizing a polymer-capped Pd nanocluster with amino silane compound to strengthen the adhesion between the ELP metal film and substrate. The second involves an additional nanoscaled TiO2 layer serving as the adhesion promoting layer (APL) coated on glass before metallization. After investigation with various tools, ELP metal film was observed to penetrate the mesoporous structure of TiO2 APL, reinforcing the adhesion of metallized film on glass through the mechanical anchoring effect. The formation of an interlayer between TiO2 APL and glass is not observed. A T-peel strength of 325 N m−1 is achieved. According to fracture analysis, the metal film/TiO2/glass structure breaks inside TiO2 APL, not TiO2 APL/glass, suggesting that further engineering developments are required to improve TiO2 APL coating.

Adhesion enhancement between aluminum and butyl rubber by (3-mercaptopropyl) trimethoxy silane for vibration damping plate

A silane coupling agent for an aluminum-based vibrational damping plate with a butyl rubber damper, which shows excellent viscoelasticity and thermal stability, was studied to enhance the adhesion strength between aluminum and butyl rubber. Considering the chemical structure of the butyl rubber, we introduced (3-mercaptopropyl) trimethoxysilane (MPTMS) as the silane coupling agent because it has a thiol functional group that can bind to the carbon chain of butyl rubber via thiol-ene reaction under heating. Based on the results of various surface analyses and the T-peel strength test, the MPTMS treatment condition was optimized, and a 180% enhancement of peel strength was obtained. Finally, a central supporting vibration test was conducted to prove the damping performance of aluminum damping plated with MPTMS. As a result, a 7-fold enhancement in the damping loss factor was seen in the damping with MPTMS compared to without.

Addition of small amounts of graphene oxide in the polyol during the synthesis of waterborne polyurethane urea adhesives for improving their adhesion properties

Mixtures of polyadipate of 1,4-butanediol polyol and different small amounts (0.01–0.10 wt%) of graphene oxide (GO) were added during the synthesis of waterborne polyurethane urea dispersions (PUDs) carried out with the acetone method. The addition of 0.02–0.04 wt% GO increased the T-peel strength of plasticized poly (vinyl chloride)/PUD/plasticized poly (vinyl chloride) joints whereas the addition of 0.05–0.10 wt% GO increased the single lap-shear strength of stainless steel/PUD/stainless steel joints. The improved adhesion of the PUDs containing GO was ascribed to the creation of covalent interactions between the surface groups on the GO surface and the NCO groups of the isocyanate during prepolymer formation, creating new urethane groups; during the phase inversion, the covalently bonded GO sheets were embedded between the polyurethane urea chains inside the PUD particles, this changed the degree of phase separation between the hard and the soft segments. When more than 0.04 wt% GO was added, some GO particles cannot be covalently bonded to the prepolymer during the PUD synthesis but they agglomerated and physically “trapped” between the polyurethane urea chains. As a consequence, the adhesion properties of the PU + GO films were different in the PU films containing 0.01–0.04 wt% GO and the ones containing 0.05–0.10 wt% GO.