Improvement In Peel Strength Research Articles

Enhancing interfacial bonding between the copper foil and poly-ether-ether-ketone film via dual modification using UV/ozone and silane coupling

In this study, copper foil and poly-ether-ether-ketone (PEEK) film were directly bonded using nanosecond lasers. To strengthen the interfacial bonding between the copper foil and PEEK, ultraviolet/ozone (UV/ozone) and silane coupling treatment (APTMS) methods were proposed to modify the surface of the copper foil. The UV/ozone treatment led to the oxidation of the surface of the copper foil to Cu2O. The bonding interface and fracture were characterized and analyzed via optical digital microscopy (OM), scanning electron microscopy (SEM), energy dispersive spectrometry (EDS), Fourier transform infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS). The Cu/PEEK joints demonstrated a 95 % improvement in peel strength following UV/ozone + silane coupling treatments. Additionally, the red shift of the typical functional group wavenumbers demonstrated a strong hydrogen bond interaction between the copper foil treated with UV/ozone + silane coupling and the PEEK film. The mechanism behind the superior peel strength of UV/ozone + ATPMS-Cu/PEEK joints was subsequently validated through the density functional theory (DFT) analysis. Moreover, DFT was utilized to calculate the differential charge transfer and binding energies of Cu/silanol and Cu2O/silanol. As per the results, the bonding of Cu2O to silanol was more stable than that of Cu to silanol.

Effect of poly (acrylamide-co-acrylic acid salt) on anti-aging properties and adhesion between acrylonitrile butadiene rubber and polyester fabric

In this study, a multifunction polymeric adhesion promoter and anti-aging compound based on the triethanolamine salt of acrylamide acrylic acid copolymer (COS) was prepared and characterized using Fourier-transform infrared spectroscopy (FTIR). The impact of different COS contents on the tensile, adhesion, and thermal properties of NBR composite and NBR/PET sandwich was evaluated. The NBR composites containing COS displayed good retention of their mechanical properties with increasing thermal ageing time, while the composite without COS showed a decrease in its mechanical properties. The highest tensile strength (17.5 MPa with a retention value of 0.6%) after 7 days of thermal aging was recorded for NBR composite, which contains 5 phr (parts per hundred parts of rubber) of COS (COS 5), compared to NBR composite without COS (COS 0), which recorded 15.1 MPa with a retention value of -27.4%. In addition, the COS 5 composite displayed an improvement in peel strength of 16.4% compared to the COS 0. The results of the thermogarvemetric analysis (TGA) supported the anti-thermal ageing effect of COS, where the initial decomposition temperature (Ti) value increased by 11.7 and 9.3 °C, after addition of 5 and 10 phr of COS to NBR composite, respectively. In addition, the other thermogravemetric parameters investigated displayed a significant increase in their values, which confirms the improvement in thermal stability of NBR composite in the presence of COS. Also, the air permeability of the PET/NBR sandwich decreased by 80% after the addition of 7.5 phr of COS.

Effect of paint baking thermal cycle on joint strength of spot welds

Advanced high strength steel sheet (AHSS) is widely used in the automotive body for weight reduction and the improvement of crash performance. Such use requires higher joint strength of the resistance spot weld in AHSS. In laboratory tests, the joint strength of specimens is evaluated in as-welded condition. The effect of paint baking cycles is usually not considered, so the actual joint strength in the automotive body is not clear. In this study, we focus on the effect of the thermal cycle corresponding to paint baking treatment on the joint strength of spot welds. Two types of tensile test, shear tensile test, and L-shaped peel tensile test were carried out. The material strength grades used in this test were from 270 to 980 MPa. The weld nugget diameter was varied from three to five square root t in each material. A paint baking thermal cycle (170 °C for 20 min) was applied to the welded joints before the tensile tests were carried out. The paint baking treatment does not cause a change in the shear strength of joints in any of the conditions (materials and nugget diameter). On the other hand, in the case of materials of 590 MPa grade or higher is used, the paint baking treatment can cause an increase in peel strength of the joint. Especially, the increase of joint strength by the paint baking treatment is most obvious in smaller nugget conditions. The results of this study suggest that the improvement in peel strength by paint baking treatment is caused by a tempering effect in the weld nugget. From these results, we concluded that the joint strength of paint-baked specimens would be more practical data, representing the actual joint performance in automotive bodies.

Water based quad acrylic copolymer/cloisite 30B nanocomposite heat resistant adhesive: thermal and rheological properties

In this study, a quad acrylic copolymer composed of four monomers namely acrylic acid, methacrylic acid, butyl acrylate, and methyl methacrylate/cloisite30B(C30B) nanocomposites with different loading of nanoclay (0.5–3.0%) is prepared by the in-situ method for heat resistant adhesive application. Different parameters like solid content, solubility, appearance, acid value, and pH values are measured for each nanoclay filled copolymer. For dispersion and thermal characterization of nanocomposite X-ray diffraction (XRD), High-resolution transmission electron microscopy (HRTEM), thermogravimetric analysis (TGA), and differential scanning calorimetry (DSC) are performed. Epoxy resin along with curing agent is added to the acrylic copolymer/C30B nanocomposite to prepare adhesive. The rheological properties for amplitude sweep, frequency sweep, and temperature scan are analyzed. The nanoclay content doesn’t affect the shear-thinning component significantly but improves the complex viscosity and elastic behavior of the adhesives. The crossover point shows good dispersion of C30B up to 2.0% in nanocomposite adhesive. Peel strength is found to be increased with an increase in nanofiller content up to 2.0%. A significant improvement in peel strength is observed when exposed to 150 °C for 45 min. Temperature sweep study by rheology and peel strength results at high temperature suggest that these adhesives can be used in high-temperature resistance adhesive application areas like heat seal packaging and fabric lamination.

Reversibly Cross-linkable Bottlebrush Polymers as Pressure-Sensitive Adhesives.

Dynamically cross-linkable bottlebrush polymer adhesives were synthesized by the grafting-from strategy through a combination of ring-opening metathesis polymerization (ROMP) and photoiniferter polymerization. A norbornene-containing trithiocarbonate was first polymerized by ROMP to form the bottlebrush polymer backbone; this was followed by blue-light-mediated photoiniferter polymerization of butyl acrylate initiated by the poly(trithiocarbonate) to form the bottlebrush polymer. This strategy afforded well-defined bottlebrush polymers with molar masses in excess of 11 000 kg/mol. For un-cross-linked bottlebrush polymers, 180° peel tests revealed a cohesive failure mode and showed similar peel strengths (∼30 g/mm) regardless of the backbone polymer degree of polymerization (DP). The bottlebrush polymers were then treated with butylamine to remove the trithiocarbonate, liberating thiols on each side-chain terminus. In the presence of oxygen, these thiols readily cross-linked via disulfide bond formation. The cross-linked bottlebrush polymers with a backbone DP of 400 showed a greater than sixfold improvement in peel strength, whereas those with a backbone DP of 100 exhibited a twofold enhancement compared with un-cross-linked samples along with a change to adhesive failure. Triphenylphosphine readily reduced the disulfide bonds, effectively removing all cross-links in the bottlebrush network and allowing for recasting of the adhesive, which showed similar adhesive and rheological properties to the original un-cross-linked samples.

The effect of tungsten disulphide nanoparticles on the properties of polyurethane adhesives

Thermoset-elastomer polyurethane (PU) nanocomposites were prepared using two types of tungsten disulphide (WS2) nanoparticles: inorganic fullerene-like (IF) and inorganic nanotubes (INT) through an in-situ polymerization process. The quality of dispersion was evaluated using scanning electron microscope (SEM) and the thermomechanical properties were analyzed using dynamic mechanical analysis (DMA). Addition of 1% and 3 wt.%. IFs resulted in enhancement in storage modulus of 45 and 100%, respectively, compared to the neat polymer. The enhancement using only 0.5% wt. INTs was more than 100% and then decreased with additional amount of nanotubes. While no significant change in the composite’s glass transition temperature (Tg) was observed with IF-WS2, 0.5% INT-WS2 showed a 20 °C increase of Tg. In both cases, analysis of the chemical structure using an attenuated total reflectance- Fourier transform infrared spectroscopy showed no effect of the nanoparticles on the chemical structure of the PU and wide-angle X-ray diffraction showed no change in morphology. In the case of IF-WS2 the highest peel strength was obtained with 1% wt. demonstrating a 44% improvement in peel strength. However, in the case of INT-WS2, incorporating 0.5% wt. improved the peel strength by more than 1000%. SEM analysis showed a unique development of a nodular morphology and a failure mechanism dominated by nanotube pull-out. It was concluded that the geometry of the nanoparticles (nanotubes or fullerene) has a dominant effect on the final PU nanocomposite properties.

Surface modification of argon/oxygen plasma treated vulcanized ethylene propylene diene polymethylene surfaces for improved adhesion with natural rubber

Vulcanized ethylene propylene diene polymethylene (EPDM) rubber surface was treated in a radio frequency capacitatively coupled low pressure argon/oxygen plasma to improve adhesion with compounded natural rubber (NR) during co-vulcanization. The plasma modified surfaces were analyzed by means of contact angle measurement, surface energy, attenuated total reflection-infrared spectroscopy, X-ray photoelectron spectroscopy, scanning electron microscopy, energy dispersive X-ray sulfur mapping and atomic force microscopy. Several experimental variables such as plasma power, length of exposure time and composition of the argon–oxygen gas mixture were considered. It was delineated that plasma treatment changed both surface composition and roughness, and consequently increased peel strength. The change in surface composition was mainly ascribed to the formation of C–O and –CO functional groups on the vulcanized surfaces. A maximum of 98% improvement in peel strength was observed after plasma treatment.

Mechanical Properties and Microstructures of SiC Fiber-reinforced Metal Matrix Composites Made Using Ultrasonic Consolidation

Ultrasonic consolidation was used for making SiC fiber-reinforced Al 3003 matrix composites. Peel tests, tensile tests, and bend tests were carried out on the composite specimens as well as on ultrasonically consolidated Al 3003 specimens containing no SiC fibers. The objective of this study was to examine whether the ultrasonically embedded SiC fibers serve as effective reinforcements or not. Incorporation of SiC fibers resulted in a considerable improvement in peel strength and tensile strength of ultrasonically consolidated parts. However, bend tests revealed some deterioration in the shear strength of the parts due to the presence of fibers. The results of mechanical testing are discussed based on microstructural and fractographic studies.

Synthesis and properties of nanocomposite adhesives

A series of acrylic co-polymers and terpolymers from ethyl acrylate (EA), butyl acrylate (BA) and acrylic acid (AA) were synthesized by solution polymerization. Nanocomposite adhesives based on these acrylic polymers and silica or clay were prepared by sol–gel or solution blending techniques, respectively. The effect of nanoparticles on the performance of the hybrid adhesives was investigated by measuring peel strength, lap shear strength or static shear resistance against three substrates having different surface characteristics- aluminum (Al), wood (W) and biaxially oriented polypropylene (PP). The results showed significant improvement in peel strength of Al–Al and PP–PP joints with increase in polarity of the polymer matrix and nanofiller concentration. These results could be explained in terms of higher cohesive strength of the nanocomposite adhesives. The locus of failure also changed from interfacial failure for neat acrylic adhesive to stick–slip failure for the hybrid composites. Both the lap shear strength and static shear resistance of the hybrid nanocomposites also gradually increased with nanofiller loading. Al–Al and W–W joints displayed higher joint strength, because of the interaction of the hydroxyl groups present on the surface of these substrates.

Adhesion behavior of PDMS-containing polyimide to glass

The effect of the incorporation of poly(dimethyl siloxane) (PDMS) segments into a poly[N,N'-(p,p'-oxydiphenylene) pyromellitimide] (PMDA-ODA) polyimide backbone on the adhesion between PMDA-ODA polyimide and glass was investigated using X-ray photoelectron spectroscopy (XPS), infrared (IR) spectroscopy, contact angle measurements, and the peel test. The peel energy of PMDA-ODA polyimide to glass was significantly improved when low molecular weight PDMS (248.5 g/mol) was incorporated, while little improvement was observed for the incorporation of high molecular weight PDMS (900 or 1680 g/mol). Exposure to air resulted in a considerable deterioration in the peel energy for the pure PMDA-ODA polyimide, while no deterioration was observed for the PDMS-containing polyimides. The improvement in peel strength was successfully achieved by the incorporation of very small quantities of PDMS such as 2 wt%. Based on XPS, IR spectroscopy, and contact angle measurements, it is suggested that the incorporated PDMS segments migrated from the bulk polyimide to the polyimide/glass interface and chemically bonded to the glass surface, which resulted in enhancement of the peel energy. However, a weak boundary layer was formed between the bulk polyimide and glass when a high molecular weight PDMS (900 or 1680 g/mol) was incorporated and thus the peel energy deteriorated.

The effect of fluorination on the surface characteristics and adhesive properties of polyethylene and polypropylene

Polyethylene and polypropylene have been treated with fluorine/nitrogen or fluorine/oxygen/nitrogen mixtures at atmospheric pressure. Changes in surface chemistry and topography as well as depth of fluorination have been examined using Fourier transform infra-red analysis, X-ray photoelectron spectroscopy (X.p.s.), atomic force microscopy (AFM) and ellipsometry. Even very short exposure times caused a large substitution of the hydrogen atoms by fluorine. No change in surface topography was noticed at magnifications of up to 5000 times with the scanning electron microscope (SEM), but AFM showed that fluorination led to an increase of microroughness. The influence of fluorine or fluorine/oxygen concentration, as well as time of treatment and time of storage before adhesive bonding, on adhesion of polypropylene to steel was investigated with a bending peel test. Significant improvement in peel strength was already achieved with minor fluorination intensity. Increase of fluorination intensity did not lead to further improvement in peel strength. Analysis of the fracture surfaces was carried out with the SEM and by energy dispersive X-ray spectroscopy and X.p.s. The findings showed that the samples failed cohesively in the polymer or directly beneath the fluorinated layer. A model to describe the formation of specific interactions between substrate and adhesive is suggested.

Improving Bonding to Piezoelectric Poly(vinylidene fluoride) for Sensor Applications

Abstract Argon, oxygen, nitrogen and ammonia plasmas and an acid etch pretreatment were performed on uniaxially stretched piezoelectric poly(vinylidene fluoride) film in order to improve wettability and bonding. Oxygen plasma was found to be too harsh, but nitrogen and argon plasmas improved wettability and resulted in a seven-fold increase in 180° peel strengths. However, this improvement in peel strength was accompanied by a 90% decrease in the piezoelectric properties of the polymer. The acid etch yielded contact angles similar to those of the plasma treated material, and improved peel strengths some twelve times over that of the untreated film. Significantly, no piezoelectric loss resulted from the acid etch.

Studies on Adhesion Between Natural Rubber and Polyethylene and the Role of Adhesion Promoters

Abstract Studies on adhesion between natural rubber (NR) and polyethylene (PE) with different levels of interaction (physical and chemical) have been carried out. Ethylene propylene diene rubber (EPDM) and chlorinated polyethylene (CPE) were used as physical promoters and epoxidised natural rubber/modified polyethylene (ENR/PEm) and sulfonated ethylene propylene diene rubber/modified polyethylene (S-EPDM/PEm) were used as chemical adhesion promoters. The failure surfaces were examined with the help of scanning electron microscopy (SEM), optical photography and electron spectroscopy for chemical analysis (ESCA) techniques. The peel strength between natural rubber and polyethylene as measured in this study is 140 J/m2. With the incorporation of physical promoters such as EPDM, the peel strength increases twenty fold because of structural similarity of EPDM with PE and the rubbery nature of EPDM. Similarly, the other promoters show significant improvement in peel strength. At high temperature and low rate of...

Modification of a nitrile-phenolic bonding agent by addition of an interfacial agent: effect on the practical adhesion between nitrile rubber and metal

—The mechanism of vulcanization bonding of a nitrile rubber (NBR) elastomer to metal with a single-coat nitrile-phenolic bonding agent is discussed. A nitrile-phenolic bonding agent consisting of NBR, phenol formaldehyde (PF) resin, and vulcanizing agents was modified with an interfacial agent (p-cresol formaldehyde resin) and the effect of interfacial agent addition on the practical adhesion between metal and the NBR elastomer after vulcanization was investigated. The adhesion strength was measured in terms of the metal-to-NBR elastomer peel strength using the bonding agent. The addition of p-cresol formaldehyde (PCF) resin to the bonding agent with a proportionate reduction of PF resin initially improved the peel strength; a maximum was reached at about 20% PCF content and then decreased with a further increase in the PCF content. The improvement in peel strength produced by the addition of PCF resin is attributed to the increased chemical bonding between NBR and the phenolic resin. The drop in peel str...

The Effect of Bubbles at the Interface on the Adhesion of Polyethylene to Metals

By use of a blowing agent bubbles of a few hundred microns diameter were introduced at the interface of copper and steel substrates coated with low density polyethylene. The presence of the bubbles leads to an improvement in peel strength. An explanation is put forward in terms of a suggested stress perturbation produced by the bubbles which leaves the interface itself relatively lowly stressed and leads to the expenditure of work in plastic deformation of the polymer away from the interface. Support for the explanation was obtained by photoelastic study of a model system and by scanning electron microscopy of the peeled surfaces.

Adhesion of Electroformed Copper and Nickel to Plastic Laminates

SummaryBy electroforming a copper or nickel surface to give mechanical keying, its adhesion to epoxide laminates can be increased from a peel strength of 4 lb/in to 12 lb/in. By oxidation or chemical treatment of the metal surface an improvement in peel strength of about 1 lb/in is obtained.