High Peel Strength Research Articles

Effects of compatibility between tackifier and polymer on adhesion property and phase structure: Tackifier‐added polystyrene‐based triblock/diblock copolymer blend system

AbstractThe effects of compatibility of tackifier with polymer matrix and mixing weight ratio of triblock/diblock copolymers as the matrix on the adhesion property and phase structure of tackifier‐added polystryrene triblock/diblock copolymer blends were investigated. For this purpose, polystyrene‐block‐polyisoprene‐block‐polystyrene triblock and polystyrene‐block‐polyisoprene diblock copolymers were used and the diblock weight ratio in the blend was varied from 0 to 1. Spherical polystyrene domains with a mean size of about 20 nm were dispersed in the polyisoprene (PI) continuous phase. In the case of the hydrogenated cycloaliphatic resin as tackifier having a good compatibility with PI and a poor compatibility with polystyrene, the peel strength increased with an increase of the tackifier content, and the degree of increase became significant above 40 wt % of tackifier. It was found that the nanometer‐sized agglomerates of tackifier in the PI matrix were formed and the distance between the nearest neighbors of agglomerates was about 15 nm from SAXS measurement. The peel strength increased with an increase of the nanometer‐sized agglomerates of tackifier from TEM observation. On the other hand, in the case of the rosin phenolic resin as tackifier having a good compatibility with both polystyrene and PI, the peel strength increased effectively at the lower tackifier content, while no significant increase at higher tackifier content was observed. The agglomerates of tackifier were never confirmed in this system. The higher peel strength was obtained at the diblock weight ratio in the blend of 0.5–0.7 for both tackifier‐added systems. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011

Rheological and adhesion properties of acrylic pressure‐sensitive adhesives

AbstractDifferent pressure‐sensitive adhesives (PSAs) based on acrylic monomers were synthesized under different reaction conditions. The synthesized PSAs have good adhesive properties and without leaving any residue can be easily peeled off from the surface of a substrate. The relationship between PSAs rheological behavior and its adhesion properties (e.g., peel, tack, and shear resistance) has been studied at constant adhesive thickness. The samples were examined for their surface energy and viscoelastic characteristics. It was observed that increase in reaction temperature and reaction time results in decreased storage modulus due to lowered molecular weight, which finally leads to lower elasticity of the PSA. While the storage (G′) and loss (G″) modulus of samples increase with increased initiator concentration, the elasticity of PSA is increased as well. High G″ at high frequency (100 Hz) represents high peel strength because of higher dissipation of viscoelastic energy during debonding. The tack values increase by lowering storage modulus at 1 Hz due to higher Me. Shear values are increased by higher storage modulus at low frequency (0.1 Hz) due to hydrogen bonding of the different components. Some parallel investigations on the surface energy of the samples showed that they have different properties because of the nature of different monomeric units with their corresponding orientations. Our results reveal that the peel strength is not affected by surface energy. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011

Effect of Ni-Cr seed layer thickness on the adhesion characteristics of flexible copper clad laminates fabricated using a roll-to-roll process

The adhesion strength of a Cu/Ni-Cr/polyimide flexible copper clad laminate (FCCL), which was manufactured via a roll-to-roll process, was evaluated according to the thickness of the Ni-Cr seed layer using a 90° peel test. The changes in the morphology, chemical bonding, and adhesion properties were characterized using a scanning electron microscopy (SEM), an atomic force microscopy (AFM), and an X-ray photoelectron spectroscopy (XPS). The thickness of the Ni-Cr (Ni:Cr = 80:20) seed layer in which the maximum peel strength of the FCCL was observed was 200A. The higher FCCL peel strength was attributed to the lower proportion of C-N bonds and higher proportion of C-O and carbonyl (C = O) bonds in the polyimide surface compared with the FCCL with a lower adhesion strength. The FCCL with a higher peel strength had a fractured polyimide surface with a higher surface roughness. The adhesion strength between the metal and polyimide was pirmarily attributed to the chemical interaction between the metal layer and the functional groups of the polyimide.

Effect of particle structure on the peel strength and heat resistance properties of vinyl acetate/acrylate latexes laminating adhesives

The concept of using particle structure design to prepare emulsion laminating adhesives (LAs) for improving both the peel strength and heat resistance properties has been investigated. The homogeneous particle latices based on vinyl acetate/acrylate copolymer (samples 1–3) were synthesized by seeded semicontinuous emulsion polymerization with different chain transfer agent (CTA) contents but with no functional monomers, while the core-shell structure crosslinkable latices (samples 4 and 5) were prepared through multistage polymerization technique. The emulsion particle structure was investigated by TEM and particle size analyzer. The results indicate that the average emulsion particle diameter is about 130 nm and the particles grow without secondary nucleation. Samples 1 and 2 prepared with 0.7 and 0.5 phm (per hundred gram monomer) CTA respectively, show high peel strength but poor heat resistance property. On the contrary, the sample 3 prepared with 0.1-phm CTA exhibits low peel strength but relatively good heat resistance. However, sample 4, which was synthesized with 0.5-phm CTA and 0.4-phm acetoacetoxy ethyl methacrylate (AAEM) in core but 0.5-phm CTA and 0.6-phm AAEM in shell stages, shows high peel strength (1032.9 g/in.) and good heat resistance property (524.9 g/in.). In addition, sample 5 also demonstrates high peel strength (987.2 g/in.) and good heat resistance property (643.5 g/in.) when it was synthesized using 0.1-phm CTA but no AAEM in core, 0.36-phm CTA and 0.75-phm AAEM in shell stages. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010

Effect of thermal treatment on adhesion strength of Cu/Ni–Cr/polyimide flexible copper clad laminate fabricated by roll-to-roll process

In this study, the effect of a Ni–Cr seed layer on the adhesion strength of flexible copper clad laminate (FCCL) was evaluated after thermal treatment. The changes in the chemical composition, morphology and adhesion property were characterized by scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), electron probe micro analyzer (EPMA), X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM) and 90° peel test. The peel strength of the FCCLs was significantly affected by the thermal treatment and the FCCL with a higher peel strength had a higher thermal stability than that with a lower peel strength. The roughness of the fracture surface for the FCCLs decreased with increasing thermal treatment temperature and holding time. The thermal treatment of the FCCL increased the ratio of the C–N bonds and reduced that of the C–O and carbonyl (C O) bonds in the polyimide.

Preparation and Properties of Glass Cloth-reinforced Meltable Thermoplastic Polyimide Composites for Microelectronic Packaging Substrates

Meltable thermoplastic polyimide resins (MTPI) with designed polymer backbones and controlled molecular weights for advanced microelectronic packaging substrate application have been synthesized by thermal polycondensation of aromatic dianhydride and aromatic diamine in presence of endcapping agent. The thermoplastic polyimide resins could be dissolved in organic solvents to give low viscosity solutions, which were then employed to impregnate E-glass cloth (EG) to yield MTPI/EG prepregs. After removal of the organic volatile, the MTPI/EG prepregs were plied up and then melt processed to give MTPI/EG composite laminates with high quality. Experimental results demonstrated that the MTPI/EG composite laminates showed desirable characteristics, including: (1) excellent thermal stability; (2) good mechanical properties; (3) great electrical insulating and dielectric properties; as well as (4) high peel strength between copper foil and the composite surface.

Spray Deposition Methods for Improving Interfacial Strength of Copper–Epoxy Systems

A simple spray method using a plain orifice atomizer has been developed for depositing γ-aminopropyltriethoxysilane (APS) from solutions in water and in methanol onto copper surfaces. The evaporative patterns of the sprayed droplets were studied to determine the distribution of deposited APS and the percent coverage of the surface. The peel strengths between copper foil and epoxy resin were measured with and without APS deposition. It was shown that the application of APS resulted in a considerable increase in interfacial adhesion. APS applied from a 1 wt% solution in methanol resulted in a higher peel strength than when applied from a 1 wt% aqueous solution; the opposite was true with 0.2 wt% APS solutions, indicating a trade-off between deposited APS film thickness and surface coverage. In all cases, a higher concentration of APS gives a higher peel strength. APS was very effective when chemisorption occurred at the surface but much less effective when only physisorption took place. A study of the fracture surfaces showed cohesive failure inside the epoxy layer, and that the deposited APS on the copper surfaces had a long-range effect which was seen deep into the epoxy layer, well away from the copper surface.

Effect of Cr Thickness on Adhesion Strength of Cu/Cr/Polyimide Flexible Copper Clad Laminate Fabricated by Roll-to-Roll Process

The adhesion strength of a Cu/Cr/polyimide (PI) flexible copper clad laminate (FCCL), which was manufactured by the roll-to-roll process, was evaluated according to the thickness of the Cr seed layer using the 90° peel test. The changes in the morphology, chemical bonding and adhesion properties were characterized by scanning electron microscopy, atomic force microscopy and X-ray photoelectron spectroscopy. The peel strength of the FCCL decreased with increasing Cr layer thickness. The higher FCCL peel strength was attributed to the lower proportion of C-N bonds and higher proportion of C-O or carbonyl (C=O) bonds on the PI surface compared to the FCCL with the lower adhesion strength. The FCCL with the higher peel strength had a fractured PI surface with a higher surface roughness. The adhesion strength between the metal and PI was mostly attributed to the chemical interaction between the metal layer and the functional groups of the PI.

Surface Modification of Polyimide for Improving Adhesion Strength by Inductively Coupled Plasma

This study examined the effect of an inductively coupled plasma (ICP) treatment using an argon and helium gas mixture on the adhesion between polyimide and a copper film. Optical emission spectroscopy (OES) of the ICP revealed the emission intensity of helium and argon at various intensities with the helium mixing ratio. The treated polyimide surface was analyzed using a contact angle analyzer, Atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS). The contact angle and RMS roughness ranged from 66 to 31° and 2.3 to 4.1 nm, respectively. XPS showed an increase in C–O bonding. The highest peel strength was 0.43 kgf/cm at a 40% of helium mixing ratio, which contained the highest level of activate species. Overall, an ICP treatment of a polyimide surface with a 40% helium gas mixture improves the adhesion strength between copper and polyimide significantly.

Adhesion Improvement of Polyimide/Metal Interface by He/O2/NF3 Atmospheric Pressure Plasma

AbstractThe surface of polyimide (PI) was modified with He/O2/NF3 dielectric barrier discharge generated by 13.56 MHz r.f. at atmospheric pressure in order to improve adhesion between metal (Cu/Cr) and PI. He/O2/NF3 plasma severely etched the surface of PI and formed many conical clusters of below 100 nm diameter on the PI surface. The surface roughness of PI was increased from 0.4 to 11 nm with r.f. power. X‐ray photoelectron spectroscopy (XPS) analysis showed that oxygen concentration was increased as much as the decrease of carbon concentration after plasma treatment. XPS analysis also showed that the component ratio of CO bonding, which is a hydrophilic functional group, was increased about 30% by the plasma treatment as compared with untreated PI. T‐peel test showed that peel strength was increased with r.f. power. The highest peel strength was 148 gf · nm−1, which was about 50 times as high as the peel strength obtained without plasma activation. It is more than two times as strong as the adhesion between the Cu/Cr film and PI substrate treated by O2 plasma. The surface morphology and chemical composition of the detached side of the PI treated by He/O2/NF3 plasma were similar to untreated PI.

Adhesion of Vulcanized Rubber Surfaces: Characterization of Unmodified and Electron Beam Modified EPDM Surfaces and Their Co-vulcanization with Natural Rubber

Peel adhesion behavior of unmodified and modified ethylene propylene diene methylene (EPDM) vulcanizates covulcanized with gum natural rubber (NR) is reported in this paper. Modification of the vulcanizate surface has been carried out by electron beam (EB) irradiation with or without EB sensitizers such as trimethylol propane triacrylate (TMPTA) and tripropylene glycol diacrylate (TPGDA). The doses of both EB and TMPTA/TPGDA have been varied in separate experiments keeping one of them constant. The surface features have been analyzed using several analytical techniques like attenuated total reflection infrared spectroscopy, X-ray photoelectron spectroscopy, atomic force microscopy, scanning electron microscopy, energy dispersive X-ray sulphur mapping, surface energy measurements, free sulphur and gel content analysis. In comparison to its unmodified EPDM vulcanizate counterpart, 100 kGy modified EPDM vulcanizate in presence of 10 wt% TMPTA shows a maximum increase in O/C ratio value from 0.01 to 0.14. High energy irradiation leads to oxidation, grafting, breakdown of cross-links and blooming, which have been quantified. The joint strength of the modified and unmodified vulcanized EPDMs with gum NR has been tested at room temperature and is found to be a strong function of the nature and extent of the modification and surface roughness. The 10 wt% TMPTA soaked EPDM vulcanizate irradiated at 100 kGy has shown the highest peel strength (71% over that of the untreated sample) among all the samples.

Enhancement of the adhesive force of metal films on PTFE surface achieved by fast-atom-beam surface modification

We tried the method to increase the peel strength between thin film metals and various substrate materials using saddle field fast atom beam (FAB) sources. It is notable that the peel strength was increased more than several times for all substrates than those who were not modified by surface activation using FAB irradiation. Highest peel strength was observed at the coupling of Si and metals in both case of Ar irradiation and SF6 reactive etching by FAB. This surface activation technique was applied to the fabrication of microelectrodes for the detection of mouse nerve signals. The process is expected as one of the available techniques for pre-treatment of the film deposition for several electrical devices.

Plasma surface treatment of polyimide for adhesive Cu/80Ni20Cr/PI flexible copper clad laminate

Two different methods of surface treatment, a low pressure plasma treatment and an atmospheric plasma treatment, on polyamide (PI) substrate were investigated from the point of view of adhesion of a Cu/80Ni20Cr layer on PI in flexible copper clad laminate (FCCL). The specimen treated with atmospheric plasma had high peel strength properties before and after aging. The root-mean-squared (rms) roughness with samples exposed to both kinds of plasma treatment was almost the same at 0.68 nm and 0.65 nm respectively, but the contact angle was different at 14.5° and 5.9°. We interpret this to mean that a more hydrophilic surface can be obtained using atmospheric plasma treatment. Observing the XPS spectra, more C–O binding rate was identified on the FCCL sample treated with the atmospheric plasma. From these results, it is suggested that the better adhesion achieved with atmospheric plasma treatment is not due to the mechanical roughness on the PI but due more to the activated C–O chemical bonding.

分子接着剤を用いる樹脂とシリコーンゴムの直接架橋接着

A new concept has been proposed for adhesion theory and technology, unifying various adhesion theories and simplifying adhesion technology. This purpose is achieved by using a molecular adhesive, 6-(3-triethoxysilylpropy-lamino)-1, 3, 5-triazine-2, 4-dithiol (TES), which contains two functional groups of dithiol triazinyl and alkoxysilyl groups in one molecule. Resins such as epoxy resin, polyamide, and polyester were pretreated by corona discharge to form OH groups on the surfaces. The OH groups react readily with TES by heating for 10min at 150°C to give TES containing resin surfaces. Silicone rubber adhered readily to the TES containing resin surfaces by hot-pressing for 10min at 160°C, with very high peel strength which is destroyed in rubber-phase. Peel strength decreased with surface roughness on resins, and the amount of TES decreased with the roughness.

Evolution of High Peel Strength via Cavitation in Acrylic Rubber/Epoxy Resin Adhesive by Reaction-Induced Phase Decomposition

Evolution of High Peel Strength <I>via</I> Cavitation in Acrylic Rubber/Epoxy Resin Adhesive by Reaction-Induced Phase Decomposition

Fabrication of 2-Layer Flexible Copper Clad Laminate by Vacuum Web Coater with a Low Energy Ion Source forSurface Modification

In order to fabricate adhesiveless 2-layer flexible copper clad laminate (FCCL) used for COF (chip on film) with high peel strength, polyimide (PI; Kapton-EN, <TEX>$38\;{\mu}m$</TEX>) surface was modified by reactive <TEX>$O_2^+$</TEX> and <TEX>$N_2O^+$</TEX> ion beam irradiation. 300 mm-long linear electron-Hall drift ion source was used for ion irradiation with ion current density (J) higher than <TEX>$0.5\;mA/cm^2$</TEX> and energy lower than 200 eV. By vacuum web coating process, PI surface was modified by linear ion source and then 10-20 nm thick Ni-Cr and 200 nm thick Cu film were in-situ sputtered as a tie layer and seed layer, respectively. Above this sputtered layer, another <TEX>$8-9{\mu}m$</TEX> thick Cu layer was grown by electroplating and subsequently acid and base resistance and thermal stability were tested for examining the change of peel strength. Peel strength for the FCCLs treated by both <TEX>$O_2^+$</TEX> and <TEX>$N_2O^+$</TEX> ion irradiation showed similar magnitudes and increased as the thickness of tie layer increased. FCCL with Cu (200 nm)/Ni-Cr (20 nm)/PI structure irradiated with <TEX>$N_2O^+$</TEX> at <TEX>$1{\times}10^{16}/cm^2$</TEX> ion fluence was proved to have a strong peel strength of 0.73 kgf/cm for as-received and 0.34 kgf/cm after thermal test.

Peel and shear strength of pressure‐sensitive adhesives prepared from epoxidized natural rubber

AbstractPeel and shear strength of two grades of epoxidized natural rubber (ENR 25 and ENR 50)‐based pressure‐sensitive adhesive was studied. Coumarone‐indene resin was used as the tackifier, whereas toluene was chosen as the solvent throughout the experiment. The tackifier loading was varied from 0 to 80 parts per hundred parts of rubber (phr). A SHEEN hand coater was used to coat the adhesive on substrate to give a coating thickness of 30, 60, 90, and 120 μm. Peel strength and shear strength of the adhesive were determined by using a Lloyd adhesion tester and Texture analyzer, respectively. Results show that maximum peel strength occurs at 40 phr of coumarone‐indene resin for both ENRs studied an observation, which is attributed to the maximum wettability of the substrate. However, the shear strength shows a gradual decrease with increasing tackifier loading because of the decrease in cohesive strength of adhesive. ENR 25 consistently indicates higher peel strength and shear strength than ENR 50. Generally, peel and shear strength increases with coating thickness. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007.

Adhesion in Solid Propellant Rocket Motors

Plasma treatment of EPDM-based rocket motor insulation materials may change the peel strength between these materials and polyurethane polymers by a factor of 0.1 to 10. The matching of surface energies seems to be important for this adhesion process. The surface tension of the components was measured to between 30 and 50 mNm−1. The total surface energy of the insulation could be increased from 27.2 mNm−1 to ca. 70 mNm−1 by the plasma process. Maximum peel strength could be obtained by a treatment of less than 1 min, whereas in most cases longer times gave lower values. In some cases very long treatment also gave good strength, probably due to a rougher surface structure. The rate of cure of the polymer was important for the adhesion process as lower rates of cure correlated with higher peel strengths, which can be explained by diffusion of the polymer's components into the insulation.

Processing and characterization of multilayer films of poly(ethylene terephthalate) and surface-modified poly(tetrafluoroethylene)

Multilayer films were prepared from poly(tetrafluoroethylene) (PTFE) and poly(ethylene terephthalate) (PET) films together with using an adhesion promoting layer (tie-layer) consisting of ethylene-methyl acrylate-glycidyl methacrylate (E-MA-GMA) terpolymer and low density polyethylene (LDPE) blend. Na/naphthalene treatment and subsequent acrylic acid grafting were applied on the surfaces of PTFE for chemical modification. FT-IR spectroscopy, XPS analysis and surface energy measurements were performed to characterize the modified PTFE films. The analyses showed defluorination and oxidation of PTFE surface, and supported the acrylic acid grafting. The surface energy of modified surfaces enhanced with respect to unmodified one, which promoted adhesion. The multilayers were subjected to T-peel tests to measure the adhesion strength between PET and modified PTFE. Peel strength between the films increased with increasing E-MA-GMA amount in the tie-layer. A proportional dependence of peel strength on Na/naphthalene treatment time was observed for multilayers containing acrylic acid grafted or ungrafted PTFE. From SEM analysis, it was observed that the texture of the PTFE surface after modifications became rougher when compared to untreated PTFE. The peeled surfaces were also analyzed by SEM. The micrographs evidence that the energy absorbing mechanism is the plastic deformation of the tie-layer, which is responsible for obtaining high peel strengths.

Viscosity and Peel Strength of SMR 10-Based Pressure-Sensitive Adhesives

The viscosity and peel strength of a natural rubber-based pressure-sensitive adhesive was studied. One grade of natural rubber (SMR 10) and coumarone-indene resin were used as the elastomeric material and tackifier, respectively. Throughout the experiment, toluene was used as the solvent to prepare the adhesive. The effect of mastication time of rubber and tackifier concentration on the viscosity and peel strength of adhesive on various substrates was systematically investigated. The viscosity was measured using a HAAKE Rotary Viscometer. T-Test, 90° Adhesion To Steel (ATS), and 180° Adhesion To Steel (ATS) Tests were used to determine the peel strength of the adhesive. The results indicate that the viscosity of the adhesive increases with the resin content but decreases with mastication time. The peel strength generally increases with an increase in resin content except for the 20 min masticated sample. For all concentrations of the resin tackifier studied, the 10 min masticated sample exhibits the highest peel strength as compared to the corresponding values of the other masticated samples. This observation is attributed to the optimum wetting and formation of mechanical interlocking, and anchorage of the adhesive in pores and irregularities in the substrate for the former sample.