Increase In Peel Strength Research Articles

Experimental testing of composite T-Joints

Composite T-joints are adhesively bonded joints between a base plate and a panel normal to it. These are crucial, yet, they remain a structural weakness of marine composite structures. A new T-joint configuration, namely, bonding ties, has recently emerged but has never been experimentally characterised. Moreover, honeycomb cores have been favoured over foam for high-performance applications, but the former remains comparatively understudied. Consequently, this paper undertakes the mechanical testing of both foam and honeycomb-cored T-joints, using four configurations: resin fillets, bonding angles, bonding angles with fillets and bonding ties. The results show that (i) peel strength is independent of the core employed; (ii) both resin fillets and bonding ties achieve the lowest peel strength, and thus, bonding ties are not recommended; (iii) for foam-cored T-joints bonding angles and bonding angles with fillets respectively yield a 42% and 96% increase in peel strength compared to resin fillets; and (iv) for honeycomb-cored T-joints, an increase in peel strength of 46% and 84% compared to resin fillets is achieved for bonding angles and bonding angles with fillets, respectively. These findings provide novel insights into the strength of composite T-joints and may inform regulatory developments, future numerical studies and the design of marine T-joints.

The Effect of Cellulose Nanocrystal Reassembly on Latex-Based Pressure-Sensitive Adhesive Performance.

Different cellulose nanocrystal (CNC) forms (dried vs never-dried) can lead to different degrees of CNC reassembly, the formation of nanofibril-like structures, in nanocomposite latex-based pressure-sensitive adhesive (PSA) formulations. CNC reassembly is also affected by CNC sonication and loading as well as the protocol used for CNC addition to the polymerization. In this study, carboxylated CNCs (cCNCs) were incorporated into a seeded, semibatch, 2-ethylhexyl acrylate/methyl methacrylate/styrene emulsion polymerization and cast as pressure-sensitive adhesive (PSA) films. The addition of CNCs led to a simultaneous increase in tack strength, peel strength, and shear adhesion, avoiding the typical trade-off between the adhesive and cohesive strength. Increased CNC reassembly resulted from the use of dried, redispersed, and sonicated cCNCs, along with increased cCNC loading and addition of the cCNCs at the seed stage of the polymerization. The increased degree of CNC reassembly was shown to significantly increase the shear adhesion by enhancing the elastic modulus of the PSA films.

Adhesion Characterization and Enhancement between Polyimide-Silica Composite and Nodulated Copper for Applications in Next-Generation Microelectronics.

As the need for high-speed electronics continues to rise rapidly, printed wiring board (PWB) requirements become ever-more demanding. A typical PWB is fabricated by bonding dielectric films such as polyimide to electrically conductive copper foil such as rolled annealed (RA) copper and is expected to become thinner, flexible, durable, and compatible with high-frequency 5G performance. Polyimide films inherently feature a higher coefficient of thermal expansion (CTE) than copper foils; this mismatch causes residual thermal stresses. To attenuate the mismatch, silica nanoparticles may be used to reduce the CTE of PI. A nodulated copper surface can be used to enhance the Cu/PI adhesion by additional bonding mechanisms that could include a type of mechanical bonding, which is a focus of this study. In this investigation, a 90° peel test was used to measure the peel strength in copper/polyimide/copper laminates containing nodulated copper and polyimide reinforced with 0, 20, and 40 wt % silica nanoparticles. The influence of silica nanoparticles on the peel strength was quantitatively evaluated. Laminates incorporating polyimide films lacking silica nanoparticles had a ∼3.75× higher peel strength compared with laminates reinforced with 40% silica. Their failure surfaces were analyzed by using scanning electron microscopy (SEM), energy-dispersive X-ray analysis (EDX), and X-ray photoelectron spectroscopy to identify the mode of failure and to understand bonding mechanisms. The key bonding mechanism, mechanical interlocking, was achieved when the polyimide surrounded or engulfed the copper nodules when the laminate was created. Post-testing failure surface analysis revealed the presence of copper on the polyimide side and polyimide on the copper side, indicating mixed mode failure. An analytical model was developed to determine the impact of applied pressure, temperature, and time on the polyimide penetration and mechanical interlocking around the copper nodules. The model was validated by measuring the peel strength on another set of specimens fabricated using increased temperature and pressure that showed a 3× increase in peel strength compared to lower temperature/pressure processing conditions. This enhanced adhesion resulted from the lower polymer material viscosity at higher temperatures, which fosters deeper and more complete penetration around the copper nodules during processing at higher pressures for longer durations. The methodology of combining peel testing, viscosity and CTE measurement, SEM/EDX, surface chemical analysis, and penetration depth calculation developed herein enables the calculation of the desired processing parameters to enhance functionality and improve adhesion.

Carbon fiber reinforced polyethylene composite adhesive at elevated temperatures

The development of multi-layer-multi-material thermoplastic structures necessitates the bonding of dissimilar materials with varying mechanical, chemical, barrier, and thermal properties. Thermoplastic adhesives, such as maleic anhydride grafted polyethylene (PE-MAH), are advantageous over thermoset adhesives given their similar manufacturability, and numerous benefits as sustainable materials in compliance with strict environmental regulation in construction, automotive, and energy industries. A key drawback is that PE-MAH demonstrates weak adhesive properties at elevated temperatures. In this study, the adhesion strength of carbon fiber (CF) reinforced PE-MAH at elevated temperatures were evaluated using a novel method of T-peel test under a controlled environment. Significant improvements of 71% and 295% increase in peel strength at 90 °C and 110 °C, respectively, were achieved with CF reinforcement over neat PE-MAH. The improving mechanisms were discussed on both macro-level, i.e., enhanced peel zone and eliminating crazing, and micro-level, i.e., transferred stress and dispersed energy into micro peel zones. This study demonstrates the efficacy of tailoring the adhesion strength of thermoplastic composite adhesive for significantly improved performance at elevated temperatures.

Reducing Bonding Temperature and Energy Consumption in Electronic Packaging Using Flash Electro-Thermal Carbon Fiber Heating Elements.

Semiconductor packaging based on an epoxy molding compound (EMC) currently has several disadvantages including warpage, limited processing area, and variability that all negatively affect cost and production yield. We propose a facile EMC molding process method using a flash electro-thermal carbon fiber heating (FE-CH) device based on carbon fiber-based papers to manufacture an EMC molded to a copper substrate (EMC/Cu bi-layer package) via Joule heating, and using this device, a modified cure cycle that combines the conventional cure cycle (CCC) with rapid cooling was performed using FE-CH to reduce the curvature of the EMC/Cu bi-layer package. Compared to the conventional hot press process, which uses 3.17 MW of power, the FE-CH process only uses 32.87 kW, resulting in a power consumption reduction of over 100 times when following the CCC. Furthermore, the FE-CH-cured EMC/Cu bi-layer package exhibits mechanical properties equivalent to those of a hot press-cured specimen, including the degree of cure, elastic modulus, curvature, bonding temperature, residual strain, and peel strength. The modified cure cycle using the FE-CH results in a 31% reduction in residual strain, a 32% reduction in curvature, and a 47% increase in peel strength compared to the CCC, indicating that this new process method is very promising for reducing a semiconductor package's price by reducing the process cost and warpage.

Bio-Based Adhesives Formulated from Tannic Acid, Chitosan, and Shellac for Packaging Materials

The aim of this study was to develop bio-based adhesives that can be used for various packaging papers. In addition to commercial paper samples, papers produced from harmful plant species in Europe, such as Japanese Knotweed and Canadian Goldenrod, were used. In this research, methods were developed to produce bio-based adhesive solutions in combinations of tannic acid, chitosan, and shellac. The results showed that the viscosity and adhesive strength of the adhesives were best in solutions with added tannic acid and shellac. The tensile strength with adhesives of tannic acid and chitosan was 30% better than with commercial adhesives and 23% for combinations of shellac and chitosan. For paper from Japanese Knotweed and Canadian Goldenrod, the most durable adhesive was pure shellac. Because the surface morphology of the invasive plant papers was more open and had numerous pores compared to the commercial papers, the adhesives penetrated the paper structure and filled the voids. There was less adhesive on the surface and the commercial papers achieved better adhesive properties. As expected, the bio-based adhesives also showed an increase in peel strength and exhibited favorable thermal stability. In summary, these physical properties support the use of bio-based adhesives use in different packaging applications.

Electronic Packaging Enhancement Engineered by Reducing the Bonding Temperature via Modified Cure Cycles.

Semiconductor packaging continues to reduce in thickness following the overall thinning of electronic devices such as smartphones and tablets. As the package becomes thinner, the warpage of the semiconductor package becomes more important due to the reduced bending stiffness and driven by thermal residual stresses and thermal expansion mismatch during the epoxy molding compound (EMC) curing to create the package. To address this packaging reliability issue, in this study, we developed a modified cure cycle that adds a rapid cooling step to the conventional cure cycle (CCC) to enhance the reliability of the EMC molded to a copper substrate (EMC/Cu bi-layer package) by lowering the bonding temperature of the EMC/Cu bi-layer package. Modeling of the package via Timoshenko theory including effective cure shrinkage allowed the rapid cooling step to be quantified and confirmed via experiments. The modified cure cycle resulted in a 26% reduction in residual strain, a 27% reduction in curvature, and a 40% increase in peel strength compared to the CCC, suggesting that this is an effective new method for managing warping effects in such packaged structures.

Evaluation of the influence of three-dimensional printing conditions on peel resistance and surface roughness of flexible polymer-textile composites

Extensive fashion and textiles research have adopted fused filament fabrication in three-dimensional printing. However, much research has dedicated itself to experimenting with rigid materials that lack the capability to mimic conventional textile-like garments. The commercialization of thermoplastic polyurethane/elastomers have posed greater potentials for developing flexible polymer-textile composites. Such materials will enable the creation of ergonomically designed textiles with optimized flexibility and elasticity aimed for garments. This study examines the influence of polymers, textile surface roughness, and nozzle temperature on peel resistance and polymer coefficient of friction/surface roughness. T-peel tests (ISO 11339:2022), cross-sectional microscopic image analysis, and a KES-FB4-A surface tester were used to evaluate the surface quality and peel resistance between polymer-textile assemblies. Our results revealed thermoplastic-polyurethane-knitted combinations to demonstrate superior peel resistance owing to knitted structure’s pore structure and thermoplastic polyurethane’s lower melting temperature. Moreover, a significant increase in peel strength was found at 260°C (above recommended printing temperature) in thermoplastic-polyurethane-knitted fabrics at 3.24 N/mm. While the coefficient of friction remained similar, a rougher surface quality was discovered at higher temperatures in thermoplastic polyurethane at 3.85 μm warp/4.35 μm weft. In thermoplastic elastomer, the roughest surface was found at 240°C measuring 3.65 μm warp/3.37 μm weft. This study fills a lack of research into flexible polymer-textile composites by suggesting parameters for achieving an equilibrium between optimal adhesion and polymer layer surface quality.

Designing a corrosion resistance system using modified graphene oxide-epoxy microcapsules for enhancing the adhesion strength of the epoxy coatings

New microencapsulated material with advanced corrosion resistance activity and superior adhesion strength on the steel sample was synthesized by in-situ polymerization. In this process, urea-formaldehyde was used as capsule shell material for encapsulating modified graphene oxide. The formation of microcapsules was effectively evidenced by FT-IR, SEM, and TGA-DSC analyses. Initially, graphene oxide was modified by the adsorption of Catharanthus roseus L. (C.R) leaves extract and characterized by FT-IR, SEM, EDX, and DFT studies. GO-C.R and UF-GO-C.R (microcapsules) were separately impregnated into epoxy resin and fabricated on the steel substrates. The anti-corrosion performance of UF-GO-C.R/Epoxy in comparison with neat GO-C.R/Epoxy coated sample was evaluated by electrochemical impedance spectroscopy (EIS) and salt spray test. Results reveal that UF-GO-C.R microcapsules in epoxy matrix showed the protection efficiency of 83.6 % after the immersion period of 7 days in 3.5 % NaCl solution which was relatively higher than those with neat GO-C.R. In addition, the coating loaded with UF-GO-C.R microcapsules showed improvement in the adhesion of epoxy coatings on the steel surface which was evident from the increase in peel strength (290 N) through peel-off adhesion test.

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.

Si-DLC膜とPMMAまたはPEEK部材との付着・剥離試験における付着力増加要因の調査

In order to reduce the peel resistance of molded resin from molds by applying hard thin films, we investigated the factors that cause the large peel resistance between Si-DLC and PEEK, against the background of the growing need for super engineering plastics in CFRTP molding. In the previous study, the peel resistance between Si-DLC and PEEK was about 20 times higher than that between Si-DLC and PMMA in the adhesion-peel test with a temperature history in which the resin was melted, and the reason was thought to be the difference in bond strength and the increase in bond strength due to oxidation of Si-DLC. In the adhesion-peeling test without melting the resin, the difference in bond strength and the increase in bond strength due to oxidation of Si-DLC should contribute to the increase in peel strength. Therefore, we conducted adhesion-peel tests without melting resin and without temperature history using Si-DLC and PEEK, and considered the possibility that these factors may be responsible for the increase in peel strength. Experimental results showed that peel between PEEK and Si-DLC generates lower peel resistance than between PMMA and Si-DLC, as long as there is no melting and resolidification process.

Light-Activated Adhesion and Debonding of Underwater Pressure-Sensitive Adhesives.

Pressure-sensitive adhesives (PSAs) such as sticky notes and labels are a ubiquitous part of modern society. PSAs with a wide range of peel adhesion strength are designed by tailoring the bulk and surface properties of the adhesive. However, designing an adhesive with strong initial adhesion but showing an on-demand decrease in adhesion has been an enduring challenge in the design of PSAs. To address this challenge, we designed alkoxyphenacyl-based polyurethane (APPU) PSAs that show a photoactivated increase and decrease in peel strength. With increasing time of light exposure, the failure mode of our PSAs shifted from cohesive to adhesive failure, providing residue-free removal with up to 83% decrease in peel strength. The APPU-PSAs also adhere to substrates submerged underwater and show a similar photoinduced decrease in adhesion strength.

Rubber-to-steel adhesives based on natural rubber grafted with poly(acetoacetoxyethyl methacrylate)

Abstract The present study aimed to develop adhesives for bonding natural rubber (NR) to steel based on modified NR bearing grafted poly(acetoacetoxyethyl methacrylate), NR-g-PAAEM. Graft copolymers of NR-g-PAAEMs were prepared by emulsion polymerization at 50 °C. A significant increase in the polar component of NR from 1.62 to 6.84 mN/m was observed after grafting modification, indicating an increase in its hydrophilicity. After that, both one-coat and two-coat adhesives (or adhesive/cover-coat system) were then prepared, using polyisocyanate (poly‐HDI) as a bonding agent. The NR/steel joints were made by vulcanization bonding, using the NR-g-PAAEM adhesive in the presence or absence of cover-coat layer. The results reveal that the NR/steel joint bonded using the two-coat system exhibited higher peel strength than that bonded using the one-coat system. For the two-coat system, the peel strength of 874 N/m was attained when the NR-g-PAAEM adhesive was used in combination with the NR cover-coat. The replacement of the NR cover-coat by the NR-g-PAAEM20 cover-coat led to 49% increase in peel strength of the NR/steel joint. Moreover, the X-ray photoelectron spectroscopy analysis also indicated the formation of urethane-like bonding in this adhesive system, as a result of the reaction between the poly‐HDI and metal oxides on the steel surface.

A Modular Strategy for Functional Pressure Sensitive Adhesives.

A modular approach to synthesizing functional pressure sensitive adhesives (PSAs) was introduced, wherein a modifiable acrylic PSA copolymer was synthesized by copolymerizing common PSA monomers with 6 mol % glycidyl methacrylate, allowing for subsequent functional group modification via the pendant epoxide functionality. This postmodification technique has the advantage of allowing the installation of a variety of functional groups relevant to adhesion, without variation of molecular weight. Because comparisons of cohesive and adhesive performance of candidate PSAs can be complicated by molecular weight differences, this strategy simplifies direct comparisons of the effects of functional groups on performance. As a proof of concept, a mussel-inspired catecholic PSA was synthesized by postreaction of the epoxide scaffold polymer with a thiol-modified catechol, allowing the effect of catechol on underlying structure-property relationships to be determined without variation in molecular weight. The mechanical performance of catecholic PSA was compared to relevant control PSAs by using industry-standard 180° peel and static shear tests, revealing an increase in peel strength achieved through catechol modification. Moreover, we observed an unexpected enhancement in PSA cohesive strength attributed to oxidation of catechol, which cannot be attributed to differences in molecular weight, a common source of changes in PSA cohesive strength.

Influence of Microstructure in Near‐Surface Areas of Feedstocks on the Bond Strength of Roll Bonded Aluminum Clads

This work determines the impact of the different grain sizes and oxide layers in near‐surface areas of aluminum semi‐finished products on the bond strength after warm roll bonding. To adjust the grain microstructures in the initially twin‐roll cast feedstocks, they are differently treated to generate different grain sizes in the near‐surface areas. Semi‐finished products of the same near‐surface microstructure are then joined by warm roll‐bonding. In industrial applications, it is common to influence the bond strength of clads by applying a post heat treatment. Therefore, a part of the samples was annealed after warm roll bonding. Post‐treated samples with coarser grain size exhibit up to two times higher peel strength than untreated samples. Higher peel strengths of the post‐treated samples can be explained both by improved diffusion bonding due to heat exposure, and by recrystallization and grain coarsening of microstructure in the interface of sheets. Increase in peel strength of the composites made of feedstocks with coarser grains can be the result of stronger grain rotation, which damages oxide layer on the interface. To summarize, twin‐roll cast and soaked material with the coarsest grains in the near‐surface areas is the best feedstock for roll‐bonding, if an additional heat treatment is applied.

Effect of Intermetallic Compound Layer on Peel Strength and Crack Propagation Behavior in Cu/Al/Cu Clad Composites

The effects of interfacial modification in tri-layered Cu/Al/Cu composites by heat treatment on interface stability and crack propagation were investigated. In order to investigate the crack path during the peel test, the intermetallic compound layer with the propagating crack was examined using electron backscatter diffraction (EBSD) analyses. The increase of peel strength from 7.8 to 9.1 N/mm in the tri-layered Cu/Al/Cu composite in the presence of thin discontinuous intermetallic compounds with heat treatment at 200–300 °C was accompanied by the increase of electrical conductivity from 65.3% IACS (International Annealed Copper Standard) to 66.8% IACS. Continuous intermetallic layers consisting of Al2Cu, AlCu, and Al4Cu9 were found in Cu/Al/Cu heat-treated at temperatures above 350 °C and its thickness increased rapidly and reached up to 35.2 μm at 500 °C. The peel strength drastically decreased to 5.75 N/mm after heat treatment at 400 °C, and it gradually increased as the heat treatment temperature was increased to 450 °C (5.91 N/mm) and 500 °C (6.16 N/mm). The increased peel strengths after heat treatment at 450 and 500 °C were accompanied by pronounced serrations of the peel strength–displacement curves. The amplitude of serration increased substantially with increasing annealing temperature from 400 to 500 °C. The major crack along the interface propagated, mostly along the Al2Cu/AlCu boundary with some inclined cracks, propagated through the AlCu and Al4Cu9 intermetallic compound layers. The repetition of crack propagation along the interface and crack deflection through the intermetallic layer as an inclined crack induced the serrated surface on the peeled-off Cu plate, enhancing the interface toughening.

Fast packaging of glass-based microfluidic chip using adhesive polyurethane material

A fast packaging method is proposed to fabricate the packaging of glass-based chips using polyurethane (PU). The performance properties of this material can be justified by the A-glue/B-glue weight ratio. To choose an appropriate proportion of glues, water contact angle, 90° peel strength, and shore hardness are employed to measure the PU material. By increasing the A-glue/B-glue weight ratio, the hardness of the PU board decreases, the peel strength increases, and the contact angle increases first and then decreases. Based on the performance of PU material, an A-glue/B-glue weight ratio of 3.6:1 is adapted to package the glass chip. However, the softness of PU led to the design and implementation of a stable plate to protect the chip. Mixing application experiment results verified the validity of the PU packing method. After comparing three packaging method, the glass-PU chip packing method was the most efficient and economical. Test results indicate that the PU Packing method can be widely used in the fabrication of microfluidic chips.

Evaluation on Microstructures and Mechanical Properties in Friction Stir Welded Lap Joints of Invar 42/SS 400

This study evaluated the microstructures and mechanical properties of friction stir welded lap joints. Invar 42 and SS 400 as experimental materials were selected, and friction stir welding was carried out at tool rotation speed of 200 rpm and welding speed of 100 mm/min. Applying the friction stir welding was notably effective to reduce the grain size of the stir zone, consequently, the average grain size of Invar 42 was reduced from 11.5 μm in the base material to 6.4 μm in the stir zone. Joint interface between Invar 42 and SS 400 showed a sound weld without voids and cracks, and the intermetallic compounds with Ll₂ type in lap joint interface were partially formed with size of 100 nm. Also, the hook, along the Invar 42 from SS 400, was formed at advancing side, which directly affected an increase in peel strength.

Property modification of a silicone acrylic pressure-sensitive adhesive with oligomeric silicone urethane methacrylate

A silicone acrylic pressure-sensitive adhesive (SPSA) was synthesized using a silicone macro-azo-initiator as an adhesive for low surface energy substrates. The SPSA had a high peel strength value on an SUS (steel use stainless) substrate due to its low surface energy; however, it had very low peel strength values on low surface energy substrates such as PP and PE. In this study, a silicone urethane dimethacrylate (SiUDMA) oligomer was synthesized as a modifier for the SPSA. The SiUDMA had a much lower viscosity and a slightly higher surface energy than the SPSA. The addition of SiUDMA increased the peel strength of the SPSA regardless of the substrate. In the case of the PP and PE substrates, the increase of peel strength with SiUDMA addition was remarkably large when compared to the SUS substrate because SiUDMA significantly reduced SPSA viscosity and improved its fluidity, consequently facilitating the wetting of the rough surfaces of PP and PE. The rough surfaces of PP and PE could also aid the spreading of SiUDMA-modified SPSA and enlarge the interfacial area. On the other hand, UV curing of SiUDMA and the SiUDMA-modified SPSA resulted in a serious decrease in the peel strength on the PP and PE substrates due to the decrease in the fluidity of the SPSA material, but the SAFT of SPSA increased with UV irradiation.

Influence of Phase Separation on Performance of Graft Acrylic Pressure-Sensitive Adhesives with Various Copolyester Side Chains.

Acrylic pressure-sensitive adhesives with various polyester side-chain lengths were synthesized to investigate the effect of branching on phase separation and polymer mechanical performance. The polyester macromonomers (MMs) were produced through ring-opening co-polymerizations of l-lactide (l-LA) and ε-caprolactone (ε-CL) initiated with 2-hydroxyethyl methacrylate (HEMA), which provides the polyester chains with terminal vinyl groups. By varying the HEMA content, a range of MM chain lengths constructed from L10C4 (five l-LA and four ε-CL units) to L100C40 were obtained at a constant monomer mole ratio. Copolymerization of 2-ethylhexyl acrylate and acrylic acid with these MMs at constant mass composition provided a series of comb copolymers consisting of acrylic backbones with polyester branches of various chain lengths. Characterization of thin films cast from the polymers using thermal analysis and scanning probe microscopy showed a transition from a homogeneous phase to the formation of distinct microphases with increasing branching chain lengths. Rheological analysis of the linear viscoelastic responses was also used through small-amplitude oscillatory shear, and dynamic master curves were constructed by time–temperature superposition. The rheological data were also consistent with phase separation for the longer side-chain lengths of L50C20 and L100C40. The extra elastic contribution at low frequency and the temperature dependence of aT both show obviously effect of separated phases. Performance testing of polymer films showed that the chain extension resulted in a significant increase in both peel strength and shear resistance, which was accompanied by a modest decrease in film tackiness. The results demonstrate that tailoring branch chain structures provide a promising means for controlling the properties of the high-biomass content adhesive polymers.