Viscoelastic and Processing Effects on the Fiber-Matrix Interphase Strength. Part III. The Effects of Postcure

A novel method for tailoring the interphase of carbon fiber-polymer composites by resistive electric heating is presented. The single-fiber fragmentation test is used to investigate the adhesion and fracture properties of the interphase. Electric resistive heating is shown to increase adhesion and toughness at the interphase region. In analyzing the results, the strength and fracture energy of the interphase are related to the thermal postcure conditions created by resistive electric heating. For this purpose, a difference analysis method is used to obtain a numerical solution for the heat conduction problem in the single-fiber test specimen and the temperature distributions are determined. Improvements obtained by using resistive electric heating of the carbon fiber are compared with those obtained by postcuring of the whole sample via convective thermal postcuring. The results obtained using these two different postcure methods seem to be similar.     

Adhesion: Comparison Between Physico-chemical Expected and Measured Adhesion of Oxygen-plasma-treated Carbon Fibers and Polycarbonate

The adhesive interaction between oxygen-plasma-treated, polyacrylonitrile-based, high-tensile-strength carbon fibers and a polycarbonate matrix has been studied. Several models have been used to predict the impact of the plasma treatment process on the strength of adhesion between both jointing partners. These approaches have been the thermodynamic work of adhesion which was calculated from the solid surface tensions, based on the results of contact angle measurements versus test liquids, the contact angle which was directly obtained via polycarbonate melt droplets on single carbon fibers and the zeta (?)-potential data provided by streaming potential measurements. The results have been compared with the interfacial shear strength determined from the single-fiber fragmentation test. Additionally, the single-fiber tensile strength of the oxygen-plasma-treated carbon fibers was determined.

We confirmed that any physico-chemical method on its own fails to describe exactly the measured adhesion. However, for the investigated system, the conscientious interpretation of the data obtained from wetting measurements, in conjunction with the thermodynamic approach, is sufficient to predict the success of a modification technique which has been applied to one component in order to improve adhesion.     

Effect of postmold curing on plastic IC package reliability

Nearly all IC encapsulating compounds require a postcure treatment to ensure integrated circuit (IC) package reliability. The issue of postcuring and this effect on IC package reliability performance are considered in this article. We examined the development of various encapsulating compounds' properties with various durations of postcure time. It was found that the mechanical strength, glass transition, and adhesion strength were increased with increasing duration of postcure time compared to as-molded samples. However, these properties could reach ultimate values after postcuring for 1–2 h. It was also seen that the moisture uptake was increased for samples that have been post-mold-cured due to increased crosslinking density causing a large free volume in the glassy polymer matrix. C-mode scanning acoustic microscopy (C-SAM) analyses were performed to investigate the effect of the duration of postcure time on the IC package reliability and they show a good relationship with the evolution of the compound's properties during the postcure process. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 69: 2187–2193, 1998     

The influence of the interphase on composite properties: Poly(ethylene-co-acrylic acid) and poly(methyl vinyl ether-co-maleic anhydride) electrodeposited on graphite fibers

The electrodeposition of saturated copolymers onto carbon fibers is investigated, focusing particular attention on improvement of shear and impact properties of the corresponding composites. Carbon fibers are electrocoated with poly(ethylene-co-acrylic acid) and poly(methyl vinyl ether-co-maleic anhydride) from aqueous media, and fabricated into epoxy composites. The results of interlaminar shear strength (ILSS) tests, initially employed to assess fibermatrix adhesion, are vitiated by the occurrence of mixed-mode failure. Interfacial shear strength (IFSS) is hence evaluated by stressing single-fiber composite specimens to obtain ultimate aspect ratios of the fiber fragments. The data are combined with fiber strengths by a recently developed statistical theory (1) to yield a distribution for IFSS. Both copolymer interphases improve fiber-matrix bonding to an extent greater even than that obtained with commercial fiber surface treatment. Good fiber-matrix adhesion is further apparent from SEM studies of fractured ILSS test specimens. A key to this improved adhesion is the interpenetration of matrix resin and interphase polymer, revealed by electron microprobe analysis (2). Notched Izod impact strength is also increased over uncoated-fiber composites. These copolymer interphases behave as deformable interlayers, absorbing impact energy and blunting the growing crack tip. Further energy is absorbed in deflecting the crack through a more tortuous path. Simultaneous improvements in impact and shear strengths are thus obtained, which may be further enhanced by optimizing the electrodeposition parameters and the coating thickness. The influence of the interphase on composite properties is better understood from this study, paving the way for refinement in interphase design.     

Effects of curing agent and carbon black filler loading on carbonization behavior of phenolic‐carbon black composites

The effects of curing agent (p‐toluene sulfonic acid, PTSA) concentration, i.e., 1.0, 1.5, 2.0, 2.5, and 3.0 wt% on neat phenolic resin (in absence of carbon black) were investigated through the measurement of density, weight loss, linear shrinkage, and mechanical properties under compression mode to understand the carbonization behavior of carbon–carbon composite. The study was carried out after curing, postcuring, and carbonization. Also, thermogravimetric analysis was used to study the effects of curing agent concentration on thermal stability and kinetic parameters (i.e., activation energy, order of decomposition, pre‐exponential term, etc). The kinetic parameters were evaluated by using four single heating rate techniques namely Friedman, Coats‐Redfern, Freeman‐Carroll, and Chang methods. Further, to study the effects of both carbon black filler loading and carbonization temperature, phenolic‐carbon black composites were prepared at the loading of 10, 20, 30, 40 wt% using 1.5 wt% of PTSA. These were also investigated through density, weight loss, and shrinkage measurements after curing, postcuring, and carbonizing at the temperature of 600, 1000, and 1400°C in nitrogen atmosphere. To analyze the evolution of carbon phase X‐ray diffraction study was carried out for the carbonized samples. Finally, cured, postcured and carbonized composite samples were subjected to compression tests to study the compression strength and modulus. POLYM. COMPOS., 31:2069–2078, 2010. © 2010 Society of Plastics Engineers     

Pultruded fiber reinforced blocked polyurethane (PU) composites. II. Processing variables and dynamic mechanical properties

Unidirectional fiber reinforced blocked polyurethane (PU) composites have been prepared by the pultrusion process. The effects of processing variables on the mechanical properties and dynamic mechanical properties of fiber reinforced PU composites by pultrusion have been studied. The processing variables investigated included pulling rate (in-line speed), die temperature, postcure time and temperature, and filler type and content. The dynamic mechanical properties of the composites produced by the process were studied utilizing dynamic mechanical spectrometer. Results show that the composites possessed various optimum pulling rates at different die temperatures. From the DSC data analysis, swelling ratio, and mechanical properties, the optimum die temperature was determined. It was found that the mechanical properties increase with filler content for various types of filler. The increasing of mechanical properties depends on the optimum postcure temperature and time. However, the properties decreased for longer postcure times since the composite materials were degraded. The glass-transition temperature (T_g) increased slightly and the damping peak (tan δ) was broadened due to fiber reinforcement. The dynamic mechanical moduli (G′, G″) of pultruded PU composites are apparently higher than those of the matrices. The moduli (G′, G″) increase with increasing fiber and filler content, and the damping peak becomes broad. Effect of postcuring on the degree of crosslinking, T_g, and dynamic modulus will be discussed.     

Adhesion: Comparison Between Physico-chemical Expected and Measured Adhesion of Oxygen-plasma-treated Carbon Fibers and Polycarbonate

The adhesive interaction between oxygen-plasma-treated, polyacrylonitrile-based, high-tensile-strength carbon fibers and a polycarbonate matrix has been studied. Several models have been used to predict the impact of the plasma treatment process on the strength of adhesion between both jointing partners. These approaches have been the thermodynamic work of adhesion which was calculated from the solid surface tensions, based on the results of contact angle measurements versus test liquids, the contact angle which was directly obtained via polycarbonate melt droplets on single carbon fibers and the zeta (ς)-potential data provided by streaming potential measurements. The results have been compared with the interfacial shear strength determined from the single-fiber fragmentation test. Additionally, the single-fiber tensile strength of the oxygen-plasma-treated carbon fibers was determined.

We confirmed that any physico-chemical method on its own fails to describe exactly the measured adhesion. However, for the investigated system, the conscientious interpretation of the data obtained from wetting measurements, in conjunction with the thermodynamic approach, is sufficient to predict the success of a modification technique which has been applied to one component in order to improve adhesion.     

Influence of Cure Conditions on the Adhesion of Rubber Compound to Brass-plated Steel Cord. Part II. Cure Time

The effect of the cure time of a rubber compound on the adhesion with brass-plated steel cord was investigated. The formation, growth and degradation of the adhesion interphase formed between the rubber compound and brass-plated steel cord was also observed as well as the formation of a weak boundary layer in the rubber near the adhesion interphase. With increase in the cure time from a fourth to four times of t ₉₀, the pull-out force after vulcanization increased significantly up to one-half of t ₉₀ followed by a slight increase to t ₉₀, and then decreased slowly with further increase in cure time. This decrease in pull-out force upon prolonged vulcanization may be explained by the severe degradation of rubber compound attached to the adhesion interphase. Also, upon prolonged vulcanization, the adhesion interphase with a rich ZnS layer may act as a barrier to copper diffusion which is required to form the adhesion interphase of copper sulfide. After thermal aging of the adhesion samples, the pull-out force decreased in comparison with that of the unaged. The decrease of pull-out force after thermal aging stemmed mainly from the decline of tensile properties after thermal aging. The adhesion after humidity aging was different from that after thermal aging. Upon increasing the cure time to one-half of t ₉₀, the pull-out force increased. But a further increase in the cure time caused a decline in pull-out force. This phenomenon can be explained by the degradation of the adhesion interphase. At longer cure time, a severe growth of copper sulfide and a large amount of dezincification were observed in the adhesion interphase. At shorter cure time, a significant growth of copper sulfide in the adhesion interphase does not occur, whereas the formation a of a ZnS layer appeared after humidity aging. With increasing cure time, the formation of a weak boundary layer in the rubber near the adhesion interphase increased, resulting in the cohesive failure of the rubber layer. The proper formation of the adhesion interphase and the good physical properties of the rubber compound at optimum cure time can lead to the high retention of adhesion.     

CHARACTERIZATION, PROPERTIES, AND PROCESSING OF LARC PETI-5® AS A HIGH-TEMPERATURE SIZING MATERIAL: III. ADHESION ENHANCEMENT OF CARBON/BMI COMPOSITES

A phenylethynyl-terminated imide oligomer (LaRC PETI-5®) with a number average molecular weight of 2500 g/mol has been applied onto the surfaces of PAN-based carbon fiber tows and woven carbon fabrics as a sizing material to introduce an interphase between the fiber and matrix in carbon/BMI composites. The adhesion between the fiber and matrix was enhanced by the presence of a properly processed LaRC PETI-5® interphase. The results showed that when LaRC PETI-5® was sized and processed at 150°C, the interfacial shear strength (IFSS) of unidirectional IM7/BMI composite measured by using a microindentation technique and the interlaminar shear strength (ILSS) of a carbon/BMI composite measured by short beam shear test were markedly improved by about 35% and 66%, respectively, in comparison with the unsized counterparts. The adhesion enhancement strongly depends not only on the presence or absence of LaRC PETI-5® sizing interphase but also on the temperature profile applied to the sizing before composite fabrication. Both of these factors critically influence the physical and chemical state of the sizing material. Scanning electron microscopic observations of the composite fracture surfaces support the improved interfacial property of carbon/BMI composites.     

An adhesion test method for spray‐applied fire‐resistive materials

Adhesion of spray‐applied fire‐resistive materials (SFRMs) to steel structures is critical in enabling a building to remain functional during a fire for a specific period of time for life safety and fire department access. Empirical tests such as ASTM E736 have been widely adopted by the industry in an effort to ensure sufficient bonding between SFRMs and steel structures. ASTM E736 assesses the adhesion of SFRMs by using tensile strength, a failure parameter that depends on the test geometry and has limited use for predicting failure in other geometries and conditions. These limitations have produced an urgent need for a scientifically based adhesion test method. In this paper, we propose a new test method that would provide more fundamental information that is independent of test geometry and has predictive capability. This paper utilizes a fracture energy‐based failure criterion (G_C) to characterize the adhesion between SFRMs and steel. The theoretical basis of this test method is validated by experimental compliance tests. The dependence of G_C on various test variables such as specimen width, substrate type, SFRM formulation, and test rate are examined. A comparison between this new test method, and the current widely used strength‐based test method is also presented. Copyright © 2010 John Wiley & Sons, Ltd.     

Dynamic mechanical analysis of fiber-reinforced phenolics

Dynamic mechanical analysis (DMA) was used to investigate the thermomechanical behavior and the effects of postcuring on a range of glass-reinforced phenolics. The materials examined were a pure resol (reinforced with S- and E-glass), a pure novolac (reinforced with S-glass), and three derivatives of the resol and/or novolac: a resol/novolac blend, a phenolic–furan graft copolymer, and a rubber-modified resol (all reinforced with S-glass). The blend and copolymer were prepared to obtain phenolic resins with improved impact strength, without degeneration of their high-temperature performance. They have a more loosely crosslinked structure compared to the pure resol or novolac. The rubber-modified resol was prepared with the intention of reducing the brittleness of the resin structure by incorporating an elastomeric phase within the resol resin matrix. It was found that the stiffness and glass transition temperature (T_g) of the materials could be increased by postcuring, which also produced a decrease in their damping capacity. Knowing that the postcure process is a function of time and temperature, a master curve was constructed that allowed prediction of the T_g of the resol/novolac blend over a broad range of postcure times and temperatures. The effect of frequency on the storage modulus of the pure resol (S-glass), copolymer, and blend was also studied from 0.01 to 100 Hz. Master curves were constructed by time–temperature superpositioning that allowed prediction of the storage modulus at times and temperatures that are not experimentally accessible. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 649–658, 1999     

Residual Stresses in Microcomposites and Macrocomposites

Existing models for built-in residual stresses in composite materials are reviewed and discussed. In particular, the thermal longitudinal stress present in the fiber prior to a single-fiber fragmentation experiment is studied using various model composite data. It is found that this stress is typically compressive in nature and that, quantitatively, it depends on the fiber content, the degree of undercooling, and the thermoelastic constants of the fiber and the matrix. In the case of single-fiber composites (or microcomposites), the thermal longitudinal stress present in the fiber is high enough to either induce fiber sinewave buckling (such as in E-glass/epoxy), or extensive fiber fragmentation (such as in graphite HM/polypropylene) that may then be used to measure the dependence of compressive fiber strength upon length. This has to be accounted for in quantitative models that calculate interfacial adhesion parameters using single-fiber tests, such as the fragmentation test or the microbond test. Implications for high fiber content composites (or macrocomposites) are discussed.     

一种新型高光注塑模具加热方法的模拟和实验研究

采用电加热方式的高光注塑模具可以有效消除传统注塑成型过程中塑料件的熔接痕、浮纤、银纹等缺陷。然而直接将电加热棒插入模具孔中,由于间隙处的空气,大大降低了传热速度,提出一种新型电加热方法,通过在电加热棒与模具之间填充一种导热液,改变电加热棒与模具之间的接触状况,建立三维传热模型,并通过模拟和实验研究,证明了这种方法可以提高40%的加热效率,同时还能降低电加热棒内部40%的温度。     

Chain-extended bismaleimides. II. A study of chain-extended bismaleimides as matrix elements in carbon fiber composites

A series of chain-extended bismalemide resins as matrix elements in carbon fibers were cured and characterized in terms of their thermal and thermomechanical properties. The cured resins were stable up to 430°C and EDABMI/MDA has the highest T^g value and the lowest loss modulus value. To understand the compatibility and the degree of adhesion between the resin and the fiber, their surface properties were determined in terms of the surface energy component and single-fiber pull-out tests. The surfaces of the resins were found to have a basic character. The resins containing ether groups have a higher degree of basicity than does the resin containing methylene groups. Similarly, an increasing trend in the interlaminar shear strength (ILSS) and the work of adhesion values were observed with the increasing number of the ether groups in the resin structure. © 1996 John Wiley & Sons, Inc.     

Influence of Cure Conditions on the Adhesion of Rubber Compound to Brass-plated Steel Cord. Part I. Cure Temperature

The effect of the cure temperature of rubber compound on the adhesion with brass-plated steel cord was investigated in conjunction with the formation, growth and degradation of the adhesion interphase formed between the rubber compound and brass-plated steel cord. With increasing cure temperature from 130°C to 190°C, the pull-out force after cure decreased linearly. This decrease in adhesion force at higher temperature may be explained by the limitation of the mass transfer of vulcanizing agents into the adhesion interphase and/or rubber compound near the adhesion interphase, resulting in a deficiency of sulfur due to the fast cure of the rubber compound which significantly retards the diffusion of vulcanizing chemicals. Also, at a high temperature, an adhesion interphase with a ZnS-rich layer, which may act as a barrier to copper diffusion for the formation of the adhesion interphase of copper sulfide, was formed. After thermal aging of the adhesion samples, the pull-out force decreased in comparison with that of the unaged. The decrease of pull-out force after thermal aging stemmed mainly from the decline of the tensile properties after thermal aging. The adhesion property after humidity aging was completely different from that after thermal aging. With increase in the cure temperature to 160°C, the pull-out force increased. But further increase in the cure temperature caused a decline in pull-out force. This phenomenon can be explained by the degradation of the adhesion interphase. At lower cure temperatures, a severe growth of copper sulfide and a large extent of dezincification were observed in the adhesion interphase. At higher cure temperatures, a significant growth of copper sulfide in the adhesion interphase appeared. The proper formation of the adhesion interphase and good physical properties of the rubber compound at a moderate cure temperature can result in high retention of adhesion properties.     

Influence of Cure Conditions on the Adhesion of Rubber Compound to Brass-plated Steel Cord. Part I. Cure Temperature

The effect of the cure temperature of rubber compound on the adhesion with brass-plated steel cord was investigated in conjunction with the formation, growth and degradation of the adhesion interphase formed between the rubber compound and brass-plated steel cord. With increasing cure temperature from 130°C to 190°C, the pull-out force after cure decreased linearly. This decrease in adhesion force at higher temperature may be explained by the limitation of the mass transfer of vulcanizing agents into the adhesion interphase and/or rubber compound near the adhesion interphase, resulting in a deficiency of sulfur due to the fast cure of the rubber compound which significantly retards the diffusion of vulcanizing chemicals. Also, at a high temperature, an adhesion interphase with a ZnS-rich layer, which may act as a barrier to copper diffusion for the formation of the adhesion interphase of copper sulfide, was formed. After thermal aging of the adhesion samples, the pull-out force decreased in comparison with that of the unaged. The decrease of pull-out force after thermal aging stemmed mainly from the decline of the tensile properties after thermal aging. The adhesion property after humidity aging was completely different from that after thermal aging. With increase in the cure temperature to 160°C, the pull-out force increased. But further increase in the cure temperature caused a decline in pull-out force. This phenomenon can be explained by the degradation of the adhesion interphase. At lower cure temperatures, a severe growth of copper sulfide and a large extent of dezincification were observed in the adhesion interphase. At higher cure temperatures, a significant growth of copper sulfide in the adhesion interphase appeared. The proper formation of the adhesion interphase and good physical properties of the rubber compound at a moderate cure temperature can result in high retention of adhesion properties.     

Role of functional groups on the microwave attenuation and electric resistivity of activated carbon fiber cloth

Virgin activated carbon fiber cloth (ACFC) samples with select degrees of activation/porosity were treated with nitric and sulfuric acids or with hydrogen. Composition, microwave attenuation constant and electric resistivity results for these samples are provided. On average, acid treatment resulted in a 677% increase in oxygen content, 89% decrease in microwave attenuation constant, and 3200% increase in electrical resistivity when comparing these properties to the corresponding ones in the virgin samples. However, hydrogen treatment resulted in a 72% decrease in oxygen content, 50% increase in microwave attenuation constant, and 63% decrease in electrical resistivity, when comparing these properties to the corresponding ones in the virgin samples. These results indicate that conduction loss dominates over the polarization loss for microwave attenuation in ACFC. Increasing the oxygen content reduces the ACFC’s ability to absorb microwaves and is expected to make ACFC more difficult to heat with microwaves. However, decreasing the oxygen content allows the ACFC to heat more readily by resistive heating. Since microwave and resistive heating techniques depend on the microwave attenuation constant and electric resistivity, respectively, controlling the density of functional groups of ACFC can significantly affect the thermal regeneration of ACFC depending on the method used to heat the ACFC.     

Particle Cleaning of EUV Reticles

The practical adhesion, characterized by either ultimate parameters (F _max or d _max) or the critical strain energy release rate (G _Ic) using the three-point flexure test (ISO 14679-1997), and the residual stress (σ ) profiles within systems of organic layers made of DGEBA epoxy monomer and IPDA diamine hardener were determined. The prepolymer (DGEBA-IPDA) was deposited as thin and thick coatings onto degreased or chemically etched aluminum alloy (5754). To understand the role of the interphase, either a tri-layer (bulk coating/interphase/substrate) or a bi-layer model (bulk coating/substrate) were used for quantitative determination of the critical strain energy release rate. Indeed, as the interphase formation results from both dissolution and diffusion phenomena, we were able to control the interphase formation within coated systems by controlling the liquid-solid contact time and then to make tri- or bi-layered systems. In the three-point flexure test used to determine the practical adhesion, the failure may be regarded as a special case of crack propagation. The model considers residual stresses developed within the entire system leading to an intrinsic parameter representing the practical adhesion between the polymer and the metallic substrate. Moreover, to determine the profiles of residual stresses generated in such systems, the Young's modulus gradient of the interphase was also considered. The maxima in residual stress intensities were found at the interphase/substrate interface for a tri-layer system and at the coating/substrate interface for a bilayer system leading for all systems to an adhesional (interfacial) failure as experimentally observed. A comparison between the results obtained from the three-point flexure test and the Tapered Double Cantilever Beam (TDCB) was made. The determination of the critical strain energy release rate shows that residual stresses cannot be neglected. G _Ic depends on the substrate surface treatment when the residual stresses were neglected. Moreover, we have determined the role of the interphase formation on the practical adhesion before and after hydrothermal aging. The results obtained emphasize that the epoxy/metal interphase affects significantly the initial practical adhesion. However, organo-metallic complex formation improves considerably the hydrothermal durability, as these complexes act as corrosion inhibitors.     

Preparation and characterization of antistatic packaging for electronic components based on poly(lactic acid)/carbon black composites

Poly(lactic acid) (PLA) is a biodegradable aliphatic polymer obtained from renewable sources; its main application is in the packaging sector. Electronic components require the use of antistatic packaging that prevents damage and electric shock. As PLA has no conductive characteristics, it requires the addition of allotropic carbon forms such as conductive carbon black to make the polymer less resistive as the dissipative material and making it suitable for the manufacture of antistatic packaging. In this study, PLA was melt blended with 5, 10, and 15 wt % of carbon black. The composites were prepared using a high-speed mixer. Samples were characterized by Izod impact resistance tests, scanning electron microscopy, thermal properties, electrical characterization, and biodegradation tests in garden soil. The addition of carbon black in the PLA matrix increases the temperature of degradation and decreases the crystallinity degree and the impact resistance of the composites. However, carbon black is a great option to increase the electrical conductivity of PLA. The addition of carbon black in PLA makes the composite less resistive and suitable for use as antistatic packaging for the transportation and storage of electronic components. Furthermore, this composite does not cause damage to the environment as the carbon black does not interfere in the degradation mechanism of PLA. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47273.     

Effects of reactive reinforced interface on the morphology and tensile properties of amorphous polyamide–SAN blends

The effects of reactive reinforced interface on the morphology and tensile properties of amorphous polyamide (a-PA) and styrene-acrylonitrile (SAN) copolymer blend have been investigated using styrene maleic anhydride (SMA) copolymer as a reactive compatibilizer. The anhydride groups of SMA copolymer can react with the amine groups of polyamide and form in situ graft copolymers at the a-PA–SAN interfaces during the blend preparation. The interfacial adhesion strength of the reactive reinforced interface was evaluated quantitatively using an asymmetric double cantilever beam fracture test as a function of SMA copolymer content using a model adhesive joint. The interfacial adhesion strength was found to increase with the content of SMA copolymer and then level off. The morphological observations of a-PA–SAN (80/20 w/w) blends showed that the finer dispersion of the SAN domains with rather narrow distribution was obtained by the addition of SMA copolymer into the blends. The trend of morphology change was not in accord with that of the interfacial adhesion strength with respect to the content of SMA copolymer. However, the results of tensile properties showed very similar behavior to the case of the interfacial adhesion strength with respect to SMA content; that is, there was an optimum level of the reactive compatibilizer beyond which the interfacial adhesion strength and tensile strength did not change significantly. These results clearly reveal that tensile properties of polymer blend are highly dependent on the interfacial adhesion strength. Furthermore, it is suggested that the asymmetric double cantilever beam fracture test using a model interface is a useful method to quantify the adhesion strength between the phases in real polymer blends. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 68: 1925–1933, 1998