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The durability of adhesively bonded titanium structures is a topic of concern in a variety of fields today. There appears to be a definite connection between durability and surface pretreatment of the adherend. A variety of pretreatments are reported for Ti-6-41-3. For example, the chromic acid anodization (CAA) pretreatment has received a lot of attention in creating surfaces resulting in improved durability of adhesive bonds.

The surfaces of Ti and Ti (6% Al-4% V) powders were characterized by several techniques. BET surface areas as a function of temperature were measured using nitrogen adsorption. Heats of immersion (δwH) of these metal powders in water were measured after evacuation over the temperature range 100°-400°C. The δwH in water increased with increasing evacuation temperature and an anomalous increase was observed between 300° and 400°C. This was attributed to exposure of water to elemental titanium by cracking of the oxide layer at 400°C. XPS analysis did not support the possibility of metal migration through the oxide layer. Higher heats of immersion in water were determined for chemically pretreated compared to untreated Ti 6-4 powders. Water vapor adsorption isotherms were measured after evacuation of the metal powders at 100°C. Partial irreversibility of the water adsorption was observed on both powders. Water adsorption on Ti was temperature dependent. Heats of immersion measurements were used to study the interaction of primer solutions with these metal powders. Polyimide (LARC-13) and polyphenylquinoxaline (PPQ) interacted preferentially compared to the solvents with both powders. This polymer-metal interaction improved significantly after pretreatment of the Ti 6-4 powder by the Turco® 5578 and phosphate-fluoride processes. Again, an anomalous increase in the heat of immersion of Ti 6-4 evacuated at 400°C in the primer solution/solvents was observed. Anatase and rutile TiO2 powders are not satisfactory models for the surface oxide layer on either Ti or Ti 6-4 powders.

There are fewer papers on the adhesive bonding of steel for structural applications than for aluminum and titanium alloys. However, the approach to the adhesive bonding of all three adherends has been similar, that is, the surfaces are pretreated prior to bonding. Trawinski, et al.1,2,3 reviewed several conversion coatings or etching processes used for steel. Haak and Smith4 selected two surface treatments among nineteen based on minimal cost, simplicity and good durability. Smith5 has reported work on stainless steel-epoxy bonds under hydrothermal stress. Bischof, et al.6 investigated the effect of surface pretreatment of steel on bonding strength obtained with polyvinyl chloride. Ziane, et al.7 identified four fracture zones resulting from shear loading of epoxy bonded galvanized steel following four different surface pretreatments. But in some cases, as in the automotive industry, there is a need to bond oily steel directly without surface pretreatment. Rosty, et al.8 have reported a study of the role of fillers and cure temperature on the shear strength of oily steel bonded with epoxy. None of the reported research utilizes both microscopic and spectroscopic techniques to analyze the fracture surfaces.

(1)Energy budgets are based upon the equation: C=P+R+FU, where C=consumption, P=production, R=respiration and FU=egesta. In studies of insect energetics, where all four parameters have been measured, the completed budget rarely balances. This can often be traced to inaccuracy in the R term which, when measured with a respirometer (Rm), is almost invariably less than when calculated as C-P-FU(=Rc).(2)The Rc·RmEmphasis>/-1values of ‘wild’ insects (av. 2.58) are consistently larger than those of ‘laboratory’ insects (av. 1.25).(3)Suggestions that incorrect oxycalorific equivalents, caused by inappropriate RQ values, result in large inaccuracies in Rmare shown to be invalid.(4)The possibility that the C term in the energy budgets of phytophagous insects has been miscalculated because of a failure to account for leaf respiration is discounted because it is equally possible, at least in properly conducted experiments, for leaves to gain weight by photosynthesis. Furthermore, this factor cannot account for imbalances in the budgets of nonphytophages.(5)The gut contents of phytophagous insects can weigh as much as the gut-free body. Failures to account for this factor lead to over-estimates of P.(6)It is concluded that there is little reason to doubt evidence published elsewhere that ‘flask-effects’ are the major cause of the discrepancy between Rmand Rc.

Termites are important agricultural pests in the semi-arid tropics. Conventional methods of control have relied on persistent organochloride insecticides with accompanying health and environmental problems. In contrast, cultural control methods provide untested, but environmentally sound options to farmers. This study reports results from three experiments on the use of mulches to reduce Microtermes obesiand Odontotermesspp. damage with relevance to groundnut production in India. Termites scarification of groundnut was 80–90% lower for pods dried in neem cake or Ipomoea fistulosamulches than for pods dried directly on the soil. Similarly, subterranean attack by termites on bamboo baits was 20–40% lower in mulched plots than in controls. However, mulches were ineffective in protecting bullock manure from removal by termites. Successful use of mulches in termite control may be related to food source concentration. Termite location of concentrated food sources, such as bullock manure, was followed by recruitment of workers and construction of protected runways. In contrast, termites foraging on limited food sources, such as groundnut pods, did not construct runways and had greater exposure to mulches. Dans les zones tropicales semi-arides, les termites sont des ravageurs importants des cultures. Les méthodes de lutte traditionnelles sont fondées sur l’utilisation répétée d’insecticides organochlorés nuisibles pour la santé et l’environnement. En revanche, les méthodes de lutte culturales non encore expérimentées, constituent une solution écologiquement saine pour les agriculteurs. Ce document rapporte les résultats de trois expériences portant sur l’utilisation de paillis pour réduire l’ampleur des dégâts occasionnés par Microtermes obesiet Odontotermesspp. dans le cadre de la production d’arachide en Inde. Le taux de scarification de l’arachide par les termites était de 80-90% inférieur pour les gousses séchées dans des tourteaux de neem ou des paillis de Ipomoea fistulosapar rapport aux gousses séchées à même le sol. De même, les attaques souterraines de termites sur les appâts en bambou étaient inférieures de 20 à 40% dans les parcelles recouvertes de paillis par rapport aux parcelles témoins. Toutefois, le paillis s’est révélé inefficace pour éviter que le fumier de boeufs ne soit emporté par les termites. L’efficacité de l’utilisation de paillis pour lutter contre les termites peut s’expliquer par la concentration de la source d’alimentation. En effet, le repérage par les termites de sources d’alimentation concentrées, telles que le fumier, donnait lieur au recrutement d’ouvrières et à la construction de voies de passage protégées. En revanche, les termites n’ayant trouvé que des sources alimentaires limitées, telles que les gousses d’arachide, ne construisaient par de voies de passage et se trouvaient de cè fait beaucoup plus exposés aux paillis.

The effects of intercropping groundnut with sunnhemp on termite incidence and damage were studied in the rainy and post-rainy season at ICRISAT Center in central India. Termite incidence in different cropping systems was determined by baiting with bamboo stakes. Damage to groundnut plants and pods was evaluated at harvest. Intercropping groundnut with sunnhemp did not affect termite abundance or damage to groundnut. These results contrast with a Colombian intercropping study in which sunnhemp exudates repelled cassava burrowing bugs. Termite biology, including recruitment of foragers and construction of protected runways, may have reduced exposure to sunnhemp, thereby minimizing effects. Au centre de l’ICRISAT en Inde centrale, une étude a été effectuée au moment de la saison des pluies et de l’après-saison des pluies sur les effets de l’association culturale arachide/Crotolaria junciasur l’incidence et les dégâts des termites. L’évaluation de l’incidence des termites dans les différents systèmes culturaux a été effectuée à l’aide de piquets de bambou servant d’appâts. L’estimation des dégâts occasionnés sur les plants et les graines d’arachide a été menée au moment de la récolte. L’association culturale arachide/Crotolaria juncian’a eu aucun effet sur l’abondance des termites et leurs dégâts sur l’arachide. Ces résultats sont en contradiction avec une étude colombienne portant sur l’association culturale dans le cadre de laquelle on a constaté que les éxudats de Crotolaria junciarepoussaient les punaises foreuses du manioc. Il est possible que la biologie des termites comprenant notamment le recrutement d’ouvrières et la construction de voies de passage protégées ait limité leur exposition à Crotolaria juncia, minimisant ainsi son effet repoussant.

The objectives of this work were to characterize the surface of commercial carbon fibers, focusing on the effect of polymer sizing and the effect of oxygen radiofrequency plasma treatment. The fiber surface composition was determined by x‐ray photoelectron spectroscopy (XPS) and the surface topography was examined by scanning transmission electron microscopy (STEM) and atomic force microscopy (AFM).

Published information was used to compile a summary of natural enemies (parasitoids, predators and diseases) reported attacking Spodoptera litura(F) under field conditions. Species (71) of insect parasitoids in seven families of Hymenoptera and two families of Diptera were listed as parasitoids of different stages of S. litura. Predatory insects (36) belonging to 14 families and 12 species of spiders from six families have been reported to feed on this species. Four protozoan, four fungal, seven bacterial, four each of viral and nematode species were also reported to be the pathogens of this species. Published information suggested that periodic releases of large number of egg parasites could help in suppressing populations of this pest. There is a considerable scope for increased attention to the role of natural enemies as component of integrated pest management programmes of S. litura. Compte rendu mondial des ennemis naturels et des maladies de Spodoptera litura(F.) (Lépidoptères: Noctuides): Des informations publiées ont servi de source pour la compilation de ce compte rendu des ennemis naturels (parasites et prédateurs) et des maladies qui s’attaquent à Spodoptera litura(F.) en milieu réel. Soixante-neuf espèces d’insectes parasitoïd parmi sept familles des Hyménoptères ainsi que de familles des Diptères sont classées comme parasites des différents stadesde S. litura. Trente-six insectes prédateurs, appartenant à 14 familles et 12 espècesd’araingnées provenant de six familles se nourriraient de cette espèce. Quatre protozoares, quatre moisissures, sept bactéries, quatre virus et cinq nematodes seraient également des agents pathogènes de cette espèce. Les information publiées laissant à croire que des introductions périodiques des parasites des oeufs en grands nombres permettraient de supprimer la population de Spodoptera. Les ennemis naturels offrent des possiblités importantes pour jouer un rôle clé dans des programmes de lutte intégrée contre S. litura.

The effects of surface preparation and sterilization treatments of cpTi on in vitro osteoblast cell attachment were investigated. Surface characterization by XPS and AES and determination of wetting angles indicated that sterilization by exposure to ultraviolet light or gamma irradiation resulted in highly energetic, relatively contaminant-free cpTi surfaces which supported high levels of osteoblast cell attachment. Steam autoclaving, however, resulted in relatively low energy surfaces with high levels of O-C-and N-containing contaminants. Other inorganic contaminants were also detected on the surface of selected samples. As a result, steam-autoclaved surfaces supported significantly lower levels of cell attachment. At 2 hours after initial attachment, the osteoblast cells failed to spread and integrate onto the surfaces sterilized by steam autoclaving. These results confirm previous studies regarding the contamination resulting from steam autoclaving and indicate that non-contaminating sterilization procedures should be employed for the sterilization of commercial metallic implant materials.

X-ray photoelectron spectroscopy (XPS) was used to examine the interfacial chemistry in polyphenylene sulfide (PPS)/copper bonded laminates. Several surface pretreatments were studied including a simple methanol wash, two acid etches, thermal oxidation and chemical oxidation. Peel test analysis showed poor adhesion to the methanol-washed and acid-etched foils, giving a peel strength of only 3-5 g/mm. XPS analysis of the failure surfaces revealed a large amount of inorganic sulfide at the interface with reduction of the copper oxide. Chemical oxidation using an alkaline potassium persulfate solution gave a matt-black surface consisting of primarily cupric oxide. These samples showed improved adhesion and XPS analysis of the failure surfaces revealed fracture through a mixed PPS/cuprous oxide layer. A simple thermal oxidation yielded a cuprous oxide surface layer and laminates bonded to these surfaces showed a more than ten-fold increase in peel strength. XPS analysis of the failure surfaces showed much lower amounts of interfacial copper sulfide and it was postulated that excess sulfide at the interface was responsible for the poor adhesion observed for other pretreatments.

Electron microprobe analysis (EMP) was used to study interdiffusion in bilayer films of thermoplastic poly(vinylpyrrolidone) (PVP) and a thermoset epoxy. The bilayer films were prepared by casting a stoichiometric mixture of the uncured diglycidyl ether of bisphenol A epoxy (DGEBA) and 4,4'-diaminodiphenylsulfone (DDS) on the PVP film and then curing the system in a two-step process under a nitrogen atmosphere. For the EMP studies, the sulfur signal was used as a probe for DDS, while the nitrogen signal served as a probe for both DDS and PVP. The addition of brominated DGEBA to the conventional DGEBA in a 1: 1 weight ratio allowed the bromine signal to be used as a probe for the epoxy phase. It was found that the interfacial thickness was much larger for the film prepared from low molecular weight PVP than that from high molecular weight PVP. Interdiffusion was suppressed when the initial cure temperature in the two-step cure cycle was 130°C compared to 170°C, in which the first stage of the cure reaction dominated the interdiffusion process. More importantly, it was demonstrated that the diffusion front of the curing agent was located closer to the thermoplastic polymer phase as compared to that of the thermoset polymer in the interface region. This tendency was more significant in the system with the larger interfacial thickness. These results have important consequences on interphase structures and properties. They suggest that crosslinking of the epoxy in the interphase may be suppressed because of an insufficient amount of curing agent and that the not-fully-reacted curing agent in the PVP phase may act to plasticize this phase. © 1997 John Wiley & Sons, Inc.

The passive film at a stainless steel surface which consists mainly of chromium and iron oxides, has a surface energy that can be strongly reduced by the adsorption of organic contamination. We have investigated the effect of surface pretreatments of stainless steel on the long-range surface forces and the adhesion forces. Electron spectroscopy for chemical analysis (ESCA) has been used to analyze the chemical composition of the surface film and to estimate the thickness of the organic contamination layer. An atomic force microscope has been used to measure the long-range hydrophobic attraction forces and the adhesion force between the stainless steel surface and a silanated silica sphere immersed in water. The adhesion forces on both the contaminated hydrophobic and cleaned hydrophilic surfaces have been correlated with the interfacial energies obtained by contact angle measurements. Both long-range attractive and adhesive forces are stronger for the noncleaned surface possibly due to the "hydrophobic effect." This hydrophobic interaction becomes neutralized in the presence of hydrophilic groups (i.e., potassium salt) on the surface. On the other hand, contact angle measurements indicate a higher surface energy for the Ar-plasma-treated surface than for the contaminated sample. This shows that these forces are not only dependent on the surface properties but are also markedly dependent on the nature of the surrounding medium, which can drastically alter the interactions between two macroscopic bodies. Copyright 1995, 1999 Academic Press

The impact of larval defoliation by Aproaerema modicella(Deventer) on the growth, development and yield of two groundnut cultivars (Kadiri 3 and NC Ac 17090) was studied under a naturally occurring, high density infestation. Defoliation by leaf-mining larvae did not increase plant mortality in either cultivar. In both cultivars, leaf and stem production were significantly lower in untreated plots than in the treated plots. Unsprayed plants of both cultivars produced fewer flowers, pegs, and pods per plant compared to plants of the same cultivar protected with monocrotophos. Fruit growth rates, however, were marginally higher in control plots than in treated plots. Pod yields were 35 and 44% lower, and haulm yields 25 and 20% lower, in Kadiri 3 and NC Ac 17090, respectively in untreated control plots compared to plots treated with insecticide. A linear relationship between leafminer density and pod and haulm yields was observed, and differences between cultivars were not significant. Cette étude a porté sur l’impact de la défoliation par les larves de Aproaerema modicella(Deventer) sur la croissance, le développement et le rendement de deux cultivars d’arachide (Kadiri 3 et NC Ac 17090) dans des conditions d’infestation naturelle à densité élevée. La défoliation n’a augmenté la mortalité de plantes ni chez l’un ou l’autre de ces cultivars. Pour les deux cultivars, la production de feuilles et de tiges était sensiblement réduite dans des parcelles non-traitées par rapport aux parcelles traitées. Des plantes non-pulvérisées des deux cultivars ont produit moins de fleurs, de gynophores et de gousses par plante, par rapport aux plantes du même cultivar traitées au monocrotophos. Cependant, les taux de croissance des fruits étaient légèrement plus élevés dans des parcelles témoins que dans des parcelles traitées. Les rendements en gousses étaient de 35 et 44% moins élevés, les rendements en fanes, de 25 et 20% moins élevés, chez Kadiri 3 et NC Ac 17090 respectivement dans des parcelles témoins non-traitées par rapport au traitement insecticide. Un rapport linéaire a été constaté entre la densité d’infestation de la mineuse des feuilles et les rendements en gousses et en fanes, les différences entre cultivars n’étant pas significatives.

The Integrated Pest Management (IPM) Programme under development at the International Crops Research Institute for the Semi-Arid Tropics (ICRISAT) calls for a proper monitoring system. Experiments conducted in groundnut fields at ICRISAT Center near Hyderabad, in peninsular India, to establish the optimum height for pheromone traps to monitor Spodoptera lituta(F), indicated that the male flight pattern changes considerably during the cropping period. During the seedling stage (sowing to 6 weeks), most moths were caught at 0.5 and 1.0 m. In the initial growth phase (7-11 weeks), the traps at 4.0 m caught most moths. During the optimum growth phase (12th week to harvest) of the crop the traps at 1.0 m height trapped most moths. After harvest, the traps at 4.0 m again recorded the highest catch. These data are interpreted in terms of the migration pattern of S. lituramoths during the crop season. We suggest monitoring this species, using 1 m height traps. Males were found to be more active around 0300 hr, with a small peak after sunset (2000 hr). Irrespective of season, the peak flight activity of this species was around 0300 hr in groundnut fields. Le programme de lutte intégrée développé à l’International Crops Research Institute for the Semi-Arid Tropics (ICRISAT) passe par la mise en place d’un système de surveillance efficace. Des expériences ont été menées dans des parcelles d’arachide au Center ICRISAT près d’Hyderabad (Inde) pour déterminer la hauteur optimum des pièges à phéromones utilisés pour surveiller les populations de Spodoptera lituraF. Les résultats montrent que l’activité de vol des mâles varie pendant la période de croissance de l’arachide. Au stade plantule (semis à 6 semaines) la plupart des mâles sont capturés dans des pièges placés entre 0,5 et 1,0 de hauteur. Pendant la phase de croissance initiale (7-11 semaines) les pièges placés à 4,0 m, capturent plus de mâles. Après la récolte, les pièges placés à 4,0 m de hauteur capturent à nouveau le plus grand nombre de mâles. Ces résultats sont iterprétés en fonction de l’activité de vol de S. liturapendant la période de culture. Les pièges à phéromone placés à 1,0 m de hauteur nous semblent les plus efficaces pour évaluer le niveau d’abondance des populations de ce ravageur. Les mâles sont plus actifs vers 0300 hr et, dans une moindre mesure, au crépuscule (2000 hr). Le pic d’activité de vol de ce ravageur se situe donc autour de 0300 hr dans les champs d’arachide, indépendemment de la saison.

First results on π−d → are reported. The measurements were made using 8 specially designed neutron counters, which were carefully calibratedin situ. The differential cross sections atTπ=142, 180, 217, and 254 MeV were obtained at four angles between 0° and 90°, they are compared to π+d →pp data measured at the same energies and angles with the same setup. At every beam energy, the shape of the angular distributions of π−d →nn and π+d →pp is the same to ±2%. The absolute cross sections differ by 1 to 10%. The error in this comparison is ±4% implying a small violation of charge symmetry.

Quantitative XPS has been used to determine the surface concentration of hydroxyl groups in native air‐formed oxide films on metals having low surface areas. A mathematical expression has been derived to give the concentration of surface hydroxyl groups as a function of the intensity ratio of the OH to O2−contributions to the O 1s photopeak. This expression is based on modeling the oxide film on a metal to be a multilayer system consisting of an outermost layer of organic contamination, a layer of chemisorbed water, a surface hydroxylated region of the oxide film and the inner portion of the oxide film. The average values of the experimentally determined concentrations of surface hydroxyl groups are 15, 13, 11, 6 and 8 OH nm−2for oxide‐covered aluminum, chromium, titanium, tantalum and silicon, respectively. X‐ray photoelectron spectroscopy depth profiles using argon ion sputtering and variable‐angle XPS have been utilized in this work. Surface treatments have employed either ultrasonic cleaning with organic solvents or argon plasma treatment. © 1998 John Wiley & Sons, Ltd.

Abstract: Natural enemies of the groundnut leaf miner,Aproaerema modicella (Deventer), were studied at the International Crops Research Institute for the Semi-Arid Tropics (ICRISAT) located near Hyderabad in peninsular India. Hymenopterous parasitoids attacking leaf miner larvae were the most important group of natural enemies. Nine primary and eight secondary parasitoids emerged from host larvae, and killed up to 50% of the leaf miner larvae sampled. The trophic relationships between primary and secondary parasitoids are incompletely understood. The influence of pathogens of this species is reported for the first time. These pathogens killed up to 30% of the leaf miner larvae. The combined effects of all mortality agents killed up to 95% of the leaf miner larvae per sample period. However, use of insecticides in sprayed plots reduced the efficacy of parasitoids. The impact of predators on larval populations was not studied and may explain underestimates of leaf miner mortality rates.

Incorporation of aesthetic considerations in the process of landscape planning and development has frequently met with poor results due to its lack of theoretical basis, public involvement, and failure to deal with spatial implications. This problem has been especially evident when dealing with large areas, for example, the Adirondacks, Scenic Highways, and National Forests and Parks. This study made use of public participation to evaluate scenic quality in a portion of the Niagara Escarpment in Southern Ontario, Canada. The results of this study were analyzed using thevisual management model proposed by Brown and Itami (1982) as a means of assessing and evaluating scenic quality. Themap analysis package formulated by Tomlin (1980) was then applied to this assessment for the purpose of spatial mapping of visual impact. The results of this study illustrate that it is possible to assess visual quality for landscape/management, preservation, and protection using a theoretical basis, public participation, and a systematic spatial mapping process.

Aluminum-polymer bonds in hot-moist environments are subject to degradation due to moisture intrusion into the bonded joint and the resulting conversion of the surface oxide to the hydroxide. In order to analyze moisture intrusion, work has been done on diffusion and/or solubility characteristics of humid air or water in polymer materials. These investigations have been concerned with the actual solution and transport behavior of water in resins, especially the influence of morphology, temperature, or concentration, which affects the moisture absorption and desorption of homogeneous materials. However, such testing cannot give information on the effect of water at the substrate/adhesive interface but it can be used to screen water-sensitive adhesives.

An investigation of polysulfone-Al/Li alloy interaction involved single lap shear joints and wedge samples following an FPL etch, sulfuric acid anodization (SAA) and phosphoric acid anodization (PAA). The study of the Al/Li surfaces involved the determination of the elemental composition and morphological features of the pretreated adherend before bonding and following fracture. When polysulfone was either thermally pressed or primed onto the microporous surface, the polysulfone indeed penetrated into the porous oxide and thereby provided a mechanical means of adhesion. The wedge test results for the adherend pretreated by PAA and SAA were superior to those for the FPL etched adherend. The failure path for the FPL etched samples was at the adhesive/oxide interface whereas the failure path for the PAA samples was within the adhesive but with occasional divergence of the crack into the oxide. The porous oxides on Al/Li alloy formed after PAA and SAA treatment were shown to undergo dramatic changes in morphology on short term (< 95 hrs) exposure to 71°C and 100% R.H. environment. The mechanism of failure was due to moisture which caused hydration and subsequent weakening of the surface oxide layer and the bonded joint. Lithium was not surface concentrated in the PAA treated Al/Li alloy as shown by AES depth profiling and therefore the effect of Li on the durability of the bonded alloy is considered minimal.

The efficacy of four pheromone-trap designs was compared for catching male tobacco caterpillar, Spodoptera litura (F), moths in groundnut fields. There was no significant difference in the performance of the single- and double-funnel traps, and the single-funnel (20 cm dia) trap captured more moths than any other trap. Septa of 4 weeks or less exposure attracted most moths. One and two traps ha-1 caught significantly fewer moths than four and more traps ha-1 however there was no significant improvement in capture when four or more traps ha-1 were installed. Night observations indicated that many moths escaped from sleeve traps. Single plastic funnel traps were found suitable and are being used in monitoring S. litura in the national monitoring network in India.

White grubs, termites, millipedes, wireworms and earwigs bore holes in developing groundnut (Arachis hypogaea L.) pods throughout the semi-arid tropics. White grubs and termites also damage the roots. The above-ground pests include Spodoptera litura Fab. and the groundnut leaf miner Aproaerema modicella Deventer in Asia. Aphids transmit a number of virus diseases. A thrips Frankliniella schultzei (Trybom) is the vector of bud necrosis disease, which is a serious problem in Asia, southern USA and Australia. Jassids can cause much foliar damage, but their pest status is not certain, except as virus vectors. The pest control options lead away from insecticides, which are often available and are too expensive, towards exploiting host plant resistance and natural control and employing management techniques that restrict pest activity.

IM7 carbon fibers were surface treated in methane, ethylene, trifluoromethane and tetrafluoromethane plasmas. The surface chemical composition of the fibers was determined by X-ray photoelectron spectroscopy (XPS). The adhesion between as-received and plasma-treated carbon fibers and polyethersulfone (PES) and an epoxy resin was measured by the microbond pull-out test. XPS showed that the methane and ethylene plasmas deposited a thin layer of hydrocarbon on the fiber surface. The trifluoromethane plasma deposited a layer of fluorocarbon on the surface of the fibers. The tetrafluoromethane plasma etched the fibers and introduced a significant amount of fluorine on the surface. The microbond pull-out test results indicated that an etching plasma, such as the tetrafluoromethane plasma, improved the adhesion between carbon fibers and PES. These results are consistent with earlier work performed with ammonia plasma. The adhesion is believed to be due primarily to the differential thermal shrinkage between the fiber and the matrix. It was shown that in the case of a reactive matrix such as an epoxy resin, the fiber chemical composition plays a role in the fiber-matrix adhesion. However, this chemical effect is secondary to the cleaning effect of the surface treatment.

The relationship between interphase microstructure produced from fiber surface chemistry and the resulting composite structural properties is not well understood. This relationship is, however, key to predicting composite performance and to the understanding of how to assemble the constituents properly for best use of the unique properties of the fibers. In this study, a significant difference in laminate compressive performance is observed for both static and dynamic loading. Two different fiber sizings, an unreacted bisphenol-A-based epoxy and the thermoplastic, polyvinylpyrrolidone (PVP), are identified as the source of these observations. The fiber, matrix and processing remained the same in both systems. However, morphological differences in the interphase region were observed. The resulting mechanical properties indicated that the PVP sizing improved static compressive strength by 51% and increased the fatigue life of notched cross ply laminates (cycled at R=-1) by at least two orders of magnitude over the bisphenol-A-sized composites. The mechanism by which PVP brought about these changes is unclear and requires further study. However, these results also indicate that the selection of interphase characteristics requires additional information about the fiber-matrix bond than merely strength.

The bonding of cold rolled steel with polysulfone, a thermoplastic adhesive has been studied. The single lap shear strength of bonded samples where the substrate was gritblasted was 40% lower than for the case where the substrate was hydrothermally oxidized. Both surface preparations resulted in diminished lap shear strength on exposure to high humidity conditions. However, the hydrothermally oxidized substrates resulted in more durable bonds.

Factors influencing the durability of Ti-6Al-4V/metal alkoxide/epoxy interphases were determined by studying the chemical composition of three metal alkoxides and evaluating the bond durability of Ti-6Al-4V/epoxy bonds primed with these materials. The three alkoxides were sec-butyl aluminum alkoxide, tetra-isopropyl titanate and tetra-n-butyl titanate.Because adhesive bonds made using phosphate fluoride (P/F) pretreated Ti - 6Al - 4V substrates were not durable, P/F treated Ti - 6Al - 4V was chosen as the substrate for testing the possible durability enhancement by the titanium and aluminum alkoxide coatings. Sec-butyl aluminum alkoxide significantly enhanced the bond durability of the P/F pretreated bonds, while the titanium alkoxide primers showed no improvement in durability. The locus of failure and infrared studies indicated the enhancement in durability by the aluminum alkoxide was due to the high concentration of hydroxyl groups on the alkoxide surface available to interact with the epoxy adhesive.

Factors influencing the durability of Ti-6Al-4V/epoxy interphases were studied by determining chemical and physical properties of Ti-6Al-4V adherend surfaces and by characterizing the strength and durability of Ti-6Al-4V/epoxy bonds.Ti-6Al-4V adherend surfaces were oxidized either by chemical etch or anodization. Four principal pretreatments were studied: chromic acid anodization (CAA), sodium hydroxide anodization (SHA), phosphate fluoride acid etch (P/F) and TURCO basic etch (TURCO). The oxides were characterized by SEM, STEM, profilometry, contact angles and XPS.All adhesive bonding was carried out using a structural epoxy, FM-300U. Both lap shear and wedge test samples were tested in hot, wet environments. The results lead to the conclusion that the interfacial area between the adhesive and adherend is the primary factor affecting bond durability.

The surface chemistry of IM7 carbon fibers was characterized by x-ray photoelectron spectroscopy (XPS). The fiber surface energetics were determined from a two-liquid tensiometric method. The adhesion between as-received and plasma-treated carbon fibers and polyethersulfone (PES) was measured by the microbond pull-out test.The surface characterization techniques showed that the effect of any plasma treatment is attained within less than 15 seconds. It was found that both argon and air plasmas increased the oxidation state of the fiber surface and that they reduced the dispersive component (γsd) of the fiber surface free energy considerably. The ammonia plasma treatment resulted in a cleaning of the surface. This plasma treatment was also effective in improving the fiber/matrix adhesion of quenched samples. A similar adhesion enhancement between as-received fibers and PES is obtained by annealing the samples above the Tg of the polymer. The air plasma treatment did not have any significant effect on the fiber/matrix adhesion.

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.

LaRC-TPI, an aromatic thermoplastic polyimide, was exposed to oxygen, argon and ammonia plasmas as pretreatments for adhesive bonding. A 180d`peel test with an acrylate-based pressure sensitive adhesive tape as an adherend was utilized to study the interactions of the plasma-treated polyimide surface with another polymeric material. The peel strengths of the pressure sensitive adhesive tape on the plasma-treated LaRC-TPI fell below the level of the non-treated controls, regardless of the plasma treatment used. Failure surface analysis by XPS revealed the presence of polyimide on the pressure sensitive adhesive failure surface, indicating failure in the plane of a weak boundary layer created by plasma treatment. The removal of the weak boundary layer by a solvent rinse restored the peel strength to the level of the control. Comparison with tape adhesion peel strengths of oxygen plasma-treated high density polyethylene showed that the physical condition of a polymer surface following plasma treatment plays an important role in determining the level of adhesion which can be achieved.

LaRC-TPI, an aromatic thermoplastic polyimide, was exposed to oxygen, argon and ammonia plasmas as pretreatments for adhesive bonding. Chemical changes which occurred in the surface as a result of the plasma treatments were investigated using x-ray photoelectron spectroscopy (XPS) and infrared reflection-absorption spectroscopy (IR-RAS). Water contact angle analysis was utilized to characterize the changes in surface wettability, and the ablative effects of the plasmas were monitored using ellipsometry. Both XPS and IR-RAS results indicated the formation of polar functional groups at the surface. Contact angle analysis showed enhanced water wettability of the plasma-treated surface. Oxygen and argon plasmas were highly ablative, whereas ammonia plasma was only moderately so. Oxygen and argon plasmas appear to react with the LaRC-TPI via a fragmentation/oxidation mechanism; the effect of ammonia plasma is postulated to be imide ring-opening resulting in the formation of amide functional groups.

Thin polysulfone (PSF) coatings on pretreated aluminum surfaces were characterized utilizing dielectric thermal analysis (DETA) to detect changes in the molecular motions and structural transitions in the PSF-Al interphase. The XPS results show that the interfacial chemistry between the PSF and the Al oxide surface was the same on both degreased and phosphoric acid anodized (PAA) Al surfaces. The order of the loss peak temperature of the PSF is, PSF coating on porous Al>PSF coating on smooth Al>neat PSF film. The activation energy of relaxation is also lower for neat PSF when compared with the thin film cast onto a smooth Al or a porous PAA Al substrate. The SEM photomicrographs revealed that the PSF uniformly coated the degreased substrate, whereas PSF filled the porous oxide on PAA Al surface and resulted in whisker-like structures.

Chromic acid (CA) anodization of Ti-6A1-4V (6% Al, 4% V by weight) produced an anodic oxide on the alloy surface. The influence of specific CA anodization conditions upon anodic oxide thickness was determined. Each CA anodization condition tested was defined by setting five variables: (1) solution composition; (2) anodization time; (3) solution temperature; (4) initial current density; and, (5) anodization potential.The results confirmed observations by previous workers about oxide thickness and structure. Data indicated an inverse relationship between film thickness and temperature, and that film growth rate decreases with time.

Unidirectional carbon fiber/LaRC TPI composites were prepared by aqueous suspension prepregging. The matrix material was fully imidized LaRC TPI powder, and the binder was LaRC TPI polyamic acid. The effect of the concentration of the polyamic acid binder on composite processability and properties was studied. An optimum concentration range of 2.9-9.4% weight/weight binder/matrix was found that resulted in good prepreg handling characteristics and good consolidation. A binder concentration 2 13.1% led to poorer consolidation of the composites due to an increase in the melt viscosity of the matrix. This increase was probably due to a combination of crosslinking and chain extension of the polyamic acid during the imidization step. Formation of the crosslinked structure was supported by transverse flexure, meso-indentation, and solubility tests.

Arylene ether phosphine oxide homopolymers were prepared via nucleophilic aromatic substitution polycondensations of bis(4-ftuorophenyl)phenyl (or methyl) phosphine oxide with various aromatic bisphenols in the presence of a weak base and an aprotic dipolar solvent. These thermoplastic materials with Tg values in the range of about 200°C-285°C showed 5% weight loss in air around 500°C with substantial amounts of char yield at 800°C, which was related to their excellent' self-extinguishing characteristics relative to other engineering thermoplastics. Additionally, the presence of phosphorus in the char after such high temperature heating implied that these materials should also be resistant to aggressive oxygen plasma environments. Indeed, these systems showed extremely low amounts of etching in oxygen plasma when compared with other engineering polymers. The presence of phosphorus residues after either burning or etching with oxygen plasma could play crucial roles in areas of commercial importance and aerospace applications.

The hemodynamic effects of i.a. [met]enkephalin were studied in the hindquarter vasculature of chronically prepared, conscious rabbits. A new method allowed i.a. injection while simultaneously measuring blood pressure and blood flow to this vascular bed. [Met]enkephalin produced a dose-dependent (3-300 micrograms/kg) decrease in hindquarter vascular resistance (18-42% change from base line). The duration of the response ranged from 28 sec to over 2 min. Heart rate decreased 16 to 45% over the same dose range but returned to preinjection levels in 5 sec. Only the bradycardia was abolished by pretreatment with atropine methyl nitrate. All hemodynamic changes were eliminated or significantly reduced after pretreatment with the ganglionic blocking agent, chlorisondamine hydrochloride. The opioid antagonist, naloxone hydrochloride, abolished the hemodynamic effects of [met]enkephalin. Resistance decreases in the mesenteric vasculature were coincident with those in the hindquarters. The time to onset of the response was delayed when [met]enkephalin was injected i.v. These data indicate activation of a reflex originating in the hindquarters that resulted in opioid-dependent increased efferent parasympathetic activity to the heart and decreased sympathetic tone to at least two vascular beds.

We appreciate the interest of Clearfield and Davis in our work on Ti-6A1-4V adherends pretreated using sodium hydroxide anodization. The authors call attention to two main points, namely, the value of the O/Ti atomic percent ratio as determined by X-ray photoelectron spectroscopy (XPS) and the relative thickness of the oxide layers as determined by depth profiling with Auger electron spectroscopy (AES).