Effect of Surface Energetics of Substrates on Adhesion Characteristics of Poly (p-xylylenes)

In investigating the effect of the surface energetics of substrate materials on the adhesion characteristics of poly(p-xylylene) and poly(chloro-p-xylylene) by the “Scotch Tape” method, it was found that if the substrates had not been preconditioned (treated with argon or a methane plasma), the adhesion was poor. The characteristics of water resistant adhesion that were observed when coated substrates were boiled in 0.9% sodium chloride solution were found to vary from excellent (when the polymer did not peel from the substrate after three cycles of 8 hours of boiling and 16 hours at room temperature) to poor (when the polymer peeled off almost immediately). It was noticed that water resistant adhesion depends on the hydrophobicity of the substrate material (the greater the hydrophobicity, the greater the adhesion) and is not related to the dry adhesive strength of poly(p-xylylene). The oxygen glow discharge treatment of the substrates decreased both the dry and wet adhesive strength of the polymer. The effect of the argon glow discharge treatment depended on the surface energetics of the substrate, and the methane glow discharge treatment increased both the dry and wet adhesive strength of the polymer. These preconditioning processes are discussed in terms of the sputtering of the material from the wall of the reactor in contact with the plasma and the deposition of the plasma polymer of the sputtered material on the substrate surface.     

Surface Energetics and Adhesion

The relationships between surface energetics and adhesion are critically reviewed. New data that confirm such relationships, for peel tests as well as lap shear tests, are presented. The effect of hydrothermal aging of aluminum surfaces on surface energetics can be used to predict degradation in bond strength. The mechanism of failure for elastic adhesives (such as Scotch ® tape) in peel tests may be essentially the same as for more brittle adhesives (such as epoxies) in lap shear tests. This mechanism may involve brittle fracture that forms a critical flaw at the adherend-adhesive interface (on a microscopic level), followed by crack propagation which then may include considerable elastic and plastic deformation. The locus of propagation (fractography) is generally not (but may be) relevant to the problem of how to remedy mechanical weakness in an adhesive joint, since the local region of critical flaw formation rather than the general surface area determines the joint strength.     

Adhesion Improvement of Poly(Phenylene-Vinylene) Substrates Induced by Argon-Oxygen Plasma Treatment

Copper films evaporated on argon-oxygen plasma-treated poly(phenylene-vinylene) films have been studied by scratch test, X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). The adhesion of the metallic film to the polymer substrate was greatly enhanced after treatment and found to increase with the treatment time. SEM observation of the treated samples revealed that the morphology of the polymer surface was gradually changed with the treatment time as compared with that of the bare polymer film. On the other hand, XPS analysis of the polymer-metal interface showed that the bonding between carbon, oxygen and copper were subsequently modified as compared with those obtained in untreated samples. The high adhesion strength observed on these substrates was related to the modification in the surface morphology on the one hand and to the formation of new compounds at the polymer-metal interface on the other. The nature of the interfacial layer and its influence on the adhesion of the copper layer was discussed by comparing the results with those obtained in poly(phenylene-vinylene) (PPV)-Al systems.     

Adhesion Improvement of Poly(Phenylene-Vinylene) Substrates Induced by Argon-Oxygen Plasma Treatment

Copper films evaporated on argon-oxygen plasma-treated poly(phenylene-vinylene) films have been studied by scratch test, X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). The adhesion of the metallic film to the polymer substrate was greatly enhanced after treatment and found to increase with the treatment time. SEM observation of the treated samples revealed that the morphology of the polymer surface was gradually changed with the treatment time as compared with that of the bare polymer film. On the other hand, XPS analysis of the polymer-metal interface showed that the bonding between carbon, oxygen and copper were subsequently modified as compared with those obtained in untreated samples. The high adhesion strength observed on these substrates was related to the modification in the surface morphology on the one hand and to the formation of new compounds at the polymer-metal interface on the other. The nature of the interfacial layer and its influence on the adhesion of the copper layer was discussed by comparing the results with those obtained in poly(phenylene-vinylene) (PPV)-Al systems.     

Water Resistance of Poly(imide-siloxane) Adhesives: An IGC Surface Energetics Study

Inverse Gas Chromatography was utilized to examine the interaction of water vapor with the surfaces of a polyimide homopolymer and poly(imide-siloxane) random-block copolymers of increasing siloxane content. The studies employed 45-60 meter, thin-polymer-film mega-bore capillary columns to maximize surface area. The free energies of specific surface interaction with water and the dispersive components of the solid surface free energies were determined. An increase in the polymer siloxane content from 0-wt% to 10-wt% resulted in a decrease of approximately 4 kJ/mol in the free energy of water-specific surface interaction. A further increase in siloxane content to 30-wt% was not found to increase surface water resistance significantly. Dispersive components of the solid surface free energies of the copolymers were comparable to values reported for poly(dimethylsiloxane) homopolymer.     

Water Resistance of Poly(imide-siloxane) Adhesives: An IGC Surface Energetics Study

Inverse Gas Chromatography was utilized to examine the interaction of water vapor with the surfaces of a polyimide homopolymer and poly(imide-siloxane) random-block copolymers of increasing siloxane content. The studies employed 45-60 meter, thin-polymer-film mega-bore capillary columns to maximize surface area. The free energies of specific surface interaction with water and the dispersive components of the solid surface free energies were determined. An increase in the polymer siloxane content from 0-wt% to 10-wt% resulted in a decrease of approximately 4 kJ/mol in the free energy of water-specific surface interaction. A further increase in siloxane content to 30-wt% was not found to increase surface water resistance significantly. Dispersive components of the solid surface free energies of the copolymers were comparable to values reported for poly(dimethylsiloxane) homopolymer.     

The Effect of Surface Treatment on the Strength and Adhesion Characteristics of Phoenix dactylifera-L(Date Palm) Fibers

ABSTRACT

There is a growing interest in the use of natural/bio-fibers as reinforcing components for thermoplastics and thermosets. However, they do suffer from a few limitations, such as lower compatibility with relatively hydrophobic polymer matrixes. Thus, improvement of the interface and interphase interactions in natural fiber–polyester composites is essential. In this research date palm (Phoenix dactylifera-L) fibers were modified by surface treatment using chemical method in order to improve their adhesion to polyester matrixes. Alkaline treatment, as an example of dissolution and treatment with silane coupling agents were performed. Furthermore, a combination treatment of alkaline and silane coupling agents was also carried out. Fiber modifications were monitored by Scanning Electron Microscopy (SEM). In addition to that, the improvement of adhesion and strength between date palm–modified fibers and polyester matrix was investigated by single filament pull-out test as well as tensile tests. It was found, from interfacial shear strength values, that substantial improvements in fiber-matrix compatibility have been achieved. According to single filament pull-out test results, interfacial shear strength increased for all treated fibers as compared to non-treated fibers. Particularly, combination of alkaline and silane coupling agents resulted in substantial adhesion improvement to the polyester matrix in comparison to the untreated fibers and fibers treated by alkaline and silane methods only.     

Adhesion at Poly(Butylacrylate)-Poly(Dimethylsiloxane) Interfaces

We present an investigation of the adhesion modulation mechanisms of silica-like nanoparticles (MQ resins) incorporated in polydimethylsiloxane (PDMS) elastomers and acrylic adhesives. The Johnson-Kendall-Roberts (JKR) test has been used to gain information on the both zero velocity and the velocity dependence of the adhesive strength, avoiding as much as possible contributions to the adhesive strength of bulk dissipation in the adhesive (which is not the case with peel tests). As the incorporation of the MQ resins into the elastomers deeply affects their own mechanical properties, the loading and unloading curves of small poly(butylacrylate) (PBA) lenses on either PDMS elastomers, adsorbed PDMS and pure MQ resin layers are compared in a systematic manner. The PBA chains are observed to have a neat affinity for the MQ resin nanoparticles. When MQ resins are present at the interface, they tend to prevent facture propagation, thus producing a larger deformation of the PBA lens. The modulation of adhesion is then dominated by the corresponding dissipation inside the acrylic adhesive.     

Surface Modification of Poly(Tetrafluoroethylene) Films by Graft Copolymerization for Adhesion Improvement with Sputtered In-Sn Oxides

Surface modification of Ar plasma-pretreated poly(tetrafluoroethylene) (PTFE) films was carried out via UV-induced graft Copolymerization with glycidyl methacrylate (GMA), acrylamide (AAm) and hydroxylethylacrylate (HEA) to improve the adhesion strength with sputtered indium-tin-oxide (ITO). The surface compositions of the graftcopolymerized PTFE films were studied by X-ray photoelectron spectroscopy (XPS). The graft yield increases with increasing monomer concentration and Ar plasma pre-treatment time of the PTFE films. The T-peel adhesion strength was affected by the type of monomer used for graft Copolymerization, the graft concentration, and the thermal post-treatment after ITO deposition. A double graft-copolymerization process, which involved initially the graft copolymeri/ation with AAm or HEA, followed by graft Copolymerization with GMA. was also employed to enhance the adhesion of sputtered ITO to PTFE. T-peel adhesion strengths in excess of 8 N cm were achieved in the ITO graft-modified PTFE laminates. The adhesion failure of the ITO/PTFE laminates in T-peel tests was found to occur inside the PTFE films. The electrical resistance of ITO on all graft-modified PTFE surfaces before and after thermal post-treatment remained conslant at about 30 Ω square, suggesting that the graft layer did not have any significant effect or. the electrical properties of the deposited ITO.     

聚硅氧烷-聚氨酯表面改性剂

采用聚硅氧烷 -聚氨酯共聚物作为表面改性添加剂对热塑性聚氨酯进行共混改性。接触角和ESCA测定结果表明 :聚硅氧烷向共混物表面迁移 ,富集在共混物表面 ,使其接触角增大 ,具有憎水性。     

Adhesion of UV-Cured Laminates of Poly(ethylene-2,6-naphthalate) (PEN) and Poly(ethylene terephthalate) (PET) films

This paper describes the properties of an ultraviolet (UV) curable laminating adhesive system that can be used with PEN, PET and UV-stabilized PET films. The adhesive system that contains (2,4,6-trimethylbenzoyl) diphenylphosphine oxide (TPO) as photoinitiator was optimally cured with a V-bulb fitted ultraviolet irradiator. The laminated structures built with this adhesive system and PEN, PET and UV-stabilized PET films showed a large manufacturing operating window, both in terms of adhesive layer thickness, initial peel strengths above 1500 N/m, V- and D-bulb UV sources and curing speeds from 5– 10 m/min. The 600-h dry heat aging tests indicated that the UV-stabilized PET films underwent less than approximately 1% decrease in light transmission and less than a 1% gain in color. The UV-stabilized PET film and its laminate showed particularly strong retention of optical properties under damp aging and QUV weathering, compared to PEN and non-UV-stabilized PET films. Finally, the peel strengths of the laminates were retained to greater than 1300 N/m for laminate structures of 50 μm film thickness, whereas structures made from thicker films retained approx. 40–60% (700–1100 N/m) of their initial peel strength.     

Peel Adhesion of Poly(Vinyl Chloride) to Nitrile Rubbers

In addition to molecular interaction and physical entanglement of the molecular chains across the interface in poly (vinyl chloride)-nitrile rubber joints, at high temperatures and long contact times interfacial chemical bonds may be formed which seem to couple the two adherends thereby resulting in cohesive failure of the rubber matrix on peeling. This is verified by performing the peel tests at high temperatures, low peel rates and under swollen conditions. Infrared spectroscopic studies of the PVC/NBR blend reveal the formation of chemical bonds at the contact temperatures studied. The peel fracture energy is found to depend on the acrylonitrile content and presence of carboxylic content in the NBR, and the presence of stabilizer and plasticizer in the PVC phase, in addition to the molding and testing conditions.     

Surface Chemical Modification of Poly(Methylphenylphosphazene)

Summary The surface reactivity of poly(methylphenylphosphazene), PMPP, and its derivatives containing silane, PMPP-SiH, and alcohol, PMPP-OH, substituents was investigated. These polymers were fabricated into films by casting from THF solutions and reactions were carried out at the interface between solid film samples and solutions. The surface of PMPP was successfully modified by deprotonation under dilute conditions followed by reactions with RMe₂SiCl [where R = CH=CH₂, and H]. While surfaces of PMPP-OH were not readily modified, those containing Si-H groups reacted with oxygen when heated and with carbon tetrachloride. The polymer surfaces were examined by contact angle measurements, attenuated total reflectance infrared spectroscopy (ATR-IR), and scanning electron microscopy (SEM). We dedicate the paper to Christopher W. Allen in recognition of his outstanding contributions to inorganic ring and polymer chemistry.     

聚丙烯酸钠吸水性树脂的粘附性能测试及表征

为探讨聚丙烯酸钠吸水性树脂的粘附性能,设计了一种对其粘附性能的测定方法并进行了测试及表征,讨论了不同实验条件对树脂粘附性能的影响.结果表明,该吸水树脂的粘附性能随吸水量、初始压力和分离速率的增加具有一定的变化规律,并根据高分子结构理论、粘接的机械互锁理论和应力松弛等理论进行了解释.     

聚丙烯酸钠吸附树脂的制备及其粘附性能

以丙烯酸为原料,制备了聚丙烯酸钠吸附树脂。建立了一种对其粘附性能的测定方法并测定了其粘附性能,讨论了该树脂粘附性能的影响因素。结果表明:当中和度为70%,引发剂用量为单体质量的0.1%,交联剂用量为单体质量的0.01%,吸水倍率为2倍时,材料有最佳粘附性能。     

酯端基型聚酰胺胺树形高分子对聚(3-羟基丁酸戊酸共聚酯)结晶性能的影响

采用不同比例G3.5酯端基类型的聚酰胺胺(PAMAM)树形高分子氯仿溶液与聚(3-羟基丁酸酯-co-3-羟基戊酸酯)(PHBV)树脂氯仿溶液进行共混并流延成膜,采用差示扫描量热分析、偏光显微镜以及拉伸和直角撕裂等方式对制备的PHBV/PAMAM复合膜进行表征。结果表明,随着PAMAM树形高分子的加入,PHBV/PAMAM复合膜的玻璃化转变温度（Tg）越来越明显,初步表明其韧性增强; G3.5 PAMAM树形高分子的加入,可使PHBV的结晶度由61.70 %先下降至24.02 %,并逐渐下降,最后至结晶消失; PAMAM树形高分子的加入可使PHBV的直角撕裂强度大幅度提高,最高可由8.90 kN/m提高到22.10 kN/m;当PAMAM树形高分子含量为2.0份时,增韧效果最好。     

Effect of Poly(L-lactic acid) on Hydrolytic Degradation of Poly(glycolic acid)

The in-vitro degradation behavior of poly(glycolic acid) (PGA) rods and the composite rods containing poly(L-lactic acid) (PLLA) were investigated via mass loss, pH value change, scanning electron microscopy (SEM), thermogravimetric analysis (TGA), and differential scanning calorimetry (DSC). Since the degradation rate of PLLA is lower than that of PGA, PLLA/PGA composite rods exhibit a slower degradation rate in comparison with PGA. This finding indicated that it was possible to control the degradation rate of the composites by changing their composition. This result indicates that this kind of composite biomaterial may be applicable to devices for the need of prolonged degradation.     

Characterization of Poly(Aminosiloxane) Surface Chemistry on Aluminum Oxide

N-2-aminoethyl-3-aminopropyltrimethoxysilane (AAPS) was shown to react with aluminum oxide powder to form an amine/carbonate salt, as observed by diffuse reflectance infrared spectroscopy (DRIFT) and thermogravimetric analysis with mass spectroscopy (TGA-MS). TGA-MS, together with electron spectroscopy for chemical analysis (ESCA), reveal that the stoichiometric ratio of amine salt to free amine is higher on the surface of aluminum oxide powder than in a comparable neat film. In addition, TGA-MS shows that a nonstoichiometric ratio of CO₂H₂O is evolved upon heating the surface-treated powder (4.5/1), whereas the neat film evolves CO₂/H₂O at a ratio near unity. The high fraction of protonated amines, together with the higher ratio of CO₂/H₂O in the presence of alumina, is consistent with a proposed bonding mechanism which involves carbonate bridging between protonated amines and hydroxyl sites on the aluminum oxide surface.     

Characterization of Poly(Aminosiloxane) Surface Chemistry on Aluminum Oxide

N-2-aminoethyl-3-aminopropyltrimethoxysilane (AAPS) was shown to react with aluminum oxide powder to form an amine/carbonate salt, as observed by diffuse reflectance infrared spectroscopy (DRIFT) and thermogravimetric analysis with mass spectroscopy (TGA-MS). TGA-MS, together with electron spectroscopy for chemical analysis (ESCA), reveal that the stoichiometric ratio of amine salt to free amine is higher on the surface of aluminum oxide powder than in a comparable neat film. In addition, TGA-MS shows that a nonstoichiometric ratio of CO₂H₂O is evolved upon heating the surface-treated powder (4.5/1), whereas the neat film evolves CO₂/H₂O at a ratio near unity. The high fraction of protonated amines, together with the higher ratio of CO₂/H₂O in the presence of alumina, is consistent with a proposed bonding mechanism which involves carbonate bridging between protonated amines and hydroxyl sites on the aluminum oxide surface.     

Effect of Hydroxyl Content on Thermally Induced Change in Surface Morphology of Lithium Niobate (0001) Substrates

Two types of LiNbO₃(000 1 ) single-crystal substrates (LN), a conventional LN containing .10¹⁹ cm⁻³ OH ions, and a dehydrated LN were annealed in a dry O₂ atmosphere, and their surface morphologies were investigated using atomic force microscopy. For the conventional LN with more OH ions, the surface was significantly roughened in the temperature range of 600°–800°C, accompanied by a large outward diffusion of OH, and then it evolved to a steplike morphology at higher temperatures. However, the dehydrated LN surface changed gradually at temperatures of .700°C to flat terraces without any roughening process. The step heights of the annealed surfaces corresponded to n /6 (where n is an integer) of the c -axis length of the LN crystal. The dehydrated LN substrate, along with the dry-annealing process, achieved fairly flat surfaces.