Surface properties and platelet adhesion characteristics of acrylic acid and allylamine plasma-treated polyethylene

Acidic oxygen-containing and basic nitrogen-containing functional groups were incorporated onto thin films formed by plasma polymerization of acrylic acid and allylamine in a lowpressure glow discharge. ESCA, ATR–FTIR spectroscopy, and static contact-angle measurements confirmed the presence of these functional groups. Surface hydrophilicity of the acrylic acid plasma polymer decreased with time due to the diffusion of hydrophilic oxygencontaining functional groups away from the surface of the plasma-treated polyethylene. In contrast, the hydrophilicity of the allylamine plasma polymer increased with time because of the extensive post-plasma-treatment oxidation with atmospheric oxygen. In assessing the blood compatibility of these two types of plasma polymer surfaces by platelet adhesion and spreading, the acidic acrylic acid plasma polymers showed an improvement in thromboresistance, but the basic allylamine plasma polymers were more thrombogenic than was the untreated low-density polyethylene base material. © 1993 John Wiley & Sons, Inc.     

Infrared spectroscopic characterization of plasma-treated polyethylene

Thin polyethylene films cast on copper or gold were treated with low-pressure oxygen plasma. Changes in the chemical structure of these films were investigated by infrared spectroscopy using a reflection method in combination with chemical derivatization (CD) reactions. The potential of the CD is demonstrated for hydroxyl groups and carbonyl groups by the reaction with trifluoroacetic anhydride and hydrazine. The reaction conditions were varied to check for side reactions. The results of the derivatization are discussed in terms of secondary structures. © 1996 John Wiley & Sons, Inc.     

Inhibition of aging in plasma-treated high-density polyethylene

The effects of cross-linking and crystallinity on the aging of plasma-treated high-density polyethylene (HDPE) have been investigated. In the case of mixed argon and oxygen, aging has been found to be reduced with an increased amount of argon in the mixture owing to an increased degree of cross-linking. A similar decrease in hydrophobic recovery has been achieved by increasing the crystallinity of HDPE. Diffusion of polar functional groups from the surface into the bulk has been observed to be lowered by both increasing the degree of cross-linking and crystallinity. The samples were analyzed by angle-resolved XPS, contact angle measurements and SEM investigations.     

Photografting of argon plasma-treated graphite/PEEK laminate to enhance its adhesion

Graphite/PEEK laminates were treated by argon plasma followed by air aging and then photografting of α- glycidyl ω- acrylate bisphenol A(GABA) to improve their adhesion characteristics. The effects of plasma time and power and photografting time on the epoxy bonded single lap shear joints between graphite/PEEK laminates were investigated. An optimum photografting time was found at which the single lap shear strength was optimized to 37 MPa compared to 28 MPa and 7 MPa obtained with air-aged argon plasma activated and pristine samples, respectively. Argon plasma treatment followed by air aging of graphite/PEEK laminate introduces surface peroxides and hydroperoxides and these when cleaved with ultraviolet (UV) light in the presence of the GABA monomer results in covalent grafting of the latter to PEEK/graphite laminate surface. The epoxy functionality of the GABA monomer then reacts with the epoxy adhesive. X-ray photoelectron spectroscopy (XPS) confirms the appearance of surface peroxides and hydroperoxides on air-aged argon plasma treated samples and disappearance of the same with UV irradiation. With UV irradiation of the air-aged argon plasma treated samples, XPS indicates the appearance of ester groups. Without the grafting monomer, UV irradiation in air cleaves the peroxide and causes oxidation resulting in the formation of surface esters. In the presence of the grafting monomer, UV irradiation results in covalent bonding of the monomer to the peroxide/hydroperoxide through the acrylate functionality resulting in increased concentration of ether linkages as confirmed by our XPS data; the ester functionality present in the grafted monomer caused the appearance of the ester peak in the XPS spectrum.     

A closer look into the behavior of oxygen plasma-treated high-density polyethylene

X-ray photoelectron spectroscopy and near edge X-ray absorption fine structure investigation have been used to characterize the surfaces of two oxygen plasma-treated high-density polyethylene (HDPE) samples having different crystalline fractions. Both the observations indicate that a higher degree of crystallinity restricts the mobility of the polar functional groups on the HDPE surface. An increased crystalline order lowers the amount of oxidation and the aging of polar functional groups on the substrate surface. The results are supported by contact angle measurements and field emission scanning electron microscopic observations.     

Investigating the effect of power/time in the wettability of Ar and O2 gas plasma-treated low-density polyethylene

Low-pressure glow discharges of Ar or O₂ gas plasmas were used to increase the wettability of low-density polyethylene (LDPE) films in order to improve their adhesion properties hence making them useful in technical applications. Surface free energies of such films were estimated by the aid of contact angle measurements at different exposure power/time combinations for a series of test liquids. Additionally, plasma-treated samples were subjected to several aging processes to determine the durability of different plasma treatments. Characterization of the surface changes due to plasma treatments were carried out by means of attenuated total reflectance, Fourier transform infrared spectroscopy (FTIR-ATR) to determine the presence of polar species such as hydroxyl, carbonyl, carboxyl, etc. groups. Furthermore, atomic force microscopy (AFM) and scanning electron microscopy (SEM) were used to evaluate changes in surface morphology and roughness. Considering the semi-crystalline nature of the LDPE film, XRD studies were also carried out to determine changes in the percentage of crystalinity. The results showed that all low-pressure Ar or O₂ gas plasmas improve the wettability properties of LDPE films. Contact angles decreased significantly depending on the discharge powers and exposure times. Surface morphology was also found to vary with plasma discharge powers, exposure times, and the type of gas being used. Ar gas plasmas comparatively produced superior results.     

Wettability and adhesion studies of plasma-treated plastic substrates for gelatin holograms

The feasibility study of using polycarbonate and poly(methyl methacrylate) substrates treated with the oxygen plasma for dichromated gelatin holograms is reported. The contact angles of water on both treated and untreated substrates were measured to indicate the wettability of substrate surfaces. An appreciable increase in adhesion between the dichromated gelatin film and the polycarbonate substrate after the oxygen plasma treatment was demonstrated.     

Mechanical properties of polymer–paper laminates

Tensile mechanical properties of synthetic polymer–paper laminates were measured. The laminates were constructed by hot pressing a sandwich made of a sheet of paper between polymer films. There is complete penetration of the polymer inside the paper; no voids are left. Two different polymer matrices were used: poly(methyl methacrylate) and polyethylene. Several paper samples were utilized: an unoriented holocellulose paper (a strong paper), a highly oriented holocellulose paper, and an unoriented Whatman filter paper (a weak paper). The laminates contain from 0% to 50% of paper. Young's moduli and breaking strengths of the unoriented holocellulose paper laminates can be theoretically predicted from the properties of their constituents using laws of mixtures. The mechanical properties of the Whatman paper laminates are significantly higher than those predicted from the laws of mixtures. This indicates that the polymer increases the strength of the fiber-to-fiber bonds of the weaker sheets, although it does not change the bond strength of a stronger paper such as the holocellulose paper. For the oriented paper laminates, changes in Young's modulus with angle of measurement are explained by the composite materials theories if the angular variations in shear modulus are taken in to account. Changes in breaking strength with angle for the oriented laminates can be analyzed by Tsai and Azzi's theory for composite materials.     

Application of ultraviolet photografting technology to acrylamide/polyethylene to improve the interfacial adhesion of polyethylene/unsaturated polyester resin composites

This study was divided into two sections. In the first part, we used ultraviolet (UV) rays in the wavelength range 300–400 nm to remove the hydrogen atom from polyethylene (PE) and worked with a hydrophilic monomer to complete the grafting action. In the second part, we used the best conditions derived from the previous film grafting and applied them to fibers to achieve excellent adhesion for application in composite materials. For the handling process of the PE film, we initially used acrylamide (AM) as the monomer and then added acetone and benzophenone (BP) to form a reactive solution for the advanced photografting process. In general, the optimum concentrations of the monomer solutions obtained from the photografting of PE films were 2 mol/L of AM and 0.2 mol/L of BP. The UV irradiation time was fixed at 30 min. The optimum grafting conditions achieved in the first part of this research were applied in the photografting process for the PE fiber bundles in the second part. The unsaturated polyester (UP) resins were spread over the outer surfaces of the modified fibers. This was done to strengthen and increase the interface between the UP resins and the modified PE fiber. During the curing experiment of the grafted fiber bundles in the resin coatings, the best material quality was obtained under the following conditions: hardener content = 0.85% (relative to the UP resin weight), oven temperature = 80°C, and time frame = 5 h. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Mechanical factors in the adhesion of polyethylene to aluminium

The adhesion of low-density polyethylene to porous anodic films on aluminum was studied using the 180° peel test. Relative values of bond strengths, obtained by using polymer with and without antioxidant and by forming the bond in air or in vacuo, indicated that good adhesion could be obtained, despite previous evidence to the contrary, in conditions where oxidation of the polyethylene was suppressed. The relation between peel strength and anodic film thickness and film-forming voltage implied that the polyethylene entered pores in the film during bond formation. This was supported by the change of the category of the adhesion to one dependent upon polymer oxidation when the pores in the anodic film were sealed prior to bond formation. It is suggested that the mechanism of adhesion to porous anodic films on aluminum involves keying of the polymer into the pores in the film.     

Composition-dependent properties of polyethylene/kaolin composites. i. degree of crystallinity and melting behavior of polyethylene

Injection-molding and blow-molding grades of high-density polyethylene composites containing up to 30 vol. % of calcinated Kaolin were characterized by measurements of melting temperatures (T_m), heats of fusion (ΔH_m) and room-temperature densities. Both T_m and the degree of crystallinity of a polymer matrix proved essentially unchanged regardless of filler content and/or presence of a custom coupling agent. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 1267–1271, 1999     

Effect of curing agent on interfacial adhesion in acrylic polymer-based laminates

The effect of crosslinking on interfacial adhesion between an acrylic elastomer and poly(methyl methacrylate) has been studied using a 90° peel test. Elastomers were master-batched with a 1 : 10 sulfur/sodium mixture. The compounded elastomer was then bonded with poly(methyl methacrylate) by in situ curing at various temperatures. Variations in the curing affect both the mechanism of adhesion and separation. The relationship between peel strength and crosslink density is found to be P = kM_c. Crosslinking at relatively low temperatures produced a partially crosslinked elastomer that leads to high peel strengths. When crosslinked at 180°C, the acrylic elastomer was completely cured, and the peel strength decreased by more than 80%. This is consistent with an optimum level of crosslinking required for peel strength. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 67:1277–1284, 1998     

Improved adhesion of low-density polyethylene/EVA foams using different surface treatments

The adhesion between a polyurethane (PU) adhesive and four foams containing different low-density polyethylene (LDPE)/ethylene vinyl acetate (EVA) blends was improved by using different surface treatments. UV-ozone, corona discharge, and low-pressure oxygen plasma treatments for different times were used to increase the surface energy of the foams. The low-pressure oxygen plasma was the most successful surface treatment to promote the adhesion of the foams. A reduced length of treatment was needed to improve the adhesion of the foams containing higher EVA content. The surface treatments produced a noticeable decrease in contact angle values due mainly to the creation of different carbon–oxygen moieties and to the formation of cracks/heterogeneities on the foams surfaces. After oxygen plasma, removal of non-polar material from EVA surfaces allowed to expose acetate groups which are likely to be important for increasing the adhesion of the foams.     

Use of silanes and copolymers as adhesion promoters in glass fiber/polyethylene composites

Two organofunctional silanes and three functionalized copolymers were used as adhesion promoters in glass fiber/polyethylene‐reinforced composites. The performance of the coupling agents was investigated by mechanical property measurements, scanning electron microscopy, and dynamic mechanical analysis. Coupling achieved with the poly(ethylene‐g‐maleic anhydride) copolymer proved to be the most successful compared with the other copolymers (ethylene/vinyl alcohol, ethylene/acrylic acid) and silane agents (γ‐methacryloxypropyltrimethoxy, cationic styryl). The combined coupling performance of the silanes and copolymers examined in this study appears to be controlled by the coupling performance of the copolymer. Effective coupling was reflected in increased mechanical properties. Increased fiber/matrix adhesion is not always associated with effective coupling because structural changes occurring at the interface region can result in a deterioration of the material property. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 2877–2888, 2001     

Effect on thermal,mechanical, and biodegradable properties of plasma-treated fish scale powder/linear low-density polyethylene polymer composite films

In the present work, we report the effect of low-temperature plasma treatment on thermal, mechanical, and biodegradable properties of polymer composite blown films prepared from carp fish scale powder (CFSP) and linear low-density polyethylene (LLDPE). The CFSP was melt compounded with LLDPE using a filament extruder to prepare 1, 2, and 3 wt.% of CFSP in LLDPE polymer composite filaments. These filaments were further pelletized and extruded into blown films. The blown films extruded with 1, 2, and 3 wt.% of CFSP in LLDPE were tested for thermal and mechanical properties. It was observed that the tensile strength decreased with the increased loading content of CFSP, and 1% CFSP/LLDPE exhibited the highest tensile strength. To study the effect of low-temperature plasma treatment, 1% CFSP/LLDP polymer composite with high tensile strength was plasma treated with O₂ and SF₆ gas before blow film extrusion. The 1% CFSP/LLDPE/SF₆-extruded blown films showed increased thermal decomposition, crystallinity, tensile strength, and modulus. This may be due to the effect of crosslinking by the plasma treatment. The maximum thermal decomposition rate, crystallinity %, tensile strength, and modulus obtained for 1% CFSP/LLDPE/SF₆ film were 500.02°C, 35.79, 6.32 MPa, and 0.023 GPa, respectively. Furthermore, the biodegradability study on CFSP/LLDPE films buried in natural soil for 90 days was analyzed using x-ray fluorescence. The study showed an increase in phosphorus and calcium mass percent in the soil. This is due to the decomposition of the hydroxyapatite present in the CFSP/LLDPE biocomposite.     

Tailoring of the practical adhesion between polyethylene and galvanised steel

The practical adhesion of maleic anhydride grafted polyethylene (MAH-PE) to galvanised steel was studied using 3-point flexure tests, before and after hydrothermal ageing. Before bonding, the electro-galvanised steel was treated with γ-aminopropyltriethoxysilane (γ-APS). The influence of the silane coating thickness and deposition pH on the practical adhesion of MAH-PE to steel was investigated. FT-IR spectroscopy and microscopy enabled to gain understanding of the interphase formation between the silane and the metal substrate. It was found that, at the natural pH of the γ-APS, Zn ions dissolved in the silane coating with subsequent formation of crystals. This interphase could be held responsible for the better durability of the bonds than for silane coatings applied at quasi-neutral pH, for which dissolution of Zn ions was not observed.     

Effect of surface properties on the adhesion between PVC and wood veneer laminates

The interface between plastic and wood fibers strongly influences the mechanical properties of a plastic/wood-fiber composite. This paper presents a means for evaluating the effectiveness of surface treatment on the wood-fibers in the PVC/wood-fiber composites by investigating the adhesion between PVC and laminated wood veneers. Wood veneers were first treated with γ-aminopropyltriethoxysilane, dichlorodiethylsilane, phthalic anhydride, and maleated polypropylene for surface modification. The chemical modification made on the wood surfaces was then characterized using different complementary surface analytical techniques: X-ray photoelectron spectroscopy and surface tension measurements. The surface tension was determined from the equation of state for interfacial tensions and the measured contact angles of glycerol sessile drops on the wood veneers (both untreated and treated) and on PVC using the Axisymmetric Drop Shape Analysis–Contact Diameter (ADSA-CD) approach. The adhesion property was evaluated by measuring the tensile shear strength of single lap joints between two wood veneers bonded with a PVC film. The adhesion between PVC and wood veneer laminates was significantly improved when wood veneers were treated with amino-silane, while no improvement was observed for the other adhesion promoters. Our experimental results indicate that matching the surface tension is not sufficient to ensure good adhesion between PVC and wood veneers.     

Interfacial adhesion reaction of polyethylene and starch blends using maleated polyethylene reactive compatibilizer

The interfacial reaction of the polyethylene (PE)/starch blend system containing the reactive compatibilizer maleated polyethylene (m‐PE) was directly characterized by Fourier transform infrared (FTIR) spectroscopy. A significant amount of anhydride groups on m‐PE existed as hydrolyzed forms, resulting in a large amount of carboxyl groups. Using a vacuum‐heating‐cell designed in the laboratory, the carboxyl groups were successfully transformed into the dehydrolyzed state (i.e., anhydride group). This result enabled the direct spectroscopic observation of chemical reaction occurring at the interface. For the PE/starch blend system containing m‐PE, the chemical reaction at the interface was verified by the evolution of ester and carboxyl groups in the FTIR spectra. The effect of the reactive compatibilizer on the interfacial morphology was also examined by scanning electron micrography (SEM). Enhanced interfacial adhesion was clearly observed for the blend system containing reactive compatibilizer. Tensile strengths of blend systems containing m‐PE also increased noticeably compared with the corresponding system without compatibilizer. A similar observation was made for the breaking elongation data. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 767–776, 2002     

Functional group efficiency in adhesion between polyethylene and aluminum

The effect of different functional groups on the adhesion between polyethylene and aluminum has been studied. Poly(ethylene-co-butyl acrylate) (EBA) and poly(ethylene-co-vinyl acetate) (EVA) were used as such and provided polyethylene surfaces with two different kinds of ester groups, butyl ester and acetate, respectively. By alkaline hydrolysis in an organic solvent the surface functionality could be changed to carboxylate and hydroxyl, respectively. Finally, acid washing converted the carboxylate groups into carboxylic acid. The effect of the surface treatments were followed by reflection IR. T-peel tests of laminates made of the original, as well as the surface-treated polymers, and aluminum allowed an evaluation of the specific contribution to the adhesion for the groups in question. The peel strength increased linearily with the bulk concentration of comonomer in the original EBA and EVA samples. The values increased from about 100 N/m for polyethylene up to 2500 N/m in the case of 3.7 mol % of carboxylic acid. The efficiency of the investigated functional groups increased in the following order: ? H<? O? CO? CH₃ <? CO? O? C₄H₉ <? COONa～? OH<? COOH.     

Tensile properties and interfacial adhesion of silicone rubber/polyethylene blends by reactive blending

Two‐phase blends of silicone rubber (SR) and linear low density polyethylene (LLDPE) were prepared by reactive blending using peroxide crosslinking agent of SR. The tensile strength and elastic modulus of the SR were found to be increased by reactive blending with LLDPE without sacrifice of the elongation. The improvement of the tensile properties is attributed to the strong adhesion at the interface between SR matrix and LLDPE domain due to the chemical reaction by peroxide. The observation by polarized optical microscopies revealed that the debonding did not occur at the interface, but the LLDPE domains were elongated to longer one. Despite the elongation of the LLDPE domain, the blends exhibited good deformation recoverability. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46192.