Adhesion Improvement by UV Grafting onto Polyolefin Surfaces

High Density Poly(ethylene) (HDPE) and Poly(propylene) (PP) were subjected to several surface treatments, namely UV grafting of hydroxyethylmethacrylate (HEMA), plasma deposition of HEMA and oxygen plasma treatment. Treated surfaces were subjected to two post-treatment routines (extraction with ethanol and high temperature aging). The effect of these treatments on the adhesion of HDPE and PP to epoxy coated studs was evaluated by a pull test. No adhesion at all was recorded on untreated samples. On the other hand, all the treatments yield high bond strength in the case of HDPE: an average bond strength of about 290 kg/cm² and of about 200 kg/cm² was observed after UV grafting and plasma treatments. The treated samples were practically insensitive to post-treatments. As to PP, which undergoes chain scission in plasma, it is best treated by the comparatively milder conditions of UV grafting, which yields an average bond strength similar to that observed on HDPE. O₂ and HEMA-plasma-treated PP show a mean bond strength close to 50 kg/cm², and are deeply affected by the post-treatment routines.     

等离子体活化硅橡胶表面紫外接枝N-乙烯基吡咯烷酮

以等离子体活化硅橡胶,然后采用紫外光接枝法将N-乙烯基吡咯烷酮接枝于硅橡胶,同时使其自聚为稳定存在于橡胶表面的聚乙烯基吡咯烷酮。通过测定水接触角、红外光谱、X射线光电子能谱、扫描电镜等方法分析硅橡胶改性前后的表面变化。结果表明,改性后硅橡胶表面携带的新官能团和元素均带有聚乙烯基吡咯烷酮的特征,表明其与硅橡胶基质有较为牢固的化学键相连;硅橡胶表面的水接触角从改性前的110°降至改性后的18°,亲水性能改善明显。     

RTV表面紫外光接枝HEMA的研究

采用液相紫外光接枝方法,研究了室温硫化型硅橡胶与甲基丙烯酸β羟乙酯的接枝反应。利用红外光谱、扫描电镜对接枝物进行了表征,并讨论了引发剂用量、辐照时间对接枝率和接触角的影响,以及不同接枝率下接枝膜的吸水性能。结果表明:引发剂质量分数为为0.25%,辐照时间为2 min时,接枝效果较好;接枝后硅橡胶的亲水性得到明显改善。     

The grafting of methyl methacrylate onto ultrahigh molecular weight polyethylene fiber by plasma and UV treatment

In this study, ultrahigh molecular weight polyethylene (UHMWPE) fibers were treated with a gas plasma of argon for 5 min. The plasma-treated UHMWPE fibers were put into a methyl methacrylate solution with n-hexane or chloroform as the solvent and irradiated with a UV lamp. The UV irradiation time was changed. The surface topography that had a significant change on the fiber was seen by scanning electron microscopy. Infrared spectra (IR) and electron spectroscopy for chemical analysis (ESCA) were also studied to probe the surface atomic chemistry and to identify the functional groups and their relative changes with treatment conditions. The grafting content was estimated by the titration of esterfication method. It was found that the grafting amount for the system with chloroform as the solvent is larger than that for the system with n-hexane as the solvent. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 65:365–371, 1997     

XPS studies of poly(acrylic acid) grafted onto UV photo-oxidized polystyrene surfaces

UV photo-oxidation of polystyrene was achieved with 253.7 and 253.7/184.9?nm radiation in the presence of an atmospheric pressure of oxygen and analyzed by X-ray photoelectron spectroscopy as a function of treatment time. A methodical increase in the atomic percentage (at.%) of oxygen occurred during 253.7?nm activation up to 2?h of treatment time. Photo-oxidation with the 253.7/184.9?nm lamps resulted in a saturation level of ca. 35 at.% O. Initially, C–O and C=O groups were formed and then O–C=O type moieties. Poly(acrylic acid) was partially and/or thinly grafted onto the oxidized polystyrene surfaces.     

Surface Free Energy Modification of PET by Plasma Treatment—Influence on Adhesion

Different cold plasmas have been used to treat the surface of polyethylene terephtalate (PET) in order to improve the adhesion of alumina thin films deposited by RF sputtering. The influence of these treatments on the surface free energy of the polymer is shown by a study of wettability. ESCA analysis of the PET surface suggests that chemical changes occur as the polymer is plasma treated.

The adhesion of alumina films on PET is studied by using tensile testing. The results show that the surface treatment of the PET by a slightly oxidizing plasma, such as carbon dioxide, increases by a factor of 1.7 the adhesion of alumina coatings.     

Adhesion between polymer substrates and plasma films from tetramethylsilane and tetramethyltin by glow discharge polymerization

Adhesion between various polymer substrates and plasma films, which had been prepared from either tetramethylsilane or tetramethyltin by glow discharge polymerization and deposited on the surface of the polymer, was evaluated by the Scotch tape test and by lap-shear strength. It was found that the plasma films exhibited fairly good adhesion to the polymer substrates (with the exception of polypropylene). The position where failure occurred was determined by X-ray fluorescence analysis, scanning electron microscopy and energy diffractive X-ray analysis. This position was at an inner layer of the plasma film (cohesive failure of plasma film), within the polymer substrate (material failure of polymer) or at the interface between polymer substrate and plasma film (adhesive failure) depending upon the polymer substrate. These results indicate an important aspect of durability of surface modification by glow discharge polymerization.     

Adhesion Measurement of Amorphous C : H Films Deposited onto Stainless Steel. Spectroscopic Investigation of Interfaces

Amorphous hydrogenated carbon films obtained by the Plasma Assisted Chemical Vapor Deposition (PACVD) process, have been extensively studied by many authors^1,2,3 because of their interesting properties (hardness, optical transparency, chemical inertness, high electrical resistivity). In the present work, carbon films were deposited on stainless steel from glow-discharge polymerization of methane at reduced pressure, using an RF generator operating at 13.56 MHz.

These thin protective films are able to play the role of a primer to which another polymer (adhesive, paint, lacquer …) can subsequently be adhered. Surface treatments of the substrate and of the polymeric film were developed in order to obtain suitable adhesion properties, firstly of the film on the metal substrate, secondly of an adhesive on the hydrogenated carbon film. These treatments were monitored by two spectroscopic methods, viz. X-ray photoelectron spectroscopy (XPS) and (Low Energy Electron Induced X-ray Spectrometry) (LEEIXS). Mechanical measurements were made using a three-point flexure test⁴ (Norm AFNOR T 30 010).     

Improvement in the adhesion between copper metal and polyimide substrate by plasma polymer deposition of cyano compounds onto polyimide

The surface modification of Kapton film by means of plasma polymer deposition is discussed from the viewpoint of improving the adhesion between copper metal and Kapton film substrate. Plasma polymers of AN (acrylonitrile) and FN (fumaronitrile) were used for the surface modification, and the adhesion between the copper metal and the plasma polymer-coated Kapton film was evaluated by the T-peel strength measurement. The surfaces of peeled layers were analyzed by X-ray photoelectron spectroscopy (XPS) and the failure mode is discussed. The plasma polymer deposition of AN and FN shows an effective improvement in the adhesion between the copper metal and Kapton film; in particular, the AN plasma polymer deposition increased the peel strength 4.3 times. Failure occurred mainly in the Kapton film, and the adhesion between the AN plasma polymer and the Kapton film and that between the copper metal and the AN plasma polymer were found to be quite strong.     

Plasma Treatment of Polyacetal-Copolymer, Polycarbonate, Polybutylene terephthalate and Nylon 6, 6 Surfaces to Improve the Adhesion of Ink

Polyacetal-copolymer (POMB), polycarbonate (PC), polybutylene terephthalate (PBT), and nylon 6, 6 (PA6, 6) have been treated in an electron cyclotron resonance (ECR) plasma chamber to improve their adhesion properties towards ink. The chemical composition, the surface free energy, and the macroscopic adhesion have been studied by X-ray photoelectron spectroscopy (XPS), contact angle measurements, cross-cut tests, and the Scotch Tape test. Their dependence on the neutral gas, the treatment time, the pressure, and the ageing in air have been investigated. The XPS results reveal that the plasma treatment allows one to clean the surface and, if reactive gases are used, to incorporate new chemical species. The static and dynamic contact angles decrease with the plasma treatment and continue to decrease after contact with air. Very slow hydrophobic recovery is visible in the advancing contact angle, whereas the receding contact angle remains non-measurable even after more than a week of air exposure. Lower pressures and longer treatment times (120 s) lead to better macroscopic adhesion and reproducibility. For optimal treatment conditions (0.5 Pa, 120s N₂ plasma treatment time), the improvement of the adhesion remains excellent after seven days exposure of the sample in air.     

Adhesion of polyurethane to surface-modified steel

A number of procedures for cleaning the surface of steel have been tested. By washing with different solvents, ultrasonic solvent cleaning, sand-blasting or grinding, and desorption of organic contamination in an oxygen plasma, the degree of cleaning increased successively, as detected by XPS. The adhesion of polyurethane to steel measured in terms of the tensile shear strength could even approach the critical shear strength of the polyurethane itself. The highest adhesion strengths were obtained by using a combination of cleaning methods, including oxygen plasma treatment. A composite of optimally pretreated steel, a phenolic resin primer, and a polyurethane showed fracture far from the interface to steel in the boundary layer comprised of polyurethane and primer. Strong interactions between the phenolic resin and steel were indicated by the shift of the Fe 2P_3/2 peak to a binding energy of 712.7 eV. The strong adhesion-promoting effect of the hydrogen plasma pretreatment was produced by another effect. With the carbon incorporated in the steel, a thin adhesion-promoting plasma polymer layer was formed. Tests with model primers, instead of the phenolic resin and chemical modification of the phenolic resin, showed that the interaction between the phenolic resin primer and the polyurethane involved the phenolic hydroxyl groups.     

Adhesion of SiO2 thin films to plasma-treated SUS304 stainless steel substrates

The adhesion strength of the coated SiO₂ thin film to SUS304 stainless steel substrates with various surface treatment conditions is studied in this research. The surface of the SUS304 stainless steel substrate is first treated with 1000-W plasma and then a SiO₂ thin film is deposited onto the surface via radio-frequency magnetron sputtering. Scanning electron microscopy is employed to observe the surface and cross section of the coating and X-ray diffraction is used to analyze the crystallographic structure. Moreover, a nanoscratch test instrument was employed to examine the indentation, scratches, coating hardness, modulus of elasticity, coefficient of friction, and critical adhesion of the SiO₂ film and to obtain surface profiles. A comparison of the coating adhesion of the substrate surfaces with and without plasma treatment indicates that critical adhesion increases significantly after Ar/N₂/O₂ plasma treatment.     

紫外辅助增强ABS与镀层间粘结性的研究

在紫外光照射下利用环境友好的H_2SO_4-MnO_2-H_3PO_4-H_2O四元微蚀体系对丙烯腈-丁二烯-苯乙烯共聚物(ABS)进行微蚀处理,研究了紫外光功率及紫外光照射时间对ABS表面形貌、表面亲水性及粘结强度的影响。结果表明,在H_2SO_4-MnO_2-H_3PO_4-H_2O四元微蚀体系中,当微蚀时间为10 min,紫外光照射功率分别为300 W和500 W,照射时间分别为8 min和6 min时,ABS基板中的聚丁二烯相与聚丙烯腈-苯乙烯相之间存在较大的微蚀速率差,ABS基板表面的微孔数量多、致密且均匀,ABS基板的表面由憎水性变为强的亲水性,粘结强度分别为1.08 kN/m和1.10 kN/m,相较于四元微蚀体系在55℃无紫外光辅助照射下微蚀处理10 min后所得的0.64 kN/m,粘结强度显著提高。     

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.     

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.     

XPS/AFM study of the PET surface modified by oxygen and carbon dioxide plasmas: Al/PET adhesion

The formation of the interface between aluminium and O₂ or CO₂ plasma-modified poly(ethylene terephthalate) (PET) has been investigated by X-ray photoelectron spectroscopy (XPS). As demonstrated by the changes in the C 1s, O 1s, and A1 2p core level spectra upon A1 deposition, the metal was found to react preferentially with the original ester, with the plasma-induced carboxyl and carbonyl groups to form interfacial complexes. The phenyl ring at the modified PET surface was seen to be involved in the formation of the interface, but to a lesser extent. This confirms the high reactivity of the oxygen-containing groups towards the deposited A1 atoms. The adhesion between A1 and the plasma-modified PET films was evaluated by means of a 180° peel test. A considerable (up to ten times) improvement in adhesion was achieved by plasma treatment of the PET substrate, but for either plasma gas the adhesion strength was found to depend strongly on the plasma power and treatment time. The results are discussed in terms of the concentration of oxygen-containing groups at the polymer surface, the surface topography, and the possible presence of low-molecular-weight materials at the metal-polymer interface.     

Adhesion between polyurethane coating and EPDM rubber compound

The effect of the bulk modification of the EPDM rubber compound on the adhesion performance with polyurethane coating (PU) was studied. Ethylene propylene diene monomer (EPDM) was bulk modified using maleated EPDM, polynorbornene (PNR) or different curatives to improve adhesion to polyurethane coating. The coating–rubber composite adhesion performance was examined by peel, crack and abrasion tests followed by microscopic investigation of fracture surfaces and their chemical nature. The adhesion between the coating and the rubber substrate was improved using maleated EPDM or PNR, as well as different curing systems. The crack stress for the delamination of the polyurethane coating from the flexible bulk-modified rubber surface follows the trend: maleated EPDM > PNR > different curing systems > control.     

紫外光辐照聚丙烯膜接枝丙烯酸的研究

在水性体系中，通过紫外光辐照丙烯酸（AA）接枝到聚丙烯膜表面。考察了引发剂二苯甲酮（BP）用量、AA的体积分数、辐照时间、反应温度对接枝率的影响，以及不同接枝率下接枝膜对水接触角的变化。结果表明。接枝率在辐照时间为7min，AA体积分数为55％，BP用量为0．075g及反应温度为60℃时达到最大值。