Surface Treatment Of Polymers Research Articles

Enhancing the bond strength between glass fibre reinforced polyamide 6 and aluminium through μPlasma surface modification

Thermoplastic polymers generally exhibit relatively low surface energies and this often results in limited adhesion when bonded to other materials. Plasma surface modification offers the potential to functionalise the polymer surfaces, and thereby enhance the bond strength between dissimilar materials. In this study, glass fibre reinforced polyamide 6 (GFPA6) was modified using a novel μPlasma surface treatment technique and the effectiveness of the adhesive bond with aluminium was evaluated. The treated GFPA6 surfaces were characterised using atomic force microscopy (AFM), Raman spectroscopy, contact angle measurements, surface free energy calculations and wetting envelope analysis. The results show that there was a near exponential growth in root mean square roughness with increasing treatment scans. A significant increase in carbonyl and amide functionality on the polymer surface was observed using Raman spectroscopy. The total surface energy was found to increase from 42.2 mN/m to 67.6 mN/m following a single treatment scan. Significant increases in the tensile shear strength were observed up to 10 treatment scans, going from 1 kN to 2.3 kN, but no further increase was observed with additional treatment scans. These observations, coupled with the atmospheric nature of the technique, points to great potential as a rapid, on-line, and effective, polymer surface treatment technique.

Theoretical mechanism behind the higher efficiency of O than OH radicals in polypropylene surface modification: a molecular dynamics study

O and OH radicals are the most important reactive oxygen species in the plasma treatment of polymer surfaces. In our previous studies, we found that the modification efficiency of polypropylene (PP) surface by O radicals was approximately four times higher than that by OH radicals. This observation contrasts with the well-established fact that the chemical reactivity of O radicals with saturated hydrocarbons (C n H2(n + 1)) is 50–60 times lower than that of OH radicals. In this study, classical molecular dynamics simulations with a reactive force field were used to explain this contradiction. The results showed that the surface modification of PP by O or OH radicals is a Langmuir–Hinshelwood process. Both O and OH radicals penetrated the bulk PP, that is, physical adsorption occurred before the chemical reactions. The penetration depth of O radicals was greater than that of OH radicals. Compared to the case of OH radicals, alkoxy radicals (RO·) are more readily formed upon the interactions of the PP surface with O radicals. Furthermore, the β-scission (splitting of the C–C bonds) of RO· can be accelerated by the physically adsorbed O radicals, leading to earlier breakage of PP chains. The improved efficiency of the surface modification of PP upon exposure to O radicals, in contrast to that of OH radicals, can be attributed to the differences in the above three crucial processes. These findings are significant for modelling and understanding the mechanisms of plasma-polymer surface treatment at the atomic and molecular levels.

Progress of research on the bonding-strength improvement of two-layer adhesive-free flexible copper-clad laminates.

The arrival of the 5G era has placed high demands on the electronic products. Developing thin, light, and portable electronic products capable of simultaneously improving the transmission rate and reducing the signal delay and transmission loss is necessary to meet such demands. The traditional three-layer, adhesive, flexible copper-clad laminate (3L-FCCL) cannot satisfy these demands because of its adhesive component. The large thickness and poor heat resistance disadvantages of 3L-FCCL can be avoided with a two-layer, adhesive-free, flexible copper-clad laminate (2L-FCCL). However, 2L-FCCL has low bonding strength. This work introduces the selection of conductor materials and insulating base films for flexible copper-clad laminates. Modification studies aimed at increasing the bonding performance of 2L-FCCL are summarized based on three aspects. These modification techniques include the surface treatment of copper foils, modification and surface treatment of polyimide films, and surface treatment of liquid-crystal polymers. Prospects are further provided.

Polymer Surface Treatments for Drug Delivery and Wound Healing

Nanomedicine is a cutting-edge field at the intersection of nanotechnology and medicine that has experienced significant advancements in recent decades [...]

Effects of duty ratio on liquid- and polymer-surface treatment by a unipolar microsecond-pulsed helium atmospheric-pressure plasma jet

Effects of duty ratio of a unipolar microsecond-pulsed helium atmospheric-pressure plasma jet (APPJ) on liquid- and polymer-surface treatments were investigated. In addition, changes in the plasma plume length, gas temperature, excitation temperature, discharge current, absorption power, and optical emission spectra were examined by varying the other operating parameters, such as applied voltage and additive flow of oxygen or water vapor. As an example of liquid sample, de-ionized water (DW) was exposed to an APPJ, and the concentrations of the reactive species generated in the DW were measured as functions of the operating parameters. Polycarbonate, polypropylene, and polymethylmethacrylate were employed as exemplary substrate materials to investigate the effect of plasma treatment on polymeric surfaces. The APPJ treatment increased the surface energy and changed the wetting characteristics of the surface from hydrophobic to hydrophilic. X-ray photoelectron spectroscopy results showed that a short-time plasma treatment with He and/or He/O2, He/H2O affects the surface wettability owing to the introduction of polar groups.

Thin coating of silica/polystyrene core-shell nano/microparticles with hierarchical morphology onto polymeric films for fabrication of superhydrophobic surfaces

A novel coating process applied directly onto polymeric films offers a long-term alternative to short-term surface treatment of low surface energy polymers. In this paper, we report (i) an improved synthesis of a coating of raspberry-like particles directly onto polymeric surfaces and (ii) a novel method to obtain films with out-of-the ordinary superhydrophobic and self-cleaning properties. Inspired by the ‘lotus effect’ observed in nature, superhydrophobic surfaces were fabricated by combining dual-scale hierarchical coatings with low surface energy fluoroalkanes. Raspberry-like core-shell microparticles (MPs) composed of polystyrene (PS) core coated with silica (SiO2) shell (SiO2/PS) were synthesized by in situ dispersion polymerization of styrene directly on the surface of corona-treated polypropylene films. The PS MPs covered surface was then coated with SiO2 nano/microparticles (N/MPs) forming a hierarchical morphology on the surface. Biomimicry of the lotus leaf morphology is achieved by the hierarchical structure formed by dual-scale N/MPs that cover both PS particles and bare polypropylene surface, allowing air to be trapped in cavities formed. Adjustment of the diameters of the PS and SiO2 N/MPs allows the surface roughness of the coating to be controlled and optimized. 1H,1H,2H,2H-perfluorododecyltrichlorosilane was applied to lower the surface free energy, allowing the polymeric films to exhibit excellent superhydrophobic properties such as water contact angle above 170° and rolling angle of 0. Here, the application of the hierarchical coating was innovatively improved by direct synthesis of each layer onto the polymeric film. The treated surface portrays self-cleaning—soil placed over the surface is efficiently washed away by water, leaving clean trails. The durability of the microstructure and wetting properties of the coating were investigated. The coated films were observed to withstand a tape peeling test for up to 20 repetitions and sandpaper abrasion (1.96 kPa) for a distance of 2 m while retaining superhydrophobicity.

Molecular Behavior of 1K Polyurethane Adhesive at Buried Interfaces: Plasma Treatment, Annealing, and Adhesion.

One-part (1K) polyurethane (PU) adhesive has excellent bulk strength and environmental resistance. It is therefore widely used in many fields, such as construction, transportation, and flexible lamination. However, when contacting non-polar polymer materials, the poor adhesion of 1K PU adhesive may not be able to support its outdoor applications. To solve this problem, plasma treatment of the non-polar polymer surface has been utilized to improve adhesion between the polymer and 1K PU adhesive. The detailed mechanisms of adhesion enhancement of the 1K PU adhesive caused by plasma treatment on polymer substrates have not been studied extensively because adhesion is a property of buried interfaces which are difficult to probe. In this study, sum frequency generation (SFG) vibrational spectroscopy was used to investigate the buried PU/polypropylene (PP) interfaces in situ nondestructively. Fourier-transform infrared spectroscopy, the X-ray diffraction technique, and adhesion tests were used as supplemental methods to SFG in the study. The 1K PU adhesive is a moisture-curing adhesive and usually needs several days to be fully cured. Here, time-dependent SFG experiments were conducted to monitor the molecular behaviors at the buried 1K PU adhesive/PP interfaces during the curing process. It was found that the PU adhesives underwent rearrangement during the curing process with functional groups gradually becoming ordered at the interface. Stronger adhesion between the plasma-treated PP substrate and the 1K PU adhesive was observed, which was achieved by the interfacial chemical reactions and a more rigid interface. Annealing the samples increased the reaction speed and enhanced the bulk PU strength with higher crystallinity. In this research, molecular mechanisms of adhesion enhancement of the 1K PU adhesive caused by the plasma treatment on PP and by annealing the PU/PP samples were elucidated.

Plasma surface treatment of transparent commercial polymers to improve their wettability, gas barrier, and optical transmittance in the visible range

Plasma surface treatment of transparent commercial polymers to improve their wettability, gas barrier, and optical transmittance in the visible range

Outside Front Cover: Plasma Process. Polym. 6/2022

Outside Front Cover: In this study, a poly-diagnostics method is employed to evaluate the shield gas impact on the propagation of a plasma jet, the discharge dynamics and the intensity of the plasma species. The shield gas type and its flow rate have a significant impact on the plasma properties which provides beneficial information for future works on polymer surface treatment, coating deposition and the exclusion of unwanted species when using plasma jets. Further details can be found in the article by Mehrnoush Narimisa, Yuliia Onyshchenko, Olivier Van Rooij, Rino Morent, Ana Sobota, and Nathalie De Geyter (e2100247).

An effective method to optimise plasma immersion ion implantation: Sensitivity analysis and design based on low‐density polyethylene

AbstractThe performance of polymer surface treatment using plasma immersion ion implantation (PIII) depends on many operating parameters, such as treatment duration, radiofrequency power, pulsed bias voltage and pulse repetition rate, and the ion fluence applied on the polymer surface. Currently, the identification of optimal operating parameters to achieve specific performance targets is heavily based on trail and error with extensive experimental testing. Herein, we present an optimisation method based on sensitivity analysis using polynomial chaos expansion and experimental design with Kriging surrogate model to greatly reduce the amount of experiments. The combined effects of PIII operating parameters on low‐density polyethylene surface modifications are investigated, demonstrating the validation and effectiveness of the method and design. The new approach offers highly accurate and computationally efficient way for achieving optimum radical density, wettability and optical transmittance that are important for biomedical applications.

Does Plasma Treatment Effective for Surface Modification of Polymer? An Overview of Treatment Effect on Adhesive and Tribological Properties

Surface modification with plasma has been widely applied to polymeric materials. This treatment is intended to improve the surface properties of the polymer including its wettability and adhesiveness. The aim of this paper is to provide a review of the literature on the surface treatment of polymers with plasma, which focuses on the effects of adhesive and surface tribology properties. The related surface properties are also reviewed in order to strengthen the review of adhesive properties and tribology. Various types of plasma treatments that have been reviewed reported that plasma can be effectively used to improve surface properties, especially adhesive and tribological properties. On a small surface treatment has been developed plasma jet treatment which has been widely applied in biomedical applications.

Micromechanical measurement of adhesion of dehydrating silicone hydrogel contact lenses to corneal tissue

Adhesion properties, which can vary with multiple factors, of silicone hydrogel contact lenses are important to their performance and comfort in the eye. In this study, we developed and used a simple, representative testing system and method to study the adhesive interactions of different silicone contact lenses (balafilcon A and senofilcon A) on polished titanium alloy and porcine whole eye cornea under dehydrating conditions. Adhesive interactions for senofilcon A varied by hydration state for both corneal and titanium adhesion, starting low, rising to a maximum and falling with dehydration time and dehydration state. Balafilcon A showed a rise and fall against titanium, but retained a relatively constant adhesive interaction with corneal tissue over dehydration time. Senofilcon A reached the highest adhesion forces (400 mN) within 5 to 10 min of testing against cornea, then dropped with time after that. Johnson-Kendall-Roberts (JKR) theory was applied to determine the surface energy of the lenses, and work of adhesion (WOA) was also determined for both lenses. Similar trends as observed with the force-hydration curves were seen with surface energy and work of adhesion as well (peak surface energy of 8 N/m and work of adhesion of 80 µJ for senofilcon A). Video imaging of the adhesive interactions showed significant corneal deformation taking place during testing, and post-test analysis shows damage to the corneal tissue. This method could be used to assess pre-clinical performance of long-lasting contact lenses and the role of hydration state. Statement of significanceAdhesion properties of contact lenses play significant roles in their performance and comfort in the eye. Adhesion is influenced by polymer chemistry, counterface materials and hydration state of the contact lenses. However, no test method has been developed to directly study the adhesion properties between contact lenses and corneal tissue during the dehydration process. Our work aims to fill this gap by developing testing and analysis methods for evaluating the adhesive interactions in vitro between contact lenses of different chemistries and properties and different counter surfaces under dehydrating conditions over time. Our study shows that adhesive interactions of contact lenses are highly dependent on polymer type, surface treatment, counterface material and hydration state.

Atmospheric Pressure Plasma Surface Treatment of Polymers and Influence on Cell Cultivation.

Atmospheric plasma treatment is an effective and economical surface treatment technique. The main advantage of this technique is that the bulk properties of the material remain unchanged while the surface properties and biocompatibility are enhanced. Polymers are used in many biomedical applications; such as implants, because of their variable bulk properties. On the other hand, their surface properties are inadequate which demands certain surface treatments including atmospheric pressure plasma treatment. In biomedical applications, surface treatment is important to promote good cell adhesion, proliferation, and growth. This article aim is to give an overview of different atmospheric pressure plasma treatments of polymer surface, and their influence on cell-material interaction with different cell lines.

Investigation of a helium tubular cold atmospheric pressure plasma source and polymer surface treatment application

Cold atmospheric plasma (CAP) is a simple and inexpensive method to produce plasma in ambient air. In this study, CAP was generated by flowing helium gas through a glass tube with a copper electrode rounded externally around it to provide an electric field for gas excitation. The plasma extended for up to a few centimeters from the opening of the tube forming a plume. Optical emission spectroscopy (OES) was used to identify the composition of the plasma along the length of the plume. Four positions along the plume were investigated at flow rates of 1, 1.5, and 2.5 L min−1. Results revealed that the plume consisted of a varying composition of excited state species dependent on the location in the plume and gas flow rate. Identified in the emission spectra were the nitrogen second positive and first negative system along with OH* emissions at 282 and 308 nm. The OH* emissions, found at the opening of the tube, had a higher intensity as the flow rate increased and were attributed to impurities from the ambient air in the source tubing, while the N2 and N2 + emissions came from the nitrogen of the ambient air and dominated the rest of the measured spectra. Identifying the species and their intensities at different locations of the plume with different flow rates helped in determining the appropriate location and flow rate needed for a specific application of the surface treatment of ultra-high-molecular-weight-polyethylene (UHMWPE) to change its roughness. Additional spectra were taken in situ with an UHMWPE sample present to compare the reactive species of a free jet with those when a target was present. Finally, preliminary roughness tests showed increases of as low as three and as much as over ten times the pristine value depending on the position of the polymer in the plume and the source flow rate.

Treatment of date palm fibres mesh: Influence on the rheological and mechanical properties of fibre-cement composites

An experimental study was conducted on the influence of different treatments of date palm fibres on the properties of mortars in both fresh and hardened states. Three types of treatment were discussed: boiling water treatment, sodium hydroxide treatment and a polymer surface treatment based on linseed oil. As a first step, tests of water absorption, setting times and direct tensile strength were performed on single fibres to assess the relevance of the predominant parameter for each treatment. Thereafter, unreinforced mortar and mortars reinforced with raw and treated date palm fibres were made and tested using a flow table test, as well as for porosity accessible to water, three-point bending strength, compressive strength and capillary water absorption. The results for individual fibres show that treatments with a 3-hour boiling of the fibres, a 3% NaOH concentration, and a 1.5% linseed oil/fibre ratio yield the lowest absorption kinetics, the shortest setting times, and the most interesting tensile properties. However, the results for fibrous composites indicate that the workability of mortars reinforced with linseed oil treated fibres was improved compared with raw fibres. In the hardened state, boiling and sodium hydroxide treatments improve the flexural strength of the composites. The same trend was observed for compressive strength. Therefore, the mortar reinforced by fibre treated with linseed oil does not improve the strength and is the most porous. The incorporation of date palm fibres decreases the kinetics of the capillary absorption of mortars compared to unreinforced mortar. The lowest absorption coefficients are obtained after the treatment with linseed oil.

Surface topology engineering of ferroelectric polymer film by high-pressure plasma etching

Oxygen plasma processis usually implemented for selective etching of organic films. The oxygen plasma etches the organic materials non-uniformly, the deep etching generatesthe rough surface morphology. However, high-pressure plasma environment can maintain the initial surface status independent of etching depth. Here, a high-pressureplasma etching method that can reduce the surface roughness of ferroelectric polymer film is presented. After an amorphous polymer having the same etching rate is formed, the surface of the amorphous polymer film is treated with a plasma, which makes it possible to have a smoother surface than the original film. This process is expected to be useful for the surface treatment of all crystalline polymers, including ferroelectric polymers.

Surface Modification and Adhesion Mechanism of Isotactic Polypropylene with Low-Energy Electron-Beam Treatments.

Recently, smaller-size electron-beam (EB) accelerators have offered EB irradiation in laboratory systems. Therefore, polymer surface treatments with low-energy EB have been developed in the past years. For high adhesion strength, low-energy EB treatment is also a promising method in comparison to plasma surface treatment. In the plasma treatment, the mechanism of the effect on the adhesion properties has been proved and the excess treatments led to the formation of a weak boundary layer and reduction of adhesion strength. In contrast, the low-energy EB possesses high penetration ability. In this work, we focused on the surface treatments of isotactic polypropylene (it.PP) with low-energy EB irradiation for adhesion. The dependence of adhesion strength on the absorbed dose of electron beam was evaluated, and the mechanism of electron beam on the adhesion properties was investigated from various perspectives of surface properties and morphology. Compared to that of plasma-treated it.PP, the adhesion strength of it.PP with electron-beam irradiation increased drastically. We proved that the radical was generated in the substrates after electron-beam treatments and would form covalent bonds between adhesives and substrates, which achieved higher adhesion than plasma treatments. In addition, the electron beam reached effectively a deep region from the top surface of the substrates and provided larger adhesion strength.

Quantitative measurement of the effect of OH radicals on the surface treatment of polypropylene

AbstractOH and O radicals are considered to be the most important reactive species in polymer surface treatment using plasma. However, the treatment effect of OH and O radicals has not been measured quantitatively due to the difficulty in separating the effects of OH and O from those of many other reactive species produced in plasma. In this study, the effect of OH radicals on the surface treatment of polypropylene (PP) is quantitatively measured using specially designed equipment that was developed in our previous research. The equipment produces OH radicals using vacuum ultraviolet photolysis of water vapor and supplies them to the PP surface while limiting the supply of other reactive species. The water contact angle on the PP surface is decreased by 1° per OH supply of [OH]τ = 7.1 × 1012 s/cm3, where τ is the treatment time.

The quality improvement of polymer-surface treatment due to optimal toolpath and cutting parameters

This article discusses the main directions of development in the sphere of polymer edge cutting machining. The authors proposed a special geometry of the cutting tool, as well as the technology for processing the case-shaped part, found on this study.

Localization of full-length recombinant human proteoglycan-4 in commercial contact lenses using confocal microscopy

The aim of this study was to determine the sorption location of full-length recombinant human proteoglycan 4 (rhPRG4) tagged with fluorescein isothiocyanate (FITC) to four silicone hydrogel contact lenses [balafilcon A (PureVision, Bausch + Lomb), senofilcon A (Acuvue Oasys, Johnson & Johnson), comfilcon A (Biofinity, CooperVision), lotrafilcon B (Air Optix, Alcon)] and one conventional hydrogel lens [etafilcon A (Acuvue 2, Johnson & Johnson)], using confocal laser scanning microscopy (CLSM). Lenses (n = 3 each) were incubated under two conditions: (1) FITC-rhPRG4 solution at 300 μg/mL and (2) phosphate-buffered saline, for 1 h at 37 °C in darkness with gentle shaking. The central 4 mm of each lens was removed and viewed with the Zeiss 510 CLSM using an argon laser at 488 nm (FITC excitation 495 nm, emission 521 nm). Depth scans were taken at 1 μm intervals to a maximum depth of 100 μm. All lens materials demonstrated sorption of rhPRG4. Both senofilcon A and balafilcon A revealed FITC-rhPRG4 penetration into the bulk of the lens, generally favoring the surface. rhPRG4 was observed exclusively on the surface of lotrafilcon B, with no presence within the bulk of the lens. rhPRG4 was evenly distributed throughout the bulk of the lens, as well as on the surface, for comfilcon A and etafilcon A. The sorption profile of FITC-rhPRG4 was successfully visualized using CLSM in various contact lens materials. The polymer composition, surface treatment and pore size of the material can influence the sorption of rhPRG4.