Surface Properties Of Polypropylene Research Articles

Improvements in Surface Properties of Polypropylene, Polycarbonate and Polyurethane by Nonthermal Atmospheric Pressure Plasma Arc Jet in Air

Improvements in Surface Properties of Polypropylene, Polycarbonate and Polyurethane by Nonthermal Atmospheric Pressure Plasma Arc Jet in Air

Development of a water-based functional additive by using isobornyl acrylate copolymer to improve ink-adhesion on untreated polypropylene surfaces: A comparative approach

The good barrier and hot-fill properties of polypropylene (PP) films and sheets make packaging industries advantageous. However, printing over a PP substrate is a major issue encountered in the packaging industry. The present study intends to prepare, characterise, and compare isobornyl acrylate (IBOA)-co-acrylic acid (AA) and isobornyl acrylate (IBOA)-co-methacrylic acid (MAA) based non-halogenated functional additives by using oil in water emulsion processes. The bornyl group of IBOA helps in enhancing molecular bonding with the polypropylene (PP) surface. The various properties of these synthesised functional additives were characterised using dynamic light scattering-particle size and zeta potential analysis, differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), thermal gravimetric analysis (TGA), and gel permeation chromatography (GPC). The adhesion of these functional additive incorporated ink samples on different untreated PP surfaces was compared using the cross-cut adhesion test. The methacrylic acid based functional additive shows better adhesion properties as compared to acrylic acid.

Effects of Chromic Treatment on the Surface Properties of Polypropylene (PP) Wood Composites

The moisture sensitivity of wood–polymer composites (WPCs) is mainly related to their hydrophilic wood components. Coatings are among the alternatives that improve the dimensional stability of these composites. However, the adhesion of most coatings to the WPC surface is generally poor. Thus, chemical and/or mechanical treatments should be applied to the WPC surface to improve the coating adhesion. Therefore, the main objective of this study was to improve the adhesion coating of polypropylene (PP) WPCs through a chromic treatment. PP was reinforced by three different pulp fibers (kraft, thermomechanical (TMP), and chemothermomechanical (CTMP)) at three fiber contents (50, 60, and 70% w/w). A chromic treatment was applied to the PP-based WPCs to activate the surface of the composites and alter their roughness parameters, creating a higher interfacial zone that improved the bonding of the epoxy coating to the surface of the PP composites. The chromic treatment increased the roughness of the surface. An increase in profile and surface parameters was observed after treatment. This treatment modified the chemical composition of the surface by creating polar carbon–oxygen groups and increasing the carbonyl and hydroxyl indexes.

Surface Modification of Polypropylene by Atmospheric Pressure Plasma

In this investigation, we studied the influence of atmospheric pressure plasma treatment on the surface properties of polypropylene (PP). The PP samples were treated for various durations using a gliding arc plasma source with air as a working gas. The formation of polar groups (–OH and C = O) on the PP surface after plasma treatment was evaluated and analyzed using Raman spectroscopy and attenuated total reflection–Fourier transform infrared spectroscopy. The contact angle was measured using polar and non-polar liquids to obtain the polar and dispersive components as well as the surface free energy of the PP before and after treatment. A sevenfold increase after treatment was observed for the polar component, while hydrophobicity decreased 73% after treatment. Finally, changes in topography were observed using atomic force microscopy (AFM) analysis before and after plasma treatment. AFM images showed that under atmospheric treatment, the PP surface underwent etching, reducing the surface roughness. Microhardness measurements of the films also revealed significant changes in mechanical properties after plasma treatment.

The crystallization of polypropylene/halloysite fibers

The halloysite (HNT) in the form of nanotubes was used as an agent for the improved mechanical, thermo-mechanical as well as surface properties of polypropylene (PP) fibers. The halloysite is the nanoadditive that can affect differently the crystallization of PP in the non-oriented and oriented systems. The structure and mechanical properties of PP and PP/HNT fibers depended on the crystallinity and crystallization kinetics of PP at the fiber preparation. The Avrami method on the determination of isothermal crystallization kinetics parameters as well as an estimation of melting and crystallization temperatures and melting and crystallization enthalpies was used for the study of thermal behavior of polypropylene/halloysite non-oriented and oriented blends and fibers. Morphological structure, mechanical and thermo-mechanical properties of polypropylene/halloysite fibers were observed. An influence on all assessed properties was evaluated from the point of halloysite content in the PP and/or PP fibers. The increased HNT content in the non-oriented PP/HNT blends at the isothermal crystallization increases the rate crystallization (decreased t1/2 and free energy σe, increased K) of PP in comparison with the pure PP. The crystallinity of PP in the oriented PP/HNT fibers is not primarily affected by addition of the HNT content 3 mass% and does not change their mechanical and thermo-mechanical properties. 5 mass% HNT increases the crystallinity of PP in PP/HNT fibers expressing mainly the decrease in tenacity at the break, Young’s modulus and shrinkage.

Improving the Cement Based Reinforced Composites by Use of Partially Oxidized PP Fiber

In improving fiber reinforced cement-based composites, it is critically important to enhance the bonding strength between fibers and cement hydrate. Polypropylene (PP) fiber is a property enhancing additive, commonly used in cement-based composites. In this study, we tried to modify the surface properties of PP to enhance its bonding with calcium silicate hydrate (C-S-H). The surface was at least partly converted from lyophilic to hydrophilic by partial oxidation using potassium dichromate. The change in surface properties was examined by FT-IR, AFM, SEM and contact angle. The appearance of peaks at 1635, 1650 and 3200 cm-1 in FTIR spectra for the treated PP, indicated the adsorption of water molecules on the surface, verifying the increase in hydrophilicity of PP. The AFM observation depicted that the roughness of partially oxidized PP surface was significantly increased. The contact angle was reduced due to the increase in hydrophilicity of the PP surface. However, the tensile strength of PP fiber had no significant reduction after being subjected to partial oxidation. Finally, AFM and SEM observations have shown that treated PP film bonded to C-S-H more tightly than that of original PP. It is suggested that partial oxidation of PP is an effective method to improve cement-based composites.

Surface and mechanical properties of polypropylene/clay nanocomposite

Huge consumption of polypropylene in the industries like automotive motivates academic and industrial R&Ds to find new and excellent approaches to improve the mechanical properties of this polymer, which has no degradation effect on other required performance properties like impact resistance, controlled crystallinity, toughness and shrinkage. Nowadays, nanoparticles play a key role in improving the mechanical and surface properties of polypropylene. In this study, three compositions of "Polypropylene/nanoclay", containing 0%, 2% and 5% of nanoclay were prepared in internal mixer. For characterizing the nanoclay dispersion in polymer bulk, TEM and XRD tests were used. For scratch resistance test, scratch lines were created on the load of 900 grain on sheets and SEM images were taken and compared with neat PP scratch image. Crystallinity and mechanical behavior were studied. The results showed that mechanical properties and scratch resistance of the composites have been improved.

Studies on adhesive properties of polypropylene (PP) and polycarbonate (PC) film surfaces using DC glow discharge plasma

Direct current (DC) glow discharge plasma has been used to increase the adhesive properties of polypropylene (PP) and polycarbonate (PC) film surfaces and make them suitable for technical applications. The modified surfaces were characterized by contact angle, atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS) analysis. Also, improved adhesion properties were analyzed using T-Peel strength test. The results show that the surface wettability has been increased due to decrease in contact angle and increase in surface energy. After plasma treatment the root mean square (RMS), roughness of PP and PC films were gradually increased with different exposure time. XPS results detected polar functional groups on plasma treated PP and PC film surfaces. T-Peel strength test for adhesion strength measurement showed that the surface modified PP and PC films were increased with adhesive properties. Key words: Glow discharge, polypropylene (PP), polycarbonate (PC), contact angle, surface energy.

Effect of injection molding cycle time on surface properties of polypropylene

This paper deals with the effect of shortening injection molding cycle time on morphology and properties of the compounded materials of polypropylene (PP), ethylene propylene rubber (EPR) and talc. Recently, shear rate and cooling speed in injection molding for automotive parts have been increasing because of higher productivity. Orientation and crystallinity in the skin layer, which were measured by a polarizing optical microscope and wide angle X-ray diffraction, increased when shortening the cycle time. Phenomenon of bleeding out additives was observed for the evaluation of surface properties by ATR-FTIR. For decreasing resin temperature, higher crystallinity restricted diffusion of additives at the same position in the injection molded plaques. But comparing the gate with the flow end, the difference of bleeding in the position was controlled by the other factors.

Surface properties of polypropylene following a novel industrial surface‐treatment process

AbstractPolypropylene (PP) is used in many automotive applications where good paint adhesion is of primary importance. PP is widely known for its low surface energy which impacts negatively on its adhesion strength. PP surfaces were modified using a new industrial surface‐treatment process known as the Accelerated Thermo‐molecular adhesion Process (ATmaP). ATmaP grafts functional groups to the polymer surface derived from an atomised and vapourised nitrogen‐containing coupling agent. The surface properties and adhesion performance of PP samples treated using the ATmaP process and two different flame processes were compared using XPS, time‐of‐flight secondary ion mass spectrometry (ToF‐SIMS) and mechanical testing (pull‐up tests). The latter showed that ATmaP improved adhesion strength significantly in comparison with conventional flame treatments. XPS showed an increase in oxygen and nitrogen concentration on the surface of ATmaP‐treated samples compared with untreated and flame‐treated samples. Principal components analysis (PCA) of the ToF‐SIMS data revealed the major phenomena occurring during the surface treatment of PP samples. Early stage events, including the chain scission of the PP backbone chain and the subsequent reaction of these chains with the surrounding air, are captured by the first principal component (PC1). The increase in the concentration of NO surface functional groups resulting from ATmaP treatment is captured by the second principal component (PC2). Copyright © 2008 John Wiley & Sons, Ltd.

Modification of polypropylene films in a direct-current discharge

The surface properties of polypropylene (PP) films modified in a direct-current discharge at the anode and cathode, as well as their change during long-term storage were studied. It was shown that the greatest decrease in the contact angles and the increase in the total surface energy and the polar component are observed for the films treated at the anode. Changes in the chemical structure of PP films were investigated by means of Fourier-transform IR spectroscopy and X-ray photoelectron spectroscopy techniques.

Adhesive properties of polypropylene (PP) and polyethylene terephthalate (PET) film surfaces treated by DC glow discharge plasma

In this study, the adhesive properties of the plasma modified polypropylene (PP) and polyethylene terephthalate (PET) film surfaces have been investigated. Hydrophilicity of these polymer film surfaces was studied by contact angle measurements. The surface energy of the polymer films was calculated from contact angle data using Fowkes method. The chemical composition of the polymer films was analyzed by X-ray photoelectron spectroscopy (XPS). Atomic force microscopy (AFM) was used to study the changes in surface feature of the polymer surfaces due to plasma treatment. The adhesion strength of the plasma modified film was studied by T-peel strength test. The results showed a considerable improvement in surface wettability even for short exposure times. The AFM and XPS analyses showed changes in surface topography and formation of polar groups on the plasma modified PP and PET surfaces. These changes enhanced the adhesive properties of polymer film surfaces.

Finite element method parametric study on scratch behavior of polymers

AbstractParametric studies were performed using finite element analysis (FEA) to learn how material and surface properties of polypropylene (PP) affect scratch behavior. Three‐dimensional FEA modeling of scratching on a PP substrate with a spherical‐tipped indenter is presented. Three different loading conditions, that is constant scratch depth, constant normal load, and linearly increasing normal load, are adopted for this parametric study. From the FEA findings, it is learned that Poisson's ratio has a negligible effect on scratch performance, whereas raising the coefficient of adhesive friction induces a significantly larger residual scratch depth and tangential force on the scratch tip. Increasing the Young's modulus of a material does not necessarily improve its overall scratch performance. On the other hand, modifying the yield stress of a material has a major impact on scratch resistance as a higher yield stress reduces the residual scratch depth. From this numerical effort, it is concluded that the yield stress and coefficient of adhesive friction are the most critical parameters to influence the scratch performance of a material. Analyses also suggest that the general trend in the parametric effect of the above four parameters on scratch behavior is independent of the applied normal load level. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 1435–1447, 2007

Characterization of an anion-exchange porous polypropylene hollow fiber membrane for immobilization of ABL lipase

Hollow fiber membrane offers the advantage to integrate catalytic conversion, product separation and catalyst recovery into a single separation process compared to conventional systems. Polypropylene (PP) hollow fiber membrane is a chemically inert and stable membrane with high potential for enzyme immobilization. The surface properties of polypropylene have been modified by radiation induced graft polymerization. Samples were prepared by grafting of glycidylmethacrylate (GMA) using gamma radiation, at different monomer concentrations and irradiation dose. The resulting epoxy was converted into a diethylamino group as an anion-exchange medium to bind the lipase molecules. Surface properties of the grafted and amine treated samples were characterized using atomic force microscopy (AFM), scanning electron microscopy (SEM) and contact angle measurements. AFM revealed higher surface roughness for grafted samples than that of virgin polymer. SEM micrographs illustrated that the porous network was retained at high degree of grafting. Contact angle measurements showed excellent wetting properties with water for the grafted and amine treated membranes. Thermal properties were studied using differential scanning calorimeter (DSC) and thermogravimetic analysis (TGA). It was observed that grafting occurred mainly in the amorphous region of the membranes. Activity and operational stability of ABL lipase, isolated from Arthobacter sp. were assayed after immobilizing it to the modified PP hollow fiber. Immobilized lipase retained 20U/g activity after ten hydrolysis cycles and 68% residual activity after 12 weeks of storage.

Surface properties of plasma-modified polypropylene and propylene-hexene-1 copolymer films

The surface properties of polypropylene and propylene and hexene-1 copolymers synthesized on the rac-Me2SiInd2ZrCl2-polymethylalumoxane isocpecific metallocene system and the Ph2C(Cp)(Flu)ZrCl2-polymethylalumoxane syndiospecific system were studied. It was found that syndiotactic polypropylene films were less hydrophobic than isotactic polypropylene films, whereas the films of propylene and hexene-1 copolymers were less hydrophobic than the films of corresponding homopolymers. The hydrophobicity of samples decreased with the hexene-1 content of the copolymer. Treatment in a dc discharge resulted in noticeable surface hydrophilization in all of the test polymer samples. There is a correlation between the surface parameters and the density of surface charge induced in the polymers by dc discharge treatment.

Comparative actions of a low pressure oxygen plasma and an atmospheric pressure glow discharge on the surface modification of polypropylene

We compared the action of low pressure oxygen plasma (LPOP) on the surface modification of polypropylene (PP) with that of atmospheric pressure glow discharge (APGD) with liquid electrolyte cathode. Both water and 0.05 M KCl aqueous solution were used as liquid cathodes in APGD system. The surface properties of PP were characterized by contact angle measurement followed by surface free energy calculation, Fourier Transform Infrared by Attenuated Total Reflectance (FTIR/ATR) and Atomic Force Microscopy (AFM). It was found that the actions of two processes were qualitatively the same. After treating PP surface with both methods, we commonly observed OH-groups, CO groups in ester, ketone and carboxyl groups, CO groups in unsaturated ketones and aldehydes. Both modification processes were also able to improve surface free energy and surface smoothing. In spite of some common features, however, the kinetic regularities of two processes were different. Characteristic time to reach stationary state in LPOP was always shorter than in APGD. Etching rates were higher in LPOP. Besides, the depth profile of oxygen-containing groups was somewhat different as well as surface morphology.

Analysis of polymer surface treated by dielectric barrier discharge

We investigate polymer surfaces after exposing them to dielectric barrier discharges with different flowing gases (He, CF4) in air. The relationship between the gas characteristics and the surface properties of polypropylene (PP) is determined by contact angle measurement, optical emission spectroscopy and x-ray photoelectron spectroscopy. Experimental results reveal that there is a definite relationship between the surface energy and the surface chemical composition of PP and also indicate that the hydrophilicity of PP in an atmospheric pressure (AP) discharge is more dependent on ionic bombardment than on the atomic oxygen composition at the surface and its hydrophobicity depends on the fluorine composition at the PP surface. In addition, it turns out that in a CF4 discharge at AP, the CF3 molecular band exhibits a continuum band at the orange line in the visible range.

Surface treatments of subdenier monofilament polypropylene fibers to optimize their reinforcing efficiency in cementitious composites

AbstractThe surface properties of polypropylene (PP) fibers have an important effect on their reinforcing efficiency in cementitious composites. Two new methods of modifying the surface of subdenier monofilament polypropylene fibers were introduced, as well as the performances of the fiber‐reinforced mortar. The results show that the surface modification improved the mechanical performance of the fiber‐reinforced mortars, such as compressive strength and flexural strength, and the reinforcing efficiency depends on the adopted method. The enhanced interfacial bonding between treated fibers and the cementitious matrix, compared with that of unmodified fibers, was investigated using scanning electronic microscopy. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 2637–2641, 2004

Blood-contacting properties of polypropylene surfaces

Blood-contacting properties of polypropylene varied with changes in crystalline-amorphous microstructure such as the crystallinity and the degree of orientation. The results from our evaluation of surface adhesiveness using polymeric glue and water structure which was sorbed into the surfaces indicate that variations in the microstructure may cause differences in macromolecular entanglement with the glue and hydrophobic interaction at the surfaces. Therefore, the prevention of these interactions may help to attain better blood-contacting properties.

Mechanistic aspects of blood-contacting properties of polypropylene surfaces -from the viewpoint of macromolecular entanglement and hydrophobic interaction via water molecules

Polypropylene surfaces with a particular crystalline-amorphous microstructure have been demonstrated to reduce protein adsorption and platelet activation. Such blood-contacting properties may be affected by the crystalline-amorphous microstructure of the surfaces, although wettability such as dynamic contact angles and surface free energy components were almost constant, being independent from the variation in the microstructure. In order to clarify the mechanistic aspects on their blood-contacting properties, the physicochemical properties of the surfaces were evaluated for a series of compression-molded polypropylene sheets in terms of the work of adhesion and the structure of sorbed water. The work of adhesion of the compression-molded sheets increased with decreasing surface layer crystallinity, presumably due to macromolecular entanglement with a polymeric glue used. The work of adhesion involving macromolecular entanglement may occur between proteins and the surfaces. Thus, a decrease in the surface layer crystallinity is considered to cause an increase in the protein adsorption. The structure of water sorbed into the sheets changed - it was more gaseous (isolated) at the surfaces with a higher crystallinity. This suggests that the hydrophobic interaction via water molecules increased with surface layer crystallinity, resulting in increasing protein adsorption and denaturation. Thus, it is considered that both macromolecular entanglement and hydrophobic interaction are important on the mechanistic aspects of blood-contacting properties of polypropylene surfaces. In order to confirm this hypothesis, the evaluation of the physicochemical properties and blood-contacting properties was also performed on a series of uniaxially drawn polypropylene films. A decrease in the work of adhesion and the hydrophobic interaction at the surfaces was observed with increasing draw ratio, and the protein adsorption and platelet activation were effectively prevented with increasing draw ratio. This result supports our hypothesis. Therefore, it is concluded that the excellent blood-contacting properties of polypropylene surfaces can be achieved by reducing the macromolecular entanglement and the hydrophobic interaction with proteins.