PP Surface Research Articles

Surface enrichment of polypropylene-graft-poly(methyl methacrylate) on polypropylene

To overcome disadvantage of polypropylene induced by its low surface energy, poly(methyl methacrylate) was grafted onto polypropylene and entrapped into polypropylene as macromolecular surface modifier. The effects of copolymer structures, contact dies and content of modifiers on their surface enrichment were studied by attenuated total reflection infrared spectroscopy (ATR-FTIR), contact angle measurements (CDA) and scanning electron microscopy (SEM). Lower content and higher surface energy dies were in favor of the copolymer to enrich on the PP surface. PPw-g-PMMA with low PMMA graft density, long length of PMMA was distributed in PP with smaller phase domains and concentration gradient, especially at lower loadings in blends, which favored its selective enrichment on the surface of PP. The modified material exhibited excellent solvent-resistance. The results indicated that PPw-g-PMMA can transfer to the surface of blends and effectively increase the hydrophilicity of PP, which offer a convenient technique to functionalize the surface of polymers with lasting-effectiveness compared with modification by homopolymers.

Surface modified polypropylene pipette tips packed with a monolithic plug of adsorbent for high‐throughput sample preparation

UV-initiated poly(butyl methacrylate-ethylene glycol dimethacrylate) porous polymer monoliths were prepared in situ in polypropylene-based pipette tips for high-throughput sample preparation. Prior to the in situ polymerization, the surface of the PP tips was modified. In this work, two different surface modification approaches were tested for this purpose. First the photoinitiator benzophenone was used to generate radicals at the surface of PP by hydrogen abstraction. In the second modification approach, a thin layer of a polymer was directly grafted to the surface. The effect of surface modification was measured by contact angle measurements of a drop of water at the surface. As a result of the surface modification, scan electron microscopy images indicate a covalent attachment of the monolith to the wall of the pipette tip. Pipette tips modified with 5% BP in methanol and packed with a plug of monolith were further evaluated for high-throughput sample preparation. Using a liquid handling system, the extraction performance of packed pipette tips was tested for the analysis of ropivacaine in plasma samples. The recovery and reproducibility results were in accordance with internationally accepted criteria for qualitative and quantitative analysis of the test substance, ropivacaine.

Comparative study of surface free energy and surface resistivity of polypropylene and polystyrene thin films after DC plasma treatment

30 o C, pressure 200 Pa). The effects of time (up to 110 s) and power (1 W or 5 W) of the treatment on the values of free energy (γs) of PS and PP samples and γS components — dispersive (γS D ) and polar (γS P ) ones — were determined. With prolonged time of interaction the values of γS and γS P increased, especially in the region of first 35—50 s, while γS D values kept the similar level during the whole time of exposure. The dependence of PP and PS surface resistance on the same parameters as above (time and power of interaction) has been also found. For both polymers this resistance decrease with prolonged time and growing power of exposure.

Study on the application possibilities of an atmospheric pressure glow discharge with liquid electrolyte cathode for the modification of polymer materials

We investigated the action of an atmospheric pressure air glow discharge (APGD) with aqueous electrolyte cathode onto the surface of polypropylene films and grey cotton fabric. Aqueous solutions of KCl, KBr and KI were utilized as a cathode. The surface properties of PP were characterized by contact angle measurement followed by surface free energy calculation, Fourier Transform Infrared by Attenuated Total Reflectance (FT-IR/ATR) analysis and height of water capillary rise for fabric. After treating PP surface, we observed OH-groups, C=O groups in ester, ketone and carboxyl groups, C=O groups in unsaturated ketones and aldehydes. Modification processes were able to improve the wettability of fabric as well as to accomplish the immobilization of some porphyrins onto PP surface.

Surface and bulk modification of polyolefins by functional aryl nitrenes as highly reactive intermediates

Aromatic azides with hindered amine light stabilizer (HALS) residues or hydrophilic groups such as glucose, sucrose and dextrine residues were synthesized and used for surface modification of polyolefins. By UV-irradiation nitrenes were formed, which are able to react with polyolefin surfaces. By photochemical immobilization of the carbohydrates hydrophilicity of PE and PP was strongly increased (surface tensions > 44mN/m). Light stability of PP surfaces modified with HALS azides was comparable with PP, stabilised with Tinuvin 770. Bulk modification of ethylene-propylene and ethylene-octene copolymers was achieved by grafting nitrenes formed by thermal decomposition of azido benzoic acid. In a circulating air oven up to 1.55 wt% amino benzoic acid residues could be bonded covalently to ethylene-propylene-copolymers, less than half of it to ethylene-octene-copolymers. Reactive extrusion resulted in grafting yields of more than 50% for both types of copolymers.

Basic Studies on Development of Structure Hierarchy in Tubular Film Blown Dynamically Vulcanized PP/EPDM Blend

Abstract The processing characteristics and structural hierarchy development in a tubular blown, dynamically vulcanized polypropylene/ethylene—propylene—diene monomer rubber (PP/EPDM) blends were investigated. The semi-crystalline PP phase exhibited a* and c-axis orientations with the a* oriented populations dominating low draw-down ratio (DDR) conditions. At high DDR, both a* and c-axis oriented populations were observed. Little or no preferential orientation was detected in the discrete EPDM phase using dichroism studies. The blown films were found to exhibit an unusual asymmetric structure: The PP phase was found to fibrillate at the outside surface while the inner surface remained relatively featureless. This was attributed to disproportionately rapid cooling of the outside surface by the air stream blown externally onto the film being extruded. This, in turn, resulted in solidification of very thin PP surface layers that caused their fibrillation under the heavy stresses they had to endure. Increasing the blow-up ratio was found to expand this web-like surface texture. As a result of this fibrillation mechanism, the increase of both the blow-up ratio and draw-down ratio was found to reduce the mechanical properties.

Reactivity of surface groups attached on a plasma treated poly(propylene) film. Application to a new concept of a chelating membrane

The goal of the present work is the synthesis of a new chelating membrane from a trivial material, such as poly(propylene), through the fixation of the chelating groups after a cold plasma irradiation. The cold plasma treatment compared to the electron beam irradiation is less degrading since only a few layers are affected. It leads to a surface bearing two types of reactive species: radicals able to initiate a post-grafting reaction of any kind of vinyl monomer and new surface functional groups – depending on the chemical nature of the cold plasma – able to react with a chelating molecule. So the modulation of the plasma conditions and the choice of the attached chelating groups onto the material can control the chelating capacity of such irradiated material. The nitrogen plasma modification of poly(propylene) (PP) leads to a weakly cross-linked and slightly degraded surface bearing alkyl radicals and amino groups in various densities depending on plasma conditions. After the plasma irradiation, N-acryloylglycine (NAG) and diethylenetriaminepentaacetic acid (DTPA) possessing specific chelating properties are grafted successfully onto the PP surface in different ways. All the grafted films present an important selectivity towards silver ions and consequently towards soft metallic ions, too. The ion capacity of NAG grafted films remains higher than with DTPA whatever the density of amino groups attached on the surface is.

Factors affecting the UV emission from pulsed surface discharges

The emission properties of pulsed electrical discharges propagating across the surfaces of PET, PP, PTFE, UPVC, and PVDF in various gases have been investigated. The optical spectra from the discharges have been recorded over the 200-500 nm bandwidth and the effect of the interaction between the pulsed discharge and the substrate material studied. The gases used were air, argon, and SF/sub 6/ at pressures in the range 0.1-1 bar. In comparison to the other gases, SF/sub 6/ was found to produce the most intense continuum and line emission within the 200-300 nm spectral region. The substrate material was found to affect both the intensity of continuum spectra and the content of the discrete line spectra. When PTFE was employed, the continuum spectra was more intense compared to that of the other materials. In contrast, the use of PVC resulted in a considerable modification to the composition of the discrete line spectra.

Surface modification of polypropylene under argon and oxygen-RF-plasma conditions

Polypropylene fabrics samples were surface functionalized under Ar and O2 RF plasma conditions. Survey and high resolution photoelectron spectroscopy and attenuated total reflectance FTIR comparative evaluation of virgin and plasma treated substrat surfaces, and their pentafluorophenyl hydrazine-derivatized correspondents, indicate that both Ar and O2-discharge treated PP surfaces undergo intense oxidation. C=O, O−C=O, and C−O linkages were identified on both inert and reactive gas plasma exposed surfaces. It was found that the relative surface atomic concentrations and the relative ratios of newly created functionalities are controlled by the external plasma parameters (RF power and treatment time). The oxidation of Ar-plasma treated surfaces has been related toex situ post plasma mechanisms. Dynamic contact angle measurements from unmodified and plasma exposed substrates demonstrated the presence of increased surface polarity, and its dependence on plasma parameters. AFM evaluations of plasma treated samples indicate the presence of rough surface morphologies.

FTIR&ATR analyses on a polypropylene (pp) surface after plasma treatment in the study of chitosan surface grafting to improve PP dyeing behaviour

AbstractThis study consisted in working on the treatment of a polypropylene (PP) film surface to improve its dyeing behaviour. A plasma treatment was carried out to try to create oxidizing groups on this surface, so that it could be then easier to apply a specific polysaccharide: chitosan which is reported to be much more reactive than PP and easy to dye. A study about the various parameters of the plasma instrument was necessary to find the optimal treatment. The possible formed oxidizing groups were emphasized by FTIR&ATR analyses. Chitosan was applied after the plasma treatment and the dyeing result which was then observed, was quite encouraging in certain conditions.

Lateral variations in mantle velocity structure and discontinuities determined from P, PP, S, SS, and SS — SdS travel time residuals

On the basis of P, PP, S, SS arrival times and SS ‐ S410S, SS ‐ S660S differential times, we construct models of mantle P and S velocity structure and boundary topography of the 410‐km and 660‐km discontinuities. Events from the catalog of the International Seismological Centre (ISC) are relocated relative to the International Association of Seismology and Physics of the Earth's Interior 1991 (IASP91) velocity model using both P and S arrival times. The arrival times are corrected for ellipticity and the PP and SS residuals are corrected for the topography at the bounce point. The cap‐averaged PP ‐ P and SS ‐ S differential time residuals, plotted at the PP and SS surface reflection points, form broad coherent patterns. The geographic distribution of the cap averaged residuals agrees quite well with PP ‐ P and SS‐S differential time residuals derived from long period Global Digital Seismograph Network (GDSN) data. A robust lp inversion scheme is used to infer global mantle structure. Synthetic tests indicate that for regions well sampled by SS ‐ S410S and SS ‐ S660S differential times, the velocity estimates are not seriously contaminated by the topography of the 410‐ and 660‐km discontinuities. However, estimates of boundary deflections may be influenced by extensive P and S velocity variations of 3% or greater. We find the 410‐km discontinuity to be depressed by as much as 24 km beneath North America. Conversely, the discontinuity is deflected upward underneath Eurasia. In some regions the topography of the 660‐km discontinuity is quite distinct from that of the 410‐km discontinuity, but the two appear to be positively correlated. A series of depressions are found at several intersections of the 660‐km discontinuity with known subduction zones. The elevated topography in the 410‐km discontinuity beneath Europe is underlain by a trough in the 660‐km discontinuity. A number of subduction zones are characterized by a thinning of the transition zone. Negative P and S velocity anomalies, underlying back‐arc basins and tectonically active continental regions, encircle the Pacific. Where they are resolved, the stable continental cratons are systematically positive velocity features that extend below 200 km. With the inclusion of PP and SS travel time residuals we are better able to constrain midmantle structure. Most notably, in the depth range 35–660 km beneath the Northwest Pacific we observe high P velocity. Where they are resolved, mid‐ocean ridges are most clearly imaged as low velocity features in the S model. The northern portion of the Mid‐Atlantic Ridge is underlain by negative S velocity anomalies. In the Pacific, the East Pacific Rise is an extensive low S velocity anomaly.

GEOPHYSICAL RESISTIVITY IMAGE RECONSTRUCTION BY DIFFERENTIAL SENSITIVITY DISTRIBUTION METHOD

The technique of computerized image reconstruction of electrical resistance in earth has been newly developed by numerical analysis methods, such as, finite element, finite difference, resistance network, integral equation and these complex solution. In this study, a new sensitivity distribution technique is proposed to improve the reliability of resistivity interpretation, mainly, to improve the subsurface image reconstruction by not only apparent resistivity measurements but also differential electrical measurements, i.e., the extended differential sensitivity distribution methods. Special cases of CC (drillhole DH-1) PP (surface) hole-to-surface, C (hole DH-1) PP (hole DH-2) crosshole, and CC (tunnel TL-1) PP (surface) tunnel-to-surface configurations were discussed.

Polypyrrole - A Potential Candidate for Stimulated Nerve Regeneration

AbstractThe proposed research is aimed at gaining a fundamental understanding of in vitro nerve cellbiomaterials interactions, with the immediate goal of engineering materials to specifically enhance expression of the neuronal phenotype. Long term goals include (1) optimizing the innervation (connection) of the host neurons with implanted bioartificial tissue constructs and, (2) facilitating the regeneration of damaged peripheral and central nerves. In this study, the interactions of neuronal like PC-I12 cells with the electrically conducting polymer, polypyrrole, (PP) have been investigated. It has been shown by quantitative image analysis that neurite extensions of PC-12 cells are more pronounced on PP surfaces as compared to tissue culture polystyrene. Application of an electrical stimulus to cells cultured on PP film significantly increased (based on morphological evaluation) the expression of neurites in these cells compared to controls. Tissue compatibility and transected sciatic nerve regeneration studies in rat models show that PP films invoke little negative response and support nerve regeneration.

Thermally-stimulated current and dielectric loss measurement of polypropylene and Teflon-FEP films immersed in diarylethane

Some properties of oil/PP (biaxially stretched polypropylene) and oil/FEP (Teflon FEP) composite insulators have been investigated with TSC (thermally stimulated current) techniques. The oil/PP system showed three TSC peaks originating from carriers captured in the swollen surface region of the PP. The TSC spectra depended strongly on the polarity of the poling voltage and on the impregnating temperature. Their analysis yielded information on the carrier traps existing near the PP surface in the oil/PP interface region. On the other hand, the TSC spectrum of the oil/FEP system has a small impregnating temperature dependence and a small effect of the poling voltage polarity. The difference in TSC between oil/PP and oil/FEP systems is closely related to the difference in the oil-polymer interaction. The TSC is a useful method for investigating carrier traps in the surface region and their change due to the oil-polymer interaction. To investigate further the relation between the carrier traps and tan/spl delta/, collecting bias TSC was measured on a specimen to which an ac voltage was applied. The results indicate that the decrease in tan/spl delta/ during the ac voltage application depends on the amount of trapped carriers near the polymer's surface or, the decrease in carriers in the oil. >

Immobilization of Surface Active Compounds on Polymer Supports Using Glow Discharge Processes: 1. Sodium Dodecyl Sulfate on Poly(propylene)

A new method has been developed in which a reversibly adsorbed layer of a surfactant (sodium dodecyl sulfate, SDS) is covalently immobilized in one step onto a hydrophobic substrate (poly(propylene), PP) by applying an argon plasma treatment. The adsorption of SDS from aqueous solutions onto PP surfaces was studied with X-ray photoelectron spectroscopy (XPS). Plateau levels of adsorbed SDS were reached within 10 s using SDS solution concentrations above the critical micelle concentration (CMC). At SDS concentrations below the CMC almost no adsorption took place, whereas at SDS concentrations above the CMC constant adsorption levels were measured. Preadsorbed SDS layers could be completely desorbed after immersion of the SDS-coated substrates in water for 90 min. If PP surfaces with preadsorbed SDS were dried and plasma-treated with an argon glow discharge and then immersed in water for 90 min, intact sulfate groups were present at the surface as shown by ion exchange and XPS measurements. This indicates that SDS preadsorbed onto PP surfaces can be immobilized by a plasma treatment. It is concluded that plasma techniques can be used to immobilize physically adsorbed surface active compounds onto substrates. This is a useful way to derivatize inert substrates with various polar or nonpolar groups.

On oxygen plasma‐treated polypropylene interfaces with air, water, and epoxy resins. II. Epoxy resins

AbstractXPS, SEM, SSIMS, FTIR‐ATR, water‐in‐air, and air‐in‐water contact angle measurements have been used to unambiguously characterize the locus of failure of PP/epoxy joints. In the case of untreated PP, the fracture has been found adhesive, whereas in oxygen plasmatreated PP, it is cohesive, within bulk PP, but close to the modified PP‐bulk PP interface. The smoothness of fracture surfaces allowed us to exclude mechanical interlocking effects. Shear‐strength measurements showed that the mechanical strength of the joint was improved by plasma treatment. Preliminary thermal equilibration of the plasma‐treated PP sample and changes in the curing cycle of the epoxy resin did not change either the locus of failure or the shear strength of the joint. The reason is probably because the number of polar functions left at the surface after thermal equilibration is sufficient to induce adhesion. The mechanical strength of the PP surface layer may be the determining factor. Fracture energy calculations showed that the observed locus of failure is the same as predicted on the basis of surface energy considerations.

Structural-chemical transformations in polymers subjected to the effects of a gas discharge

IR spectroscopic methods have been used to study structural-chemical transformations in the surface of PETP and PP under the effect of a gas discharge. It is shown that the improvement in wetability is caused, in the first instance, by a structural-conformational rearrangement of the molecules in the surface layer under the action of high-energy particles.

Surface electronic bands of GaAs(1 1 0)-Sb: An angular resolved photoemission study

Sb deposited in monolayer coverage at 300 K on cleaved GaAs(1 1 0) surfaces forms a well ordered overlayer with a p(1 × 1) LEED pattern. The two dimensional (2 D) surface electronic band structure of this overlayer system is studied by angular resolved UV photoemission spectroscopy (ARUPS) along the Γ X and Γ X symmetry lines of the pp(1 × 1) surface Brillouin zone. Four surface state bands in the energy range down to 5 eV below the upper valence band edge are resolved. A comparison with available theoretical band structure calculations yields satisfactory agreement.

Morphological study of the wear of crystalline polymers II: Isotactic poly(propylene)

The morphology of the worn surface and wear debris of isotactic poly(propylene) (PP) slid against steel in air and water was studied. From electron micrographs, electron diffraction patterns and X-ray diffraction patterns it was found that both the worn surface and the wear debris had a smectic structure. Plastic deformation of the surface of PP took place during frictional contact both in air and in water, giving rise to the formation of thick meandered fibrous aggregates with their longitudinal axes nearly perpendicular to the sliding direction and thin fibrils aligned parallel to the sliding direction.