Surface changes of corona‐discharge‐treated polyethylene films

Morphological and chemical changes of the surface of low‐density polyethylene (LDPE), linear middle‐density polyethylene (L‐MDPE), and their 80/20 blend were studied by different techniques after corona‐discharge treatment in air and subsequent annealing. The surface tension was determined by wetting; the roughness was measured by atomic force microscope (AFM), and the surface chemical composition was analyzed by X‐ray photoelectron spectroscopy (XPS), whereas the low‐molecular‐mass fraction washed off by chloroform by FTIR. The surface tension of the films increases with the electrode current. The surface roughness depends primarily on the polymer type and is less affected by the corona treatment. At the initial stage of annealing, posttreatment‐type oxidation and hydrophobic recovery are competing. The former is more pronounced in L‐MDPE, the latter in LDPE. After annealing at 50°C for 160 days, hydrophobic recovery becomes predominant in each film studied, which is accompanied by significant smoothening of the surface. According to XPS and FTIR results, this is due to the migration of low‐molecular‐mass components (oligomers, oxidized polymer fractions, and additives) to the surface. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 76: 1529–1541, 2000     

Argon low‐temperature plasma modification of chopped aramid fiber and its effect on paper performance of aramid sheets

Chopped aramid fiber was modified by an argon low‐temperature plasma treatment to enhance the interfacial strength of aramid paper. The water contact angle of the aramid fiber and the tensile strength, tearing strength, and evenness of the aramid sheets were investigated under different conditions, and the parameters of the argon low‐temperature plasma modification, like gas pressure, discharge power, and discharge time, were optimized. The chemical structure and surface morphology of the fiber after plasma modification were characterized by X‐ray photoelectron spectroscopy, atomic force microscopy, and scanning electron microscopy. The strengthening mechanism of aramid paper by low‐temperature plasma modification was also studied. It was found that the argon low‐temperature plasma treatment introduced some new polar groups onto the fiber surface and increased the fiber surface wettability and roughness. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45215.     

Controlling the morphology of polyurethane/polystyrene interpenetrating polymer networks for enhanced blood compatibility

Polyurethane (PU)/polystyrene (PS) IPNs were simultaneously synthesized at 80°C, controlling the reaction kinetics to change the morphology. Polymerization kinetics of styrene was controlled by the content of initiator, and that of polyurethane by the catalyst concentration. The effect of the initiator and the catalyst on the polymerization rate was analyzed by NMR spectroscopy and FTIR. Gelation time was also measured by using the advanced rheometric expansion system (ARES). Samples with sea‐and‐island morphology were obtained, when the polymerization rate of PS was relatively slow, and the phase separation time was long. When the polymerization rate of PS was relatively fast, and the phase separation time was short, cocontinuous morphology was obtained. The degree of phase separation and surface roughness decreased, as the rate of PU network formation was increased, and the phase‐continuity was increased. The in vitro blood‐compatibility tests showed that the surface roughness was an important factor on the adsorption of fibrinogens and platelets. A large amount of fibrinogens and platelets were adsorbed on the relatively rough surface of samples showing sea‐island morphology. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 379–387, 2002; DOI 10.1002/app.10358     

Simple route for the preparation of graphene/poly(styrene‐b‐butadiene‐b‐styrene) nanocomposite films with enhanced electrical conductivity and hydrophobicity

This paper reports a simple route for the preparation of graphene/poly(styrene‐b‐butadiene‐b‐styrene) (SBS) nanocomposite films employing a vacuum filtration method. Graphene is exfoliated well by an electrochemical procedure and homogeneously dispersed in the polymer matrix. The prepared nanocomposite films were characterized by XRD, Fourier transform IR (FTIR) spectroscopy, X‐ray photoelectron spectroscopy (XPS), Raman spectroscopy, AFM and SEM. Morphological studies showed that graphene formed a smooth coating over the surface of SBS. The increase in graphene concentration induces the wrinkling of graphene sheets at the composite surface which causes a further increase in surface roughness. The FTIR, Raman and XPS spectra of graphene/SBS nanocomposite films indicate the strong interactions between graphene and the polymer matrix. According to the XRD patterns, introducing SBS into graphene did not modify the graphene structure additionally, i.e. the crystal lattice parameters do not depend on SBS content in graphene/SBS nanocomposite films. The graphene/SBS nanocomposite films also exhibited better hydrophobicity due to the increased surface roughness and lower sheet resistivity (reduced 10 times) compared to exfoliated graphene. © 2018 Society of Chemical Industry     

Swelling,compression and tribological behaviors of bentonite‐modified polyacrylate‐type hydrogels

Hydrogel was synthesized from acrylamide and 2‐acryloylamido‐2‐methylpropanesulfonic acid monomers (ratio: 50/50 wt %) and crosslinked with 0.25 wt % of methylene‐bisacrylamide. This hydrogel was also modified by adding 4 wt % of sodium bentonite (NB). Selected properties of the hydrogels with and without NB were investigated and compared. Their water uptake was measured gravimetrically; the compression and compression creep were assessed by dynamic‐mechanical and thermo‐mechanical analysis (DMA and TMA, respectively) techniques. The friction and wear of the hydrogels were determined in a shaft(metal)‐on‐plate(hydrogel) type testing configuration under water lubrication. The hydrogel was transparent and exhibited very high equilibrium water content (>99 wt %). The latter was less affected; however, the hydrogel became slightly more hazy after NB incorporation. The crosslink density of the hydrogels was deduced from swelling and compression tests and compared with the theoretical values. Modification by NB enhanced the ultimate compression strength and reduced the related compression strain. The compression creep response under both loading and deloading strongly depended on the level of the initial load. A very low friction coefficient (～ 0.003) and a relatively high specific wear rate (～ 0.05 mm³/N m) were registered under water lubricated sliding wear using a metallic counterpart with high surface roughness. Scanning electron microscopy combined with energy dispersive spectroscopy delivered additional information on the NB dispersion and surface structure of the hydrogels. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Effect of surface roughness and reciprocating time on the tribological properties of the polyimide composites

Novel polyimide (PI) composites were designed and prepared as a frictional material for ultrasonic motors (USM). The effect of roughness and reciprocating time on the tribological properties of PI composites was specially investigated for simulating USM operating condition. These typical PI composites were designed along with the special characteristics of USM by filling proportional solid lubricants and nanoparticles, and prepared using classical hot‐press sintering. The friction and wear behavior of PI composites with different surface roughness polished by SiC sandpaper and various reciprocating time was carried out on a pin‐on‐plate tribo‐meter against GCr15 steel pin. The worn surface was observed by SEM to reveal wear mechanisms. Experimental results indicated that the coefficient of friction and specific wear rate increased with an increase of surface roughness which was detrimental for USM to prolong the service life. The coefficient of friction and wear volume will increase with an increase of reciprocating time due to fatigue wear, but specific wear rate will decrease with the minimum value of 2.1 × 10^?6 mm³/N m. This study can provide significant guidance for USM to optimize frictional surface and running‐in time. POLYM. ENG. SCI., 59:483–489, 2019. © 2018 Society of Plastics Engineers     

蛇纹石对不同粗糙度45~#钢表面的减摩行为

利用MMW-1A型万能摩擦磨损试验机研究蛇纹石对3种不同粗糙度45#钢表面的减摩行为。采用三维视频显微镜、扫描电子显微镜和能谱仪对实验前后磨损表面形貌和化学组成进行分析。结果表明：蛇纹石的减摩效果对于光滑磨损表面更为显著。当表面粗糙度Ra=0.742μm时,磨损表面被有效修复,摩擦系数大幅下降,表面粗糙度下降了72.1%,并且磨损量仅有1.3mg;当Ra=1.424μm和3.706μm时,摩擦副磨损遵循一般金属材料的磨损特征。修复层平整光滑,其形成与磨损存在一个动态平衡。     

Flame‐retardant mechanism of silica: Effects of resin molecular weight

The effects of resin molecular weight on the flame‐retardant mechanism of silica were studied with two different molecular weights of poly(methyl methacrylate) (PMMA), 122,000 and 996,000 g/mol, and two silicas, fused silica with a small surface area and silica gel with a large surface area. A total of six different samples were studied, with a mass fraction of 10% silica. The mass loss rate of the six samples in nitrogen and the heat release rate from burning in air were measured at an external radiant flux of 40 kW/m². The addition of silica gel to the low‐molecular‐weight PMMA significantly reduced the mass loss rate and heat release rate; addition to the high‐molecular‐weight PMMA provided the largest reductions of these quantities in this study. For fused silica, some reduction in mass loss rate and heat release rate was observed when it was added to the high‐molecular‐weight PMMA; addition to the low‐molecular‐weight PMMA did not reduce either loss rate. Chemical analysis of the collected residues and observation of the sample surface during gasification reveal the accumulation of silica near the surface; the larger its coverage over the sample surface was, less the mass loss rate and heat release rate were. Both the level of accumulation and its surface coverage depended strongly not only on the silica characteristics but also on the melt viscosity of the PMMA. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 1541–1553, 2003     

Characterization of shear stress at the tool‐part interface during autoclave processing of prepreg composites

In this article, shear stress between an aluminum tool and a carbon fiber‐epoxy prepreg is characterized during cure using polymeric release agent and release film at the tool‐part interface. The effects of surface roughness, release materials, pull‐out speed, temperature, and normal force (autoclave pressure) on the shear stress are investigated using a customized friction rig. Results show that the interfacial shear stress decreases as the temperature increases and it increases as the normal force increases when using either the release film or the release agent. Additionally, changes in surface roughness from 1.35 to 0.18 μm decrease the shear stress 10–27% while the use of release agent shows a decrease between 23% and 51% in the shear stress. Furthermore, strong adhesion between the tool and the part is observed when using release agent and pull‐out speeds of 0.05 mm/min (static/dynamic friction ratio of 5.29 ± 0.19). Using the experimental data, a mathematical approach based on the Coulomb's friction model is proposed to predict the friction force at the tool‐part interface. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Reduction of surface friction of natural rubber film coated with PMMA particle: Effect of particle size

The friction coefficient of the sulphur‐prevulcanized natural rubber (SPNR) film could be effectively reduced by deposition of poly(methyl methacrylate) (PMMA) particles. The nanoscale surface roughness of rubber, determined by atomic force microscope, was directly proportional to the particle size of PMMA particle at 12% surface coverage (Cs). The %Cs and surface roughness of the modified SPNR increased, while the friction coefficient decreased, with increasing PMMA latex concentration and immersion time. By using a mixture of latexes having both large and small sizes, the increase in the amount of small particles resulted in the better distribution of large particles deposited on the rubber surface. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Surface roughness and foam morphology of cellulose acetate sheets foamed with 1,3,3,3‐tetrafluoropropene

Cellulose acetate (CA) is a bio‐based polymer suitable to replace foamed polystyrene (PS) in packaging applications. Foam trays can be produced by thermoforming of extruded sheets foamed with physical blowing agents. In this paper, the effects of various process settings and the calibration of the sheet on foam morphology and surface quality of extruded CA sheets are presented. Different contact cooling options were applied in order to investigate their influence on surface roughness, density, and morphology of the sheets. By adjusting cooling parameters, blowing agent formulation, and process settings, smooth foam sheets with a surface roughness below 10 µm and a density in the range of 150 kg m^?3 were produced. POLYM. ENG. SCI., 57:441–449, 2017. © 2016 Society of Plastics Engineers     

Synthesis and characterization of nonionic 1‐vinyl‐2‐pyrrolidinone/methacryloxy silicone copolymers: Effects of molecular weight of silicone and crosslinking density

Nonionic 1‐vinyl‐2‐pyrrolidinone/methacryloxy silicone copolymers (VP/VS copolymers) were prepared and characterized as functions of molecular weight of silicone and crosslinking density. Fourier transform infrared spectroscopy, ¹³C‐NMR, and pyrolysis gas chromatography–mass spectrometry study showed that those copolymers were successfully synthesized. Also, the gel‐permeation chromatography spectrum exhibited a fairly narrow distribution of the molecular weight of the polymer. It was found that the turbidity in ethanol (EtOH) and the glass‐transition temperature of crosslinked VP/VS copolymers are influenced by the amount of crosslinking agent. However, in the case of branched VP/VS copolymers, a transparent solution was obtained, regardless of the molecular weight of silicone. SEM/EDS study revealed that silicone is more abundant on the coating surface than on the interface of coating/glass. This is probably because Si‐containing chains have lower surface energy than that of vinylpyrrolidinone‐containing chains. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 2244–2253, 2002     

Investigation on the Friction Sensitivity of a Matchhead Composition Influenced by the Surface Roughness of Contact Materials

Fire and explosions in the processing of matchhead compositions are reported due to the friction sensitivity of materials used. This investigation is aimed at investigating the influence of different types of contact materials and their surface roughness on the friction sensitivity of a matchhead composition. The friction sensitivity of the matchhead composition was found to be dependent on the contact materials and their roughness. The results demonstrated that the contact materials and their surface roughness imparted variations to the sensitivity, ranging from 108 to 360 N. The sensitivity response of the energetic mixture was quicker in case of aluminum plate‐aluminum pin combinations than those when steel plate‐steel pin and brass plate‐brass pin combinations were used. For the first time, the experimental investigation identified a new value based on the material’s surface roughnesses called critical surface roughness, at which the matchhead composition ignited at a minimum frictional load. The matchhead composition was found to be highly hazardous at the critical surface roughness values of 1.09, 1.01, and 1.05 μm for aluminum, brass, and steel surfaces, respectively. Based on the experimental results this paper also discusses mechanism of ignition caused by the frictional load.     

Tailoring surface properties of cellulose acetate membranes by low‐pressure plasma processing

The aim of this study was to tailor the surface properties of cellulose acetate membranes using low‐pressure plasma processing. Argon (Ar) plasma and Difluoromethane (CH₂F₂) plasma were used to control the surface wettabilities of cellulose acetate membranes. Optical emission spectroscopy was used to examine the various chemical species of low‐pressure plasma processing. In this investigation, the plasma‐treated surfaces were analyzed by X‐ray photoelectron spectroscopy, while changes in morphology and surface roughness were determined with confocal laser scanning microscopy. Ar plasma activation resulted in hydrophilic surface. CH₂F₂ plasma deposited hydrophobic layer onto the cellulose acetate membrane because of strong fluorination of the top layer. The results reveal low‐pressure plasma processing is an effective method to control the surface properties of cellulose acetate membranes. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Mechanism and Simulation of Removal Rate and Surface Roughness During Optical Polishing of Glasses

Glass optics with ultra‐low roughness surfaces (<2 Å rms) are strongly desired for high‐end optical applications (e.g., lasers, spectroscopy, etc.). The complex microscopic interactions that occur between slurry particles and the glass workpiece during optical polishing ultimately determine the removal rate and resulting surface roughness of the workpiece. In this study, a comprehensive set of 100 mm diameter glass samples (fused silica, phosphate, and borosilicate) were polished using various slurry particle size distributions (PSD), slurry concentrations, and pad treatments. The removal rate and surface roughness of the glasses were characterized using white light interferometry and atomic force microscopy. The material removal mechanism for a given slurry particle is proposed to occur via nano‐plastic deformation (plastic removal) or via chemical reaction (molecular removal) depending on the slurry particle load on the glass surface. Using an expanded Hertzian contact model, called the Ensemble Hertzian Multi‐gap (EHMG) model, a platform has been developed to understand the microscopic interface interactions and to predict trends of the removal rate and surface roughness for a variety of polishing parameters. The EHMG model is based on multiple Hertzian contacts of slurry particles at the workpiece–pad interface in which the pad deflection and the effective interface gap at each pad asperity height are determined. Using this, the interface contact area and each particle's penetration, load, and contact zone are determined which are used to calculate the material removal rate and simulate the surface roughness. Each of the key polishing variables investigated is shown to affect the material removal rate, whose changes are dominated by very different microscopic interactions. Slurry PSD impacts the load per particle distribution and the fraction of particles removing material by plastic removal. The slurry concentration impacts the areal number density of particles and fraction of load on particles versus pad. The pad topography impacts the fraction of pad area making contact with the workpiece. The glass composition predominantly impacts the depth of plastic removal. Also, the results show that the dominant factor controlling surface roughness is the slurry PSD followed by the glass material's removal function and the pad topography. The model compares well with the experimental data over a variety of polishing conditions for both removal rate and roughness and can be extended to provide insights and strategies to develop practical, economic processes for obtaining ultra‐low roughness surfaces while simultaneously maintaining high material removal rates.     

Optical properties of high‐density polyethylene in injection press molding for IR system lenses

An experimental investigation of injection press molding (IPM) was conducted to assess high infrared radiation (IR) transmittance with an opaque state (low‐visibility ray (VR) transmittance) necessary for IR system lenses as a target high‐density polyethylene (HDPE) IR transmission material. The changed conditions were the cavity open distance and delay time considering the polymer melt flowability. Other molding conditions were held constant. Mold surface roughnesses of two kinds were used. Data for IR and VR transmittance were evaluated using measurements or observation results obtained for surface roughness, thickness, differential scanning calorimetry (DSC), crystallinity, and the internal structure. Results show that the surface roughness and thickness of molded parts did not influence IR or VR transmittance. For thin skin layers with low orientation of molecular chains, the IR transmittance was higher for longer delay times. For low molecular chain orientation in the shear–core layer, the VR transmittance was also low. The molecular chain orientation differed depending on IPM conditions. Setting a longer delay time produced a uniform distribution of the molded part thickness. Furthermore, thickness became a constant value when a mold with high surface roughness was used. POLYM. ENG. SCI., 2017. © 2017 Society of Plastics Engineers     

Effects of functional groups and surface roughness on interfacial shear strength in ultrahigh molecular weight polyethylene fiber/polyethylene system

Corona discharge treatment was conducted for ultrahigh molecular weight polyethylene (UHMWPE) fiber. The functional groups and surface roughness of the polyethylene fiber surface were determined by an X‐ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM). The interfacial shear strength of UHMWPE fiber with HDPE film was determined by microbond pullout method. The interfacial shear strength increased by corona treatment. Then, the effect of the chemical and physical factors on the interfacial shear strength was discussed based on the results of multivariate regression analysis. The results indicated that the contribution of functional groups and surface roughness to the interfacial shear strength was expressed as 50 and 50%, respectively. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 71: 243–249, 1999     

Tribological properties of SiO2 nanoparticle filled–phthalazine ether sulfone/phthalazine ether ketone (50/50 mol %) copolymer composites

SiO₂ nanoparticle filled–poly(phthalazine ether sulfone ketone) (PPESK) composites with various filler volume fractions were made by heating compression molding. The tribological behavior of the PPESK composites was investigated using a block‐on‐ring test rig by sliding PPESK‐based composite blocks against a mild carbon steel ring. The morphologies of the worn composite surfaces, wear debris, and the transferred films formed on the counterpart steel surface were examined with a scanning electron microscope, whereas the chemical state of the Fe element in the transfer film was analyzed with X‐ray photoelectron spectroscopy. In addition, IR spectra were taken to characterize the structure of wear debris and PPESK composites. It was found that SiO₂ nanoparticle filled–PPESK composites exhibit good wear resistance and friction‐reduction behavior. The friction and wear behavior of the composites was improved at a volume fraction between 4.2 and 14.5 vol % of the filler SiO₂. The results based on combined SEM, XPS, and IR techniques indicate that SiO₂ nanoparticle filled–PPESK composite is characterized by slight scuffing in dry sliding against steel and polishing action between composite surface and that of the countpart ring, whereas unfilled PPESK is characterized by severe plastic deformation and adhesion wear. In the former case a thin, but not complete, transfer film was formed on the surface of the counterpart steel, whereas in the latter case, a thick and lumpy transfer film was formed on the counterpart steel surface. This accounts for the different friction and wear behavior of unfilled PPESK and SiO₂ nanoparticle filled–PPESK composites. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 2136–2144, 2002     

The surface modification of medical polyurethane to improve the hydrophilicity and lubricity: The effect of pretreatment

The medical polyurethane (PU) film was grafted with poly(acrylic acid) (PAA) to improve the hydrophilic and lubricious properties. The influences of pretreatment by ozone or potassium peroxydisulfate on themorphologies of PU films and grafting results were systematically investigated. The grafted PU films were characterized using attenuated total reflection Fourier transformed infrared spectroscopy (ATR‐FTIR), scanning electron microscopy (SEM), atomic force microscopy (AFM) and gel permeation chromatography (GPC). The hydrophilic and lubricious properties were evaluated by water contact angle and friction coefficient, respectively. The results showed that PAA could be grafted firmly on PU activated by both ozone and potassium peroxydisulfate, and the PAA‐grafted PU showed good hydrophilic and lubricious performance. More importantly, the PAA‐grafted PU films with the pretreatment of ozone were better in surface roughness, hydrophilicty and lubricity, compared to those with the pretreatment of potassium peroxydisulfate. Hence, surface ozonation could be a better choice for the pretreatment of medical polymer. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Effect of current density and polytetrafluoroethylene on the properties of micro-arc oxide coating of pure aluminum

Micro-arc oxidation (MAO) is a surface treatment technology that enhances the surface properties of valves by creating a ceramic oxide layer on the metal surface. The goal of this study is to investigate the influence of current density on the properties of aluminum coatings during preparation and to improve the tribological properties of MAO/PTFE self-lubricating films on the coating surface. The characterization of the coating was performed using X-ray photoelectron spectroscopy, X-ray diffraction, Raman spectra, and energy dispersive spectroscopy. The roughness, hardness, and elastic modulus of the coatings were tested using atomic force microscopy and nanoindentation. Tribological experiments were conducted to evaluate the tribological properties of the coatings. The experimental results show that the friction coefficient (COF), roughness, hardness, and elastic modulus of the MAO coating increase with the increase of current density. Additionally, the friction coefficient of the MAO composite coating significantly decreases after the addition of polytetrafluoroethylene (PTFE), improving the service life and application range of the metal coating. These findings are expected to promote the development of valve metal in various application fields.