Surface segregation of polyethylene in low‐density polyethylene/ethylene–propylene–diene rubber blends: Aspects of component structure

Aspects of the molecular weight and its distribution, the branching of low‐density polyethylene (LDPE), and the molecular composition of the ethylene–propylene–diene rubber (EPDM) matrix are presented in this article in terms of their influence on the surface segregation of polyethylene (PE) in elastomer/plastomer blends. All of the PEs studied, despite different weight‐average molecular weights and degrees of branching, segregated to the surface of the LDPE/EPDM blends. Atomic force microscopy pictures demonstrated defective crystalline structures on the surface of the blends, which together with a decrease in the degrees of their bulk crystallinity and a simultaneous increase in their melting temperatures, pointed to a low molecular weight and a defective fraction of PE taking part in the surface segregation. The extent of segregation depended on the molecular structure of the EPDM matrix, which determined the miscibility of the components on a segmental level. The higher the ethylene monomer content in EPDM was, the lower was the PE content in the surface layer of the blends. The composition and structure of the surface layer was responsible for its lower hardness in comparison with the bulk of the blends studied. The surface gradient of the mechanical properties depended on the physicochemical characteristics of the components and the blend composition, which created the possibility of tailoring the LDPE/EPDM blends to dedicated applications. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 625–633, 2006     

Optimization of the electron‐beam‐lithography parameters for the moth‐eye effects of an antireflection matrix structure

In this study, we mainly used the characteristics of electron‐beam lithography in measurement control and direct‐write technology to improve the physical restrictions and production processes of optical lithography and other nanopattern production methods. We did this by using a silicon wafer as a substrate, coating a negative‐tone photoresist, and using scattering and the reflection produced by the collision of an electron beam with the wafer lattice and the proximity effect of a secondary electron inside the electron‐beam photoresist to produce an antireflection matrix structure with a moth‐eye effect. In addition, we used the Taguchi quality method with an orthogonal array to plan the experiment and the signal‐to‐noise ratio to analyze the experimental data, and in the experimental process, we produced a full factorial equivalent experiment, using very few experiment repetitions and deriving optimum conditions. Also, we used back‐propagation neural networks to fine‐tune significant factors, allowing the production of the deepest process control parameters and thereby imparting to the antireflection matrix structure the best effect. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 5303–5313, 2006     

Effect of different film preparation procedures on the thermal,morphological and mechanical properties of pure and calcite‐filled HDPE films

The effect of different film preparation procedures on the thermal, morphological and mechanical properties of high density polyethylene (HDPE) films have been studied using differential scanning calorimetry (DSC), wide angle X‐ray diffraction (WAXRD), atomic force microscopy (AFM), scanning electron microscopy (SEM) and ultimate tensile testing. Film preparation procedures included variation in cooling methods, including quenching, forces (fanning) and natural cooling and techniques such as extrusion followed by melt squeezing and compression molding. The heat of fusion (from DSC), the degree of crystallinity (from WAXRD) and the crystallite size (from WAXRD and AFM) were found to be highest for naturally cooled specimens, followed by fan‐cooled and quenched ones. AFM images of surface topology exhibit stacked lamellar morphology for forcefully cooled (fan‐cooled and quenched) samples and spherulitic ‘lozenges’ for naturally cooled ones. The Young's modulus and yield stress [from the universal testing machine (UTM)] were highest for naturally cooled samples, followed by fan‐cooled and quenched ones. Among the calcite‐filled composites, the ‘base film,’ which was prepared by extrusion followed by melt squeezing and natural cooling, exhibited the lowest heat of fusion and degree of crystallinity and a similar crystallite size relative to compression‐molded films. Lower yield stress, tensile strength and Young's modulus and higher elongation at break were observed for the base film in comparison to the naturally cooled composite film. The low degree of crystallinity and crystallite size in the ‘base film’ explain all of its mechanical and morphological properties. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 1427–1434, 2004     

Surface migration of carboxylic acid in styrene–butadiene rubber and its tribological consequences

Surface migration of the carboxylic acids (C₁₀H₂₁COOH, C₁₁H₂₃COOH, C₁₂H₂₅COOH, C₁₅H₃₁COOH, C₁₆H₃₃COOH, and C₁₇H₃₅COOH) in styrene–butadiene rubber (SBR) matrix was investigated together with its influence on tribological properties of the vulcanisates. Macro‐ and microtribological properties were correlated with properties that come from carboxylic acid addition to the samples. A plastifying effect was characterized by a decrease of the rubber glass transition temperature measured by the DSC method. Thickness of an acid bloom was directly determined from an indentation experiment and estimated from the DSC curve as well as from FTIR reflection spectra. Morphology of the bloom was studied using an AFM technique to characterize topography as well as microroughness of the bloom surface. Macrofriction was studied using block‐on‐ring tribometer. Microfriction was examined with a Nano Test apparatus, applying ball‐on‐plate contact. Despite correlation found between plastification, morphology, and bloom thickness on the one hand, and tribologic properties of the rubber on the other hand, influence of the chain length of carboxylic acids on properties of the samples still needs further qualitative investigation. Tribological properties of SBR modified with carboxylic acids are the result of balance of two opposite effects: plastification of rubber—leading to an increase of friction and lubrication—which causes a decrease of friction of the rubber. Apart from plastifying and lubrication effects microroughness also plays an important role in friction. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 3368–3376, 2002     

Nano‐/Microscale Investigation of Tribological and Mechanical Properties of Epoxy/MWNT Nanocomposites

The effects of MWNT content and aspect ratio on the properties of epoxy‐based nanocomposites are investigated using nanoindentation and nanoscratch methods. The Halpin‐Tsai model for predicting the elastic modulus and hardness is modified to include the effective aspect ratio factor. The modified model predicts the experimental results more accurately. The frictional behavior is investigated and a new equation is proposed that correlates the ploughing friction with the plasticity index. The dispersion state of MWNTs and the surface features of residual grooves are investigated using scanning electron micrographs and AFM profiles. The mechanisms of improvements in the properties are also discussed.

     

Synthesis,structure, and properties of new methacrylic derivatives of naphthalene‐2,3‐diol

The synthesis of a new monomer, 2,3‐(2‐hydroxy‐3‐methacryloyloxypropoxy)naphthalene, and its copolymerization with divinylbenzene is presented. This monomer was obtained from naphthalene‐2,3‐diol in a two‐step synthesis. Copolymers in the form of porous microspheres were prepared by a suspension‐emulsion polymerization method. As pore‐forming diluents, toluene, 1‐decanol, benzyl alcohol, and their mixtures were used. In studies of their porous structure, two methods were used: the adsorption of nitrogen at low temperatures, which provided information about the porous structure of the material in a dry state, and inverse exclusion chromatography, which provided information about the porous structure of the polymer swollen by a good solvent. The obtained results suggest that the porous structures for the dry and swollen polymers were different. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 1886–1895, 2006     

Studies on the electrostatic self‐assembly of polyelectrolytes and organic dyes with atomic force microscopy

An ultrathin film was formed by the electrostatic self‐assembly of polyelectrolyte poly‐N‐ethyl‐N,N‐dimethyaminoethyl methacrylate (PDMAEB) and the organic dye metanil yellow (MY) on a smooth glass sheet. An atomic force microscope was used to study the topography and the phase of the two samples and the ultrathin film (PDMAEB–MY). The dynamic course of the surface structure was researched by atomic force microscopy also. It is illustrated that the existence of electrostatic interactions between PDMAEB and MY made MY arrange in order on the polyelectrolyte surface. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 1029–1033, 2003     

Phase structural analyses of polyethylene extrusion coatings on high‐density papers. I. Monoclinic crystallinity

In the present work the morphology of high‐density polyethylene (HDPE) extrusion coating layer on high‐density paper (HDP) has been investigated. An uneven layer with a high content of crystallinity against the paper surface was discovered. The methods applied were solid‐state ¹³C NMR Spectroscopy and Atomic Force Microscopy. The highly crystalline layer was found to be mainly monoclinic crystallinity. The formation of the monoclinic crystallites was probably initiated by orientation of the polyethylene molecules by drawing, adhesion to the fibrous paper surface, and pressure. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 218–225, 2004     

The role of interfacial interactions on the crystallinity and nanomechanical properties of clay–polymer nanocomposites: A molecular dynamics study

Polymer clay nanocomposites (PCN) show enhanced mechanical, thermal, liquid or gas barrier properties in comparison to pure polymer. However, the mechanisms for enhancement of these physical properties of PCN are not well understood. This knowledge is important for tailoring the properties of PCN to desired specifications. Our earlier study showed that organic modifiers have significant influence on the crystallinity and nanomechanical properties of PCN. For quantitative evaluation of the influence of organic modifiers on the crystallinity and nanomechanical properties of PCN, molecular models of three intercalated PCNs containing same polymer and clay but with three different organic modifiers are constructed in this work. Using molecular dynamics simulations, the interaction energies among the different constituents of PCNs are evaluated. This study reveals that the interactions between polymer, organic modifiers, and intercalated clay are critical factors in controlling the crystallinity and enhancement of nanomechanical properties of PCN. We have described the possible mechanisms leading to change in crystallinity and nanomechanical properties. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Surfactant interactions with P(AM–AA–BPAM) hydrophobically modified polyelectrolytes

The interactions of hydrophobically modified polyelectrolytes poly(acrylamide–sodium acrylic acid–N‐(4‐butyl)phenylacrylamide [P(AM‐AA‐BPAM)] with anionic (sodium dodecyl sulfate), cationic (cetyl trimethylammonium bromide), and nonionic (tetradecyldimethyl‐aminoxid) surfactants were studied via solution rheology, surface tension, and atomic force microscopy measurements. Viscosity measurements indicated that the intermolecular association of the polymer was greatly enhanced by the interaction with the surfactants, especially the oppositely charged surfactants with both a hydrophobic association and an electrostatic attraction. The greatest viscosity increase was realized with the addition of such oppositely charged surfactants. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 2664–2671, 2003     

Organic‐acid‐catalyzed sol–gel route for preparing poly(methyl methacrylate)–silica hybrid materials

In this study, a series of organic–inorganic hybrid sol–gel materials consisting of a poly(methyl methacrylate) (PMMA) matrix and dispersed silica (SiO₂) particles were successfully prepared through an organic‐acid‐catalyzed sol–gel route with N‐methyl‐2‐pyrrolidone as the mixing solvent. The as‐synthesized PMMA–SiO₂ nanocomposites were subsequently characterized with Fourier transform infrared spectroscopy and transmission electron microscopy. The solid phase of organic camphor sulfonic acid was employed to catalyze the hydrolysis and condensation (i.e., sol–gel reactions) of tetraethyl orthosilicate in the PMMA matrix. The formation of the hybrid membranes was beneficial for the physical properties at low SiO₂ loadings, especially for enhanced mechanical strength and gas barrier properties, in comparison with the neat PMMA. The effects of material composition on the thermal stability, thermal conductivity, mechanical strength, molecular permeability, optical clarity, and surface morphology of the as‐prepared hybrid PMMA–SiO₂ nanocomposites in the form of membranes were investigated with thermogravimetric analysis, differential scanning calorimetry, dynamic mechanical analysis, gas permeability analysis, ultraviolet–visible transmission spectroscopy, and atomic force microscopy, respectively. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Effects of the nature and combinations of solvents in the intercalation of clay with block copolymers on the properties of polymer nanocomposites

Polystyrene (PS) nanocomposites were prepared by the free‐radical polymerization of styrene in the presence of organically modified montmorillonite (MMT) clays. MMT clay was modified with a low‐molecular‐weight and quarternized block copolymer of styrene and 4‐vinylpyridine [poly(styrene‐b‐4‐vinylpyridine) (SVP)] with 36.4 wt % PS and 63.6 wt % poly(4‐vinylpyridine) (P4VP). Special attention was paid to the modification, which was carried out in different compositions of a solvent mixture of tetrahydrofuran (THF) and water. The swelling behavior of the MMT clay was studied by an X‐ray diffraction technique. The diffraction peak shifted to lower 2θ angles for all of the modified clays, which indicated the intercalation of the quarternized SVP copolymer into the MMT layers in different degrees. Higher interlayer distances, which showed a high degree of block copolymer insertion, were obtained for solvent compositions with THF in water. The resultant nanocomposites were characterized by X‐ray diffraction, atomic force microscopy, scanning electron microscopy, thermogravimetric analysis, and dynamic mechanical analysis. The desired exfoliated nanocomposite structure was achieved when the MMT modification was conducted in 50 or 66 wt % THF, whereas the other modifications all resulted in intercalated structures. The resulting exfoliated nanocomposite was found to have better thermal stability and dynamic mechanical performance compared to the others, even with 2% clay loading. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Atomic force microscopy study on structure and properties of irradiation grafted silica particles in polypropylene‐based nanocomposites

Nanosilica particles treated by irradiation grafting polymerization can effectively improve the strength and toughness of a thermoplastic polymer at a rather low filler content. A detailed investigation on the modified nanoparticles in the absence and presence of a polypropylene matrix is carried out by using atomic force microscopy. The results indicate that the loosen agglomerates of the untreated SiO₂ became more compact due to the linkage between the nanoparticles offered by the grafting polymer. In addition, the molecules of the polypropylene matrix are able to diffuse into the modified nanoparticle agglomerates during the melt processing. Entanglement between the molecules of the grafting polymer and the matrix is thus available, which in turn facilitates a strong particle–matrix interfacial interaction. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 2218–2227, 2001     

Preparation of titanium dioxide/polyacrylate nanocomposites by sol–gel process in reverse micelles and in situ photopolymerization

UV‐curable, transparent acrylic resin/titania organic–inorganic hybrid films were prepared by controlled hydrolysis of titanium tetrabutoxide in Span‐85/Tween 80 reverse micelles and the subsequent in situ photopolymerization of the acrylic monomers. UV–vis spectra and atomic force microscopy (AFM) indicated the presence of a nanoscale hybrid composition. The onset of absorption (λ_onset) of titania in the hybrids appeared between 363.4 and 383.5 nm, which exhibited blue shifts relative to that of bulk anatase (λ_onset = 385 nm). The titania content increased rapidly at higher temperature and higher TTB content, whereas it increased slowly with longer post‐thermal treatment times. The refractive index and UV shielding properties of the organic polymer were obviously improved with increasing titania content. AFM images showed the inorganic domains (mean size 25.3–28.8 nm) were uniformly dispersed in the polymeric networks. The roughness parameters of the hybrid material were: toughness, 1.5–2.3 nm; root mean square roughness, 4.5–4.6 nm; and peak and valley distance, 9.7–19.4 nm. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 5105–5112, 2006     

Characterization of lignocellulosic–poly(lactic acid) reinforced composites

The effects of adding poly(lactic acid) (PLA) to the physical strength of paper test sheets prepared from three unbleached loblolly pine kraft pulps with different amounts of lignin and an aspen bleached chemothermomechanical pulp were studied. The physical strength studies demonstrated that relatively low levels of PLA addition (0.5–4.0%) could dramatically improve the tensile and burst strength properties as a function of the amount of PLA added. Hot pressing the test sheets was shown to be an important treatment for enhancing the strength properties. An analysis of untreated and PLA‐treated hot‐pressed test sheets by atomic force microscopy indicated that the addition of PLA markedly altered the surface properties of the sheets. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 1346–1349, 2006     

Rheological,electrokinetic, and morphological characterization of alginate–bentonite biocomposites

We prepared biocomposite gel dispersions involving sodium alginate (Na‐Alg) and calcium bentonite (Ca‐B) with various solid concentrations and characterized their rheological, electrokinetic, and morphological properties. The flow properties, such as the apparent and plastic viscosities, shear stress, and yield value point, changed with increasing clay dosage. The viscosities of the homogeneous dispersions were represented by the Herschel–Bulkley model. The ζ‐potential results were examined in the light of different characterization methods (X‐ray diffraction, Fourier transform infrared spectroscopy, and atomic force microscopy) to understand the interactions between the Na and Ca ions of the alginate biopolymer and bentonite clay. A plausible structural model for the alginate–bentonite composite gel, known as the egg‐box model, is proposed. The presence of Ca ions in the Ca‐B partially crosslinked Na‐Alg may be regarded as an excellent example of a self‐assembling process. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011.     

A physical approach to define a class A surface in polymer thermosetting composite materials

In polymeric composite material, a class A surface is a high‐quality surface according to its visual appearance. Bulk molding compound polymeric composites behave as a dielectric material with high bulk light scattering, low specular reflection, and low surface scattering. Gloss, related to specular reflection, is then low and cannot be a sufficient criterion to qualify a composite surface. For this purpose, we propose using either haze or roughness and power spectrum density (PSD) measured by AFM. An alternative solution to qualify a surface sample is to cover the sample by a metallic film. The sample then behaves as a metallic material with a main specular reflection and light scattering exclusively because of the surface. Measurements of gloss, haze, PSD, or roughness over a given spatial frequency range can qualify a sample surface and could especially define a surface in the class A family. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 451–461, 2007     

Effect of sterilization techniques on the physicochemical properties of polysulfone hollow fibers

Sterilized hollow‐fiber membranes are used in hemodialysis, ultrafiltration, bioprocessing, and tissue engineering applications that require a stable and biocompatible surface. In this study, we demonstrated significant changes in the fiber physicochemical properties with different methods of sterilization. Commercial polysulfone (PS) hollow fibers containing poly(vinyl pyrrolidone) were subjected to standard ethylene oxide (ETO), sodium hypochlorite (bleach), and electron‐beam (e‐beam) sterilization techniques followed by analysis of the surface hydrophilicity, morphology, and water‐retention ability. E‐beam sterilization rendered more hydrophilic fibers with water contact angles near 47° compared to the ETO‐ and bleach‐treated fibers, which were each near 56°. Atomic force microscopy revealed lumen root mean square (rms) roughness values near 19 nm for all three sterilization methods; however, e‐beam‐sterilized and bleach‐treated fibers had significantly higher (～ 106 nm) rms values for the outer wall compared to the ETO‐sterilized fibers (～ 39 nm). The increased hydrophilicity and surface area of the e‐beam‐sterilized fiber were reflected by a greater water evaporation rate than that of the ETO‐treated fiber. These results demonstrate that common sterilization methods may significantly and distinctly alter the polymer membrane physicochemical properties, which may, in turn, impact the performance and, in particular, surface fouling. For tissue engineering and bioprocessing applications, these changes may be leveraged to promote cell adhesion and spreading. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Preparation and characterization of hybrid organic–inorganic epoxide‐based films and coatings prepared by the sol–gel process

Hybrid organic–inorganic coatings and free‐standing films were prepared and characterized. The hybrids were prepared from [3‐(glycidyloxy)propyl]trimethoxysilane, diethoxy[3‐(glycidyloxy)propyl]methylsilane, poly(oxypropylene)s of different molecular weights end‐capped with primary amino groups (Jeffamines D230, D400, and T403), and colloidal silica particles with hydrochloric acid as a catalyst for the sol–gel process and water/propan‐2‐ol mixtures as solvents. The structure evolution during the network formation was followed by NMR spectroscopy and small‐angle X‐ray scattering; the surface morphology was tested by atomic force microscopy. The influence of the reaction conditions (the organosilicon precursor, oligomeric amine, ratio of functional groups, and method of preparation) on the network buildup and product properties was studied and examined. The mechanical testing, based on stress–strain experiments, in combination with dynamic mechanical thermal analysis served as an effective instrument for the optimization of the reaction conditions for the preparation of products with desired properties. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 937–950, 2004     

Comparative study on structural features of α chitin from Xiphopenaeus kroyeri and its precipitated product from phosphoric acid solution

A sample of α chitin was obtained from shells of the shrimp Xiphopenaeus kroyeri by demineralization and deproteinization processes. This sample of native α chitin (NC) was dissolved in concentrated phosphoric acid and recovered by precipitation in an alkaline aqueous solution, giving rise to a sample named PC. Solid‐state carbon‐13 nuclear magnetic resonance (¹³C‐NMR), X‐ray diffraction, and atomic force microscopy (AFM) techniques were used to compare both samples and to investigate structural changes in α chitin under the action of phosphoric acid. ¹³C‐NMR experiments and X‐ray diffraction results revealed a high crystalline order in both samples. Structural differences were due to the higher distance between adjacent chains along the b axis and the consequent decrease in the number of intermolecular hydrogen bonds in the sample recovered from solution. While remarkable supramolecular differences could be observed in the fibrillar crystals of the NC sample, the PC sample was characterized by only one type of morphology. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 151–159, 2002