Structure Of Polymer Matrix Research Articles

Statistical Evaluation Tensile Properties of High-Density Polyethylenes

The mechanical properties, among all the properties of plastic materials, are often the most important properties because virtually all service conditions and the majority of end-use applications involve some degree of mechanical loading [1]. In the present work three different commercial polyethylene materials are tensile tested at four or five different tensile rates and two or three temperatures. Tensile test results against tensile rate include stress at 0.5 % elongation, tensile strength, yield strength, modulus of elasticity, elongation at yield and % elongation are determined. It is concluded that the structure, chain lengths and branching rates of polymer matrix significantly effected tensile test curve characteristic.

Transmission Performance and Free Volume of Gel Electrolyte Membranes Based on Comb-like Methyl Methacrylate Copolymers

Three comb-like methyl methacrylate copolymer matrixes for gel polymer electrolyte (GPE) were synthesized by reacting methyl methacrylate-maleic anhydride copolymer (P(MMA-co-MAh)) with poly(ethylene glycol) monomethylether (PEGME) of different molecular weight (350, 600, and 750), respectively. Three kinds of GPE membranes made from comb-like copolymers as matrix, shorted for CL350, CL600, CL750, propylene carbonate (PC) as plasticizer and LiClO4 as salt, have been prepared by solution casting technique. By studying the ion transporting properties of the GPE, it is found that the conduction mechanism of the GPE accords with VTF (Vogel-Tamman-Fulcher) equation, which is derived from free volume theory. Positron annihilation lifetime spectroscopy (PALS) was employed to analyze the properties of free volume in GPE systems and the effect of microstructure on conductivity of GPE membranes. It is noted that increasing the side chain length of polymer matrixes will increase the free volume existed in system. When the content of polymer matrix is 45 wt%, free volume in CL750 based GPE membrane is 21% larger than that in CL350 based GPE membrane. Correspondingly, compared with CL350 system, the ionic conductivity of CL750 system grows by 200%. It is apparent that the ionic conductivity of GPE membranes is affected by the structure of polymer matrix to a great extent.

Influence of Polymer Gel Electrolyte on the Performance of Dye-Sensitized Solar Cells Analyzed by Electrochemical Impedance Spectroscopy

The effects of gel electrolyte polymer matrix structure and composition on the photovoltaic properties of quasi-solid state dye-sensitized solar cells(DSSCs) were investigated using two series of copolymers,poly(hydroxy ethyl methacrylate-N-vinyl) pyrrolidone P(HEMA-NVP) and poly(methyl methacrylateN-vinyl pyrrolidone) P(MMA-NVP),by electrochemical impedance spectroscopy(EIS).P(HEMA-NVP) copolymers with various crosslinking agent and N-vinyl pyrrolidone(NVP) contents,as well as P(MMA-NVP)copolymers with various NVP content,absorbed liquid electrolyte to form gel electrolytes HGelI,HGelII,and MGel,respectively.It was found that with increasing copolymer P(HEMA-NVP) crosslinking agent content,from 0.1 to 0.6%(w),the power conversion efficiency(η) of DSSCs based on HGelI initially increased and then decreased.A maximum conversion efficiency of 5.54% at 100 mW.cm-2 was observed when crosslinker content was 0.4%(w).Meanwhile,we compared the parameters of DSSCs based on HGelII with those of DSSCs based on MGel.The conversion efficiencies of the former,which contained hydroxy groups,were all higher than those of the latter,while the open circuit voltages(Voc) of the latter were larger than those of the former.DSSCs assembled with HGelII with a HEMA content of 60% exhibited the highest conversion efficiency,at 100 mW.cm-2.Electrochemical impedance spectroscopy(EIS) investigations showed that copolymer crosslinking structure affected the internal resistance and ionic conductivity of the resulting DSSCs,while addition of hydroxy groups decreased the interfacial resistance.Thus,the photovoltaic performance of DSSCs can be improved by tuning the crosslinking structure and the hydroxy content of the copolymer.

Magnetic field and particle concentration competitive effects on ferrofluid based silicone elastomer microstructure

Structural peculiarities of ferroelastomers composed of polydimetylsiloxane with embedded magnetite particles during polymerization have been studied by small-angle neutron scattering. The effects of ferroparticles’ concentration in the range of C = 0–6 wt %, and external magnetic fields of induction B = 0−1 kG applied during the polymerization on the structure of polymeric matrix and particles distribution in polymer were analyzed.

A potential enzyme-encapsulating, ultrafine fiber for phenol detection

Ultrafine composite fibers of silicate–polymer matrix structure were synthesized by the combination of sol–gel chemistry and electrospinning to immobilize a tyrosinase enzyme for the purpose of continuous and/or reusable operations. These ultrafine enzyme-carrying fibers with average diameters of less than one micron were studied by their incorporation into a small-scale, flow-through micro-reactor to demonstrate the feasibility of phenol detection with simultaneous remediation through biocatalysis. Biocatalytic activity of the electrospun enzyme (tyrosinase) was confirmed and evaluated using the integrated form of the Michaelis–Menten equation, having the advantage of requiring fewer experimental runs than other approaches. Micro-Raman spectral analysis was also used to demonstrate biocatalysis and the possible biocomposite nature of the enzyme-carrying fibers. Biocatalytic activity of the electrospun enzyme was retained at phenol concentrations of 0.12–5 mM, typical of contaminated waters. This research demonstrates the potential of this cost-effective fibrous material for biocatalysis and detection applicable in environmental and industrial analysis and remediation.

Structure and thermostability of PMMA in PMMA/silica nanocomposites: Effect of high‐energy ball milling and the amount of the nanofiller

AbstractIn this work, the effect of the presence of silica nanoparticles in the structure, dynamics, and thermodegradation of poly(methyl methacrylate), PMMA, has been considered. A new method for preparing nanocomposites has been considered in which high‐energy ball milling, HEBM, was used to uniformly disperse nanoparticles within a polymeric matrix (PMMA). Fourier transform infrared spectroscopy, FTIR, was used to analyze the structure and dynamics of the PMMA to study the influence of the presence of silica nanoparticles and finally to discuss the thermal stability of these nanocomposites. Dynamic thermogravimetric analyses were performed to carry out the kinetics analysis about the thermostability of the modified PMMA, being the milling process and the amount of nanoparticles the variables taken into account. The milling process creates chain ends on the PMMA favoring its first step of thermal degradation. There is only an improvement in terms of thermal stability if the amount of silica nanoparticles within the PMMA exceeds a threshold higher than 2% by weight when the unfavorable effect of the milling process is compensated. POLYM. COMPOS., 31:1585–1592, 2010. © 2009 Society of Plastics Engineers

Nanofiber Composites of Polyvinyl Alcohol and Cellulose Nanocrystals: Manufacture and Characterization

Cellulose nanocrystals (CN) were used to reinforce nanofibers in composite mats produced via electrospinning of poly(vinyl alcohol) (PVA) with two different concentrations of acetyl groups. Ultrathin cross-sections of the obtained nanocomposites consisted of fibers with maximum diameters of about 290 nm for all the CN loads investigated (from 0 to 15% CN loading). The electrospinning process did not affect the structure of the PVA polymer matrix, but its degree of crystallinity increased significantly together with a slight increase in the corresponding melting temperature. These effects were explained as being the result of alignment and enhanced crystallization of PVA chains within the individual nanofibers that were subjected to high shear stresses during electrospinning. The strong interaction of the PVA matrix with the dispersed CN phase, mainly via hydrogen bonding or bond network, was reduced with the presence of acetyl groups in PVA. Most importantly, the elastic modulus of the nanocomposite mats increased significantly as a consequence of the reinforcing effect of CNs via the percolation network held by hydrogen bonds. However, this organization-driven crystallization was limited as observed by the reduction in the degree of crystallinity of the CN-loaded composite fibers. Finally, efficient stress transfer and strong interactions were demonstrated to occur between the reinforcing CN and the fully hydrolyzed PVA electrospun fibers.

Chain Degradation during Dissolution of Polymer-Fullerene Nanocomposites as a Result of Interaction of Entangled Polymer Matrix with the Filler

Chain degradation of poly(α-methylstyrene) and polystyrene during dissolution of their nanocomposites with fullerene C60 in solvents of different quality with respect to fullerene was studied in detail by size exclusion chromatography and UV spectroscopy. Chain ruptures have been shown to arise during swelling of composites but only for samples with entangled polymer matrix. The data obtained confirm that the hindered mobility of chains because of interaction of the entangled matrix with fullerene is the only cause of degradation. Chain rupture leads to radical depolymerization accompanied by covalent binding of fullerene with the chain fragments, which results in changing of the polymer matrix structure. Chain degradation indicates deterioration of the mechanical properties of the polymers in the presence of C60. The possibility of chain degradation in polymer-filler nanocomposites under deformation with the simultaneous observation of an apparent reinforcement effect because of the addition of filler in the polymer matrix is discussed.

Effect of crosslinking on the properties of sodium caseinate films

AbstractProtein films are used as effective lipid, oxygen, and aroma barriers at moderate relative humidity conditions. However, they perform poorly as moisture barriers. The introduction of crosslinks within or between protein chains by enzymatic or chemical modification has been proposed as an alternative means to achieving a stronger polymeric matrix structure, which would result in better functional film properties. In this article, we report the preparation and characterization of sodium caseinate (SC) films crosslinked by glutaraldehyde (GTA) or heat. The crosslinking density increased with GTA content. The thermal stability and tensile modulus and strength increased with GTA content, although films with a low crosslinking density exhibited lower properties than the uncrosslinked sample. Unexpectedly, water vapor permeability and absorption also increased with crosslinking density. The crosslinking of SC was also induced by simple heating. The resulting films showed enhanced thermal, mechanical, and barrier properties compared to the unmodified SC films and even the GTA‐crosslinked samples. GTA crosslinking was unable to reduce the high hydrophilicity of the SC films. Thermally induced crosslinking was revealed to be a valid alternative for improving the properties of SC films, without the inherent complications associated with the use of a chemical crosslinking agent. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010

Interfacial enhancement by shish–calabash crystal structure in polypropylene/inorganic whisker composites

Abstract The polymer matrix structure and the interface are strongly influenced by filler in semi-crystalline polymer composites because the fillers have the potential to nucleate the polymer crystallization. The structure of the nucleated crystalline polymer on filler is of particular interest and is a key to the interfacial enhancement. In this work, whiskers, with a large length/diameter ratio and with a diameter (0.2–2 μm) much larger than that of carbon nanotubes but much smaller than that of common fibers, were used to nucleate crystal morphology in polypropylene (PP)/whisker composites. The crystal morphology, interfacial adhesion and tensile properties of the composites were carefully investigated. A kind of peculiar shish–calabash crystallization morphology, with whisker serves as shish and PP spherulites serves as calabash, was observed for the first time in the thin film via PLM and in the injection molded bars by SEM. The formation mechanism of this shish–calabash structure was attributed to be that only a few nuclei could be induced on the whisker surface, which develop into large PP spherulites without hindrance, and finally stringed by the whisker, forming the shish–calabash structure. As a result, a significant improvement of interfacial interaction and tensile properties has been achieved.

Development of a new generation of filament wound composite pressure cylinders

A new generation of composite pressure vessels for large scale market applications has been studied in this work. The vessels consist on a thermoplastic liner wrapped with a filament winding glass fibre reinforced polymer matrix structure. A high density polyethylene (HDPE) was selected as liner and a thermosetting resin used as matrix in the glass reinforced filament wound laminate. The Abaqus 6.5.1 FEM package was used to predict the mechanical behaviour of pressure vessels with capacity of approximately of 0.06 m (60 l) for a 0.6 MPa (6 bar) pressure service condition according to the requirements of the EN 13923 standard, namely, the minimum internal burst pressure. The Tsai-Wu and Von Mises criteria were used to predict composite laminate and thermoplastic liner failures, respectively, considering the elasto-plastic behaviour of the HDPE liner and the laminae properties deducted from micromechanical models for composite laminates. Finally, prototype pressure vessels were produced and submitted to pressure tests in similar conditions to those used in the FEM simulations. The comparison between the FEM simulations and experimental results are discussed in the present paper.

Effect of Processing Method on Conductivity and Mechanical Properties of Glass Fibre Reinforced Carbon Black Filled Polyethylene

The conductivity and mechanical properties of carbon black (CB) filled polyethylene (PE) composites depend on the conductive filler, molecular structure of polymer matrix, and the processing methods which are applied. CB filled high density polyethylene without and with glass fibre (GF) composites have been manufactured using single and twin screws extruder. The composite made from the single screw extruder showed a much higher conductivity than that made from twin screws extruder for CB/PE composites with and without glass fibre. The conductive paths are formed at very low CB content (1wt% CB for GF/CB/PE) when using single screw extruder to manufacture. The microstructure of these composites were analysed using SEM.

Colloidal Crystallization of Polymer-grafted Silica and Fabrication of Particle Array Structure in Polymer Matrix

Colloidal Crystallization of Polymer-grafted Silica and Fabrication of Particle Array Structure in Polymer Matrix

Physicochemical, Morphological and Therapeutic Evaluation of Agarose Hydrogel Particles as a Reservoir for Basic Fibroblast Growth Factor

Micron-sized agarose hydrogel particles were prepared using an emulsification/gelation method as a controlled release reservoir for basic fibroblast growth factor (bFGF). Mean particle size of agarose hydrogel particles decreased with an increase in stirring speed and also with an increasing temperature of the oil phase, as measured before cooling. Morphologies of agarose particles before and after dispersing into water were investigated by scanning electron microscopy (SEM) and cryogenic SEM, respectively. Freeze-dried agarose particles were spherical with rough surface. Porous polymer matrix structure was observed in the hydrogel particles by cryo-SEM. More than 99% of bFGF was encapsulated and the release from the agarose hydrogel particles was less than 3% during the incubation in phosphate buffered saline. bFGF molecules were not only adsorbed on the particle surface but also permeated and retained within the matrix. The therapeutic efficacy of bFGF retained in agarose hydrogel particles was significantly higher than that dissolved in saline. Agarose hydrogel particle seems to be a potential candidate for a bFGF reservoir.

From conductive polymer composites with controlled morphology to smart materials

Conductive polymer composites (CPC) based on insulating matrix with conductive dispersed fillers are extensively studied since many years. A specific feature of such materials is a value of the filler content corresponding to the percolation threshold where a sharp transition insulating/conductive state occurs. The objective of this work is first the study of percolation phenomena in composites based on polypropylene (PP), on copolymers of polyamides (CPA) and polymer blends PP/CPA filled with dispersed iron (Fe) related to their structure but also to pay attention to their specific behaviour in temperature so-called PTC effect which can be controlled according the composition and the structure in the heterogeneous polymer matrix of the composites to elaborate intelligent/smart materials.

Siloxane-containing polymer matrices as coating materials

Coating materials based on siloxane-containing polymer matrices that had been modified with fluoropolymer or acrylic resins and applied as organic components of hybrid systems were examined. The optimal recipes of the dispersion systems, applied as polymer matrix precursors, were determined on the basis of factorial experiments, designed as 22 with additional ‘star’ experimental points to obtain greater accuracy in the resulting regression equations. The siloxane cage formation was based on the following crosslinking reactions of functional polysiloxanes: (1) hydrosilylation of vinyl groups; (2) condensation of silanol groups. Moreover, the molecular modeling, using P3 semi-empirical methods, was applied to build the model structure of a siloxane-containing polymer matrix. The surface properties of these coatings were studied using wettability assessments (dynamic contact angle and surface-free energy evaluation), atomic force microscopy (AFM), and X-ray electron microscopy (ESCA-XPS). The morphology, roughness, and structural regularity are discussed to illustrate the effects of the organic component on the surface properties. The most significant changes were observed in the surface morphology of the coatings. The application properties of such coating materials for the protection of buildings were tested, based on studies of their water vapor permeability, water absorption, and weathering resistance (freezing/thawing, salt-saturated aqueous sodium sulfate solution). The effect of the chemical structure of the siloxane-containing polymer matrix on the properties of the resulting coatings was focused on the protection of porous building materials. A very good correlation of the application properties of these coating materials and their surface properties, such as high dynamic contact angle (DCA), low surface-free energy (SFE) and surface morphology, was observed and is discussed.

Morphology, deformation behavior and thermomechanical properties of polypropylene/maleic anhydride grafted polypropylene/layered silicate nanocomposites

AbstractNanocomposites polypropylene (PP) with 3 and 7 wt % of clay were prepared by melt mixing. Four types of maleic anhydride grafted PP (MAPP) in broad range of MA groups content (0.3–4 wt %) and molecular weights (MW) were used as polar compatibilizers. The effect of the MAPP kind on both the clay dispersion and miscibility with PP was studied. The mixed intercalated/exfoliated morphologies of nanocomposites in the presence of all studied compatibilizers were revealed by XRD and TEM. The oligomer compatibilizer with 4 wt % of MA groups increases the intercalation ability of polymer into clay galleries but this one has limited miscibility with PP and worsens crystalline structure of polymer matrix. The MAPPs with 0.3–1.3% of MA are characterized by the lower intercalation ability but well cocrystallize with PP. Maximum reinforcing effect is attained using high MW MAPP with 0.6% MA and for nanocomposite with 7 wt % (3.8 vol %) of clay it averages almost 1.7 times relative to neat PP and 1.3 times relative to noncompatibilized composite. Dynamic storage moduli of nanocomposites compatibilized by MAPPs with 0.3–1.3% of MA containing 7 wt % of clay increase up to 1.4–1.5 around 30–75°C and over the whole temperature range remain higher compared with both neat PP and uncompatibilized composite. On the contrary, the oligomer MAPP with 4 wt % of MA groups decreases the thermal–mechanical stability of nanocomposite at high temperature compared with both PP and uncompatibilized composites. The study of nanocomposites flammability showed that creating complex composites containing both layered silicate and relatively small amount of magnesium hydroxide can be a successful approach to reduce the combustibility of PP‐based nanocomposites. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007

PSYCHOPHYSICAL MARKERS FOR CRISPNESS AND INFLUENCE OF PHASE BEHAVIOR AND STRUCTURE

ABSTRACT This article focuses on developing a psychophysical model for sensory crispness and understanding the role of structure and phase behavior of the food polymer matrix in terms of affecting crispness. The core hypothesis of the article is that the number peaks during brittle fracture of food foams is the stimulus for crispness. Accurate mechanical methods were developed to count the peaks and then relate them to sensory crispness scores utilizing magnitude estimation. An excellent correlation was obtained with data that was generated in three independent sets of measurements. Finally, models describing the relationship between structure, mechanical signatures and sensory crispness of extruded cellular foods were developed. PRACTICAL APPLICATIONSTexture is one of the most important quality attributes of food products. The fracture properties of the foods have to be clearly understood, because they are one the most important manifestations of texture. Understanding the fracture process in‐depth can help increase consumer acceptability by generating structures leading a particular breakdown behavior, because the sensory attributes like crispness are directly related to how the fracture occurs in solid food foams. The psychophysical model developed in this study will serve as a very useful tool for assessing the effects of changes in formulation and processing that result in a wide range of structural features leading to the desired crisp sensation in the final product.

Phenomenon of electrical resistivity reduction by UV irradiation for UV-curable polymer composite film including a small amount of VGCF

It was unexpectedly observed that the volume electrical resistivity of UV-curable polymer film including a small amount of vapor-grown carbon fiber (VGCF) along thickness direction decreased by three ordered magnitude (from 1010 to 107 Ω· cm) after UV irradiation. The cause of the rapid decrease was investigated by changing various parameters, such as, VGCF concentration, thickness, VGCF structure (linear or branch, dispersion), and volume shrinkage of UV-curable polymer matrix. The decrease occurred reproducibly when the concentration of VGCF was between 0.005 and 0.1 wt % with thickness less than 25 μm. The moving distance of VGCF by UV irradiation through the volume shrinkage of the matrix was confirmed to be around 9.0 micron at the center part of the film. It was suggested from optical microscope observation that the presence of a trace amount of branched VGCF (L, X, Y form) having similar length to the film thickness moved by the volume shrinkage of UV-curable polymer matrix during UV irradiation and made the conductive paths along thickness direction.

Spectroscopic Studies of Poly(ε-Caprolactone)/Sodium Montmorillonite Nanocomposites

Polymer-layered silicate nanocomposites belong to a new class of hybrid materials consisting of organic-synthetic polymer matrix and inorganic filler-layered structure clay minerals. The paper presents the results of FTIR, NMR, and SAXS studies of poly(e-caprolactone)/sodium montmorillonite nanocomposites. We observed a correlation between the concentration of poly(e-caprolactone) in nanocomposite samples and structural changes both of the clay mineral and the intercalated polymer. Stiffening of the clay structure appears as a result of poly(e-caprolactone) intercalation into a clay structure. Al NMR studies indicated in nanocomposites two non-equivalent sites of aluminium ions, i.e. in octahedral and tetrahedral coordination, whereas in the montmorillonite clay structure the aluminium ions are located in the interlayer space too. We found also that the temperatures of structural changes and softening process of poly(e-caprolactone) chains in the nanocomposites depend on the concentration of poly(e-caprolactone).