Journal of Polymers The latest articles from Hindawi © 2017 , Hindawi Limited . All rights reserved. Variation of the Pole Length in Pole-Oriented Bonded Rings due to the Location and Number of Injection Points Wed, 15 Feb 2017 09:11:01 +0000 Polymer bonded magnets are compounds consisting of a polymer matrix with embedded hard magnetic filler particles. These materials are mainly used in applications in actor or sensor technology. One example is the application as multipolar encoder wheel in magnetic sensors. Depending on the application different requirements have to be fulfilled, such as a high pole length accuracy and repeatability. This investigation deals with the production of multipolar rings in the injection molding process for sensor applications and influences of the design of the gating system on the pole length accuracy. It is shown that the number of injection points and developing weld lines, as well as the positioning of the injection points, has a major influence on the magnetization characteristics of the molded rings. In general, a positioning of injection points and weld lines in the pole pitch and higher number of injection points lead to rings with a high reproduction accuracy of the pole length of the mold. Katharina H. Kurth and Dietmar Drummer Copyright © 2017 Katharina H. Kurth and Dietmar Drummer. All rights reserved. Synthesis, Properties, and Humidity Resistance Enhancement of Biodegradable Cellulose-Containing Superabsorbent Polymer Tue, 10 Jan 2017 00:00:00 +0000 To improve the humidity resistance and water absorption capacity of the superabsorbent polymer (SAP), a biodegradable cellulose-containing polymer was successfully assembled through inverse suspension polymerization, using cellulose, acrylic acid, and acrylamide as monomers, Span-80 as dispersant, and potassium persulfate as initiator. The impact of conditions such as reaction temperature, ratio of oil to water, degree of neutralization, amount of cellulose, and cross-linking agents on the properties of the polymer were evaluated. The results showed that the as-prepared superabsorbent polymer exhibited the best water (859 g/g) and salt water (72.48 g/g) absorption rate, when the reaction temperature was 70°C, monomer ratio was 1 : 10, neutralization degree was 75%, and oil-water ratio was 3 : 1. Moreover, the humidity resistance of the polymer could be enhanced significantly by adding different cross-linking reagents such as epoxy chloropropane or diethylene glycol. Hongliang Guan, Junbo Li, Biyu Zhang, and Xunmin Yu Copyright © 2017 Hongliang Guan et al. All rights reserved. Isolation and Characterization of 1,3-Bis(vinylbenzyl)thymine: Copolymerization with Vinylbenzyl Thymine Ammonium Chloride Wed, 04 Jan 2017 08:11:20 +0000 A novel bioinspired molecule, 1,3-bis(vinylbenzyl)thymine (bisVBT), was isolated as a by-product during the synthesis of 1-(4-vinylbenzyl)thymine (VBT) and analyzed with various techniques: NMR, IR, and Single-Crystal X-ray Diffraction. In addition to embodying all the desired characteristics of VBT (i.e., having the ability to undergo a photodimerization reaction upon UV irradiation, a derivatization site, hydrogen bonding sites, and aromatic stacking ability) the bisVBT monomer has the added benefit of having two vinyl groups for cross-polymerization. Copolymerizing the bisVBT monomer with the charged monomer vinylbenzyl triethylammonium (VBA) chloride, different copolymers/terpolymers/cross-linked network were obtained, as it was shown by the absence of the vinyl resonance in the NMR spectra. Thermal Gravimetric Analysis (TGA) and Differential Scanning Calorimetry (DSC) showed an indication of materials with low degree of cross-linking. A Gel Permeation Chromatography (GPC) method was improved to better characterize the molecular weight distributions of the cationic structures. Preliminary qualitative cross-linking studies were performed on bisVBT-VBA copolymers, and a comparison with VBT-VBA copolymers is presented. Ngoc Chau H. Vy, Nina Bin Chen, Debora M. Martino, John C. Warner, and Nancy Lee Copyright © 2017 Ngoc Chau H. Vy et al. All rights reserved. Effect of Urea Concentration on the Viscosity and Thermal Stability of Aqueous NaOH/Urea Cellulose Solutions Wed, 23 Nov 2016 09:47:16 +0000 Aqueous solutions of sodium hydroxide (NaOH) and urea are a known and versatile solvent for cellulose. The dissolution of cellulose occurs at subambient temperatures through the formation of a cellulose-NaOH-urea “inclusion complex” (IC). NaOH and urea form a hydrate layer around the cellulose chains preventing chain agglomeration. Urea is known to stabilize the solution but its direct role is unknown. Using viscometry and quartz crystal microbalance with dissipation monitoring (QCM-D) it could be shown that the addition of urea reduced the solutions viscosity of the tested solutions by almost 40% and also increased the gelation temperature from approximately 40°C to 90°C. Both effects could also be observed in the presence of additional cellulose powder serving as a physical cross-linker. Using Fourier transform infrared (FTIR) spectroscopy during heating, it could be shown that a direct interaction occurs between urea and the cellulose molecules, reducing their ability to form hydrogen bonds with neighbouring chains. Tim Huber, Katherine Starling, Wanwen (Samantha) Cen, Conan Fee, and Simone Dimartino Copyright © 2016 Tim Huber et al. All rights reserved. Experimental Studies on the Bonding Strength and Fracture Behavior of Incompatible Materials Bonded by Mechanical Adhesion in Multilayer Rotational Molding Tue, 22 Nov 2016 13:52:29 +0000 Rotational molding is a plastic processing method that allows for the production of seamless, hollow parts. Defined shaping of the polymeric material only takes place on the outer surface where contact to the tooling is given. The inner surface forms by surface tension effects. By sequential adding of materials, complex multilayer build-up is possible. Besides pure, single materials, filled, or multiphase systems can be processed as well. In this work, possibilities to generate bonding between supposedly incompatible materials by adding a mix-material interlayer are investigated. Interlock mechanisms on a microscale dimension occur and result in mechanical bonding between the used materials, polyethylene (PE) and thermoplastic polyurethane (TPE-U). The bonding strength between the materials was investigated to reveal the correlations between processing parameters, resulting layer build-up, and bonding strength. The failure behavior was analyzed and inferences to the influence of the varied parameters were drawn. Martin Löhner and Dietmar Drummer Copyright © 2016 Martin Löhner and Dietmar Drummer. All rights reserved. Radiation Crosslinking of Polyurethanes: Characterization by FTIR, TGA, SEM, XRD, and Raman Spectroscopy Sun, 06 Nov 2016 11:36:41 +0000 Gamma radiation can be used for enhancing the physical properties of polyurethane (PU). Radiation was used to crosslink a polyurethane at room temperature; four samples of the PU solid film are irradiated at variable four radiation doses 0, 50, 100, and 150 kGy under vacuum conditions. Crosslinking radiation is more common than oxidative degradation and crosslinking is believed to be more efficient in the soft segment of PU. The structure of the PUs is performed by Fourier transform infrared (FTIR-ATR), Thermogravimetric Analysis (TGA-DTG), and X-ray Diffraction (XRD) which have been used to investigate the effect of gamma radiation on the polyurethane (PU). The results showed that the radiation crosslinking of polyurethanes improved the thermal stability and the crystallinity. The microstructure modifications of polyurethane samples have also been studied as a function of the dose using the scanning electron microscope (SEM). The effects of gamma irradiation on the color changes of polyurethane were observed. The irradiated PUs have conjugated structure and are capable of emitting purple fluorescence. Mohamed Mohamady Ghobashy and Zizi I. Abdeen Copyright © 2016 Mohamed Mohamady Ghobashy and Zizi I. Abdeen. All rights reserved. Modelling the Heating Process in Simultaneous Laser Transmission Welding of Semicrystalline Polymers Thu, 27 Oct 2016 09:19:34 +0000 Laser transmission welding is an established joining process for thermoplastics. A close-to-reality simulation of the heating process would improve the understanding of the process, facilitate and shorten the process installation, and provide a significant contribution to the computer aided component design. For these reasons a thermal simulation model for simultaneous welding was developed which supports determining the size of the heat affected zone (HAZ). The determination of the intensity profile of the laser beam after the penetration of the laser transparent semicrystalline thermoplastic is decisive for the simulation. For the determination of the intensity profile two measurement systems are presented and compared. The calculated size of the HAZ shows a high concordance to the dimensions of the HAZ found using light microscopy. However, the calculated temperatures exceed the indicated decomposition temperatures of the particular thermoplastics. For the recording of the real temperatures during the welding process a measuring system is presented and discussed. Christian Hopmann and Suveni Kreimeier Copyright © 2016 Christian Hopmann and Suveni Kreimeier. All rights reserved. Joining of Metal-Plastics-Hybrid Structures Using Laser Radiation by Considering the Surface Structure of the Metal Wed, 12 Oct 2016 12:22:03 +0000 Lightweight construction is a central technology in today’s industrial production. One way to achieve the climate goals is the production of hybrid compounds of metal and plastic. The manufacturing process for these hybrid parts can be divided into in-mold assembly and postmold assembly. The postmold assembly includes thermal joining by laser, which is applied in the context of this paper. For the investigations, four plastics (MABS, PA6.6-GF35, PP, and PC), which differ in their properties, and three metals (unalloyed steel, stainless steel, and aluminum) are combined and analyzed. These materials have been used, since they have a huge significance in the automotive industry. Preliminary studies showed that an adhesive bond between the two materials is achieved using metal with a structured surface. According to these studies, three structuring processes for metals (selective laser melting (SLM), NRX, and a welded metallic tissue) are tested. The quality of the material/structure combinations is tested in tensile-shear-tests, microscopy images, and alternating climate tests. Compounds with SLM-Structure achieve highest strength, while compounds with aluminum are much more complex to manufacture. Christian Hopmann, Suveni Kreimeier, Jan Keseberg, and Carsten Wenzlau Copyright © 2016 Christian Hopmann et al. All rights reserved. Weatherability of Polypropylene by Accelerated Weathering Tests and Outdoor Exposure Tests in Japan Mon, 10 Oct 2016 07:52:13 +0000 As a joint study of the Polymer Subcommittee in the Industrial Technology Cooperative Promotion Committee, in which members are Japanese local governmental research institutes and National Institute of Advanced Industrial Science and Technology (AIST, Japan), carried out from 2010 to 2012, polyethylene reference sample (PE-RS) pieces and six types of polypropylene (PP) were subjected to accelerated weathering tests and outdoor exposure tests, resulting in the following findings. (1) The PE-RS was subjected to eight 100 h exposure tests in the same test machine. The accelerated weathering test machines of the participating institutes had high reproducibility. (2) The PE-RS CI values were greater when the temperature in the chamber was greater during accelerated weathering tests, and there was a high correlation with the average temperature in the outdoor exposure tests at 20 places in Japan. (3) By comparing the change in PP strength by normalizing the degradation environment using the PE-RS CI values, the accelerated weathering test with results showing the highest correlation with the outdoor exposure test results was the one with the xenon arc lamp at an irradiance of 60 W/m2 and a BPT of 63°C. Kenichi Shimizu, Yuuki Tokuta, Akihiro Oishi, Takashi Kuriyama, and Masao Kunioka Copyright © 2016 Kenichi Shimizu et al. All rights reserved. Poly(acrylonitrile-co-butadiene-co-styrene) Reinforced with Hollow Glass Microspheres: Evaluation of Extrusion Parameters and Their Effects on the Composite Properties Sun, 10 Jul 2016 09:19:40 +0000 Hollow glass microspheres (HGMs) filled poly(acrylonitrile-co-butadiene-co-styrene) (ABS) composites were prepared by means of a twin-screw extruder. S038 HGMs were incorporated at different percentages of 2.5, 5.0, and 7.5 wt%. The HGMs were added into the twin-screw extruder at two different feeding zones, and the effect of HGMs loading and specific feeding zone addition on the composites produced was evaluated with regard to morphological, thermal, rheological, physical, and mechanical properties. As a result, the composite density was reduced while the thermal stability, storage modulus, complex viscosity, and tensile and flexural modulus were improved when compared with the ABS matrix. The results also indicate that the addition of 5.0 wt% of HGMs at the feeding zone closer to the die maintains the integrity of the HGMs and promotes composites with higher mechanical properties and lower density when compared with the composites obtained with the addition of HGMs closer to the hopper. Marina Panozzo Cunha, Laura Berasain Gonella, Matheus Poletto, Ana Maria Colon Grisa, and Rosmary Nichele Brandalise Copyright © 2016 Marina Panozzo Cunha et al. All rights reserved. Iterative Deconvolution of PEA Measurements for Enhancing the Spatial Resolution of Charge Profile in Space Polymers Thu, 30 Jun 2016 08:39:58 +0000 This work aims to improve the PEA calibration technique through defining a well-conditioned transfer matrix. To this end, a numerical electroacoustic model that allows determining the output voltage of the piezoelectric sensor and the acoustic pressure is developed with the software COMSOL®. The proposed method recovers the charge distribution within the sample using an iterative deconvolution method that uses the transfer matrix obtained with the new calibration technique. The obtained results on theoretical and experimental signals show an improvement in the spatial resolution compared with the standard method usually used. Mohamad Arnaout, Khaled Chahine, Fulbert Baudoin, Laurent Berquez, and Denis Payan Copyright © 2016 Mohamad Arnaout et al. All rights reserved. Novel Gas Barrier SiOC Coating to PET Bottles through a Hot Wire CVD Method Mon, 27 Jun 2016 06:44:05 +0000 In an attempt to enhance the gas barrier enhancement of plastic containers such as poly(ethylene terephthalate) bottles, a novel method was found using a hot wire CVD technique, where tantalum wire is heated and exposed to a gas flow of vinyl silane. The resultant SiOC thin film was confirmed to characteristically contain Si-Si bonds in its surface and demonstrate a remarkably and highly practical decrease of the permeation of various gas through poly(ethylene terephthalate) bottles. Masaki Nakaya, Kenji Kodama, Shigeo Yasuhara, and Atsushi Hotta Copyright © 2016 Masaki Nakaya et al. All rights reserved. A Review on Epoxy and Polyester Based Polymer Concrete and Exploration of Polyfurfuryl Alcohol as Polymer Concrete Thu, 16 Jun 2016 09:54:09 +0000 Petroleum based epoxy and polyester based thermoset resins can be used to produce high-quality polymer concrete. However, petroleum based resources are finite and this has necessitated the development of thermoset bioresins to be used as polymer concrete. Furfuryl alcohol (FA), a thermoset bioresin, is derived from lignocellulosic biomass and it can be polymerized into polyfurfuryl alcohol (PFA) in the presence of an acid catalyst. The highly exothermic polymerization reactions involving conversion of FA to PFA can be used to fabricate PFA based concrete with rock-like structure. The PFA based polymer concrete offers the broadest range of chemical resistance against acid and alkali over all other types of polymer concrete which are based upon different thermoset polymeric systems. In this review paper, we have discussed the formulations (incorporation of aggregates, fillers, and resin) and properties (especially compressive and flexural) of epoxy and polyester based polymer concrete. In another section, we have given the mechanical, thermal, and water resistance properties of PFA based biopolymer, biocomposites, nanocomposites, and polymer concrete. Lastly, we have tried to explore whether PFA can be used successfully as biopolymer concrete or not. Rakesh Kumar Copyright © 2016 Rakesh Kumar. All rights reserved. Optimal Catalyst and Cocatalyst Precontacting in Industrial Ethylene Copolymerization Processes Thu, 05 May 2016 12:56:27 +0000 In industrial-scale catalytic olefin copolymerization processes, catalyst and cocatalyst precontacting before being introduced in the polymerization reactor is of profound significance in terms of catalyst kinetics and morphology control. The precontacting process takes place under either well-mixing (e.g., static mixers) or plug-flow (e.g., pipes) conditions. The scope of this work is to study the influence of mixing on catalyst/cocatalyst precontacting for a heterogeneous Ziegler-Natta catalyst system under different polymerization conditions. Slurry ethylene homopolymerization and ethylene copolymerization experiments with 1-butene are performed in a 0.5 L reactor. In addition, the effect of several key parameters (e.g., precontacting time, and ethylene/hydrogen concentration) on catalyst activity is analyzed. Moreover, a comprehensive mass transfer model is employed to provide insight on the mass transfer process and support the experimental findings. The model is capable of assessing the external and internal mass transfer limitations during catalyst/cocatalyst precontacting process. It is shown that catalyst/cocatalyst precontacting is very important for the catalyst activation as well as for the overall catalyst kinetic behavior. The study reveals that there is an optimum precontacting time before and after which the catalyst activity decreases, while this optimum time depends on the precontacting mixing conditions. Paul Aigner, Christian Paulik, Apostolos Krallis, and Vasileios Kanellopoulos Copyright © 2016 Paul Aigner et al. All rights reserved. Highly Accelerated Aging Method for Poly(ethylene terephthalate) Film Using Xenon Lamp with Heating System Thu, 21 Apr 2016 14:18:21 +0000 PET films were degraded at temperature higher than 100°C with steam and xenon light by using the newly developed system. Degradation products obtained using the proposed and conventional systems were essentially the same, as indicated by the similar increase in the intensity of the carbonyl peak near 1685 cm−1 in the FT-IR spectra of irradiated specimens and spectrum of original PET film. Elastic moduli derived from the stress-strain (SS) curves obtained in tensile tests were almost the same in the case of the proposed and conventional systems and were independent of the heating temperature, light intensity, and irradiation time. Tensile strength of degraded PET films decreases with increasing heating temperature. Tensile strengths of PET films degraded at same temperature decrease linearly with increasing intensity of xenon light. The lifetime at 90% strength of PET films was calculated. Attempts were made to express this lifetime as functions of the light intensity and the reciprocal of the absolute temperature by using the Eyring model. Estimated lifetime 15.9 h of tensile test using Eyring model for PET film agreed with the lifetime 22.7 h derived from data measured using the xenon weather meter. Masahiro Funabashi, Fumi Ninomiya, Akihiro Oishi, Akihiko Ouchi, Hideaki Hagihara, Hiroyuki Suda, and Masao Kunioka Copyright © 2016 Masahiro Funabashi et al. All rights reserved. Intramolecular Lactonization of Poly(α-hydroxyacrylic acid): Kinetics and Reaction Mechanism Mon, 28 Sep 2015 07:39:16 +0000 Poly(α-hydroxyacrylic acid), PHA, is one of the few polymers with biodegradable properties used in mechanical pulp bleaching to stabilize hydrogen peroxide. A new method for the in situ follow-up of the lactone ring formation of PHA has been developed. The results have further been applied to describe the reaction kinetics of the lactonization and hydrolysis reactions through parameter estimation. In addition, the reaction mechanism is elucidated by multivariate data analysis. Satisfactory identification and semiquantitative separation of the lactone ring as well as the acyclic (carboxyl and hydroxyl groups) forms have been established by 1H NMR in the pH range of 1–9. The lactonization reaction approaching equilibrium can be described by pseudo-first-order kinetics in the pH range of 1–6. The rate constants of the pseudo-first-order kinetic model have been estimated by nonlinear regression. Due to the very low rates of lactonization as well as the weak pH dependency of the reaction, an addition-elimination mechanism is proposed. Additionally, the presence of a transient reaction intermediate during lactonization reaction could be identified by subjecting the measurement data to multivariate data analysis (PCA, principal component analysis). A good correlation was found between the kinetic and the PCA models in terms of model validity. Heli Virkki, Antti Vuori, and Tapani Vuorinen Copyright © 2015 Heli Virkki et al. All rights reserved. Thin Polymer Layers with Superparamagnetic Properties Mon, 21 Sep 2015 06:53:35 +0000 Superparamagnetic particles were widely used in medical applications as well as for magnetic sensors and actuators. Generally, the size of the particles is in the range of 10–20 nm. To use such particles in large-scale applications, a simple processing as well as the use of commercially available particles is required. Therefore superparamagnetic nanoparticles available on the market were incorporated in flexible polymer films and the magnetic properties of the films were investigated. At ambient temperature no significant hysteresis was observed, indicating the superparamagnetic properties. Films containing up to 25% nanoparticles were prepared. The films show a saturation magnetization of 13.8 Am2/kg and a coercivity of 7 Oe at ambient temperature. Kristin Trommer, Carina Petzold, and Bernd Morgenstern Copyright © 2015 Kristin Trommer et al. All rights reserved. Understanding the Morphological Changes in the Polypropylene/Polyamide 6 Fifty/Fifty Blends by Interfacial Modifiers Based on Grafted Atactic Polypropylenes: Microscopic, Mechanical, and Thermal Characterization Sun, 20 Sep 2015 07:12:09 +0000 The main aim of the present work is to correlate the morphological changes observed in the modified PP/PA6 fifty/fifty blends molded at confined flow conditions with both their mechanical and thermal properties and the kind and the amount of the interfacial modifiers used. Both transmitted light optical microscopy in the positive phase contrast mode, PC TOM, and field emission scanning electronic microscopy, FE SEM, were the used techniques for, respectively, general morphology overview and fractures surface analysis. The interfacial modifiers, a succinic anhydride, aPP-SA, and a succinyl-fluorescein, aPP-SF/SA, grafted atactic polypropylenes obtained and well characterized in authors’ laboratories came from the chemical modification of an atactic polypropylene industrial by-product. The amounts of any of both the interfacial modifiers came coded by the Box-Wilson experiment design methodology applied to the overall PP/PA6 binary system, watching that the interfacial agent was not a third component on a ternary blend but a true interfacial modifier in a binary one. All the studies were carried out over suitable specimens according to each test procedure with no further material manipulations to preserve at any moment the morphology of the blends as they emerge from the compression molding step at confined flow conditions. E. P. Collar, J. Taranco, S. Areso, and Jesús María García-Martínez Copyright © 2015 E. P. Collar et al. All rights reserved. Potential Application of a Visible Light-Induced Photocured Hydrogel Film as a Wound Dressing Material Mon, 24 Aug 2015 07:43:27 +0000 The objective of this work was to prepare hydrogel films, as semi-interpenetrating polymer networks (semi-IPN), based on polyethylene glycol-co-fumarate (PEGF) and chitosan (Ch) blends. Hydrogel films were prepared by free radical cross-linking of PEGF, an unsaturated aliphatic polyester, in the presence of N-vinyl pyrrolidone (NVP), camphorquinone (CQ), and N,N-dimethyl-p-toluidine (DMPT) as a cross-linking, photoinitiating, and accelerating agent, respectively. The effect of NVP concentration on physicochemical and biological properties of semi-IPN film properties was evaluated. The sol fraction, water vapor transmission rate, and swelling degree of the hydrogel films were also investigated. Antibacterial activity against S. aureus was observed for the photocured blend hydrogels of Ch/PEGF with no toxicity to L929 cells according to the cell viability assays. Blend hydrogel films showing 600 ± 88% of equilibrium swelling degree in water and the lowest sol fraction (3.14 ± 1.22%) were obtained at 20 wt% of NVP content whilst preserving their own cytocompatibility and antibacterial activity. Therefore, this formulation was considered as an optimal semi-IPN blend hydrogel film composition with potential application for wound dressing. Aazadehsadat Hashemi Doulabi, Hamid Mirzadeh, Nasrin Samadi, Shadab Bagheri-Khoulenjani, Mohammad Atai, and Mohammad Imani Copyright © 2015 Aazadehsadat Hashemi Doulabi et al. All rights reserved. Peanut Husk Filled Polyethylene Composites: Effects of Filler Content and Compatibilizer on Properties Sun, 23 Aug 2015 07:43:19 +0000 Agrowaste biocomposites were obtained using peanut husk filler and LDPE. The effects of agrofiller content and compatibilizer on the mechanical and biodegradable properties of the composites have been discussed. Mechanical and biodegradable behaviour of LDPE became noticeably worse when it was blended with agrofiller, due to poor compatibility between the two phases. The presence of MAPE in the composites and its compatibility with the agrofiller, led to much better dispersion and homogeneity of agrofiller in the matrix and consequently to improved properties. Water absorption and thickness swelling indices increased with increasing filler content and were reduced on addition of MAPE. Furthermore, weight loss of composites via enzymatic degradation showed that both composites were biodegradable even at high levels of filler addition. However, composites with MAPE exhibited lower weight loss. Henry C. Obasi Copyright © 2015 Henry C. Obasi. All rights reserved. Dielectric and AC Conductivity Studies in PPy-Ag Nanocomposites Sun, 16 Aug 2015 13:39:24 +0000 Polypyrrole and silver nanoparticles have been synthesized at 277 K by chemical route. Nanoparticles of polypyrrole-silver (PPy-Ag) composites were prepared by mixing polypyrrole and silver nanoparticles in different weight percentages. Dielectric properties as a function of temperature in the range from 300 K to 550 K and frequency in the range from 50 Hz to 1 MHz have been measured. Dielectric constant decreased with increase in frequency and temperature. Dielectric loss decreased with increase in frequency and increased with increase in temperature. Using dielectric data AC conductivity has been determined. Conductivity was found to be in the order of 10−3 (Ω−1 m−1) and it increased with increase in temperature. Temperature variation of conductivity data has been analyzed in the light of Mott’s polaron hopping model. Activation energy for conduction has been determined. Activation energy was determined to be in the order of meV and it has increased with increase in frequency and Ag nanoparticles content. This is the first time that PPy-Ag nanocomposites have been investigated for dielectric properties and AC conductivity and data analyzed thoroughly. K. Praveenkumar, T. Sankarappa, J. S. Ashwajeet, and R. Ramanna Copyright © 2015 K. Praveenkumar et al. All rights reserved. Self-Healing Hydrogels Based on Carboxymethyl Chitosan and Acryloyl-6-aminocaproic Acid Mon, 10 Aug 2015 11:48:30 +0000 Once cracks have formed within hydrogel materials, the integrity of the structure is signifcantly compromised, regardless of the application. Here, we demonstrate cross-linked CMCS hydrogels can be engineered to exhibit self-healing under mild conditions. CMCS hydrogels based on CMCS and acryloyl-6-aminocaproic acid (A6ACA) were synthesized by free radical aqueous copolymerization using ammonium persulfate as initiator. A series of hydrogels was synthesized varying the percentage of A6ACA. The hydrogels were characterized by Fourier transform infrared spectroscopy (FTIR) techniques and their morphologies were investigated by scanning electron microscope (SEM) images. When the proportion of A6ACA was increased, the compressive strength, stress, and strain of hydrogels were increased. The cross-linked hydrogel based on CMCS that can autonomously heal between cut surfaces after 1 h was formed under mild conditions. The increase of A6ACA content in the hydrogels will lead to increased mechanical properties and mechanical healing efficiencies for highly cross-linked polymeric networks. Hydrogen bond is the main reason for self-healing ability, and the covalent cross-linkss and noncovalent cross-links both bear loads in the hyrogel. Polymers with the ability to self-repair after sustaining damage could extend the lifetime of materials used in many applications. Jiufang Duan Copyright © 2015 Jiufang Duan. All rights reserved. Study of Antioxidant Effectiveness of Kraft Lignin in HDPE Mon, 03 Aug 2015 11:13:20 +0000 Polymers are subject to oxidative degradation during all steps of their useful cycle. This degradative process is prevented using stabilizers like antioxidant of the type sterically hindered phenols or amines. Lignin, due to the presence of phenolic groups in their structure, can present characteristic as antioxidant agent, in a similar way to the additives used in polymers. Therefore, in this work, the antioxidant capacity of the lignin in a sample of polyethylene is studied. For this reason, in this paper, a method based on nonisothermal differential scanning calorimetry (DSC) to evaluate this property is used. The samples studied were subjected to heat treatment at different scan rates and in presence of oxygen to promote thermooxidation of the material. The antioxidant capacity of different formulations of lignin and additives in the polymer resin was determined from the temperature of onset of oxidation () at different heating rates and adjusting Arrhenius model prediction. The results indicate that the procedure can predict the antioxidant capacity of antioxidant additives in HDPE with good reproducibility and accuracy, according to the Arrhenius model prediction. I. Piña, F. Ysambertt, D. Perez, and K. Lopez Copyright © 2015 I. Piña et al. All rights reserved. Preparation and Antiflame Performance of Expandable Graphite Modified with Sodium Hexametaphosphate Mon, 27 Jul 2015 13:35:26 +0000 A kind of polyphosphate modified expandable graphite (EGp) was prepared in graphite oxidation and intercalation reaction with KMnO4 as oxidant, H2SO4 as intercalator, and sodium hexametaphosphate (SHMP) as assistant intercalator. The feasible mass ratio of C : KMnO4 : H2SO4 (98%) : SHMP was determined as 1.0 : 0.3 : 4.5 : 0.6, H2SO4 was diluted to 77 wt% before intercalation reaction, and the reaction lasted for 40 min at 40°C. Expanded volume and initial expansion temperature of the prepared EGp reached 600 mL/g (at 800°C) and 151°C, respectively. X-ray diffraction spectroscopy testified the intercalation and layer structure of EGp, and Fourier transform infrared spectroscopy illuminated the intercalated functional groups. Flame retardance of the prepared EGp and the referenced EG (with only H2SO4 as intercalator) for linear low density polyethylene (LLDPE) was also investigated. Addition of 30 wt% EGp to the polymer improved the limiting oxygen index (LOI) from 17.5 to 27.3%. On the other hand, the LOI of the same amount of the referenced EG was only 24.6%. Assistant intercalation of SHMP improved the dilatability and flame retardancy. Hongmei Zhao, Xiuyan Pang, and Zhixiao Zhai Copyright © 2015 Hongmei Zhao et al. All rights reserved. Oxidative Coupling Copolymerization of 2,6-Dimethylphenol and Dihydroxynaphthalene Affording Poly(phenylene oxide) Derivatives Thu, 16 Jul 2015 10:40:59 +0000 The oxidative coupling copolymerization between 2,6-dimethylphenol (DMP) and dihydroxynaphthalenes, such as the 2,3- and 2,6-dihydroxynaphthalenes (2,3- and 2,6-DHN), was carried out using a Cu catalyst under an O2 atmosphere. The polymerization was significantly affected by the structure of the comonomer, and the copolymers were efficiently obtained during the copolymerization of DMP and 2,6-DHN. The obtained copolymers containing hydroxyl groups of the DHN unit were further transformed into polymers containing ester and urethane groups. The obtained copolymers containing various functional groups showed a very different solubility from that of the homopolymer of DMP. Shigeki Habaue, Ryosuke Ito, Ken Okumura, and Yuki Takamushi Copyright © 2015 Shigeki Habaue et al. All rights reserved. Model for Charge Transport in Ferroelectric Nanocomposite Film Mon, 23 Mar 2015 08:42:21 +0000 This paper describes 3D particle-in-cell simulation of charge injection and transport through nanocomposite film comprised of ferroelectric ceramic nanofillers in an amorphous polymer matrix and/or semicrystalline ferroelectric polymer with varying degrees of crystallinity. The classical electrical double layer model for a monopolar core is extended to represent the nanofiller/nanocrystallite by replacing it with a dipolar core. Charge injection at the electrodes assumes metal-polymer Schottky emission at low to moderate fields and Fowler-Nordheim tunneling at high fields. Injected particles propagate via field-dependent Poole-Frenkel mobility. The simulation algorithm uses a boundary integral equation method for solution of the Poisson equation coupled with a second-order predictor-corrector scheme for robust time integration of the equations of motion. The stability criterion of the explicit algorithm conforms to the Courant-Friedrichs-Levy limit assuring robust and rapid convergence. Simulation results for BaTiO3 nanofiller in amorphous polymer matrix and semicrystalline PVDF with varying degrees of crystallinity indicate that charge transport behavior depends on nanoparticle polarization with antiparallel orientation showing the highest conduction and therefore the lowest level of charge trapping in the interaction zone. Charge attachment to nanofillers and nanocrystallites increases with vol% loading or degree of crystallinity and saturates at 30–40 vol% for the set of simulation parameters. Meng H. Lean and Wei-Ping L. Chu Copyright © 2015 Meng H. Lean and Wei-Ping L. Chu. All rights reserved. Cyclic Oligolactic Acid in Direct Polycondensation PLLA and Its Extraction with Organic Solvent Tue, 25 Nov 2014 11:16:57 +0000 The contents of poly(L-lactic acid) (PLLA) prepared by direct condensation polymerization without using a catalyst were studied. 1H NMR and mass spectrometry analyses suggested that PLLA contained cyclic oligo(L-lactic acid) (c-OLLA) with 3–20 repeat units. Notably, only c-OLLA was extracted and isolated using hexane or cyclohexane at 4°C; thus the hydrophobicity, topology, and temperature dependence of the solubility of the obtained PLLA enabled the selective extraction of c-OLLA. The effect of cyclic compounds on direct polycondensation and the potential for c-OLLA to form molecular inclusion complexes were also discussed. Keiichiro Nomura, Yuta Nakatsuchi, Ryugo Shinmura, Sommai Pivsa-Art, Weraporn Pivsa-Art, Yuji Aso, and Hitomi Ohara Copyright © 2014 Keiichiro Nomura et al. All rights reserved. Kinetic Studies on Saponification of Poly(ethylene terephthalate) Waste Powder Using Conductivity Measurements Mon, 25 Aug 2014 09:15:45 +0000 Conductometric measurement technique has been deployed to study the kinetic behavior during the reaction of poly(ethylene terepthalate) (PET) and NaOH. A laboratory made arrangement with facility of continuous stirring was used to carry out experiments at desired temperature. With conductometry, the determination of kinetic as well as thermodynamic parameters becomes more simple and faster as compared to gravimetry. Chemical kinetics of this reaction shows that it is a second order reaction with reaction rate constant  g−1 s−1 at 70°C. The specific reaction rates of the saponification reaction in the temperature range at various temperatures (50–80°C) were determined. From the data, thermodynamic parameters such as activation energy, Arrhenius constant (frequency factor), activation enthalpy, activation entropy, and free energy of activation obtained were 54.2 KJ g−1,  min−1, 90.8 KJ g−1, 126.5 JK−1 g−1, and 49.9 KJ g−1, respectively. Dilip B. Patil, Vijendra Batra, and Sushil B. Kapoor Copyright © 2014 Dilip B. Patil et al. All rights reserved. The Effects of Antioxidants Content on Mechanical Properties and Water Absorption Behaviour of Biocomposites Prepared by Single Screw Extrusion Process Wed, 04 Jun 2014 12:03:53 +0000 The performance of hybrid fillers between rice husk and sawdust filled recycled high density polyethylene (rHDPE) with the presence of antioxidants (IRGANOX 1010 and IRGAFOS 169, with the ratio of 1 : 1) was investigated. The biocomposites with 30 wt% of matrix and around 70 wt% of hybrid fillers (rice husk and sawdust) and different antioxidants’ contents (0 to 0.7 wt%) were prepared with single screw extruder. Increasing the amount of antioxidants in biocomposites reduced the modulus of elasticity and modulus of rupture on flexural testing. The addition of antioxidants increased the tensile and impact strength of biocomposites. From the study, samples with 0.5 wt% of antioxidants produce the most reasonable strength and elasticity of biocomposites. Furthermore, the effect of antioxidants content on water uptake was minimal. This might be caused by the enhanced interfacial bonding between the polymer matrix and hybrid fillers, as shown from the morphology by using scanning electron microscopy (SEM). Mohd Hafizuddin Ab Ghani, Mohd Nazry Salleh, Ruey Shan Chen, Sahrim Ahmad, Mohd Rashid Yusof Hamid, Ismail Hanafi, and Nishata Royan Rajendran Royan Copyright © 2014 Mohd Hafizuddin Ab Ghani et al. All rights reserved. Edible Polymers: Challenges and Opportunities Mon, 05 May 2014 13:09:35 +0000 Edible polymers have established substantial deliberation in modern eons because of their benefits comprising use as edible materials over synthetic polymers. This could contribute to the reduction of environmental contamination. Edible polymers can practically diminish the complexity and thus improve the recyclability of materials, compared to the more traditional non-environmentally friendly materials and may be able to substitute such synthetic polymers. A synthetic hydrogel polymer unlocked a new possibility for development of films, coatings, extrudable pellets, and synthetic nanopolymers, particularly designed for medical, agricultural, and industrial fields. Edible polymers offer many advantages for delivering drugs and tissue engineering. Edible polymer technology helps food industries to make their products more attractive and safe to use. Novel edible materials have been derived from many natural sources that have conventionally been regarded as discarded materials. The objective of this review is to provide a comprehensive introduction to edible polymers by providing descriptions in terms of their origin, properties, and potential uses. Subhas C. Shit and Pathik M. Shah Copyright © 2014 Subhas C. Shit and Pathik M. Shah. All rights reserved.