bluuebunny/crossref_metadata_2025 huggingface dataset:
Curing Study of a Toughened Epoxy System Using the Dynamic Torsional Vibration Method
Authors: Dazhu Chen , Fang Yuan , Pingsheng He , Jiasheng Qian
Published: September 2018

Epoxy resins are widely used as adhesives or as the matrix of high-performance composites and the monitoring for quality of their cure process is of great interest. In this paper, the cure kinetics of an epoxy/polyamide system was successfully studied using the dynamic torsional vibration method (DTVM) by measuring the change in mechanical properties (torque) during the cure. The experimental data were analyzed by the non-equilibrium thermodynamic fluctuation theory and the Avrami method. The results from dynamic mechanical thermal analysis (DMTA) reveal that the fully cured specimens of epoxy resin/polyamide exist in the rubbery plateau state at the applied cure temperature. With increasing cure temperature, the equilibrium torque drops, the gel time decreases and the cure reaction takes less time to complete. After the gel point, the same curing mechanism occurs at various cure temperatures. The effect of increasing hardener concentration on the rate of cross-linking at a given cure temperature was also examined. Excess polyamide increases the number of cross-linking points, and hence enlarges the Avrami exponent n.
Polyamide-6/Clay Nanocomposites: A Critical Review
Authors: Gupta Bhuvanesh , Lacrampe Marie-France , Krawczak Patricia
Published: September 2018

The plastics business is gathering around nanocomposites because of the unusual performance of these materials in some technologically important applications, such as automotive parts, packaging, textiles and flame resistant materials. The use of clay as the reinforcing component of polymers has transformed the properties of the resultant materials. These nanocomposites are regarded as futuristic. However the science of clay-polymer interaction is still a subject of intense investigation. The industrialization of nanocomposites is accelerating and efforts are being made to achieve still better performance by optimising of their compounding and processing conditions. Nanocomposites based on many different polymers have been, or are being developed. The current scenario in relation to polyamide-6/clay nanocomposites is presented in this article. Preparation, processing and application issues are addressed in particular.
Effect of Processing Parameters on the Size and Size Distribution of High Molecular Weight Atactic Poly(vinyl alcohol) Gel Particles Prepared by Water-in-Oil Emulsion Method Using High Pressure Homogenizer
Authors: Lyoo Won Seok , Cho Soo Hyeok , Shin Dong Soo , Han Sung Soo , Park Chan Sik , Kim Jae Hyun , Noh Seok Kyun
Published: September 2018

To produce high molecular weight poly(vinyl alcohol) (PVA) particles with various sizes for biomedical applications such as embolic treatment and as matrices for drug delivery systems, vinyl acetate was bulk-polymerized using 2,2-azobis(2,4-dimethyl valeronitrile) and the corresponding atactic PVA (a-PVA) was obtained by the saponification of poly(vinyl acetate). Then a-PVA particles were prepared by a series of processes, forming fine water-in-oil (W/O) emulsions using a high pressure homogenizer, with precipitation in ethanol, freezing and thawing, and drying. The effects of the agitation speed of the homogenizer, homogenizing time, and the oil content on droplet size, droplet size distribution, and the morphologies of the solid particles were studied. The droplet sizes shifted to smaller values with increasing agitation speeds and with decreasing oil contents. In addition, novel ketoprofen-loaded a-PVA particles were obtained using the same method adopted for the preparation of the particles. The release behaviour of ketoprofen from a-PVA particles was examined by high performance liquid chromatography.
Composite from Wood Fibres Bonded with Renewable Wood Resin
Authors: Ghosh Arun , Sain Mohoni
Published: September 2018

This paper shows the efficiency of a renewable wood resin as a binder for wood fibres in the manufacture of environmentally friendly fibreboard composites. The wood resin was nevertheless partially replaced by urea formaldehyde (UF) resin to make fibreboards more economical and performance-driven. The results demonstrate that nearly all the mechanical properties of the fibreboards were above the minimum requirements specified in the ANSI-AHA standard.

The mechanical properties of wood resin bonded fibreboard were inferior to those of the UF resin bonded equivalents. The horizontal density profiles of the composites revealed that the wood resin distribution in the wood fibres could be optimised in presence of liquid UF resin. Wood resin bonded fibreboard showed a lower rate of formaldehyde emission than UF resin bonded fibreboard. The curing conditions were also optimised to achieve improved mechanical performance and dimensional stability for the composite fibreboards.
Predicting the Elastic Modulus of Hybrid Fibre Reinforced Thermoplastics
Authors: Facca Angelo G. , Kortschot Mark T. , Yan Ning
Published: September 2018

Hybrid fibre reinforced thermoplastics (containing more than one type of fibre) offer several design possibilities that do not exist with single fibre reinforced systems. Although there are extensive experimental data available in the literature on a variety of hybrid systems, a reliable and simple analytical model to predict the stiffness of these composites is not available. In this study, a modification of the hybrid rule of mixtures equation is developed to determine the stiffness properties of hybrid composites. Experimental data from single fibre reinforced thermoplastics forms the basis of the modification. Combinations of E-glass, hemp and hardwood flour were blended into high-density polyethylene in total fibre loadings of 10 to 60wt% to produce hybrid composites. The density and Young's modulus of the hybrid composites fell between the extreme values obtained for the single fibre composites. The modified rule of hybrid mixtures equation was found to adequately predict the tensile modulus of the hybrid composites.
Toughening of Polycarbonate with Organic-Inorganic Hybrid Materials
Authors: Zhang Zhiyi , Zhao Ning , Wei Wei , Wu Dong , Sun Yuhan
Published: September 2018

Polycarbonate (PC) was modified with organic-inorganic nanostructured acrylate polymer and its tensile and impact properties were studied. The PC alloys exhibited higher flexibility than pure PC and the tensile strength hardly decreased with the addition of the modifiers. The SEM results indicated that the inorganic particles and the acrylic ester polymer were all dispersed in the PC matrix forming a co-continuous phase.
Finite Element Simulation on Thermoforming Acrylic Sheets Using Dynamic Explicit Method
Authors: Dong Y. , Lin R.J.T. , Bhattacharyya D.
Published: September 2018

After optimising the critical material parameters obtained from hot tensile tests, a dynamic explicit software package, PAM-FORM™, is used to simulate the thermoforming process of polymeric sheet. A hyperelastic constitutive law based on the Mooney-Rivlin model has been successfully adopted to carry out the initial simulation on bubble inflation and to identify the material parameters. It has shown a good agreement of the deformation profile with the experimental results. In this paper, further investigations are concentrated on the thickness distribution analysis and the strain states of the bubble inflation along with a comparison to the results from kinematic Grid Strain Analysis (GSA). The numerical simulation of pressure forming of a cup, whose forming mechanisms have been explained reasonably well with the available Williams’ analytical solutions, is also presented. For a more academic case, the adaptive mesh refinement scheme has been employed in the simulation of thermoforming a complex-shaped rectangular container to well predict the wall thickness distribution. The final simulation results of the deformation at different stages of forming process and the analyses of final part geometry are also presented.
Study on Morphology and Structure of Dynamically Cured PP/MAH-g-POE/Epoxy Blends
Authors: Jiang Xueliang , Zhou Aijun , Yuan Jun
Published: September 2018

A method of simultaneous reinforcing and toughening of polypropylene (PP) was reported. Dynamic cure of the epoxy resin was successfully applied in the PP/maleic anhydride-grafted ethylene-octene copolymer (MAH-g-POE) blends, and the obtained blends named as dynamically cured PP/MAH-g-POE/epoxy blends. The smaller size of the epoxy particle in the PP/MAH-g-POE/epoxy blends shows that MAH-g-POE was also used as a compatibilizer. The structure of the dynamically cured PP/MAH-g-POE/epoxy blends embedded the epoxy particles by the MAH-g-POE. The stiffness and toughness of dynamically cured PP/MAH-g-POE/epoxy blends were in good balance. The cured epoxy particles as organic filler increased the stiffness of the PP/MAH-g-POE blends, and the improvement in the toughness was attributed to the embedded structure in the blends. The tensile strength and flexural modulus of the blends increased with increasing the epoxy resin content, and the impact strength reaches a maximum of 378 J/m at the epoxy resin content of 10 wt.%. Thermogravimetric analysis results showed that the incorporation of MAH-g-POE into the PP could reduce the thermal stability of PP, but the addition of epoxy resin could improve the thermal stability of PP, the dynamically cured PP/MAH-g-POE/epoxy blends had good thermal stability when compared to PP.
Dynamic Mechanical Behaviour of Banana-pseudostem-filled Unplasticised Polyvinyl Chloride Composites
Authors: Zainudin E.S. , Sapuan S.M. , Abdan K. , Mohamad M.T.M.
Published: September 2018

The dynamic mechanical behaviour of unplasticized polyvinyl chloride (UPVC) and its composites reinforced with banana pseudostem (BPS) fibres has been studied, with special reference to the effect of filler loading and temperature. Dynamic properties such as the storage modulus (E’) and damping behaviour (tan d) were evaluated as a function of BPS volume fraction. It was found that the storage modulus increased with increasing BPS content in the samples. At lower temperatures (in the glassy region), the E’ values of the samples were highest in both unmodified and acrylic-modified BPS/UPVC composites with 40% fibres. The glass transition temperature (Tg) associated with the damping peaks of BPS/UPVC composites reached its highest value at 94.9 °C with 20% fibre loading for unmodified BPS/UPVC composites, whereas, in the case of acrylic-modified composites, CA4 had the highest Tg at 98.7 °C.
A Study of PU/MMT Nanocomposites
Authors: Qiao Min , Ran Qianping , Wu Shishan , Shen Jian
Published: September 2018

The polyurethane (PU)/montmorillonite (MMT) composite prepared by in situ polymerization was a sort of intercalated nanocomposite. The silicate platelets were dispersed in the PU matrix on the nanoscale. The N,N-dimethylformamide (DMF) suspension containing the PU/MMT nanocomposite was stable for a long time, and the silicate platelets did not subside. With an increasing content of silicate, the tensile and tear strength of the PU/MMT nanocomposite increased, but the rate of increase diminished. Compared with that of pure PU, the temperature of initial weight loss of the PU/MMT nanocomposite in the first step decreased because of the acid catalytic action of the protonated silicate platelets, but the temperature of initial weight loss in the second step increased due to the barrier effect of the silicate platelets and the strong interfacial interaction between silicate platelets and the molecular chains of PU.
Effect of Swelling Process on Monodispersity of Porous Polystyrene-Divinylbenzene Microspheres Prepared by Two-step Swelling Polymerization Methods
Authors: Liao Xiaoyan , Cheng Jiang , Li Lu , Pi Pihui , Wen Xiufang , Yang Zhuoru
Published: September 2018

Porous polystyrene-divinylbenzene (PS-DVB) microspheres of narrow size distribution in the size range of 3.9–4.4 μm were prepared by two-step swelling polymerization methods. Effects of swelling conditions such as swelling activator, temperature, the way of dispersion and dibutyl phthalate (DBP)/seed particle ratio on particle size distribution of the PS-DVB microspheres were investigated in detail. Optimal swelling conditions for the preparation of uniformly sized polystyrene particles have been found as follows: swelling activation agent was dibutyl phthalate (DBP), swelling temperature was 35 °C, dispersion manner was ultrasonic assistant magnetic dispersion, DBP/seed particle ratio was 1–1.5 ml·g-1. It was found that particle size distribution became narrower and swelling time was shortened from more than 24 h to 10 h with the introduction of ultrasonic dispersion, which was attribute to the cavitation effect of ultrasonic and the huge magnetic field action arising therefrom, speeding up the equilibrium of swelling process. Swelling temperature also has significant effect on the monodispersity and particles with the best uniformity could be achieved with the temperature at 35 °C. The possible reason is that process of seed particles absorbing swelling agent through water phase is an equilibrium course of thermodynamics and kinetics.
Preparation of High Molecular Weight Poly(vinyl carbazole) Web by Electrospinning
Authors: Kim Hee Sam , Lee Ki Bum , Lyoo Won Seok
Published: September 2018

High molecular weight poly(N-vinyl carbazole) (PVCz) webs were obtained by the electrospinning technique. PVCz solutions were prepared by dissolving PVCz in chloroform and were spun under various electrospinning conditions. Especially, to improve the spinnability of PVCz, a high molecular weight specimen was adopted. Effects of processing parameters such as solution concentration, applied voltage, and tip–to-collector distance (TCD) on the spinnability, shape, and diameter and uniformity of fibres in the web were investigated. The average diameter of fibres in the webs was about 5 μm. The higher the solution concentration, the voltage, and the TCD, the finer and more uniform were the fibres in the web. PVCz fibres in webs prepared at high initial solution concentration were not cylindrical but planar, similar to “ribbons” but with nano-sized pores.
Influence of Fillers in Stiffener Core and Structural Parameters on Compaction of T-Stiffened Skins in Autoclave Process
Authors: Li Min , Wang Xueming , Xie Fuyuan , Zhang Zuoguang
Published: September 2018

Using carbon fibre/bismaleimide unidirectional prepregs, T-stiffened skins were fabricated by integral moulding technology of co-bonding in autoclave. The research was focused on comparing the effects of different filler content and structural parameters (curvature and ply sequence considered) on the compaction of T-stiffened skins. The measurement thickness and observation of micrographs were used to characterise the consolidation and compaction of T-stiffeners, and the experimental results indicated that filler content and structural parameters were both significant factors. A non-uniform thickness distribution and thickening at the corner section of T-stiffeners were observed. For T-stiffeners with quasi-isotropic lay-up, more uniform thickness distribution was obtained under the conditions of rolling unidirectional prepregs as fillers into stiffener core and increasing curvature radius, which could help to compact T-stiffeners and eliminate rich resin defect. The results provided in this study will contribute to understanding of the fracture mechanism of T-stiffened skins.
Utilisation of Potato Leaves and Organophilic Montmorillonite for the Preparation of Superabsorbent Composite under Microwave Irradiation
Authors: Wang Yun-Pu , Liang Yan , Chen Jiu-Cun , Yan Xiao-Dong , Li Cheng-Lin , Wang Xi-Ping
Published: September 2018

A novel superabsorbent composite from potato leaves (PL, a kind of agricultural waste materials), organophilic montmorillonite (OMMT), acrylic acid (AA) and acrylamide (AM), PL-g-P(AA-AM)/OMMT, was synthesised by microwave irradiation, using potassium persulfate (KPS) as the initiator and N,N′-methylenebisacrylamide (MBA) as the crosslinker. The polymerisation conditions were investigated by orthogonal tests, and the optimal conditions were determined. The superabsorbent composites were characterised by FTIR, XRD, and TGA, the results show that AA and AM successfully grafted onto the PL chain, the layers of OMMT were exfoliated and dispersed in the composite after copolymerisation. The introduction of PL in the composite slightly increased the water absorbency. And the thermal stability, water absorbency, water retention and swelling rate of the superabsorbent composite were also improved by the introduction of 5% OMMM into the PL-g-P (AA-AM) network. The use of a microwave irradiation method not only greatly enhanced the reaction rate, but also increased the water absorbance over the conventional method. All of the results indicated that this new approach showed promise in utilising such waste in the production of useful products, which are economical and environment-friendly.
Tailoring of Teflon-Fep Film through Graft-Copolymerization with Polar Monomers for Desalination Processes: Effect of Swift Heavy Ion Irradiation
Authors: Kaur Inderjeet , Rattan Sunita , Chauhan Sandeep , Gupta Nitika
Published: September 2018

In the present communication we report on the grafting of 4-vinyl pyridine (4-VP) and methacrylic acid (MAAc) onto Teflon-FEP film by a preirradiation method to synthesize ionic membranes. Optimum conditions pertaining to maximum percentage of grafting were evaluated as a function of different reaction parameters. Maximum percentage of grafting of 4-VP (13.66%) was obtained at an optimum total dose of 58.3 kGy at [4-VP] = 1.9 moles/L while MAAc produced 66.40% of maximum grafting at optimum conditions of 39.74 kGy total dose using [MAAc] = 2.5 moles/L in 10 ml of water. Effect of dose rate on grafting of 4-VP has also been discussed. The optimum conditions were used to graft 4-VP and MAAc onto Teflon-FEP film irradiated at different fluence with Swift heavy ions (SHIs). Better grafting of 4-VP was obtained in the SHI irradiated films while MAAc produced lower grafting. The membranes were characterized by FTIR spectroscopy, scanning electron microscopy and thermo gravimetric analysis. Swelling studies of the membranes were performed in different polar solvents such as water, ethanol (EtOH), dimethyl sulphoxide (DMSO) and dimethyl formamide (DMF). Teflon-FEP-g-poly(4-VP) showed maximum swelling in water whereas in case of Teflon-FEP-g-poly (MAAc), maximum swelling was observed in DMSO. Conductance measurements in aqueous sodium chloride solution showed that these membranes have an affinity for Na+ ions and Cl- ions and hence can be used in desalination processes for the separation of ions.
Tracing the Void Content Development and Identification of its Effecting Parameters during in Situ Consolidation of Thermoplastic Tape Material
Authors: Khan Muhammad Amir , Mitschang Peter , Schledjewski Ralf
Published: September 2018

One of the ways to identify the quality of structures made from fibre-reinforced thermoplastic material is by examining its void content percentage. Significant improvement in mechanical properties can be achieved by minimising it. The purpose of this work was to develop a simulation tool from existing available model in literature, to trace out the void development inside the laminate during the manufacturing and identification of major influencing process parameter. The effects of consolidating force, process velocity, hot gas flow in the heating region, and repetitive passes were investigated through simulation. A series of experiments was carried out on several AS4/PEEK laminated plates manufactured by automatic tape placement process. Simulated void distribution through thickness and density were compared with measured values to trace the effecting input parameters. Thickness build-up with successive lay-ups is also monitored online and the average thickness lies in close proximity to the predicted range. Major influencing process parameters were identified.
Isothermal Crystallization Kinetics of Tricomponent Blends of Polycarbonate, Poly(Trimethylene Terephthalate) and Polybutylene Terephthalate
Authors: Al-Mulla Adam , Al-Omairi Lafi , Mathew Johnson , Bhattacharya Sathi
Published: September 2018

The isothermal crystallization kinetics of two different types of linear aromatic polyesters, namely poly(trimethylene terephthalate) (PTT), poly(butylene terephthalate) (PBT) and their blend with polycarbonate (PC) has been investigated using differential scanning calorimetry (DSC). The blend composed of PTT25/PBT25/PC50 (wt/wt.%) was synthesized using a twin screw extruder. Isothermal studies for PTT were conducted between 129 and 159 °C. The temperature ranged between 168–177 °C for PBT and between 170 and 183 °C for the blend. Avrami, Tobin and Malkin models were used to estimate the crystallization kinetic parameters, such as crystallization rate order (n), crystallization rate constant (k) and half time of crystallization (t0.5). The values of average sum of square of errors (ASE) of all models were comparable. This detailed study indicates that the models investigated are suitable for describing the crystallization kinetics of the blend and the neat polymers.
Mechanical and Surface Properties of E-beam Irradiated Polytetrafluoroethylene-Silicone Rubber Composites
Authors: Dadbin Susan , Kashcooli Yaser , Frounchi Masoud
Published: September 2018

Compounding electron beam irradiated polytetrafluoroethylene (PTFE or Teflon) powder with silicone rubber produced silicone rubber/PTFE composites with desired physical properties.

PTFE powder was exposed to electron beam irradiation at various doses and characterized by FTIR, DSC and contact angle measurements. Irradiation of PTFE with high energy electron beam induced chain scission reactions. Irradiated PTFE showed higher degree of crystallization and lower melting point with increasing absorbed dose. Number average molecular weight of irradiated PTFE was reduced significantly at higher absorbed doses. Formation of polar groups on the surface of irradiated PTFE powder was detected by FTIR spectroscopy. The latter was also verified by measurements of water-drop contact angle, which decreased with increasing absorbed dose.

Mechanical and surface properties of the composites of silicone rubber and PTFE were characterized by tensile strength, abrasion resistance and water drop contact angle measurements. All the composites containing 5–15 phr PTFE showed higher tensile strength compared to the silicone rubber. Irradiation of PTFE powder had a significant effect on improving the abrasion resistance of the silicone rubber upon addition of only 5 phr irradiated PTFE. Similar abrasion resistance was obtained with the addition of higher amounts of non-irradiated PTFE (15 phr). Water drop contact angle of the composites decreased slightly with increasing the absorbed dose of PTFE.
Interfacial Shear Strength in a Metal-Thermoplastic Composite
Authors: Putman Carol Ochoa , Vaidya Uday K.
Published: September 2018

Hybrid materials featuring thermoplastic polymer composites in conjunction with steel cords are being considered as structural materials in infrastructure, transportation and military applications. The present study focuses on understanding the mechanical performance of metal cord-thermoplastic composites. Since the optimal performance of a composite strongly depends on the behavior of the interface, finite element modeling has been adopted to characterize the interface between steel fibers and thermoplastic composite material. The mechanical interactions between thermoplastics and steel have been studied with a goal to improve interfacial shear strength and cohesive strength. Steel cord was combined with nylon, polypropylene, soft thermoplastic polyurethane and hard thermoplastic polyurethane to find the parameters that affect mechanical bonding via pull out tests and friction coefficient tests. The test parameters have been correlated to interfacial shear strength using both experimental and modeling approach.
Structure and Thermal Properties of Co-polyamide (CPA)/Clay Nanocomposites by a Melting Extrusion Method
Authors: Zhao Shuaijiang , She Xilin , Li Hailing , Yuan Fang , Zhou Di
Published: September 2018

The aim of the work was to study the structure and thermal property of co-polyamide (CPA)/clay nanocomposites. Two nanocomposites, based on two co-polyamides (CPA) and organic-clay, were successfully prepared by melting extrusions in a twin-screw extruder with high aspect ratio back-whorl. Their morphology and thermal properties were characterized by transmission electron microscopy (TEM), different scanning calorimeter (DSC). TEM results showed that the layered silicate sheets with the thickness of about 15 nm dispersed homogeneously in the polymeric matrix and formed exfoliated layered silicate nanocomposites. DSC results revealed that the crystallization rate increased due to the addition of 2.0 wt.% clay into CPA.
An Aromatic Macromolecule as a Nano Drug Carrier: Polyether Dendrimer / Poly(2-hydroxyethyl methacrylate)
Authors: Saboktakin Mohammad Reza , Tabatabaie Roya M. , Maharramov Abel , Ramazanov Mohammad Ali
Published: September 2018

Highly branched, functionalized polymers have the potential to act as efficient drug carrier systems. The aromatic polyether dendrimers are spherical, highly ordered, multibranched, nanometre-sized macromolecules having positively charged ether groups on the surface under physiological conditions. In this study, we have synthesized a kind of dendrimer/poly(2-hydroxy ethyl methacrylate) nanocomposite/5-aminosalicylic acid (5-ASA) for oral drug delivery. The aromatic polyether dendrimer (generation 2, hyperbranched polyether with -CH2OH functionality, 3,5-Dihydroxybenzoic acid core) was prepared from generation 2, hyperbranched polyether dendrimer with -COOCH3 form in excellent yield. FT-IR, 1H-NMR and DSC studies suggest that the monomer predominantly forms a complex with polyether dendrimers because of the interaction between the –CH2OH end groups of dendrimer and the –OH group of 2-hydroxyethyl methacrylate monomer.
Epoxidized Palm Oil Plasticized Polylactic Acid/Fatty Nitrogen Compound Modified Clay Nanocomposites: Preparation and Characterization
Authors: Al-Mulla Emad A. Jaffar , Zin Wan Yunus Wan Md. , Bt Ibrahim Nor Azowa , Ab. Rahman Mohamad Zaki
Published: September 2018

Fatty nitrogen compounds (FNCs); fatty amides (FAs), fatty hydroxamic acids (FHAs), and N,N′-carbonyl difatty amides (CDFAs), which were synthesized from palm oil, have been used as organic compounds to modify a natural clay (sodium montmorillonite). The clay modification was carried out by stirring the clay particles in an aqueous solution of FAs, FHAs, or CDFAs by which the clay layer distance increased from 1.23 to 2.69, 2.89 and 3.21 nm, respectively. The modified clay was then used in the preparation of the epoxidized palm oil (EPO) plasticized polylactic acid (PLA) nanocomposites. The interaction of the modifier in the clay layer was characterized by X-ray diffractometry (XRD) and Fourier transform infrared spectroscopy (FTIR). Elemental analysis was used to estimate the presence of these FNCs in the clay. The nanocomposites were synthesized by solution casting of the modified clay and a PLA/EPO blend at the weight ratio of 80/20, which has the highest elongation at break. The nanocomposites were then characterized using XRD, transmission electron microscopy (TEM), thermogravimetric analysis (TGA), and tensile properties measurements. The XRD and TEM results confirmed the production of nanocomposites. PLA/EPO modified clay nanocomposites show higher thermal stability and significant improvement of mechanical properties in comparison with those of the PLA/EPO blend.
Effect of Solvent on the Morphology of High Molecular Weight Poly(N-vinyl carbazole) Web Prepared by Electrospinning
Authors: Kim Hee Sam , Kee Ki Bum , Lee Young Jae , Han Sung Soo , Chung Yong Sik , Jeon Han Yong , Lee Yong Rok , Gal Yeong Soon , Noh Seok Kyun , Lyoo Won Seok
Published: September 2018

The effects of solvents such as 1,1,2,2-tetrachloroethane (TCE) and tetrahydrofuran (THF) and other processing parameters of electrospinning on the spinnability of high molecular weight poly(N-vinyl carbazole) (PVCz) solution and morphological variations of the as-spun PVCz web were investigated. That is, electrospun PVCz webs with various dimensions and shapes were obtained by controlling the type and amount of solvent and processing parameters like applied voltage, tip to the collector distance, and solution concentration. In the cases of all parameters, the average diameter of fibres in PVCz web electrospun in TCE was finer than that in THF. In addition, minimum diameters of fibres were about 900 nm and 3 μ m for TCE and THF, respectively. In THF, PVCz fibres at high initial polymer concentration were not cylindrical but planar, which were similar with “ribbon” and nano-sized pores, resulting from the differences in evaporation rates and in the viscosities of the solvent and the solutions.
Synthesis and Characterization of N-(carboxy-methylthioureido)-Chitosan and its Dispersion Capability
Authors: Liu J. , Wu Y. min , Nie Z. Li
Published: September 2018

Water-soluble N-carboxymethylthioureidochitosan (CMTC) was synthesized by the reaction between chitosan (CTS) and ammonium thiocyanate and chloroacetic acid in a hydrochloric acid aqueous solution. The modified product was confirmed by Fourier transform infrared (FTIR) spectrometry, X-ray diffractometry (XRD) and thermal analysis. The results showed that new functional groups had been linked to amino groups of CTS molecules, and the product was more amorphous than CTS. The dispersion stability of CMTC was examined with a sedimentation test of 1 wt.% kaolin suspension in test tubes, under different concentrations and different pH. The results indicated that CMTC may be applicable for use as a novel stabilizer in neutral solution in which the concentration of CMTC is 0.5% or 1%.
The Influence of the Extrusion Temperature on the Mechanical Properties of MMT Filled PA 6 Composite
Authors: Mészáros L. , Oláh L. , Ronkay F. , Czvikovszky T.
Published: September 2018

Effects of varying extrusion temperatures on the mechanical properties of polyamide 6 (PA 6) matrix montmorillonite (MMT) filled composites were investigated in this paper. Five different temperature programs were used for producing composites with 1 wt.% nanoparticles content. The mechanical properties were evaluated by tensile and flexural tests and SEM pictures were taken from the fracture surfaces. X-ray diffraction patterns were also measured to obtain some information about the structures of the materials. The results showed that the lower extrusion temperatures resulted in better mechanical properties of the composite.
Theoretical and Experimental Investigation on Helium Leakage Characterization of Flexible Film-Fabric Laminated Composites
Authors: Yao Xue Feng , Wu Qing , Xiong Chao , Wen Pin Jing , Tan Hui Feng
Published: September 2018

Flexible film-fabric laminated composites with low-density and high-performance are important envelope materials in stratosphere aerostats. In this paper, a multilayer leak model is used to predict the helium leak rate of the virgin samples by the Fick's law, which shows a good agreement with experimental data. The influences of mechanical damage, ultraviolet radiation and intense ozone corrosion on the Young's modulus and the permeability of envelop materials are investigated in experiment, which are confirmed by means of damage-induced helium leakage models. Finally, helium leakage mechanisms of flexible film-fabric laminated composites are analyzed.
Effect of Interfacial Modifiers on Physical Properties and Flammability Properties of PE/Wood Composites
Authors: Haoqun Hong , Tao Liu , Hui He , Demin Jia , Haiyan Zhang
Published: September 2018

The ternary-monomer graft copolymers of polyethylene (GPE) were used as interfacial modifiers for recycled polyethylene (rPE)/wood flour (WF) composites. How the interfacial modifiers and WF processing methods affected the mechanical properties, thermal stability and flammability properties of the composites were investigated. Results show that the steam-braising on WF could increase the mechanical properties of the composites. The interfacial modifiers were excellent compatilizers for the rPE/WF composites that significantly increased the mechanical properties of the composites. Wood flour acted as charring agent during the combustion of the composites to improve the flame retardancy of PE/wood flour composites. Due to the improved interface compatibility between rPE and WF by GPE, the rPE/WF composites maintained excellent mechanical properties and flame retardancy even at higher filler content.
Morphology and Properties of Polypropylene Blends Containing Phenolic Resin Produced from the Liquefaction of Empty Fruit Bunch Fibres
Authors: Chai Lee-Lee , Chia Chin-Hua , Zakaria Sarani , Nabihah Sharifah , Rasid Rozaidi
Published: September 2018

Phenol formaldehyde (PF) resin prepared from phenol-liquefied empty fruit bunch (EFB) fibres was blended with polypropylene (PP) using a co-rotating twin-screw extruder. The effects of the PF content (10, 20, 30 and 40 wt.%) blended with PP on the properties of the PP/PF board were investigated. SEM images depicted the formation of spherical protuberances and voids in the PP/PF board with the increasing PF content. The size of the protuberances was also increased with the PF content. The formation of void could be due to the release of water, ammonia and formaldehyde during the blending and hot-press processes. The density, moisture content and maximum water absorption of the PP/PF board increased with the increase of PF content. The TG curves of the PP/PF boards revealed that the PF and PP in the PP/PF board decomposed at different temperature ranges, i.e., 200–420 and 425–480 °C, respectively. The addition of PF to PP reduced the activation energy of the first stage thermal decomposition of the PP/PF boards. The addition of 10 wt.% PF was the optimum content to produce PP/PF board with optimum mechanical properties.
Kinetics for Grafting of Acrylic Acid onto Chlorinated Polypropylene
Authors: Fu Heqing , Lai Wangting , Wang Lina , Yan Caibin
Published: September 2018

Acrylic acid (AA) grafting onto chlorinated polypropylene (CPP) was carried out using toluene as solvent and benzoyl peroxide (BPO) as initiator by free radical polymerization. The effects of reaction temperature, concentration of acrylic acid monomer and benzoyl peroxide initiator on the rate of graft polymerization were studied. The rate of graft polymerization depended on the initiator and monomer concentrations. The actual rate constant of graft polymerization was found to obey the Arrhenius law and the activation energy E value was 40.6 kJ/mol. The kinetic equation for the grafting of acrylic acid onto chlorinated polypropylene was R = K [BPO] [AA]0.62.
Modification of an Injectable Chitosan Scaffold by Blending with NaHCO3 to Improve Cytocompatibility
Authors: Huang Zhi , Yu Bo , Feng Qingling , Li Songjian
Published: September 2018

The chitosan/β-glycerophosphate (C/GP) system, which allows injection at room temperature and gel-formation at body temperature, can be considered as a candidate for injectable scaffolds. To improve the cytocompatiblity of the C/GPhydrogel, we used NaHCO3 as buffer to neutralize chitosan solution and lower the GP concentration from 400 to 135 mM. The chitosan/β-glycerophosphate//NaHCO3 (C/GP/NaHCO3) system was liquid before injection and became a three-dimensional porous hydrogel at body temperature, as revealed by scanning electron microscopy (SEM). The C/GP/NaHCO3 hydrogels showed higher cytocompatibility with rat bone marrow-derived mesenchymal stem cells (rBMSCs) in vitro compared to C/GP hydrogels. Our results indicated that the C/GP/NaHCO3 system was suitable as an injectable scaffold for tissue engineering.
Anisotropic Thermal Characteristics of Graphene-Embedded Polyimide Composite Sheets
Authors: Park Seong-Yeob , Bae Jong-Seong , Kim Jin-Gyu , Oh Min-Wook , Kim Jungsoo , Nam Dae-Geun , Yeum Jeong Hyun , Oh Weontae
Published: September 2018

Polyimide-graphene (PIG) composites were prepared, and their thermal properties were characterized as films or sheets. Graphene loadings were controlled up to 8 wt.% or 12 wt.% in their composites. The graphenes used in this work were prepared by the chemical treatment of graphite. The as-prepared polyimide-graphene composites were thermally characterized in films or sheets. The thermal conductivities of the PIG sheets were separately analyzed in both in-plane and out-of-plane directions. The thermal expansion coefficients (TECs) of the PIG composites slightly changed with the amount of graphene added to the composites. The in-plane thermal conductivities were higher than the out-of-plane thermal conductivities, and the thermal conductivities of both directions proportionally increased with the graphene loadings in the PIG composites. The temperature-dependent stresses of the composite films monotonically decreased with the graphene loadings. The experimentally obtained thermal characteristics of the polyimide-graphene composites were compared and discussed on the basis of the composite morphologies.
The Effect of Montmorillonite Modification on Crystallization Behaviour of Polypropylene/Montmorillonite Composites
Authors: Yang Zhihong , Wu Minghu , Chen Gang , Li Shengjuan , Peng Panpan , Zhang Qiaolian
Published: September 2018

This paper reports the preparation of organic montmorillonite (OMMT) modified by octadecylamine and polypropylene/montmorillonite (PP/MMT) composites produced by the method of melt compounding. The effect of MMT modification degree on the crystallization behaviour of PP was emphasized by X-ray diffraction (XRD), polarizing optical microscopy and differential scanning calorimetry (DSC). Interlayer d-spacings of 3.02 nm, 1.27 nm and 2.59 nm were detected for MMT modified by octadecylamine, Titivate coupling agent and commercial OMMT, respectively. The spherulite size and the crystallinity of the composite decreased and the number of spherulites increased with the interlayer spacing of OMMT. The values of t1/2 and F(T) for PP crystallisation decreased with the interlayer spacing at a given cooling rate or a given relative crystallinity degree, indicating that MMT with a larger gallery height could accelerate the crystallization rate of PP more efficiently. Moreover, the composites containing OMMT modified by octadecylamine exhibited better mechanical properties in comparison to those incorporating OMMT modified by Titivate coupling agent and commercial OMMT, indicating that primary amine was one of the best potential surfactants for MMT modification. It was concluded that full modification of OMMT by octadecylamine was more beneficial to the crystallization of PP and hence caused a positive effect on the mechanical properties of the composites.
Techno-Economic Feasibility Study of New Concept for Build-Up of Local Load Specific Reinforced Hybrid Structures
Authors: Holschuh Renέ , Becker David , Mitschang Peter
Published: September 2018

This article describes a new process approach, based on a combination of thermoforming and in-situ tape placement for the build-up of locally load-related, reinforced multi-material-systems based on polymer-polymer-hybrids. The process is evaluated and compared with state-of-the-art technologies.

A techno-economic analysis is presented for a case study, considering the cost-efficiency throughout the complete development in a process-based and stepwise differentiation approach. Compared to other competing concepts the novel concept offers the potential for reducing the unit costs at large-scale production scenarios.
Tensile Properties Study of E-Glass/Epoxy Laminate and π/4 Quasi-Isotropic E-Glass/Epoxy Laminate
Authors: Gopalakrishnan M. , Muthu S. , Subramanian R. , Santhanakrishnan R. , Karthigeyan L.M.
Published: September 2018

The usage of composites has increased in various fields, including automotive and aerospace, due to their high strength-to-weight ratio. The optimum use of composite material is also being studied to bring down the fuel costs and carbon emissions to atmosphere. The concept of optimum usage of composite material could be applied at the initial design stage or when repairing damaged composite structures. This paper describes preliminary work towards the optimum usage of π/4 quasi-isotropic E-glass/epoxy laminate repair practices, and it demonstrates the procedure followed to determine their tensile properties. This work used unidirectional fibre (UDF) laminae and UDF laminate specimens to understand the tensile properties of UDF E-glass/epoxy laminate. This paper provides a unique comparison between experimental results of UDF laminae and UDF laminate level. The tensile properties obtained from UDF laminae and UDF laminate were suitably used to derive [A][B][D] matrices of π/4 quasi-isotropic laminates, so as to understand whether the laminates were pertaining to the quasi-isotropic category. Finally, π/4 quasi-isotropic laminates with the above-mentioned codes were tested to understand the tensile properties. The derived properties could be suitably used for future work on quasi-isotropic E-glass/epoxy composite laminate repair practices.
Polymer Sheet Hot Incremental Forming - an Innovative Polymer Forming Approach
Authors: Sridhar R. , Rajenthirakumar D.
Published: September 2018

Polymers are currently used as raw materials in automobile and house hold applications. Particularly in automobile parts polymers having significant percentage, because of its strength to weight ratio. But their conventional processing of heating- melting -injecting and solidifying process cycle is mainly suitable for high volume mass production1. Increasing demands for the products with low volume, best quality, less production lead time are impart the need for a new polymer processing method. This can be capable of fulfilling the current industrial requirement of agile manufacturing processing methods with short span for life cycle of parts and short design to production lead time.

This paper is mainly focused on problems in conventional polymer processing and proves the opportunity to use single point incremental forming technology which is currently used for sheet metal forming applications. This method reduces and eliminates capital investment on special dies and tools. It is a highly flexible forming process and is enabled with the help of computer numerical control (CNC) technology2. In this work, a novel process namely hot incremental polymer forming (HIPF) is developed. In this process the material is heated with the help of heating element up to the required temperature and the hemispherical tool moves over the hot sheet, the tool path is controlled by CNC technology.

This innovative process starts with development of low cost fixture and spherical tool, heating coil, temperature measurement device, feedback element and temperature controller. A truncated hexagonal pyramid shape is used to study the process capability regarding the geometrical accuracy and sheet thinning of the produced part. Results show that this method capable of forming polymer sheet parts at elevated temperature with good dimensional accuracy and better formability.
Solvent Effect on the Fabrication and Mechanical Behavior of Sandwich Structured Poly(vinyl alcohol)/Carbon-nanofiber Buckypaper Composite
Authors: Lu M. , Sun S.C. , Bu Z.X. , Wang L.S. , Sun L.
Published: September 2018

A solution-casting method has been developed to fabricate polymer/carbon nanofiber (CNF) buckypaper composite/polymer sandwich structures. Such layered nanocomposites can take advantage of the buckypaper's mechanical reinforcement effect and to introduce multi-functionalities including dynamic damping, electrical/thermal conductance and electromechanical responses. By controlling the solution chemistry, the structure, morphology and thus the performances of the composite samples were effectively manipulated. Dimethyl sulfoxide (DMSO) as a solvent was found to greatly enhance the wettability of polyvinyl alcohol (PVA) to carbon nanofiber as compared to water, and it increased polymer penetration in the buckypaper. It was also observed that PVA formed a surface coating layer surrounding individual CNF which behaved differently from bulk polymer. This intermediate layer played a critical role in determining the static mechanical reinforcement effect of buckypaper and further affected the composite dynamic damping characteristics. Incorporating carbon nanofiber buckypaper not only strengthened the PVA static mechanical performance but also lowered the loss modulus and tan d. By introducing the controlled structure of such composite sandwiches, it is possible to tailor the multi-functionalities targeting specific applications.
Preparation, Characterization and Application of Polyaniline/silk Fibroin Composite
Authors: Ahmad Sharique , Sultan Adil , Raza Waseem , Muneer M. , Mohammad Faiz
Published: September 2018

We report the electrical properties and photocatalytic activity of polyaniline (Pani) and polyaniline/silk fibroin (Pani/SF) composite. The Pani/SF composite has been synthesized first time by chemical oxidative in-situ polymerization method by using potassium persulphate (K2S2O8) in an acidic medium. Thus prepared Pani and Pani/SF composite were characterized by using Fourier-transform infrared spectroscopy, x-ray diffraction, thermogravimetric analysis and scanning electron microscopy. The stability in terms of the DC electrical conductivity of Pani/SF composite and Pani was investigated under isothermal and cyclic aging conditions. Results indicated that the electrical properties of the composite were significantly influenced by the loading of SF to Pani and observed to be more thermally stable than those of Pani. As-prepared Pani and Pani/SF composites were studied for the degradation of methylene blue (MB) and Rhodamine B (RhB) under UV-light irradiations. The results showed that 91.4% & 85.4% degradation of RhB and MB takes place respectively after 90 min over Pani/SF composite. The decomposition rate of composite was 1.8-2.2 times greater than that of Pani. The improvement of photocatalytic activity of composite may be attributed to the electron-sink function of silk fibroin which increases the optical absorption property and separation of photogenerated charge carriers than Pani alone.
Postdisaster Politics: New Lessons from New Orleans
Authors: Montjoy Robert S. , Chervenak Edward E.
Published: September 2018

How do disasters affect voting? A series of postdisaster studies have sought to answer this question using a retrospective framework through which voters deviate from normal patterns of political support (measured by votes or attitudes) to punish or reward officials for their performance, or lack thereof. Here, we argue that the political effects of disasters can last longer than and be qualitatively different from reactions to the original disaster because postdisaster recoveries generate their own issues, to which voters may respond prospectively, and retrospectively. Local communities affected by disasters are likely sites for this effect because their citizens experience the consequences of a disaster more directly and for longer periods than do national audiences. The case of New Orleans after Hurricane Katrina demonstrates this point. Where most studies of postdisaster politics use partisanship as the baseline against which to measure change, we use race because that has been the overriding division in New Orleans. We show that local political effects of Katrina were much more complex and longer lasting than have been found in prior research based on the retrospective model. In the years following the storm, voters changed the pattern of race-based voting for mayoral candidates, approved major governmental reforms, and responded to prospective issues in their evaluation of the incumbent mayor.