bluuebunny/crossref_metadata_2025 huggingface dataset:
Fatigue Behaviour of Multilayer Braided Fabric Reinforced Laminates
Authors: Huang Zheng-Ming , Teng X. C. , Ramakrishna S.
Published: September 2018

In this paper, the fatigue behaviour of the laminated composites made from an epoxy matrix and four layers of flat regular braided carbon fiber fabrics of different braiding angles was investigated experimentally. Three laminate lay-ups were used. They are: [100/100/100/100], [280/100/100/280], and [280/280/280/280], where 100 within the bracket indicates that the single layer braid lamina had a braiding angle of 100 inclined with the longitudinal (loading) direction. The static tensile and tension-tension fatigue tests were conducted for those laminates, and detailed fatigue data are reported in the paper. Failure mechanisms of the tested laminates were also characterized. The stiffnesses and strengths (including static tensile and fatigue strengths) of the [100/100/100/100], [280/100/100/280], and [280/280/280/280] laminates were the highest, intermediate, and the lowest respectively. However, different failure mechanisms were recognized. It was found that under the uniaxial tensile or a high-level fatigue load, the [280/280/280/280] laminate failed catastrophically as a result of fiber breakage nearly across the cross section of the specimen. Delamination was seen only when a low-level fatigue load was applied to the laminate. In the case of the [100/100/100/100] laminate, a laminate longitudinal splitting was the main failure mode. No delamination accompanied the laminate failure. For the [280/100/100/280] laminate, significant delamination was found with any applied load (whether static or tensile fatigue of any load level). Splitting, both across the cross-sectional breakage and longitudinal, were involved in the failure of this combined laminate. These findings provide a useful insight into understanding the fatigue behaviour of braided fabric reinforced laminates.
Polypropylene/Ethylene-Octene Copolymer/Organic-Montmorillonite Nanocomposites
Authors: Guo Minyan , Zhou Xiaodong , Dai Gance , Hu Fuzeng
Published: September 2018

Melt compounding was employed to prepare polypropylene (PP)/ethylene-octene copolymer (POE)/organic-montmorillonite (OMMT) nanocomposites. Polypropylene grafted with maleic anhydride (MPP) was added as a compatibilising agent. Analyses by wide-angle X-ray diffraction, transmission electron microscopy and scanning electron microscopy indicated that polymer chains intercalated into OMMT and that some of the OMMT delaminated into nano-layers dispersed in the PP matrix. Mechanical tests showed that the addition of POE increases the toughness of PP, but it decreases the stiffness. When OMMT and MPP were added, the toughness of PP increased greatly and the stiffness was not changed profoundly. Differential scanning calorimetry was used to study the melt and crystallization behavior of the composites. The results indicate that OMMT and MPP act as effective nucleating agents.
Synthesis, Characterization and Properties of SiO2-Polyimide Hybrid Film
Authors: Zhang C.H. , Zhang Z.Q. , Li Q.Y. , Cao H.L.
Published: September 2018

A polyamic acid (PAA) solution with a solids content of approximately 15 wt% was synthesized by reacting pyromellitic dianhydride with 4,4'–diaminodiphenyl methane in N-methyl-2-pyrrolidone through a ring-opening polyaddition. A nano-SiO2 precursor was also synthesized from tetraethoxysilane (TEOS) via a sol-gel process. SiO2-polyimide (SiO2-PI) hybrid films were then successfully prepared. The polyimide (PI) film and the SiO2-PI hybrid films were characterized by FT-IR, XPS and SEM. The FT-IR spectra showed that PAA became imidized completely after a heat treatment process. The analyses by FT-IR, XPS and SEM confirmed that most of the TEOS had changed into nanoscale SiO2 particles, distributed homogeneously in the PI matrix. Nano-indenter XP was employed to detect the nano-indentation harness and nano-indentation modulus of the films. The results indicated that the mechanical properties of the SiO2-PI hybrid films were better than those of PI film, and the SiO2 content of the SiO2-PI hybrid films had an obvious effect on their nano-indentation properties. When the SiO2 content was 5 wt%, the maximum values of the nano-indentation hardness and nano-indentation modulus were 0.870 GPa and 6.974 GPa, respectively. TGA evidence suggested that the thermal stability of the SiO2-PI hybrid film was better than that of PI film, and the thermal decomposition temperature was increased from 547.8 oC to 567.5 oC.
Sorption of Aromatic Hydrocarbons into Styrene Butadiene Rubber/Poly(ethylene-co-vinyl acetate) Blends
Authors: Radhakrishnan C.K. , Ganesh B. , Sujith A. , Unnikrishnan G. , Thomas Sabu
Published: September 2018

Benzene, toluene and xylene sorption by styrene-butadiene rubber/poly (ethylene-co-vinyl acetate) (SBR/EVA) blends in the temperature range of 26-56 °C have been investigated. The blends were vulcanised by three different systems viz. sulphur, dicumyl peroxide and a mixed system of sulphur and peroxide. The effects of various parameters such as blend composition, vulcanising systems, crosslink density, penetrant molecule size, and temperature on the sorption parameters were studied. Blends with higher EVA contents, vulcanised by the peroxide system, were found to exhibit the lowest interaction with the solvents. The mechanism of sorption deviated regularly from the normal Fickian behaviour, found for conventional elastomers, with increase in EVA content. The molecular mass between crosslinks, kinetic rate constant, transport coefficients and related thermodynamic parameters have been computed to complement the experimental observations. The experimental results have been compared with different theoretical predictions.
Thermoforming Complex Parts from Unconsolidated and Consolidated Polypropylene/Glass Fibre Fabrics
Authors: Trudel-Boucher David , Fisa Bo , Denault Johanne , Gagnon Patrick
Published: September 2018

Thermoforming of unconsolidated and consolidated polypropylene/glass fibre fabrics was studied for two mould geometries, i.e. a square mould and a mould with three studs. The principal objective of this study was to evaluate the feasibility of direct thermoforming of unconsolidated fabrics in complex moulds, since this process offers the potential of reducing the cost of the raw material by eliminating the separate consolidation step performed prior to moulding. In this work, the unconsolidated and consolidated fabrics plies were heated in a convection oven and then quickly transferred to a press to be simultaneously conformed and (re-)consolidated using a rubber punch and a metal cavity. Results show that similar product quality (evaluated by the void content) can be obtained with unconsolidated and consolidated fabrics once conformation to the mould shape is achieved. A minimal forming temperature of 215 °C is required to achieve conformation to the mould shape, while minimal forming pressures of 2 and 3 MPa must be applied to achieve the same objective for the consolidated and unconsolidated fabric, respectively. Increasing the punch hardness, varying the fabric orientation and increasing the number of vents could reduce the pressure necessary to produce conformation to the mould shape.
Mechanical and Thermal Properties of Oil Palm Empty Fruit Bunch-Filled Unplasticized Poly (Vinyl Chloride) Composites
Authors: Bakar A. Abu , Hassan A. , Yusof A.F. Mohd
Published: September 2018

Awareness of the advantages of natural fibres has stimulated interest in their use to reinforce polymers. One type of natural fibre that is of great relevance to Malaysia is oil palm empty fruit bunches (EFB). To produce EFB-filled unplasticized poly(vinyl chloride) (PVC) composites, PVC resin and the various additives were first dry-blended using a laboratory blender before being milled into sheets on a two-roll mill. Test specimens were then hot pressed, after which the mechanical and thermal properties were determined. Four untreated EFB fibre contents were employed, 10, 20, 30 and 40 phr. The increase in EFB fibre content resulted in an improvement in flexural modulus at the expense of impact strength and flexural strength. The incorporation of EFB slightly enhanced the glass transition temperature but it decreased the thermal stability of the composites, evidenced by a decrease in decomposition temperature and a change in the degradation process from two to three stages.
Silver Ion Release from Polymethyl Methacrylate Silver Nanocomposites
Authors: Damm Cornelia
Published: September 2018

Polymethyl methacrylate (PMMA) silver nanocomposites were prepared by the thermal reduction of silver(I) trifluoroacetate. Transmission electron microscopic investigations reveal that the silver nanoparticles were spherical and their particle sizes were between 5 nm and 50 nm. The particles were distributed randomly in the PMMA matrix.

Immersion of the nanocomposites in water led to a release of silver ions.

The silver ion release from the PMMA silver nanocomposites was measured by anodic stripping voltammetry.

When a nanocomposite sample having a surface area of 36.8 cm2 and a silver content of 0.12 wt% was immersed in water, the silver ion concentration in the surrounding water was about 0.05 mg/l after two days. This is sufficient to kill bacteria. Using conventional silver powder as a filler, a silver content 30 times higher is necessary to achieve the same silver ion concentration in the surrounding water under the same conditions.

The silver ion concentration in the water increased with increasing nanosilver content of the composites.

The composites incorporating conventional silver powder are not transparent. In contrast, PMMA silver nanocomposites containing less than 0.25 wt% silver show a translucency sufficient for use in packaging materials.
EMI Shielding Effectiveness of Copper/Epoxy Composites
Authors: Wetherhold Robert C. , McManaman Joseph M.
Published: September 2018

Samples of shaped and treated copper (Cu) fibre/brittle matrix composites have been fabricated with a variety of fibre shapes, treatments, diameters, and powder inclusions and tested for shielding effectiveness (SE) using the ASTM standard D4935-99 method over the frequency range 200 to 1500 MHz. A small amount of nickel (Ni) powder was included in some specimens to evaluate the effect of magnetic permeability on SE. Most tests were conducted at constant (15 vol%, “v%”) fibre volume fraction. Results show that a smaller fibre diameter results in significant SE improvements. SE was also substantially improved by relatively minor fibre shaping (which changes along the fibre length) or by fine-scale roughening via chemical treatment.

Addition of small amounts of Cu powder leads to major improvements in SE. Most of the improvements are presumably due to the establishment of conductive networks, although fibre shaping or treatment allows greater scattering and thus more internal reflections with attendant absorption. The smaller diameter fibres consistently gave better SE. When a continuous fibre mesh was used, high SE resulted, showing the dominance of fibre connectivity for such materials; the surface condition of the mesh is relatively unimportant. The improvements in SE can be achieved with essentially identical mechanical properties, leading to an effective multifunctional material, although most of the SE values achieved so far are modest. Ni powder results in overall improvement in SE as well as a cyclic dependence of SE on frequency, which indicates phase interference at a scale of particle size not previously seen.
Image Analysis of Elastomer Morphology in Toughened Thermoplastic and Thermoset Resins
Authors: Cañavate J. , Carrasco F. , Pagès P. , Colom X.
Published: September 2018

A thermoplastic polystyrene-based material with styrene-butadiene-styrene dispersed particles and a thermoset polyester toughened with butadiene-acrylonitrile particles were studied. Photomicrographs of materials that had different proportions of elastomer were processed and the images analysed. The changes in the morphological characteristics were correlated with the fracture toughness and modulus of elasticity.
Thermal Stability and Flame Retardancy of Polypropylene with Phosphorus, Nitrogen and Silicon-Containing Compounds
Authors: Li Qiang , Jiang Pingkai , Su Zhanpai , Wei Ping
Published: September 2018

Flame retardants containing phosphorus, nitrogen and silicone elements have been synthesized. The thermal stabilities of polypropylene (PP), PSiN and PP/PSiN have been studied by thermogravimetric (TG) analysis in nitrogen, air and oxygen atmospheres. The initial decomposition temperature (IDT), maximum-rate degradation temperature (Tmax), integral procedure decomposition temperature (IPDT) and char yield at 800 °C in various atmospheres have been investigated.

Although the IDT of PP was reduced by the introduction of PSiN, the Tmax, IPDT and char yield were all increased. The flame retardancy of PP/PSiN composites were evaluated by measuring their Limiting Oxygen Index (LOI) values. Their thermal stabilities agreed with the results of the flame retardancy tests: the PP/PSiN-A exhibited good flame retardancy with LOI of 26.0 and its char yields at 800 °C were 27 wt.% (in nitrogen), 12 wt.% (air) and 12 wt.% (in oxygen). The activation energies of PP, PSiN and PP/PSiN composites in various atmospheres were calculated using the method of Horowitz-Metzger.
The Construction and Analysis of a Prediction Model for Combining the Taguchi Method and General Regression Neural Network for Injection Moulding
Authors: Jeffrey Kuo Chung-Feng , Li Yung-Chang , Wu Yi-Shiuan
Published: September 2018

Plastics always show mould deformation after the injection moulding process and this can cause dimensional errors. The extent of a dimensional error can be controlled effectively by choosing adequate processing parameters. The target of this work was to reduce the dimensional error in the hexagonal screw diameter when processing polyether ether ketone (PEEK), and to improve the polymer's quality. First, we selected the factor levels according to the chosen quality characteristics. We decided that a prediction model for the injection process could be constructed using the Taguchi quality method and a general regression neural network (GRNN). The optimum conditions determined by the Taguchi method can be modified by the neural network. The injection moulding product can achieve a reduced dimensional error by adjusting the factor levels using this combined approach.
Crystallization Behaviour and Mechanical Properties of Polypropylene Copolymer/Silicon Dioxide Nanocomposites
Authors: Chen Minjie , Zhang Yong , Wan Chaoying , Zhang Yinxi
Published: September 2018

Polypropylene copolymer (co-PP)/silicon dioxide (SiO2) nanocomposites were prepared by melt extrusion in a twin-screw extruder. The isothermal crystallization behaviour of co-PP/SiO2 composites was investigated by differential scanning calorimetry. The SiO2 restricted the mobility of the co-PP molecular chains and retarded the crystallization of the co-PP component in the co-PP/SiO2 composites. A small amount of SiO2 (3 phr) could increase the tensile strength and elongation at break of the co-PP/SiO2 composites, and a high loading of SiO2 could decrease the tensile strength and elongation at break. Results of thermogravimetric analysis indicated that a small amount of SiO2 could greatly improve the thermal stability.
Torsion Transmission Capacity of a Hybrid Aluminum/Composite Driveshaft
Authors: Mutasher S.A. , Sapuan S.M. , Sahari B.B. , Hamouda A.M.S.
Published: September 2018

Experiments were carried out to study the static torsion capability of a hybrid aluminum/ composite drive shaft. A hybrid shaft was fabricated using a wetted filament winding method by winding glass and carbon fibres onto aluminum tube with different winding angles, numbers of layers and stacking sequence. The torque-angle-of-twist response was obtained and the failure modes of the hybrid shaft were studied. The results show that the static torque capacity for a winding angle of 45o is larger than it is for 90o, for both glass and carbon fibres. For [+45/-45]3s laminates, the maximum static torsion for carbon fibres is approximately 36% higher than for the glass fibres. The aluminum tube yielded first at the central region of the shaft, followed by crack propagation in the composite shaft along the fibre direction, which eventually caused delamination of the composite layers from the aluminum tube. Then the white regions appeared in the composite layer and finally the fibres broke and the catastrophic failure took place. For a hybrid shaft wound with fibre configurations of[90/+45/-45/90] and [+45/-45/90/90], the torque-angle-of-twist response results were similar and this satisfied the Classical Lamination Plate Theory. In addition, the torque capacity increased approximately 14 fold for the case of an aluminum tube wound with six layers of the carbon fibre and a winding angle of 45° compared to the aluminum tube alone.
Thermal and Morphological Studies of Acrylonitrile–Butadiene (NBR) Latex Reinforced Jute Nonwoven Fabric Composites
Authors: Kumar M.N. Satheesh , Siddaramaiah  , Jagannath J.H. , Bawa A.S.
Published: September 2018

A series of composites was fabricated by impregnating jute nonwoven fabric in a bath of acrylonitrile-butadiene (NBR) latex. Thermogravimetric analysis of the jute, NBR and their composites were performed in order to establish the thermal stability and mode of thermal degradation. Thermal degradation of the jute fabric and composites was found to proceed in two steps, unlike NBR. All the composites were stable to 280°C. A degradation kinetic parameter was obtained for each stage of degradation of the jute, NBR and their composites, using Broido, Coats-Redfern and Horowitz-Metzger methods.

The activation energy (Ea) of the composites for the thermal degradation process lay in the range 39-129, 35-130 and 20-142 kJ/mol for the Broido, Coats-Redfern and Horowitz-Metzger method respectively. Cryogenically fractured specimens were used to analyse the surface morphology of the jute fabric and composites by scanning electron microscopy.
Cure Kinetics of an Epoxy-Anhydride-Imidazole Resin System by Isothermal DSC
Authors: Wang C.S. , Kwag Choongyong
Published: September 2018

The cure kinetics of a dimethyl imidazole catalyzed diglycidyl ether of bisphenol A - methyltetrahydrophthalic anhydride resin system was examined. Degree of conversion versus cure time was obtained using isothermal DSC over the temperature range from 80 °C to 140 °C. The kinetic data were analysed using both nth order and autocatalytic kinetic models. The results indicated that the epoxy curing process could be described satisfactorily by Kamal's four-parameter generalised autocatalytic model modified with an exponential function of conversion defined as the diffusion factor. The curing process was predominantly autocatalytic in nature. The autocatalytic rate constant of the resin system was 10 to 60 times larger than the nth order rate constant. The corresponding activation energies obtained from Arrhenius equation were 78.1 kJ/mol and 67.6 kJ/mol, respectively. The approximate order of reaction was 0.39 for the autocatalytic reactions and 1.0 for the nth order reactions.
Preparation and Surface Properties of Siloxane-Acrylate Copolymer with High Siloxane Content
Authors: Deng Xiaobo , Cao Shunsheng , Liu Bailing , Luo Rong , Chen Hualin
Published: September 2018

A copolymer of acrylate and 3-(methacryloxypropyl)-trimethoxysilane (MPS) with high MPS content was prepared by emulsion copolymerisation and characterised by FT-IR, surface tension analysis and the static contact angle method. After Soxhlet extraction, there was scarcely any monomer or homopolymer left in the solvent and the weight losses in all the samples appeared to be negligible, which indicated that almost all the MPS and acrylate monomers had been copolymerised in the reaction. The FT-IR results also supported the same conclusion because there was no C=C peak in the spectrum. The surface tension also was investigated, and the outcome showed that the surface tension decreased with increasing MPS content in the copolymer. The surface properties of the copolymer films were studied by the static contact angle method too. Compared with the acrylate homopolymer, the copolymer containing MPS was more effective in creating a hydrophobic surface and the introduction of MPS was capable of making an obvious increase in water repellency. All the measurements were consistent with the conclusion that a copolymer of siloxane and acrylate with a high siloxane content has been prepared successfully. The siloxane content reached 30%, which was much higher than other reported values.
Characterization of Carbon Nanofibre Reinforced Epoxy Composite using Nanoindentation and AFM/UFM Techniques
Authors: Lee H. , Mall S. , Nalladega V. , Sathish S. , Roy A. , Lafdi K.
Published: September 2018

Carbon nanofibre (CNF) reinforced epoxy composites were characterized using nanoindentation, Atomic Force Microscopy (AFM) and Ultrasonic Force Microscopy (UFM). These tests were supplemented with ultrasonic wave propagation and three-point bend test methods. CNFs were functionalised with oxygen to improve dispersion and adhesion in the epoxy matrix. The CNF/epoxy composites showed an improvement in modulus and hardness compared to those of neat epoxy resin. The improvement was dependent on the functionalisation treatment time; however, the increase was of a different magnitude when measured by three methods: nanoindentation, wave propagation method and three-point bend (TPB) test. Thus, the indention test technique is capable of providing mechanical properties from a limited size and/or quantity of nanocomposites, which is generally the case during the initial material development stage. Further, the AFM-UFM was able to characterize the dispersion behavior of CNFs in nanocomposites, which is an important factor to improve the mechanical properties of nanocomposites. However, UFM provided much clearer information about dispersion than AFM. Finally, AFM-UFM appears to be a promising technique for observing nanocomposites at nanoscale and it has potential for the mapping of the local surface stiffness at nanoscale.
Processing-Induced Morphology: Its Relationship with Tensile-Impact Behaviour in Injection-Moulded Polypropylene
Authors: LaFranche Eric , Brassart Grέgory , Krawczak Patricia
Published: September 2018

This paper aims at identifying the main parameters that govern the tensile-impact strength of injection-moulded polypropylene. A Taguchi Design of Experiments (DOE) analysis has shown that the key parameters in both flow and transverse directions are the polymer melt and mould temperatures and the volumetric flow rate. The differences in high-speed mechanical behaviour have been explained on the basis of an investigation of the processing-induced morphology/tensile-impact behaviour relationship. The microstructure of parts manufactured under two extreme sets of moulding conditions has been analysed through-the-thickness by means of microscopy observations and by measurements of crystallinity, molecular orientation and thermal expansion. The impact brittleness originates from the skin layers, the major influential parameters being the skin/core ratio and the crystalline structure. The crack initiation energy increases with the oriented skin layer thickness, whereas the brittleness increases with the crystallinity level and the spherulite size.
Chemical Modification of Date Palm Mesh Fibres for Reinforcement of Polymeric Materials. Part I: Examination of Different Cleaning Methods
Authors: Taha I. , Steuernagel L. , Ziegmann G.
Published: September 2018

The use of date palm mesh fibres (DPMF) as reinforcements for polymeric matrices is the aim of this work. A first step towards fibre preparation and cleaning for further treatment is described. DPMF were chemically cleaned using sodium hydroxide, carbon tetrachloride, a detergent and an alcoholic mixture of toluene/methanol/acetone. The cleaning efficiency was investigated by scanning electron microscopy and its effect on thermal degradation, water absorption and mechanical properties were further analysed. The SEM micrographs show the most effective cleaning in the case of sodium hydroxide (NaOH) treatment, and subsequent investigations showed an improvement in the tensile strength and modulus of elasticity of the fibres. The water uptake of NaOH treated fibres was found to be higher than that of the untreated ones and their thermal stability lay within a similar range, i.e. 225–250 °C. Because of these promising results, alkali treatment will be adopted as the basic cleaning method for future work.
A Theoretical Model of a Magnetic Polymer
Authors: Maiti Pravat Kumar
Published: September 2018

We report a theoretical model of a magnetic polymer consisting of benzenoid structures incorporated in a simple linear polyethylene-like polymer chain. The benzenoid structures are double ring annulenes having 12, 16, 20 and 24 outer ring π electrons and the benzene ring inside the main cyclic π system. Either six or three covalent bonds of benzene linked to the outer ring carbon atoms at regular intervals will bring planarity to the annulene systems.

Hückel molecular orbital theory of quantum chemistry predicts that a 4n (n = 0, 1, 2,….) π alternating cyclic system has a triplet (2s + 1 = 3) stable ground state molecular orbital, provided the cyclic system is planar. Although cyclobutadiene is planar, it is quasi-stable. The 8, 12, 16, 20 and 24 annulenes are not planar but they are stable. If a benzene ring is introduced into the annulene ring and six or three carbon atoms of benzene are covalently linked to the carbon atoms of the outer ring annulene at regular intervals, the annulene systems might become planar. The presence of a benzene ring inside the annulene ring has little influence on the symmetry, electron distribution, energy level and molecular orbitals of the 4n system and as a result it is expected that these modified annulenes would have quite a stable triplet ground state. These predictions are here confirmed by DFT (density functional theory) geometrical optimisation of one of the systems at the B3LYP/6-31+G*level. Calculation of the nucleus independent chemical shift (NICS) at the centre of the ring produces strongly positive values for the triplet 4n annulene structure. Furthermore, the resulting systems do not undergo cyclo-addition (Diels Alder) reactions either at room temperature or in presence of UV radiation. If these planar star-like annulene molecules are incorporated into the polyethylene chain at regular intervals, the polymer is expected to be magneto- active.
Immobilized β-galactosidase: Preparation and Characterization
Authors: Zhang Ji , Zhang Shengtang , Zeng Jiayu , Wang Yunpu , Wang Yongfeng
Published: September 2018

A new enzyme support consisting of magnetic composite microspheres was prepared using artemisia seed gum, chitosan and magnetic fluid as a source, and characterized. The microspheres contained reactive aldehyde groups that react with the free amino groups of the enzymes.

The β-galactosidase was largely immobilized by covalent binding to the surface of the activated magnetic carriers. The factors controlling the relative activity and the enzymic properties of the immobilized β-galactosidase were compared with those of its soluble counterpart, for which ONPG (o-nitrophenol β-D-galactopyranoside) was chosen as a substrate. The pH and thermal stability of the immobilized β-galactosidase were higher than those of the soluble one.

The Michaelis constant, Km, was evaluated both for the immobilized β-galactosidase and for the soluble enzyme. The immobilized type exhibited better environmental adaptability and re-usability than the soluble one.
Tensile Fracture and Bond Properties of Ductile Hybrid FRP Reinforcing Bars
Authors: Won Jong-Pil , Park Chan-Gi , Jang Chang-Il
Published: September 2018

Fibre reinforced plastic (FRP) rebar has only linear elastic behaviour, whereas steel rebar has linear elastic behaviour up to its yield point, followed by a large amount of plastic deformation. With no plastic deformation, a small increase in the load acting on concrete structures containing FRP rebar can cause a catastrophic collapse without warning. A ductile hybrid FRP rebar was manufactured and evaluated in this study. The tensile and bond strengths of the hybrid FRP rebar were tested to determine its fracture properties and bond behaviour. It showed elastic behaviour up to the point of early fracture, but had very irregular behaviour thereafter. The fibres in the sleeves were broken at very irregular lengths, while the cores appeared to fracture in a regular pattern. The stress–strain curves were linearly elastic, with a definite yield point followed by pseudo-plastic deformation. In addition, the hybrid rebar specimens exhibited a large amount of slip when the peak load was reached.
Synthesis and Application in Polypropylene of a Novel Nitrogen-Containing Intumescent Flame-Retardant
Authors: Liu Gang , Zhao Jianqing , Zhang Yonghua , Liu Shumei , Ye Hua
Published: September 2018

A nitrogen-containing blowing agent, poly(2-piperazinylene-4-morpholino-1,3,5-triazine) (PPMT), was synthesised for use as the gas resource in an intumescent flame-retardant system. Nickel (II) acetate, as a synergistic agent, was used in order to improve the flame retardancy of polypropylene. PPMT was characterised by Fourier transform infrared spectroscopy. A variety of characterisation methods including limiting oxygen index, thermogravimetric analysis, and the UL-94 flammability test were applied to evaluate the flame-retardancy and thermal stability of flame-retardant polypropylene.
Mode 1 Interlaminar Fracture Behaviour of Continuous Glass Fibre/ Polypropylene Composites Based on Commingled Yarn
Authors: Wang Yantao , Dong Qingzhi , Liu Xin
Published: September 2018

The mode 1 interlaminar fracture behaviour of commingled glass fibre/polypropylene (GF/PP) composites moulded at different cooling rates was investigated. The composites were prepared from unidirectional, woven fabric and mat plies, respectively, and tested using double cantilever beam specimens. The results showed that mat composites possessed the highest interlaminar fracture toughness, whereas woven fabric laminates were the most sensitive to delamination at a fixed cooling condition, as a result of different crack propagation mechanisms. For woven fabric composites, a small amount of debonding of transversely oriented fibres occurring periodically on the free edge is thought to have been responsible for the lowest interlaminar fracture toughness. As expected, extensive fibre bridging and tortuous crack growth path effectively improved delamination resistance of unidirectional laminates. The highest interlaminar fracture toughness for mat laminates was attributed to pronounced debonding of off-axis fibres or yarns combined with pull-out of through-thickness fibres during crack propagation. Moreover, it could be deduced that using different cooling rates would impose various levels of delamination resistance in GF/PP composites because of the considerable effect on the microstructure of the PP matrix and on fibre-matrix interactions. Micrographs of the fracture surfaces of the specimens proved the important role of the amorphous PP phase at the fibre-matrix interface.
Phase Change Materials-Embedded Coatings Prepared by In-situ Polymerisation of Water-borne Polyurethane-urea
Authors: Yoo Hye-Jin , Kim Eun Young , Kim Han-Do
Published: September 2018

Waterborne polyurethane-urea (WBPU) emulsions embedded with phase change materials (PCM; hexadecane, octadecane, and eicosane) as microspheres were prepared by in-situ polymerisation in an emulsion system. Polyamide fabrics were coated with coating materials formulated from PCM embedded WBPU/thickener/hardener. The maximum /optimum contents of embeddable PCM in WBPU dispersions for stable WBPU emulsions were found to be about 30 wt%. By DSC analysis,)Hfusion,)Hcrystallization, and the embedding efficiencies of PCM of film samples were found to increase with increasing PCM contents of up to 30 wt% to reach their maximum values. The maximum buffering temperature of polyamide fabrics coated with PCM (30 wt%) embedded WBPU were about ± 3 °C around the phase transition points of PCM. The PCM (30 wt%) embedded WBPUs dispersions prepared here by in-situ polymerisation show excellent potential as coating materials, with good heating and cooling functions.
Prediction of Thermal Conductivity of Aligned Short Fibre Composites with Different Fibre Aspect Ratios
Authors: Lee Jae-Kon
Published: September 2018

A closed-form solution using the distribution of fibre aspect ratios is proposed for predicting the thermal conductivity of aligned short fibre composites. The present model is the extended version of Hatta and Taya's model, where Eshelby's equivalent inclusion method modified for finite volume fraction of fibres is employed. The validity of using the average fibre aspect ratio for predicting the thermal conductivity is examined in terms of the distribution of the aspect ratios such as its average and standard deviation, fibre volume fraction, and constituents' thermal conductivity ratio. The guideline for the selection of either the actual distribution or the average fibre aspect ratio is presented in terms of the thermal conductivity ratio and the coefficient of the variation of the aspect ratio for the better prediction of the thermal conductivity of the composites.
Composite Materials from Unsaturated Polyester/Rice Husk Ash/ Natural Rubber-g-Polystyrene
Authors: Chuayjuljit Saowaroj , Sriratampai Pecharee , Potiyaraj Pranut
Published: September 2018

Composite materials from unsaturated polyester (UPE) resin, black rice husk ash (BRHA), and natural rubber grafted polystyrene (NR-g-PS) were prepared. NR-g-PS was synthesised by emulsion copolymerisation with a NR/styrene molar ratio of 80/20 using tert-butyl hydroperoxide/tetraethylene pentamine (t-BHPO/TEPA) as an initiator. Grafting efficiency of the copolymer product was about 54%. Initially, UPE was blended with BRHA at UPE/BRHA weight ratios of 100/30, 100/40 and 100/50. Each blend was subsequently mixed with NR-g-PS in the proportions of 5, 10 and 15 parts per hundred of UPE resin (phr). After curing, the cast specimens were examined for their physical properties, thermal expansion coefficient and morphology. It was found that the composite of 100UPE/30BRHA/5NR-g-PS exhibited the highest flexural and impact strength but the lowest water absorption. The thermal expansion coefficient of 100UPE/30BRHA/5NR-g-PS composite measured by thermomechanical analysis (TMA) was as low as 0.00005/°C. The morphology of the composites was investigated by scanning electron microscopy (SEM), which disclosed that NR-g-PS particles were well dispersed in the UPE matrix whereas the RHA was agglomerated and poorly dispersed in the composites. The higher the amount of NR-g-PS the more agglomeration of BRHA. This was due to the very high viscosity of the systems.
Thermal Decomposition and Oxidation Ageing Behaviour of Polypropylene/Halloysite Nanotube Nanocomposites
Authors: Du Mingliang , Guo Baochun , Liu Mingxian , Jia Demin
Published: September 2018

The thermal decomposition and oxidation ageing behaviour of polypropylene (PP) and PP/halloysite nanotube (HNT) nanocomposites were studied. The kinetics of thermal decomposition were calculated by integral models. The thermal oxidation ageing was investigated by Fourier transform infrared spectroscopy (FTIR). The PP nanocomposites showed a higher activation energy of thermal decomposition than neat PP. Their surface treatment and lower HNT loading led to a higher activation energy of decomposition. Their improved thermal stability in nitrogen was attributed to entrapment of decomposition products at initial decomposition stage and to barrier effects.

Nanocomposites made by using silane-modified HNT (m-HNT) and also those with lower quantities of (unsilanated) HNT showed improved resistance to thermo-oxidative ageing. The rate of thermo-oxidative ageing was correlated with the number of acidic sites and the volume of entrapped oxygen in the lumen of the HNT and in cavities.
The Influence of Reaction Kinetics on Polyurethane/Vinyl Ester Resin Interpenetrating Polymer Networks
Authors: Qin C.L. , Niu H.J. , Bai X.D. , Ding Y.C. , Yang W. , Cai W.M.
Published: September 2018

Polyurethane/poly(vinyl ester resin)(butyl methacrylate) Interpenetrating Polymer Network (PU/VER(BMA) IPN) materials were synthesised at room temperature by polymerising butyl methacrylate as a comonomer with simultaneous interpenetration. The curing process of these IPNs was dynamically traced and semi-quantitatively analysed by Fourier transform infrared spectroscopy (FT-IR) and the kinetics of their formation with different PU catalysts and VER initiators was studied. The results showed that when the amounts of stannous octoate and BPO respectively were 0.5wt.% of PU and 0.67wt.% of VER, the reaction rates of the monomers were close, the conversions of the monomers were high and these amounts were optimised. The influence of the kinetics on the microstructure and damping properties of the IPNs was detected by Transmission Electron Microscopy (TEM) and by Dynamic Mechanical Analysis (DMA). The results showed that with the appropriate amount of the polyurethane catalyst stannous octoate and VER initiator BPO, the PU/VER(BMA) IPN showed a multiphase microstructure containing some finer phase domains having nanometre domain sizes, together with good damping properties (a broad damping plateau and high tanδ). When the amount of stannous octoate or BPO was increased or decreased, the IPNs presented an unfavourable microstructure and poor damping properties. The relationship between the kinetics, microstructure and damping properties was analysed further.
Kinetics of Ageing of Wood-Filled Polypropylene-Based Composites
Authors: Nenkova Sanchi , Dobrilova Cvetomira , Vassileva Stefanka , Natov Milcho , Valcheva Eva
Published: September 2018

The kinetics of light ageing of wood filled composites made from polypropylene filled with unmodified wood flour and with wood flour modified with maleic anhydride (MA) in amounts of 10, 20 and 30% has been investigated.

The investigation shows that the light ageing of wood-filled polypropylene-based composites is an autocatalytic chain process. The decrease of the rate constants with increasing wood content showed that the wood flour had a screening effect on light.

It is established that the modification of wood flour with MA have a stabilising effect on the ageing of the composite materials owing to a decrease in the number of active centres capable of undergoing oxidation, and in the number of the carbonyl groups.
Morphology and Viscoelastic Properties of Poly(Vinyl Chloride)/ Poly(Vinyl Alcohol) Incompatible Blends
Authors: Takeuchi Kazuma , Kamaguchi Akihiro , Nabeta Muneaki , Fujii Syuji , Nakamura Yoshinobu , Iida Takeo
Published: September 2018

The effects of the pre-mixing method and degree of saponification poly(vinyl alcohol) (PVA) on the morphology of poly(vinyl chloride) (PVC)/PVA blends were investigated. Two pre-mixing methods were employed: a powder method and an aqueous solution method. In the powder method, both components were blended in powder form before melt kneading using a mixing roll. In the aqueous solution method, the PVC powder was added to an as-prepared PVA aqueous solution, followed by drying and then pounding before melt kneading. In the case of PVA with a degree of saponification of 98 mol%, PVA domains several hundred μm across were dispersed in the PVC matrix in the powder method system, whereas finer PVA domains with sizes ranging from sub μm to several μm were observed in the aqueous solution method. In the cases of PVA with saponification degrees of 88 and 78 mol%, domain sizes of several tens of μm were observed for both powder and solution methods. This indicates that there was no apparent influence of pre-mixing method on the domain size. When poly(methyl methacrylate) (PMMA) was added to the PVC/PVA blend, smaller PVA domains (with sizes ranging from 5 to 10 μm) were observed in both powder and solution method systems than without the PMMA. Viscoelastic properties showed specific interactions between PVC and PMMA, and between PMMA and PVA.
Processing, Impact Response and Damage Characterisation of Plain-Weave Carbon/Epoxy-Nanoclay Nanocomposites
Authors: Chowdhury F.H. , Hosur M.V. , Jeelani S.
Published: September 2018

An organically modified montmorillonite nanoclay, was used to modify a toughened epoxy system using the sonication route. The modified epoxy was then used to fabricate 15-layer plain weave carbon/epoxy laminates using hand-layup followed by vacuum bag moulding. X-ray diffraction studies were carried out to investigate the basal spacing between the clay galleries. The results indicated that an intercalated clay structures was produced. Samples were cut from the laminates and subjected to low-velocity impact loading using an instrumented drop-weight system. Transient responses of the samples were recorded and analysed in terms to load-energy versus time relations. Impact damage was characterised by utilising an ultrasonic non-destructive evaluation system. Results of the study indicated that nanoclay reinforced laminates exhibited better impact performance in terms of higher peak load and reduced damage size than the controlled samples at any given energy level.
Thermal and Mechanical Couplings in Plain and Wood Fibre Reinforced Polypropylene during Tensile and Fracture Tests
Authors: Dupre Jean-Christophe , Lagattu Fabienne
Published: September 2018

The aim of this work was to show the influence of spruce fibres on polypropylene, by way of an experimental thermo-mechanical approach. These studies were performed by the simultaneous measurement of the strain field and the thermal field. A digital image correlation method was used for the strain measurements. The thermal field was obtained with the help of an infrared camera. The heat equation established in the context of classical thermodynamics of irreversible processes allowed us to evaluate the heat sources.

The main difference between the plain resin and the composite material was that the heat sources dissipated by the composite were locally lower. In tensile tests the plain material allowed the creation of a neck zone with very high strain values. In fracture tests, it also generated very high strains localised at the crack tip. For the composite, the results of tensile tests showed that the presence of wood fibres led to a quasi-brittle failure of the specimen. In fracture tests, a better overstress accommodation was observed near the crack tip by distributing the strains in a wider zone.
Non-Isothermal Crystallisation Kinetics of Polyamide 6/Mesoporous Silica Nanocomposites
Authors: Hu Qingyuan , Ji Xiangling , Lu Yunfeng
Published: September 2018

Non-isothermal crystallisation kinetics of a polyamide 6/mesoporous silica nanocomposite (PA6-MS) has been investigated by differential scanning calorimetry (DSC) at different cooling rates. Mandelkern, Jeziorny-Ziabicki and Ozawa methods were applied to describe this crystallisation process. The analyses show that the mesoporous silica particles act as nucleating agents in the composite and that the Avrami exponent n varies from 3.0 to 4.6. The addition of mesoporous silica influenced the mechanism of nucleation and the growth of polyamide 6 (PA 6) crystallites.
Preparation and Optimisation of Polyethersulfone-Based Composite Membranes for Air Separation at Low Pressures
Authors: Madaeni S.S. , Esmaeili M. , Barzin J.
Published: September 2018

Three polymeric solutions with different concentrations (1, 2 and 6% wt) of glassy polymers including ethyl cellulose (EC), poly vinyl alcohol (PVA) and polystyrene (PS) were employed for the preparation of the top layer of composite membranes with 18% wt polyethersulfone (PES) by dip coating. Membrane morphology was characterised using scanning electron microscopy, IR-ATR experiments and gas separation performance. The results indicate that PVA and PS composite membranes improve the selectivity of PES membranes to some extent. EC provides no selectivity. Increasing the PES concentration of the EC composite membrane improves the selectivity considerably. The concentration of EC was increased to 9% wt and the solution was coated on the surface of PES membranes having different concentrations (18, 25 and 37 wt%). Gas permeability and selectivity of EC membranes revealed that a coating solution with an EC concentration of 6% wt is an optimum condition for enhancing the selectivity.
Flame Retardant Polyethylene with Intumescent System Containing Macromolecule-Encapsulated Low Molecular Weight Charring Agent
Authors: Liu Meifang , Huang Xing , Liu Yuan , Wang Qi
Published: September 2018

Intumescent flame retardants are important halogen-free products used in polyethylene. However, their thermal stability and water-resistance are major shortcomings. In this work, a composite charring agent, pentaerythritol (PER) encapsulated by thermoplastic polyurethane (TPU) was used in an intumescent system to improve the flame retardancy of high density polyethylene (HDPE). The encapsulation of macromolecular charring agent TPU can effectively suppress the esterification reaction of PER and acid source in the intumescent system during processing. It can also remarkably decrease the water absorption, thus producing flame retardant HDPE with high performance. The synergistic effects of other common flame retardants including melamine phosphate, melamine polyphosphate and ammonium polyphosphate with TPU-encapsulated PER, as well as the ratio of charring agent to acid source were investigated so as to determine the optimum formula for use in HDPE. The flame retardant HDPE can reach limiting oxygen index of 33 and achieve UL-94 V-0 rating at 3.2 mm thickness when the ratio of MP/composite charring agent is 2:1 w/w.
Preparation and Conductivity of Polyaniline/Sio2 Composites
Authors: Tang Qunwei , Wu Jihuai , Ao Haiyong , Sun Hui , Lin Lin , Lin Jianming
Published: September 2018

A novel polyaniline/ silica composite with a conductivity of 0.26 S/cm was prepared by the polymerisation of aniline monomer and ultrafine silica powder in aqueous solution in the presence of hydrochloric acid as dopant and ammonium persulfate (APS) as initiator and oxidant. The influence of APS, silica and dopant on the volume conductivity of the composite was investigated by X-ray diffraction, infrared spectroscopy and conductivity measurements. The preparation conditions were optimised. The conductivity of the composites remained fairly stable on storage for 50 days.