bluuebunny/crossref_metadata_2025 huggingface dataset:
Prediction of the Ultimate Strength of Composite Laminates under in-Plane Loading Using a Probabilistic Approach
Authors: Kang Tae Jin , Cho Young Jun , Youn Jae Ryoun , Chung K. , Lee Kyung Woo
Published: September 2018

A numerical approach to predicting the ultimate strength of composite laminates is presented. In order to take into account the wide scatter in ply strengths, the basic strength distribution functions for the longitudinal, transverse and in-plane shear strengths were obtained using a two-parameter Weibull distribution. These functions, in conjunction with the Tsai-Hill failure criterion, were then used to predict the ultimate strength of the composites. Reasonable agreement was obtained between the predicted and experimental results, not only in respect of the ultimate strength, but also in relation to the stress-strain curves for the various composites.
The Effect of Polymerization Conditions on the Density and Tg of Bisphenol-A and Hexafluoroisopropylidene-Containing Polybenzoxazines
Authors: Kanchanasopa Mantana , Yanumet Nantaya , Hemvichian Kasinee , Ishida Hatsuo
Published: September 2018

The volumetric expansion of bisphenol-A and aniline-based benzoxazine (BA-a) has been studied by comparing the room temperature density of the cured BA-a under different polymerization conditions with the amorphous BA-a monomer. The glass transition temperatures (Tg) of BA-a at various degrees of polymerization have been investigated by differential scanning calorimetry (DSC). The degrees of conversion at different polymerization temperatures were compared with the respective glass transition temperatures. It was found that substantial development of Tg occurs at low degrees of conversion. A fluorinated polybenzoxazine was synthesized from the ring-opening polymerization of hexafluoroisopropylidene-containing benzoxazine monomer. The properties of the fluorine-containing polymer were compared to those of nonfluorinated polybenzoxazine. Fluorine incorporation had a profound effect on the glass transition temperature of polybenzoxazine. The thermal stability also improved upon fluorination.
Carbon Fibre-Reinforced Poly(Phenylenesulphide) Composite Coatings
Authors: Sugama Toshifumi , Gawlik Keith
Published: September 2018

To enhance the thermal conductivity and improve the mechanical properties of poly(phenylene sulphide) (PPS) that was used as a coating for carbon steel heat exchanger tubes, chopped carbon fibres, ∼7.5 μm diam. x ∼3 mm long were incorporated into the PPS matrix. All the experiments in this work were performed using steel panels instead of steel tubes. As a result, 0.5 wt% of fibres was the most effective amount of fibres in minimizing the rate of penetration of electrolytes through the composite coating films. Even though the steel panels coated with the 0.5 wt% fibre-reinforced PPS composites were exposed for 14 days in an autoclave containing 20,000 ppm CO2-laden 13 wt% NaCl solution at 200°C, the coatings remained intact. This suggested that the composite coatings not only adequately protect steel against corrosion in a wet, harsh, and hostile geothermal environment, but they also have great hydrothermal stability. In addition, the thermal conductivity of the bulk PPS rose ∼ 60% by adding 0.5 wt% fibre. The rough surface texture of the fibres provided good mechanical interlocking bonds with the PPS matrix. Such interfacial bonding can be interpreted as one of the factors governing the outstanding mechanical properties, such as tensile strength, tensile modulus, and elongation, of the multidirectional fibre-reinforced composite films.
Evaluation of Two-Roll Mill Method for Preparing Short Glass Fibre Reinforced Nbr-Phenolic Composites
Authors: Rezadoust A.M. , Esfandeh M.
Published: September 2018

Mechanical properties of short fibre composites depend strongly on the fibre length. Therefore, in preparing short fibre composites, processing conditions are of great importance as they affect the final fibre length. In this study 50 mm glass fibres were used to prepare acrylonitrile butadiene rubber (NBR) phenolic-glass fibre composites by two-roll mill method. Fibre breakage during processing was studied and the fibre critical length was calculated. On the basis of the critical length, the usefulness of the two-roll mill method for preparing glass-NBR-phenolic composites with the specified formulation was assessed.
Heat Stability and Degradation of Thermally Stable Prepolymers in a Controlled Atmosphere
Authors: Richer S. , Alamercery S. , Delolme F. , Dessalces G. , Paisse O. , Raffin G. , Sanglar C. , Waton H. , Grenier-Loustalot M.F.
Published: September 2018

Monitoring the homopolymerization of cyanate monomers during heat treatment shows that triazine rings formed during the 180°C step. Oligomers were composed of 1 to 15 triazine rings. Analysis of compounds formed before the gel point revealed the presence of side products containing terminal phenolic functions: the phenol-cyanate (M0-OH) and oligomers with one or two hydroxyl functions (M1,2,…-OH). Kinetic and mechanistic monitoring during treatment at 210°C in the solid state allowed the determination of the structure of the final system and the detection and quantification of unreacted cyanate functions. Kinetic and thermal studies in the temperature range of 100 to 220°C showed that the homopolymerization of hexafluorobisphenol A dicyanate starts at a lower temperature and is slower than that of bisphenol A dicyanate. Thermogravimetric data showed that residual monomers volatilized between 150 and 300°C, while the degradation of crosslinked products occurred between 400 and 600°C and involved two distinct steps.
The Effect of the Vulcanizing System on Cure and Mechanical Properties of Nbr/Epdm Blends
Authors: Oliveira Marcia G. , Soares Bluma G.
Published: September 2018

The effect of the curing system and curing parameters, mechanical properties, ageing resistance, and crosslink density of NBR/EPDM blends has been investigated. The curing characteristics of the blends were affected by the accelerator type and the sulphur concentration. The sulphur/benzothiazyl-disulphide (S/MBTS) vulcanizing system offered the best scorch safety, whereas those single and binary accelerator systems based on tetramethyl thiuram disulphide (TMTD) provided faster cure. The MBTS single accelerator system was able to crosslink the EPDM phase better and consequently displayed better mechanical performance than the other systems based on tetramethyl thiuram disulphide (TMTD). Higher thermal stability was also achieved in blends containing higher levels of sulphur, probably because of increased crosslinking in the EPDM phase. The results of dynamic mechanical investigations showed differences in the glass transition temperatures, which increased with increasing of the sulphur content in both S/MBTS and S/MBTS/TMTD vulcanizing systems. Formulations based on S/TMTD single accelerator systems gave the lowest values of Tg, and the amount of sulphur did not affect this property.
The Plastic Deformation of Fibrous Polymers via Weibull Model
Authors: Juhar G. , Saqan S. , Zihlif A.M.
Published: September 2018

This work deals with the plastic deformation of polypropylene, PAN-based carbon and Kevlar fibres at different gauge lengths and uses the Weibull model. A statistical analysis for the fibre strength and breaking strain is presented to test the experimental data relating to the fibre deformation. The mechanical parameters such as fibre strength, breaking strain and Young's modulus have been studied as a function of gauge length. It was found that both strength and breaking strain increase as fibre gauge length decreases, while the Young's modulus increases with increasing gauge length and depends on both strength and breaking strain. The output of the analysis supports the concept that the Weibull model is a good technique to specify the statistical distribution for strength and breaking strain of fibres and of suitable to investigate, is the deformation behaviour of fibrous polymeric materials in general.
A Comparison of the Mechanical Behaviour of Weft-Knitted Glass and Carbon Fiber Fabric-Reinforced Polyamide-12 Composites Produced with Commingled Staple Yarns
Authors: Czigány T. , Karger-Kocsis J.
Published: September 2018

The mechanical response of knitted glass- (GF) and carbon fiber (CF) fabric-reinforced polyamide-12 (PA-12) composites was compared both under static (tensile, flexural) and dynamic (perforation impact) conditions. The GF- and CF-content of the composites produced by hot pressing of 8 layers of planar weft knits containing staple reinforcing GF or CF and PA-12 fibers was practically the same, viz ca. 50 vol%. Dynamic-mechanical thermoanalysis (DMTA) showed a strong stiffness anisotropy: the stiffness of the composites in the wale-direction (W) was markedly higher than in the course-direction (C). The same strong anisotropy was also found for the static tensile and flexural characteristics (stiffness and strength). The mechanical anistropy and the large difference between the stiffness and strength due to tensile and flexural loading were traced to the structure of the knits (“unbalanced” reinforcement) and their non-planar structure in the composite sheets. The mechanical performance of the knitted CF-reinforced composite was superior to the GF-reinforced version under dynamic perforation impact conditions as well.
Kinetics of Zinc Octoate/Nonylphenol Catalysed Thermal Cure of Bisphenol a Dicyanate
Authors: Nair C.P. Reghunadhan , Gopalakrishnan C. , Ninan K.N.
Published: September 2018

The kinetics of the Zinc octoate/nonylphenol catalysed thermal cure of bisphenol A dicyanate (BACY) was investigated using non-isothermal differential scanning calorimetry (DSC). The kinetic parameters were estimated by the methods of Coats-Redfern (C-R) and Roger and Kissinger. The overall reaction conformed to first order kinetics. The calculated activation energy (E) and pre-exponential factor (A) depended on the analytical approach. However, the variation in activation energy was associated with a proportional change in A, rendering the overall rate constants nearly identical and independent of the analytical method for a given system. The presence of catalyst enhanced the rate constant. The apparent activation energies, normalised to a fixed A value, were practically identical for a given system, implying the existence of a kinetic compensation effect. The activation energy decreased with increasing catalyst concentration. The variation in activation energy with conversion for a given catalyst concentration was within the kinetic compensation limit for a given system. The activation parameters were used to predict the cure profile of the resin under given conditions of temperature and catalyst concentration.
Effect of Kenaf Fibres on the Properties of Natural Rubber Vulcanizates
Authors: El-Sabbagh S.H. , El-Hariri D.M. , El-Ghaffar M.A. Abd
Published: September 2018

The mechanical properties and swelling behaviour of natural rubber (NR) vulcanizates loaded with kenaf fibres were studied using (hydrated silica, resorcinol and hexamethylene tetramine) as the adhesion system and compared with those of NR vulcanizates loaded with synthetic polyester short fibres (viscose).

The effect of fibre content on the afore mentioned mechanical properties of NR vulcanizates was also studied before and after ageing. The kenaf fibres showed a higher reinforcing effect than that of synthetic polyester fibres and improved the rheological properties. Scanning electron microscopy was used to investigate the surface texture of unreinforced and reinforced vulcanizates.
Permanent, Transparent, Non-Blooming and Non-Hygroscopic Antistatic Agents Based on Combined Neoalkoxy Organometallics
Authors: Monte Salvatore J.
Published: September 2018

Minor amounts of thermally and hydrolytically stable combined dissimilar polarity type neoalkoxy titanates and/or zirconates can be added directly into the polymer during the thermoplastic or thermoset compounding phase at temperatures in excess of 200°C to form bipolar layers that provide a transparent, non-blooming organometallic transfer circuit resulting in a volume as well as surface antistatic effect. The permanent antistatic effect depends upon a complete dispersion of the combined organometallics and thus works differently than conventional surface blooming hygroscopic antistats that rely on polymer incompatibilization and resultant surface blooming to attract ESD atmospheric moisture to the thermoplastic surface in environments having humidity greater than 25%. A transparent film results since the combined organometallics are of good color and solubilize into the polymer, and are not made of insoluble conductive particulate or cobalt-based metallocenes. Specifically, it will be shown that when using a combined trineoalkoxy dodecylbenzene sulfonyl zirconate/trineoalkoxy aliphatic amino zirconate antistatic agent, transparent olefin films remain clear after long-term aging tests. Atomic dispersion of the antistat will be shown to be critical. For example, data will show that when 1% of the new and novel antistat is added to polypropylene in an intensive mixer (Banbury) operating in the range of 160 to 190°C – and the mixer compounding conditions are changed (to increase specific energy input) from 30-second drop after flux occurs @ 50 rpmto 2-3 minutes drop after flux occurs at 100-125 rpm – the resistivity will be lowered from 1013 to 1011 Ω/sq. for 30 mil compression molded slabs. Differences in ESD effects in HDPE using a 2-roll mill vs. a twin-screw extruder will be discussed. In addition to PP and HDPE, ESD effects will be shown in various other polymer disciplines such as LLDPE, PVC, PVC/Nitrile, PETG, Nylon, PES, Acrylic, ABS, Ethyl Acetate (Nail Polish), Natural Rubber Latex, Acrylic Latex and Polyurethane. For example, a clear thermoplastic polyurethane having a surface resistivity and a volume resistivity of 1.3 × 1016 Ω/sq. and 1.7 × 1015 Ω-cm respectively will exhibit ESD properties of 7.4 × 1012 Ω/sq. and 4.6 × 1011 Ω-cm when 2% by weight of PU of a 60% active combined trineoalkoxy zirconate on silica powder masterbatch is used.
Halogenated and Non-Halogenated Flame Retardant Additives in Polypropylene (PP) Homopolymer for Battery Applications
Authors: Rangaprasad R. , Rangan K. , Vasudeo Y.B.
Published: September 2018

The paper describes how to make PP homopolymer flame retardant through the use of halogenated and halogen-free additives. The paper attempts to capture the intricacies involved in compounding recipe development, physical and mechanical properties and performance aspects during injection moulding of the final article. In a nutshell, the paper describes the end user's experience of flame retardant additives in PP homopolymer from concept to product.

The present work was directed towards compound development and the characterization of physical, mechanical, flammability performance and performance during the injection moulding of PP homopolymer. The application identified was injection mouldable battery boxes for applications in the telecom sector.

PP compounds were prepared from halogen-based and halogen-free flame retardant (FR) additives, designed to meet V0 at 3.2 mm thickness as per the UL94 test protocol.

Flame retardant polypropylene; (FR-PP) is used for “back-up” batteries. These are used in telecommunications and railway units and supply energy immediately in the case of an interruption of normal power supply. The batteries contain sulphuric acid as electrolyte.

Experimental work was undertaken to develop FR-PP compounds and investigate the effect of FR additives on critical properties. The effect of FR-additives on the heat sealing properties of battery containers was also investigated.

The results show that halogenated FR additives can contribute to the excellent acid resistance of PP. Use of non-halogenated FR additives in PP resulted in compounds having densities close to 1.0 g/cm3, at identical loadings to those used with halogenated FR additives. In comparison, FR-PP compounds based on halogenated FR additives gave densities close to 1.2 g/cm3.

The data obtained from this investigation show that both types of FR/PP compounds are suitable for battery box applications made by injection moulding.
Siloxanes as Additives for Plastics
Authors: Stadtmüller S.
Published: September 2018

Organomodified siloxanes combine the high efficiency of silicone oils with good compatibility with polymeric resins. The synthesis of organic siloxanes reveals a high degree of freedom, giving access to a variety of different representatives. Depending on the nature of the organic moiety and the overall molecular weight, organomodified siloxanes can be adapted to special applications within polymers. Thus their performance covers the range from performance additives, as lubricant or dispersing agent, as in filled compounds, to surface modifying additives, helping to improve surface characteristics, such as scratch resistance. Various polypropylenic compounds containing representatives of such organomodified siloxanes were evaluated. Process parameters such as energy consumption, pressure build up and out-put rate on a twin screw extrusion line could be increased. A positive influence on surface properties could be obtained by selecting favourable additives from this class of products.
A Revolutionary Light Stabilizer System for Polyolefins and Other Resins
Authors: Arnaboldi Paolo , Davis Leonard , Samuels Sari-Beth , Zenner John M. , Vulic Ivan
Published: September 2018

The use of plastics is being extended into increasingly durable applications. These include applications where direct sunlight exposure is common or occurs daily. Direct UV exposure is known to deteriorate the physical and aesthetic properties of nearly all polymers, though to varying extents. As the service life demands of polymers become more rigorous, the development of improved performance light stabilizers is critical. To help meet these performance criteria, a new generation of light stabilizers has been developed which shows extraordinary efficacy in polyethylene, polypropylene and other resins.
Thermal Stability and Degradation of Thermally Stable Prepolymers under Controlled Atmosphere: IV- Thermal Stability and Degradation of Cross-linked Systems Prepared from Cyanate Monomers
Authors: Richer S. , Alamercery S. , Raffin G. , Sanglar C. , Waton H. , Grenier-Loustalot M.F.
Published: September 2018

We report the results of a study on the thermal degradation of cyanate prepolymers and corresponding materials prepared in the molten state by the homopolymerization of monomers in a controlled atmosphere (nitrogen) and in the temperature range of 100 to 500°C. We propose degradation mechanisms for these materials based on the analysis of physicochemical data obtained by the differential scanning calorimetry, thermogravimetric analysis, gas chromatography-mass spectrometry and Fourier transform infrared spectroscopy of volatile organic compounds and residues after the thermal cycle. These mechanisms depend on the structure of the carbon skeleton.
Processing and Properties of Polypropylene Composites with High Filler Content
Authors: Ren Z. , Shanks R. A. , Rook T. J.
Published: September 2018

Highly filled polypropylene composites have been prepared with filler contents up to 43.8 vol.% (70 wt.%) after surface treatment of the fillers with titanate or silicone. The fillers used were calcium carbonate, talc and barium sulfate. Surface modification of the fillers facilitated extrusion and reduced brittleness while providing hard composites with high density. The high density and hardness provide a texture which is not characteristic of polypropylenes, but more like thermoset composites or ceramics; yet the composites can be extruded using typical thermoplastic processing equipment. The composition has been measured by thermogravimetry, and morphology observed with scanning electron microscopy. The tensile properties were measured and related to the composition, filler type and surface treatment.
Modification of Polypropylene by Blending with Oligopinene
Authors: Mendes L.C. , Martins B.B.B.
Published: September 2018

The changes in physical properties, melting behaviour and morphology of polypropylene (PP) in binary blends with low molar mass oligopinene resin were evaluated. Melting mixtures were prepared in a Haake Rheocord at 473 K, 30 rpm, for 600s; an abrupt drop in torque was observed when the blends were enriched by oligomer. At room temperature, with up to 20% of oligopinene, the nominal stress-strain curves of the blends showed a change in behaviour from ductile to brittle. The elastic modulus increased, and the other mechanical parameters were also dependent on the composition. The density increased linearly with oligopinene content, and the hardness also increased with the amount of oligomer present. No phase segregation was observed, before or after etching with heptane. The SEM results indicated that the oligopinene component is located mainly in the intraspherulitic regions of the PP.
Effect of Heat Treatment on the Fracture Toughness of Glass Fibre Reinforced Polypropylene
Authors: Lin Jeng-Shyong , Wu Sheng-Kuen
Published: September 2018

In this work, the effect of heat treatment on the fracture toughness of glass fibre reinforced polypropylene was studied. Polypropylene blended with short glass fibres was injection-moulded. The moulded parts were heat treated at 150°C for 30 min. The crack growth resistance curve (R-curve) was measured to evaluate the effect of heat treatment on the fracture toughness, and to determine the stress intensity factor at the point of instability, KR(ins). The fracture surface was examined using scanning electron microscope to analyze the fracture mechanism. The results show that the stress intensity factor at the unstable fracture point KR(ins) increases with the initial crack length.
Dielectric Properties of Polymers Filled with Dispersed Metals
Authors: Mamunya Ye.P. , Davydenko V.V. , Zois H. , Apekis L. , Snarskii A.A. , Slipchenko K.V.
Published: September 2018

The authors have studied the dielectric properties of composite materials based on both thermoplastic and thermoset resins filled with nickel or copper, with various particle sizes and shapes. In addition, two types of particle distribution, random and segregated, were produced for composites filled with nickel. The main objective was to study the effect of the above factors on the dielectric properties of the composites. The concentration dependence of the dielectric parameters (i.e. the real, ∊′, and the imaginary, ∊″, parts of the complex dielectric permittivity and the dielectric loss tangent, tanδ), calculated for all the systems studied, demonstrates a critical behaviour in the percolation threshold region, with maximum values reached at a volume fraction ϕ = ϕc. The dependence of the dielectric parameters on concentration follows power-law behaviour in the ϕ < ϕc region. The critical exponent value for ∊′ is q = 0.75, in agreement with the theoretical one. The dielectric characteristics of the filled composites are more sensitive to the spatial filler distribution. For the segregated PVC-Ni system with an ordered filler distribution, the value of ϕc is much lower than for ER-Ni composites with a random filler distribution. Besides, for the segregated PVC-Ni system, the value of q is not constant, as it depends on the filler concentration. A model for the structure, which explains this behaviour, is proposed.
Cure Behaviour and Structure of Dicyanate-Epoxy Novolac Blends
Authors: Guo Baochun , Fu Weiwen , Jia Demin , Qiu Qinghua , Wang Lei
Published: September 2018

The cure characteristics of bisphenol A dicyanate-novolac epoxy resin blends were investigated by gel time determination and dynamic DSC. The effects of the proportion on the structures of cured blends were investigated by FTIR. In situ FTIR was utilized to study the curing mechanism and curing kinetics. The results indicated the distinct catalytic effects of the novolac epoxy resin on the curing of bisphenol A dicyanate. Due to considerable amounts of unepoxidized phenol present in the novolac epoxy resin, the reactions between phenol and cyanate disturbed the formation of the co-reaction products. The curing reactions of the blends indicated by in situ FTIR did not follow the Bauer mechanism totally. A composite mechanism of triazine-epoxy insertion and epoxy-cyanate reaction indwells in the systems. The authors suggest that most of the oxazolidinone present in the blends is formed by isomerization of oxazoline rather than by insertion of epoxy into isocyanurate. The amount of epoxy resin in the blend did not alter the curing mechanism, but had significant effects on the kinetic behaviour.
The Improvement of the Fracture Behaviour of Polybutyleneterephthalate Modified by Highly Dispersed Metals
Authors: Ozden S. , Borukayev T.A. , Mashukov N.I. , Mikitayev A.K.
Published: September 2018

The failure mechanism of polybutyleneterephthalate (PBT) was improved by the addition of highly dispersed Fe/FeO to the polymer. The mechanical behaviour of the materials under impact was investigated. It was shown that the addition of Fe/FeO stabilised the failure mechanism of PBT and improved its mechanical properties. Increased interphases between crystalline and amorphous phases, decreased crystalline size, increased network entanglement density and decreased critical structural defect length were responsible for these improvements.
Reinforcement of Damaged Concrete Columns by Filament Winding of Thermoplastic Composites
Authors: Friedrich K. , Glienke N. , Flöck J. , Haupert F. , Paipetis S. A.
Published: September 2018

An experimental study was conducted to compare various composite systems with different fibres (E-glass and carbon) in two different thermoplastic matrices (PPS, PEEK) for their strengthening efficiency for wrapped concrete columns. The results indicated that the use of E-glass fibres within a polyphenylenesulfide matrix to externally reinforce concrete columns is quite effective. The carbon fibre PEEK based system does not show much improvement in the load carrying capacity. The thickness of wrap/radius of concrete column-ratio also has an influence on the strengthening efficiency. For example ten layers of glass fibre/PPS-tapes resulted in a five fold improvement of the compressive strength of the non-reinforced concrete. Predamaged samples with the same amount of reinforcement were still 4.5 times stronger than the undamaged, non-reinforced concrete.
Polypropylene and Aliphatic Polyester Flax Fibre Composites
Authors: Hodzic A. , Shanks R. A. , Leorke M.
Published: September 2018

Composite materials have been prepared from hydrophobic and hydrophilic polypropylene with flax fibres, where the flax fibres have been used with and without silane surface treatment. Other comparable composites have been prepared from poly(lactic acid) and poly(ethylene succinate), recently developed biodegradable polymers with promising mechanical properties. The polar polymers were found to provide better wetting of the surface of the flax, regardless of the surface treatment. Differential scanning calorimetry (DSC) was used to study the crystallisation and melting of the composites compared with the pure polymers. The surface wetting of the fibres and morphology of the composites was studied by scanning electron microscopy (SEM) and optical microscopy. Mechanical properties were studied using dynamic mechanical analysis (DMA). It was found that the relatively low density flax fibres provide efficient reinforcement compared with that expected from analogous glass fibre composites. The influence of the transcrystalline interphase on the dynamic storage modulus was found to be important.
Studies on Mechanical Properties of Discontinuous Glass Fiber/Continuous Glass Mat/Polypropylene Composite
Authors: Zhou Xiaodong , Lin Qunfang , Dai Gance
Published: September 2018

The mechanical properties of discontinuous glass fiber/continuous glass fiber mat/polypropylene composites were investigated. The mechanical properties increased with increasing areal weight of the continuous glass mat, whereas the suitable content of discontinuous fiber was also depended on the mat areal weight. The impact strength of composites initially decreased due to the addition of discontinuous glass fiber, but increased when the content of discontinuous glass fiber further increased. Comparisons between the 4 mm discontinuous fiber length and the 12 mm fiber showed that the longer discontinuous glass fiber was advantageous to the mechanical properties of composite system. The modification of the interfacial adhesion between reinforcements and matrix resin by using functionalized polypropylene played a significant role in improving the mechanical properties of the composites. But the impact strength decreased above 5% of MA-g-PP level (with respect to matrix resin). It was also found that using a matrix resin with a high melt index was beneficial impregnation with the mechanical properties improving accordingly.
Study of Utilization of Ground EVA Waste as Filler in NBR Vulcanizates
Authors: Moreira Viviane Xavier , Soares Bluma Guenther
Published: September 2018

Rubber blends containing nitrile rubber (NBR) and ground ethylene-vinyl acetate copolymer waste (EVAW) from the footwear industry have been prepared over a wide range of composition (up to 90 phr of waste component). The ground EVAW had particle size in the range of 100-350 mm and a gel content of 60±5%. The effect of different amounts of EVA waste on the tensile strength, elongation at break, hardness, tear strength and dynamic mechanical properties was studied. EVAW had a good reinforcing effect on the NBR matrix. A combination of optimum tensile properties, resistance to solvent penetration and dynamic mechanical properties, such as storage modulus and loss tangent was achieved by introducing 50 phr of EVAW in the NBR matrix. This composition also presents a more uniform morphology, as indicated by scanning electron microscopy.
Cyclomatrix Phosphazene Polymers via Alder-ene Reactions
Authors: Nair C.P. Reghunadhan , Sunitha M. , Ninan K. N.
Published: September 2018

Cyclomatrix phosphazene polymers were synthesized by the Alder-ene reaction between tris(2-allylphenoxy)triphenoxy cyclotriphosphazene (APCP) and bis(4-maleimido phenyl) methane (BMM). APCP was synthesized from hexachlorocyclotriphosphazene by sequential reaction with sodium phenolate and sodium (2-allylphenolate). It was co-cured in various stoichiometric ratios with BMM. The cure of the APCP/BMM blend was characterized by differential scanning calorimetry, dynamic mechanical analysis, and rheometry. The polymers exhibited good thermal stability and anaerobic char yield. Although allylphenoxy phosphazene led to early initiation of thermal decomposition, it was conducive to a slow rate of thermal erosion and higher char residue. The cured polymers showed a Tg in the range of 240-250°C. They formed good uni-directional composites with glass fibres, although the phosphazene was found to marginally decrease the inter-phase bonding.
Molecular Transport of Aromatic Hydrocarbons through Ethylene Propylene Diene Terpolymer
Authors: Kumar P.V. Anil , Varughese K.T. , Thomas Sabu
Published: September 2018

The transport behaviour of aromatic hydrocarbons in crosslinked ethylene propylene diene terpolymer (EPDM) has been studied in the temperature interval of 28-60°C. EPDM rubber was vulcanized by four different systems viz, Conventional (CV), Efficient (EV), Semi-efficient (SEV) and Sulphurless (S-less). The samples were cured to the same crosslink density. EPDM vulcanized with the sulphurless system showed highest solvent uptake tendency and that vulcanized with semi-efficient system showed the lowest. The influence of penetrant size on sorption behaviour of EPDM has been examined. In all systems the mechanism of diffusion showed an anomalous behaviour. From the diffusion data, the activation energies of diffusion and penetration, enthalpy and entropy of sorption, interaction parameter etc. were evaluated. Comparison between theoretical and experimental diffusion results were carried out.
A Fresnel's Reflection Optical Fiber Sensor for Thermoset Polymer Cure Monitoring
Authors: Vacher S. , Molimard J. , Gagnaire H. , Vautrin A.
Published: September 2018

The paper presents a novel optical sensor that can perform real-time measurements of the degree of cure of an epoxy resin used as a matrix in fiber reinforced polymer composites. This sensor is based on the Fresnel's reflection at the end of an optical fiber. An increase in the degree of cure induces a corresponding increase in the density of the resin and therefore an increase in the measured reflected light intensity. The response of this optical sensor is shown to be in agreement with a well-established method, namely the Differential Scanning Calorimetry (DSC). In addition, a calibration method for the optical sensor in service is proposed. This calibration takes advantage of the heating phase of the epoxy resin at the beginning of the process. Due to its low intrusivity, this sensor can be easily embedded into a composite material to monitor the resin cure in-situ.
The Preparation of Self-Reinforced Sisal Fiber Composites
Authors: Lu Xun , Zhang Ming Qiu , Rong Min Zhi , Yue Da Lei , Yang Gui Cheng
Published: September 2018

To prepare self-reinforced sisal composites, sisal fibers were cleaned, treated with NaOH solution, and then benzylated with benzyl chloride. In this way, the skin layers of the fibers were converted into thermoplastic material while the core of the fiber cells remained unchanged. Under the circumstances of hot pressing, self-reinforced all-plant fiber composites of sisal can be prepared, in which plasticised sisal serves as matrix and the unplasticised cores of the fibers as reinforcement. In this work the effect of the reaction conditions, such as alkalinity, temperature and the extent of benzylation, was studied in detail. The roles of quaternary ammonium salts and γ-ray irradiation treatment on the efficiency of benzylation were also taken into account. In addition, structural characteristics, melt flow and mechanical properties of the modified sisal and their composite sheets were analysed. It was found that a balance between melt processability and the reinforcing effect of the benzylated sisal fibers was required.
Compression Failure Mechanisms of 3-D Angle Interlock Woven Composites Subjected to Low-energy Impact
Authors: Chiu C. H. , Lai M. H. , Wu C. M.
Published: September 2018

Instrumented drop weight impact and compression-after-impact tests (CAI) were conducted to assess the impact performance, compression failure mechanisms and residual compression strength of three-dimensional (3-D) interlock carbon woven/epoxy composites. Comparative evaluations were also contrasted with those for conventional two-dimensional (2-D) plain woven/epoxy laminated composites. The results show that the 3-D interlock woven composites exhibited a smaller impact damage area and higher % residual strength than the 2-D woven laminated composites. The improvements were attributed to the larger crimp-angle and interlacing structure of the 3-D interlock woven composites, which inhibits delaminated propagation along the plane direction. Besides, the fact that the 3-D interlock woven structure prevents buckling of the fibre tows under compressive load also contributes to the CIA performance.
Surface Smoothness of Glass Mat Reinforced Polypropylene Stampable Sheet
Authors: Yamaguchi Susumu , Tanigaki Etsuko , Hamada Hiroyuki
Published: September 2018

Stampable sheets can be made consisting of polypropylene (PP) plies and long glass fibre mat plies. Because stampable sheet is recyclable, and it shows good mechanical properties and processability, it is used for automotive products. However, products made of stampable sheet do not have sufficient surface smoothness, so they are not used for exterior parts that require high surface quality. In this study, the moulding conditions needed for good surface smoothness was investigated. The results indicated that surface smoothness is affected by mould temperature. When the mould temperature was near the melting temperature of the resin, the products had high surface smoothness, but this condition was not appropriate for mass production because it lengthened the production cycle too much Finally, we proposed suitable moulding conditions.
A Literature Review of Pineapple Fibre Reinforced Polymer Composites
Authors: Arib R. M. N. , Sapuan S. M. , Hamdan M. A. M. M. , Paridah M. T. , Zaman H. M. D. K.
Published: September 2018

A literature review of the development, mechanical properties and uses of pineapple leaf fibre (PALF) reinforced polymer composites is presented in this paper. The mechanical properties of PALF composites as determined by various researchers are discussed, together with chemical, thermal and physical properties. Both thermosetting and thermoplastic resins have been used as matrices for PALF composites. Most of the work surveyed used short PALF. Manufacturing methods such as injection moulding, hand lay up and compression moulding were usually employed for making composite samples.
Crystallinity of Polypropylene-Silica Ash Composites Affected by the Mixing Conditions – DSC Studies
Authors: Chaudhary D.S. , Jollands M.C. , Cser F.
Published: September 2018

For particulate polymeric composites, mixing is a crucial step to be optimised; and in the process-control stage, identification of the factors that influence mixing is important for a deeper understanding of the composite mechanical performance. A mixing study of a hydrophobic polymer matrix (polypropylene) filled with a hydrophilic particulate-filler (silica from rice husk ash) was carried out using a batch mixer at a constant filler fraction of 20% (w/w). The study involved varying the mixing-time, screw speed and mixing-chamber temperature used to prepare the composites.

Mechanical analysis of the samples showed that the tensile strength and modulus values were dependent on the mixing conditions. Furthermore, DSC studies of the samples revealed that the degree of crystallinity was also affected by the mixing conditions. The observed increase in the tensile strength was attributed to the increased filler-matrix interactions; however, there was difficulty in analysing how the mixing conditions influenced the tensile strength because of a lack of extensive data on filler dispersion. The increase in crystallinity, as affected by mixing conditions, was thought to improve the filler-matrix interaction leading to an increased tensile modulus. Interestingly, samples showed permanent morphological changes after their previous thermal histories were erased, suggesting that there was significant interaction between the silica ash particles and the polymer matrix, even though they are quite incompatible.

A statistical analysis based on the tensile data was carried out to optimise the state of mixing. The results indicate that (i) the optimised state of mixing correlated with higher crystallinity and (ii) changes in the parameters of physical mixing might significantly affect the homogeneity and crystallinity, both of which are related to the mechanical performance of the composites. Furthermore, reducing the particle size of the silica ash was also found to increase the crystallinity, which was in turn related to the improved tensile properties of the composites.

The investigation attempts to highlight that for apparent incompatible system, homogeneity is very important but it alone cannot explain the moderate filler-matrix interactions and filler bonding characteristics that are known to contribute to improved tensile properties. Somehow, composites mechanical properties are improved by optimising the physical mix-state, and by modifying the particle size but it seems like that the net effect is due to increased interactions. In any case, it is clear that optimisation of interactions can be achieved by obtaining a homogeneous phase.
Relationship between Filler Loading and Morphology of the Interphase in Polyethylene-Chalk Composites
Authors: Kozak Maciej , Danch Adam , Osoba Wojciech , Domka Ludwik , Stelzer Franz , Jurga Stefan
Published: September 2018

Mineral fillers such as kaolin or chalk have been commonly used in the polymer industry as additives to improve polymer mechanical properties and, at the same time, reduce the cost of raw materials. The problem is that the hydrophilic surface of the filler hinders its introduction into the polymer matrix. The paper reports a study of low density polyethylene (LDPE) composites with a natural chalk content of up to 40% wt. The morphology of the filler molecules and the microstructure of the composites were determined by scanning electron microscopy (SEM). The distribution of the filler molecules was estimated by light scattering. The mean diameter of the filler particles was 926.3 nm and their polydispersity was 0.101. The thermal and mechanical properties of the composites were characterised by differential scanning calorimetry (DSC) and dynamic mechanical thermal analysis (DMTA). The enthalpy of melting, ΔH *, decreased by about 8% when the amount of filler was 10 wt% in the sample (PE10). However, no difference was recorded between the ΔHm value of the sample with 40 wt% content of filler (PE40), and the value for PE10. In LDPE composites with 40% of chalk, the free space in the interphase is reduced, slightly increasing the chain mobility in comparison with that in the composite with 10% of chalk.
Effect of Injection Speed on Internal Structure and Mechanical Properties in Short Glass Fibre Reinforced Polyamide Injection Mouldings
Authors: Kuriyama Takashi , Mizoguchi Machiko , Ogawa Toshimitsu
Published: September 2018

Injection mouldings of glass/polyamide can have heterogeneous features such as skin/core structures, depending on the injection moulding conditions. The structure of glass fibre reinforced polyamide injection mouldings is discussed on the basis of the results of acoustic emission and fractographic observations associated with static and fatigue testing. The heterogeneous structures identified by variations in fibre distribution were affected by injection moulding speed. The mechanical properties and the fatigue life were also affected by the injection speed because there is a strong relationship between the internal structure and the fracture behaviour. In particular, the existence of resin rich regions dominates the fracture behaviour in both tensile and fatigue testing.
The Influence of Polyester Resin Properties on the Stress Corrosion Resistance of Glass Fiber Reinforced Composites
Authors: Bogner Ben R. , Pretzer Wayne R.
Published: September 2018

Resin properties, such as heat deflection temperature (HDT) and tensile elongation, can affect composite lifetime under conditions of sustained stress at various temperatures in an aqueous environment. Measurement of time to failure of unidirectional glass fiber reinforced composite rods comprising E-glass fiber strands and one of a series of isopolyester resins suggests a correlation between stress, time to failure, and the temperature differential between the resin HDT and the exposure temperature. Time to failure decreases significantly at moderate relative stress as the temperature differential (HDT – exposure temperature) becomes less than 10 °C.
Buckling and Ultimate Failure of Thin-Walled Pultruded Composite Columns
Authors: Hassan Nahla K. , Mosallam Ayman S.
Published: September 2018

This paper presents the results of an investigation on the buckling behavior of concentrically loaded thin–walled pultruded fiber reinforced polymer (PFRP) composite columns. Both open- and closed-web columns were evaluated. Finite element (FE) analysis and theoretical predictions are presented and correlated with experimental data. Good agreement between theoretical, analytical and experimental results was achieved. The paper also presents design guidelines to determine the bending stiffness and the critical buckling load for pultruded composite columns. In addition, a discussion on the axial strength of unidirectional PFRP columns and identification of different modes of failure are presented.
How Many Monomer Repeat Units are Necessary for Reliable Molecular Dynamics Simulation?
Authors: Kwon Y. W. , Harrell A. F.
Published: September 2018

This study was an attempt to answer the question, “How many monomer repeat units are necessary in molecular dynamics simulation in order to obtain reliable (i.e. repeatable) solutions?” A series of numerical tests was conducted to provide an answer. Based on the numerical results, reliable solutions required approximately ten thousand monomer repeat units at minimum, which was the sum of the monomer units in every polymer chain molecule. It did not matter much whether there were longer chain polymer molecules in a small quantity or shorter chain polymer molecules in a large quantity. What was critical was the total number of monomer repeat units. For a particle reinforced composite that consists of metallic atoms embedded in a polymer matrix, the minimum number of total monomer repeat units in the polymer matrix was approximately five thousand for reliable solutions.
Recycling of Glass-fibre Reinforced Phenolic Prepreg Waste. Part 2. Milled Prepreg as Functional Filler in PP and PA6
Authors: Gröning Mikael , Hakkarainen Minna , Albertsson Ann-Christine
Published: September 2018

Phenolic resin impregnated glass-fibre prepreg waste was milled and used as reinforcing filler in polypropylene (PP) and polyamide 6 (PA6). Prepreg was particularly suitable to be used as filler in PA6. The fibres were homogeneously distributed during compounding and the addition of 20 wt% prepreg increased the tensile strength of PA6 by 63%, from 52 MPa to 85 MPa. Milled prepreg alone did not significantly increase the tensile strength of PP. However, if compounded together with maleic anhydride grafted polypropylene (PP-g-MA, Epolene G3003) compatibiliser, prepreg can be used as reinforcing filler in PP as well. Addition of 20 wt% prepreg together with 5 wt% Epolene G3003 increased the tensile strength of PP from 26 MPa to 43 MPa.

In order to mill the prepreg for compounding with thermoplastics it has to be cured. A 2 kg batch of prepreg had to be cured for at least 2 hours at 200 °C to prevent the phenolic resin from falling off the glass-fibres. Milling should be performed using screens with holes larger than 3 mm in diameter to reduce the amount of prepreg fibres shorter than 2 mm, as they jam the hopper when feeding the recyclate to the extruder. The initial prepreg fibre length is of little importance to the composite mechanical properties, as the fibres are shortened to approximately the same length during compounding.
Epoxy/Glass Resin Injection Pultrusion Simulation
Authors: Rahatekar S.S. , Roux J.A.
Published: September 2018

Injection pultrusion is a continuous process for manufacturing composite materials. To produce good quality parts it is essential that complete wet out of the reinforcement fibers is achieved in the injection chamber. To achieve good wet out of the fibers, knowledge of the magnitude of the injection pressure is quite important. The present work presents the impact of pull speed, fiber volume fraction, resin viscosity and compression ratio (taper) of the injection chamber on resin fiber wet out within the injection chamber for epoxy/glass rovings composites. The recommended injection pressures for complete wet out are predicted for specified sets of processing parameters. Darcy's law for flow through porous media is employed to simulate the pressure field and flow field for the fiber/resin system corresponding to injection pultrusion. Different permeability models1,2 were used to determine the transverse permeability and the longitudinal permeability employed in the numerical simulation. The governing equations were solved employing the finite volume method to predict the resin pressure field, resin velocity field, and resin moving flow front.