Polymers and Polymer Composites
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Published By Sage Publications

1478-2391, 0967-3911

2022 ◽  
Vol 30 ◽  
pp. 096739112110609
Author(s):  
Atik Mubarak Kazi ◽  
Ramasastry DVA

The influence of fibre orientation on physical, mechanical and dynamic mechanical properties of Hibiscus sabdariffa fibre composites has been studied. The composites with longitudinal (0°), transverse (90°) and inclined (45°) fibre orientation were prepared using the hand layup technique. ASTM standards were used for characterization of continuous Hibiscus sabdariffa fibre composites. The composite with longitudinally placed fibres yields improved mechanical characteristics. The addition of longitudinal (0°) oriented continuous Hibiscus sabdariffa fibres to the epoxy enhances tensile strength by 460%, flexural strength by 160% and impact strength by 603% compared to neat epoxy. The longitudinal (0°) fibre oriented composite offers higher resistance to water absorption and thickness swelling compared to other types of composites. All continuous Hibiscus sabdariffa fibre epoxy composites possess an improved storage modulus than the neat epoxy resin. The glass transition temperature of continuous Hibiscus sabdariffa fibre composites is 8%–31% lower than that of neat epoxy. Scanning electron microscopy (SEM) images confirm the existence of voids in the matrix, fibre pullout and crack propagation near the fibre bundle, which indicates the stress transfer between fibre and matrix is non-uniform.


2022 ◽  
Vol 30 ◽  
pp. 096739112110627
Author(s):  
Sirvan Mohammadi

In this paper, considering different parameters and various patch materials, the effect of disbond on the efficiency and durability of a composite patch repair is investigated in mode I and mixed-mode. One of the most important aspects of the composite patch repair is the bond strength. Repair patch disbond may occur at the patch edges or the crack site. At first, the effect of different parameters such as repair patch material and Young’s modulus and thickness of the adhesive on the efficiency and durability of the patch is investigated. Then, the effect of the disbond site on the stress intensity factor (patch efficiency) and adhesive stress (patch durability) is analyzed in both modes I and II. The results show that disbond at the crack site leads to a further reduction in patch efficiency compared to the patch edge disbond, but when separation occurs at the patch edge, the adhesive stress and the disbond growth rate are higher. Also, when 15% of the patch is separated in the crack site, for the longitudinal and transverse disbond modes, the mean KI is increased by 8 and 4%, respectively, compared to the state without disbond. Thus, the longitudinal disbond mode is more critical.


2022 ◽  
Vol 30 ◽  
pp. 096739112110633
Author(s):  
Deepak SampathKumar ◽  
Thirumalaikumarasamy Duraisamy ◽  
Thirumal Pattabi ◽  
AshokKumar Mohankumar

At present, puncture resistance and rheological performance of shear thickening fluid (STF) is an essential design requirement for a soft armour material (target sample). The target sample is prepared with a dip and dry process of STF impregnated woven polypropylene (PP) fabric. These samples were tested and compared with neat PP fabric. The penetration depth of target samples is highly sensitive to the coefficient of friction between the indenter’s nose shape geometry and the target sample. The STF is prepared by mechanical dispersion of synthesized microsphere silica microparticles at a volume fraction of 57% in polyethylene glycol (400 g/mol). The rheological response indicates that the prepared concentration of silica microparticles in the STF suspension is observed to have a better shear thickening effect. The viscosity of suspension is highly sensitive to silica aspect ratio, volume fraction and particle size distribution in this work. Tensile tests along with puncture resistance with different indenter nose shapes geometry (hemispherical, elliptical, flat and conical) have been performed in the present study. Results indicate that the energy absorption is more with the hemispherical indenter and less with that of the conical indenter, which is attributed to the minimum surface area of contact as compared to all other indenters. A total of 16 number of fabricated target samples with various coating thicknesses of STF impregnated fabrics achieved the desired tensile strength, modulus and puncture resistance.


2022 ◽  
Vol 30 ◽  
pp. 096739112110631
Author(s):  
Azin Paydayesh ◽  
Leyla Heleil ◽  
Arezoo Sh Dadkhah

In recent years, polymeric hydrogels are widespread in the field of biological materials such as wound dressing and wound care. In this work, we report for the first time the preparation and application of pHEMA nanocomposite hydrogels containing iron oxide nanoparticles as wound dressings. For this purpose, nanocomposite hydrogels based on poly (hydroxyl ethyl methacrylate) (pHEMA) and various amounts of 5, 10, and 15 wt% iron oxide nanoparticles were successfully prepared via radical polymerization. The structure and morphology of nanocomposite hydrogels were determined by Fourier transform infrared spectroscopy (FTIR) and field emission scanning electron microscope (FE-SEM), respectively. The results of gel fraction and the degree of swelling of hydrogels demonstrated that the gel percentage of pHEMA increased, and the degree of swelling decreased with increasing the percentage of nanoparticles. The WVRT and the porosity of hydrogels decreased by increasing the quantity of nanoparticles and were suitable for wound dressing applications. The effect of iron oxide nanoparticles on the mechanical properties of nanocomposite hydrogels was also studied using compression test and hardness shore A durometer. The results indicated that the compression strength, modulus, strain, and hardness are steadily increasing compared to pure hydrogel by adding nanoparticles. The maximum increase was obtained for a hydrogel sample with 15 wt% iron oxide nanoparticles. Antibacterial properties and biocompatibility were determined by the disk-diffusion and MTT assay methods, respectively. Based on the results, nanocomposite hydrogels exhibited higher percentages of cell survival and better antibacterial properties compared to pure pHEMA.


2022 ◽  
Vol 30 ◽  
pp. 096739112110627
Author(s):  
Ramkumar Yadav

The objective of the article is to explore the fabrication of dental restorative composite materials and the ranking order using the preference selection index (PSI) as a multi criteria decision making (MCDM) technique under a set of conflict performance defining criteria (PDCs). The polymer matrix of the dental restorative composite was prepared using bisphenol a-glycidyl methacrylate (55 wt.%), triethylene glycol dimethacrylate (44 wt.%), camphorquinone (0.3 wt.%), and ethyl 4-(dimethylamino) benzoate (0.7 wt.%). Five different dental restorative composite material compositions were fabricated using hybrid nSiO2-TiO2 particulates with a variation of nSiO2 (0, 2, 4, 6, 8 wt.%) while TiO2 is constant (15 wt.%). The results revealed that an increasing trend has been found in compressive strength, flexural strength, Vickers hardness, etc., while a decreasing trend has been shown in depth of cure, polymerization shrinkage, degree of conversion etc. The performance analysis of five dental composite formulations via the PSI method shows the following ranking order: nS4 > nS6 > nS2 > nS0 > nS8. The obtained experimental results are associated with the ranking order of the different sets of dental composite formulations. Hence, the preference selection index approach is one of the best techniques among MCDM techniques for ranking under different PDCs.


2022 ◽  
Vol 30 ◽  
pp. 096739112110632
Author(s):  
SI Radwan Torab ◽  
MM Shehata ◽  
HH Saleh ◽  
ZI Ali

Poly (vinyl alcohol) is blended with ethylene glycol by casting method to form PVA-EG blend films. These films were irradiated by both N2 ion beam extracted from dc ion source at different ion fluences and γ-rays with various irradiation doses. The effects of ion beam and γ-rays irradiation on the thermal, micro-hardness, and gel fraction properties of PVA-EG blend films were investigated. The gel fraction % and micro-hardness increase with increasing the γ-rays doses up to 150 kGy and then decreased, where they increased at all fluences of ion beam irradiation. The improvement in the gel fraction percentage and micro-hardness suggest that PVA-EG blend films exhibited a crosslink density. The thermal behavior was examined by thermogravimetric analysis and it shows different thermal patterns depending on the type and dose of radiation. The thermal stability parameters of γ-rays- and ion beam-irradiated PVA-EG samples were evaluated using the Ti, Ts, T0.5, Tf temperatures, and activation energy (Ea) values. The thermal stability parameters were dependent on both the type and extent of irradiation dose and fluence. Finally, there is a good agreement between the obtained results from different measurement techniques.


2021 ◽  
pp. 096739112110576
Author(s):  
Rajeshkumar Selvaraj ◽  
Kamesh Gupta ◽  
Shubham Kumar Singh ◽  
Ankur Patel ◽  
Manoharan Ramamoorthy

This study investigates the free vibration responses of laminated composite sandwich beam with multi-cores using experimental and numerical methods. The laminated composite face sheets are made by using hand layup method. An experimental modal test has been carried for different configurations of multi-core sandwich beams under different end conditions. The single-core and multi-core sandwich beams has been modeled and the natural frequencies of sandwich beams are determined using ANSYS software. The numerical model is verified by comparing the obtained natural frequencies with experimental results. The numerical and experimental results indicate that the multi-core sandwich beam greatly influences the structural stiffness compared with single-core sandwich beam under different end conditions. Furthermore, the influence of several parameters such as the end conditions, thickness of the core layer, and stacking sequence on the natural frequencies of the various configurations of the multi-core sandwich beams are presented.


2021 ◽  
pp. 096739112110598
Author(s):  
Gorka Díez-Barcenilla ◽  
José L Gómez-Alonso ◽  
Koldo Gondra ◽  
Ester Zuza

The technology of epoxy tooling, at present under continuous development, is used for the rapid manufacture of cost-effective tools for small batch production. It is a valid alternative with no need for expensive investment in metallic moulds for the development of new products. Current investigations are focused on improvements to the production system, improved tool performance, the cost reduction of moulds and tool manufacturing sustainability. In this paper, both the advantages and the disadvantages of epoxy tooling in injection moulding, wax injection, metal stamping and hot embossing are compared with conventional techniques. Following a brief introduction of rapid tooling technologies, the latest advances of epoxy tooling and their implementation in different manufacturing processes are all analysed. These developments refer to the production of new ad-hoc epoxy composites, increased productivity using conformal cooling channels, the reduction of the tooling manufacturing costs through waste reuse and the emerging industry 4.0 technologies for smart manufacturing and tooling. The main objective is to identify both the challenges facing epoxy tooling techniques and future research directions.


2021 ◽  
pp. 096739112110486
Author(s):  
Anjaly Mathew ◽  
Beena Mathew ◽  
Ebey P Koshy

Polymer-supported reagents have become popular in synthetic organic chemistry over the past decades. But the kinetics of polymer-supported reactions is slow compared to solution phase synthesis because of the poor diffusion of the reactants through the macromolecular polymer matrix. This difficulty can be reduced to a great extent by performing polymer-supported reactions under microwave (MW) conditions. The present work is focussed on the design and development of an innovative, powerful, MW stable and recyclable polymeric reagent prepared by attaching bromoderivative of 2-oxazolidone into the macromolecular matrix of polystyrene. 3% cross-linked polystyrene was prepared by free radical aqueous suspension polymerization technique using tetra ethylene glycol diacrylate as the cross-linking agent and the resulting beads were functionalized by chloromethylation followed by reaction with 2-oxazolidone. Bromine functionality is introduced into the polymer by treating with bromine in carbon tetrachloride. The synthetic utility of the prepared polymeric reagent was demonstrated by the oxidative coupling of thiols to disulfides under MW irradiation. No over oxidation was observed in this protocol and the utilization of polystyrene support simplifies work up and product isolation. The synthesised polymeric reagent displayed good cyclic stability up to five cycles without any substantial decrease in bromine content and satisfactory storage stability under normal laboratory condition. Moreover this may be the first report that uses MW energy for the oxidation of thiols to disulfides using polymer-supported reagents. [Formula: see text]


2021 ◽  
pp. 096739112110461
Author(s):  
C Rajesh ◽  
P Divia ◽  
S Dinooplal ◽  
G Unnikrishnan ◽  
E Purushothaman

Dynamic mechanical properties of polymeric materials are of direct relevance to a range of unique polymer applications. The aim of the study is to investigate the dynamic mechanical properties of composites of short nylon 6 fiber with acrylonitrile butadiene rubber (NBR). The storage modulus (G′), loss modulus (G″), and the damping factor (tan δ) have been analyzed with reference to the effects of fiber loading, curing systems, and bonding agents over a range of temperature and at varying frequencies. The storage modulus increases with increment in fiber loading, whereas loss modulus and damping factor decrease. The glass transition temperature shifts to higher temperature upon increment in fiber loading. Dicumyl peroxide (DCP)–cured composites show higher storage modulus and lower damping than the corresponding sulfur-cured one. The addition of hexa-resorcinol and phthalic anhydride as bonding agents enhances the dynamic mechanical properties of the composites. The experimental results have been evaluated by comparing with Einstein, Guth, and Nielsen models.


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