Shore-D Hardness Research Articles

Evaluation of mechanical properties of sandwich structures with polyethylene terephthalate and polyvinyl chloride core

Sandwich structures are comprised of two external faces/skins (usually made of synthetic fiber/resin) and a core, being lightweight and with high stiffness. These structures when based on a foam core are commonly processed using liquid molding techniques. In this study, the light resin transfer molding process is used to inject the polymeric resin (vinyl ester) into the porous cavity between the impermeable core and the mold walls. The main goal of the present work is to study the effect of different types of cores (polyvinyl chloride (PVC) and polyethylene terephthalate) and faces (glass fiber cloths or mats) on the mechanical characteristics of the sandwich structures. Specimens were subjected to flexural, flatwise and edgewise compression, and Shore-D hardness testing. General comparison between the different core materials indicated higher flatwise compressive, flatwise tensile and shear strength of the PVC. However, the effect of the core on the properties of the sandwich structure, e.g. flatwise compressive and edgewise compressive strength, was much less evident.

Studies of Abrasive Water Jet Machining (AWJM) Parameters on Banana/Polyester Composites Using Robust Design Concept

In this present work the banana/polyester was fabricated using hand layup method followed by compression moulding technique. The moulded composite was studied with special references to the Taguchi’s method for optimizing the cutting parameters of AWJM for minimizing the kerf width and kerf taper. An L9 (34) orthogonal array was selected to conduct the experiment with the identified significant parameters such as Feed rate, Pressure, Standoff distance and Abrasive Method. The significance of cutting parameters was analysed with the help of ANOVA. The optimum process parameters were identified with the help of signal to noise ratio (SN). The decreasing value of hardness was observed after the machining of composite using shore-D hardness tester. The influence of abrasive particle was found to be predominant affecting the performance of the output quality measures.

Parameters optimization in FSW of polypropylene based on RSM

Purpose – The purpose of this paper is to weld polypropylene (PP) material by friction stir welding (FSW) process. The input process parameters considered were: tool pin profile, feed rate and tool rotational speed and the process output characteristics were tensile strength, Shore-D hardness, Rockwell hardness, Izod strength, Charpy strength and nugget area. Design/methodology/approach – Optimization of process parameters were carried out based on response surface methodology (RSM) and significant parameters were obtained by performing analysis of variance (ANOVA). Findings – The optimized results were the threaded pin profile for feed of 60 mm/min and tool rotational speed of 1,500 rpm. A confirmation test was carried out to verify the optimized results. Originality/value – In this paper, the process parameters were optimized based on RSM. This is newly adopted optimization techniques in the FSW process of PP materials and also it gives better results.

Dry and Residue-Free Cutting with High-Pressure CO<sub>2</sub>-Blasting

Jet cutting with high-pressure CO2 jets has the potential for a dry and residue-free machining of materials. However, a high-pressure CO2 blasting plant as well as experimental expertise for the continuous jet cutting with high-pressure CO2 at atmospheric conditions are not available. A pilot plant for the continuous jet cutting with liquid carbon dioxide was developed and realized at the Fraunhofer-Institute for Production Systems and Design Technology. Identical cutting tests were carried out in polyurethane blocks of different Shore D-hardness and density with high-pressure CO2 and water jets. Based on the first results in polyurethane blocks the tests were extended to cutting carbon fibre reinforced plastic plates with the high-pressure CO2 jet. Finally the possibilities and limits of the high-pressure CO2 jet cutting were summarised.

Static and Dynamic Characterization of Cellulose Nanofibril Scaffold-Based Composites

The reinforcement potential of novel nanocellulose-based scaffolding reinforcements composed of microfibrils 5 to 50 nm in diameter and several microns in length was investigated. The cellulose nanofibril reinforcement was used to produce a three-dimensional scaffolding. A hybrid two-step approach using vacuum pressure and hot pressing was used to integrate the nanocellulose reinforcements in a liquid molding process with an epoxy resin to manufacture composites containing fiber volume contents ranging from 0.6% to 7.5%. The mechanical properties were studied using three-point bending. The Shore-D hardness test and differential scanning calorimetry (DSC) were used to investigate the curing response and its relation to the mechanical properties. Dynamic mechanical analysis (DMA) with a three-point bend setup was used to investigate the viscoelastic behavior of the nanocellulose composite samples at various temperatures and dynamic loadings. The results using the proposed liquid resin manufacturing method for processing the nanocellulose composites showed an increased modulus and a lower strain-to-failure compared to neat resin. Dynamic testing showed a trend of lower tan delta peaks and a reduction in the glass transition temperature with the addition of nanocellulose reinforcement.

EFFECT OF KAOLIN ON THE MECHANICAL PROPERTIES OF POLYPROPYLENE/ POLYETHYLENE COMPOSITE MATERIAL

In this work, the mechanical and water absorption properties of polymer blend polypropylene (PP) and low density polyethylene (LDPE) at constant ratio (50/50) composites as a function of kaolin powder weight content in the grain size (100,120 µm) were investigated. Polymer composite was fabricated by mixing polymer blend ( PP\LDPE) with (0, 1, 3 ,5, 10, 14) wt.% of kaolin powder to obtain desirable properties. The parameters such as tensile strength, tensile modulus, elongation at break , yield stress, impact strength, shore D hardness and water absorption test were carried out on the prepared samples. The results showed that the addition of kaolin powder to the polymer leads to increase the tensile strength, modulus of elasticity, shore-D hardness and impact strength and it decreases the % elongation at break,. Water absorption of the composites behaves as function of time (days) has also been investigated, and it increases by increasing immersion time for the same filler content, while the absorbed amount of water increases, by increasing the wt% of kaolin at constant immersion time.

Setting characteristics of vinyl-polysiloxane interocclusal recording materials

ObjectivesTo investigate the elemental and molecular composition, curing efficiency, setting shrinkage strain and hardness of vinyl-polysiloxane interocclusal recording materials. MethodsThe materials tested were Blu-Mousse Classic/BMC, Exabite II NDS/EXB, Futar Scan/FTS, O-Bite/OBT, Occlufast Rock/OFR, R-Si-Line Metalbite/RMB and Stone Bite/STB. Composition was examined by SEM/EDX and micro-ATR FTIR. Curing efficiency (n: 7) was evaluated by micro-ATR FTIR on unset materials and following 3, 5, and 10min after mixing. Setting shrinkage strain (%S, n: 7) was evaluated by the bonded-disk method as a function of time up to 10min after mixing and Shore-D hardness measurements (n: 7) were performed at setting time and after 72h storage at room temperature. Statistical analysis was performed by one-way ANOVA and paired t-tests (a: 0.05). ResultsAll materials were particle-filled vinyl-polysiloxane composites with different elemental composition. C, O and Si were found at highest concentration in all products, whereas Al, Na, Mg, Ti and Ca were additionally detected. Curing efficiency measurements ranked the products in three statistically homogeneous groups (OFR, EXB, OBT>FTS, RMB>BMC, STB) at all time intervals, except OFR which at 5 and 10min was ranked in the second group. In all products, a statistically significant increase in %Smax values was found in comparison with %S at setting time. Strain saturation was reached by all materials at different time intervals, except from BMC and OBT. Hardness differences were detected among materials for the same time interval and between time intervals per material. SignificanceDifferences among materials were detected regarding the properties tested, which may imply variations in their clinical performance.

Aggressiveness of a 20% bioethanol 80% gasoline mixture on autoparts: II Behavior of polymeric materials

Ethanol has become one of the main components for reformulated fuels because it is able to comply with environmental regulations. Biofuels have great advantages due to their physical and chemical characteristics, raw materials and production costs. However, they also have some disadvantages, mainly in terms of their compatibility with existing materials. Some components that are normally compatible with gasoline can be degraded by the presence of ethanol in fuel. The aim of this study was to evaluate the physical and chemical behavior of different polymeric materials typically used in autoparts, exposed in a mixture of gasoline and ethanol. To evaluate the resistance to degradation of the polymer samples, a continuous immersion test was performed according to SAE 1748. The effects of the 20% ethanol −80% gasoline mixture (E20) were examined by comparing changes in gain/loss of mass and by measuring the Shore-D hardness of the material at the end of exposure. The characterization of polymers was carried out before and after exposure by using the techniques of differential scanning calorimetry (DSC), thermogravimetric analysis (TGA) and Fourier Transform Infrared Spectroscopy (FTIR). In general, polymeric materials submerged in gasoline showed negligible changes in mass. Samples of POM, HDPE, PA6/6 and PA6 exposed to E20 showed mass increases below 10%. The chemical structure and mechanical properties (hardness) of the evaluated polymers were not significantly affected by the E20 blend with the exception of PA66. Since significant changes were observed in the thermal properties of this polymer, it can be concluded that it was at the limit of compatibility.

Effect of citric acid on setting inhibition and mechanical properties of gypsum building plasters

The role of citric acid, a retarder additive used to prolong the workability and setting time of gypsum binders, was studied at concentrations of 0, 125, 250, 500, 1000, 1500 and 3000 ppm with a constant water/binder ratio. The hydration process (setting) was studied by the knife method, conductivity measurements and attenuated total reflectance infrared spectroscopy, which provided an estimation of the time it took for calcium sulphate dihydrate to be formed. Scanning electron microscopy confirmed that the gypsum microstructure varied when citric acid is used. The mechanical properties of the plaster were also studied by ultrasonic measurements, shore-D hardness, flexure and compressive strength tests. It was found that citric acid partially inhibits binder hydration from hemihydrate to dihydrate, as observed by X-ray diffraction analysis.

Effect of Treatment of Maleic Anhydride on Mechanical Properties of Natural Fiber: Polystyrene Composites

: In the present work, banana, hemp, and sisal fibers are employed as fillers for the formation of natural fiber:polystyrene composites in the ratios of 55:45, 50:50, 45:55, and 40:60 (wt/wt). The natural fibers were treated with maleic anhydride. The Young's modulus, flexural modulus, impact strength, and Shore-D hardness all decreased with increasing amounts of fibers in the natural fiber:polystyrene composites. The sisal fiber composites show the highest mechanical strength for all ratios. A maleic anhydride treatment shows significant improvement in Young's modulus, flexural modulus, impact strength, and Shore-D hardness compared with the untreated fiber composites.

Mechanical Properties of Wood Polymer Composites Prepared from Agro-Waste and HDPE

: Wood polymer composites based on untreated and maleic anhydride treated banana, hemp, and sisal fibers with HDPE resin are prepared in different ratios of 55:45, 50:50, 45:55, and 40:60 (wt/wt), respectively. Young's modulus and flexural modulus decrease with increase in fiber amount in the polymer. Maleic anhydride-treated fiber composites show highest Young's modulus and flexural modulus. The impact strength and shore-D hardness is also observed to be higher in maleic anhydride-treated fiber composites than in the untreated fiber composites.

Filler effect of potato starch and urea on degradation of linear low density polyethylene composites

Starch and urea are used as fillers, owing to their good mechanical and degradable properties, in linear low density polyethylene matrix. Composites of varying amount of starch and urea composition are prepared. Various properties like tensile strength, elongation at break, Young's modulus, shore-D hardness, and water absorption are studied. The tensile strength, elongation at break, Young's modulus, and Shore-D hardness decrease with maleic anhydride treatment of starch and urea for polymer composites. On increasing the amount of filler in the composites, the mechanical properties decrease. The soil-burial treatment of these composites also causes reduction in these properties. The absorption of water increases for one month and decreases later during the period 2–5 months. The increase in absorption might be due to the onset of degradation of composites. The degradation of the composites is also observed by the presence of grooves and pits in optical micrographs of soil-exposed composites.

The compatibilising effect of maleic anhydride on swelling and mechanical properties of plant-fiber-reinforced novolac composites

In the present work, fibers of banana, hemp and sisal are used as fillers in novolac resin. These fibers have been esterified with maleic anhydride and the effect of maleic anhydride on the swelling and mechanical properties of plant fiber polymer composites has been assessed. Higher absorption of steam and water is observed in untreated fiber composites. The Young's modulus increases with increase in fiber content up to 45 and 50% in untreated and MA treated fiber composites, respectively. The impact strength and Shore-D hardness have been found to be higher in maleic-anhydride-treated fiber composites than the untreated-fiber composites.

Coloured Glass-fibre Reinforced Composites

Coloured glass-fibre reinforced composites of conventional di-glycidylether of bis-phenol-A and novel heterocyclic pigments. 1,4-di-keto-pyrrolo[3,4-c]pyrrole (DPP) were prepared, using di-ethylenetriamine as curing agent and evaluated for their physical properties (such as density. % resin content and % void content) and mechanical properties (such as flexural strength, interlaminar shear strength and shore-D hardness). The laminates were also evaluated for their chemical resistance and electric properties. It is observed that the incorporation of DPP pigments imparts colour, but does not deteriorate the above mentioned properties of the DGEBA based glass-fibre reinforced composite.

Absorption of steam and water at ambient temperature in wood polymer composites prepared from agro-waste and Novolac

Banana (Musa paradisica), Hemp (Hibiscus cannabinus), and Agave (Agave jourcroydes) fibers were treated with Novolac resin for the formation of their composites in the ratio of 50: 50 (wt/wt). These fibers were also treated with maleic anhydride, and it was found that composites based on treated fibers showed higher absorption of steam ( at 100°C) up to 12 h; and beyond 18 h, it is less than the untreated fiber composites. However, at ambient temperature, the absorption of water is lesser for composites based on maleic anhydride-treated fiber than for composites based on untreated fibers. The SHORE-D hardness was commonly higher for composites based on maleic-anhydride-treated fibers.

Latex interpenetrating polymer networks based on polyacrylates and network II comprised of poly(styrene‐co‐methyl methacryalte)

Latex interpenetrating polymer networks (LIPNs) were prepared using the polyacrylate seed, comprising of n-butyl acrylate, methyl methacrlate, tetraethylene glycol dimethacrylate in the ratio of 55 : 45 : 0.7 by weight (wt), and with different amounts of methacrylic acid (MAA) ranging from 0 to 6% on monomer wt. basis and the copolymer of styrene and methyl methacrylate (53 : 47 by wt) as the second network, to study the effect of the increase in the hydrophilicity of the seed on the final latex properties. The swelling and polymerization of mixture of the monomers II and the crosslinker II were done at two different pHs (viz. 3.3 and 8.5). All the latexes yielded continuous films upon drying at ambient temperature. All the LIPNs possess multiphase morphology. Tensile strength and shore-D hardness have been found to increase with an increase in MAA concentration in the seed. Different properties like film formation, glass transition temperature, and tensile strength of the LIPNs thus prepared have been compared with the set of LIPNs produced using the same seed, but with polymer II comprising of the either polystyrene (PS) or poly-MMA (PMMA) homopolymer. The LIPNs having the copolymeric combination showed the combined effect of both the constituents. © 1996 John Wiley & Sons, Inc.

Latex interpenetrating polymer networks based on polyacrylates and network II comprised of poly(styrene-co-methyl methacryalte)

Latex interpenetrating polymer networks (LIPNs) were prepared using the polyacrylate seed, comprising of n-butyl acrylate, methyl methacrylate, tetraethylene glycol dimethacrylate in the ratio of 55 : 45 : 0.7 by weight (wt), and with different amounts of methacrylic acid (MAA) ranging from 0 to 6% on monomer wt. basis and the copolymer of styrene and methyl methacrylate (53 : 47 by wt) as the second network, to study the effect of the increase in the hydrophilicity of the seed on the final latex properties. The swelling and polymerization of mixture of the monomers II and the crosslinker II were done at two different pHs (viz. 3.3 and 8.5). All the latexes yielded continuous films upon drying at ambient temperature. All the LIPNs possess multiphase morphology. Tensile strength and shore-D hardness have been found to increase with an increase in MAA concentration in the seed. Different properties like film formation, glass transition temperature, and tensile strength of the LIPNs thus prepared have been compared with the set of LIPNs produced using the same seed, but with polymer II comprising of the either polystyrene (PS) or poly-MMA (PMMA) homopolymer. The LIPNs having the copolymeric combination showed the combined effect of both the constituents.

A kinetic study and the glass-reinforced composites of a liquid diglycidyl ether of bisphenol-P epoxy resin

The curing reaction of liquid epoxy resin based on l,l'-bis(4-hydroxyphenyl) cyclopentane with different amines, in the presence or absence of a fortifier, has been studied by differential scanning calorimetry (DSC). The glass-fibre-reinforced composites of liquid diglycidyl ether of bisphenol-P (DGEBP) were prepared using different amines as curing agent with/without fortifier and evaluated for their physical properties (such as density,% resin content and% void content) and mechanical properties (such as flexural strength, interlaminar shear strength and shore-D hardness). The laminates were also evaluated for their chemical resistance and electrical properties. It was found that using an epoxy fortifier (PGEHA) reduces the mechanical properties of the DGEBP-curing agent system.