Improvement In Impact Strength Research Articles

Study on Shape Memory Behavior of Ternary Poly(Lactic Acid)/Poly(Methyl Methacrylate)-grafted Natural Rubber/Natural Rubber Thermoplastic Vulcanizates

ABSTRACT Here, poly(lactic acid) (PLA)/poly(methyl methacrylate)-grafted natural rubber (NR-PMMA)/natural rubber (NR) ternary blends with co-continuous phase structure were prepared via peroxide-induced dynamic vulcanization. The good compatibility between NR-PMMA with PLA and NR and the interfacial grafting reaction during the preparation process ameliorated the interfacial compatibility between the phases. Therefore, the energy stored in the rubber phases could be effectively transferred to PLA, thus achieving an excellent shape-memory effect even under-repeated shape-memory cycles. Furthermore, by adding 10 wt% NR-PMMA, the TPVs exhibited improved impact strength and tensile strength up to 98.05 kJ/m2 and 45.2 MPa, respectively.

Preparation and Properties of BN/Si3N4/Epoxy Composites

The effect of a hybrid filler on the thermal conductivity of an epoxy composite is described. The hybrid filler, containing boron nitride (BN) particles and silicon nitride (Si3N4) whiskers with different wt% ratios (20:0, 18:2, 15:5, 10:10, 5:15, 2:18 and 0:20), was loaded into the epoxy resin. The thermal conductivities of the doped composites were higher than that of the pure EP (0.4287 W·m−1·K−1); with addition of BN and Si3N4 fillers the 10%BN/10%Si3N4/EP composites exhibited the highest thermal conductivity (1.1486 W·m−1·K−1), which was 185% and 214% that of the 20%BN/EP composite (0.6200 W·m−1·K−1) and the 20%Si3N4/EP (0.5374 W·m−1·K−1), respectively. The impact strength of the composite material 10%BN/10%Si3N4/EP also was the maximum (3.48 KJ/m2). Thus, the 10%BN/10%Si3N4/EP composites not only exhibited excellent thermal conductivity, but also slight improvements in thermal stability and impact strength. Suggesting it would be useful for thermal sensor interconnections of electronic circuits.

Kinetics of formation and viscoelastic and mechanical properties of optically transparent interpenetrating networks of poly(methyl methacrylate)/polyurethane

An optically transparent material with enhanced physical-mechanical properties was synthesized, which is based on the in situ formed sequential interpenetrating polymer networks of poly(methyl methacrylate)/polyurethane with an oligoester component. The kinetic features of polymerization of methyl methacrylate in these systems were studied. It was established that the polymerization rate of methyl methacrylate increases with an increase in the content of a polyurethane component, which results from an increase in the system viscosity. Irrespective of the content of polyurethane (15, 20 or 25 wt.%), optically transparent materials with a light transmission coefficient of about 90% were formed. The method of dynamic mechanical analysis showed that the modification of cross-linked poly(methyl methacrylate) with cross-linked polyurethane led to a decrease in the value of the elastic modulus; the value of the loss modulus being increased with an increase in polyurethane content. This indicated bot a decrease in fragility and the improvement in impact strength of the glass-like material. According to the study of physical-mechanical properties of the materials, the presence of polyurethane in their composition resulted in an increase in the impact strength and relative breaking elongation and in the reduction of the Young modulus. It was found that the interpenetrating polymer network containing 20% of polyurethane showed the best values of breaking strength, breaking elongation and Charpy impact.

Structural Characterization and Mechanical Behaviour of Sodium Hydroxide-Treated Urena lobata Fiber Reinforced Polypropylene Matrix Composites

The present study is on the production and characterization of untreated and treated Urena lobata (U. lobata) fiber reinforced polypropylene (PP) composites. The untreated and treated U. lobata/PP composites were produced by compression moulding at varying weight percents of the fibers (5, 10, 15, 20 25, 30, 35) wt%. The following characterizations were carried out on the treated and untreated U. lobata/PP composites; X-ray diffraction (XRD), Fourier Transform Infra-red spectroscopy (FTIR), and Scanning electron microscopy (SEM). Due to enhanced fiber-matrix adhesion, attributed to increased fiber roughness and crystallinity, the alkaline treated U. lobata composites showed enhanced mechanical, structural and morphological properties over the untreated U. lobata reinforced composites. Furthermore, the 30 wt% fiber loading, gave the best combination of the mechanical properties, as improvement in tensile strength (2–22 %), percentage elongation (5–26 %), and impact strength (2–19 %) was observed for the treated fiber reinforced composite compositions. Consequently, the 30 wt.% Urena lobata/PP composite is recommended for the development of PMC based automobile components.

Fabrication of well-miscible and highly enhanced polyethylene/ultrahigh molecular weight polyethylene blends by facile construction of interfacial intermolecular entanglement

To enhance the interfacial intermolecular entanglement of the polyethylene/ultrahigh molecular weight polyethylene (PE/UHMWPE) system, the blend was fabricated via a facile melt blending process in presence of UHMWPE with relatively low molecular weight (LUHMWPE). Incorporation of LUHMWPE filled molecular weight gap between PE and UHMWPE, and thus a matched viscosity gradient for the components of blend was constructed. The UHMWPE/LUHMWPE particles with remarkably decreased size and distribution were tightly embedded in PE matrix, and the interface transition area between UHMWPE and PE phase increased dramatically. Meanwhile the molecular entanglement density and viscoelasticity were improved greatly, demonstrating enhanced interfacial adhesion, interfacial intermolecular diffusion and construction of a dense chain entanglement network in blend. An obvious deformation accompanied by lots of pulling-out UHMWPE fibrils was observed on the fractured surfaces of the blend, and the mechanical property was highly enhanced by a roughly 38%/22% increase in tensile strength and a great improvement in impact strength, respectively when compared with neat PE and PE/UHMWPE. The blend was further employed to fabricate pipes, which exhibited significantly improved tensile strength both along hoop and axial direction, and the internal pressure resistance. This work provides a facile method for manufacturing PE/UHMWPE blend and pipe with promising application potentials.

Modeling of Mechanical Properties and High Temperature Wear Behavior of Al7075/SiC/CRS Composite Using RSM

The study focuses on preparing hybrid composites with aluminium alloy strengthened with solid waste Crushed Rock Sand (CRS) and SiC through the stir casting process. The weight portion of reinforcement is diverse from 0 to 6% with a step variation of 3%. The mechanical properties such as hardness, ultimate tensile strength, impact strength, flexural strength, density, and porosity were investigated on prepared composites at room temperature. Central composite design-based response surface methodology (RSM) was espoused for computing and optimizing of the weight percentage of reinforcements considering mechanical properties as responses. An arithmetical model was developed to predict the mechanical properties and the adequacy of the model was verified using analysis of variance (ANOVA). The wear behavior associate with the composite is investigated at 28˚C and 350˚C. The specific wear rate and coefficient of friction of all samples shall be correlated with the above-mentioned temperature state. The maximum density of 2.766 g/cc is recorded for a sample with 3% wt. of SiC. The level of improvement in hardness, tensile strength, impact strength, and flexural strength is 59.7%, 45.9%, 16.9%, 58.7% relative base alloy. The specific wear rate, frictional force, and coefficient of friction decrease with elevated temperature due to the creation of oxide films. The depth and width of grooves at elevated temperatures are smaller.

Incorporation of poultry eggshell and litter ash as high loading polymer fillers in polypropylene

With oil supplies needed for plastic polymer generation reducing, alterative feedstock materials are required for polymer producers. Replacement of plastic feedstock with other materials, such as fillers or functional additives, is a suitable method. Many of these materials are being derived from waste sources, including potential those derived from poultry production. Eggshell and poultry litter (incinerated into ash – PL(Ash)) have been investigated to determine the effect of using as a high loading filler with polypropylene. Characterisation of both materials showed each contained minerals suitable for polymer usage, with eggshell consisting of large amounts of calcium carbonate (common polymer filler). Both were added to polypropylene in loading up to 55% wt., and were successfully compounded into consistent polymer pellets, followed by injection moulding into test samples. Despite the use of a relatively large particle size, improvement in Young's modulus, flexural properties and impact strength were recorded. Samples however became more brittle with reductions in tensile strength and elongation. Characterisation showed both eggshell and PL(Ash) adhered with polypropylene, exhibiting full contact between particles and matrix, verifying potential as a polymer filler material and as a replacement to high amounts of oil-based polymer feedstock.

An Investigation into the Mechanical and Wear Characteristics of Hybrid Composites: Influence of Different Types and Content of Biodegradable Reinforcements

ABSTRACT This research work focuses on the wear characteristics of hybrid composites prepared using Sisal fiber (SF) /Pineapple fiber (PF) and Pineapple fly ash (PA) in various wt.%. Linear reciprocating tribometer was used for determining the Specific Wear Rate (SWR) and Coefficient of Friction (CoF) of the hybrid composites. The XRF results of PA filler showed the existence of silica (64.43%) and aluminum oxide (10.03%) in a major percentage. The hybrid fiber combination of 30-50 wt.% showed improvement in Tensile Strength (TS), Flexural Strength (FS) and Impact Strength (IS) with the filler mixing up to 5 wt.%. The Taguchi optimization (SN graph) observed the combination with PA addition of 5 wt.%, hybrid fiber addition of 30 wt.%, sliding distance and load of 1500 m, 10 N having lower SWR. Similarly for lower CoF, fly ash of 1 wt.%, fiber of 30 wt.%, sliding distance and load of 500 m and 5 N, respectively, with high SN ratio is the best combination. SEM results showed a decrease in filler content, higher load conditions, higher reinforcement causing more surface deformations in the composites.

Hybrid effects of carbon fiber and nanoclay as fillers on the performances of recycled wood-plastic composites

Waste wood-plastic composite (WPC) was used in this work as a raw material to produce recycled WPCs reinforced with carbon fiber and nanoclay. To evaluate the synergistic effects of carbon fiber and nanoclay, various performances (i.e., microstrucural, mechanical, thermal, water absorption, and electrical properties) were investigated. Scanning electron micrographs and X-ray diffraction analysis of the fillers (carbon fiber and nanoclay) present in the recycled WPCs showed that the nanoclays were properly intercalated when filled with carbon fibers. According to mechanical property analysis, hybrid incorporation of carbon fibers and nanoclays improved impact strength, tensile strength, and flexural strength. However, further incorporation of nanoclays reduced the impact strength and did not improve the tensile modulus or the flexural modulus. The carbon fibers present in the recycled WPCs improved the electrical conductivity of the composites, despite the various fillers that interfered with their electrical conduction. In addition, carbon fibers and nanoclays were mixed into the recycled WPCs to improve the thermal stability of the composites. Finally, the presence of nanoclays in recycled WPCs led to increased water uptake of the composites.

Detailed analysis on thermal, microstructural, mechanical, and morphological features of side chain liquid crystalline polymer/isotactic polypropylene graft copolymers: Effect of grafted and ungrafted polymer units

AbstractThe main scope of this comprehensive study is to investigate the effects of poly(p‐benzophenoneoxycarbonylphenyl acrylate), poly(BPOCPA), which presenting as only graft units or both graft and ungrafted units in the matrix, on the fundamental features of isotactic polypropylene (IPP). The graft copolymerization of BPOCPA onto IPP was performed with the aid of bulk melt polymerization at varying monomer content levels ranging from 5% to 40%. The thermal behavior, crystal quality, mechanical performance, and surface morphology of the samples were investigated by means of differential scanning calorimeter, X‐ray diffractometer (XRD), universal mechanical test, and scanning electron microscope (SEM) techniques. Thermal analyses depicted that there existed the noteworthy enhancements in both crystalline melting temperatures and percent crystallinities of matrix polymers. Furthermore, according to XRD results, a and b parameters increased significantly at low percentages of the graft units, while the parameter c decreased in all products in consistence with the content. As for the mechanical characterization, the grafting led to remarkable improvements in modulus, tensile and impact strength of the products. SEM micrographs indicated that the samples were completely homogeneous without any phase separation and the products exhibited brittle nature with some ductility.

Compression after Impact and Charpy Impact Characterizations of Glass Fiber/Epoxy/MWCNT Composites

In this study, glass fiber/epoxy resin/multi-walled carbon nanotubes (MWCNTs) were used to fabricate hybrid composites with biaxial warp-knitted fabrics. The biaxial warp-knitted fabrics were grafted with various amounts of MWCNTs and the hybrid composites were fabricated using the resin transfer molding (RTM) method, subsequently. The fabricated samples were subjected to compression after impact and Charpy impact tests. The hybrid composites exhibited higher compression after impact modulus and strength with 26 % and 17 % compared to the samples without nanotubes, respectively. Moreover, the MWCNTs integrated specimens showed 17 % improvement of Charpy impact strength against specimens without carbon nanotubes in 0 ° degree direction. Fracture surface analysis revealed lower number of cracks and shorter crack propagation lengths in the MWCNTs reinforced specimens. The improvement in mechanical properties of the hybrid composites can most likely be attributed to an increase in interfacial adhesion due to the presence of the carbon nanotubes.

Low-Velocity Impact Induced Damage Evaluation and Its Influence on the Residual Flexural Behavior of Glass/Epoxy Laminates Hybridized with Glass Fillers

This research work investigates the low-velocity impact induced damage behavior and its influence on the residual flexural response of glass/epoxy composites improved with milled glass fillers. The low-velocity impact damage employing varying impact velocities (3 m/s, 3.5 m/s, and 4 m/s) was induced on baseline and filler loaded samples with different fiber orientations. The residual performance and their damage modes were characterized using post impact flexural (FAI) test and acoustic emission (AE) monitoring. In all fiber orientations, the filler modified glass/epoxy samples showed improved impact strength and stiffness properties. A substantial improvement in impact damage tolerance, especially for samples impacted at 3.5 m/s and 4 m/s was observed. The presence of filler at the interlaminar zone contributed to improved energy dissipation through filler debonding and pull-out. This further contributed in arresting the crack growth, showing reduced damaged area. The inclusion of milled fibers on glass/epoxy laminates enhanced the impact toughness and residual flexural behavior.

Facile synthesis of Ag nanoparticles-loaded chitosan antibacterial nanocomposite and its application in polypropylene

The development of environmental-friendly antibacterial agents with high efficiency and low cost has become the focus of attention. In this work, the Ag nanoparticles doped into chitosan (Ag NPs-CS) were synthesized by a green and facile method, and the samples were characterized by UV–Vis spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and thermogravimetric analysis (TGA). The antibacterial tests implied that Ag NPs-CS obtained from glucose (G-Ag NPs-CS) exhibited the excellent antimicrobial activities against Gram-negative (Escherichia coli) and Gram-positive (Staphylococcus aureus) microbes. Besides, the utilization of antibacterial agents in polymeric materials plays an significant role in healthy living. The aim is to impart the antibacterial properties and maintain/improve the mechanical properties. Therefore, the G-Ag NPs-CS with 5 wt% Ag was chosen as the optimal additive to endow polypropylene with antimicrobial activity via a simple melt blending method. The results demonstrated that the suppression of bacteria proliferation was enhanced with increasing the amount of antibacterial agent, and the microorganisms were almost killed when the content reached to 8 wt%. Meanwhile, the considerable improvement in elastic modulus and impact strength along with a slight decrease of elongation at break provided the evidence that Ag NPs-CS/PP nanocomposites were the promising candidate for practical applications.

Cell structures, phase morphologies and impact toughness of phenolphthalein poly(ether ether ketone)/epoxy composite foams

AbstractThermoplastic phenolphthalein poly(ether ether ketone) (PEK‐C) /epoxy composite foams were prepared by free foaming process (Fre‐foams) and limited foaming process (Lim‐foams), respectively, and the effects of PEK‐C content and foaming methods on the cell structures, phase morphologies, and impact strength of epoxy foams were investigated. The results showed that the gas pressure in the bubbles promoted the resin curing process and polymerization‐induced phase separation process (PIPS) during the free foaming process, while the resin curing process and PIPS were highly constrained in Lim‐foams. The incorporation of PEK‐C in the Fre‐foams showed superior improvement in impact strength compared with the PEK‐C/epoxy Lim‐foams. By adding 12 wt% PEK‐C, the specific impact strength of Fre‐foams could be enhanced by 72%, and the improved specific impact strength was because the phase‐inverted structures could prevent crack initiation and propagation, and moreover the presence of PEK‐C led to significantly refine cell structure and reduce foam density. Interestingly, the impact strength of Lim‐foams was nearly independent on the PEK‐C content, it was attributed to the obviously increased cell size with increasing PEK‐C content, and also that the phase separation process was not carried out.

Effect of particulate fillers on natural rubber/high-density polyethylene blends for roofing application

Blending of two or more polymers generates a new material, which is more cost-effective than a newly synthesised material. Blending-type thermoplastic elastomer (TPE) is produced by melt-mixing of a thermoplastic with a rubber. These blends have high demands associated with excellent property combinations of the parent materials. Particulate fillers are used in the rubber and plastic industry for property modification and cost reduction. In this work, six particulate fillers, namely, calcium carbonate, barium sulphate (BaSO4), kaolin, talc, Snobrite clay and dolomite were used to develop natural rubber (NR)/high-density polyethylene (HDPE) TPE blends, and the most suitable filler for roofing application was identified. A series of NR/HDPE 20/80 blends were prepared by varying filler loading from 10 phr to 30 phr at 10 phr intervals using a Plasticorder. Mechanical properties, such as tensile strength, hardness, impact strength and tear strength, and gel content of the blends were investigated. The addition of talc, dolomite and kaolin to NR/HDPE blend showed reduced impact strength, which is the most important property for a roofing application. The other three fillers showed improved impact strength at specific loadings. The blend with 30 phr of BaSO4 was identified as the best blend, as per the overall performance.

Study of Mechanical and Moisture Absorption Behavior of Epoxy/Cloisite-15A Nanocomposites Processed Using Twin Screw Extruder

Abstract This paper presents the effect of process parameters of twin screw extruder and addition of Cloisite-15A on mechanical, thermal and moisture barrier properties of epoxy/Cloisite-15A nanocomposites. Four lobed kneading blocks were used the in shearing zone of the extruder, based on their effectiveness in dispersing nanofillers in epoxy. Screw speeds from 100 min−1 to 400 min−1, number of passes up to 15, temperature from 5°C to 80°C and Cloisite-15A contents from 1 wt.% to 2.5 wt.% were considered for designing the L12 Orthogonal Array. Improvements in tensile strength, compression strength, flexural strength, impact strength, hardness and moisture diffusivity in the nanocomposites were 11.89%, 20.06%, 27.73%, 37.26%, 25.48% and 56.22% respectively, when compared to neat epoxy. The improvements were achieved for screw speed of 400 min–1, 5 passes through the extruder, processing temperature of 5°C and 2 wt.% of Cloisite-15A. Dispersion of Cloisite-15A in epoxy was studied by XRD, SEM and TEM. Thermal stability and moisture barrier properties were superior in the nanocomposites.

Simultaneously enhanced impact strength and dielectric properties of an epoxy resin modified with EHTPB liquid rubber

AbstractTo simultaneously improve the impact strength and dielectric properties of cured epoxy (EP), herein we explore liquid rubber toughened EP based on a nonpolar epoxidized hydroxyl‐terminated polybutadiene (EHTPB), where the rubber is covalently bonded to the EP. Fourier transform infrared and nuclear magnetic resonance proved the chemical reaction between EHTPB and EP, which makes the immiscible EHTPB‐EP blend change to compatible one. The results indicate that both the impact strength and dielectric properties can be visibly enhanced with the addition of EHTPB and the maximum values are obtained at 10 phr of EHTPB loading. The improved mechanical toughness can be ascribed to the extensive shear yielding induced by the uniformly dispersed EHTPB domains and the enhanced interfacial compatibility between the two components. Moreover, the enhanced electrical resistivity and dielectric breakdown strength as well as the reduced dielectric constant and loss for the EHTPB‐EP can be attributed to the combination of the excellent insulating properties of HTPB and dielectrically favorable interfaces. Therefore, the EHTPB‐EP with a concurrent improvement in impact strength and dielectric properties can be used as promising insulating materials for high‐frequency microelectronics and high‐voltage electrical equipment.

Sustainable PHBV/Cellulose Acetate Blends: Effect of a Chain Extender and a Plasticizer

Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) and cellulose acetate (CA) were blended in the presence of a plasticizer, i.e., triethyl citrate (TEC), and a chain extender, i.e., poly(styrene-acrylic-co-glycidyl methacrylate). To increase the ductility and impact properties of PHBV and to investigate a new biodegradable PHBV-based blend for sustainable packaging, CA was compatibilized with TEC. PHBV and plasticized CA (pCA) blends showed complete immiscibility through separate glass transition and melting peak temperatures in differential scanning calorimetry (DSC), despite the similar Hansen solubility parameters of PHBV, CA, and TEC, indicating partial miscibility. Phase separation between PHBV and pCA was clearly observed by scanning electron microscopy (SEM). PHBV/pCA (70:30) blends had improved impact strength, exceeding that of neat PHBV and pCA, which is attributed to PHBV porosity induced by degradation from the high processing temperature. During processing, the plasticizer migrated from CA to PHBV and partially plasticized it, as evidenced through DSC analysis. The melt temperature of PHBV was reduced, which was confirmed by double melting peaks, representing the formation of secondary crystallites at a lower temperature. Due to processing at high temperatures (210–220 °C), significant porosity was observed in the PHBV/pCA 30:70 blend in SEM analysis. Consequently, the impact strength was improved by 110% as compared to that of virgin PHBV. The addition of CE had no effect on the mechanical properties but did make the PHBV/pCA blends morphologically uniform.

Epoxidation of Kraft Lignin as a Tool for Improving the Mechanical Properties of Epoxy Adhesive.

Owing to its chemical structure, wide availability and renewable nature, lignin is a promising candidate for the partial replacement of fossil-based raw material in the synthesis of epoxy resins. Its poor compatibility has been reported to be one of the main drawbacks in this domain. On the other hand, a well-established modification method for lignin epoxidation has been used for many years for the improvement of lignin compatibility. However, the extent of the effect of lignin epoxidation on the improvement of bio-based epoxy mechanical properties, applied as adhesives, is still an open question in the literature. In this context, a pristine and industrial grade kraft lignin (AKL) was reacted with epichlorohydrin to yield epoxidized lignin (E-AKL) in this work. Afterwards, AKL or E-AKL were separately blended with petroleum-based epoxy resin at 15 and 30 wt% and cured with a commercial amine. The adhesive curing kinetic was evaluated using a novel technique for thermal transition characterization, Temperature Modulated Optical Refractometry (TMOR); the results showed that the incorporation of AKL reduces the crosslinking rate, and that this effect is overcome by lignin modification. Mechanical tests revealed an improvement of impact and practical adhesion strength for samples containing 15 wt% of E-AKL. These results elucidate the effect of lignin epoxidation on the application of lignin-based epoxy adhesives, and might support the further development and application of these bio-based materials.

Development and characterization of polymer-based composites filled with micro-sized waste marble dust

This investigation explores the possibility of developing a new class of particulate-filled polyester composites using waste marble dust as filler. The dusts collected from local construction sites are sieved to three different sizes (58, 110, and 155 μm). Polyester composites are fabricated with filler in different weight proportions (0, 8, 16, 24, 32, and 40 wt%). A Fourier transform infrared spectroscopy study is done to get an insight into the chemistry of composite formation. Scanning electron microscopy reveals the surface features of the filler as well as the composites. X-Ray diffraction tests are carried out on the raw filler and on the composites to ascertain the presence of hard phases. The experimental findings suggest that, while the tensile and flexural strengths of the composites marginally drop with the incorporation of marble dust, there is reasonable improvement in compressive strength, impact strength, and Shore hardness. The density and voids are also affected by the size and content of filler particles in the composite. Armed with lightweight, improved hardness, and impact strength, these polyester–marble composites are expected to find potential use in wear-related engineering applications.