Study of Thermal Effect on the Mechanical Properties of Nylon 610 Nanocomposites with Graphite Flakes That Have Undergone Supercritical Water Treatment at Different Temperatures

This study investigates the thermal effect of supercritical water treatment at different temperatures (150, 175, 200 °C) and semi-vacuum state (-0.08 MPa) on graphite flakes which are then incorporated into nylon 610. The treatment is deemed to increase the surface activity of nanofillers through the formation of oxygen-containing functional groups. X-ray diffraction (XRD) analysis indicated that the crystal structure of the flakes remained similar before and after supercritical water treatment. Fourier transform infrared spectroscopy (FTIR) also showed the presence of hydrogen bonding between the flakes and the polymer matrix through the appearance of amide bands. The intensity of the amide peaks is higher for nanocomposites with treated flakes than untreated ones. Furthermore, scanning electron microscopy (SEM) showed that at higher wt%, aggregation will occur, which leads to a weakening in physical properties. The tensile strength of nanocomposites with treated flakes decreased with increasing wt%, while those with untreated flakes increased with increasing wt%. Young's modulus of all the nanocomposites generally increased with increasing wt%. The highest tensile strength obtained is 967.02 kPa, while that of neat nylon 610 is 492.09 kPa. This enhancement in mechanical properties can be attributed to the intact structure of the graphite flakes and the interaction between the flakes and the nylon 610 matrix. A higher temperature of water treatment was discovered to cause higher oxidation levels on surface of the nanofillers but would result in some structural damage. The optimum nylon 610 nanocomposite synthesized was the one that was incorporated with 1.5 wt% graphite flakes treated at 150 °C and -0.08 MPa, as it has the highest tensile strength.

Superior Interaction of Electron Beam Irradiation with Carbon Nanotubes Added Polyvinyl Alcohol Composite System

This work was conducted to investigate the effect of carbon nanotube (CNT) on the mechanical-physico properties of the electron beam irradiated polyvinyl alcohol (PVOH) blends. The increasing of CNT amount up to 1.5 part per hundred resin (phr) has gradually improved tensile strength and Young’s modulus of PVOH/CNT nanocomposites due to effective interlocking effect of CNT particles in PVOH matrix, as evident in SEM observation. However, further increments of CNT, amounting up to 2 phr, has significantly decreased the tensile strength and Young’s modulus of PVOH/CNT nanocomposits due to the CNT agglomeration at higher loading level. Irradiation was found to effectively improve the tensile strength of PVOH/CNT nanocomposites by inducing the interfacial adhesion effect between CNT particles and PVOH matrix. This was further verified by the decrement values of d-spacing of the deflection peak. The increasing of CNT amounts from 0.5 phr to 1 phr has marginally induced the wavenumber of O–H stretching, which indicates the weakening of hydrogen bonding in PVOH matrix. However, further increase in CNT amounts up to 2 phr was observed to reduce the wavenumber of O–H stretching due to poor interaction effect between CNT and PVOH matrix. Electron beam irradiation was found to induce the melting temperature of all PVOH/CNT nanocomposite by inducing the crosslinked networks.

A Review on the Synthesis, Properties, and Utilities of Functionalized Carbon Nanoparticles for Polymer Nanocomposites

Carbon can form different allotropes due to its tetravalency. Different forms of carbon such as carbon nanotubes (CNTs), carbon nanofibers, graphene, fullerenes, and carbon black can be used as nanofillers in order to enhance the properties of polymer nanocomposites. These carbon nanomaterials are of interest in nanocomposites research and other applications due to their excellent properties, such as high Young’s Modulus, tensile strength, electrical conductivity, and specific surface area. However, there are some flaws that can be found in the carbon nanoparticles such as tendency to agglomerate, insoluble in aqueous or organic solvents or being unreactive with the polymer surface. In this study, the aim is to study functionalization in order to rectify some of these shortcomings by attaching different functional groups or particles to the surface of these carbon nanoparticles; this also enables the synthesis of high-performance polymer nanocomposites. The main findings include the effects of functionalization on carbon nanoparticles and the applications of polymer nanocomposites with carbon nanoparticles as nanofillers in the industry. Additionally, the different methods used to produce polymer composites such as in situ polymerization, solution mixing and melt blending are studied, as these methods involve the dispersion of carbon nanofillers within the polymer matrix.

Viscoelastic Properties and Thermal Stability of Nanohydroxyapatite Reinforced Poly-Lactic Acid for Load Bearing Applications

We studied the reinforcing effects of treated and untreated nanohydroxyapatite (NHA) on poly-lactic acid (PLA). The NHA surface was treated with three different types of chemicals; 3-aminopropyl triethoxysilane (APTES), sodium n-dodecyl sulfate (SDS) and polyethylenimine (PEI). The nanocomposite samples were prepared using melt mixing techniques by blending 5 wt% untreated NHA and 5 wt% surface-treated NHA (mNHA). Based on the FESEM images, the interfacial adhesion between the mNHA filler and PLA matrix was improved upon surface treatment in the order of mNHA (APTES) > mNHA (SDS) > mNHA (PEI). As a result, the PLA-5wt%mNHA (APTES) nanocomposite showed increased viscoelastic properties such as storage modulus, damping parameter, and creep permanent deformation compared to pure PLA. Similarly, PLA-5wt%mNHA (APTES) thermal properties improved, attaining higher Tc and Tm than pure PLA, reflecting the enhanced nucleating effect of the mNHA (APTES) filler.

Thermochemical compatibilization of reclaimed tire rubber/ poly(ethylene-co-vinyl acetate) blend using electron beam irradiation and amine-based chemical

Waste tire rubber is commonly recycled by blending with other polymers. However, the mechanical properties of these blends were poor due to lack of adhesion between the matrix and the waste tire rubber. In this research, the use of electron beam irradiation and (3-Aminopropyl)triethoxy silane (APTES) on enhancing the performance of 50 wt% reclaimed tire rubber (RTR) blend with 50 wt% poly(ethylene-co-vinyl acetate) (EVA) was investigated. Preparation of RTR/EVA blends were carried out in the internal mixer. The blends were then exposed to electron beam (EB) irradiation at doses ranging from 50 to 200 kGy. APTES loading was varied between 1 to 10 wt%. The processing, morphological, mechanical, and calorimetric properties of the blends were investigated. The stabilization torque and total mixing energy was higher in compatibilized blends. Mechanical properties of RTR/EVA blends were improved due to efficiency of APTES in further reclaiming the RTR and compatibilizing the blends. APTES improved the dispersion of embedded smaller RTR particles in EVA matrix and crosslinking efficiency of the blends. Calorimetric studies showed increased crystallinity in compatibilized blends which corresponds to improved mechanical properties. However, the ductility of the blend was decreased due to increased interaction between EVA and APTES. Presence of APTES increased the efficiency of electron beam irradiation induced crosslinking which was shown through gel content analysis and Charlesby-Pinner equation.

Gamma-Irradiation Induced Functionalization of Graphene Oxide with Organosilanes

Gamma-ray radiation was used as a clean and easy method for turning the physicochemical properties of graphene oxide (GO) in this study. Silane functionalized-GO were synthesized by chemically grafting 3-aminopropyltriethoxysilane (APTES) and 3-glycidyloxypropyltrimethoxysilane (GPTES) onto GO surface using gamma-ray irradiation. This established non-contact process is used to create a reductive medium which is deemed simpler, purer and less harmful compared conventional chemical reduction. The resulting functionalized-GO were characterized by Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), thermogravimetric analysis (TGA), and Raman spectroscopy. The chemical interaction of silane with the GO surface was confirmed by FT-IR. X-ray diffraction reveals the change in the crystalline phases was due to surface functionalization. Surface defects of the GO due to the introduction of silane mioties was revealed by Raman spectroscopy. Thermogravimetric analysis of the functionalized-GO exhibits a multiple peaks in the temperature range of 200–650 °C which corresponds to the degradation of chemically grafted silane on the GO surface.

E-beam sterilizable thermoplastics elastomers for healthcare devices: Mechanical, morphology, and in vivo studies

The effect of electron beam radiation on ethylene-propylene diene terpolymer/polypropylene blends is studied as an attempt to develop radiation sterilizable polypropylene/ethylene-propylene diene terpolymer blends suitable for medical devices. The polypropylene/ethylene-propylene diene terpolymer blends with mixing ratios of 80/20, 50/50, 20/80 were prepared in an internal mixer at 165°C and a rotor speed of 50 rpm/min followed by compression molding. The blends and the individual components were radiated using 3.0 MeV electron beam accelerator at doses ranging from 0 to 100 kGy in air and room temperature. All the samples were tested for tensile strength, elongation at break, hardness, impact strength, and morphological properties. After exposing to 25 and 100 kGy radiation doses, 50% PP blend was selected for in vivo studies. Results revealed that radiation-induced crosslinking is dominating in EPDM dominant blends, while radiation-induced degradation is prevailing in PP dominant blends. The 20% PP blend was found to be most compatible for 20-60 kGy radiation sterilization. The retention in impact strength with enhanced tensile strength of 20% PP blend at 20-60 kGy believed to be associated with increased compatibility between PP and EPDM along with the radiation-induced crosslinking. The scanning electron micrographs of the fracture surfaces of the PP/EPDM blends showed evidences consistent with the above contentation. The in vivo studies provide an instinct that the radiated blends are safe to be used for healthcare devices.

INFLUENCE OF SONICATION ASSISTED DISPERSION METHOD ON THE MECHANICAL AND ELECTRICAL PROPERTIES OF NYLON 66/NANO-COPPER NANOCOMPOSITE

Nylon 66 is a well known engineering polymer with excellent mechanical and thermal properties. However, its poor electrical conductivity restricts its application for conductive material. In this study, nano-copper particles are added into nylon 66 polymer matrix to enhance the electrical conductivity value of the nanocomposite. Sonication assisted dispersion method was used to achieve well dispersed nanomaterials through reasonable exfoliation of the nano-copper particles in the nylon 66 polymer. The impact of sonication on the mechanical performance and the electrical conductivity of nanocomposite were evaluated. The sonication was found to effectively reduce agglomeration of nano-coppers in nylon 66, and improved both mechanical performance and electrical conductivity of the nanocomposite. Irrespective of the nano-copper amount, nanocomposite with sonication-treated nano-copper consistently showed higher hardness and impact strength than nanocomposite without sonication. The electrical conductivity increased by two orders of magnitude from 10-15 to 10-13 for the nanocomposite added with sonication-treated nano-copper compared to that without sonication treatment.

Enhancements in crystallinity, thermal stability, tensile modulus and strength of sisal fibres and their PP composites induced by the synergistic effects of alkali and high intensity ultrasound (HIU) treatments

In this investigation, sisal fibres were treated with the combination of alkali and high intensity ultrasound (HIU) and their effects on the morphology, thermal properties of fibres and mechanical properties of their reinforced PP composites were studied. FTIR and FE-SEM results confirmed the removal of amorphous materials such as hemicellulose, lignin and other waxy materials after the combined treatments of alkali and ultrasound. X-ray diffraction analysis revealed an increase in the crystallinity of sisal fibres with an increase in the concentration of alkali. Thermogravimetric results revealed that the thermal stability of sisal fibres obtained with the combination of both alkali and ultrasound treatment was increased by 38.5°C as compared to the untreated fibres. Morphology of sisal fibre reinforced composites showed good interfacial interaction between fibres and matrix after the combined treatment. Tensile properties were increased for the combined treated sisal fibres reinforced PP composites as compared to the untreated and pure PP. Tensile modulus and strength increased by more than 50% and 10% respectively as compared to the untreated sisal fibre reinforced composite. It has been found that the combined treatment of alkali and ultrasound is effective and useful to remove the amorphous materials and hence to improve the mechanical and thermal properties.

Facile Surface Modification of Graphene Nanoplatelets (GNPs) Using Covalent ATPS-Dehydration (GNPs-ATPS) and Non-Covalent Polyetherimide Adsorption (GNPs-PEI) Method

Graphene nanoplatelets (GNPs), a newly discovered nanomaterial, promise a great potential in many technological applications. However, the direct usage of GNPs was limited due to several surface property factors that require innovative modifications and treatments. In this study, the GNPs surface treatment is carried out by using a covalent and non-covalent approach. The success of the treatment was determined and evaluated through the Raman and FTIR spectroscopy analysis, FESEM, TEM and XRD morphological observation. A strong vibration of Raman peak at 2081.11 cm-1 represent a possible covalent bonding of C=C due to the ATPS-silane treatment, while the characteristic peak at 1013.82 cm-1 indicates the aromatic ring nature of polyimide that non-covalently associated with C-H and C-C, as well as C-O-C linkage from the polyether. From the IR spectroscopy, the covalent treatment on GNPs was occurred through the dehydration mechanism while hydrogen bonding in the multiple structures of –OH that associated to the carboxylic acids was obviously involved for non-covalent treatment of GNPs. TEM observation of GNPs-PEI (polyetherimide) revealed a unique phenomenon of a polymeric adsorption as represented by a nanosize gray dot morphology in between of the GNPs platelets. In overall, the facile procedure of the surface treatment that was applied in this study is reliable to yield a different type of GNPs characteristic of covalent and non-covalent surface active, which may open up broad possibilities for various cutting edges applications.

Non-Covalent Polymeric Wrapping of IGEPAL C0890 for Graphene Nanoplatelets (GNPs-C0890) Filled NR/EPDM Rubber Blend Nanocomposites

Graphene nanoplatelets (GNPs) surface modification was performed by using a simplified dual-action of ultrasonication and high speed mechanical shearing. This approach induced a non-covalent polymeric wrapping interaction between GNPs surfaces with IGEPAL-C0890 (ethoxylated nonyl phenol with 40 moles ethylene oxide). Various characterization tools like FTIR, Raman spectroscopy, FESEM and TEM were utilized to confirm the success of the surface treatment. The efficacy and suitability of non-covalent treated GNPs-C0890 as nanofiller reinforcement and inorganic compatibilizer in NR/EPDM rubber blends were evaluated. Effects of GNPs-C0890 loading variation to the mechanical tensile properties and fracture morphologies of NR/EPDM nanocomposites rubber blend were studied. It is interesting to note that the GNPs-C0890 was not able to reinforce NR/EPDM blend at a higher loading addition (≥ 3.00 wt.%) due to the agglomeration and crosslinking retardation phenomena by phase separation. However, at a lower loading (≤ 1.00 wt.%), the blend strengthening effects promise the improvement at about 64.55% of tensile strength and 14.20% of elongation percentage as compared than unfilled NR/EPDM blend. Obvious fractured morphological changes due to the absence and presence of GNPs provide hints on the role of GNPs treatment in effecting the NR/EPDM rubber blend mechanical properties.

Effects of calcium stearate and metal hydroxide additions on the irradiated LDPE/EVA compound properties

The effects of the addition different fillers, such as calcium stearate (CS), aluminum trihydrate (ATH), and magnesium hydroxide (MH), on the properties of low-density polyethylene/ethylene vinyl acetate (LDPE/EVA) compounds were studied. It was determined that the adhesion forces among MH and LDPE/EVA compounds were stronger than those among analogue compounds containing ATH in each irradiated sample. The gel content (GC) values of irradiated compounds containing ATH were higher than those of the analogue MH compounds, and CS addition enhanced the GC values of all compounds in each irradiated sample. The density values of compounds with MH content were higher than those of analogue compounds containing ATH in each irradiated sample. It was shown that all pristine compounds whose density was compared with irradiated samples had maximum values. Addition of CS and enhancing irradiation to polymer compounds reduced the density values. Compounds with high CS contents and were highly irradiated showed high tensile strength (TS) values. The TS values of compounds containing ATH were lower than those of analogue compounds containing MH in each irradiated sample. ATH or MH addition to polymer matrices reduced the elongation at break (EB) values in each irradiated sample. The EB values of compounds containing ATH were higher than those of compounds containing MH in each irradiation range. CS addition improved polymer chain flexibility and enhanced the compounds’ EB values with irradiation.

Electron-beam irradiation of low density polyethylene/ethylene vinyl acetate blends

In this work, the properties of electron-beam irradiated low density polyethylene (LDPE), ethylene vinyl acetate (EVA) and blends were investigated. EVA addition had an enhancement effect on crosslinking of irradiated LDPE/EVA blends. The measured gel content increase of the blends and the improvement of thermal elongation, tensile strength, elongation at break, thermal aging and heat deformation, have confirmed the positive effects of electron-beam irradiation on the blend properties. The crystallinity of the blends decreased with irradiation. The gel content and hot set tests showed that the degree of crosslinking in the amorphous regions was dependent on the dose and blend composition. Increasing the EVA content resulted in tighter network structures. A significant improvement in the tensile strength of the neat EVA samples was obtained upon electron-beam irradiation up to 210 kGy. The irradiated LDPE/EVA blends showed improved tensile strength and elongation at break, when compared to LDPE. The enhanced irradiation crosslinking of the LDPE/EVA blends was proportional to the good compatibility and the increasing degree of the amorphous region’s content of the LDPE/EVA blends. The possible degradation mechanism of LDPE/EVA blends was discussed quantitatively with a novel method step analysis process of irradiated LDPE/EVA blends in the thermal gravimetric analysis (TGA) technique. It was found, with measuring thermal conductivity (k) and specific heat capacity (Cp) of the blends, that the k values of the LDPE samples at a prescribed temperature range decreased with increasing irradiation. An increase in the crystallinity led to an increase in the k values and a decrease in the Cp values of the LDPE samples. Irradiation below 150 kGy decreased the Cp (at 40°C) and k in average values, whereas increasing the EVA made enhanced the Cp and k values of LDPE/EVA blends at each irradiation. The surface resistance and volume resistivity (VR) of the blends reached a maximum at a 170 kGy irradiation and 30 wt% of EVA. Increasing the amount of EVA contents resulted in enhancement of the dielectric loss factor for the irradiated blends.