Khaled F. El-Nemr

The impact of graphene oxide (GO) nanoparticle content and exposure to electron beam (EB) on the tensile, dynamic mechanical, water uptake, and thermal properties of high‐density polyethylene/bagasse fibers composite was investigated. The GO was added at different loading levels: 0.25, 0.5, 0.75, and 1 parts per hundred parts of plastic (php), while 2 doses of EB were used (100 and 200 kGy). The influence of adding 10 php of carbon black (CB) to the HDPE/BF was also investigated. The addition of GO and irradiation up to 100 kGy, along with the inclusion of 10 php of CB, led to improvements in tensile strength, elastic modulus, storage modulus, and hardness. The composite containing 1 php of GO and exposed to 100 kGy, demonstrated the highest tensile strength value, with a 47.3% improvement compared with the unirradiated one. This composite also, exhibited the lowest values of water absorption percent (3.7%) and diffusion coefficient (0.007 mm ² /h) compared with the unirradiated HDPE/BF composite. These results suggest that the resulting composite has potential for use in advanced industrial applications due to its improved physicomechanical properties. Highlights: Composites based on high‐density polyethylene (HDPE) and bagasse fibers (BF) were fabricated The incorporation of graphene oxide (GO) improved the mechanical properties. GO and electron beam (EB) irradiation enhanced the water resistance of HDPE/BF composite. Both GO and EB increased the thermal stability of HDPE/BF composite.

Natural fiber-reinforced polymer composites offer many benefits over predictable composite materials, such as accessibility, low-cost, lightweight, and high definite mechanical properties. However, the applications of these materials are quiet restricted due to the contests in realizing a good interface between the fibers and matrix. This is highly influenced by the fiber surface characteristics and the polymer matrix properties. Therefore, this work discusses the incorporation of newsprint microcrystalline fibers (NPMCFs) in styrene-butadiene rubber (SBR) based composite. The fibers were first treated with (consistent concentration (10 w/100 w) coupling agents to fiber, respectively. The coupling agents namely: vinyl acetate versatic ester (VAcVe), maleic anhydride (MA), and phenol-formaldehyde resin (PFR), followed by surficial modification by irradiation with 30 kGy electron beam. Pristine and produced fibers were compounded to SBR. Mixing the ingredients was carried out on a rubber roll mill and then molded on a hot press to induce sulfur vulcanization. Characterization of the yielded fibers was investigated using Fourier Transform Infrared Spectrometry (FTIR). The mechanical properties of composites, such as tensile strength (TS), tensile modulus, tensile set, and crosslinking density demonstrated enhanced values as a result of enforcing the SBR matrix. The morphological examination via scanning electron microscopy (SEM) techniques explicitly indicated the adhesion of the prepared fibers to SBR moiety. Thermogravimetric analysis (TGA) confirmed a remarkable improvement in the thermal stability of the developed MA and PFR/SBR composites.

The present study focuses on utilizing polystyrene emulsion treated newsprint microcrystalline fibers (NPMCF). These treated fibers were then added to styrene‐butadiene rubber (SBR) at different concentrations, namely, 3, 6, 9, and 12 phr (part per hundred part of rubber). Mixing of ingredients was carried out on a rubber roll mill and afterward molded as a thin film on a hot press, then, exposed to electron beam irradiation doses up to 200 kGy so as to enhance the treatment of the composites. Mechanical properties of the composites, such as tensile strength, elongation at break, tensile modulus, and cross‐link density were enhanced by adding the treated fiber to SBR and by irradiation, and this enhancement was obtained at 6 phr fiber at 100 kGy. Measurements of scanning electron microscopy (SEM) proved the adhesion of the treated fibers to SBR. The thermal conductivity was measured for the prepared composites as a function of electron beam irradiation and fiber content. It was found that the thermal conductivity decreases according to fiber loading (up to 6 phr fiber) and irradiation dose.

The purpose of this research is to investigate the effect of gamma irradiation, concentration of microcrystalline newsprint fibers (MNF) and maleic anhydride as coupling agent for treating microcrystalline newsprint fibers (MA–MNF) on the mechanical and thermal properties of ethylene propylene diene monomer rubber matrix (EPDM). Maleic anhydride (MA) was used at a different ratios (5, 10, and 15 wt% according to the MNF). The EPDM/MA–MNF composites were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM) techniques. The results confirm the adhesion between MA–MNF and EPDM rubber matrix in presence of radiation. EPDM/MA–MNF composites have achieved higher mechanical properties than EPDM rubber matrix and EPDM/MNF composites. EPDM composites containing MNF that treated with 15% MA and gamma irradiated at 80 kGy have the highest tensile strength, tensile modulus at 100% strain, crosslink density and thermal stability over all other composites.

Virgin styrene‐butadiene rubber (SBR) was replaced by devulcanized waste tire rubber (DWR) 50/50 and used as a rubber base for preparing composites to depend on different silicate types at fixed content 40 phr (part per hundred part of rubber). All composites were mixed on a rubber roll mill and then subjected to electron beam irradiation to induce cross‐linking at a dose of 100 kGy. Different silicate fillers were used in this study such as precipitated silica (PS) 40 phr, waste glass window (WG) – PS 20/20 phr, fly ash (FA)‐PS 20/20 phr, and micaosilica (MS)‐PS 20/20 phr. Waste silicate was treated with (3‐aminopropyl) trimethoxysilane (APTMS) and blended with PS. Mechanical properties were measured for the composites like ultimate tensile strength, elongation at break, tensile modulus, and the cross‐link density was calculated from the mechanical study. As well as, application for floor tiles included compression set and abrasion resistance measurements. All results indicated an enhancement in ultimate tensile strength, modulus, and cross‐link density by adding silicate fillers and more enhanced in the electron beam irradiated samples. For the application of floor tiles, the MS filler gave a good compression set and abrasion resistance followed by other silicate fillers (PS, FA), except WG.

In this study, new composites were prepared from ethylene propylene diene rubber (EPDM) that loaded with various concentrations of short carbon fibers (SCFs) ranged from 5 up to 20 part per hundred part of rubber (phr). Aluminum trihydroxide (ATH) was added by two concentrations, namely 10 and 30 phr to EPDM/SCFs composites to enhance its heat shielding. Foaming agent, azodicarbonamide (ADC) was added to increase ablation resistance. Composites were prepared on open rubber roll mills, and then the rubber composites were gamma ray irradiated at different doses of 25, 50, 75, 100 and 150 kGy. Fiber incorporation into rubber matrix has been proven as a key factor in enhancing tensile strength and flame retardant properties of fabricated composites. The prepared composites were characterized by using various analytical methods counting physico-mechanical properties, thermal gravimetric analysis (TGA), Ablation test (oxy acetylene test) and propagation flame test. The utmost mechanical performance was reported for the incorporated 5 phr of carbon fiber into EPDM at 100 kGy. Also, the flame retardancy and ablation properties for composites were enhanced by increasing addition of carbon fibers and ATH in of ADC.

The engagement of waste tires rubber as source of raw materials for different applications can be a partial solution to the great environmental problems caused by these products. In this study, waste tire rubber was devulcanized using both mechano–chemical and microwave methods. This process was achieved using different concentrations of 2-mercapto benzothiazole disulfide (MBTS) and tetramethylthiuram disulfide (TMTD) as a devulcanizing agent and different microwave devulcanizing times. The optimum content of both MBTS, TMTD and suitable microwave treatment time to make continuous film were noted. The devulcanized waste rubber was then added, at different concentrations, to virgin styrene–butadiene rubber (SBR). The thermal properties and dynamic mechanical behaviors were investigated for all blends. The thermal analysis proved that natural and styrene butadiene rubber are the main two constituents of the waste tire rubber utilized in this study. The mechanical behavior of the SBR blends remarkably improved by using 20 phr waste rubber (WR) devulcanized by 2 phr MBTS and by exposure for 2.2 min to microwaves. Storage modulus, tearing strength and tension set behaviors notably improved for all SBR/WR blends by irradiating with gamma ionizing radiation with a dose of 100 kGy and further improvement could be attained by increasing the dose up to 200 kGy.

Waste tire rubber was comparatively devulcanized by using two-roll mill mechano-chemical and microwave techniques at room temperature. The former technique was performed utilizing tetramethylthiuram disulfide and mercaptobenzothiazole disulfide. The developed devulcanized elastomer was characterized by scanning electron microscopy, chemical soluble fraction indication, and cross-link density determination. The blend was mixed in two roll mills by replacing a portion of virgin styrene-butadiene rubber (SBR) in a common formulation with the devulcanized waste rubber (DWR) product at various ratios, namely 10, 20 and 50 wt%. The morphological micrographs confirmed marked improvement in compatibility between both rubbery materials. The tensile strength and elastic modulus examinations of the fabricated blends ensured successful substitution of the virgin SBR with DWR. The abrasion resistance of SBR proved unaffected by blending with DWR. The compounded blends were subjected to γ rays at different radiation doses elevated up to 200 kGy and comparatively mechanically investigated.

Composites of acrylonitrile butadiene rubber loaded by different concentration (0–40 parts by weight per hundred parts of rubber (phr)) of waste rubber ash (WRA) that treated by Vinyltriethoxysilane (VTES) have been prepared, and then the composites subjected to gamma radiation at different doses ranged (0 up to 150 kGy) to desire curing. The WRA powder that treated by VTES silane (WRA-Sn) was characterised by different tools like Fourier transforms infrared spectroscopy and X-ray diffraction. Mechanical properties of composites tensile, elongation and modulus were shown enhancement by increasing the treatment of waste rubber and also by increasing irradiation dose. The crosslink density of composites increases by increasing WRA-Sn content and irradiation dose. The thermal stability of a variety of composites was done using thermogravimetric analysis. The results show that the WRA-Sn improves its thermal stability of composites.