Electrical and thermal properties of γ‐irradiated nitrile rubber/rice husk ash composites

The effects of both the rice husk ash (RHA) loading and fumed silica (FS) loading on the structure, thermal stability, and electrical properties of acrylonitrile–butadiene rubber (NBR) composites were studied. The filler loading were chosen to be 5 and 20 phr for RHA and 5 and 30 phr for silica. Also, the effect of the γ‐irradiation dose (25 kGy) on these parameters was investigated. The structure and thermal stability were studied with X‐ray diffraction and thermogravimetric analysis techniques. Furthermore, some electrical parameters, such as the direct‐current electrical conductivity (σ_dc), activation energy (E_a), dielectric constant (?′), and dielectric loss (?″), were determined. The incorporation of both RHA and FS resulted in improved thermal stability after γ irradiation at 25 kGy. The loading of FS on NBR was shown to decrease σ_dc, ?′, and ?″ and increase E_a. On the other hand, the loading of RHA showed the opposite trend. Finally, γ irradiation of NBR composites filled with both fillers decreased the values of σ_dc, ?′, and ?″ for all the samples, which followed the trend for the unirradiated composites. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Effect of gamma‐irradiation on the mechanical behavior of EPDM rubber‐recycled newsprint microfibers composites

Waste newsprint paper was collected from the local market and subjected to chemical pulping using 2 M NaOH. The fiber, after getting rid of water, was treated again using 2 M HCl solution for the same time period. The obtained newsprint microfibers (NPFs) were characterized by using scanning electron microscopy (SEM), X‐ray diffraction (XRD), and Fourier transform infrared spectra. Then the dried and grounded NPF batch was mixed with ethylene propylene diene monomer (EPDM) rubber using different concentrations ranged from 5 to 50 phr. The prepared composites were irradiated by using gamma rays at different doses from 20 to 100 kGy. The mechanical properties of prepared EPDM/NPFs composites such as tensile strength (Ts), elongation at break (E_b%), tensile modulus (M₁₀₀), toughness (T_t), and crosslink density (Cd) were measured as a function of fiber contents and irradiation dose. The results indicated that the tensile strength (Ts) increases with increasing microfibers contents up to 10 phr and irradiation dose up to 40 kGy, while E_b% decreases as the fibers content and irradiation dose increase. M₁₀₀ and Cd values increase with increasing fibers content up 50 phr fibers and irradiation dose up to 60 kGy. The results also concluded that the toughness values of EPDM/NPFs composites reach its maximum degree when using 10 phr NPFs concentration and 60 kGy irradiation dose. J. VINYL ADDIT. TECHNOL., 25:198–212, 2019. © 2018 Society of Plastics Engineers     

Electron beam irradiation of polycarbonate reinforced acrylonitrile butadiene rubber

The effects of electron beam irradiation and polycarbonate (PC) concentration on the properties of acrylonitrile butadiene rubber (NBR) were investigated. The electron beam irradiation doses were from 25 to 150 kGy, whereas the PC contents were from 10 to 30 phr. It was found that the mechanical properties of NBR such as tensile strength (TS), hardness and tear strength (Ts) were remarkably improved by the incorporation of PC, while elongation at break (E_b) and thermal properties were decreased. However, the improvement in TS of NBR/PC blends was strongly dependant on PC content, in which maximum improvements need higher doses. On the other hand, the maximum value of Ts for all the blend ratios was at 25 kGy, whereas the hardness increases with increasing irradiation dose. Moreover, it was observed that the fuel resistance of NBR/PC was higher than NBR and decreases by increasing the content of PC.     

Mechanical and physicochemical properties of electron beam irradiated rubber/clay nanocomposites

Effect of electron beam irradiation on the mechanical and physicochemical properties of both styrene butadiene rubber (SBR)/clay and ethylene propylene diene monomer (EPDM)/clay nanocomposites containing clay contents from 3 to 10 phr prepared by melt blending method has been investigated. The prepared composites were subjected to electron beam irradiation doses of up to 150 kGy to induce radiation curing, whereas the mechanical properties in terms of tensile strength (TS), tear strength (Ts), and elongation at break (E_b) were studied as a function of irradiation dose and clay content. TS and Ts increased with increasing irradiation dose up to 100 kGy, they were decreased with further increase in dose. An increase in TS and Ts for SBR and EPDM nanocomposites containing various organomodified montmorillonite (OMMT) contents (3–5 phr) was noticed, whereas a decrement behavior was observed at higher OMMT content. The elongation at break decreased continuously with both irradiation dose and OMMT content. The crosslink density for either EPDM or SBR samples increases with increasing irradiation dose up to 150 kGy and by increasing clay content up to 5 phr, whereas it decreases at higher clay content (7–10 phr). At 5 phr OMMT and 100 kGy irradiation, SBR nanocomposites showed higher TS and Ts than EPDM nanocomposites, while the crosslink density of SBR is lower. POLYM. COMPOS., 34:1600–1610, 2013. © 2013 Society of Plastics Engineers     

Mechanical,thermal, and transport properties of nitrile rubber–nanocalcium carbonate composites

The article describes the properties of acrylonitrile butadiene copolymer (NBR)–nanocalcium carbonate (NCC) nanocomposites prepared by a two‐step method. The amount of NCC was varied from 2 phr to 10 phr. Cure characteristics, mechanical properties, dynamic mechanical properties, thermal behavior, and transport properties of NBR–NCC composites were evaluated. For preparing NBR nanocomposites, a master batch of NBR and NCC was initially made using internal mixer. Neat NBR and the NBR–NCC masterbatch was compounded with other compounding ingredients on a two roll mill. NCC activated cure reaction upto 5 phr. The tensile strength increased with the nanofiller content, whereas NBR–NCC containing 7.5 phr exhibited the highest modulus. The storage modulus (E′) increased up to 5 phr NCC loading; the reinforcing effect of NCC was seen in the increase of modulus which was more significant at temperatures above T_g. The effect of nanofiller content and temperature on transport properties was evaluated. The solvent uptake decreased with NCC content. The mechanism of diffusion of solvent through the nanocomposites was found to be Fickian. Transport parameters like diffusion, sorption, and permeation constants were determined and found to decrease with nanofiller content, the minimum value being at 7.5 phr. Thermodynamic constants such as enthalpy and activation energy were also evaluated. The dependence of various properties on NCC was supported by morphological analysis using transmission electron microscopy. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Effect of electron beam irradiation and degree of boric acid loading on the properties of styrene-butadiene rubber

Synthetic and totally amorphous styrene-butadiene rubber (SBR) has been loaded with varying contents of boric acid. Vulcanization of prepared composites as well as of unloaded rubber has been induced by ionizing radiation of accelerated electron beam of varying doses up to 250 kGy. Evaluation of prepared composite subjected to this range of irradiation has been followed up through the measurement of mechanical, physical, electrical and thermal properties of vulcanized composites. Mechanical properties, namely tensile strength (TS) and Young’s modulus were found to increase, whereas elongation at break (E_b) and permanent set (PS) were found to decrease with the increase in degree of boric acid loading as well as irradiation dose. On the other hand, physical properties, namely the gel content, have increased whereas the swelling number has decreased. Moreover, increase in the decomposition temperature has been attained. Also, limited increase in electrical conductivity has taken place. Data obtained indicate enhancement in thermal as well as in physico-mechanical properties of prepared composites. Moreover, 60 phr of boric acid has attained good mechanical properties.     

Impact of graphene oxide nanoparticles and carbon black on the gamma radiation sensitization of acrylonitrile–butadiene rubber seal materials

Seals prepared from acrylonitrile–butadiene rubber (NBR) are primarily used in nuclear services. Nevertheless, at relatively high ionizing radiation doses, NBR seal materials may undergo radiation-induced degradation processes, leading to adverse effects on the sealing ability life. Herein, to strengthen the functional characteristics of NBR seals against radiation, graphene oxide (GO) nanoparticles were prepared and characterized by transmission electron microscopy, X-ray diffraction (XRD), Fourier transform infrared (FTIR), and ultraviolet/visible spectroscopies. Various NBR/GO composites fabricated with different ratios of GO nanoparticles and in the presence or absence of carbon black (CB) were investigated via cross-linking density, scanning electron microscopy, XRD, FTIR, and mechanical and thermal stability analyses. The synergistic effect of the simultaneous presence of GO and CB on the NBR seal sensitization to gamma radiation up to a dose of 1 MGy was studied. The physicomechanical properties were enhanced by adding GO nanosheets up to 3 phr and by incorporating 35 phr of a CB with GO until 5 phr. Further, the application of γ-irradiation resulted in an overall enhancement in the mechanical, physical, and thermal stability of the prepared composites up to 0.5 and 1 MGy with GO nanosheets in the absence or presence of CB particles, respectively. The mechanical measurements indicated significant increments by loading with GO nanosheets in the absence and presence of CB as well as by irradiation. The tensile strength elevated up to about 121%, 336%, and 366% by adding 3 phr GO, 3 GO:35 CB phr, and 5 GO:35 CB phr, respectively.     

EFFECT OF FIBER REINFORCEMENT ON THERMAL STABILITY AND SWELLING BEHAVIOR OF CR/NBR BLENDS

The effect of type, length, and denier of fibers on the thermal stability and swelling behavior of chloroprene/butadiene–acrylonitrile rubbers (CR/NBR) composites was investigated. The results reveal that Nylon 6 fibers improved mechanical properties, thermal stability, and swelling resistance in toluene of 50/50 CR/NBR blends. Of all fiber types investigated, the viscose fiber CR/NBR composite has the best swelling resistance in motor oil, whereas the polyester (PET) fiber composite has the best swelling resistance in brake fluid. The effect of Nylon 6 fiber loading up to 30 phr was tested in terms of mechanical properties of the composites and swelling in toluene and oils. Also, the reinforcement of white-filled blends were examined. Nylon 6 fiber loadings (15–30 phr) showed promising results, and the white-filled Nylon 6 composites showed a significant reinforcement with regard to mechanical properties and thermal stability.     

Irradiation Modification of PVC/NBR Blend

Electron beam initiated cross-linking on the 50/50 poly(vinyl chloride), PVC/acrylonitrile butadiene rubber, NBR blend was studied in the absence and presence of 4 phr trimethylolpropane triacrylate (TMPTA). The 50/50 NBR/PVC blend was prepared by mixing in a Brabender Plasticoder at 170°C. The blend was then irradiated by using a 3.0 MeV electron beam machine at doses ranging from 0 to 200 kGy in air and room temperature. The changes in gel fraction, tensile strength, hardness, impact strength, scanning electron micrographs and dynamic mechanical properties of the samples were investigated. The gel fraction results indicate that under the irradiation conditions employed, the PVC/NBR blend cross-linked by electron beam irradiation. The addition of TMPTA was found to be effective in the acceleration of the radiation-induced cross-linking. Gradual increases in mechanical properties with irradiation dose were observed before exhibiting a decline due to embrittlement as a consequence of excessive cross-linking at higher irradiation doses. The gradual changeover from ductile to brittle fracture due to the irradiation-induced cross-linking was evident from the SEM examination The increase in the storage modulus and T_g as well as the reduction in the damping peak with the increase in irradiation dose reveal that the enhancement in mechanical properties of NBR/PVC blends upon irradiation is due to the irradiation-induced cross-linking, as well as the improved interaction between NBR and PVC.     

Thermal behavior of gamma‐irradiated amorphous poly (ethylene terephthalate) films

Poly (ethylene terephthalate) (PET) was irradiated in air by gamma rays at dose rate of 28 kGy/h for doses up to 3500 kGy. The influences of gamma irradiation on the glass transition and degree of crystallinity were investigated by differential scanning calorimetry. For amorphous PET, the observed glass transition temperature T_g and step of heat capacity ΔC_p decreased with absorbed dose. These decreases were attributed to a predominant chain scission process. The glass transition temperature may be useful as an indicator of radiation to the PET. The results also showed that such chain scission increases in mobility lead to a greater crystallizability. POLYM. ENG. SCI. 46:1374–1377, 2006. © 2006 Society of Plastics Engineers     

The effect of gamma irradiation on mechanical,thermal and morphological properties of glass fiber reinforced polyethylene waste/reclaim rubber composites

Composites of waste polyethylene (WPE), collected from municipal solid waste/recycled waste rubber powder (RWRP) reactive compatibilizing agent, maleic anhydride (MA) and glass fiber (GF) up to 20 wt%, prepared by melting and irradiated with gamma-rays up to 150 kGy have been studied. Tensile strength (T_S), elongation at break (E_b), elastic modulus, hardness, thermal and morphological parameters of the irradiated composites were investigated. The examined mechanical properties have been found to improve largely with filler content. Interesting E_b behavior has been detected for the irradiated composites loaded up to ∼10 wt% GF and has been basically discussed in view of matrix crystallinity and morphology. TGA thermograms of unirradiated composites revealed enhanced thermal stability than that reported for the blend whereas comparatively slight improvement has been demonstrated by irradiation. Whereby insignificant alteration in T_m values was observed by loading or irradiation, yet ΔH_m maximum of 3.41 J/g, indicated for the 5 wt% GF irradiated composite with an integral dose of 75 kGy, emphasizes the influence of the relatively moderate load and dose levels on matrix stability. The phenomenon has been confirmed by the respective SEM micrographs.     

Structure–property relationship of electron‐beam‐modified EPDM rubber

Electron‐beam‐initiated grafting of trimethylolpropane triacrylate (TMPTA) onto the bulk ethylene propylene diene monomer (EPDM) was carried out with varying concentrations of TMPTA at a constant irradiation dose of 100 kGy and over a wide range of irradiation doses (0–500 kGy) at a fixed concentration (10%) of TMPTA. The rubber was also modified in the bulk by tripropylene glycol diacrylate (TPGDA, 10%) and tetramethylol methane tetraacrylate (TMMT, 10%) at an irradiation dose of 100 kGy. The modified rubbers were characterized by IR spectroscopy, crosslinking density measurements, and mechanical, dynamic mechanical, and electrical properties. The IR studies indicated increased peak absorbances at 1730, 1260, and 1019 cm⁻¹ due to increased 〉CO and C O C concentrations up to certain levels of TMPTA and irradiation dose. These are accompanied by an increase in the crosslinking density. The tensile strength of the samples increases gradually with increasing both the concentration of the monomer and radiation dose up to a certain level. The values of the modulus also increase at the expense of the elongation at break. An increase in the number of double bonds from two in the case of the diacrylate to four in the case of the tetraacrylate also brings about an increase in the tensile strength and moduli values. The elongation at break, however, decreases. The DMTA measurements indicate changes in the glass transition temperature, T_g, and tan δ_max on modification. The T_g shifts to a higher temperature with a simultaneous lowering of the tan δ_max values as the TMPTA level is increased. A similar trend is observed when the irradiation dose is increased and the nature of the monomer changes from di‐ to tetraacrylate. The dielectric loss tangent registers an increase on modification by irradiation of TMPTA while the permittivity is decreased. All the results could be explained on the basis of the structural modification and crosslinking density. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 323–337, 2000     

Microwave effect in removal process of NO by electron beam irradiation and quantitative prediction of the removed NO

A flow process with electron beam (EB) irradiation carried out the removal of NO in air by adding microwave (MW) to improve the removal efficiency of NO. The EB irradiation combined with MW irradiation was very effective in the range of NO removal efficiency of 70–80% and reduced required doses up to more than 30%, compared to the flow process without MW. On the other hand, MW irradiation was unlikely to affect the NO removal above 90% of removal efficiency. In addition, MW effect appeared definitely in the dose ranges of 8–24 kGy, whereas the effect became minor below 8 kGy and above 24 kGy. This study found that MW irradiation can play an auxiliary role in NO removal with EB irradiation and the effect of MW on the NO removal is based on an intrinsic kinetic to the exclusion of a thermal effect. The concentrations of removed NO could be linearly correlated as ΔC=k[NO] _o +k _o . Where, k was proportional to dose and ko could be related to k _o /D ⁿ =aD+b, giving n value of 0.7 without MW irradiation and 0.4 with MW irradiation, respectively.     

Evidence of irradiation‐induced crosslinking in miscible blends of poly(vinyl chloride)/epoxidized natural rubber in presence of trimethylolpropane triacrylate

Electron‐beam initiated crosslinking of a poly(vinyl chloride)/epoxidized natural rubber blend (PVC/ENR), which contained trimethylolpropane triacrylate (TMPTA), was carried out over a range of irradiation doses (20–200 kGy) and concentrations of TMPTA (1–5 phr). The gelation dose was determined by a method proposed by Charlesby. It was evident from the gelation dose, resilience, hysteresis, glass‐transition temperature (T_g), IR spectroscopy, and scanning electron microscopy studies that the miscible PVC/ENR blend underwent crosslinking by electron‐beam irradiation. The acceleration of crosslinking by the TMPTA was further confirmed in this study. Agreement of the results with a theory relating the T_g with the distance between crosslinks provided further evidence of irradiation‐induced crosslinking. The possible mechanism of crosslinking induced by the irradiation between PVC and ENR is also proposed. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 1914–1925, 2001     

Thermal and physicomechanical properties of gamma‐irradiated EPDM/waste newsprint microfibers composites treated using acrylic styrene emulsion as a coupling agent

This investigation deals mainly with thermal stability and crosslinking density of EPDM/newsprint microfibers composites. The recycled newsprint microfibers were treated using a different ratio of acrylic styrene emulsion (5, 10, and 15 wt% fiber) as a bonding agent to reinforce EPDM rubber matrix. The effect of microfibers content, namely, 5 up to 50 phr (part per hundred part of rubber) and the effect of ionizing radiation on EPDM/newsprint microfibers composites properties were investigated. The microfibers structure and EPDM/microfibers composite were investigated using X‐ray diffraction and FTIR analysis; the results indicate that bonding has occurred between the treated newsprint microfibers and EPDM polymer matrix. EPDM/untreated newsprint microfibers composites have achieved higher crosslinking density than EPDM matrix up to 50 phr microfibers content and up to 100 kGy then decreased with increasing gamma irradiation dose. Meanwhile treatment of the microfibers using 10 wt% acrylic styrene leads to improve crosslinking density at any microfibers content. Thermogravimetric analysis (TGA) was carried out for the microfibers and their composites. TGA indicated that the thermal stability of microfiber was enhanced using acrylic styrene. Whereas there is a slight improvement in thermal stability and activation energy of the composites due to adding treated microfibers using 10 phr microfiber content treated using10 wt% acrylic styrene emulsion and irradiated with 60 kGy gamma radiation dose. J. VINYL ADDIT. TECHNOL., 25:E91–E106, 2019. © 2018 Society of Plastics Engineers     

Short kevlar fiber–thermoplastic polyurethane composite

Mechanical and dynamic mechanical behavior of short Kevlar fiber-filled thermoplastic polyurethane (TPU) have been studied with respect to fiber loading and orientation. The strength of the composite is improved at higher fiber content with a minimum at 10 phr of fibers. Storage and loss moduli (E′, E″) are increased and tan δ_max is reduced progressively with fiber loading, the effect on moduli being more pronounced at post-T_g temperatures. Anisotropy in strength is evident beyond 15 phr fiber loading. Impact strength is reduced considerably at all fiber loading irrespective of fiber orientation. Study of the fracture furface by scanning electron microscopy (SEM) shows good correlation between the modes of failure and strength of the composites. SEM study of the extracted fibers shows the existence of a kinking stage through which the fiber undergoes severe breakage during processing.     

Thermoluminescence features of alumina-mixed borophosphate glasses with Tb3+ ions for dosimetric applications

Amorphous barium borophosphate materials doped with small quantity of terbium ions and with the addition of some amounts of alumina were prepared. Thermoluminescence (TL) characteristics of these glasses were investigated after irradiating them with different doses of γ-rays (in the range 0.5-8.0 kGy). The TL emission exhibited a dosimetric peak at about 210°C. The TL output under this glow peak is observed to increase with the γ-ray dose. For any fixed γ-ray dose, the TL output is increased with increase in Al₂O₃ content up to 3.0 mol%, and beyond this concentration, quenching of TL is visualized. The dose response of TL output of these glasses exhibited linear behavior in the dose range 0.5-4.0 kGy. The mechanisms responsible for TL emission and the variation of TL output with the concentration of Al₂O₃ are quantitatively discussed in terms of structural defects induced during γ-ray irradiation. Finally, it is concluded that these glasses are potential materials for dosimetry applications in the dose range 0.5-4.0 kGy.     

Characterization of gamma irradiated polyethylene films by DSC and X‐ray diffraction techniques

The effect of gamma radiation on the thermal behavior and crystalline structure of low density polyethylene (LDPE) has been investigated using differential scanning calorimetry (DSC) and X‐ray diffraction techniques (XRD). Gamma irradiation was carried out in atmospheric air to a maximum dose of 883 kGy. DSC results of the heating run from room temperature up to 150 °C showed that the melting temperature (T_m), and onset temperature of LDPE film decrease linearly with increasing irradiation dose. However, upon cooling LDPE film from 150 °C to room temperature, the crystallization temperature (T_c) and onset temperature were found to decrease non‐linearly with increasing irradiation dose up to 500 kGy and then tended to level off. The change in heat of fusion (ΔH_f) with irradiation dose was found to proceed with different behaviour, two stages, with a kink at irradiation dose of about 500 kGy, being observed. This suggests the occurrence of degradation and crosslinking at low and high doses, respectively. However, parameters of the X‐ray diffraction pattern such as number of diffraction patterns, peak position (2θ) and width of the diffraction pattern, support the results of DSC measurements. © 2000 Society of Chemical Industry     

Radiation crosslinking of polyethylene with electron beam at different temperatures

The effect of temperature over the range ?196 to 150°C on the crosslinking of polyethylenes irradiated by electron beam has been investigated on the basis of gel content determination and Fourier transform infra-red (FTIR) spectroscopy. The crosslinking efficiency increases significantly with increasing irradiation does and at elevated irradiation temperature. The crosslinking rates of high density polyethylene (HDPE) and low density polyethylene (LDPE) samples above the melting point (T_M) are much higher than those below T_m. The FTIR data give positive evidence: (i) that trans-vinylene double bonds in cross linked HDPE and LDPE samples increase with increasing irradiation dose temperature (ii) that vinyl double bonds in HDPE decrease rapidly with increasing irradiation dose and temperature, and (iii) vinylidene groups in LDPE decrease slowly with increasing temperature at the lower dose and are almost independent of the irradiation temperature at above room temperature and the higher dose of more than 100 kGy. Gas bubbles are observed in LDPE samples irradiated at 100 and 150°C with high dose (200 to 250 kGy). The size of the bubbles increases gradually at high temperatures.     

Electron Beam Irradiation to Recrosslink Devulcanized Sulfur Cured Rubber Blended Polypropylene

This study aims to investigate the effect electron beam (EB) irradiation on the polypropylene/devulcanized sulfur cured rubber (PP‐DVC) compound. The PP‐DVC compounds were compounded using twin‐screw extruder and then compression molded into required shapes before irradiation begins. The gel content of all irradiated PP‐DVC compounds gradually increased with higher irradiation dose indicated that the presence of DVC plays an important role in crosslinking enhancement. The mechanical properties of PP‐DVC compounds were observed marginally higher at low irradiation dosages (≤50 kGy). However, higher irradiation dosages up to 200 kGy cause adverse effect to the PP‐DVC compounds. In addition, the application of low irradiation dosage could enhance the dispersion of DVC particles at 20 phr composition in PP matrix. This also found that the scanning electron microscopy (SEM) observation where the DVC particles dispersed better in PP matrix compared to that of nonirradiated samples. Further increment in irradiation dosages up to 200 kGy reduced the crystallinity caused by chain scissoring process could rupture the crystalline structure in PP matrix. It was also found that the wavenumber of the C? H and CH₂ groups for irradiated samples reduced at high irradiation dosages due to the formation of carbonyl group. POLYM. ENG. SCI., 59:1017–1027, 2019. © 2019 Society of Plastics Engineers