Improvement of Physico-Mechanical Properties of Radiation-Vulcanised Natural Rubber Latex Films by Adding Urea

The role of urea as an additive on the physico-mechanical properties of radiation vulcanised natural rubber latex (RVNRL) films was investigated. RVNRL films were prepared by the addition of urea with the concentration range 0–1.0 phr (parts per hundred rubber) and irradiated with various radiation doses (0–20 kGy). The concentration of urea and radiation doses were optimised and found to be 0.5 phr urea and 12 kGy radiation dose. Tensile strength, tear strength and cross-linking density of the rubber films increased with increasing the concentration of urea as well as radiation doses. The tensile and tear strengths of the films enhanced by 39 and 41%, respectively, at the optimum conditions. Elongation at break, permanent set and swelling ratio of the films decreased with increasing urea concentration and radiation doses until they attained approximately constant values.     

Improvement of Physicochemical Properties of Natural Rubber and Polyvinyl Alcohol Blends by Radiation Vulcanization

Variable compositions of natural rubber latex (NRL) and polyvinyl alcohol (PVA) have been blended. The contents of PVA in the blends were varied from 0.5 phr to 3.0 phr and the total solids contents of NRL was fixed to 50%. The blends were irradiated at different irradiation doses (0–20 kGy) in the presence of normal butylacrylate (n-BA). The permanent set; swelling ratio and elongation at break point of the blended films at all compositions decrease with the increase of radiation doses whereas increase is observed in cross-linking density, gel content, tensile strength and modulus. Sharp changes of all the properties were observed between 3–5 kGy radiation doses. On the other hand, at higher radiation doses, ≥ 5 kGy, the permanent set, swelling ratio, gel content did not show any appreciable change whereas cross-linking density, tensile strength, modulus and elongation at break point are changed. The maximum cross-linking density of blend is observed with 2.0 phr PVA at 12 kGy radiation. The highest value of modulus and tensile strength of the same blend are found at 10 kGy and 5 kGy respectively. Blends with 2.0 phr PVA for all compositions proved to be optimum for improving varies properties at 5–12 kGy radiation doses.     

Improvement of Physicochemical Properties of Rubber Blends Between Nonirradiated and Irradiated Rubber Latexes by Radiation Vulcanization

Abstract

Nonirradiated natural rubber latex (NRL) and irradiated (12 kGy) rubber latex were blended in ratios of 100:0, 85:15, 65:35, 50:50, 35:65, 15:85, and 0:100 (v/v) to improve properties of the rubber latex. The blends were irradiated using different irradiation doses (0–20 kGy) in the presence of a radiation vulcanization accelerator (RVA), normal butyl acrylate (n-BA). The physicochemical properties of the nonirradiated latex, irradiated latex, and blend films were determined after leaching with distilled water. It was observed that the tensile strengths of the blend films increases with an increase in the content of the irradiated proportion and radiation doses. The composition of the blends and the doses of radiation were optimized. The maximum tensile strength (31.41 MPa) was found for the 50:50 composition of the blend with a 5 kGy radiation dose. The 100:0 blends, when irradiated, give the highest tensile strength (27.69 MPa) with 12 kGy but a 15:85 nonirradiated blend gives the tensile strength of 26.18 MPa.     

Study on the Properties of Blend Rubber Between Grafted Rubber Latex and Natural Rubber Latex by Gamma Radiation

Blend rubber films were prepared by mixing styrene grafted rubber latex and natural rubber latex (NRL) with varying proportions by gamma radiation from Co-60 source at room temperature. Tensile strength, modulus at 500% elongation, elongation at break, permanent set, and swelling ratio were measured. Tensile strength and modulus at 500% elongation attain maximum at 8 kGy radiation dose for blend rubber films. The increase in tensile strength is insignificant, but modulus increases from 5.61 to 7.46 MPa with increased proportion of grafted rubber latex from 40 to 70% in the blend at this radiation dose. Elongation at break, permanent set, and swelling ratio of blend rubber decreases with increase in radiation dose as well as proportion of grafted rubber.     

Effect of crosslinking monomers on the performance of electron beam-induced biodegradable Bionolle–rubber blends

To find out the better crosslinking monomer for vulcanization of natural rubber under electron beam (EB) radiation, the dry rubber was masticated with different polyfunctional monomers like TMPTA, NVP, and ethylene glycol diacrylate of different numbers of CH₂ CH₂ O group, such as 1G, 3G, 7G, and 10 G. The masticated films were irradiated with different doses under EB at 10 kGy/pass. The highest tensile strength (25 MPa) of the rubber was observed in the presence of TMPTA (3phr) at 150 kGy dose. The gel content of the rubber increased with an increase of dose. Bionolle was mixed with the masticated rubber containing 3 phr TMPTA at different proportions; films of these blends along with Bionolle were irradiated under EB with different doses. The concentration of rubber in Bionolle and radiation dose were optimized. The elastomer with 5% masticated showed the highest tensile strength (62 MPa). The gel content of the blends was found to increase with an increase of radiation dose as well as rubber concentration in Bionolle. The elastomers or blends were found to possess good thermal properties. The elastomers exhibited a much lower loss of tensile strength due to the thermal aging compared with pure Bionolle. The elastomers sustained their original shape for 300 min at 180°C, whereas Bionolle sustained its shape for only 3 min at 120°C under the same load (50 g). Among all the elastomers, 5% rubber containing elastomer was found to be better in all respects. It was observed from scanning electron microscopy and differential scanning calorimetry studies that 5% rubber is well mixed with Bionolle. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 799–807, 2001     

Reinforcement of natural rubber latex film by ultrafine calcium carbonate

Using ultrafine calcium carbonate to reinforce natural rubber latex film, the effect of its content on latex properties such as surface tension, viscosity, mechanical stability, and heat stability and the physical properties of latex film before and after aging such as tear strength, modulus, and tensile strength were investigated. The results showed that the surface tension of natural rubber latex reinforced by ultrafine calcium carbonate only changed slightly; when the content of calcium carbonate was less than 20%, the change of viscosity was not obvious, but when the content was greater than 20%, the viscosity significantly lowered. Ultrafine calcium carbonate could effectively improve the tear strength, tensile strength, and modulus of the natural rubber latex film. The modulus increased with the increment of the calcium carbonate. When the content of calcium carbonate was less than 15%, the tear strength and tensile strength increased with the increments of calcium carbonate, but when the content was greater than 15%, the above‐mentioned properties decreased with the increment of calcium carbonate. By comprehensive consideration, the best reinforcing effect was obtained at a content of 15% ultrafine calcium carbonate. The particle diameters of calcium carbonate and their distribution in the calcium carbonate emulsion and in the rubber film were analyzed with SEM and a laser particle size tester, which showed that the distribution of calcium carbonate in the latex film was even and that it could effectively reinforce natural rubber latex film. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 982–985, 2003     

Curing Characteristics and Aging Properties of Natural Rubber/Epoxidized Natural Rubber and Cellulose II

In this work, natural rubber (NR) and regenerated cellulose (cel II) latexes were co-coagulated and to the mixture epoxidized natural rubber (ENR) was added on a two-roll mill. The cellulose content was fixed at 20 phr while ENR content varied from 0 to 75 phr. The influence of ENR was studied through the cure characteristics, aging and dynamic-mechanical properties. The aging provides nanocomposites with better solvent resistance and increased tensile strength at ENR content of 25 phr. The results suggest that a new type of light-colored nanocomposites were obtained, which presented high mechanical performance and resistance to solvents.     

Preparation and characterization of organoclay‐rubber nanocomposites via a new route with skim natural rubber latex

Skim natural rubber latex (SNRL) is a protein rich by‐product obtained during the centrifugal concentration of natural rubber (NR) latex. A new method to recover rubber hydrocarbon and to obtain nanocomposites with organoclay (OC) was investigated. The approach involved treatment of SNRL with alkali and surfactant, leading to creaming of skim latex and removal of clear aqueous phase before addition of OC dispersion. Clay mixed latex was then coagulated to a consolidated mass by formic acid, followed by drying and vulcanization like a conventional rubber vulcanizate. X‐ray diffraction (XRD) studies revealed that NR nanocomposites exhibited a highly intercalated structure up to a loading of 15 phr (parts per hundred rubber) of OC. Transmission electron microscopy studies showed a highly exfoliated and intercalated structure for the NR nanocomposites at loadings of 3–5 phr organically modified montmorillonite (OMMT). The presence of clay resulted in a faster onset of cure and higher rheometric torque. The rubber recovered from skim latex had a high gum strength, and a low amount of OC (5 phr) improved the modulus and tensile strength of NR. The high tensile strength was supported by the tensile fractography from scanning electron microscopy. Thermal ageing at 70°C for 6 days resulted in an improvement in the modulus of the samples; the effect was greater for unfilled NR vulcanizate. The maximum degradation temperature was found to be independent of the presence and concentration of OC. The increased restriction to swelling with the loading of OC suggested a higher level of crosslinking and reinforcement in its presence. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 3277–3285, 2006     

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     

Influence of Aging on Autohesive Tack of Brominated Isobutylene-co-p-methylstyrene (BIMS) Rubber in the Presence of Phenolic Resin Tackifier

The role of phenolic resin tackifier on autohesive tack of brominated isobutylene-co-p-methylstyrene (BIMS) rubber was studied by a 180° peel test with particular reference to aging. Phenolic resin showed very little effect on the unaged tack of BIMS rubber. The tack strength of the rubber/resin mixture marginally increased at 1 phr resin concentration, beyond which it decreased. Based on the data on the compression creep, maximum tensile stress, and viscoelastic properties of the rubber/resin mixtures, phenolic resin did not enhance the interfacial viscous flow behavior of the rubber/resin mixtures. The results from dynamic mechanical analysis (DMA) and scanning electron microscopy (SEM) confirmed the existence of a phase-separated morphology in the rubber/resin blends even at low resin concentration. Upon aging at 100°C for 36 h, the rubber/resin blend containing 1 phr of phenolic resin showed further increase in tack strength which was attributed to migration of the tackifier to the rubber surface and the changes in the compression creep, viscoelastic behavior, and maximum tensile stress of the rubber/resin mixtures. This is also a function of aging time. Surface energy analysis by contact angle measurement, Fourier Transform Infrared Spectroscopy (FT-IR/ATR) studies, and surface roughness measurement by atomic force microscopy (AFM) elucidate the enrichment of the phenolic resin on the rubber surface upon aging and the mechanism of enhanced tack strength.     

硫黄用量对天然胶乳膜性能的影响

采用凝固剂浸渍法制备天然胶乳硫化胶膜,并对其结构和性能进行研究。结果表明：天然胶乳预硫化程度随硫黄用量的增加而增大;胶膜硫化后的交联程度随硫黄用量的增加先增大后减小,在硫黄用量为1.25份时达到最大值;拉伸强度随硫黄用量的增加先增大后减小,在硫黄用量为1份时达到最大值,而拉断伸长率呈下降趋势;当硫黄用量为1份时达到最佳致密性。     

Electron‐beam‐induced crosslinking of natural rubber/acrylonitrile–butadiene rubber latex blends in the presence of ethoxylated pentaerythritol tetraacrylate used as a crosslinking promoter

A natural rubber latex, an acrylonitrile–butadiene rubber latex, and their 50: 50 blends were exposed to an electron beam in air. A polyfunctional monomer, ethoxylated pentaerythritol tetraacrylate, was used as a crosslinking promoter. Cast films from the irradiated systems were characterized for their gel contents, swelling properties, and tensile strength. An increase in the radiation dose from 0 to 500 kGy resulted in increased crosslinking, as measured by an increase in the gel content and better swelling resistance. The effect of the polyfunctional monomer, ethoxylated pentaerythritol tetraacrylate, as a crosslinking promoter was studied with infrared spectros copy. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 1206–1214, 2007     

The Effect of Filler Loading and Epoxidation on Paper-Sludge-Filled Natural Rubber Composites

The effect of filler loading and epoxidation on curing characteristics, dynamic properties, tensile properties, morphology, and rubber-filler interactions of paper-sludge-filled natural rubber compounds have been studied. Two different types of natural rubber, SMR L and ENR 50, having 0% and 50% of epoxidation and conventional vulcanization were used. Paper sludge was used as a filler and the loading range was from 0 to 40 phr. Compounding was carried out using a laboratory-sized two-roll mill. The scorch time for both rubber compounds decreased with filler loading. The cure time was found to decrease with increasing filler content for SMR L vulcanizates, whereas for ENR 50, the cure time seemed to be independent of the filler loading. Dynamic properties, i.e., maximum elastic torque, viscous torque, and tan delta, increase with filler loading in both grades of natural rubber. Results also indicate that both rubbers show increment in tensile modulus but inverse trend for elongation at break and tensile strength. However, for a fixed filler loading, ENR 50 compounds consistently exhibit higher maximum torque, modulus at 100% elongation, and modulus at 300% elongation, but lower elongation at break than SMR L compounds. In the case of tensile strength, ENR 50 possesses higher tensile strength than SMR L at 10 to 20 phr, but the difference is quite small at 30 and 40 phr. These findings might be associated with better rubber-filler interaction between the polar hydroxyl group of cellulose fiber and the epoxy group of ENR 50.     

Accelerated electron effects on EVA based compound

The major effects induced by accelerated electron irradiation on EVA based polymeric compound were evaluated for various doses up to 240 kGy. Some main characteristics (gel fraction, density, elongation at break, and tensile strength) were investigated. Oxygen uptake and thermal analysis methods (TG, DTG, and DTA) were applied for determination of oxidation resistance of radiation processed EVA samples. It was established that a 30 kGy exposure dose promotes maximum crosslinking. At this dose the density and tensile strength reach maximum values, which are maintained for higher doses up to 240 kGy. On the other hand, the thermooxidative stability exhibits a sharp decrease as the absorbed dose rises from 0 to 30 kGy and has a constant value for the absorbed dose range 30–240 kGy. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 613–617, 2005     

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     

Effect of electron beam radiation on the performance of biodegradable Bionolle-jute composite

To study the radiation effect on the physical, thermal, mechanical and degradable properties of biodegradable polymer Bionolle (chemosynthetic polyester poly(1,4-butylene succinate)), Bionolle films prepared by compression molding process and were irradiated with electron beam (EB) radiation of different doses. Gel content was found to increase with increase of radiation dose. Tensile strength of Bionolle was enhanced when Bionolle film was exposed under 20 kGy radiation. The loss of tensile strength of both unirradiated and irradiated Bionolle is 70% and 8% due to thermal aging at 70°C for 30 days. Both irradiated and unirradiated films of Bionolle were subjected to different degradation test in compost (soil burial), enzyme and storage degradation both in outdoor and indoors conditions. The loss of weight due to soil (compost) degradation test decreased with increase of radiation dose. The loss of weights of irradiated samples were found to be very less within the first three months of compost degradation. After 120 days, tensile strength of the Bionolle films irradiated at 20 kGy and 100 kGy were 68 MPa and 40 MPa, respectively, compared to the value (30 MPa) of the unirradiated Bionolle samples. Loss of tensile strength of irradiated Bionolle due to storage degradation like in roof, ground and indoors was minimum compared to unirradiated Bionolle. The weight loss due to enzymatic degradation was found to be decreased with increase of radiation dose. The tensile strength of jute reinforced Bionolle composites (23 wt.-% jute content) irradiated at 20 kGy was found to be higher (22%) than that of an unirradiated composite.     

Short polyethylene terephthalate fiber (PET) reinforced NBR rubber composites

Acrylonitrile-butadiene rubber (NBR) has been reinforced with different content of PET up to 25 phr. Vulcanization of prepared composites as will as the unreinforced ones have been induced by ionizing radiation of accelerated electron beam of varying dose up to 150 kGy. Evaluations of the vulcanized composites have been followed up through the measurement of mechanical, physical and thermal properties. Also, scanning electron microscope (SEM) was performed. Mechanical properties, namely tensile strength (TS) and hardness were found to increase with the increase of irradiation dose as well as the increase in the content of PET up to 25 phr. Also, elongation at break (ε _b) was found to decrease with the increase of irradiation dose; however, the decrease in ε_b is not consistence with the increase in fibers loading. Young’s modulus (E) and tensile modulus at 25% elongation (E25) were found to increase with the increase of irradiation dose and fiber loading up to 20 phr. Also, the volume fraction of swollen rubber increases as irradiation dose and/or fiber content increased; it was more influenced by irradiation rather than fiber loading. Anisotropic swelling increased with irradiation and fiber loading up to 20 phr. SEM photomicrograph showed that irradiation causes adhesion between PET fiber and NBR where less pulling out and less pitting on the surface were observed. The thermal properties of the composite irradiated at 100 kGy reveal that the activation energy (E _a) increases up to 10 phr fiber content. When the composite that contains 10 phr fiber irradiated at doses higher than100 kGy, Ea decreased.     

Thermal properties and aging characteristics of chemically modified oil palm ash-filled natural rubber composites

The chemically modified oil palm ash (OPA) with the cetyltrimethylammonium bromide (CTAB) solution was prepared prior to compounding with the natural rubber and other curing ingredients. The aging resistance and thermal stability of CTAB-modified OPA-filled natural rubber composites were evaluated in the same manner as non-modified OPA samples. The retention tensile properties after thermal aging was measured and based on the result shown, the CTAB-modified OPA-filled natural rubber composites imparted insignificant effect to aging resistance as compared to the non-modified OPA-filled natural rubber composites at very low OPA loading; however, the effect became apparent beyond 3 phr OPA loading where the CTAB-modified OPA-filled natural rubber composites provided better aging resistance than the corresponding non-modified OPA-filled natural rubber composites. The thermogravimetric analysis indicated that the CTAB-modified OPA-filled natural rubber composites exhibited lower thermal stability which showed lower temperature at their respective weight loss and lesser char residue than that of non-modified OPA-filled natural rubber composites. This was attributed to the CTAB which started to decompose at the temperature of 210 °C. However, for the range from ambient temperature to 210 °C, the CTAB-modified OPA-filled natural rubber composites produce better thermal stability than those of non-modified OPA-filled natural rubber composites.     

Toughening of dicyandiamide-cured DGEBA-based epoxy resins by CTBN liquid rubber

Toughening of a diglycidyl ether of bisphenol-A (DGEBA)-based epoxy resin with liquid carboxyl-terminated butadiene acrylonitrile (CTBN) copolymer has been investigated. For this purpose six blend samples were prepared by mixing DGEBA with different concentrations of CTBN from 0 to 25 phr with an increment of 5 phr. The samples were cured with dicyandiamide curing agent accelerated by Monuron. The reactions between oxirane groups of DGEBA and carboxyl groups of CTBN were followed by Fourier-transform infrared (FTIR) spectroscopy. Tensile, impact, fracture toughness and dynamic mechanical analysis of neat as well as the modified epoxies have been studied to observe the effect of CTBN modification. The tensile strength of the blend systems increased by 26 % when 5 phr CTBN was added, and it remained almost unchanged up to 15 phr of CTBN. The elongation-at-break and Izod notched impact strength increased significantly, whereas tensile modulus decreased gradually upon the addition of CTBN. The maximum toughness of the prepared samples was achieved at optimum concentration of 15 phr of CTBN, whereas the fracture toughness (K _IC) remained stable for all blend compositions of more than 10 phr of CTBN. The glass transition temperature (T _g) of the epoxy resin significantly increased (11.3 °C) upon the inclusion of 25 phr of CTBN. Fractured surfaces of tensile test samples have been studied by scanning electron microscopic analysis. This latter test showed a two-phase morphology where the rubber particles were distributed in the epoxy resin with a tendency towards co-continuous phase upon the inclusion of 25 phr of CTBN.     

Cure Characteristics and Mechanical Properties of Short Nylon-6 Fiber Neoprene Rubber Composite Containing Epoxy Resin as Bonding Agent

ABSTRACT

Cure characteristics and mechanical properties of the short nylon fiber reinforced neoprene rubber with and without epoxy bonding agent at various fiber loadings were studied. The fiber loading was varied from 0 to 30 phr and the resin content was in the range 0 to 5 phr. Minimum torque and cure time were increased in the presence of resin. Mechanical properties like tensile strength and abrasion resistance showed an increase with resin concentration. It was found that epoxy based bonding agents enhanced the properties of short nylon fiber reinforced neoprene rubber.