Study of Fatigue Life and Filler Interaction of Paper Sludge Filled Epoxidized Natural Rubber (ENR) and Maleated Natural Rubber (MNR) Composites

An investigation on the effect of epoxidation and maleated natural rubber (MNR) on fatigue and rubber-filler interaction properties of paper sludge filled natural rubber composites was elucidated. Paper sludge loading was varied from 0 to 40 phr and conventional vulcanisation system was used while compounding was carried out on a laboratory sized two roll mill. Two different types of natural rubber, SMR L and ENR 50 having 0 and 50 mole% of epoxidation were used in order to investigate the effect of epoxidation on the composites. Results indicate that, at a fixed filler loading, ENR 50 vulcanizates exhibit higher fatigue life than SMR L vulcanizates especially at filler loading below 20 phr which might be associated with better rubber-filler interaction. In the case of composites with the addition of maleated natural rubber (MNR), a higher fatigue life was observed due to presence of physical and/or chemical linkages, which increases the interfacial adhesion. Scanning electron microscopy (SEM) micrographs of fatigue fracture surfaces and rubber-filler interaction study supported the observed result on fatigue life.     

The Use of Interfacial Blend to Increase the Adhesion Properties of Natural Rubber/Polyvinylalcohol Multilayer Using Electron Beam Irradiation

Multilayers of natural rubber (NR) and polyvinylalcohol (PVA) were processed by casting natural rubber latex (NRL) then PVA with varying layer thickness. Adhesion between NR and PVA was found to be very poor, as determined with the peel method. The films of interfacial blend were composed of NRL and PVA having different ratios as a layer between NR/PVA layer, possessing good adhesion and exhibited one mechanical phase in tensile-elongation at break tests. The result of adhesion was confirmed by thermogravimetric analysis and scanning electron microscopy study. Also, adhesion was too strong for delamination at the interface when the unit of three layers NR/blend/PVA was irradiated at 25 kGy. To probe the effect of the adhesion difference on mechanical behavior and deformation of NR/blend/PVA layers at dry and wet conditions, the peel strength was examined as a function of layer thickness and aging time. The results indicated that the interfacial blend, irradiation process and film thickness were the key parameters affecting adhesion of NR/PVA layer.     

Effect of Poly(Vinyl Acetate) on Mechanical Properties and Characteristics of Poly(Lactic Acid)/Natural Rubber Blends

Natural rubber grafted with poly(vinyl acetate) copolymer (NR-g-PVAc) was synthesized by emulsion polymerization. Three graft copolymers were prepared with different PVAc contents: 1 % (G1), 5 % (G5) and 12 % (G12). Poly(lactic acid) (PLA) was melt blended with natural rubber (NR) and/or NR-g-PVAc in a twin screw extruder. The blends contained 10–20 wt% rubber. The notched Izod impact strength and tensile properties were determined from the compression molded specimens. The effect of NR mastication on the mechanical properties of the PLA/NR/NR-g-PVAc blend was evaluated. Characterization by DMTA and DSC showed an enhancement in miscibility of the PLA/NR-g-PVAc blend. The temperature of the maximum tan δ of the PLA decreased with increasing PVAc content in the graft copolymer, i.e., from 71 °C (pure PLA) to 63 °C (the blend containing 10 % G12). The increase in miscibility brought about a reduction in the rubber particle diameter. These changes were attributed to the enhancement of toughness and ductility of PLA after blending with NR-g-PVAc. Therefore, NR-g-PVAc could be used as a toughening agent of PLA and as a compatibilizer of the PLA/NR blend. NR mastication was an efficient method for increasing the toughness and ductility of the blends which depended on the blend composition and the number of mastications.     

Preparation of Liquid Epoxidized Natural Rubber by Oxidative Degradations Using Periodic Acid,Potassium Permanganate and UV-Irradiation

Epoxidized natural rubber (ENR) needs to be degraded into shorter chain lengths, to form liquid epoxidized natural rubber (LENR), for applications such as coating and adhesives. Since ENR contains both C=C and epoxide groups as reactive sites for degradation reactions, thus, LENR could be prepared by different methods through cleavages of C=C or epoxide groups, or a combination of both sites. Different mechanisms would produce different terminals on the LENR. This paper reports the oxidative degradation by (a) periodic acid, (b) potassium permanganate and (c) ultra violet (UV) irradiation. The degraded rubbers were characterized by gel permeation chromatography (GPC), nuclear magnetic resonance (NMR) and Fourier transform infra-red spectroscopy (FTIR). Ester and ketone terminals were formed in all the three methods, but lactone and hydrofuranic structures were observed only in degradation by UV irradiation. NMR spectrum reveals that cyclization of ENR has occurred during degradation by periodic acid. At lower periodic acid concentration, degradation takes place only via C=C cleavage, but at higher concentration, the attack to the epoxide groups becomes more prominent. Potassium permanganate has attacked both the double bonds and epoxide groups. On the other hands, epoxide group was not affected during degradation by UV irradiation, which cleaved only the C=C bonds.     

Preparation of Natural Rubber/Condensed Tannin Semi-interpenetrating Polymer Network Composites by Hematin-Catalyzed Cross-Linking

In this study, the preparation of semi-interpenetrating polymer network (semi-IPN) composites composed of natural rubber and condensed tannin was performed by means of the enzyme-mimetic cross-linking of condensed tannin catalyzed by hematin. Prior to the preparation of the composites, the hematin-catalyzed cross-linking behavior of condensed tannin was evaluated by the TGA measurement. The TGA results indicated that condensed tannin was sufficiently cross-linked by the hematin-catalyzed reaction in the presence of appropriate amounts of 30% (w/v) H₂O₂ aq. to give the relatively thermostable materials. For the preparation of the composites, a solution of condensed tannin and hematin, and subsequently 30% (w/v) H₂O₂ aq. were added to natural rubber latex and the mixture was stirred at room temperature for 10 min to perform the cross-linking of condensed tannin, followed by drying of the reaction mixture at 50 °C for 5 h, which was subsequently put into a heat device and hot-pressed at 100 °C and 20 MPa for 20 min to give the semi-IPN composite. The tensile stress?Cstrain measurement of the composites was conducted to evaluate the mechanical properties, which were changeable depending on the weight ratios of natural rubber to condensed tannin and the amounts of 30% (w/v) H₂O₂ aq. Moreover, the miscibility of the cross-linked tannin with natural rubber in the composite was evaluated by the SEM measurement.     

Mexican High Rubber Producing Guayule Shrubs: A Potential Source for Commercial Development

Guayule is a shrub native to Mexico growing in semiarid lands, that may be incorporated into the semiarid region production system as a complement for annual crops. The possibility to develop this natural resource as a sustainable industrial source of natural rubber, may improve the socio-economical level of people living at the guayule region and favor the agricultural development near the US-Mexico border. Despite the existence of natural stands in Mexico with guayule plants of different rubber content, a program envisaging selection of plants with high rubber synthesis potential joined to agronomic management practices are required. This could achieve the rubber yield needed to guarantee a constant supply of raw material for an industrial processing plant. This paper reviews R&D work carried out in Mexico for the last 25 years, including genetic aspects and evaluation of guayule response to environmental and agronomic factors. Relevant results showed plants with up to 21% rubber content and the existence of diploid plants, which could facilitate future plant breeding programs.     

Comparison of end-of-life tire treatment technologies: A Chinese case study

The aim of this paper is to compare different end-of-life tire (ELT) treatment technologies in China from an environmental and economic perspective. Four treatment technologies were evaluated: ambient grinding, devulcanization, pyrolysis and illegal tire oil extraction.Life cycle assessment (LCA) was applied to evaluate the potential environmental impact of each treatment based on the Eco-indicator 99 (Hierarchist approach) method provided by GaBi 4 software. The final result shows that pyrolysis represents the environmentally benign option while illegal tire oil extraction caused the worst damages. For the three legal treatments, although high credit was obtained when considering avoided impacts from recycled materials and energy, they have great impact as to respiratory effects (inorganic) dominantly contributed by energy production stage, which implies that the emphasis on environmental policies related to ELT treatment should shift from the control of emissions from treatment process to the reduction of energy consumption.A simplified comparison of net benefits and total impacts shows that the most eco-effective ELT treatment technology is pyrolysis, followed by dynamic devulcanization and ambient grinding. The illegal tire oil extraction, however, must be prohibited immediately because of its highest environmental pollution and lowest net benefit.     

Microbial Degradation of the Natural Rubber in Tire Tread Compound by a Strain of Nocardia

Tread compound of truck tires is based primarily on natural rubber or blends of natural rubber (NR) and synthetic polymers in combination with high grade carbon black. When the tread compound is attacked by a strain of Nocardia capable of degrading NR, part of the NR in the compound is mineralized, and part is disintegrated to very small black particles. The small black particles consist of the residual rubber and inorganic fillers. At higher NR content, large and deep cavities are formed on the surface of the pieces of the tread compound after microbial disintegration. At lower content of NR, large but very shallow cavities or very small pits can be seen on the tread surface. During microbial growth on the tread compound, isoprene oligomers with molecular weight of about two thousand are produced. Not only the isoprene oligomers, but also butadiene oligomers are produced during microbial disintegration of the tread compound of NR/synthetic rubber blend.     

Processing and Characterization of Recycled Polypropylene and Acrylonitrile Butadiene Rubber Blends

In this paper investigation on thermoplastic elastomers (TPE) and thermoplastic vulcanizates (TPV) derived from waste polypropylene (WPP) of Municipal Solid Waste (MSW) and acrylonitrile-butadiene rubber (NBR) are reported. The WPP was segregated, cleaned, dried and melt processed with NBR at 180 °C in a Brabender Plasticorder at different blend ratios. TPV was prepared by dynamic vulcanization of the TPE with conventional sulfur accelerator curing system. The mechanical properties measured were found to decrease with increase in NBR proportion in the blend; however the dynamic vulcanization of the nitrile rubber phase enhanced the strength properties of the corresponding TPE. The crystallinity of the WPP reduced with increase in NBR ratio. The dynamic modulus decreased with nitrile rubber content in the TPE. Interestingly, the storage modulus of the TPV at higher rubber content enhanced significantly and damping characteristics increased sharply. The rheology studies reveal that the damping of the blend has been reduced with the addition of high storage modulus rubber at melt processing conditions and hence increased viscosity. The amorphous rubber content with higher storage modulus imparts higher viscosity for the polypropylene (PP) matrix at the processing temperature. The SEM study reveals that the dynamic vulcanization of the rubber phase in the blend caused a smoother and finer surface morphology.     

Devulcanization of Ground Tires by Different Strains of Bacteria: Optimization of Culture Condition by Taguchi Method

Biological devulcanization of ground tires (GTs) was evaluated by eleven different bacteria belonging to the genera Thiobacillus, Gordonia, Nocardia, Amycolaptopsis and Pseudomonas. The GTs were treated by each bacterium in a mineral medium and devulcanization was measured by increasing the sulfate of the medium and decreasing the sulfur of the GTs. The effects of incubation time (10 and 20 days) and the percent of ground tire in the medium (0.5 and 5 w/v %) on desulfurization were investigated. No significant changes were observed after 10 days of incubation. The total sulfur contents of all bio-treated GTs were decreased by 6–21% in 0.5% GTs after 20 days of incubation. While in 5% GTs, the total sulfur contents were mainly decreased using Thiobacillus ferroxidans DSMZ 583 and PTCC 1647 up to 27 and 15%, respectively. SEM photograph further indicated a good coherency interface between the bacteria and the GTs. Subsequently, Taguchi method was applied for the optimization of the culture condition of DSMZ 583. An L12 orthogonal array was performed by which the effects of eleven factors in two levels were evaluated. It was found that the amount and mesh size of GTs are the most important factors in biological devulcanization of ground tires.     

A Novel Environmentally Compatible Bio-Based Product from Gelatin and Natural Rubber: Physical Properties

The objective of the present work was to study the preparation of a novel bio-based product from gelatin (GT) and natural rubber (NR) using potassium persulphate (KPS) as an initiator. The GT and NR composites (GT/NR composites) containing KPS were formed in an aqueous latex solution. The chemical structure of the GT/NR composite was characterized by ATR-FTIR, and XRD. The highest tensile strength was observed in a 9/1 GT/NR composite and the elongation at break of this composite was improved by the addition of both NR and glycerol. In addition, the swelling ratio increased as a function of increasing GT content in the composite. The thermal stability of the GT was improved after the formation of the chemical interaction between the NR and GT helped by the KPS. The best ratio of the GT/NR composite was 3/7 GT/NR. This environmentally friendly composite easily decomposed in natural soil within 30 days. The novel biopolymer showed high mechanical properties, water resistance and was produced in an environmentally compatible process. The NR was able to improve some of the physical and mechanical properties of GT biofilms produced from the composite. Possible future applications of this composite are for medical materials, and the packaging and life extension of food products.     

Effect of Nucleating Agents on Physical Properties of Poly(lactic acid) and Its Blend with Natural Rubber

Poly(lactic acid) (PLA) presents high strength and modulus, but very low toughness as well as slow crystallization. Natural rubber (NR) was blended to enhance the toughness and nucleating agent was added to improve the crystallization. Cyclodextrin (CD), considered as a green compound, as well as calcium carbonate (CaCO₃) and talc were used as nucleating agents. Effects of these nucleating agents on crystallization, mechanical properties and morphology of neat PLA and PLA/NR blend were investigated. It was found that the addition of talc and CD decreased cold crystallization temperature (T_cc) of the PLA. Same result was obtained in PLA/NR blend containing talc. All nucleating agents increased the degree of crystallinity (Χ_C) of PLA, whereas only talc and CaCO₃ increased Χ_C of PLA in PLA/NR blends. The enhanced toughness of PLA by the addition of nucleating agent was attributed to its increased crystallinity, as well as decreased spherulite size. For PLA/NR blends, the increase in toughness was mainly contributed by the presence of the rubber.     

Cetyltrimethyl Ammonium Bromide Modified Kaolin as a Reinforcing Filler for Natural Rubber

Cure characteristics, Mooney viscosity and physico-mechanical properties of natural rubber (NR) containing CTAB modified kaolin have been studied. NR mix containing 6 phr (parts per hundred part rubber) of CTAB modified kaolin showed significant increases in cure rate and state of cure as compared to gum NR compound and a mix containing the same amount of unmodified kaolin. Lower Mooney viscosity of the NR mix containing CTAB modified kaolin suggested improved processability. Reinforcing effect of CTAB modified kaolin in NR was evident from higher chemical crosslink density index, tensile modulus, hardness, tensile strength and tear strength. Besides, the NR vulcanizate containing 6 phr of CTAB modified kaolin showed lower abrasion loss and heat build-up which could be beneficial for applications such as tire treads.     

Visualization of the Malleability of the Rubber Core of Rubber Particles from Parthenium argentatum Gray and Other Rubber-Producing Species Under Extremely Cold Temperatures

Rubber particles from Parthenium argentatum Gray (guayule) were frozen in liquid nitrogen (–196°C), fractured, and visualized using cryo-scanning electron microscopy. We observed that the rubber polymer core of the rubber particles was still malleable at this extremely cold temperature, and the core stretched substantially during separation of the fracture planes. This malleability was observed in situ in tissue sections, as well as in purified rubber particles, and was found to be independent of purification procedure, guayule line, tissue age, or season. The malleability or stretching phenomenon suggests that P. argentatum rubber has some unique properties because rubber particles from Hevea brasiliensis Müll. Arg. and Ficus elastica Roxb. were brittle at this temperature, fractured cleanly, or showed only tiny threads of material pulling out of the core.     

A Novel Packaging Film from Cassava Starch and Natural Rubber

Currently, there is an environmental pollution problem generated in part by packaging materials produced from non-biodegradable synthetic polymers made from petroleum. However, these can be replaced with biodegradable materials made from cassava starch (CS) and natural rubber (NR). In the work described, a novel biopolymer film was obtained from the CS and NR using glycerol (GE) as a plasticizer in a water-based system. The physical properties of an 95/5 CS/NR blend films with the addition of NR and with varying GE contents were studied based on their swelling ratio, moisture content, moisture absorption, mechanical properties and biodegradability in soil. The results showed that the moisture content and moisture absorption tended to be directly proportional to the GE content, while the moisture content and moisture absorption of the sample decreased as a function of the NR content. The swelling ratio of the 95/5 CS/NR blend slightly decreased as a function of the NR and GE content. Surprisingly, the best swelling ratio of 350% was found at 10% NR. The elongation at break of the CS/NR blend was improved by the addition of GE. The contact angle of the 95/5 CS/NR blend decreased as a function of the GE. With increased NR in the composite, an increasing, trend in the contact angle was found. Further, the 95/5 CS/NR blend exhibited good transparency when it was applied as a coating to delay the ripening of bananas, the results were positive. Moreover, the film showed decomposition well in natural soil.     

Propranolol Hydrochloride Film Coated Tablets Using Natural Rubber Latex Blends as Film Former

Journal of Polymers and the Environment - The aim of this study was to investigate the feasibility of concentrated natural rubber latex (CNRL), a major polymer, blended with either...     

空气涡轮制冷低温粉碎法回收废弃橡胶

利用带回冷循环的空气涡轮制冷系统，在低温条件下，将废旧橡胶进行冷冻、粉碎、制成６０目以上的精细胶粉。此法的冷冻能耗成本仅为国际上通用的液氮法的１／１０，整具工艺过程不产生二次污染，为废旧橡胶的综合利用提供了一条新途径。     

Improvement of Physico-Mechanical Properties of Photo-Cured Chitosan Films with Ethylene Glycol Dimethacrylate and (2-Hydroxyethyl) Methacrylate

Chitosan, a natural polymer, was prepared by deacetylation of chitin which was obtained from dried prawn shell and was characterized. Thin chitosan film of chitosan was prepared by casting method from 0.2 % chitosan in 2 % acetic acid solution. Five formulations were developed with ethylene glycol dimethacrylate and (2-hydroxyethyl) methacrylate along with photo-initiator, Darocur-1664 (4 %). The chitosan film was soaked in the formulations at different soaking times and irradiated under UV-radiation at different intensities for the improvement of its physical and mechanical properties. The cured chitosan films were then subjected to various mechano-chemical tests like tensile strength, elongation at break, polymer loading, water absorption and gel content. The formulation containing 30 % ethylene glycol dimethacrylate and 66 % (2-hydroxyethyl) methacrylate showed the best performance at the 30th UV pass of UV-radiation for 3 min soaking time.     

The Biodegradation of Latex Rubber: A Minireview

Natural rubber is used for the production of adhesives, latex gloves, tubing and tires. This widespread use is accompanied with an extensive generation of waste rubber material. In many parts of the world, especially industrialized countries, this has prompted legislation to be passed to govern the proper disposal of rubber waste. Even so, the recycling of this polymer is not widely practiced. This review looks at the useful bacteria capable of degrading this recalcitrant polymer. Furthermore we review the mechanism of action and the identification of rubber degrading genes. Clearly, a deep understanding of this biodegradative process at the biochemical and genetic level exists and should prompt the instigation of this knowledge in biotechnological applications.     

Biodegradation of Natural Rubber and Natural Rubber Products by <Emphasis Type="Italic">Streptomyces</Emphasis> sp. Strain CFMR 7

The rubber degrading activity of Streptomyces sp. CFMR 7 whose whole genome sequence was recently determined was tested with non-vulcanized fresh latex and common vulcanized rubber products such as latex glove, latex condom and latex car tyre. The degradation activity was unequivocally demonstrated by scanning electron microscopy with respect to microbial colonization efficiency, disintegration of rubber material and biofilm formation after 3, 6 and 9 months of inoculation. Fourier transform infrared spectroscopy comprising the attenuated total reflectance analysis on these inoculated products revealed insights into the biodegradation mechanism of this strain whereby, a decrease in the number of cis -1,4 double bonds in the polyisoprene chain, the appearance of ketone and aldehyde groups formation indicating an oxidative attack at the double bond of rubber hydrocarbon. In the presence of strain Streptomyces sp. CFMR 7, gel permeation chromatography analysis revealed a significant shift of the molecular weight distribution to lower values. Clear decrease in the molecular weight was observed over 3, 6 and 9 months of cultivation on fresh latex samples compared to other vulcanized products. No shift in the molecular weight distribution was observed for non-inoculated control. These results clearly showed that Streptomyces sp. CFMR 7 was able to cleave the carbon backbone of poly (cis -1,4-isoprene). Although this strain was able to degrade both non-vulcanized and vulcanized rubber products, faster degradation was obtained with natural rubber and rubber products with low complexity.