Physical Properties of Cured Self-green Epoxidized Natural Rubber with Amino Acid

Journal of Polymers and the Environment - The environmental-friendly and sustainable development is a top concern of rubber industry. Here we reported a green method to fabricate a class of...     

Biodegradable Green Glove Containing Ascorbic Acid from Maleated Epoxidized Natural Rubber/Poly(vinyl alcohol) Blend: Preparation and Physical Properties

Journal of Polymers and the Environment - The objective of this work was to prepare a maleate epoxidized natural rubber (MENR) and poly(vinyl alcohol) (PVA) (MENR/PVA) blend in the presence of...     

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 Potential of Chicken Eggshell Waste as a Bio-filler Filled Epoxidized Natural Rubber (ENR) Composite and its Properties

Eggshell calcium carbonate (ECC) and eggshell calcium carbonate treated with high temperature (ECC-600) were prepared from chicken eggshell waste. ECC was obtained by crushing eggshell waste, eliminating membranes and followed by sieving. In the case of ECC-600, ECC powder was additionally heated at 600 °C for 2 h. Both were used to promote as fillers compared to that of commercial light-precipitated calcium carbonate (commercial CaCO₃) with various loading levels (i.e., 0, 25, 50 and 75 phr) in epoxidized natural rubber containing 25 mol% of epoxide group (ENR-25). Among the three types of fillers (i.e., ECC, ECC-600 and commercial CaCO₃), ECC filled materials showed superior vulcanization characteristics by the increasing of maximum torque (M_H) and cure rate index (CRI) with the reducing of cure time (t_c90) and scorch time (t_s2). The highest tensile properties as well as the lowest tension set value were also observed. Morphological property revealed that ECC was greater interfacial adhesion than those of others. In addition, dynamic mechanical properties of vulcanizates containing ECC, storage modulus (E′) was the highest and glass transition temperature (T _g ) shifted toward high temperature. Increasing of loading levels of any fillers affected the increase of M_H and CRI with reducing of t_c90 and t_s2. However, tensile properties decreased with increasing filler content but it did not affect T _g shifting except for a series of vulcanizates containing ECC.     

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.     

Preparation of Cellulose/Xanthan Gum Composite Films and Hydrogels Using Ionic Liquid

This paper reports the preparation of cellulose/xanthan gum composite films and hydrogels through gelation with an ionic liquid. Mixtures of cellulose and xanthan gum in desired weight ratios with an ionic liquid, 1-butyl-3-methylimidazolium chloride (BMIMCl), were thinly placed on a Petri dish and heated at 100 °C for 9 h to obtain the solutions. Then, the solutions were left standing at room temperature for 1 day for the progress of gelation. The resulting ion gels were subjected to Soxhlet extraction with ethanol to remove BMIMCl, followed by drying under ambient conditions to obtain the composite films. The crystalline structures of the polysaccharides and the mechanical properties were evaluated by powder X-ray diffraction measurement and tensile testing of the films, respectively. The ion gels in various cellulose/xanthan gum weight ratios, which were prepared in a test tube by the same procedure, were immersed in water for the exchange of disperse media to obtain the cellulose/xanthan gum composite hydrogels. Water contents of all the materials were higher than 90 %. The mechanical properties of the hydrogels were evaluated by compressive testing.     

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.     

Study on the Effect of Dicumyl Peroxide on Structure and Properties of Poly(Lactic Acid)/Natural Rubber Blend

In attempt to enhance the compatibility of NR in PLA matrix, and furthermore to enhance mechanical properties of PLA, PLA/NR blends with strong interaction were prepared in Haake internal mixer, using dicumyl peroxide (DCP) as cross-linker. The effects of dicumyl peroxide on morphology, thermal properties, mechanical properties and rheological properties of PLA and PLA/NR blends were studied. The results indicated that dicumyl peroxide could increase the compatibility of poly(lactic acid) and natural rubber. With small amount of dicumyl peroxide, the effect on NR toughening PLA was enhanced and the tensile toughness of PLA/NR blends was improved. When the DCP content was up to 0.2 wt%, the PLA/NR blend reached the maximum elongation at break (26.21 %) which was 2.5 times of that of neat PLA (the elongation at break of neat PLA was 10.7 %). Meanwhile, with introducing 2 wt% DCP into PLA/NR blend, the maximum Charpy impact strength (7.36 kJ/m²) could be achieved which was 1.8 times of that of neat PLA (4.18 kJ/m²). Moreover, adding adequate amount of DCP could improve the processing properties of blends: the viscosity of PLA/NR blend decreased significantly and the lowest viscosity of the blends could be achieved when the DCP content was 0.5 wt%.     

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.     

Development of Urea Uptake and Release Studies Using N,N-Dimethylacrylamide/Maleic Acid/Citric Acid Based Macrogel

Journal of Polymers and the Environment - Recently, the use of polymers in agricultural and horticultural applications has been seen as a solution to reduce water consumption and excess fertilizer...     

Comparison of Polylactic Acid/Kenaf and Polylactic Acid/Rise Husk Composites: The Influence of the Natural Fibers on the Mechanical, Thermal and Biodegradability Properties

This paper investigates and compares the performances of polylactic acid (PLA)/kenaf (PLA-K) and PLA/rice husk (PLA-RH) composites in terms of biodegradability, mechanical and thermal properties. Composites with natural fiber weight content of 20% with fiber sizes of less than 100 μm were produced for testing and characterization. A twin-screw extrusion was used to compound PLA and natural fibers, and extruded composites were injection molded to test samples. Flexural and Izod impact test, TGA, soil burial test and SEM were used to investigate properties. All results were compared to a pure PLA matrix sample. The flexural modulus of the PLA increased with the addition of natural fibers, while the flexural strength decreased. The highest impact strength (34 J m⁻¹), flexural modulus (4.5 GPa) and flexural strength (90 MPa) were obtained for the composite made of PLA/kenaf (PLA-K), which means kenaf natural fibers are potential to be used as an alternative filler to enhance mechanical properties. On the other hand PLA-RH composite exhibits lower mechanical properties. The impact strength of PLA has decreased when filled with natural fibers; this decrease is more pronounced in the PLA-RH composite. In terms of thermal stability it has been found that the addition of natural fibers decreased the thermal stability of virgin PLA and the decrement was more prominent in the PLA-RH composite. Biodegradability of the composites slightly increased and reached 1.2 and 0.8% for PLA-K and PLA-RH respectively for a period of 90 days. SEM micrographs showed poor interfacial between the polymer matrix and natural fibers.     

Effects of Acid Rain on Competitive Releases of Cd, Cu, and Zn from Two Natural Soils and Two Contaminated Soils in Hunan, China

Leaching experiments of rebuilt soil columns with two simulated acid rain solutions (pH 4.6–3.8) were conducted for two natural soils and two artificial contaminated soils from Hunan, south-central China, to study effects of acid rain on competitive releases of soil Cd, Cu, and Zn. Distilled water was used in comparison. The results showed that the total releases were Zn>Cu>Cd for the natural soils and Cd>Zn≫Cu for the contaminated soils, which reflected sensitivity of these metals to acid rain. Leached with different acid rain, about 26–76% of external Cd and 11–68% external Zn were released, but more than 99% of external Cu was adsorbed by the soils, and therefore Cu had a different sorption and desorption pattern from Cd and Zn. Metal releases were obviously correlated with releases of TOC in the leachates, which could be described as an exponential equation. Compared with the natural soils, acid rain not only led to changes in total metal contents, but also in metal fraction distributions in the contaminated soils. More acidified soils had a lower sorption capacity to metals, mostly related to soil properties such as pH, organic matter, soil particles, adsorbed SO₄ ²⁻, exchangeable Al³⁺ and H⁺, and contents of Fe₂O₃ and Al₂O₃.     

二硫化碳萃取—气相色谱法同时测定含盐酸废水中的甲苯、邻氯甲苯、对氯甲苯和氯化苄

建立了二硫化碳萃取—气相色谱法同时测定含盐酸废水中甲苯、邻氯甲苯、对氯甲苯和氯化苄的方法,并应用于实际水样的测定。采用二硫化碳萃取含盐酸废水中的甲苯、邻氯甲苯、对氯甲苯、氯化苄,待测物质经30QC3/AC20（30 m×0.32 mm×0.50 μm）毛细管柱气相分离。采用保留时间定性,外标法定量。实验结果表明,甲苯、邻氯甲苯、对氯甲苯和氯化苄的质量浓度在0.2~100.0 mg/L范围内与对应的峰面积呈良好的线性关系,检出限分别为0.09,0.12,0.13,0.10 mg/L。该方法的精密度和准确度较高,相对标准偏差小于2%,加标回收率在96.4%~101.0%之间。