Yong Yue Luo

Preparation and Characterization of Epoxidized Natural Rubber

Epoxidized Natural Rubber is prepared with latex processing technology. The relationships of the epoxidation with the reaction times and temperature were investigated. The structure of ENR was characterized by Fourier transform-infrared spectroscopy (FIIR). It is found that, the by products, ring-open components increases with the reaction temperatures and the reaction times. It is found that as the level of epoxidation increased, the number of tetrahydrofuran ring increased.

Preparation and Properties of Interpenetrating Polymer Network Films from Prevulcanized Natural Rubber Latex/Chitosan Blends

The acidfied sulfur-prevulcanized natural rubber (NR) latex was mixed with 1～20 parts per hundred rubber (phr) of a 2wt% solution of chitosan (CS) in 1wt% acetic acid, then cast to preapare a series of NR/CS semi-interpenetrating polymer network (semi-IPN) films; the NR/CS semi-IPN films were further treated with 0.5wt% glutaraldehyde（GA）solution for respectively 1, 3 and 6h to obtain NR/CS IPN films. The mechanical properties and swelling behavours in various media of water, toluene and reference olis of IRM901 and IRM 903 of these films were studied and compared with those pure sulfur-prevulcanized natural rubber latex (SNRL) film. Results showed that, NR/CS IPN films with better mechanical properties could be obained by treating the 24h-leached NR/CS semi-IPN films than by treating directly the unleached ones with 0.5wt% GA solution; the tear strength, 300% modulus, Shore A hardness, hydrophilicity and resistance to non-polar solvents and oil of the SNRL films increased with the incorporation of CS, while the NR/CS IPN films exhibited better than the NR/CS semi-IPN films, especially in tear strength enhancement; the tensile strength and elongation at break of NR/CS semi-IPN and IPN films gradually decreased with the increase in CS content. However, most of the elasticity of pure NR vulcanizate could be reserved, when the CS content was not greater than 15 phr.

Surface Modification of Natural Rubber Latex Film by N-Vinypyrrolidone Graft Copolymerization

The surface modification of natural rubber (NR) latex film by argon plasma pretreatment and subsequent UV-induced graft copolymerization of N-vinypyrrolidone (NVP) was carried out to improve the hydrophilic behavior. The effects of plasma pretreatment time and UV irradiation time on the graft yields were studied. The peroxide functionalities formed by the oxidations in air after plasma pretreatment are the activated species for the subsequent UV-induced graft copolymerization of NVP. ATR-FTIR and XPS analyses indicate that the PVP molecules have covalently bonded onto the surface of NR latex film. The argon plasma pretreatment time of 2min and UV irradiation time of 10min are the proper conditions for the graft polymerization of NVP onto NR latex film, which can reduce the water contact angle value of NR latex film from 95o to about 57o.

Role of Epoxidized Natural Rubber in Dynamic Mechanical Properties of NR/ENR/silica Composites

NR/ENR/silica composites with different ENR amount were prepared in an open two-roll laboratory mixing mill at room temperature. Dynamic properties of ENR filled NR/silica were performed by dynamic mechanical thermal analyzer (DMA) and compression fatigue analyzer. DMA and compression fatigue test results showed that the effect of ENR on dynamic properties of NR/silica was significant. DMA displayed the tanδ of NR/ENR/silica composites at 0 °C was increased with increasing ENR amount. Compression fatigue test indicated the presence of ENR decreased the heat produced during compression test and the heat build-up is the least when NR to ENR ratio is 80 to 20. Scanning electron microscopy was used to investigate the morphology of NR/silica filled with ENR. It is found that silica self-aggregation was improved in the presence of ENR and sea-island structure was formed in NR/silica when 30phr ENR added, which maybe the reason of decrement of heat produced during compression.

Damping Performance of CB Filled NR/ENR, NR/BR and NR/IIR Compounds

Natural rubber (NR)/epoxidized natural rubber (ENR)/carbon black (CB), natural rubber/butadiene rubber (BR)/carbon black and natural rubber/isobutylene-isoprene rubber (IIR)/carbon black compounds were prepared by mechanical mixing method. The mechanical properties, dynamic mechanical properties for the compounds were investigated respectively. The temperature range of tanδ>0.3 of NR/ENR40/CB compound was wider and shifted to high temperature than NR/CB compound. Comprehensive analysis indicated that NR/BR/CB and NR/IIR/CB compounds had no better damping performance than NR/CB compounds, while NR/ENR/CB compound had better damping performance.

Study on the Fabrication of Degummed Tilapia Fish Scale and its Adsorption of Carmine

Fish scale, a by-product of fish processing, contains abundant of hydroxyapatite. Boiling fish scale in alkaline solution can fabricate adsorbent for sewage treatment. Degumming experiment had been investigated by exploring different heating time. Adsorption experiment had compared the adsorption effect of carmine by different fish scale sample. The results indicated that degummed fish scale had the best adsorption effect for containing both surface adsorption by hydroxyapatite and electrostatic adherence by collagen.

Surface Modification of Natural Rubber Latex Film Using Photocrosslinkable Chitosan

Surface modifications of natural rubber latex films were carried out to improve the hydrophilicity by UV-induced immobilization of water-soluble butyryl derivative of chitosan using the photosensitive hetero-bifunctional crosslinking reagent, 4-azidobenzoic acid. The effects of the concentration of modified chitosan solution and UV irradiation time on the water contact angle values of natural rubber latex films were studied. ATR-FTIR analyses confirmed that the O-butylrylchitosan molecules were covalently bonded onto the surface of natural rubber latex film. The water contact angle value of natural rubber latex film which is about 95o reduces to 55o significantly with the introduction of O-butylrylchitosan. The results indicate that the hydrophilic behaviour of natural rubber latex film has been improved by immobilization of O-butylrylchitosan.

Effect of Calcium Stearate Concentration on Tensile Properties of Epoxidized Natural Rubber

The tensile strength and elongation at break of epoxidized natural rubber (ENR) was investigated by adding different concentration of calcium stearate. Two grades of epoxidized natural rubber (ENR), namely, ENR 25 and ENR 40 were used as model materials. Semi-efficient vulcanization (semi-EV) was used throughout the study. The tensile property of unaged and aged ENR vulcanizates was determined by using U-CAN electron tensile testing machine. Results indicate that tensile strength and elongation at break of unaged ENR 25 and ENR40 vulcanizates increase gradually with increasing concentration of calcium stearate up to about 1phr of calcium stearate and after which, the tensile strength and elongation at break drop with a further increase in calcium stearate loading. For a similar alcium stearate concentration, the tensile strength and elongation at break of ENR 40 vulcanizates exhibits a consistently higher value than that of ENR 25 vulcanizates, which is due to the higher crosslink density of ENR40 which contains more epoxide groups than ENR 25. For aged samples, the addition of calcium stearate could enhance the tensile strength and elongation at break of aged samples. Percentage retention of tensile strength and elongation at break also gradually increases with calcium stearate loading. That means that the incorporation of calcium stearate is found to improve the aging resistance of ENR vulcanizates. This is because calcium stearate neutralizes sulfur acids which can catalyze ring-opening of expoxide groups via ether crosslinks.

Effect of Calcium Stearate Concentration on Cure Properties of Epoxidized Natural Rubber

Two grades of epoxidized natural rubber (ENR), namely, ENR 25 and ENR 40 were mixing through adding 0-5 phr calcium stearate. The effect of calcium stearate concentration on cure characteristics of ENR was studied. The cure properties were determined by Moving Die Rheometer (MDR 2000) at 150°C. It showed that the scorch time (TS1) for ENR 25 and ENR 40 increased to a maximum value at 1 phr of calcium stearate, and further addition of calcium stearate maked it decrease. The cure time (T90), maximum torque (MH) and torque difference (MH﹣ML) of ENR decreased with increasing calcium stearate loading. For a fixed calcium stearate concentration, the scorch time (TS1) and cure time (T90) of ENR 40 were shorter than that of ENR 25, which is attributed to the activation of an adjacent double bond by the epoxide group in ENR. The results indicate that the effect of calcium stearate concentration on the cure characteristics of epoxidized natural rubber is remarkable.

Thermal and Thermo-Oxidative Degradations of Deproteinized Natural Rubber and Natural Rubber

Deproteinization of natural rubber was achieved in the latex stage. The structure of deproteinized natural rubber (DPNR) was characterized by fourier transform infrared spectroscopy (FTIR). The thermo degradation of DPNR was studied by thermogravimetry analysis (TG) under air atmosphere and nitrogen atmosphere. The kinetic parameters apparent activation energies (Ea) of the thermal decomposition reaction been calculated from the TG curves using the method described by Broido. And the results were compared with the thermo degradation of natural rubber (NR) under the same conditions. The effect of proteins in natural rubber latex on thermal/ thermo-oxidative stability of NR was discussed. The results show that: the absorptions of the proteins in DPNR at 1546 ㎝-1, compared to NR, become significantly weaker, nearly disappear, which indicates most of proteins has been removed from NR. The thermo degradation of DPNR in nitrogen atmosphere is a one-step reaction. The initial degradation temperature (T0) 、the maximum degradation temperature（Tp） and the final degradation temperature（Tf）as well as the Ea of DPNR are higher than those of NR, which indicates that DPNR represents a better thermal stability than NR under nitrogen atmosphere. Thermo-oxidative degradation of DPNR and NR are two-step reaction. The characteristic temperatures (T0, Tp and Tf) of DPNR are lower than those of NR. The Ea during the First Step of Thermooxidative Degradation of DPNR are also lower than those of NR. These results prove that the thermo-oxidative stability of DPNR is worse than that of NR. Protein is the key role to the thermal stability of natural rubber.