Air Dried Sheet Research Articles

Influence of alkaline treatment and acetone extraction of natural rubber matrix on properties of carbon black filled natural rubber vulcanizates

In this study, air dried sheet (ADS) showed higher molecular weight, proteins, lipids and more gel content than the low protein natural rubber (LPNR) from alkaline treatment or acetone-extracted natural rubber (AENR). After removal of proteins and lipids, LPNR and AENR had shorter scorch and cure times among the rubber compounds observed. This is due to higher content of free fatty acids, glycerides and sodium salts of fatty acid that might act as cure activators with sulfur curing. Furthermore, a finer dispersion of CB was found in ADS, due to chemical interactions of CB with proteins and lipids at terminal ends of NR molecules. Also, high molecular weight and gel in ADS could induce a higher reinforcing index (α) resulting to superior mechanical, dynamic, thermo-mechanical, hardness and crosslink density. In contrast, CB agglomerates occurred in LPNR and AENR with low molecular weight and reduced proteins and lipids, causing inferior mechanical, dynamic, thermo-mechanical, along with loss of stiffness and crosslink density.

Drying Modeling and Energy Consumption of Air Dried Sheet (ADS) Rubber by Solar and Biomass Energy

This research aims were to evaluate drying kinetics model for describing evolution of moisture transfer of air dried sheet (ADS) rubber by using solar and biomass drying, multi-stages solar and biomass drying [2 stages (2S) and 3 stages (3S)] and conventional open-sun (OS) drying. The experiments were carried out under the conditions of ADS rubber drying with temperature of 30-60°C. Initial moisture contents of sample rubber were varied between 20 and 50% dry-basis. The final moisture content for each drying strategies was fixed at 1±0.05% dry-basis. The experimental drying results were mathematical simulated by 7 common non-linear empirical models. The results showed that fresh rubber sheets drying with OS technique took longer drying time than those of solar and biomass drying. And the simulated data using approximation of diffusion model was the best fitting to experimental data of rubber sheet. Effective diffusivity of ADS rubber was also determined using the 2nd Ficks law of diffusion and conclusion was that effectice diffusivity was dependent on drying temperature and was in order of 10-7 m2/s. With various drying strategies, the results showed that specific energy consumption of 3-stages ADS rubber drying had a relatively low compared to the other drying techniques.

Determination of Isosteric Heat and Entropy of Sorption of Air Dried Sheet Rubber Using Artificial Neural Network Approach

Equilibrium moisture contents (EMC) of air dried sheet (ADS) rubber were determined by commonly gravimetric-static method with saturated salt solution among surrounding temperatures of 40-70°C correlated to water activity (aw) ranges between 0.10 and 0.9. The experimental results was analyzed by 5 commonly EMC model. The results showed that equilibrium moisture content of ADS rubber decreased with increase of surrounding temperature at constant water activity and the simulated data using Chung-Pfost model has a good relation to experimental data with R2, RMSE and χ2 equal 0.9565, 0.0235 and 0.0006, respectively. However some physical property of ADS rubber sample affects to evaluate EMC modeling. Due to avoid this effect, thus the aim of this research work was to determine EMC value by using Artificial neural network (ANN) method and also evaluate the isosteric heat of sorption by following the Clausius-Clapeyron equation. The results showed that simulated results using ANN approach has relatively high accuracy compared to common EMC model. Finally determination of isosteric heat of sorption and entropy of sorption of ADS rubber were carried on. The results stated that the enthalpy and entropy of heat sorption was power function and polynomial function of moisture content respectively. These two parameters of ADS rubber can be used for prediction suitable storage condition and drying condition for ADS rubber drying in the near future work.

Effect of Rubber Clone on Fatty Acid Composition and Properties of Air Dried Sheet

Properties of air dried sheet (ADS) made from four different clones of Hevea brasiliensis (BPM24, RRIM600, PR255 and PB235) were investigated. BPM24, RRIM600 and PR255 rubbers show a bimodal molar mass distribution (MMD) while PB235 rubber has quasi-unimodal molar mass distribution. It was found that ADS from rubber clone with bimodal MMD (BPM24, RRIM600 and PR255) displayed lower original plasticity (P0) but higher plasticity retention index (PRI). Those rubber samples with bimodal MMD show higher accelerated storage hardening test (ASHT) values than ADS from PB235. Within bimodal rubbers, ADS from PR255 displayed lower PRI and P than the 2 other clones, i.e. RRIM600 and BPM24. ADS made from BPM24 and RRIM600 presented similar fatty acid composition with 3 major fatty acids namely linoleic acid (C18:2), stearic acid (C18:0) and oleic acid (C18:1). In contrast, major fatty acids of ADS made from PR255 were linoleic acid (C18:2) and furan fatty acid. Moreover, ADS from PB235 showed the highest amount of furan fatty acid which confirmed the results of Liengprayoon et al. [1]. Relationship between mesostructure, fatty acids composition and ADS properties are discussed.

Drying Model, Shrinkage and Energy Consumption Evaluation of Air Dried Sheet Rubber Drying System for Small Enterprise

The main objective of this research was to study drying kinetics of air dried sheet (ADS) rubber using hot air and simulated drying kinetics by empirical model compared to experimental results. The 10-15 fresh rubber sheet with initial moisture content ranging of 23-40% dry-basis was dried by temperature of 40-70°C and air flow rate of 0.7 m/s. The fresh rubber sheet samples were dried until the desired final moisture content reached to 0.15% dry-basis. The experimental results showed that the drying rate of ADS rubber dried with hot air convection was faster than conventional natural air convection and drying rate was related to drying temperature. The experimental data was statistical non-linear regression analyzed by using 10 conventional empirical models. The coefficient of determination (R2) and root mean square error (RMSE) values were used as the criteria for selecting the best equation to describe the experimental data The results showed that the calculated results of Verma et al.’ model had a good relation to the experimental results. For specific energy evaluation, the results showed that at high drying temperature specific energy consumption of ADS rubber was relatively low compared to drying with low temperature. Finally, the determination of physical quality showed that.

Rheological properties of maleated natural rubber/polypropylene blends with phenolic modified polypropylene and polypropylene- g-maleic anhydride compatibilizers

Maleated natural rubber was prepared using natural rubber (air-dried sheet) and maleic anhydride by a melt mixing process under high shearing action. Two types of blend compatibilizers: graft copolymer of polypropylene and maleic anhydride (PP- g-MA), and phenolic modified polypropylene (Ph-PP) were also synthesized in a molten state. The 60/40 MNR/PP blends were later prepared by a melt mixing process using PP- g-MA and Ph-PP at various loading levels of 3, 5, 10, 15 and 20 wt% of PP. Shear flow properties of the blends were later characterized. We found that the apparent shear stress and shear viscosity increased with an increase in apparent shear rate over a range of loading levels of compatibilizers of 0–5%. This may be attributed to the chemical interaction between different phases of the blend caused by compatibilizers. They consist of segments chemically reactive to their respective counterparts in the polymer pairs. The increase in chemical interaction between the interface caused an improvement of interfacial tension and led to decreasing size of dispersed domains of the minor phase (PP) in the MNR matrix. Increasing loading level of compatibilizers higher than 5 wt% caused a decreasing trend of the flow properties. This may be attributed to the formation of micelles dispersed in the MNR matrix. Therefore, the apparent shear stress and shear viscosity decreased because the micelles act as a lubricant in the polymer melt flow. The log additive rules was applied to the flow properties and it was found that the 60/40 MNR/PP blends with PP- g-MA and Ph-PP compatibilizers indicated positive deviation blends. That is, the blends were partially compatible blends. The power law equation was also applied to the shear flow properties. We found that at a loading level of compatibilizers of 5 wt%, the lowest n value was observed. This indicates the highest pseudoplasticity of the polymer melts.