Sonosynthesis of microcellulose from kenaf fiber: optimization of process parameters

Green composites using cellulose fibers as a reinforcement material provide a sustainable and renewable alternative to petroleum-based polymers. However, controlling the usage of chemicals and processing parameters to extract the cellulose could be sometimes difficult. Therefore, this study aims to optimize the conditions for extracting the microcellulose from kenaf fibers using central composite design (CCD), a statistical tool in design of experiments. Three factors and three levels were chosen for carrying out the analysis. The design was based on sodium hydroxide (NaOH) dosage, Sodium Chlorite (NaClO2) dosage and sonication time as independent variables, while dependent variables were the fiber size and degradation point. Later, size responses were fitted using quadratic polynomial model and degradation responses using 2-factor interaction model (2FI). The R2 values of 0.89 and 0.83 were obtained for the quadratic and the 2FI model, respectively. Further, surface morphology, thermal analysis, Fourier transform infrared (FTIR) spectroscopy and X-Ray diffraction (XRD) were also used for design validation. Optimal parameters for microcellulose extraction were found to be 0.15 g of NaOH at first stage, 4.6 mL of NaClO2 at second stage, and 10 min of sonication during third stage

Electron beam irradiation of low-density polyethylene filled with metal hydroxides for wire and cable applications

The effects of electron beam irradiation for crosslinking of polymers used for wire and cable insulations are still being researched. In this research, the influence of electron beam irradiation on the different blends of low-density polyethylene (LDPE) filled with aluminum trihydrate and magnesium hydroxide (ATH, MH) were studied. It was revealed by melt flow index, tensile strength, and elongation at break tests that addition of MH to LDPE increases the adhesion forces inside polymer matrices more efficient than similar ATH/LDPE compounds. Field emission scanning electron microscopy test showed that MH is platy in structure and more homogenous mixed than ATH with LDPE. The results on thermogravimetric analysis and limiting oxygen index tests revealed that the thermal stability and incombustibility properties of MH blends are more efficient than similar ATH blends. Meanwhile, it was observed by smoke density test that MH blends produce the lowest smoke density compared with virgin LDPE and similar ATH blends. It was also observed that increasing irradiation by electron beam had impressive affections on the density, gel content, and mechanical properties for all the polymeric samples in this study

Validation and field application of tailor-made nitrogen dioxide passive samplers

This study describes the validation and field application of new tailor-made passive samplers for nitrogen dioxide measurements. These samplers consist of polypropylene diffusion tubes containing glass fiber filters impregnated with 20 % triethanolamine. The tube was constructed from locally made material. The sampler is simple, lightweight, cheap, easy to use and suitable for simultaneous and multipoint measurements. Nitrogen dioxide concentrations obtained from the passive samplers were strongly correlated with chemiluminescence analyzer (r = 0.924). The nitrogen dioxide measurements by the passive samplers have been recorded at 20 sampling sites in Chiang Mai City, Thailand, once a month (3 days of exposure) from November 2007 to April 2008. The sampling sites were located across the city in alignment with the major wind direction. The highest nitrogen dioxide concentrations (28.1–45.1 ppbv) were found in the urban areas with high level of traffic density and human activity. Meteorological conditions, i.e., wind direction/speed and precipitation, were considered for their influence on nitrogen dioxide concentrations. Due to a calm wind occurring during the sampling, its direction had, therefore, no significant effect on nitrogen dioxide concentrations collected from the different locations. However, the mean nitrogen dioxide concentrations were higher at the downwind sites than at the upwind locations. Unlike wind, rain precipitation obviously affected pollutant concentration levels. In regard to the spatial and temporal variations of nitrogen dioxide concentrations in the study sites, it was deduced that their levels were much more affected by local activities, such as traffic density and biomass burning, rather than meteorological factors

Validation and field application of tailor-made nitrogen dioxide passive samplers

This study describes the validation and field application of new tailor-made passive samplers for nitrogen dioxide measurements. These samplers consist of polypropylene diffusion tubes containing glass fiber filters impregnated with 20 % triethanolamine. The tube was constructed from locally made material. The sampler is simple, lightweight, cheap, easy to use and suitable for simultaneous and multipoint measurements. Nitrogen dioxide concentrations obtained from the passive samplers were strongly correlated with chemiluminescence analyzer (r = 0.924). The nitrogen dioxide measurements by the passive samplers have been recorded at 20 sampling sites in Chiang Mai City, Thailand, once a month (3 days of exposure) from November 2007 to April 2008. The sampling sites were located across the city in alignment with the major wind direction. The highest nitrogen dioxide concentrations (28.1–45.1 ppbv) were found in the urban areas with high level of traffic density and human activity. Meteorological conditions, i.e., wind direction/speed and precipitation, were considered for their influence on nitrogen dioxide concentrations. Due to a calm wind occurring during the sampling, its direction had, therefore, no significant effect on nitrogen dioxide concentrations collected from the different locations. However, the mean nitrogen dioxide concentrations were higher at the downwind sites than at the upwind locations. Unlike wind, rain precipitation obviously affected pollutant concentration levels. In regard to the spatial and temporal variations of nitrogen dioxide concentrations in the study sites, it was deduced that their levels were much more affected by local activities, such as traffic density and biomass burning, rather than meteorological factors