Fabrication of Polypropylene Nanofibers from Polypropylene/Polyvinyl Butyral Blend Films Using Laser-Assisted Melt-Electrospinning

Polypropylene (PP) nanofibers, a few hundred nanometers in diameter, are of immense importance in the fiber industry. This article reports the fabrication of delicate PP nanofibers. Polyvinyl butyral (PVB) was added to PP as a blend component, and a nozzle-free melt-electrospinning system with a line-like CO₂ laser melting device was used to manufacture PP nanofibers. We investigated the effect of PVB ratio on fiber diameter. The addition of PVB was found to be potentially very beneficial in PP/PVB blends, resulting in improved PP crystallinity and a steady decrease of fiber diameter with high productivity. The reduction of fiber diameter was attributed to the decline of viscosity, increase of surface adhesion properties, and polarity of blends due to the inclusion of PVB. To produce PP nanofiber, the PVB was removed from PP/PVB blend fibers with an ethanol treatment. A drastic drop of PP fiber diameter followed by fiber splitting was observed after PVB removal. We obtained PP nanofibers with a diameter as low as 181 ± 105 nm from the blend fiber with 90% PVB. Infrared spectroscopy of fibers demonstrated that PP fibers from pure polymer and blends showed the same characteristic peaks. POLYM. ENG. SCI., 60: 362–370, 2019. © 2019 Society of Plastics Engineers     

Improvement of thermal conductivity and dielectric constant of graphene-filled epoxy nanocomposites using colloidal polymerization approach

Polymer Bulletin - The effect of the polymeric cross-link density on the thermal conductivity of an oxidized graphene (OG)-filled epoxy nanocomposite was investigated by two different fabrication...     

Generating Synthetic Rainfall Total Using Multivariate Skew-<Emphasis Type="Italic">t</Emphasis> and Checkerboard Copula of Maximum Entropy

This study aims to test the appropriateness of multivariate skew-t copula and checkerboard copula of maximum entropy in generating monthly rainfall total data. The generation of synthetic data is important, as it provides hypothetical data in areas for which data availability remains limited. Three selected meteorological stations in Kelantan, Malaysia, Stesen Pertanian Melor, Rumah Pam Salor, and Ladang Lepan Kabu, are considered in this study. Monthly rainfall total data for the driest and wettest months in the year are tested in this study. For these three stations, the identified month with the least total of rainfall received (driest) is May, while the month with the highest total of rainfall received (wettest) is November. The data is fitted to gamma distribution with the corresponding parameters estimated. The observed data will be transformed to be in unit uniform using the gamma marginal. The resulting data is compared to simulated uniform data generated using multivariate skew-t copula and checkerboard copula of maximum entropy models based on the correlation values of the observed and simulated data. Next, the Kolmogorov-Smirnov test is used to assess the fit between the observed and generated data. The results show that the values of simulated correlation coefficients do not differ much for gamma distribution, multivariate skew-t, and maximum entropy approaches. This implies that the multivariate skew-t and maximum entropy may be used to generate monthly rainfall total for cases in which actual data is unavailable.     

Distribution of linear alkylbenzenes (LABs) in riverine and coastal environments in South and Southeast Asia

This paper reports the result of sewage pollution monitoring conducted in South and Southeast Asia during 1998-2003 using linear alkylbenzenes (LABs) as molecular tracers of sewage contamination. Eighty-nine water samples collected from Malaysia, Vietnam, and Japan (Tokyo), and 161 surface sediment samples collected from Tokyo, Thailand, Malaysia, Philippines, Vietnam, Cambodia, Indonesia, and India were analyzed for alkylbenzenes. The concentration range of SigmaLABs in river water particles in Southeast Asia (<0.005-0.913 microg/L) was comparable to or higher than those found in Tokyo (<0.005-0.638 microg/L). I/E ratios (a ratio of internal to external isomers of LABs) in tropical Asian waters were close to the value of LABs in raw sewage ( approximately 1) and much lower than those in secondary effluents (3-5). This suggests that untreated or inadequately treated sewage is discharged into the water. SigmaLABs concentrations in sediments from South and Southeast Asia ranged from <0.002-42.6 microg/g-dry with the highest concentration occurring at several populous cities. Low I/E ratios of the sediments with high SigmaLABs concentrations suggest a heavy load of untreated sewage. Clearly in view of the current data and evidence of the implications of sewage pollution, this paper highlights the necessity of the continuation of water treatment system improvement in tropical Asia.     

Multiple Linear Regression Model for Total Bed Material Load Prediction

A new total bed material load equation that is applicable for rivers in Malaysia was developed using multiple linear regression analyses. A total of 346 hydraulic and sediment data were collected from nine natural and channelized rivers having diverse catchment characteristics in Malaysia. The governing parameters were carefully selected based on literature survey and field experiments, examined and grouped into five categories namely mobility, transport, sediment, shape, and flow resistance parameters. The most influential parameters from each group were selected by using all possible regression model method. The suitable model selection criteria namely the R-square, adjusted R-square, mean square error, and Mallow’s Cp statistics were employed. The accuracy of the derived model is determined using the discrepancy ratio, which is a ratio of the calculated values to the measured values. The best performing models that give the highest percentage of prediction from the validation data were chosen. In general, the newly derived model is best suited for rivers with uniform sediment size distribution with a d50 value within the range of 0.37–4.0 mm and performs better than the commonly used Graf, Yang, and Ackers–White total bed material load equations.     

Gene-Expression Programming for the Development of a Stage-Discharge Curve of the Pahang River

This study presents Gene-Expression Programming (GEP), an extension of Genetic Programming (GP), as an alternative approach to modeling the stage-discharge relationship for the Pahang River. The results are compared to those obtained by more conventional methods, i.e., the stage rating curve (SRC) and regression techniques. Additionally, the explicit formulations of the developed GEP models are presented. The performance of the GEP model was found to be substantially superior to both GP and the conventional models.     

Latex-coated polymeric monolithic ion-exchange stationary phases. 2. Micro-ion chromatography

Latex-coated monolithic polymeric stationary phases are used for micro-ion chromatography (mu-IC) of inorganic anions. Monolithic columns were prepared by the in situ polymerization of butyl methacrylate, ethylene dimethacrylate, and 2-acrylamido-2-methyl-1-propanesulfonic acid within fused-silica capillaries of varying internal diameters. Introduction of ion-exchange sites was achieved by coating the anionic polymeric monolith with either Dionex AS10 or Dionex AS18 quaternary ammonium functionalized latex particles to give total ion-exchange capacities in the range 9-24 nequiv for a 30-cm column. The resultant mu-IC columns were used for the separation of anionic analytes using chloride or acetate as the eluent-competing ion and direct UV spectrophotometric detection at 195 nm or using hydroxide as the eluent-competing ion and suppressed or nonsuppressed contactless conductivity detection. Separation efficiencies of 13,000 plates/m were observed (for iodate), and separation efficiency was maintained for large increases in flow rate (up to 42 microL/min, corresponding to a linear flow velocity of 18.5 mm/s), enabling highly reproducible, rapid separations to be achieved (seven analyte anions in less than 2 min). Use of a hollow fiber micromembrane suppressor enabled effective suppression of hydroxide eluents over the range 0.5-5.0 mM, thereby permitting suppressed conductivity detection to be performed. However, the relatively large size of the suppressor resulted in reduced separation efficiencies (e.g., 5400 plates/m for iodate). Detection limits obtained with suppressed conductivity detection were in the range 0.4-1.2 microM.     

Removal of cadmium and manganese by a non-toxic strain of the freshwater cyanobacterium Gloeothece magna.

The ability of both living and dry cells of Gloeothece magna, a non-toxic freshwater cyanobacterium, to adsorb cadmium and manganese is demonstrated in this study. Chlorophyll a content of living cells was not influenced by either cadmium or manganese concentrations, indicating that adsorption of both Cd²⁺ and Mn²⁺ by living cells of G. magna, was independent of the metabolic state of the organism. Moreover, the adsorption of both Cd²⁺ and Mn²⁺ to living cells and dry cells, was dependent on the metal concentrations, and fitted the Freundlich adsorption isotherm. However, dry cells had larger binding capacity for both Cd²⁺ (K_f=912.6) and Mn²⁺ (K_f=2398) than living cells (K_f=151.4 & 63, respectively). The role of the capsular polysaccharides, the main constituents of the cyanobacterial envelope, in binding these two metals was also studied. Polysaccharide extracts of this organism adsorbed high amounts of both Cd²⁺ (115–425 μg mg⁻¹) and Mn²⁺ (473–906 μg mg⁻¹). This study suggests that G. magna would probably be cultured in water bodies contaminated by heavy metals to ameliorate their toxicity. Also dry material of this cyanobacterium being a non-toxic species, could be used as a safe biofilter to remove toxic metals from drinking water.     

Finite Element Analysis of Glass Fiber‐Reinforced Polyamide Engine Oil Pan Subjected to Localized Low Velocity Impact from Flying Projectiles

This paper investigates low velocity impact involving a glass fiber‐reinforced polyamide engine oil pan as part of a complete new development of thermoplastic components. The assessment of the impact resistance has driven the need to employ LS DYNA for finite element modeling in order to benchmark and predict the strength and fracture behavior of stressed plastic parts. In order to develop a reliable predictive capability and to validate simulations, complete components were manufactured by injection molding techniques for the experimental samples. Low velocity impact investigations were carried out using a gas gun and a falling weight tester in order to simulate impact events to which the oil pan is subjected whilst in operational service. This was intended to point out damage tolerance and failure mechanisms likely to occur in the structure. The study results show the significant contribution of the design in terms of shock absorption. Specific oil pan design with protective ribbing combined with a superior material considerably improves the impact resistance. The paper provides results and discussions on experimental and finite element analysis investigations before concluding with some remarks.