Shishir Sinha

Wood flour–reinforced plastic composites: a review

Abstract The light weight, easy availability, and biodegradability of natural fiber composites afford a variety of uses of these materials for the building and automobile sectors. Among all available natural fibers, wood flour is one of the most abundantly available resources. Commodity plastics such as high-density polyethylene, low-density polyethylene, linear low-density polyethylene, and polypropylene, can be reinforced with wood flour, along with a compatibilizer and a coupling agent. A wide variety of compatibilizers and coupling agents are commercially available to cater to different needs. Under optimal conditions and compositions, they impart better mechanical, chemical, and thermal properties to the wood flour–reinforced plastic.

Particle-hopping models of vehicular traffic: Distributions of distance headways and distance between jams

We calculate the distribution of the distance headways (i.e., the instantaneous gap between successive vehicles) as well as the distribution of instantaneous distance between successive jams in the Nagel-Schreckenberg (NS) model of vehicular traffic. When the maximum allowed speed, Vmax, of the vehicles is larger than unity, over an intermediate range of densities of vehicles, our Monte Carlo (MC) data for the distance headway distribution exhibit two peaks, which indicate the coexistence of “free-flowing” traffic and traffic jams. Our analytical arguments clearly rule out the possibility of occurrence of more than one peak in the distribution of distance headways in the NS model when Vmax=1 as well as in the asymmetric simple exclusion process. Modifying and extending an earlier analytical approach for the NS model with Vmax=1, and introducing a novel transfer matrix technique, we also calculate the exact analytical expression for the distribution of distance between the jams in this model; the corresponding distributions for Vmax > 1 have been computed numerically through MC simulation.

Distributions of time- and distance-headways in the Nagel-Schreckenberg model of vehicular traffic: effects of hindrances

Abstract:In the Nagel-Schreckenberg model of vehicular traffic on single-lane highways vehicles are modelled as particles which hop forward from one site to another on a one dimensional lattice and the inter-particle interactions mimic the manner in which the real vehicles influence each others motion. In this model the number of empty lattice sites in front of a particle is taken to be a measure of the corresponding distance-headway (DH). The time-headway (TH) is defined as the time interval between the departures (or arrivals) of two successive particles recorded by a detector placed at a fixed position on the model highway. We investigate the effects of spatial inhomogeneities of the highway (static hindrances) on the DH and TH distributions in the steady-state of this model.

Effect of chemical modifications upon exchange capacity of aminated macroporous styrene–divinyl benzene (PS–DVB) copolymer anion exchange resin

The macroporous PS–DVB resin was prepared in the laboratory by suspension polymerization using gelatin as stabilizer and toluene as porogen. This is subsequently nitrated by a mixture of NO and NO2 (called NOx) in a gas phase reaction, and the carbon–nitrogen covalent bonding has been demonstrated by modified Laissagne spot test, FTIR, and ESCA analysis. This has been aminated by reducing the nitrate groups using hydrazine hydrate, and the resultant weak base anion exchange resin was shown to have a one-time exchange property because of its inability to be regenerated by the usual ASTM procedures. The chloroethylated PS–DVB resin is prepared by reacting aminated resin with dichloroethane, and is shown that two molecules of the latter react with every amine group. The regenerable strong-base anion exchange resin is then prepared by quarternizing it with tartiary (trimethyl and triethyl) amines and triphenyl phosphine, and it is shown that these gegen ions have a considerable effect on the exchange ability of the resin. We have found the duration of nitration to be the most important parameter affecting the capacity, and in this work, we report studies for all these gegen ions. It is found that for any gegen ion, the exchange capacity first increases for short times of nitration, reaches a broad maxima of around 5 mEq/g of wet resin with about 69% moisture content (or 15.48 mEq/dry g), and falls slightly for larger times of nitration due to a slight degradation. This is to be compared with commercial chloromethylated resin, which has an exchange capacity of 1.68 mEq/g of wet resin with 43.53% moisture content (or 2.97 mEq/dry g of resin). It is found that the resin with triphenyl phosphine as a gegen ion gives the highest exchange capacity, while the one with trimethyl gives the lowest. To assess the solvation ability of the chloroethylated resin prepared in this work, we evolved three stages of drying consistent with the literature such that in the first stage, unmodified resin loses moisture completely (shell 1 moisture), in the second stage, chloromethylated (commercial anion exchange) resin loses moisture completely (shell 2 moisture), and in the third stage chloroethylated resin loses moisture completely (shell 3 moisture). With the increase in the duration of nitration, the shell 1 and 2 moistures first increase, but after 5 h of nitration they fall to lower asymptotic values for a large duration of nitration. However, shell 3 moisture keeps on increasing and is the highest for triphenyl phosphine gegen ion and the lowest for trimethyl amine. This increased solvation ability of chloroethylated resin is likely to be responsible for higher exchange ability of the resin reported in this work.

Rice husk as reinforcing filler in polypropylene composites

Abstract Commodity plastics such as polypropylene can be reinforced with lignocellulosic materials such as rice husk, available in the environment in abundance. Bonding between the polymer and rice husk can be improved by proper selection of compatibilizer or coupling agents. Thermoplastic composites thus prepared have potential applications in automotive industries and as good building material.

Preparation of high capacity chloroethylated strong base anion exchange resin using NOx

Suspension polymerization of styrene and divinylbenzene has been carried out in the presence of gelatin as stabilizer to form macroporous polystyrene divinylbenzene resin (PS–DVB). In order to prepare surface chloroethylated macroporous PS–DVB resin, it is nitrated (resin 2) using a mixture of NO and NO2 gases (called NO x ), is reduced to amine groups (resin 3), further reacted with dichloroethane, then quarternized (resin 6) using trimethyl amine. Simple material balance demonstrates that all NO x reacted show up as exchanging sites of resin 6 and this resin has at least three exchanging sites on every repeat unit. We have examined the effect of duration of nitration on the exchange capacity of resin 6 and it was found that it first increased with increase in the duration of nitration, reaching a broad maxima of 4.8 meq/g of wet resin with 69% moisture (or capacity of 15.5 meq/g of dry resin) for about 5 hr of nitration and when nitration is continued for a longer time there is a fall due to polymer degradation. This is to be compared with the commercial chloride form of strong base anion exchange resin, which has the exchange capacity of 1.68 meq/g of wet resin with 43.53% moisture (or capacity of 2.97 meq/g of dry resin). In order to assess the solvation ability of the chloroethylated resin, we evolved a three-stage drying procedure and showed that it holds moisture differently. On a dry gram basis, the chloroethylated resin is about five times superior compared to available commercial resin.

Effect of chemical treatment on the mechanical and water absorption properties of bagasse fiber-reinforced epoxy composites

Abstract The present article presents a study on the mechanical and water absorption properties of bagasse fiber-reinforced epoxy composites. Bagasse fibers are subjected to chemical treatment with 1% sodium hydroxide followed by 1% acrylic acid at ambient temperature to enhance the bonding strength between the fiber-polymer, resulting in high values of the mechanical properties and a reduction in the water absorption properties of the composites. We analyzed the optimum value of fiber treatment, and it was found that 15% treated fiber loading yields enhanced the mechanical properties together with a reduction in water absorption properties.

Conversion of Glycerol into Value-Added Products Over Cu–Ni Catalyst Supported on γ-Al2O3 and Activated Carbon

Abstract A series of Cu, Ni monometallic and bimetallic catalysts supported on γ-Al2O3 and activated carbon were synthesized by incipient wetness impregnation method and examined for hydrogenolysis and esterification of glycerol. Hydrogenolysis reaction was carried out in a 250 ml Teflon-coated stainless steel batch reactor at 250°C and 10 bar H2 pressure, whereas esterification of glycerol with acetic acid was carried out at 120°C at atmospheric pressure. The physiochemical properties of the catalysts were investigated by various techniques such as surface area, X-ray diffraction (XRD), NH3-temperature-programmed desorption (TPD). Characterization results dictated that the reduction behavior, acidic nature and the metal support interactions were varied with the support as well as Cu/Ni weight ratio. The XRD results confirmed the formation of mixed oxide Cu0.75Ni0.25 Al2O4 phase in Cu–Ni (3:1)/γ-Al2O3 catalyst. Among the catalysts tested, Cu–Ni bimetallic catalysts showed superior performance as compared to monometallic catalysts in both the reactions. The glycerol hydrogenolysis activity of γ-Al2O3 supported Cu–Ni catalysts was higher than the activated carbon-supported catalysts. 1,2-PDO was obtained as the main hydrogenolysis product independent of the support as well as Cu/Ni weight ratio and its selectivity was in the range of 92.8–98.5%. The acidic nature of γ-Al2O3 and the mixed oxide (Cu0.75Ni0.25Al2O4) phase played an important role for hydrogenolysis activity. Cu–Ni (3:1)/γ-Al2O3 catalyst showed the maximum 1,2-PDO selectivity to 97% with 27% glycerol conversion after a reaction time of 5 h. On the other hand, Cu–Ni(1:3)/C catalyst showed the highest glycerol conversion of 97.4% for esterification and obtained selectivity to monoacetin, diacetin and triacetin were 26.1%, 67.2% and 6.5%, respectively.

Adsorption study of lead(II) onto xanthated date palm trunk: kinetics, isotherm and mechanism

AbstractThe adsorption of lead(II) onto xanthated date palm trunk (XDPT) from aqueous solutions was studied in a batch adsorption system. Factors influencing lead(II) adsorption such as initial Pb(II) concentration (25.8–207.0 mg/l), pH (1–6), contact time (5–240 min), and adsorbent dosage (0.625–6.0 g/l) were investigated. The adsorption process was relatively fast and equilibrium was established within 120 min. Maximum adsorption of Pb(II) occurred at pH ∼ 5. A comparison of the kinetic models on the overall adsorption rate showed that the adsorption system can be best described by the pseudo-second-order kinetics. The adsorption equilibrium data obeyed Langmuir isotherm and the monolayer adsorption capacity of Pb(II) was found to be 53.48 mg/g. The adsorption mechanism has been suggested to be due to the complexation of lead(II) ions with sulfur donors present in XDPT.

Adsorptive Removal of Hg(II) From Synthetic and Real Aqueous Solutions Using Modified Papaya Seed

The performance of chemically modified papaya seed (CMPS) adsorbent with carboxyl and amino groups has been studied. Adsorption experiments were performed with respect to the changes in initial pH of the solution, contact time, initial Hg(II) concentration, and CMPS dosage. Kinetic data were fitted to the pseudo-second-order model. The maximum adsorption capacity calculated by Langmuir model was 18.34 mg/g. CMPS was characterized by elemental analysis, Fourier transform infrared (FTIR) spectroscopy, and scanning electron microscopy. The results indicate that adsorption mechanism of CMPS involves ion exchange (2Na+/Hg2+) and carboxylic-group-dominated surface complexation. Regeneration study revealed that CMPS can be used successfully for four cycles with a small adsorption capacity loss (6.8%). GRAPHICAL ABSTRACT