Soxhelt Extraction Research Articles

Polymer–montmorillonite nanocomposites: Chemical grafting of polyvinyl acetate onto Cloisite 20A

AbstractThis paper is an account of the experiments on grafting polyvinyl acetate onto organophilic montmorillonite. Cloisite 20A was reacted with vinyltrichlorosilane to replace the edge hydroxyl groups of the clay with a vinyl moiety. Because the reaction liberates HCl, it was performed in the presence of sodium hydrogencarbonate to prevent the exchange of quaternary alkylammonium cations with H+ ions. Only the silanol groups on the edge of the clay react with vinyltrichlorosilane. After the reaction, the product maintained the same basal spacing as the precursor. The radical polymerization of the product with vinyl acetate as a vinyl monomer leads to chemical grafting of polyvinyl acetate onto montmorillonite surface. The homopolymer formed during polymerization was separated from the grafted organoclay by Soxhelt extraction. Chemical grafting of the polymer onto Cloisite 20A was confirmed by infrared spectroscopy. The prepared nanocomposite materials and the grafted nano‐particles were studied by XRD, SEM, and TEM. Exfoliated nanocomposite was obtained for 0.5% clay content. Nanocomposites with 1% and 3% clay contents showed significant intercalation and agglomeration occurred at higher clay loadings. The nanocomposites were studied by thermogravimertic analysis (TGA) and dynamic mechanical analysis (DMTA). Improved thermo‐mechanical properties were observed for nanocomposite with 0.5% clay content. POLYM. COMPOS., © 2011 Society of Plastics Engineers.

PMMA-clay nanocomposite materials: Free-radically grafting of PMMA onto organophilic montmorillonite (20A)

This paper reports the grafting of poly(methyl methacrylate) (PMMA) onto organophilic montmorillonite (Cloisite 20). Cloisite 20A was reacted with vinyltrichlorosilane to replace the edge hydroxyl groups of the clay with a vinyl moiety. Under the reaction condition, the exchange of quaternary alkylammonium cations with H+ ions was prevented and only the silanol groups on the edge of the clay reacted with vinyltrichlorosilane. The radical polymerization of the product with methyl methacrylate as a vinyl monomer led to the chemical grafting of PMMA onto the montmorillonite surface. Chemical grafting of the polymer onto Cloisite 20A was confirmed by Infrared (IR) spectroscopy after Soxhelt extraction. The interlayer and surface changes to the clay in the prepared nanocomposite materials and the grafted nano-particles were examined by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The intercalated nanocomposites were obtained for clay contents up to 5%. The nanocomposites were examined by thermogravimetric analysis (TGA) and dynamic mechanical analysis (DMTA). Nanocomposites exhibit a higher glass transition temperature and improved thermal properties than neat PMMA due to an interaction between the PMMA matrix and PMMA-grafted clay particles.

Minimum Amount of Binder Removal Required during Solvent Debinding of Powder-Injection-Molded Compacts

Unsatisfactory dimensional control, distortion, and defects are frequently observed in powder-injection-molded parts, particularly after the solvent and thermal-debinding processing steps. One of the reasons is that the amount of soluble binder removed during the first step, solvent debinding, is not great enough to form interconnected pores throughout the compact, particularly in the core region. Thus, blistering, cracking, and bubbles can form easily during the subsequent thermal debinding. To determine the minimum debinding fraction required for solvent debinding, at which point interconnected pore channels are formed at the center, modeling of the distribution of the remaining soluble binder in the compact was established. The actual distribution, which was obtained by measuring the binder content layer by layer with the soxhelt extraction method, is in good agreement with the model. The modeling, bubble test, and fluorescence dye-penetration analysis show that, regardless of the compact thickness, the minimum bulk debinding fraction needed is consistently approximately 59 pct, yielding a local debinding fraction of 37 pct and a porosity of 8.5 pct at the center. This porosity is close to the value at which pores in a sintered compact transform from open to closed at the beginning of the final stage of sintering.

DDT residue in soil and water in and around abandoned DDT manufacturing factory

Dichlorodiphenyltrichloroethane (DDT) belongs to one of the most hazardous groups of chemicals called persistent organic pollutants. Many organochlorine pesticides including p,p(')-DDT are long lasting due to their non-degradability can travel to distant places and being fat soluble can accumulate in animals and human bodies. Due to the persistent nature of p,p(')-DDT, its adverse environmental and health impacts, the present study was undertaken to examine the residual p,p(')-DDT in and around abandoned p,p(')-DDT manufacturing factory in Amman Gharh, Nowshera, NWFP. Samples of soil, sediments and water were collected in and around the factory area, nearby p,p(')-DDT stores, main factory drain leading to river Kabul and nearby villages. Standard procedures were used for the collection, transportation and storage of samples for analyses. Extraction of each sample for p,p(')-DDT analyses was carried out in triplicates using Soxhelt extraction. p,p(')-DDT contents in the samples were analyzed by capillary GC with electron capture detector. Most of the samples collected up to half kilometer distance from the site of the DDT factory were found contaminated. Further the level of p,p(')-DDT decreased with increasing depth from top to bottom and with distance from the site. The results indicate that there is no immediate threat to underground water reservoirs.

Evaluation of antibacterial activity of different mangrove plant extracts

Antibacterial activity of mature leaves, tender leaves and bark extracts of Avicennia marina, Avicennia officinalis and Bruguiera sexangula were evaluated using Soxhelt extraction method. Petroleum ether, chloroform, ethyl acetate and ethanol were used as solvents in order to get the plant extracts. The antibacterial activity was screened by using agar diffusion technique against pathogenic bacteria species of Staphylococcus sp. (from urine), Proteus sp. (from a wound), Escherichia coli (from infected blood), Shigella sp. (from a wound) and Pseudomonas sp. (from a wound). The length of inhibition zone was measured in millimeters from the edge of the well to the edge of the inhibition zone. Twelve different plant extracts in A. marina, A. officinalis and B. sexangula exhibited different degree of growth inhibition against tested bacterial strains. Mature leaf extracts of A. marina and tender leaf extracts of A. officinalis in ethyl acetate exhibited promising antibacterial activity than other plant extracts. All plant extracts in ethyl acetate showed strong inhibition compared to other extracts on all tested bacterial strains. Among all bacterial strains, Pseudomonas sp. and E. coli showed considerable growth inhibition against almost all plant extracts. Mature leaf extract of only A. marina was used for further investigations since a large amount of tender leaves of A. officinalis was not readily available. Charcoal treated mature leaf extracts of A. marina showed more inhibition for all tested bacterial strains than untreated plant extracts. Combinations of mature leaf extracts of A. marina in different solvents failed to exhibit synergistic activity against tested bacterial strains. Most combinations showed antagonistic effect against Proteus sp., E. coli and Shigella sp. Antibacterial activity of plant extracts of A. marina gradually declined during 4 months after extraction, for all tested bacterial strains. Components of mature leaf extracts of A. marina in chloroform, ethyl acetate and ethanol were separated by Analytical Thin Layer Chromatography (ATLC) when the eluents were hexane and diethyl ether. Isolated components in Preparative Thin Layer Chromatography (PTLC) exhibited moderate antibacterial activity against Pseudomonas sp., Shigella sp. and E. coli. Separated components did not show any antibacterial activity against Proteus sp. and Staphylococcus sp. Phytochemical screening revealed that mature leaf of A. marina contained alkaloids, steroids, triterpenoids and flavonoids.

A new approach of coke characterization on metal and support for Pt/Al 2O 3 by combination of Al 2O 3 and Pt/SiO 2

The main goal was to study the distribution and probability of chain growth of coke by the combination of Pt/SiO 2 representing the metal sites with 100–120 mesh mixed with Al 2O 3 60–80 mesh representing the acid sites. TPO, ESR, IR and Soxhelt extraction analyzed with GC-14B were employed for coke characterization. From the effects of time, temperature, H 2/HC ratio and modification of catalysts, it was found that probability of chain growth on both sites were the same. However, the greater accumulation was occurred on the support. This offered transformation on the gas phase of coke intermediates from the metal, which was primarily responsible for producing the coke precursors. The roles H 2 and promoter was more sensitive to reduce coke and probability of chain coke, especially the effect of K promoter.