摘要:

Gamma rays from60Co were used to graft chloromethylstyrene on samples of polysilicone, followed by quaternization with pyridine, then reaction with sodium heparin to replace chloride ions in the samples with heparin anions. Extraction tests on the heparinized samples with normal saline solution showed a maximum heparin removal rate of 5 × 10−-8g/cm2/min. The heparinized polysilicone was found to be more blood compatible than untreated polysilicone in a rabbit ex vivo bleeding test.

ISSN:0022-233X    

DOI:10.1080/00222338108056824

出版商:Taylor & Francis Group    

年代:1981

数据来源: Taylor

摘要:

Poly(viny1 chloride) (PVC) was dehydrochlorinated thermally in pyridine solution under N2atmosphere and the effect of variation of reaction time, temperature, and concentration of PVC in pyridine was studied. The extent of dehydrochlorination (or conversion, x%) increases with an increase in reaction time and temperature, and with a decrease in the concentration of PVC. Incomplete precipitation of dehydrochlorinated PVC (DHPVC) occurs by nonsolvent (methanol). During dehydrochlorination there is no HCl evolution as it forms a pyridine hydrochloride complex which is supposed to act as a catalyst for dehydrochlorination. A possible mechanism has been proposed. Chain scission and cross-linking reactions are responsible for the molecular weight changes that take place during the reaction.

ISSN:0022-233X    

DOI:10.1080/00222338108056825

出版商:Taylor & Francis Group    

年代:1981

数据来源: Taylor

摘要:

Polystyrene resins having pendant nucleic acid bases were prepared. They were found suitable for high performance liquid chromatography to separate N-substituted nucleic acid bases effectively. From the measurements of retention times and peak resolution values, it became evident that the specific base-base interaction between the solutes and the resin plays an important role in the separation purpose.

ISSN:0022-233X    

DOI:10.1080/00222338108056826

出版商:Taylor & Francis Group    

年代:1981

数据来源: Taylor

摘要:

Radiation-induced wood-polymer composites have been prepared using some tropical commercial woods. These included Kapur (Dryobalanop sp.), Kempas (Koompassia sp.), Red Seraya (Shorea sp.), White Seraya (Parashorea sp.), and Jelutong (Dyera sp.). The wood specimens were modified by impregnation with monomers and followed by exposure to gamma radiation. Monomer systems used were methyl methacrylate, methyl methacrylate with 5% dioxane, acrylonitrile, 60:40 styrene-acrylonitrile comonomer, vinyl acetate, and vinylidene chloride. The resulting composite specimens exhibited significant increases in hardness and compressive strength, the extent of which appeared to depend on the amount and type of polymer present. Dimensional stability increased when the woods were impregnated with polymethyl methacrylate and improved further to about 35% on addition of a swelling agent, dioxane. Wood-polyvinylidene chloride composites gave high fire resistance as opposed to wood-polymethyl methacrylate which showed increased flammability. A 4-fold decrease in weight loss was observed in the fire-tube and crib tests conducted. The impregnated polymers were not totally resistant to termites. The polymers, not being nutrients, reduced the number of survivals after a 90-d test period. Polystyrene-acrylonitrile appeared toxic to the termites.

ISSN:0022-233X    

DOI:10.1080/00222338108056827

出版商:Taylor & Francis Group    

年代:1981

数据来源: Taylor

摘要:

Microencapsulation is a technique of enclosing a core material into a polymeric membrane such that the encapsulate may be released over a period of time by diffusion or spontaneously on collapsing the wall by a sudden pressure. Besides being used in the dyes, foodstuffs, and chemical industries, such a technique has also found applications in biomedicine for prolonged drug delivery. The present work discusses the possible use of cellulose acetate as an encapsulating material giving microcapsules for sustained drug delivery. The conditions of formation of such capsules containing testosterone as the drug, and its subsequent release from depots, are described. Scanning electron micrographs of these show formation of good, nearly spherical capsules in the range of 5–100 μm. The release of testosterone from the microcapsules sustains up to 35 d. Possible use of this system in medical applications is discussed.

ISSN:0022-233X    

DOI:10.1080/00222338108056828

出版商:Taylor & Francis Group    

年代:1981

数据来源: Taylor

摘要:

Graft copolymerization of methyl methacrylate onto wool induced by the permanganate-oxalic acid redox system was investigated in aqueous medium. The rate of grafting was determined by varying the concentrations of monomer, oxalic acid, permanganate, acidity of the medium, temperature, and the reaction medium. The graft yield increases significantly with increasing oxalic acid concentration up to 1.5 × 10−-2M and thereafter it decreases. The graft yield also increases wTth an increase of the monomer concentration, initiator concentration, acid concentration, and temperature up to a certain range and then decreases. The effect of some inorganic salts and surfactants on the rate of grafting has also been investigated and a suitable reaction mechanism has been proposed.

ISSN:0022-233X    

DOI:10.1080/00222338108056829

出版商:Taylor & Francis Group    

年代:1981

数据来源: Taylor

摘要:

Graft copolymerization of methyl methacrylate onto wool was investigated in aqueous solution using the potassium peroxy-diphosphate-thiourea redox system as the initiator. The rate of grafting was determined by varying the monomer, peroxydi-phosphate ion, temperature, and solvent. The graft yield increases with increasing peroxydiphosphate ion up to 80 × 10−-4mol/L, and with further increase of peroxydiphosphate ion the graft yield decreases. The graft yield increases with increasing monomer concentration. The percentage of grafting decreases with increasing thiourea concentration. The rate of grafting increases with an increase of temperature. The effect of acid and water-soluble solvent and certain salts on graft yield has been investigated and a suitable rate expression has been derived.

ISSN:0022-233X    

DOI:10.1080/00222338108056830

出版商:Taylor & Francis Group    

年代:1981

数据来源: Taylor

摘要:

The stability constants of ternary Co(II) or Ni(II) complexes containing 2,2′-bipyridyl (bipy) or 1,10-phenanthroline (phen) as primary ligand and N-phenyl 2-mercaptoacid amide (PMA), N-(p-chloro)phenyl-2-mercaptoacid amide (CPMA), N-(p-toly1)-2-mercaptoacid amide (TMA) or N-(p-anisyl)-2-mercaptoacid amide (AMA) as secondary ligand were determined in 70% (v/v) dioxane-water medium at 30 ± 1°C and 0.1M(NaC1O4) ionic strength in a nitrogen atmosphere. A study Tf Co(II) or Ni(II) in the presence of an equimolar concentration of the two ligands showed the formation of mixed ligand complexes containing a 1:1:1 molar ratio of metal and the two ligands. These ternary complexes are more stable than would be expected on a statistical basis, i.e., the difference, Δ log KM= log KMAMAL- log KMML, is positive (A = bipy or phen, L = secondary ligand). Further results suggest that both the ligands are incompatible toward the metal ions and hence the mixed-ligand complexes formed are relatively more stable.

ISSN:0022-233X    

DOI:10.1080/00222338108056831

出版商:Taylor & Francis Group    

年代:1981

数据来源: Taylor

摘要:

The reaction of diaminotetraalkoxy- and aryloxycyclotriphos-phazene with toluendiisocyanate (TDI) was investigated in various solvents. It was found that benzene or electron negative groups such as the trifluoroethoxy group (-OCH2CF3) were the most suitable solvents for the growing of molecules having an N3P3ring. The adhesive property of the products to a hard polyvinyl chloride laminate was studied by bonding strength measurements. The product formed from the reaction of diaminotetramethoxy-cyclotriphosphazene with TDI had the strongest adhesive strength even though it had the low molecular weight.

ISSN:0022-233X    

DOI:10.1080/00222338108056832

出版商:Taylor & Francis Group    

年代:1981

数据来源: Taylor

摘要:

The condensation reaction of α-naphthylisocyanate with n-butanol has been studied in toluene and in bis(2-methoxyethyl) ether (diglyme) by IR spectroscopy at different temperatures (20–60°C). A kinetic study shows that it is first order with respect to each reactant even when the reaction is catalyzed by tin octoate. A general mathematical treatment indicates that secondary reactions may occur in some conditions of temperature, solvent and catalyst, but do not take place in our system. The activation enthalpy and entropy have been determined.

ISSN:0022-233X    

DOI:10.1080/00222338108056833

出版商:Taylor & Francis Group    

年代:1981

数据来源: Taylor