摘要:

AbstractA new type of complex reservoir–matrix system for the controlled delivery of diltiazen hydrochloride was developed. This capsule‐type device was designed for oral administration to humans and/or animals. It contained (i) an appropriate amount of the drug in a compartment; (ii) a swelling‐controlled membrane which was prepared by mixing polymeric materials with another appropriate amount of the drug; and (iii) a water‐soluble gelatin capsule as container. The swelling‐controlled membranes were prepared from poly(2‐hydroxyethyl methacrylate) hydrogels. The effect of pH on the swelling of the hydrogels was studied.In‐vitrodissolution testing was carried out to evaluate the release of the drug using a continuous‐flow method. Zero‐order release kinetics was obtained over

ISSN:0959-8103    

DOI:10.1002/pi.1995.210380401

出版商:John Wiley&Sons, Ltd.    

年代:1995

数据来源: WILEY

摘要:

AbstractAn investigation was undertaken regarding the adsorption of heavy metal ions (CrO2−4or Pb2+) and phenol from solution with a highly crosslinked amphoteric starch containing the phosphate anionic group and the tertiary amine cationic group. The adsorption process was found to be dependent on initial pH and concentration for both metal ions, and to be concentration‐independent for the phenol organic substance. The adsorption follows the Langmuir adsorption isotherm for CrO2−4, and the Freundlich adsorption isotherm for Pb2+. The adsorption mechanism confirms that the Na+of the sodium phosphate group and the Cl−of the tertiary amine group are used to exchange Pb2+and CrO2−4ions, respectively, and the tertiary amine group is used to adso

ISSN:0959-8103    

DOI:10.1002/pi.1995.210380402

出版商:John Wiley&Sons, Ltd.    

年代:1995

数据来源: WILEY

摘要:

AbstractThe dissociation mechanism suggested for lithium‐based polymerization in many cases requires a relationships between the degree of association of the active centres and the kinetic data. This connection has recently been questioned (R. N. Young, L. J. Fetters, J. S. Huang&R. Krishnamoorti,Polymer International,33(1994) 217). It is the purpose of the present communication to show that this questioning is not soundly base

ISSN:0959-8103    

DOI:10.1002/pi.1995.210380403

出版商:John Wiley&Sons, Ltd.    

年代:1995

数据来源: WILEY

摘要:

AbstractA dicarboxylic acid (1) bearing two phthalimide rings was prepared by the condensation ofN‐phenyl‐3,3‐bis[4‐(4‐aminophenoxy)phenyl]phthalimidine and trimellitic anhydride. A new family of poly(amide–imide)s having inherent viscosities of 0.65–1.65 dl/g was prepared by the triphenyl phosphite activated polycondensation of the diimide–diacid1with various aromatic diamines in a medium consisting ofN‐methyl‐2‐pyrrolidone (NMP), pyridine, and calcium chloride. All the resulting polymers showed an amorphous nature and were readily soluble in polar solvents such as NMP andN,N‐dimethylacetamide. The soluble poly(amide–imide)s afforded transparent, flexible, and tough films. The glass transition temperatures of these polymers were in the range 249–340°C and the 10% weight loss temperatures

ISSN:0959-8103    

DOI:10.1002/pi.1995.210380404

出版商:John Wiley&Sons, Ltd.    

年代:1995

数据来源: WILEY

摘要:

AbstractHybrid modifiers composed ofN‐phenylmaleimide–styrene copolymers (PMS), andN‐phenylmaleimide–styrene–p‐hydroxystyrene terpolymers (PMSH) containing pendentp‐hydroxyphenyl groups as functionalities, were used to improve the toughness of bisphenol‐A diglycidyl ether epoxy resin cured withp,p′‐diaminodiphenyl sulphone. The hybrid modifiers were effective in toughening the epoxy resin. When using the modifier composed of 10 wt% PMS (M̄w313000) and 2.5 wt% PMSH (2.5 mol%p‐hydroxystyrene units,M̄w316000), the fracture toughness (KIC) for the modified resins increased 100% with no deterioration in the flexural properties and the glass transition temperature. The improvement in toughness of the epoxy resins was attained because of the co‐continuous phase structure and the improvement in interfacial adhesion. The toughening mechanism is discussed in terms of the morphological characteristics of the mod

ISSN:0959-8103    

DOI:10.1002/pi.1995.210380405

出版商:John Wiley&Sons, Ltd.    

年代:1995

数据来源: WILEY

摘要:

AbstractTimes to gelation and times to vitrification during isothermal curing for the epoxy system diglycidyl ether of bisphenol A and 1,3‐bisaminomethyl‐cyclohexane were measured at different curing temperatures between 50 and 100°C. Gelation occurs around 56% conversion. Vitrification was determined from data curves of glass transition temperature,Tg, versus curing time obtained from DSC experiments. The minimum and maximumTgdetermined for this epoxy system wereTgo= −37°C andTg∞= 150°C. Values of activation energy of the epoxy/amine cure reaction of 58 kJ/mol and 49.5 kJ/mol were obtained fromTgversus time shift factors and gel time measurements respectively. The isothermal time–temperature–transformation diagram has be

ISSN:0959-8103    

DOI:10.1002/pi.1995.210380406

出版商:John Wiley&Sons, Ltd.    

年代:1995

数据来源: WILEY

摘要:

AbstractA series of polyether–copolyester segmented copolymers ((PBT–PET)PTMG) based on hard segments of tetramethylene terephthalate–ethylene terephthalate copolyester (PBT–PET) and soft segments of poly(tetramethylene ether)(PTMG) was synthesized. The hard : soft segment weight ratio was 30 : 70 and the mole ratio of PBT : PET was 1 : 10; 1 : 6; 1 : 1; 3 : 1, respectively. Their mechanical properties, morphology, crystallization behavior and optical transparency were investigated and compared with poly(tetramethylene terephthalate)–poly(tetramethylene ether)(PBT–PTMG), as well as with poly(ethylene terephthalate)–poly(tetramethylene ether)(PET–PTMG), consisting of the equivalent composition ratio of hard and soft segments. It was found that the transparency could be improved by introducing a small amount of PBT into PET–PTMG through copolymerization. However, a decrease was observed in the transparency if more PBT was added. This is due to the fact that the copolymerization makes both crystallinity and crystallizat

ISSN:0959-8103    

DOI:10.1002/pi.1995.210380407

出版商:John Wiley&Sons, Ltd.    

年代:1995

数据来源: WILEY

摘要:

AbstractPolymerization of non‐conjugated divinyl monomerN,N′‐methylene bisacrylamide was studied with a novel redox pair of manganese (VII)–thiol in a homogeneous gel‐free state, under varying conditions of concentration, temperature, pH and ionic strength, and the kinetic results were interpreted by a suitable mechanistic sequence from among various possibilities. Absence of gelation is attributed to the formation of a cyclic polymer. An attempt is made to correlate the structure of the reductant–oxidant complex with the observed kine

ISSN:0959-8103    

DOI:10.1002/pi.1995.210380408

出版商:John Wiley&Sons, Ltd.    

年代:1995

数据来源: WILEY

摘要:

AbstractThe influence of annealing conditions on the morphology and melting behaviour of poly(ethylene terephthalate) (PET) was studied. PET annealed under isothermal conditions often shows double melting endotherms depending on the annealing temperature (Ta) and the heating rate of the calorimeter. It was found that the morphological structure and the lower melting peak depend strongly on the annealing temperature,Ta. The increase of the lower melting peak temperature withTais due to an increase of the lamellar thickness within the spherulitic structure and to a higher crystallite perfection.

ISSN:0959-8103    

DOI:10.1002/pi.1995.210380409

出版商:John Wiley&Sons, Ltd.    

年代:1995

数据来源: WILEY

摘要:

AbstractA detailed description of the morphology and the complex melting behaviour of poly(butylene terephthalate) (PBT) annealed in the range 80–228°C is presented. Double melting endotherms can be obtained by annealing PBT in a differential scanning calorimeter (DSC). The lower endotherm corresponds to the melting of crystalline material formed at the annealing temperature in addition to some of the crystallized material reorganized during the quenching process. The upper melting endotherm results from the melting of a fraction of the original crystalline material reorganized during the DSC scan. Electron microscopy showed that the spherulitic structure over a wide range of annealing temperature below the melting point is unchanged. At high annealing temperatures, such as 228°C, electron micrographs showed that the narrow high melting peak is associated with the melting of isolated single crystals grown at that temperat

ISSN:0959-8103    

DOI:10.1002/pi.1995.210380410

出版商:John Wiley&Sons, Ltd.    

年代:1995

数据来源: WILEY