摘要:

AbstractTwo separate assay systems were used to evaluate the biodegradation potential of cellulose acetate: anin vitroenrichment cultivation technique (closed batch system), and a system in which cellulose diacetate (CDA) films were suspended in a wastewater treatment system (open continuous feed system). Thein vitroassay employed a stable enrichment culture, which was initiated by inoculating a basal salts medium containing cellulose acetate with 5% (v/v) activated sludge. Microscopic examination revealed extensive degradation of CDA (DS = 2.5) fibers after 2–3 weeks of incubation. Characterization of the CA fibers recovered from inoculated flasks demonstrated a lower average degree of substitution and a change in the mol wt profiles.In vitroenrichments with CDA (DS = 1.7) films were able to degrade>80% of the films in 4–5 days. Cellulose acetate (DS = 2.5) films required 10–12 days for extensive degradation. Films prepared from cellulose triacetate remained essentially unchanged after 28 days in thein vitroassay. The wastewater treatment assay was less active than thein vitroenrichment system. For example, approximately 27 days were required for 70% degradation of CDA (DS = 1.7) films to occur while CDA (DS = 2.5) films required approximately 10 weeks before significant degradation was obtained. Supporting evidence for the biodegradation potential of cellulose acetate was obtained through the conversion of cellulose [1‐14C]‐acetate to14CO2in thein vitroassay. The results of this work demonstrate that cellulose acetate fibers and films are potentially biodegradable and that the rate of biodegradation is highly dependent on the degree of substitution. © 1993 John Wiley

ISSN:0021-8995    

DOI:10.1002/app.1993.070471001

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1993

数据来源: WILEY

摘要:

AbstractBulk anionic copolymerization of ε‐caprolactam (CPL) was conducted, under four different conditions by changing temperature (110 or 125°C) and [NCO]/[NaH]ratio (1, 2, or 3), in the presence of NCO‐terminated polypropylene glycol (P1) and its CPL‐blocked prepolymer (P2). Under the same conditions and reaction time, the conversion of CPL and reduced viscosity of the P2 system were higher than those of the P1 system. However, at the same conversion the P1 system showed higher viscosity for reactions at 125°C with [NCO]/[NaH]= 3 and at 110°C with [NCO]/[NaH]= 2. These results were attributed to cyclotrimerization of NCO groups of P1 (formation of isocyanurate) at the initial stage, which not only consumed the effective concentration of NCO but also increased the viscosity of the P1 system. Comparing IR spectra of the reaction products of model compounds, phenyl isocyanate and CPL‐blocked phenyl isocyanate, with NaH/CPL also supported this conclusion. The crystalline melting temperature (Tm= 198–208°C) and melting enthalpy of the final products depended on the conversion of CPL and the types of macroactivators. © 1993 John

ISSN:0021-8995    

DOI:10.1002/app.1993.070471002

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1993

数据来源: WILEY

摘要:

AbstractSisal fibers (Agave‐Veracruz) have been used as reinforcements in low‐density polyethylene (LDPE). The influence of the processing method and the effect of fiber content, fiber length, and orientation on tensile properties of the composites have been evaluated. The fiber damage that normally occurs during blending of fiber and polyethylene by the meltmixing method is avoided by adopting a solution‐mixing procedure. The tensile properties of the composites thus prepared show a gradual increase with fiber content. The properties also increased with fiber length, to a maximum at a fiber length of about 6 mm. Unidirectional alignment of the short fibers achieved by an extrusion process enhanced the tensile strength and modulus of the composites along the axis of fiber alignment by more than twofold compared to randomly oriented fiber composites. © 1993 John Wiley&Son

ISSN:0021-8995    

DOI:10.1002/app.1993.070471003

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1993

数据来源: WILEY

摘要:

AbstractThe migration of compounds from polymer‐based packaging may impart undesirable odors to foods. We, therefore, undertook a study of the volatile compounds produced during the heating of polyethylene (PE) in the presence of excess O2at temperatures of 150–350°C and for heating times of 5–15 min. Eightyfour volatile compounds in the range of C5—C23were identified by gas chromatography mass spectrometry. The major products were aliphatic hydrocarbons, aldehydes, ketones, and olefins. Changes in temperature and heating times affected the amount and type of compounds produced, with hexanal being found in the largest amount and 300°C resulting in the greatest quantity of volatile compounds. At 350°C, greater amounts and numbers of low‐boiling and fewer high‐boiling compounds were formed. Only small amounts of volatiles were produced at 150°C. Many of the compounds identified have been reported to have odor and/or toxicological significance. © 1993 John

ISSN:0021-8995    

DOI:10.1002/app.1993.070471004

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1993

数据来源: WILEY

摘要:

AbstractThe effect of diethylene glycol (DEG) on the crystallization of poly(ethylene terephthalate) (PET) was studied under isothermal and dynamic conditions. The strain‐induced crystallization of PET and its relationship to DEG content was also studied. The samples were isothermally and dynamically crystallized in the differential scanning calorimeter (DSC). The thermograms were then analyzed to determine the kinetic parameters. Strain‐induced crystallization was studied by stretching samples at different strain rates. These samples were then annealed for various periods of time and quenched to room temperature. Birefringence and density were measured on the annealed samples. Results indicate that the DEG content reduces the rate of crystallization of PET when crystallizing from the melt, isothermally and dynamically. When crystallizing from the glassy state, the effects of DEG are not prominent. The mechanism of crystallization is not affected by the amount of DEG, within the range of DEG contents evaluated. In the case of strain‐induced crystallization, increased DEG content reduces the crystallinity of PET at intermediate strain rates, but at higher strain rates, the crystallinity is not affected by the DEG content. © 1993 John Wiley&Son

ISSN:0021-8995    

DOI:10.1002/app.1993.070471005

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1993

数据来源: WILEY

摘要:

AbstractStarch‐g‐poly(methyl acrylate) (S‐g‐PMA) copolymers containing 55–60% PMA were prepared from cornstarch, high amylose cornstarch, and waxy cornstarch with ceric ammonium nitrate initiation. Graft copolymers were characterized with respect to % PMA homopolymer, % conversion of monomer to polymer, grafted PMA content, grafting frequency, and the molecular weight and molecular weight distributions of PMA grafts. Variables investigated in the graft copolymerization reaction were nitric acid concentration, ceric ion‐to‐starch ratio, reaction time, gelatinization of the starch, and reactant concentration in water. At high reactant concentrations, high conversions of methyl acrylate to grafted PMA could be obtained in less than 0.5 h at 25°C. © 1993 John

ISSN:0021-8995    

DOI:10.1002/app.1993.070471006

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1993

数据来源: WILEY

摘要:

AbstractUltrasmall CdS particles, whose average size was controlled by thiols to range from 2 to 4 nm, were embedded in poly(vinyl alcohol) films. Shift of the fluorescence peak associates with the shift of the absorption threshold of the films, and the fluorescence intensity increases with the decrease in the size of CdS. Laser ablation at 308 nm was investigated by monitoring the emission spectra. Third‐harmonic generation was measured for various sizes of CdS particles, and the optical nonlinearity in the nonresonance region was found to remain almost constant in the diameter range studied. © 1993 John Wiley&Sons, I

ISSN:0021-8995    

DOI:10.1002/app.1993.070471007

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1993

数据来源: WILEY

摘要:

AbstractThe Curie transition, even though the conformational change at the Curie transition primarily arises from intermolecular interaction, is highly dependent on the crystallization conditions. A slower cooling rate from the melt during paraelectric crystallization lowersTc, increases the portion ofFβat the expense ofFαreduction, and produces a more unstable ferroelectric phase.T ↓cis rarely dependent upon the amount of PMMA, butT ↑cis increased with the PMMA content. PMMA has a favorable action in forming a more stable ferroelectric phase in the P(VDF/TrFE)/PMMA blend and elevating the Curie transition point because of the all‐transsequence conformation of PMMA and a specific intermolecular interaction with P(VDF/TrFE) in the melt state. However, PMMA reduces the total amount of the crystalline phase, the electric response, and the piezoelectricity. © 1993 John Wil

ISSN:0021-8995    

DOI:10.1002/app.1993.070471008

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1993

数据来源: WILEY

摘要:

AbstractCyclohexanone oxime‐blocked isophorone diisocyanate and cyclohexanone oxime‐blocked toluene diisocyanate were synthesized and analyzed by infrared spectra, nuclear magnetic resonance spectra, elemental analysis, etc. Decomposition temperatures of the blocked isocyanates were determined by thermogravimetry. The solubilities of blocked isocyanates in various polyols were tested. © 1993 John Wiley&Sons,

ISSN:0021-8995    

DOI:10.1002/app.1993.070471009

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1993

数据来源: WILEY

摘要:

AbstractFilms from 96% quinoline and from 96% quinoline with poly(1,4‐cyclohexylene carbonate), mesoporphyrin IX dimethyl ester, and Pd(II)mesoporphyrin IX dimethyl ester have been cast via heating and subsequent evaporation. The films are approximately 3 μm thick, with a maximum variation normal to the surface of 0.10 μm in 2 mm of surface travel. The optical quality of the samples formed from 96% quinoline alone is excellent and variable from the 96% quinoline/solute combinations. The third‐order nonlinear optical (NLO) properties of these materials have been examined. © 1993 John Wiley&Son

ISSN:0021-8995    

DOI:10.1002/app.1993.070471010

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1993

数据来源: WILEY