bluuebunny/crossref_metadata_2025_split huggingface dataset:
Blends of poly(vinyl acetate) and poly(ethyl methacrylate): Some mechanical properties
Authors: Olayemi J. Y. , Ibiyeye M. K. 
Published: April 2003

AbstractPoly(vinyl acetate) (PVAc) and poly(ethyl methacrylate) (PEMA) were solution blended in chloroform and cast into films on mercury surface. Some mechanical properties of the films were studied with the Instron Testing Machine. Tensile strength (TS), initial modulus (IM) and elongation at break of the films were found to depend highly on blend composition, and increased above the values for the pure polymers, each showing a peak at about 20% PEMA. The peak values of TS, IM, and elongation at break depended on an important factor, (Mv)rc the ratio of the molecular weights of (PEMA) to (PVAc). Improvements to the mechanical properties of the polymers due to blending were considered to be as a result of the presence of favorable and strong (PVAc‐PEMA) intermolecular interactions which reveal miscibility and compatibility of the polymers. A lower critical value (Mv)rc of 4.9 was found, above which no phase separation would be expected on blending these two polymers to the extent of 20% by weight of PEMA.
Moisture regain and dyeability of poly(acrylic acid)‐ and poly(styrene)‐carbamoylethylated cotton graft copolymers induced by gamma radiation
Authors: Hebeish A. , Zahran A. H. , El‐Naggar A. M. K. , Rabie A. M. 
Published: April 2003

AbstractGamma radiation‐induced graft copolymerization of either acrylic acid or styrene onto untreated cotton, alkali‐treated cotton, and carbamoylethylated cottons having 0.392% N, 0.524% N, 0.725% N, 1.379% and 1.546% N was investigated under different conditions. Moisture regain and dyeability of these substrates before and after copolymerization were also examined. It was found that the graft yield increases by increasing monomer concentration and radiation dose irrespective of the monomer or substrate used. Using water‐ethanol mixtures as polymerization media are advantageous for grafting of styrene. With both monomers, however, the graft yield for the modified cottons are substantially higher than untreated and alkali‐treated cottons, indicating that the presence of carbamoylethyl in the molecular structure of cotton cellulose affords additional sites for graft copolymerization. Copolymers obtained using acrylic acid show much higher moisture regain that the ungrafted substrates, particularly when the carboxylic groups of the graft were in the sodium form. The opposite holds true for copolymers brought about by grafting with styrene. The color strength of all substrates dyed with a direct or a reactive dye decreases significantly after copolymerization with poly(acrylic acid) prior to dyeing. On the other hand, this copolymerization improves the affinity of the substrates for the basic dye and brings about perceptible shade. Copolymerization of the substrates in question with poly(styrene) improves the color strength of these substrates when dyed with direct, disperse, and basic dyes but decreases the color strength upon dyeing with a reactive dye.
New aspects in cationization of lignocellulose materials. III. Influence of delignification on reactivity and extractability of TMAHP–hemicelluloses
Authors: Ebringerová Anna , Antal Miroslav , Šimkovic Ivan , Micko Michael M. 
Published: April 2003

AbstractBeech sawdust samples with different lignin content were alkylated with 3‐chloro‐2‐hydroxypropyltrimethylammoniumchloride (CHMAC). The yields and the degree of subtitution of trimethylammonium‐2‐hydroxypropyl (TMAHP) samples were similar. Differences were found in extractability of hemicelluloses from this materials both with water and dilute alkali. To obtain the maximum yield of TMAHP–hemicelluloses (ca. 90% of the amount originally present), it is sufficient to remove about 50% of lignin. The lignin component does not influence the reactivity of hemicelluloses. The isolated hemicelluloses differ only in the distribution of functional groups and extractability.
Rheological studies of ultraviolet curing with an oscillating plate rheometer
Authors: Otsubo Yasufumi , Amari Takeshi , Watanabe Koichiro 
Published: April 2003

AbstractThe dynamic viscoelastic behavior during UV curing was studied for thin liquid films of epoxy acrylate prepolymer by the use of an oscillating plate rheometer. The dynamic viscosity rapidly increases after a certain period of irradiation, so that the UV curing process has the minimum exposure energy required to start polymerization. The minimum exposure energy markedly increases with increasing sample thickness; this results from the inconsistency of degree of curing in the direction perpendicular to the shearing surface. Since free radicals which initiate polymerization are formed by photochemical decomposition of initiator, the ability to cure a film depends on the light intensity at a given depth of the film. the attenuation of light in the film is primarily responsible for this inconsistency. When UV light is applied through a UV filter, the curing behavior is analyzed by a single exponential decay of light with depth because the curing is induced by absorption of a monochromatic light of 365 nm. On the other hand, when UV light from a UV lamp whose output spectrum is a continuum is directly applied, the curing behavior is explained by a combination of energy absorption at different wavelengths. In both cases, the theoretical curves of dynamic viscosity predicted in relation to spectral sensitivity show a good agreement with the experimental results.
Structural differences exhibited by networks prepared by chemical and photochemical reactions IV chemical relaxation
Authors: Haidar B. , Vidal A. , Donnet J. B. 
Published: April 2003

AbstractChemical stress relaxation has been used for the characterization of elastomeric networks obtained either by peroxide curing or by photocrosslinking. It has been shown that the differences observed between photocrosslinked and peroxide‐cured elastomers are not limited to their structure and physical properties but are also due to the very nature of the created bonds.