Two samples of gum supposedly obtained from Sapotaceae achras and named "sapote gum" were studied using the methods of partition chromatography. The two samples were proven to be entirely different in composition and to constitute in fact two separate and distinct gums. The previously unreported gum was characterized and shown to contain D-xylose, L-arabinose, D-galactose, and one or more glucuronic acids, including some methoxy-glucuronic acid. A new spray reagent was developed for paper chromatography of the sugars, and a novel technique used for making permanent photographic prints of the papergrams. Crystalline sugars were obtained from hydrolysates in pure form by separation on partition columns of powdered cellulose. / Science, Faculty of / Chemistry, Department of / Graduate

No description available.

No description available.

The objective of this research was to investigate the interaction of tackifier resins in water-based and olefinic polymers for potential pressure sensitive adhesive applications. The first part of this research work was focused on evaluating the usefulness of olefinic block copolymer blends with two amorphous polyolefins (atactic propylene homopolymer and ethylene-propylene copolymer) as potential base polymers for hotmelt pressure-sensitive adhesives. Unsaturated and saturated hydrocarbon resins were studied as potential compatibilizing agents and rheology modifiers. Results show that the chemistry of hydrocarbon resins definitely influence the miscibility of the olefinic block polymer and amorphous polyolefin blends. Ethylene-propylene amorphous copolymer based blends seems to show better miscibility characteristics. Based on the learning from blend miscibility studies, we have successfully made pressure-sensitive adhesives for disposable diaper construction application with olefinic block copolymer/ethylene-propylene amorphous copolymer blends, containing unsaturated hydrocarbon resins and saturated hydrocarbon resins. These olefinic adhesives showed good sprayability characteristics, when applied using air assisted spiral spray equipment (Acumeter Spray Coater) and they showed good adhesive peel properties, which were comparable to the SBS based control. The second part of the study was focused on the evaluation of natural rubber latex-based pressure-sensitive adhesives (PSA) containing three different C5 aliphatic tackifier dispersions with different softening points. Natural rubber-based, water-borne PSA wet rheology (rheology in liquid state) was correlated to morphological analysis on a coating and converting stand point. Dry adhesive rheology was also studied and was then correlated to adhesive properties at different conditions. It has been learned that the type and amount of dispersing agents in tackifier dispersions has a major influence in wet rheology of the PSA formulations. Softening point of the dispersion seems to influence the dry adhesive rheology and adhesive properties such as peel, tack and shear.

No description available.

The performance of three different lipid/hydrocolloid coatings was tested on Golden Delicious apples. The coatings consisted of a mixture of lipid, wax, and various gum blends. The three treatments were compared to an uncoated group (control). Both objective and sensory tests were performed to determine the shelf-life stability of the apples. Objective results indicated that all three treatments significantly decreased (P<0.0083) the respiration rates of the apples when compared to the control. The treatment groups also significantly (P<0.0083) maintained the texture of the apples along with a lower (P<0.0083) starch degradation rate. The treatment groups also significantly (P<0.0083) maintained the malic acid level in the apple. There were no significant differences (P>0.0083) among the groups with regard to soluble solids and fresh weight loss. Externally, the treated apples had a significantly greener hue (Hunter color "a") than the control apples, however, there were no significant differences (P>0.0083) in yellow color (Hunter color "b") between the groups. Sensory results indicated that the treated apples were firmer, crisper and juicier (P<0.0083) than the control apples. However there were no significant differences (P>0.0083) in the sweetness, tartness, and appearance of all of the groups. Overall, the derived coatings could serve as a resource for extending and maintaining the shelf life of perishable fruit. / Master of Science

published_or_final_version / abstract / Dentistry / Doctoral / Doctor of Philosophy

No description available.

Inaug.-Diss.--Bern.

No description available.