Thesis (M.S.)--University of Wisconsin--Madison. / Typescript. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 120-121).

Thesis (M.S.)--University of Wisconsin--Madison, 1966. / eContent provider-neutral record in process. Description based on print version record. Bibliography: l. 101.

Guayule (Parthenium argentatum Gray) has the potential of becoming an important domestic source of natural rubber. Although some progress has been achieved in increasing yields, for guayule to become an economically feasible crop of the southwest desert, further increases in rubber yield, either by increasing biomass or the plant's rubber content, are necessary. Providing the variability for these desired traits is present in available germplasm, the plant breeder must find a means of selecting for these two traits. It is obvious that biomass can be visually estimated, and it is therefore easier to select for this trait in comparison to the plant's rubber content. Due to practical consideration such as harvesting and processing, high rubber content becomes more desirable than extremely large plants. However, it is hoped that measured characters can be found to predict both traits in order to aid the plant breeder. The variables measured in this study were percent rubber and resin, rubber and resin yield(g/plt.), plant height (cm), width (cm) and volume m³, fresh and dry weight (kg/plt.), mean steam diameter (cm), total and mean steam area (cm²), total and mean stem circumference (cm), total circumference/total area (cm⁻¹), stem number, percent dry weight, and regeneration. This study examined a field with 234 guayule breeding lines. A high amount of variability existed both within and among these lines. It was found that dry weight (kg/plt.) had the best correlation to rubber yields (r = 0.92) and plant volume best predicts dry weight (r = 0.84), but none of these variables correlated well with rubber content. The best statistical regression model for percent rubber included four variables, fresh and dry weight (kg/plt.), dry weight (%) and plant volume (m³). This model accounted for 51% of the variability. In comparison, the best regression on rubber yield had an R² = 0.85 for our variables including plant height (cm), width (cm), volume (m³) and dry weight (kg/plt.). It is obvious that rubber yields may be more easily increased by selecting for biomass. However, it appears that in the long term, increases in rubber content will be of critical importance for maximum efficiency. Therefore, a measurable indication of rubber content is needed to aid in selecting for this trait.

The choice of rubber material for use in sealings and hoses in the fuel system is of great importance. If a wrong type of rubber is used, premature failure during service may occur. This impacts the environmental performance, the safety during driving, uptime and economy of the transport. In this diploma work, rubbers for use in sealing and hoses in the fuel system have been evaluated to assess which materials have the potential to be used under long-term use in contact with commercial fuels.   Three commercial fuel hoses, nitrile rubber (NBR), hydrogenated nitrile rubber (HNBR), ethylene-acrylic rubber (AEM) and fluorocarbon rubber (FKM) of varying types and compositions have been evaluated in diesel with 7% RME (rapeseed methyl ester), 100% biodiesel of RME and ethanol fuel. Tests were performed by immersing the materials in fuel and measure the compression set and changes in properties like volume, hardness, tensile strength and elongation at break.   The results showed that one NBR material, one AEM and all FKM are potential materials for long term use in diesel with 7% RME. All types of NBR and two types of FKM (terpolymers, peroxide cured) may be used in ethanol fuel. NBR and HNBR were the only rubbers evaluated in biodiesel. NBR and HNBR with an ACN content of ~30% might be used in 100% RME at lower temperatures for shorter periods. The aging resistance in air was good for HNBR, AEM and FKM but poor for NBR. Life assessment of rubber articles in fuels

Thesis (Ph. D.)--University of Wisconsin--Madison, 1963. / Typescript. Abstracted in Dissertation abstracts, v. 23 (1963) no. 9, p. 3153. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 101-104).

[No abstract submitted] / Science, Faculty of / Physics and Astronomy, Department of / Graduate

This work on the ultraviolet absorption of stretched and unstretched Type 3 GR-S latex films, was undertaken on the suggestion of Dr. H. D. Smith and Dr. E. Guth, with the expectation that the ultraviolet absorption could give information on the arrangement of the molecules in the stretched state as compared with the unstretched latex. Previous investigators have found that styrene has an absorption band with maximum absorption at 2850 angstroms. Since styrene is one of the constituents of GR-S latex, it was supposed that this absorption band would also appear in any spectral analysis of the latex. To find the nature of this band and its behaviour upon stretching the sample was one of the objectives of this research. The type of spectrograph used for this work was a Hilger E496.303 with a wavelength scale, and Spekker photometer attachment. Eastman Type II-F spectroscopic plates were used for all readings. A tungsten steel spark with about 25,000 volts across the electrodes was used as a source for all plates. The unstretched films were prepared by coating a pane of glass with a ten percent solution of zinc chloride, and when dry, the glass was coated with the latex. After drying, a very thin film of rubber was deposited on the glass which could be peeled off as needed. By this method ultraviolet transparent films of initial thickness 0.020 cm. were obtained. These films were stretched into the shape of a spherical bubble by means of nitrogen gas. By calculating the surface areas of the stretched samples and assuming Poisson's Ratio to be 1/2 for rubber, the thicknesses of the stretched samples could be calculated. A narrow absorption band was found for latex of thickness 0.00260 cm. in the region of 2850 angstroms which did not appear to shift with further stretch. A slight broadening effect upon stretching might have been present but it would not amount to more than 5 or 10 angstroms in either direction. From this it was concluded that the absorption centres of the styrene molecules remained unaffected during stretching. Absorption coefficients were also calculated by Lambert's Law on the assumption that the total loss of radiation was due to absorption. It was found that a decrease in thickness was followed by an increase in the absorption coefficient for a constant wavelength. To obtain the true absorption coefficients, the coefficients computed, by Lambert's Law must, be corrected for surface reflection and body scattering. This may affect the values of the coefficients but not the position of the band. The Increase in scattering with a decrease in thickness is suggested to be due to the existence of microcrystals when the latex is under stress. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

The thermal conductivity of GR-I gum stock was measured with an improved apparatus. The thermal conductivity of butyl decreases with temperature showing a double value at temperatures between 0°C and -80°C. Stock containing 10% sulphur showed no hysteresis character, and the conductivity changed only slightly over the temperature range. For the stretched stock a hysteresis loop was found. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

The current research on non-migratory antiozonant systems for natural rubber follows a tripartite study involving the formulation of a coating compound with static and dynamic ozone testing of the coatings, a review of some commercial in-mould coating techniques and analysis of diffusion of a commercial antiozonant through a coating. An outline of the mixing of Nipol 1312, a low molecular weight nitrile butadiene rubber grade produced by leon Chemicals Inc., with other ingredients to produce a coating composition is also given. Test pieces of the natural rubber substrate were placed in pre-coated mould cavities and cured under compression to achieve covulcanisation between the substrate and the coating. All ozone tests were carried out under standard ASTM DI149-911D518-91 conditions. Results show that the formulated nitrile rubber coating compound is able to protect natural rubber from ozone attack with no migration of the antiozonant as in classical chemical antiozonant systems. An up to date patent search on in-mould coating techniques and systems was carried out and evaluated in conjunction with some current commercial coating methods. In this overview, more emphasis is laid on the nature of the coating material which subsequently determines the appropriate coating technique, than on the specific in-mould coating process applied. Post-mould coating work with polyvinyl chloride (PVC) on natural rubber substrate was also assessed. An experimental and theoretical study of the diffusion of the antiozonant N,Isopropyl N-phenyl-pphenylenediamine (IPPD) through a protective coating on a natural rubber substrate is made in the project. This study shows that the protective coating is able to reduce the loss of antiozonant through diffusion while giving the rubber adequate protection from ozone. The study also demonstrates that the combination of a commercial antiozonant and a protective coating gives enhanced product service life and provides protection to damaged regions of the coating.

Thesis (Ph. D.)--University of Wisconsin--Madison, 1958. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 426-432).