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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.

A comparison of porous polymers used in collecting organic volatiles in foods

Boyko, Alayne Linda 01 July 1975 (has links)
Porapak Q, Chromosorb 102, and Tenax GC, three porous polymers commonly used as adsorbents in headspace analyses were investigated. The retention times of various low-boiling compounds relative to water were measured on the collection columns to determine which compounds would be lost during the water removal step employed after sampling aqueous materials. Compounds eluted fastest from Tenax GC precolumns and slowest from Porapak Q, with retention times on Chromosorb 102 generally intermediate. Thus, loss of low-boiling compounds relative to water was greatest on Tenax GC and limited the use of this polymer for quantitative study of samples containing low-boiling volatile compounds. The residual water in Porapak Q precolumns employed in the usual procedure for collection of volatile materials by entrainment from aqueous systems, could be completely eluted in 15 min with a N₂ purge of 30 ml/min at 55°C. without appreciable loss of collected organic compounds. Retention times of high-boiling organic compounds were determined on the precolumns, and those containing Tenax GC had shorter times than Chromosorb 102 or Porapak Q. Under conditions employed for unloading trapped compounds from precolumns, fewer compounds remained on Tenax GC precolumns. Thus, Tenax GC appeared to be the trapping polymer of choice in investigations involving high-boiling compounds. Back flushing of Porapak Q, Chromosorb 102, and Tenax GC precolumns during unloading was essential in order to recover the trapped organics within the time allotted for unloading at 135°C. At 280°C back flushing on Tenax GC was not necessary to insure unloading since retention times were well within the unloading period. The recovery of n-undecane from the precolumns after simulated water removal conditions was found to be 98.5% for Tenax GC, 99.5% for Porapak Q, and 100.0% for Chromosorb 102. / Graduation date: 1976

The negative thermal expasion along the chain direction for polymer crystals.

January 1980 (has links)
by Wong Sai-peng. / Thesis (M.Phil.)--Chinese University of Hong Kong, 1980. / Includes bibliographical references (leaves 144-145).

Structure and properties of dimethacrylate polymers

Simon, George Philip. January 1986 (has links) (PDF)
Bibliography: leaves 194-217.

Investigating hydrophilic channels in polymer composites using atomic force microscopy

Cummins, Matthew David. January 2007 (has links) (PDF)
Thesis (M.Eng.)--University of Louisville, 2007. / Title and description from thesis home page (viewed December 14, 2007). Department of Chemical Engineering. "December 2007." Includes bibliographical references (p. 58).

Surface dynamics at the polymer-air interface of water-plasma-treated polydiene films /

Grunzinger, Stephen J., January 2002 (has links)
Thesis (Ph. D.)--Lehigh University, 2002. / Includes bibliographical references and vita.

Nonequilibrium behavior of polymeric network glasses /

Tant, Martin Ray, January 1979 (has links)
Thesis (M.S.)--Virginia Polytechnic Institute and State University. / Vita. Abstract. Includes bibliographical references (leaves 125-127). Also available via the Internet.

Rod-climbing in molten polymers

Vu, Thi Khanh Phuong January 1976 (has links)
No description available.

The morphology of fibrillar polyolefin crystals.

Wikjord, Alfred George. January 1968 (has links)
No description available.

The emulsion polymerization of alkylbutadienes.

Aikin, Archibald McKinlay. January 1949 (has links)
The polymerization of alkylbutadienes has a long history, dating from Grenville William's experiments with isoprene, obtained from the destructive distillation of natural rubber (l). However no large scale production of polymers of butadienes was attempted until World War I, when the Germans manufactured over 2300 tons of polydimethylbutadiene. Until then the natural sources of rubber yielded adequate supplies for world needs. Some research was continued in the field of synthetic rubber andby 1939 the Germans, and later the Western Allies, were able to produce large quantities of synthetic elastomers (the name given to high polymers that possess rubber-like properties). A copolymer of butadiene and styrene, called Buna-S or GR-S, wasconsidered to be the best general purpose synthetic elastomer and this copolymer is produced on a large scale on this continent. Much research has been done on this material but the pure polymers, such as polybutadiene and polyisoprene, have not been investigated as thoroughly since they have failed to show promising properties. As copolymers have the extra variable of compositional heterogeneity, it is thought that the study of pure polymers may lead to an easier and better understanding of the problems involved in obtaining elastomers of the desired properties.[...]

Investigation of surface damage resulting from static charging of moulded plastic components

Taylor, Paul James January 1999 (has links)
Static Charging or Contact Electrification occurs on the separation from intimate contact of materials of dissimilar properties. The amount of charge transferred is dependent on, amongst other things, the contact potential difference between the materials. While a great deal of work has been performed in the past investigating contact electrification, variability in contacts from sample to sample has led to difficulty in providing a fundamental understanding of the process. The investigation here is concerned with surface damage to a plastic component (a spectacle lens), which results from contact electrification. The component in question is cast between two crown glass moulds. After curing, the moulds adhere strongly to the plastic requiring significant leverage to separate them. When separation occurs in the dark, a flash of light is often seen. / Thesis (PhD)--University of South Australia, 1999

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