<p> A high-pressure nitrogen-driven viscometer has been used to study the melt fracture of polystyrene. The polystyrene samples used differed in molecular weight and molecular weight distribution. The weight average molecular weight (Mw) ranged from 97,200 to 1.8 x 10^6 and the distribution breadth (Mw/Mn) from 1.06 to 9.21. Results obtained indicate that the critical shear stress varies linearly with 1/Mw, increases slightly with temperature and is independent of the polydispersity of polymers. This type of behaviour is satisfactorily explained in terms of Graessley's entanglement theory.</p> / Thesis / Master of Engineering (MEngr)

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A study of the effect of shear rate on the inherent and intrinsic viscosities of polystyrene fractions, in dilute solution was carried out. Inherent viscosities were determined for five fractions (of molecular weights ranging from 2.9 x 10 to 4.8 x 106); in three solvents (Benzene, Toluene and Methyl Ethyl Ketone); at five temperatures (from 15°C to 85°C); and shear rates ranging from 1.0 x 103 to 2.8 x 104 sec.-1. Inherent viscosities thus determined were extrapolated to zero rate of shear and the extrapolated values plotted against concentration to determine intrinsic viscosities at zero rate of shear, [N] D=0 The inherent viscosity decreased with increasing shear rate. The slope of the curve of inherent viscosity vs shear rate was found to increase (ie become more negative) with increasing concentration, temperature and molecular weight and to be less in a poor solvent than in a good solvent. At very high molecular weights the value of inherent viscosity was found to decrease non-linearly with shear rate. The intrinsic viscosity was found to decrease with increasing shear rate. The slope of the [N] vs D curve was found to increase with increasing molecular weight and decreasing temperature; the slopes were smaller the poorer the solvent. For the three lower fractions the intrinsic viscosity was found to decrease with increasing temperature, very slightly in Methyl Ethyl Ketone and appreciably in Benzene and Toluene, the relative being greater at higher molecular weights. With the two highest fractions this trend was reversed. The slope of the [N] D=0 vs T curve becoming less negative (and actually positive for Benzene end Toluene). The [N] vs T curves ( [N] at free fall) for the three lower fractions were parallel to those at zero rate of shears but of lower intrinsic viscosity values. With the two highest fractions, the slope of the [N] vs T curve became less negative but not to as great a degree as was found with [N] D=0 vs curves. Intrinsic viscosities obtained at zero rate of shear were applied to the Flory-Fox theory. Calculated intrinsic viscosities for polystyrene fractions in Benzene and Toluene were found to agree to within+-4% of the experimental results. For Methyl Ethyl Ketone a wide variation in values was obtained. / Thesis / Master of Science (MS)

Doctor of Philosophy / Enhancing and recycling plastic are two important focuses in plastics research. In this dissertation, enhancing the property of polyetherimide (PEI) is first discussed, and two methods are introduced. Later, a new recycling strategy, the degradation-upcycling (Deg-Up) strategy, is presented. The potential of Deg-Up is evaluated on three plastics: polystyrene (PS), polyethylene (PE), and polypropylene (PP). These plastics serve broad applications in daily life, such as Styrofoam, food containers, shopping bags, garden decorations, and furniture. PEI, a powerful plastic resilient to high temperature and strength, is broadly used in aerospace, defense technology, space exploration, and transportation. However, PEI can only be processed at high temperatures, and PEI films can be easily dissolved or compromised in many solvents, such as solmethine, chloroform, and furanidin. Water is not permeable in PEI, and therefore, it is strongly demanded to modify the PEI structure, giving PEI new and improved properties for water filtration and purification. We have investigated two methods for modifying PEI. Influencers affecting the PEI film's performance are also studied. Plastic upcycling, which converts low-value wastes to high-value chemical products, is a vital technology that mitigates the environmental crisis and the plastic recycling problem. However, effective plastic upcycling improving waste value with good selectivity toward products with ten-fold or even greater value is uncommon due to the lack of upcycling theories/methodologies. This dissertation presents a new upcycling strategy; the degradation-upcycling strategy (Deg-Up) comprises degradation reactions yielding preliminary chemicals and upcycling reactions converting the preliminary chemicals to desired high-value products. Based on the Deg-Up strategy, PS is converted to fragrances and drug precursors, and PE and PP are Deg-Up to fats and soaps. The economic and industrial possibilities are also discussed through a preliminary industrial design and an economic analysis.

Formaldehyde, an important feedstock in industrial processes and manufacture, is widely present in numerous consumer products. Emitted by many types of consumer products and indoor materials, indoor air can contain high concentrations of formaldehyde. Exposure to formaldehyde is hazardous to human health. Thus knowledge of formaldehyde mass-transfer properties is critical to efforts to reduce formaldehyde emissions and establish related standards and regulations. The primary objectives of this project include: 1) documenting and validating procedures and methods for analyzing and measuring formaldehyde mass-transfer characteristics; 2) evaluating and comparing formaldehyde mass-transfer properties in different materials using micro-balance sorption/desorption tests; 3) investigating observed formaldehyde mass-transfer irreversibility and the recently developed formaldehyde polymerization theory. The procedures and methods for analyzing and measuring formaldehyde mass-transfer characteristics were developed in an effort to minimize experimental variability and were strictly followed during the research. The formaldehyde mass-transfer properties of five polymer materials (polycarbonate, polystyrene, poly(methyl methacrylate), polyethylene and polypropylene) were measured through sorption/desorption testing. Results indicated that formaldehyde solubility was highest in polyethylene while the rate of diffusion was the highest in polypropylene. Results also showed that the diffusion process in the selected polymer materials was irreversible in all cases. Furthermore, additional testing showed no detectable polyformaldehyde formation on polymer surfaces after exposure to formaldehyde. The causes of observed mass-transfer irreversibility need further study. / Master of Science

Block copolymers are widely used in both the academic and industrial communities due to their unique properties. With the development of living polymerization techniques, the synthesis of block copolymers with controlled molecular weights and unique architectures has reached an all time high. Here a novel approach to the synthesis of block copolymers, namely polystyrene-b-polyisoprene, using azide-alkyne click chemistry techniques is investigated. Both azido and alkyne-terminated polystyrene were synthesized using ATRP. Azido-terminated polystyrene was synthesized via a substitution reaction between NaN3 and bromo-terminated polystyrene. Alkyne-functionalized polystyrene was synthesized using propargyl 2-bromoisobutyrate as a functional initiator. ¹H NMR and SEC were used to analyze the degree of polymer functionalization. Anionic polymerization techniques were used to synthesize polyisoprene. Polyisoprenyl lithium was reacted with propylene oxide to obtain hydroxyl-terminated polyisoprene. Functionalization of ≥ 90% was demonstrated via flash column chromatography. The aforementioned hydroxyl-terminated polyisoprene was reacted with both 11-chloroundecanoyl bromide and 11-chloroundecanoyl chloride to synthesize halogen-terminated polyisoprene. As with polystyrene, a substitution reaction with NaN3 afforded azido-terminated polyisoprene. Alkyne-functionalized polystyrene was coupled with azido-terminated polyisoprene via click chemistry to create said block copolymers. The reactions were investigated using ¹H and ¹³C NMR, SEC, IR and in some cases TEM. The clicked block copolymers should provide precedent for the synthesis of supramolecular block copolymers. / Master of Science

Thesis (Ph. D.)--Ohio State University, 2007. / Title from first page of PDF file. Includes bibliographical references (p. 152-167).

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