Browsing by Subject "biopolymers"

Now showing 1 - 2 of 2
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    Physical and Biochemical Strategies for Improving the Yield and Material Properties of Polyhydroxyalkanoate Biopolymers
    (2014-10) Barrett, John
    Polyhydroxyalkanoates (PHAs) are a diverse class of microbially synthesized biopolymers that are valued for their synthesis from renewable feedstocks and rapid biodegradation. As such, the commercial development of PHA plastics has potential to reduce the environmental impact of many, current polymers, which are non-biodegradable and rely on the use of unsustainable petroleum feedstocks. But despite the desirable traits of PHAs, the proliferation of these materials into commercial markets remains slow. Part of this is due to the greater cost of the renewable substrates used for PHA production versus the artificially low cost of petroleum-derived feedstocks. The other part of the challenge of promoting PHA utilization owes to the relatively limited diversity of physical and mechanical properties of PHAs that are currently available. As such, additional work is needed to develop new PHAs, which can satisfy the performance characteristics of many polymers already in use. Motivated by these two main challenges, 1.) to lower the production cost of PHAs and 2.) to broaden the range of unique PHAs materials available, the thesis presented herein details the development of new technologies to increase the substrate-to-product yield of PHA production and to expand the range of physical and mechanical properties of PHA-based materials. Chapter1 gives a broad introduction to polyhydroxyalkanoates and discuss various aspects of their production and application. Chapter 2 highlights the value of block-copolymers as a rich source for scientific discovery and technological development of PHAs. Methods are detailed in Chapter 3. The experimental results are presented in Chapters 4, 5, and 6, which focus generally upon: 4.) production of PHA copolymers in recombinant E. coli , 5.) fabrication and testing of PHA-graphene nanocomposites and 6.) production of PHA copolymers and block-copolymers directly from CO2 using Ralstonia eutropha. Finally, conclusions and prospects for future PHA research and development are given in Chapter 7. Taken all together, this thesis provides a solid foundation in theory and practice, for several technological approaches, which have great potential
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    Synthesis and Physiochemical Characterization of Biobased, Compostable Polymers Containing Lignin
    (2016-09) Harris, Stephanie
    Biobased and compostable materials have gained in popularity as sustainable solutions for reducing waste and minimizing environmental impacts. Polylactide (PLA) continues to be a popular biobased polymer, but has limited use due to its brittleness, high vapor and ultraviolet (UV) light permeability. This study addresses these shortfalls through copolymerization of lactide (LA) with organosolv lignin from switchgrass (OSL) and delta-valerolactone (DVL) to produce 100 % biobased polymers with improved properties. Incorporation of hydrophobic OSL into poly(L-lactide) (PLLA), even in small quantities (up to 0.26%) resulted in a considerable decrease in water vapor transition rate (WVTR) of up to 64 %, nearly a 20 % decrease in UV light transmission, and slowing of hydrolytic degradation. Unfortunately, lignin appears to stop the chain propagation and effectively reduces overall M ̅_w of the copolymer. Young’s modulus for these copolymers is affected little as stress and strain decreased proportionally with the addition of OSL, resulting in a copolymer that is nearly equal to PLLA in stiffness. To improve elasticity, terpolymers of PLLA-DVL-OSL were explored. The addition of DVL to the polymerization was found to increase UV transmission rate, an effect that could be counteracted through OSL addition. PLLA-DVL co and terpolymers showed low Young’s modulus, characteristic for polymers with elastomeric properties. WVTR was seen to decrease with the addition of DVL and was even further reduced through addition of OSL, resulting in an overall WVTR reduction of up to 79 %.