Darmstadt, Techn. Universiẗat, Diss., 2000.

Orientador: Maria Isabel Felisberti / Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Quimica / Made available in DSpace on 2018-08-05T10:36:42Z (GMT). No. of bitstreams: 1 Goos_SilviaCarlaHaither_D.pdf: 7178544 bytes, checksum: 62ca8cec5872617bf46a79e12727c605 (MD5) Previous issue date: 2005 / Doutorado / Físico-Química / Doutor em Ciências

Nanocrystalline cellulose (NCC) has great potential as a reinforcing agent in thermoplastics (such as polyesters, polyamides and polycarbonates) due to its high mechanical strength and aspect ratio – being compared with reinforcements like steel and carbon nanotubes. In order to maintain its strength when compounded with thermoplastics, the high-temperature processing must not damage the structural integrity of the nanocrystalline cellulose. The processing temperature for polyesters, polyamides and polycarbonates is relatively high and near to the onset of thermal degradation of cellulose bio products, therefore care must be taken to ensure the preservation of the structural integrity of nanocrystalline cellulose. The thermal stability and the kinetics of thermal degradation of five different cellulose samples were studied using an Ozawa-Flynn-Wall method and thermogravimetric analysis data. To complete the characterization of the NCC for polymer processing applications, the crystallinity index was determined using X-ray diffraction; surface morphology was studied with scanning electron microscope, chemical composition was studied using FT-IR, and moisture content was measured using a moisture analyser. Each of these properties observed is essential to the end mechanical properties of the polymer nanocomposite as these properties will affect the dispersion and interfacial adhesion of the fibres to the polymer matrix. After a complete investigation of the cellulose reinforcements, a procedure was developed for dispersion of the NCC fibres into a polycarbonate matrix followed by the moulding of specimen bars. The mechanical properties of the five cellulose-polycarbonate nanocomposites – for example, tensile modulus, flexural modulus and impact strength – were tested and compared to the homo-polycarbonate. The motivation for this project was to design a new material for use as strong, lightweight window substitute; an alternative to conventional residential/commercial windows and a lightweight alternative to conventional automotive glass, offering increased fuel efficiency.

Nanocrystalline cellulose (NCC) has great potential as a reinforcing agent in thermoplastics (such as polyesters, polyamides and polycarbonates) due to its high mechanical strength and aspect ratio – being compared with reinforcements like steel and carbon nanotubes. In order to maintain its strength when compounded with thermoplastics, the high-temperature processing must not damage the structural integrity of the nanocrystalline cellulose. The processing temperature for polyesters, polyamides and polycarbonates is relatively high and near to the onset of thermal degradation of cellulose bio products, therefore care must be taken to ensure the preservation of the structural integrity of nanocrystalline cellulose. The thermal stability and the kinetics of thermal degradation of five different cellulose samples were studied using an Ozawa-Flynn-Wall method and thermogravimetric analysis data. To complete the characterization of the NCC for polymer processing applications, the crystallinity index was determined using X-ray diffraction; surface morphology was studied with scanning electron microscope, chemical composition was studied using FT-IR, and moisture content was measured using a moisture analyser. Each of these properties observed is essential to the end mechanical properties of the polymer nanocomposite as these properties will affect the dispersion and interfacial adhesion of the fibres to the polymer matrix. After a complete investigation of the cellulose reinforcements, a procedure was developed for dispersion of the NCC fibres into a polycarbonate matrix followed by the moulding of specimen bars. The mechanical properties of the five cellulose-polycarbonate nanocomposites – for example, tensile modulus, flexural modulus and impact strength – were tested and compared to the homo-polycarbonate. The motivation for this project was to design a new material for use as strong, lightweight window substitute; an alternative to conventional residential/commercial windows and a lightweight alternative to conventional automotive glass, offering increased fuel efficiency.

No description available.

Synthetic polymers intended for use in biomedical applications require the additional criteria of biocompatibility and sometimes biodegradability included within the design parameters along with mechanical properties, manufacturability, and other properties depending on the specific application in mind. The composition of the monomer and the type of linker within the main chain polymer as well as the chemical reactivity of these chemical entities will define the degradation rates and the conditions under which degradation will or will not occur. However, biocompatibility is usually a built-in characteristic related to the polymer (and monomer) composition and is not easily engineered into an existing polymer by conversion from a non-biocompatible to a biocompatible polymer. Consequently, a majority of the biocompatible polymers used in medical devices or evaluated for biomedical uses are composed of substances that are natural metabolites or known to be biocompatible and nontoxic. Using this design principle, a number of successful examples of biocompatible polymers have been reported such as poly(lactic acid), poly(glycolic acid), and their copolymers, and today, all of these polymers are used in US and EU approved devices. For similar reasons, glycerol-based polymers are attracting increasingly more attention for both fundamental studies and practical applications. Various glycerol polymer architectures from linear to dendritic have been reported for pure polyglycerol ethers and carbonates as well as copolymers with hydroxyacids, for example, to give polyether esters or polycarbonate esters. Herein, the design and synthesis of glycerol-based polycarbonates via copolymerization of epoxide and carbon dioxide is described. The underlying chemistry that affords these glycerol-based polycarbonates will be discussed. Their structural characteristics, their chemical, physical, and rheological properties, and as well as their applications with a focus on drug carrier will also be covered.

Heidelberg, Univ., Diss., 2006.

The functionalization of renewable and abundant carbon dioxide as a building block for industrial polymer production leads to safer designs in manufacturing of materials, decreases the dependence of fossil fuel feedstocks, and diminishes plastic waste generation due to engineered biodegradability. Through judicious catalyst design, the copolymerization of carbon dioxide and oxiranyl small molecules has not only opened new synthetic routes towards the manufacturing of novel polycarbonate architectures, but in addition, allows for the mass production of commodity plastics via raw materials derived entirely from biomass. This environmentally friendly methodology pioneered by Shohei Inoue not only accommodates polymer product with an eco-design, but in tandem serves as a means of carbon capture, mitigating the effects of global climate change. With a global market value anticipated to reach 2 billion dollars by 2026, polyacrylate resins are ubiquitous in the paint, automotive, and adhesive industries. However, the production of these non-degradable polymers compounds the rising concern of plastic pollution in the environment. Herein, the design and synthesis of polyacrylate mimetics bearing a degradable carbonate moiety in the backbone is described. The synthetic methodology utilizes a green pathway through the use of carbon dioxide as the C1 source. The thermal, chemical, and rheological properties of the materials are evaluated and compared to commercial acrylates and adhesives. Additional modification of the materials through terpolyermization is conducted, and their ability to perform as smart adhesive surfaces as well as clinical use in lung resection surgery is covered. / 2020-11-12T00:00:00Z

No description available.

No description available.