Publisher Summary
Thermoplastic elastomers (TPEs) are a rapidly growing segment of polymer manufacturing. The primary advantage of TPE over conventional rubber is the ease of processing, the wide variety of properties available, and the possibility of recycling and reuse. To qualify as a thermoplastic elastomer, a material must have three essential characteristics: the ability to be stretched to moderate elongations and, upon the removal of stress, return to something close to its original shape; processable as a melt at elevated temperature; and absence of significant creep. Most TPEs have certain similar structural characteristics. The comonomers typically have long runs, making the material a block copolymer. The comonomers are almost always dissimilar, leading to microphase separation on a nanometer length scale, which means these materials are properly termed nanomaterials. This chapter is concerned with the TPE morphology, as the morphology determines their physical and mechanical properties. It illustrates specific examples of the effect of structure on the physical properties. It also discusses the thermodynamics of phase separation, which includes detailed discussions on morphology as well as thermal behavior. This chapter also studies the rheology and processing of these materials. It closes with some applications for thermoplastic elastomers.

13 – Thermoplastic Elastomers

Polymers have been considered as important materials in fabrication of biomedical devices for various medical purposes including drug delivery. Among the suggested polymers, polyurethane (PU) is widely used as biomaterials due to their excellent biocompatibility and physico-mechanical properties. PU contributes in a number of technological applications, such as appliances, clothing, automobile parts, shoe soles, flexible and rigid foams, waterproofing compounds, and surface coatings. The unique combination of biocompatibility with excellent mechanical properties enabled this class of materials to find innumerable applications in the medical field. Examples include cardiovascular applications, reconstructive surgery, drug-delivery systems, and prophylactics. The present chapter gives a comprehensive review of therapeutic nanostructures of PU for drug-delivery applications. The PU technology and its emergence in the biomedical and pharmaceutical applications will be briefly touched upon. The developments in the nanostructures of PU and recent developments in controlled drug-delivery applications will be described in detail.

Polyurethane Nanostructures for Drug Delivery Applications

CAI, SHAOBO. Novel Polymer Composite Materials and Stimulation Devices for Bone Tissue Engineering Applications. (Under the direction of Dr. Thom LaBean). Tissue engineering is a promising therapeutic approach to treat large tissue defects, addressing the challenges of limited tissue sources or potential host rejection in traditional treatment methods such as autograft and allograft. To obtain engineered tissues with ideal physiological conditions, two components are crucial for the tissue regeneration process: scaffold materials and biomimetic stimuli. Each of these components and their interactions have a significant impact on the functionality of engineered tissues. In this dissertation, from a materials science and engineering aspect, advances in the development of functional scaffold materials and novel stimulation devices were performed. Relevant mechanisms of the interactions between the developed materials, or devices, with biological responses were also systematically studied. In the first part of this dissertation, a high-throughput, low-cost, industrial-scale fabrication method was developed to produce a series of multi-functional polymer composites as scaffold materials for tissue engineering applications. With the inclusion of newly synthesized multi-functional additives, the produced polymer composites exhibited excellent osteogenic inducibility to human adipose-derived stem cells and satisfactory antibacterial efficiency against both E. coli and S. aureus. Relative to previously reported methods of direct loading silver nanoparticles into polymeric materials, the developed composites exhibited significantly reduced silver associated cytotoxicity. Also, a novel synergistic antibacterial effect at the material interface was found on the fabricated polymer composite, where the material exhibited significantly lower affinity to bacterial adhesion. In the second part of this dissertation, a novel electrical field stimulation device was developed. The micro-fabricated stimulation device consists of micro-sized interdigitated electrodes, which provide a stable and consistent electric field above the surface. This configuration ensures the generation of a physiologically relevant electric field, even with application of ultra-low electric voltages, eliminating potential adverse electrochemical effects. Polymers were also coated onto the surface of the electrodes to further improve the biocompatibility of the stimulation device. In summary, this dissertation successfully demonstrated the potential of applying industrial polymer processing technologies as a promising alternative approach to produce specially functionalized scaffolds for tissue engineering and regenerative medicine applications. The developed electrical field stimulation device provides manipulation and activation methods for stem cells that can be used without immunogenic bio-agents or complicated equipment. © Copyright 2018 Shaobo Cai

Novel Polymer Composite Materials and Stimulation Devices for Bone Tissue Engineering Applications

Polymerization reactor control can sometimes be used to augment chemistry for the tailored synthesis of polymers. This theme is explored giving attention to generic methods for the control of molecular weight distribution for living polymerization processes when carried out in flow reactors. The role of modeling and simulation for achieving targets are considered.

Modeling, Simulation and Control of Polymerization Processes: Some Aspects for Tailored Synthesis

Doping polymers with metallic materials can improve significantly its use. Ultra high molecular weight polyethylene is known for its high resistance to abrasion and impact, and also for its friction coefficient, which is significantly lower than that of commercial steel and most polymeric materials. Therefore, this material presents high industrial demand despite its processing difficulty due to its high viscosity. One kind of polymer processing which has been widely used recently is the high energy mechanical alloying. This method provokes significant changes in the material, such as crystalline structure transformation, amorphization, formation of metastable phases, and nanostructuring, among others. In order to investigate the influence of iron dopant in structural characteristics of polymeric matrix, ultra high molecular weight polyethylene were doped with low concentrations (between 0.1at% and 1at%) of iron using this method, high energy mechanical alloying. The samples composition was characterized by X Ray Diffraction, Mossbauer spectroscopy. A theoretical molecular modeling was carried out and to simulate the iron presence in polymeric cell, which is in good agreement with the experimental results. Therefore, there is evidence that part of the iron promotes a crossed bond between the polymeric chains. Palavras-chave: Ultra high molecular weight polyethylene (UHMWPE); High energy mechanical alloying; Mossbauer Spectroscopy; structural properties.

/pdf/ultra-high-molecular-weight-polyethylene-doped-with-iron-4rlpvx2a5m.pdf

Ultra high molecular weight polyethylene doped with iron through high energy mechanical alloying

Selected Articles. Acrylate adhesives. Adhesion: fundamental principles. Adhesives in medicine. Appliances: applications of engineered plastics. Armor, composite. Automotive composite components: fabrication. Blow molding of thermoplastics. Bond durability. Bottles and other rigid containers. Cellulose: nature and applications. Composites: applications overview. Composites: manufacturing overview. Computer control in polymer processing. Decorative laminates. Degradation and stabilization, thermal. Design with plastics. Die extrusion. Elastomer-metal adhesion processes. Elastomer-thermoplastics adhesion processes. Elastomer-textile adhesion processes. Elastomeric coatings. Elastomeric foams. Elastomeric products from liquid polymers. Electrical properties of elastomers. Electrodeposited polymer coatings. Fabrics: finishing. Fibers: drawing. Flammability of polymers. Glass-reinforced plastics: thermoplastic resins. Health hazards in elastomer processing. Hot-melt adhesives. Injection molding of polymers: computer simulation. Liquid crystal processing. Melt delivery systems: normal stress pumps. Melt spinning: dynamics. Mixing: basic concepts. Mixing: twin-screw extruders. Offshore engineering applications of polymers. Polyethylene processing to produce ultimate properties. Polymer blends. Powdered and particulate elastomer processing. Processing: shear-controlled orientation. Quality requirements in elastomer processing. Radiation processing. Recycling. Rubber processing. Sports equipment manufacture. Synthetic adhesives. Tubular film extrusion: dynamics and heat transfer. Vulcanization. Vulcanization by silanes. Vulcanization, continuous. Welding of plastics. 2000 lit. refs. approx., numerous illus.

Concise encyclopedia of polymer processing & applications

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Concise encyclopedia of polymer processing & applications