Blend environmental stability

There are still many problems to be solved with electrically conductive polymers (and blends) before wide-spread commercial use can be expected. Thermal stability, processability, water-borne coating technology development, oxidative and environmental stability e.g., moisture), improved economics and reproducible conductivity are areas, which will require future attention. 

Polymers are also used in adhesives and Avalon [11] noted that TG can be used in combination with a database of information about the components of the product and the product itself to compare the maximum mass loss temperature and profile of the TG curve to provide a quantitative analysis of the product. The database of information can be either a strength or weakness of this approach, depending on the completeness of the data available for the comparative work. The use of DSC, DMA/TMA and TG were also discussed [12] relative to adhesive applications. Among the properties examined were % crystallinity, Tg, cure state, environmental stability, blend ratios, modulus and damping, thermal expansion and shrinkage, composition, volatiles and plasticizer levels. 

P3HT layer at the interface was effectively encapsulated by the crystalline PE phase on the top, resulting in significantly improved environmental stability. In contrast, when a film was cast at room temperature (scheme II), PE crystallized before P3HT, which resulted in poor device performance (t[Pg.207]

The morphologies of the miscible, immiscible, and partially miscible polymer blends are distinct from each other. In an immiscible blend, two phases are present the discrete phase (domain), which is lower in concentration, and the continuous phase, which is higher in concentration. The miscible polymer blends exhibit singlephase morphology. Partially miscible polymer blends may form completely miscible blends at a different composition. The two phases may not have a well-dehned boundary. Each component of the blend penetrates the other phase at a molecular level. The molecular mixing that occurs at the interface of a partially miscible two-phase blend can stabilize the domains and improve the interfacial adhesion. A compatible blend that has commercial possibilities may be immiscible, and a miscible polymer blend may lack commercial applications due to other factors such as cost, source of raw materials, safety, and environmental issues such as recyclability. 

The research devoted to the study of different chemical and physical aspects of polypyrroles is largely justified by their potential technological applications. The full range of techniques available from polymer chemistry and physics (copolymerization, processable precursors, inclusion of substituents, blend and composite or latex formation, and the versatility of electrochemical methods of film production, as well as the relatively high level of environmental stability in its doped state, processability and high mechanical integrity) can be applied to the development of useful materials for specific applications. In fact, fabrication of conducting... 

The addition of a comonomer to a semicrystalline polymer typically causes a loss in crystallinity, unless the second monomer crystallizes with the first. The decrease in crystallinity is very significant as small quantities of the comonomer are added, and it is accompanied by reductions in stiffness, hardness and melting point. Because vinyl polymers are thermoplastic and completely miscible with most organic solvents, copolymerization with vinyl monomers is a logical route to conventional processability and environmental stability. This route was pursued by polymer chemists who desired these properties in an electrically conductive material. But with the low percolation threshold observed in simple blends of vinyl polymers and conducting polymers, work on copolymerization has been abandoned in favor of composites. The two principal drawbacks of composites are incompatibility of the components and lack of genuine solution processability. What follows is a brief review of efforts to obtain electrically conducting and processable random vinyl copolymers of 3-methylthiophene. 

Sulfur is naturally present in many crude oils and petroleum fractions, most commonly as organic sulfides and heterocyclic compounds. Residual fuel oils are variable products whose sulfur contents depend not only on their crude oil sources but also on the extent of the refinery processing received by the fuel oil blending components. Sulfur, present in these fuel oils in varying amounts up to 4 or 5% w/w, is an undesirable constituent, and many refining steps aim to reduce the sulfur content to improve stability and reduce environmentally harmful emissions. 

The selection of polymers and polymer blends for use as specific materials requires the consideration of how these will withstand the environmental conditions to which these will be subjected. The long term stability of a polymer will depend on its aging characteristics both physical and chemical. 

---