Crystallinity glass transition temperature

Relatively few processible polyimides, particularly at a reasonable cost and iu rehable supply, are available commercially. Users of polyimides may have to produce iutractable polyimides by themselves in situ according to methods discussed earlier, or synthesize polyimides of unique compositions iu order to meet property requirements such as thermal and thermoxidative stabilities, mechanical and electrical properties, physical properties such as glass-transition temperature, crystalline melting temperature, density, solubility, optical properties, etc. It is, therefore, essential to thoroughly understand the stmcture—property relationships of polyimide systems, and excellent review articles are available (1—5,92). 

Permeation and dissolution are the main processes determined by diffusive mass transfer. Permeation of polymers by small molecules depends on their solubility and diffusivity. For both quantities reasonable estimations are possible if some basic data of the permeating molecules (e.g. critical temperature and collision diameter) and of the polymer (structure, glass transition temperature, crystallinity) are known. For the estimation of the permeability of thin layers (films) an additive quantity, the permachor, is available. 

Crystalline and amorphous phases glass transition temperatures, crystalline melting points levels of crystallinity viscoelastic behaviour... 

In order to investigate miscibility and phase behavior of polymer blends, differential scanning calorimetry (DSC) has been frequently used for determination of glass transition temperature, crystalline melting temperature and other thermal properties. 

Glass transition temperature, crystallinity, cross-linking, fiber fillers, plasticizers Molecular weight, chain orientation, reinforcement, rubber additions Molecular motion, reactive groups Free motion of electrons... 

In recent years, the uses of synthetic polymers have expanded from making simple objects to much more complex applications such as targeted drug delivery systems and flexible solar cells. In any case, the application for the polymer is driven by its physical and chemical properties, notably bulk properties such as tensile strength, elasticity, and clarity. The structure of the monomer largely determines the chemical properties of the polymer, as well as other important measurable quantities, such as the glass transition temperature, crystallinity, and solubility. While some impor-... 

Diffusion is comparable to the molecular sieve method of separation in that it is based on size exclusion the polymer matrix allows easy passage of smaller molecules and slows larger ones. The diffusivity component is influenced primarily by the physical properties of the polymer, for example, the glass transition temperature, crystallinity, and cross-linking [35]. 

In the temperature range between 50° K and the glass transition temperature, crystallinity and also chain conformation is not of great influence on the heat capacity. In this range the difference between heat capacities of cis-l,4-polyisoprene and cis-l,4-polybutadiene is caused by the presence of the extra methyl group and can be compared to the difference between heat capacities of polypropylene and polyethylene. 

Developments in differential scanning calorimetry (DSC) for the characterisation of semicrystalline thermoplastics, including mixed recyclates are discussed. The techniques include stepwise DSC for the accurate determination of specific heat capacity, rapid determination of crystallinity using the Gray-Mathot total enthalpy technique, and analysis of crystallisation kinetics. The techniques show the influence of impurities on the glass transition temperature, crystallinity and crystallisation. 6 refs. 

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