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The Flory–Fox equation relates the number-average molecular weight, M n, to the glass transition temperature, T g, as shown below: =, where T g,∞ is the maximum glass transition temperature that can be achieved at a theoretical infinite molecular weight and K is an empirical parameter that is related to the free volume present in the polymer sample.
In polymers the glass transition temperature, T g, is often expressed as the temperature at which the Gibbs free energy is such that the activation energy for the cooperative movement of 50 or so elements of the polymer is exceeded [citation needed]. This allows molecular chains to slide past each other when a force is applied.
The physical origin of the non-Arrhenius behavior of fragile glass formers is an area of active investigation in glass physics. Advances over the last decade have linked this phenomenon with the presence of locally heterogeneous dynamics in fragile glass formers; i.e. the presence of distinct (if transient) slow and fast regions within the material.
Both types of segments are linked by covalent links so that they actually form block-copolymers. The miscibility of the hard and soft segments in TPU depends on the differences in their glass transition temperature (Tg) [1] which occurs at the onset of micro-Brownian segmental motion, identifiable by dynamic mechanical spectra. For an ...
PTMC is a predominantly amorphous polymer in the relaxed state but it can present some crystallinity, particularly when the chains are stretched. [ 4 ] The polymer presents glass transition temperature ( T g {\displaystyle T_{g}} ) between -15 and -30 °C and melting temperature ( T m {\displaystyle T_{m}} ) ranging from 38 to 41°C.
Repeating unit of polyphthalamide. Polyphthalamide (aka.PPA, [1] High Performance Polyamide) is a subset of thermoplastic synthetic resins in the polyamide family defined as when 55% or more moles of the carboxylic acid portion of the repeating unit in the polymer chain is composed of a combination of terephthalic (TPA) and isophthalic (IPA) acids. [2]
Mutual solubility between a polymer and a solvent may be determined using the Hildebrand solubility parameter. [2] [3] Polymers will generally be more soluble in solvents with similar solubility parameters to their own in a given state (liquid or solid). The solubility parameters of polymers are not greatly affected by changes in temperature ...
Polymers are composed of long molecular chains which form irregular, entangled coils in the melt. Some polymers retain such a disordered structure upon freezing and readily convert into amorphous solids. In other polymers, the chains rearrange upon freezing and form partly ordered regions with a typical size of the order 1 micrometer. [3]