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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.
The glass transition of a liquid to a solid-like state may occur with either cooling or compression. [10] The transition comprises a smooth increase in the viscosity of a material by as much as 17 orders of magnitude within a temperature range of 500 K without any pronounced change in material structure. [11]
Therefore, this polymer relies solely on physical anchor points. When heated up to Tg, the material abruptly changes from a rigid state to a tapered state (softens). To achieve the effect, the shape must be changed rapidly to avoid rearrangement of the segments of the polymer chains and immediately cool the material also very rapidly below Tg.
For the production of sutures, polydioxanone is generally extruded into fibers, however care should be taken to process the polymer to the lowest possible temperature, in order to avoid its spontaneous depolymerization back to the monomer. The ether oxygen group in the backbone of the polymer chain is responsible for its flexibility.
That is, is the total number of polymer segments (monomers) in the solution, so is the number of nearest-neighbor sites to all the polymer segments. Multiplying by the probability ϕ 1 {\displaystyle \phi _{1}} that any such site is occupied by a solvent molecule, [6] we obtain the total number of polymer-solvent molecular interactions.
Poly(p-phenylene oxide) (PPO), poly(p-phenylene ether) (PPE), poly(oxy-2,6-dimethyl-1,4-phenylene), often referred to simply as polyphenylene oxide, is a high-temperature thermoplastic with the general formula (C 8 H 8 O) n. It is rarely used in its pure form due to difficulties in processing.
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 ...
[1] [2] Polymers can crystallize upon cooling from melting, mechanical stretching or solvent evaporation. Crystallization affects optical, mechanical, thermal and chemical properties of the polymer. Crystallization affects optical, mechanical, thermal and chemical properties of the polymer.