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Entanglement molar mass

The entanglement molar mass Me for PE is 1.7 kg.mof. The ratio M c/Mg ranges thus between 23 and 59 versus 5 for low crystalline or amorphous polymers. This means that embrittlement occurs while the... [Pg.165]

Within this framework, one can imagine a two dimensional ductile-brittle transition criterion which would be composed of two perpendicular boundaries in the graph la-Mw (Fig. 7). The vertical boundary would correspond to a critical molar mass M c- In polymers of low crystallinity or fully amorphous, M c would be sharply linked to the entanglement molar mass M c 5Me. In polymers of medium to high crystallinity, M c would be the molar mass below which it is impossible to have values higher than lac- The horizontal boundary would correspond to U = lac-... [Pg.169]

The entanglement strand has entanglement molar mass M = N Mq. The entanglement strand effectively replaces the network strand in the determination of the modulus for networks made from long strands, and also determines the rubbery plateau modulus of high molar mass polymer -melts ... [Pg.266]

Equation (8.136) is tested in Fig. 8.17 (solid curves) and found to describe the molar mass dependence of constant friction coefficient viscosity data for all three of these linear polymers. The critical molar mass Me for entanglement effects in viscosity is always a factor of 2-4 larger than the entanglement molar mass Mg. that was defined in Eq. (7.47). [Pg.341]

The plateau modulus Ge defines the entanglement spacing of a polymer melt, and the entanglement molar mass Me[17]... [Pg.448]

This number appears to be constant for flexible polymers, with the average value = 20.6( 8%). Table 25.1 shows data for polyolefin melts listing density p, plateau modulus Ge, melt chain dimensions from SANS o/M, entanglement molar mass Me calculated from Eq. (25.6), Kuhn length b, packing length p, tube diameter a, and the overlap parameter for entanglement P, all at temperature T. [Pg.448]

It can be interesting to establish a relationship between Mp and the entanglement molar mass Mp, this latter being sharply linked to the chemical structure (Fetters et al., 1999). It appears that ... [Pg.385]

Since hydrolysis is a chain scission process, it always induces embrittlement. In initially ductile linear polymers, such as PET or PAll, toughness falls off by two or three decades when the weight average molar mass reaches a critical value Mp of the order of 10-20 mol.kg corresponding to a small multiple of the entanglement molar mass (Fayolle et al., 2008). In the frame of second-order kinetics (rate constant h)> it is possible to determine a lifetime value corresponding to the time to embrittlement ... [Pg.401]

The non-uniformity of the molar mass distribution influences polymer properties and their processing (see Table 4.1.5). The distinguishing feature of commercial polymers is that they have molar masses far in excess of the entanglement molar mass of about 10,000 g/mol. From typical industrial synthesis, a fairly broad distribution of molar mass results. The features of this distributicm have dramatic effects on the processability (viscosity) and properties (miscibility, strength and modulus) of plastics. [Pg.58]

By analogy with an elastomer [Eq. (30)], the small strain rubbery plateau modulus may be set equal to = riekT, where is the entanglement density , assumed to play an equivalent role to n in an elastomer. may therefore be expressed in terms of an entanglement molar mass. Me, according to Eq. (53), where Na is Avogadro s number. [Pg.739]

In the rubbery state the chains may be entangled and the plateau modulus can be used to obtain the entanglement molar mass. If Ge is the plateau modulus, the entanglement molar mass is defined by Me = Ge, where p is the density, K is the gas constant and T is the temperature. [Pg.78]

The so-called entanglement molar mass (Mg) is calculated from the plateau value of the shear modulus (Gg, Fig. 6.8) and, using classical rubber elasticity... [Pg.106]

A recent review (45b) still insists on this process even though it is unable to facilitate chain folding in high molecular weight polymers, nor is it required to account for crystallization behavior below the entanglement molar mass, M. ... [Pg.1160]


See other pages where Entanglement molar mass is mentioned: [Pg.77]    [Pg.48]    [Pg.609]    [Pg.362]    [Pg.367]    [Pg.447]    [Pg.448]    [Pg.448]    [Pg.285]    [Pg.753]    [Pg.80]    [Pg.109]    [Pg.123]    [Pg.205]   
See also in sourсe #XX -- [ Pg.266 , Pg.341 , Pg.362 ]




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