Number-average molecular weight, glass transition temperature

Figures 2-5 depict the effects of CL content upon number-average molecular weight, glass transition temperature(Tg) and crystallization characteristics for those copolyesters derived from oligomeric PCL-diols.

T is the glass-transition temperature at infinite molecular weight and is the number average molecular weight. The value of k for poly(methyl methacrylate) is about 2 x 10 the value for acrylate polymers is approximately the same (9). A detailed discussion on the effect of molecular weight on the properties of a polymer may be found in Reference 17. 

Fig. 30. Evolution of the glass transition temperature of polychloroprene-aromatic hydrocarbon resin blends (17 wt% resin content) as a function of the number average molecular weight of the hydrocarbon resin. Tg values obtained from DSC experiments.

The PET studied was Mylar C film (DuPont) of 12 to 25 micron thickness. Such films are biaxially oriented and are about 50% crystalline. The glass transition and melting temperatures are about 70° and 250°C., respectively. The polymer contains several parts per thousand of inorganic materials, moisture, and 1 to 2% cyclic oligomers (mostly trimer) (8). The number-average molecular weight of the polymer molecules is... 

Increases in number average molecular weight, Mn, and cross-link density will both act to increase the T. The addition of plasticizers, such as in the case of PVC, will decrease the value of the glass transition temperature. The glass transition temperature of the plasticized... 

TABLE 1. The effect of sulfone/fluorene copolymer composition on the glass transition temperature and number average molecular weight. 

The glass transition temperature, of a linear polymer with number-average molecular weight M = 3000 is 100°C. The value of Tg increases to 130°C for a sample of the same linear polymer with M = 10,000. A branched sample of this polymer with = 6000 has a Tg of 90°C. Determine the average number of branchings on the branched polymer. 

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