Polyethylene linear, equilibrium melting point

Polyethylene (all three low-density, high-density, and linear low-density) is used mainly for food packaging, trashbags, food carryout bags, and so on and has a Tg of-36°C (Gaur and Wunderlich 1980) or -128 °C (Beatty and Karasz 1979) and an equilibrium melting point of 141.4 °C as directly measured on... 

Calculate the molar entropy of fusion for linear polyethylene from the following data equilibrium enthalpy of fusion Ah° = 293 J and the equilibrium melting point TJ, = 415-418 K (different values have been reported). 

The material used in this study is the same linear polyethylene obtained from Dow that was used in om previous studies It has a weight average moleeular weight of 101,300 g/mol and a polydispersity index of 1.88. Isothermal crystallization kineties, equilibrium melting point and lamellar thickness studies for the Dow linear polyethylene have been reported earlier. 

Figure 5.9 shows the creep and recoverable compliances of a metallocene, linear, low-density polyethylene at 150 °C [36]. This polymer has a polydispersity index (Af, /M ) of about two. The data shown start in the transition from the plateau to the terminal zones, and the last few points are in the terminal zone, which corresponds here to steady flow. Note that the experiment had to be continued for about 2.5 hours to reach steady state, where J t) = /° +tlr)g and /j (f) = /°. (/r is the recoverable compliance defined in Eq. 4.26.) It is of interest to compare the creep compliance of an entangled polymer melt with that of a cross-linked elastomer. The latter cannot flow, so at long times /(t) approaches a constant value, the equilibrium compliance, /°. 

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