Diluent method

Other crystallization parameters have been determined for some of the polymers. The dependence of the melting temperature on the crystallization temperature for the orthorhombic form of POX (T = 323K) and both monoclinic (T = 348K) and orthorhombic (T = 329K) modifications of PDMOX has been determined (284). The enthalpy of fusion, Aff, for the same polymers has been determined by the polymer diluent method and by calorimetry at different levels of crystallinity (284). for POX was found to be 150.9 J/g (36.1 cal/g) for the dimethyl derivative, it ranged from 85.6 to 107.0 J/g (20.5—25.6 cal/g). Numerous crystal stmcture studies have been made (285—292). Isothermal crystallization rates of POX from the melt have been determined from 19 to —50 C (293,294). Similar studies have been made for PDMOX from 22 to 44°C (295,296). 

Quinn FA, Jr, Mandelkem L (1959) Thermodynamics of Crystallization in High Polymers Polyethylene, (correction of the of T able 1 for the heat of liision of polyethylene by the diluent method). J Am Chem Soc 81 6533. 

The compilation in Table 5.1 clearly indicates that although a linear relation is observed in plots suggested by Eq. (5.42), the deduced A//u values are much lower than those determined by the diluent method. This is a general conclusion, being based on a widely diverse set of polymers. The differences in A//u values are significant. Differences of a factor of two are observed in some cases. There are several possible reasons for this discrepancy. One is the fact that Eq. (5.42) represents equilibrium for an ideal melt. In the examples cited efforts were not made to determine... 

Table 5.1. Comparison of the copolymer and diluent methods for determining A//u...

Diluent Method for the Heal of Fusion data for polyethylene ethyl benzoate 3.89 kJ/mol tetralene 4.14 kJ/mol... 

---