Effects of Counits and Diluents

The presence of co-units or stereo defects in a chain, which cannot be included in the crystal lattice, and of low molar mass diluents in the melt modifies the crystallization and melting properties. Time- and temperature dependent 

SAXS and wide angle X-ray scattering (WAXS) studies were carried out to 

The findings for sPP and a variety of related octene-copolymers [7] are depicted in Fig. 23.5. Contrasting the normal behavior of the melting lines, which shift to lower temperatures when the co-imit content increases, the crystallization line is invariant within this set of samples. One observes a unique vs relationship common to all of them, which determines as being inversely proportional to the supercoohng below T = 195° C. 

In a recent experiment the same invariance was also foimd for the lateral size of the blocks in the lamellar crystals [16]. Crystal block diameters can generally be derived from the linewidth of Bragg reflections in WAXS patterns, by application of the Scherrer equation 

As can be seen, all points D o(Tc) are located on one common line. When continued, this line ends again at = 195°C, like the crystallization line of sPP which is also included in the figure. Analogous results were obtained for PE and copolymers with butene- and octene units [16], 

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