Polyethylene crystallization from decalin

Growth rate studies of linear polyethylene from other solvents have also been re-ported.(51,53) The results obtained with decalin, a relatively good solvent, are very similar, at all concentrations, to those obtained with p-xylene.(51) In contrast, in a poorer solvent, n -octane, a maximum in the growth rate is observed at all concentrations studied, 0.001 % to 0.1 wt%.(48) However, the rate of decrease is much steeper in this case. Growth rates of linear polyethylene crystallizing from tetradeconol (0.05%), over the molecular weightrangeM = 1.4x 10" to 1.2x 10, are essentially constant at the lower crystallization temperatures. (5 3) However, as the temperature is raised the crystallization rate of the lowest molecular fractions decreases. 

Fig. 13.25 Plot of a against the weight average molecular weight for linear polyethylene crystallizing from different solvents, p-xylene o 86.0 °C and 86.6 °C 90.7 °C. Decalin 85.3 °C n-octane A 98.0 °C.

Figure 6 Micrographs of drawn samples of polyethylene films of Mw = 1.5 X 10 and Mn = 2 x 10 crystallized from solutions in decalin, and from the melt (see Reference 1 for details). The initial polymer volume fractions were (a) - 0.005 (b) - 0.02 (c) - 0.1 (d) - 1.

Figure 14. Scanning electron micrographs of critical-point dried gels of UHMW PE, obtained from 2 % solutions in decalin. A) quiescent conditions B) agitated solutions (lOOOX). Note the lamellar nature of the polyethylene crystals in A, and the fibrillar crystals reminiscent of the flow that occurred during agitation prior to gelation, in B.

Fig. 13.18 Plot of ln( 1 /to, 1) against (r /r)(l/Ar)fora linear polyethylene fraction, M = 1 X 10, crystallizing from av2 = 0.003 solution of the following diluents o decalin tetralin A p-xylene -hexadecane T Q -chloronaphthalene. (From Riande and Fatou (30))...

Figure 13. Wide-angle X-ray (WAXS) pattern of gel of 2 % v/v of ultra-high molecular weight polyethylene (M = 1,500,000 kg/kmol) in decalin. The amorphous halo is due to the solvent the sharp circular reflections result from the 100 and 200 crystal planes of the crystalline polymer junctions.

---