Simultaneous SAXS/WAXS and d.s.c. analysis of the melting and recrystallization behaviour of quenched polypropylene

• Published in: Polymer (Guilford) 1994-01, Vol.35 (7), p.1352-1358
• Main Authors: O'Kane, W.J., Young, R.J., Ryan, A.J., Bras, W., Derbyshire, G.E., Mant, G.R.
• Format: Article
• Language: English
• Subjects: Applied sciences; Crystallization; Exact sciences and technology; monoclinic polypropylene; Organic polymers; Physicochemistry of polymers; Properties and characterization; quenched polypropylene; synchrotron radiation
• ISSN: 0032-3861; 1873-2291
• DOI: 10.1016/0032-3861(94)90333-6

The behaviour of a quenched ethylene-propylene block copolymer cast film has been investigated during melting and recrystallization experiments carried out at heating and cooling rates of 10°;C min −1. The experimental techniques used to follow the melting and recrystallization processes were differential scanning calorimetry (d.s.c.) and simultaneous small-angle X-ray scattering (SAXS) and wide-angle X-ray scattering (WAXS). In particular, the WAXS results show that the melting of the material is preceded by a solid-state transition involving transformation of the quenched structure into the monoclinic α modification. This transition appears as an exotherm in the range 65–120°C on the d.s.c. melting trace. SAXS results show that an increase in the amount of long-range order occurs during this transition. The sample was then found to melt at 162°C. Upon cooling from the melt, recrystallization of the monoclinic α modification was found to occur in the range 123-105°C without any apparent prior formation of the quenched structure.