Αλέξανδρος Δ. Γκότσης
Αλέξανδρος Δ. Γκότσης
molecular structure
TUC
Polyporpylene (ΡΡ) is considered as the polymer of the future. Its world market has already surpassed that of other polyolefins (e.g. the several types of PE), polystyrene, and PVC. PP is produced in Greece by ΕΛΠΕ in Thessaloniki. The reasons that ΡΡ is considered so successful are its excellent mechanical properties, its high melting point that allows its use at temperatures higher than those of PE and PS and its lower price (lower monomer cost).
The PP melt, however, has low melt strength, a fact that discourages its use in processes with strong extensional flows (e.g. in foaming or film blowing). The low melt strength is due to its linear macromolecules and the relatively narrow molecular weight distribution. Such melts do not show strain hardening in their elongational viscosity, which is necessary for the stabilisation of the melt, e.g. at the membranes between the evolving foam bubbles. Thus, the bubbles burst easily and the foam collapses.
The melt strength is affected by the molecular weight distribution and the molecular structure of the polymer. The existence of long branches on the chain is the most effective. The study of the relation between molecular structure and elongational rheology is of immediate interest to the PP processing industry, the PP resin manufacturers and the chemical industry that produces chemicals that may catalyse or control the molecular structure, either during the initial polymerisation or a later modification of the polymer in a reactive extruder.
Molecular structure of polypropylene and its melt strength (1999 - ...)
Η ΜΟΡΙΑΚΗ ΔΟΜΗ ΤΟΥ ΠΟΛΥΠΡΟΠΥΛΕΝΙΟΥ ΚΑΙ Η ΑΝΤΟΧΗ ΤΗΓΜΑΤΟΣ
Example:
foam density & long chain branching in polypropylene
Η μοριακή δομή του πολυπροπυλενίου και η αντοχή τήγματος
Η γραμμική δομή της αλυσίδας του εμπορικού πολυπροπυλενίου έχει ως αποτέλεσμα χαμηλή αντοχή του τήγματός του. Για την βελτίωση των ιδιοτήτων εφελκυσμού του τήγματος μπορούμε να αλλάξουμε τη μορφή της αλυσίδας του προσθέτοντας μακριούς κλάδους.
ΔΗΜΟΣΙΕΥΣΕΙΣ
A.D. Gotsis, R.P. Lagendijk and A.H. Hogt, The influence of peroxide modification on the extensional rheological properties of polypropylene, Proceedings, XIIIth Intern. Congress on Rheology, 2000, I-203
C.J. Tsenoglou and A.D. Gotsis, Rheological Characterization of Long Chain Branching in a Melt of Evolving Molecular Architecture, Macromolecules, 34, 4685-4687, 2001
R.P. Lagendijk, A.D. Gotsis, A. Hogt and A. Buijtenhuijs, Peroxydicarbonate modification of polypropylene and extensional flow properties, Polymer, 42(25), 10035-10043, 2001
A.D. Gotsis, A.H. Hogt, Vertakt polypropeen: Hoge smeltsterkte en goede eigenschappen in rekstroming, Kunststof en Rubber, 58(2), 28-30, 2003
A.D. Gotsis, B.L.F. Zeevenhoven and A.H. Hogt, The effect of long chain branching on the processability of polypropylene in thermoforming, Polym.Eng.Sci. 44(5), 973-982, 2004
A.D. Gotsis, B.L.F. Zeevenhoven and C. Tsenoglou, Effect of long branches on the rheology of polypropylene, J. Rheol.,48(4), 895-914, 2004
C. Tsenoglou, E. Vogiatzis and A.D. Gotsis, An integral constitutive equation for the analytic description of nonlinear visco-elastic stress in fluids under elongation, J.Non-Newt.Fl.Mech. 138, 33-43, 2006
E. Borsig, A.D. Gotsis, F. Picchioni, M. van Duin, Addition of Long Chain Branching on Linear Polypropylene in the Solid State, EUR.POLYM.J, 44(1), 200-212, 2008
A.D. Gotsis and M. Kalaïtzakis, Branched PP: high melt strength and processability in elongational flows, Bull.Hell.Soc.Chem.Eng., 202:132-140, 2011