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JOURNAL OF POLYMER ENGINEERING Vol. 23, No. 2, 2003, page 79 EFFECTS OF DEGREE OF RECYCLING ON THE RHEOLOGY AND PROCESSABILITY OF THERMOPLASTIC POLYMERS
Alex Bonardi1,
Romina Cilloni1, Valerio Paganuzzi1, and Nino Grizzuti2,* 1Laboratorio di Impresa 2Dipartimento di
Ingegneria Chimica, Università di Napoli “Federico II” Piazzale V. Tecchio 80, 80125 Napoli, Italy ABSTRACT
The effects of recycling on the processability of two injection molding
grade thermoplastic polymers has been investigated. Recycling of a Polypropylene
(PP) and a Polyamide (Nylon 6, PA6) has been simulated by repeated injection
molding cycles, followed by blending of the processed materials with the virgin
polymer. The flow properties of both the recycled materials and the blends have
been evaluated by different rheological techniques, namely, capillary viscosity
and MFI measurements, linear viscoelastic tests and solution viscosity number
determination.
The experimental results clearly indicate a qualitatively different
behaviour of the two polymers upon recycling. PP shows a reduction of both
viscosity and viscoelastic properties upon increasing the number of processing
cycles, thus confirming the thermo-mechanical degradation of this polymer. PA6,
conversely, shows an increase of both the melt and the number viscosity as the
number of injection molding passages is increased. The results on PA6 suggest
also that the thermally-induced re-gradation is accompanied by an increase of
the degree of branching, that may be responsible for some peculiar features of
the Virgin/Recycled blend rheology. Keywords: Recycling, Polymers, Rheology
*
To whom all correspondence should be addressed.
Phone: +39 081 7682285; Fax: +39 081 2391800;
e-mail: nino.grizzuti@unina.it
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Freund Publishing House Ltd, P.O. Box 35010, Tel Aviv, Israel, 61350. Tel: 972-3- 562-8540; Fax: 972-3-562-8538 E-mail: h_freund@netvision.net.il; website: https://www.freundpublishing.com
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