Recycled poly(ethylene terephthalate) chain extension by a reactive extrusion process

A commercial-scale reactive extrusion processing system for recycled poly(ethylene terephthalate) (PET) flakes with an added chain extender, pyromellitic dianhydride (PMDA), was investigated. The PMDA concentration was varied with the intention of reaching a higher recycled PET intrinsic viscosity ([η]). The effect of changing the extruder residence time on the system's stability and the recycled PET [η] was also investigated. Reactive extruded PET with a PMDA concentration up to 0.3 wt% was found to have a higher [η] and lower carboxyl content than recycled PET processed in a normal extrusion system. A shift in [η] of about 0.18 dl/g was obtained with a 0.3 wt% PMDA concentration. A PMDA concentration above 0.3 wt% produced chemical, thermal and hydrodynamic instability in the system, causing crosslinking reactions and gel formation. The reactive extrusion system was stable at low residence time (45 s) and moderate (0.15 wt%) PMDA concentration; however, using 0.2 wt% PMDA produced higher reactive extruded recycled PET [η] with lower carboxyl content than other PMDA concentration levels examined. Residence times higher than 45 s produced higher reactive extruded recycled PET [η]. Reactive extruded recycled PET was also tested for mechanical properties. Polym. Eng. Sci. 44:1579–1587, 2004. © 2004 Society of Plastics Engineers.

[1]  S. Hwang,et al.  Reactive extrusion of in-situ composite based on PET and LCP blends , 1997 .

[2]  Shunichi Matsumura,et al.  Chain extenders for polyester. II. Reactivities of carboxyl-addition-type chain extenders; bis cyclic-imino-ethers , 1986 .

[3]  Loredana Incarnato,et al.  Structure and rheology of recycled PET modified by reactive extrusion , 2000 .

[4]  R. Sedgwick,et al.  High-temperature reactions of hydroxyl and carboxyl PET chain end groups in the presence of aromatic phosphite , 1986 .

[5]  F. Chang,et al.  Characterizations for blends of phosphorus‐containing copolyester with poly(ethylene terephthalate) , 1998 .

[6]  H. A. Pohl.  Determination of Carboxyl End Groups in Polyester, Polyethylene Terephthalate , 1954 .

[7]  L. Janssen,et al.  Twin screw extruders as polymerization reactors for a free radical homo polymerization , 1993 .

[8]  L. Janssen.  On the stability of reactive extrusion , 1998 .

[9]  Shunichi Matsumura,et al.  Chain extenders for polyesters. IV. Properties of the polyesters chain‐extended by 2,2′‐bis(2‐oxazoline) , 1987 .

[10]  Shunichi Matsumura,et al.  Chain extenders for polyesters. I: Addition-type chain extenders reactive with carboxyl end groups of polyesters , 1985 .

[11]  Bernard Boutevin,et al.  Study of thermal and mechanical properties of virgin and recycled poly(ethylene terephthalate) before and after injection molding , 2000 .

[12]  G. Karayannidis,et al.  Chain extension of recycled poly(ethylene terephthalate) with 2,2′-(1,4-phenylene)bis(2-oxazoline) , 2000 .

[13]  L. Delamare,et al.  A global computer software for polymer flows in corotating twin screw extruders , 1998 .

[14]  D. Tsiourvas,et al.  Chain extension of poly(ethylene terephthalate) by reactive blending using diepoxides , 1999 .

[15]  Sandro Cobror,et al.  New Technology for Solid‐state Polymerization of Polymers: Polyethylene terephthalate–Solid‐state Polyaddition , 1997 .

[16]  E. Occhiello,et al.  Chain extension of recycled poly(ethylene terephthalate) with 2,2′‐Bis(2‐oxazoline) , 1993 .

[17]  Shunichi Matsumura,et al.  Chain extenders for polyesters. III. Addition-type nitrogen-containing chain extenders reactive with hydroxyl end groups of polyesters , 1986 .

[18]  Shunichi Matsumura,et al.  Chain extenders for polyesters. V. Reactivities of hydroxyl‐addition‐type chain extender; 2,2′‐bis(4h‐3,1‐benzoxazin‐4‐one) , 1987 .

[19]  J. Månson,et al.  Reactive processing of poly(ethylene terephthalate) modified with multifunctional epoxy-based additives , 2000 .

[20]  G. Karayannidis,et al.  Chain extension of polyesters PET and PBT with N,N′‐bis (glycidyl ester) pyromellitimides. I , 1995 .

[21]  Shunichi Matsumura,et al.  Chain extenders for polyesters. VI. Properties of the polyesters chain-extended by 2,2′-bis(4H-3,1-benzoxazin-4-one) , 1987 .

[22]  G. Karayannidis,et al.  Chain extension of polyesters PET and PBT with two new diimidodiepoxides. II , 1996 .