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pps proceeding
Symposium: S08 - Reactive Processing
Oral Presentation
 
 

High “Melt Strength, Tear Resistant Blown Film Based on Poly(lactic acid)

Edmonds Neil (1)*, Plimmer P. N. (2), Tanner Chris (3)

(1) The University of Auckland - Auckland - NewZealand, (2) Plimmer Associates - Auckland - NewZealand, (3) Clariant NZ Ltd - Auckland - NewZealand

A major problems associated with the commercial manufacture of thin films from PLA is that it does not have the processing characteristics of low density polyethylene on blown film lines. PLA has poor melt strength (leading to bubble instability) and develops a permanent crease in the flattened film as it exits the tower of the film line (1). In addition, the thin film product has poor tear strength and an unacceptable ‘noise’ level when converted into flexible packaging. Furthermore, fabricated articles based on PLA are known to show an unattractive tendency toward dimensional instability (2). This behaviour is associated with ‘cold crystallization’, a phenomenon which also causes exudation of any plasticizer added for improving flexibility. Blow moulded articles based on PLA also exhibit dimensional sensitivity above 60oC. All of these issues have been overcome by the technology described in this paper. This has been accomplished without loss of the valuable compostability characteristic of PLA; this was confirmed by evaluation of film in a commercial composting operation. These results have been achieved through novel reactive compounding technology which: (a) Creates a PLA-rich structure containing long chain crosslinks, (b) generates a low glass transition temperature phase covalently bonded to the PLA structure, and (c) provides a material which performs like LDPE in a blown film manufacturing operation. The technology developed is covered by NZ Patent 580231 (3). The patent is held by UniServices Ltd, The University of Auckland, New Zealand. References 1. Processing technologies for poly(lactic acid)-L.T.Lim, R.Aurus,M.Rubino –Progress in Polymer Science, 33 (2008) 820–852 2. Jacobsen, S; Fritz, H. G "Plasticizing Polylactide - the effect of different plasticizers on the mechanical properties", Polymer. Eng. Sci. 1999, 39, 1303-1310). 3. NZ Patent 580231- Reactive Polymeric Mixture –Plimmer, Tanner , 2009