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Effect of different mechanical recycling processes on the hydrolytic degradation of poly(l-lactic acid)

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Beltrán González, Freddys and Lorenzo Esteban, Vicente and Orden Hernández, María Ulagares de la and Martínez Urreaga, Joaquín (2016) Effect of different mechanical recycling processes on the hydrolytic degradation of poly(l-lactic acid). Polymer Degradation and Stability, 133 . pp. 339-348. ISSN 0141-3910

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Official URL: http://dx.doi.org/10.1016/j.polymdegradstab.2016.09.018




Abstract

The growing production of poly(lactic acid) (PLA) has increased the interest for the mechanical recycling of this polymer. The main objective of this work is to study the effect of different mechanical recycling processes on the hydrolytic degradation of PLA. A commercial grade of PLA was subjected to two different recycling processes, one of them comprising an accelerated thermal and photochemical aging and a second melt compounding and compression molding step, and other including a demanding washing step after the accelerated aging process. The accelerated aging and, especially, the washing step had a significant effect on degradation during recycling. Samples of virgin and recycled plastic immersed in a phosphate buffered solution at 37 or 58 °C were removed at selected times and then characterized by gravimetric analysis, IR and UV spectroscopy, thermal analysis, x-ray diffraction and microhardness and viscosity measurements. The water absorption process, at both temperatures, can be modeled using a Fickian model only when the immersion times were short. The different recycling processes caused an increase of the diffusion coefficient of PLA at 37 °C, while at 58 °C the differences were smaller. DSC results pointed out that mechanical recycling promotes a slight crystallization of PLA at 37 °C that explains the increasing of the hardness during the hydrolysis.


Item Type:Article
Additional Information:

Received 28 June 2016, Revised 12 September 2016, Accepted 17 September 2016, Available online 19 September 2016.

Uncontrolled Keywords:Poly(lactic acid); Mechanical recycling; Water absorption; Hydrolytic degradation
Subjects:Sciences > Chemistry > Plastics industry
Sciences > Chemistry > Environmental conditions
Sciences > Chemistry > Chemistry, Organic
ID Code:43576
Deposited On:30 Jun 2017 11:54
Last Modified:03 Jul 2017 07:28

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