Abstract
The influence of an accelerated hygrothermal ageing simulation test on a commercial PLA and its three subsequent mechanically-reprocessed materials was studied. The analysis was focused on the water diffusion kinetics and the physico-chemical changes induced by the hygrothermal degradation. Water diffusion proceeded faster than chain relaxation processes, as defined by a Case II absorption model. It was proved that the water diffusion rate decreased with subsequent reprocessing cycles and increased with higher hygrothermal ageing temperatures. Hydrolytic chain scission provoked significant molar mass decays and consequent general losses of thermal and mechanical performance. The rearrangement into crystalline fractions of shorter chains provoked by hygrothermal ageing was qualitatively and quantitatively followed by both Fourier-Transform Infrared Spectroscopy and Differential Scanning Calorimetry. The microstructural changes were monitored by the cold-crystallization temperature, the crystallinity degree XC and the absorbance intensity ratio I921/I955. A Weibull model showed that the crystallites were formed faster at higher reprocessing cycles and at lower hygrothermal ageing temperatures. All these effects were particularly significant for PLA reprocessed more than one time.
| Original language | English |
|---|---|
| Pages (from-to) | 1881–1890 |
| Number of pages | 10 |
| Journal | Polymer Degradation and Stability |
| Volume | 97 |
| Issue number | 10 |
| Early online date | 15 Jun 2012 |
| DOIs | |
| Publication status | Published - Oct 2012 |
| Event | 3rd International Conference on Biodegradable and Biobased Polymers - ECPM, University of Strasbourg, Strasbourg , France Duration: 29 Aug 2011 → 31 Aug 2011 http://www.biopol.unistra.fr/ |
Bibliographical note
B.Sc. Oscar Gil-Castell is acknowledged for his dedication in the lab and his outstanding attitude towards learning. The authors thank the Spanish Ministry of Science and Innovation, through the Research Projects ENE2011-28735-C02-01 and UPOVCE-3E-013, the Ministry of Education and Science for the awarding of the FPI pre-doctoral grant to L. Santonja-Blasco and FPU pre-doctoral grants to A. Martinez-Felipe and J.D. Badía. The financial support of the Generalitat Valenciana, through the Grisolia (A. Martinez-Felipe) and Forteza (J.D. Badia) programs and the ACOMP/2011/189. UPV is thanked for additional support through the PAID 05-09-4331 program and the PAID 04-11 for the allowance conceded to attend to the III International Conference on Biodegradable and Biobased Polymers (BIOPOL2011) in Strasbourg.Keywords
- Polylactide (PLA)
- Hygrothermal ageing
- Water absorption kinetics
- Crystallinity
- Differential scanning calorimetry (DSC)
- Fourier-transform infrared analysis (FT-IR)