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Digital archive of theses discussed at the University of Pisa


Thesis etd-07262016-103629

Thesis type
Tesi di dottorato di ricerca
email address
Thesis title
Preparation and characterization of compounds based on poly(lactic acid) to tailor processability and mechanical properties
Academic discipline
Course of study
tutor Prof. Lazzeri, Andrea
commissario Prof. Pukanszky, Bela
commissario Prof. Zebarjad, Seyed Mojtaba
  • Design of Experiments
  • Nucleating agent
  • Plasticizer
  • Poly(lactic acid)
  • Rigid amorphous fraction
  • Takayanagi model
Graduation session start date
In the bio-based polymer products, the degree of crystallinity has profound effects on the structural, thermal, barrier and mechanical properties. PLA products, under practical processing conditions as it is well known are in an amorphous form and show low crystallinity because of the intrinsic slow crystallization rate, which limits wider applications in sectors, such as automotive and packaging fields. In processes, such as injection molding, because of the high cooling speed, it is much more difficult to develop significant crystallinity, and thus, processing modifications leading to increased injection cycles are necessary. Alternatively, nucleating agents can be added to PLA for the promotion of crystallinity via traditional processing, such as injection molding, thus better controlling both thermal history and cycle time.
In this study, investigated about the synergic effect between different plasticizers and nucleating agents in order to tailoring mechanical, physical and thermal properties in PLA compounds.
This thesis work represents an insight on the complexity of mechanical behavior of PLA based materials. In order to obtain a modulation of mechanical properties it is necessary to keep into account the effect of processing parameters on the amount and kind of different phases. The change in compositions, in terms of nucleating agents and plasticizer much influence the development of these different phases thus contributing to properties modulation.
The technological exploitation of this study can occur by correctly selecting additives for PLA based materials and also modifying mould temperature and holding time in injection moulding to benefit of the improved crystallization rate in the composition range where a synergy between plasticization and nucleation was found.