Akademik Veri Yönetim Sistemi
Tezin Türü: Yüksek Lisans
Tezin Yürütüldüğü Kurum: Wageningen Universiteit, VLAG Graduate School, Food Process Engineering, Hollanda
Tezin Onay Tarihi: 2023
Tezin Dili: İngilizce
Öğrenci: Ming Ma
Danışman: Murat Yanat
Özet:
Polylactic acid (PLA) is currently considered one of the most promising bio-based and biodegradable
plastics, which can realize the plastic transition, from conventional to bio. Although PLA is comparable in
properties to some fossil-based plastics (polyethylene, polypropylene), it needs significant improvements
in mechanical strength and barrier properties for widespread use. Therefore, highly abundant, and
biobased chitin nanocrystals (ChNC) have recently been incorporated into PLA matrix. These non-toxic
nanofillers have enhanced the physical properties; moreover, their addition can provide antioxidant and
antimicrobial features to PLA. However, the effect of ChNC addition on the biodegradability of PLA has
not been explored. Hence, this thesis study aims to investigate the biodegradability of ChNC-reinforced
PLA nanocomposites.
The study involved producing ChNC via acid hydrolysis and incorporating them into PLA nanocomposites
using the solvent casting method with a 5 % nanocrystal load. The standard ISO 14851-2019 method was
used to determine the ultimate aerobic biodegradability of microcrystalline cellulose (reference material),
PLA, and PLA/ChNC samples in an aqueous medium over 28 days. PLA/ChNC nanocomposites were
produced by the solvent casting method with a 5% load of the nanocrystal. The standard ISO 14851-2019
method with help of the pressure monitoring system Oxitop was conducted to test the biodegradability
of this nanocomposite. To further study the biodegradation behavior and mechanism, analyses including
scanning electron microscope (SEM), Fourier-transfer infrared spectroscopy (FTIR), and differential
scanning calorimetry (DSC) were made carried out. The materials were characterized before, during, and
after 28 days of the biodegradation period.
After 28 days of biodegradation, the test was confirmed valid with the degree of biodegradation of
reference material over 90%. Furthermore, the biodegradability of PLA is 35%, while PLA/ChNC slightly
lower, the degree of biodegradability reached 25%. According to the ISO standard, PLA and PLA/ChNC are
not considered biodegradable. However, with an overall trend of pressure decrease during the
biodegradation period, an extended biodegradation period is advised to reach better biodegradability
result. The difference of biodegradability between PLA and PLA/ChNC is proved due to the intermolecular
networking effect of nanocrystals, which slowed the rate of biodegradation. Results of this research
suggest that to commercialize biodegradable food package as PLA-based plastic, more efforts are still
needed to balance the conflict between improving mechanical properties and maintaining better
biodegradability.