Investigation of the effect of chitin nanowhiskers distribution on structural and physical properties of high impact polypropylene/chitin nanocomposites
Date
2014-12
Authors
Nel, Alicia
Journal Title
Journal ISSN
Volume Title
Publisher
Stellenbosch : Stellenbosch University
Abstract
ENGLISH ABSTRACT: Polymer composites have been gaining more importance in our daily lives because of the
favorable properties that can be provided by these types of material. A polymer composite
consists of improved properties when compared to the individual polymers that
it is compiled of. The reason that composites are better than the individual polymers
is mainly because composites are a combination of all the bene cial properties from the
individual materials that was used to make the polymer composite.
High impact polypropylene (HiPP) is a complex copolymer that was developed to overcome
the restrictions of polypropylene (PP). Although PP have excellent properties at
lower temperatures, it loses these advantages at elevated temperatures. High impact
polypropylene has a much better impact strength and is processable at high temperatures.
High impact polypropylene has been studied in depth for its applications and its
superior properties such as an improved impact strength. The tensile properties, after
the incorporation of a nano ller, have however not been investigated to our knowledge.
Nano llers have reinforcing abilities due to the nano-scale diameters. Particles that have
sizes on a nanometer range are mostly devoid of defects. Nano llers that are biopolymers
have additional advantages such that can consist of antimicrobial abilities, renewability,
biocompatibility and biodegradability. Composites reinforced with chitin nanowhiskers
(chnw) have shown to have valuable applications in the latest medical, industrial and
environmental developments. Di erent loadings of chnw were incorporated into a HiPP matrix in order to investigate
the e ects that this nano ller will have on the tensile properties of HiPP. There were two
challenges that required attention during the incorporation of chnw into HiPP. The rst
major challenge was the poor interaction that exist between chnw and HiPP due to the
hydrophobic nature of the HiPP matrix and the hydrophilic nature of chnw. The second
problem was the agglomeration that can occur because of the hydrogen bonding between
the chnw that is caused by the structure of the chnw chains. In order to gain the best
dispersion of chnw within the HiPP matrix it was necessary to use compatibilizers and
di erent methods of incorporation. The two types of compatibilizers that were chosen
to improve the compatibility between the HiPP matrix and chnw were polypropylenegraft-
maleic anhydride (PPgMA) and poly(ethylene-co-vinyl alcohol)(EVOH). Injection
molding is typically used to process HiPP and was chosen as one of the methods for incorporating chnw into the HiPP matrix. A second method of incorporation was used
speci cally for the nancomposites containing EVOH known as electrospinning combined
with meltpressing.
Tensile testing, DSC, TGA and FTIR were used to investigate the changes in the mechanical
and thermal properties of the nanocomposites. SEM and TEM were employed
to investigate the morphology of the electrospun ber mats and to characterize the chnw.
FTIR as well as TGA were used to characterize the chitin nanowhiskers and to identify
the individual components within the nanocomposites after incorporation took place.
The incorporation of chnw along with the compatibilizer did show improvement in some
mechanical properties of the polymer matrix. However, the in uence that each type of
compatiblizer had on this e ect varied depending on the content of the chnw and compatibilizer
with regards to the polymer matrix.
Description
Thesis (MSc)--Stellenbosch University, 2014.
Keywords
Nanocomposites (Materials), Chitin nanowhiskers, Reinforcement, Polymeric composites, Dissertations -- Chemistry, Theses -- Chemistry, UCTD