Environmental Engineering Reference
In-Depth Information
distribution of distinct components [23]. Advances to integrate the two techniques
can be the way forward in the characterisation of polymer degradation.
XPS or electron spectroscopy for chemical analysis provides information about the
oxidation and reduction of polymers catalysed by microbial metabolism and it also
facilitates the study of the chemistry of bioilms to some extent [4]. XPS has been
used to give quantitative information about microorganisms, proteins and microbial
adhesins on non-metallic surfaces and metal surfaces [24]. It is a surface technique
that probes the outer atomic layers of a sample. Here a monochromatic beam of low
energy X-rays is focused onto a surface which causes photoelectrons with characteristic
energies to be driven out from an electronic core level [20]. It provides information
pertaining to bulk. The main disadvantage of this technique is the degradation of
the samples during analysis, thin sampling depth (around 3−10 nm) and high cost of
instrumentation. Improvement to this technique which addresses all the shortcomings
will be helpful for polymer research.
Two-dimensional (2D) correlation spectroscopy is an analytical technique for
developing the heterocorrelation between completely different types of spectroscopic
or physical techniques. 2D heterospectral XPS/IR correlation analysis has been
investigated with biodegradable poly(3-hydroxybutyrate-
co
-3-hydroxyhexanoate)
copolymers and provides correlation between XPS and IR bands. This is not possible
from a simple examination of XPS or IR spectra alone [25]. This technique is very
promising in polymer material research and has not yet been fully exploited.
Photo-acoustic spectroscopy (PAS) has both optical spectroscopy and ultrasonic
tomography features, providing a depth resolved study of both optically and
acoustically inhomogeneous media. Thus, it is extremely eficient for studying optically
opaque samples [26]. Background noise hampers acoustic measurements, which if
resolved will make it a useful tool.
XRD is a non-destructive technique that provides thorough details about the chemical
composition and crystallographic structure of materials. It is a relatively new technique
used to determine the changes in the polymer crystallinity because of degradation.
The surface energy of a polymer is an important parameter in biodegradation.
The contact angle indicates the hydrophobicity of the surface, and the greater is its
value the greater is the hydrophobicity. Microbial attack on polymers can affect the
surface energy of the polymers. The modern contact angle instruments use a camera
and software to capture and analyse the drop shape and this helps in both dynamic
and advanced studies. The disadvantage of the goniometer is the relatively long time
required for a single measurement and thus, it is not suitable for online measurements
in combination with other analytical tools. Also the reproducibility and consistency
