Environmental Engineering Reference
In-Depth Information
3.2.6 Methods of Synthesis
The method of synthesis also affects the stability and properties of the polymers.
ComparedtocopolymerisedPP,PPsynthesisedusingaZiegler-Nattacatalystandbulk
polymerisation are more susceptible towards photodegradation than one prepared
by copolymerisation [18]. The synthesis method alters the crystallinity and other
properties of the material, which in turns alters how the chemical biodegrades.
3.2.7 Environmental Conditions
In the marine environment, where the polymer is in contact with salt water, the
formation of bioilm increases with exposure time (
Figure 3.2
). But because of the
ocean currents the bioilm formed may get dislodged. This phenomenon depends on
the stiffness of the material. Increase in bioilm increases the extracellular material
(protein) produced by the bacteria. Polymer
biodegradation in the marine environment
is also governed by the environmental conditions which cannot be eficiently controlled
in nature. These include quality of water, radiation, wave and ocean current, amount
of light penetration and seasonal variation [2, 3, 19]. Factors such as humidity,
temperature, pH, salinity, dissolved oxygen (DO) and nutrients have important effects
on the microbial degradation of polymers. The biological environment including
bacteria, fungi, macrofoulant and their enzymes are responsible for biodegradation.
It has been observed that the season and environment (latitude and longitude, depth
of the sample and whether the sample is stationary or in motion) plays a major
role in the biofouling of synthetic polymers used in the marine environment [2, 3].
Changes in ocean currents and seasons affect the DO and the amount of nutrients in
the water which in turns alters the formation of bioilm and oxidation of the surface.
DO is higher towards the open sea than near the shore, so a higher oxidation of
samples exposed to the open sea is observed than to near the shore.
3.3 Types of Polymer Degradation
3.3.1 Biotic Degradation: Biological − Action of Living Organisms, usually
Microbes
3.3.1.1 Enzymic Hydrolysis
Glycosidic, peptide and ester bonds (protein, nucleic acid, polysaccharides and
