Page 31 - POLYMER TECHNOLOGY
P. 31
3.2 Chemical properties of plastic.
a. Decaying due to ultraviolet ray
Ultraviolet (UV) radiation consists of photons with high energy relative to visible
light, it can cause decaying or degradation in the form of physical and chemical
changes in polymeric materials. When absorbed by plastics, UV radiation causes
photooxidative degradation which results in breaking of the polymer chains,
produces free radical and reduces the molecular weight, causing deterioration of
mechanical properties and leading to useless materials, after an unpredictable
time.
Figure 3.5: Decaying or degradation of plastic.
b. Oxidation
Oxidation degradation is a chemical reaction in which oxygen is diffuse into the
molecular structure of the polymer, creating a form of carbon-oxygen bonds
known as carbonyl functionality. It produces a permanent change within the
plastic, most often in the form of molecular weight reduction through shortening
of the polymer chains. Oxidation degradation occur in a relatively long period of
time. Increase the temperature can increase the rate of oxidation of plastic
material. Oxidation will cause the loss of the physical properties of polymers,
mechanical, brittle and lose its color.
Basically, there two types of polymer oxidation, thermal-oxidation and photo-
oxidation.
27 | P a g e
