Nondestructive testing of defects in adhesive joints

Photodegradable polypropylene film – Natural weathering studies
K. Rajakumar a , V. Sarasvathy a , A. Thamarai Chelvan b , R. Chitra c and
C. T. Vijayakumar a, *
a Department of Polymer Technology, Kamaraj College of Engineering and
Technology, S. P. G. C. Nagar, K. Vellakulam Post – 625 701, Tamilnadu, India
b Post-graduate and Research Department of Chemistry, Thiagarajar College,
P.O. Box 625 009, Madurai, India
c Centre for Fire, Explosive and Environment Safety, DRDO, P.O. Box 110 054,
Timarpur, Delhi, India.
* E-mail: ctvijay22@yahoo.com
Abstract
Polypropylene (PP) is an attractive and dominating material for packaging due to its low cost,
high tensile strength, gloss and versatility and hence, their consumption increases thereby littering,
which leads to environmental pollution. To solve these problems, out of various technologies
available, photodegradation seems to be a better choice due to the freely available sunlight. The
polymers that degrade by peroxidation followed by bioassimilation of the oxidation products are more
environmentally acceptable than the biodegradable polymers. In the present work, transition metal salt
of stearic acid was synthesized as prodegradant (MF01) and incorporated in PP to enhance the
photodegrdability. The virgin polypropylene and its blend with 0.2 % MF01 were extruded into films
of 60 μm thickness. The films were naturally weathered from the period, December 2006 to March
2007 (winter season) and May 2007 to July 2007 (summer season). The photodegradation behavior
was studied using Fourier Transform Infrared Spectrophotometry (FTIR), Universal Testing Machine
(UTM) and Scanning Electron Microscope (SEM). A steep increase in the various indices like
hydroperoxide, hydroxyl, carbonyl, lactone, ester, carboxylic acid, vinylidene and crystallinity were
noted for virgin PP after 50 days of exposure whereas these values increased after 15 days of exposure
for the prodegradant added PP. The sudden decrease in the elongation at break (%) for the materials
signifies chain scission. PP films having higher carbonyl index values showed surface cracks in the
scanning electron micrographs, indicating the degradation of the material.
Introduction
The synthetic polymers are used in vast areas based on their inertness towards outside
factors like heat, radiation, chemicals and micro organism, but recently, this inertness has become a
major contributor to the serious problem of solid waste disposal [1]. Increasing amounts of municipal
solid waste (MSW), decreasing the landfill capacity for plastic disposal and slow degradation of
plastic litter in the environment, which lead to generate intense interest in degradable plastics in the
last quarter century.
According to estimates, plastic wastes represent 15-25% of municipal solid waste. To
minimize this problem, there are three ways to utilize the plastic waste: landfilling, incineration with
or without energy recovery and recycling. The largest amount of plastic waste is going for landfilling
(65-70%), incineration and recycling amounts to about 20-25% and 10% respectively [2, 3].
Therefore, the environmental problem is still present. So, many researchers have intense interest to
develop polymers that are more degradable in the natural environment after use, is desired for
environmental conservation. Many authors have been investigating about degradable polymers which
were reported in several research articles [4-7].
Now a days polypropylene has achieved in dominating position based on the excellent
price/property relationship thereby it can be applied in various field. Also it is an attractive material