Environmental degradation of epoxy–organoclay nanocomposites due to UV exposure. Part I: Photo-degradation

Abstract

The environmental degradation mechanisms of epoxy-organoclay nanocomposites due to accelerated UV and moisture exposure are studied. Various characterisation tools, including FTIR, SEM, XRD and XRF analyses, were used to evaluate the effects of clay content on the progressive changes in chemical element, topography and colour of the nanocomposite. It is found that microcracks started to appear on both the neat epoxy and nanocomposite surface after about 300 h of UV exposure. The nanocomposite exhibited thicker and shallower cracks with a less degree of discoloration than the neat epoxy due to the diffusion barrier characteristics of organoclay with high aspect ratio. The presence of transition metal ions along with low-molecular-weight organic modifiers in organoclay, however, accelerated the degradation of polymer, counterbalancing the above ameliorating barrier properties of clay. FTIR analysis indicated that photo-degradation generated carbonyl groups by chain scission and the rate was slightly higher for the nanocomposites than for the neat epoxy. While moisture further accelerated the photo-degradation process through the enhanced mobility of free radicals and ions, the organoclay could limit the deteriorating effect of moisture, resulting in much better overall resistance to photo-degradation in the presence of moisture for the nanocomposite than the neat epoxy.

Atmospheric corrosion of Nylon 6,6 in Mauritius

“…The formation of these particular chemical compounds is also proposed by RABEK [1]. Additionally, WOO et al [2] identified the presence of carbonyl groups compounds in photo-degraded nanocomposites specimens using Fourier Transform Infrared spectroscopy (FTIR) and reported an increase in its concentration with increasing exposure time to ultraviolet radiation. 3.…”

“…Ultraviolet degradation, such as photo-oxidation. This involves the formation of micro cracks and a yellowing effect on composites [2] or surface cracking on long fiber-reinforced thermoplastic composites samples [3]; 3. Hydrolytic degradation, which can cause subsequent discolouration of the material [4]; 4.…”

“…Mauritius is a tropical island of 1865 km 2 . It lies about 800 kilometres east of Madagascar, as shown in Figure 1.…”

“…Any combination of the above degradation process; 6. Metal induced degradation [2]. Deterioration of synthetic polymers generally involves changes in the physical and visual appearance of the material and may appear in the following ways [5]: Surface embrittlement, crack formation, yellowing of surface, softening of material, discolouration of surface, charring, delamination and swelling of material.…”

Tensile properties and color and mass variations of GFPR composites under alkaline and ultraviolet exposures

“…Nevertheless, the discoloration is often subjective and cannot be associated with loss of strength, stiffness or some other im-portant mechanical property of the composites. Although GFRP photodegradation has been extensively studied [4,7,[9][10][11][12], there is little information on the quantitative color variation and its influence on the mechanical behavior of GFRP composites. In this study, the influence of the accelerated degradation of two types of GFRP composites produced in Brazil on the quantitative change of color was investigated.…”