Some aspects of the environmental photo-degradation of LDPE

Influence of climatic ageing on the mechanical properties and the microstructure of low‐density polyethylene films

“…Because the alkyl radicals are not detectable per se with the FTIR and NMR techniques utilized in this work, special experiments using Electron Spin Resonance should be necessary, as shown previously 31. However, the absorption bands at 3600 cm −1 and around 3500 cm −1 observed by FTIR suggest the presence of hydroperoxides because these absorptions are generally attributed to the OH stretching of such groups 3, 19, 32…”

“…As we saw in the experimental section, the weathering principally affects the capability of the material to undergo large plastic stretching. This embrittlement, which has a negative impact on the durability of LDPE films for their application in greenhouse covering, is principally attributed to the reduction of the average molecular weight caused by the multiplication of chain scissions 3, 17, 18, 34. The most probable cause of ductility loss in the plastic stage comes from the scission of tie molecules joining two adjacent crystallites, because it is known36, 37 that these particular chains play a major role in the cohesion of the material at large plastic strain.…”

“…This is because this type of agriculture allows earlier production, higher yields, and sustainable water economy. However, in such regions where sun irradiation is very intensive, it was reported by several authors that the films undergo rapid degradation when exposed outdoor to climatic ageing 1–4. The effect of sun exposure was also investigated for other polyethylene grades, like linear LDPE4 and high‐density polyethylene 5…”

“…However, in such regions where sun irradiation is very intensive, it was reported by several authors that the films undergo rapid degradation when exposed outdoor to climatic ageing. [1][2][3][4] The effect of sun exposure was also investigated for other polyethylene grades, like linear LDPE 4 and high-density polyethylene. 5 Although the study of UV-irradiation ageing in accelerated tests with artificial sources requires less time due to constant photon flux and faster degradation kinetics, 6,7 it is important to study the climatic ageing phenomena in outdoor experiments as well.…”

Degradation study of polypropylene (PP) and bioriented polypropylene (BOPP) in the environment

“…During the process of polymeric materials degradation oxygen diffusion occurs prevalently in the amorphous regions, linking degradability to the thermal history of the material, in addition to synthesis faults (start of degradation in preferential sites and chromophores, as is the case of carbonyls and unsaturated carbons) which do not belong in the crystalline structure, but are rather part of the amorphous region 11 . PP amorphous regions are the most susceptible to degradation and the impurities in the polymeric material can act as a catalyst for photodecomposition 12 . The energy absorbed by means of heat, light, mechanical strain, etc.…”