The effect of ultraviolet light on the mechanical properties of polyethylene and polypropylene films (original) (raw)
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Effect of UV-aging on the mechanical and fracture behavior of low density polyethylene
Polymer Degradation and Stability, 2020
In polyethylene, a transient, oxidation-induced strengthening is often observed over a narrow range of UV radiation dose. In addition, plastic deformation may not be volume-preserving due to cavitation. Here, we employ a suite of analytical experiments and mechanical testing on pristine and oxidized lowdensity polyethylene films in order to investigate the transient strengthening behavior as well as the propensity for cavitation to fracture. Emphasis is laid on connecting macroscopically observed behavior with microscopic information involving the competition between multi-scale phenomena: chain scission and cross linking at a fine scale, chemi-crystallization, oxidation-induced cracking and mechanical damage at the meso and coarse scales. The results provide an insight into the role of cavitation in the oxidative embrittlement of semicrystalline polymers.
UV Absorption and dynamic mechanical analysis of polyethylene films
2014
Photooxidative processes that lead to chain scission and chain linking in polymers play an important role in polymer degradation. These processes are induced by both ultraviolet (UV) and visible light absorption. The capability of these radiations to be absorbed depends on the existence of chromophores in the polymeric material. Assessment of photodegradation data obtained from a polymer material processed in a conventional manner is of more practical use than extrapolation of data obtained from pure resin. This study reports on the absorption of ultraviolet-light by conventionally processed polyethylene (PE) films. The PE film samples were submitted to UV from fluorescent lamps at 20°C and relative humidity 40% for two hours. Transmission, reflection and emission spectra, from which absorption was inferred, were obtained with anoptical spectrum analyzer. The study also reports the natural degradation under solar action of these PE films for a period of up to 150 days. Degradation w...
Maejo International Journal of Energy and Environmental Communication
In this study, the research was made to understand the knowledge widely related to the degradation process of polyethylene polymer. The mode of treatment that involves in the degradation process of polyethylene is physical treatment while the method of degradation used is photo-degradation of UV light. By using the physical treatment of UV irradiation light, it helps by affecting the bonding that holds the polymer together to break and weakens the plastic. From the result obtained in FTIR and SEM analysis, in FTIR spectrum of LDPE shows higher transmittance compared to FTIR spectrum of HDPE both UV-treated for 30 days. This indicates the high transmittance have few bonds to absorb light in the LDPE sample, low transmittance in HDPE sample means has high population of bonds which have vibrational energies corresponding to the incident light. For SEM result, the polyethylene for LDPE plastic sheet shows the best results for degradation and managed to reduce the weight loss at 87.5% co...
Procedia - Social and Behavioral Sciences, 2015
This study deals with the photodegradation of polyethylene films for greenhouse covering. The UV range of solar light appears as the most deleterious factor of plastic degradation in outdoor exposure. The reasons of this photosensitivity are structural defects which are light absorbing. The use of FTIR as an investigation tools has revealed that the material reacts with surrounding oxygen via a photooxidation process. Although, the photochemical process is quite complex it appears through this study than crosslinking and chain scissions are the most important events taking place during ageing These two key reactions change irremediably the average molecular weight affecting thus drastically the mechanical properties and reducing in the same way the service life time of the films.
Modification of surface and mechanical properties of polyethylene by photo-initiated reactions
Polymer Degradation and Stability, 2003
Low density polyethylene thin films were crosslinked in the bulk and on the surface by means of photo-initiated reactions. The purpose of these experiments was to study if there is a direct relationship between the distribution of crosslinks in the depth of the films and the mechanical properties of the films themselves. By bulk treatment with a PI1 photoinitiator and
World Academy of Science, Engineering and Technology, International Journal of Chemical and Molecular Engineering, 2015
This study deals with the photodegradation of polyethylene films for greenhouse covering. The UV range of solar light appears as the most deleterious factor of plastic degradation in outdoor exposure. The reasons of this photosensitivity are structural defects which are light absorbing. The use of FTIR as an investigation tools has revealed that the material reacts with surrounding oxygen via a photooxidation process. Although, the photochemical process is quite complex it appears through this study than crosslinking and chain scissions are the most important events taking place during ageing These two key reactions change irremediably the average molecular weight affecting thus drastically the mechanical properties and reducing in the same way the service life time of the films.
Effects of Electron-Beam Irradiation and Ultraviolet Light (365 nm) on Polylactic Acid Plastic Films
1999
Strips of Ca-I [polylactic acid (PLA) monolayer plastic films from Cargill Dow Polymers LLC, Minnetonka, MN] cut in the machine and nonmachine directions were irradiated with an electron beam using a CIRCLE III Linear Accelerator (MeV Industries S.A., Jouy-en-Josas, Cedex, France). The effects of 33-kGy irradiation on the physical properties of the Ca-I strips were studied. In addition, the effects of ultraviolet (UV) light (365-nm) illumination on the degradation of three PLA plastic films, Ch-I (PLA monolayer plastic films from Chronopol, Golden, CO), GII (PLA trilayer plastic films from Cargill Dow Polymers LLC), MN), and Ca-I (PLA monolayer plastic films from Cargill Dow Polymers LLC) were analyzed by a modified ASTM D5208-91 method. Results showed that irradiation had decreased the weight-average molecular weight (M w ), stress at break, percentage of elongation, and strain energy of Ca-I by 35.5, 26.7, 32.3, and 44.8%, respectively (P < 0.01). The shelf life of the irradiated Ca-I strips at 5°C and <20 ± 5% RH was about 6 months. The degradation rate of Ch-I, GII, and Ca-I with no UV light treatment at 55°C and 10% RH was 2512, 5618, and 3785 M w /week, respectively. Under the UV light illumination (365 nm), the degradation rate of Ch-I, GII, and Ca-I, was 2982, 8722, and 7467 M w /week, respectively. Hence, the degradation rate of GII and Ca-I was increased 55 and 97% by UV light (P < 0.008), respectively. This trend was not observed in Ch-I because its starting M w (78,000 g/mol) was close to the tensile strength lost range (50,000 to 75,000 g/mol) of PLA films. To our knowledge, this is the first study to demonstrate that UV light does further enhance the degradation of PLA films.
Effect of morphology on the photooxidation of polypropylene films
Polymer Photochemistry, 1985
Photooxidative degradation of polypropylene films with different morphology (degree of crystallinity and orientation) has been followed by means of mechanical tests. The kinetics o[ the photooxidation are signiOcantly depressed on increasing crystaUinity and especially orientation. This behaviour has been interpreted in terms of the reinforcing action due to the oriented crystalline fibrils. A correlation has been attempted between the photooxidative kinetics and a morphological parameter.