Study of ultraviolet photooxidative degradation of LDPE film containing cerium carboxylate photosensitizer

Abstract

ABSTRACT:The carbonyl indices (CI) of photooxidation of low-density polyethylene (LDPE) films containing cerium carboxylate (CeCar 3 ) with/ without aromatic ketones (AK) were determined by infrared (IR) spectroscopy. The effects of these photosensitizers on the rates of ultraviolet (UV) photooxidation of LDPE films and their mechanism in sensitizing photooxidative degradation are studied. Results show that CeCar 3 can cause the accelerated photooxidative degradation of LDPE films, but CeCar 3 in combination with AK may bring about the accelerated or retarded photooxidative degradation of LDPE films to varying degrees. After UV irradiation, followed by long duration storage, LDPE films containing these photosensitizers continued storage oxidative degradation at the storage oxidative rates similar to the past, except for the Michler ketone.

Investigating the role of metal oxidation state on the degradation behaviour of LDPE

“…It is generally believed that the LDPE films containing prooxidants enter into the embrittlement stage when the M n is <5000 [14]. The results of [h] and viscosity average molecular weight (M h ) of the formulations as a function of xenon arc and air oven aging time is summarized in Table 3.…”

“…The carbonyl index (CI) was used to characterize the degree of degradation of polyethylene. It has been defined as the ratio of absorbance of the carbonyl band peaking around 1714/cm and internal thickness band at 2020/cm [14]. The thermal behaviour was investigated using a Perkin Elmer Diamond Simultaneous TGA-DTA-DSC under nitrogen atmosphere at a constant heating rate of 5 C/min.…”

“…As is evident, there was negligible increase in the CI of neat LDPE whereas a substantial increase was observed in the CI of films containing pro-oxidant. It is generally believed that polyethylene films enter into the decay stage at CI greater than 6 [14]. Films in the absence of pro-oxidants do not reach the decay stage during the period under investigation.…”

Thermal degradation studies of LDPE containing cobalt stearate as pro-oxidant

“…The absorption band due to stretching of carbonyl group, which is centered around 1714 cm -1 grow in intensity and at the same time, a band broadening is observed which indicate the presence of numerous oxidation products like aldehydes (1733 cm -1 ), carboxylic acid groups (1700 cm -1 ) and (lactones (1780 cm -1 ) [24]. It has been reported that polyethylene films enter into the decay stage at CI greater than 6 [25]. Increase in the CI of F1 was not significant and did not reach this stage even after 600 h of thermal exposure at 70°C.…”

Mn2Al-LDH- and Co2Al-LDH-stearate as photodegradants for LDPE film

“…Products based on cobalt [16][17][18][19][20] iron [21][22][23], manganese [3,24] and cerium [25] have been commercialized. It is believed that they function as catalytic hydroperoxide decomposition agents via the cycle of redox reactions shown in Scheme I [26].…”