Pro-Degradant Activity of Naturally Occurring Compounds on Polyethylene in Accelerate Weathering Conditions

In this work, naturally occurring compounds, such as Vitamin E (VE) and Ferulic Acid (FA), at high concentrations, have been considered as pro-degradant agents for Low Density Polyethylene (PE). However, all obtained results using the naturally occurring molecules as pro-oxidant agents for PE have been compared with the results achieved using a classical pro-oxidant agent, such as calcium stearate (Ca stearate) and with neat PE. The preliminary characterization, through rheological, mechanical and thermal analysis, of the PE-based systems highlights that the used naturally occurring molecules are able to exert a slight plasticizing action on PE and subsequently the PE rigidity and crystallinity slightly decrease, while the ductility increases. To assess the pro-degradant activity of the considered naturally occurring compounds, thin films of neat PE and PE-based systems containing 2 and 3 wt.% Ca stearate, VE and FA have been produced and subjected to accelerated weathering upon UVB light exposure. All obtained results point out that the VE and FA, at these high concentrations, exert a clear pro-oxidant activity in PE and this pro-oxidant activity is very similar to that exerted by Ca stearate. Moreover, the VE and FA at high concentrations can be considered as suitable eco-friendly pro-degradant additives for PE, also in order to control the polyolefin degradation times.

Novel anti-ultraviolet performances of thin films polyurethane containing nano-mixed oxides CeO2-TiO2

The nano-mixed oxides CeO2-TiO2 was synthesized by gel combustion method using polyvinyl alcohol as fuel and mixtures of titanium trichloride and cerium(IV) nitrate at a relatively low calcination temperature of 550°C for 2 h. The prepared CeO2-TiO2 nanoparticles with a specific area of 65.70 m2 g−1 were dispersed in polyurethane matrix in different concentration conditions from 0.0 to 1.5 wt% to study ultraviolet durability following HONDA HES D 6501-97 standards. After 400 h of testing in the QUV accelerate weathering tester, the thin film containing 1 wt% CeO2-TiO2 nano-mixed oxides has presented the noticeable capacity for absorbing ultraviolet light by only 6.8 g.u change in specular gloss at 60° and ΔE = 3.66 in color difference.

EFFECT OF WEATHERING ON DISINTEGRATION AND SHEAR STRENGTH REDUCTION OF CLAY SHALE

Frequent and strong atmosphere and hydrosphere reactions accelerate weathering of clay shale. This study was carried out to determine the effects of frequent natural drying and wetting-drying cycles on clay shales in every 8 days until the value of disintegration ratio, DR reached zero (completely non-durable). Clay shale samples from Semarang-Bawen and Hambalang were tested in the laboratory under four circumstances: (1) without soaking, (2) soaked once in every 8 days, (3) soaked 2 times in every 8 day and (4) soaked 3 times in every 8 days. Disintegration ratio, DR was obtained from the change in grain size distribution of the clay shale due to weathering. Reductions in shear strength of the samples were observed after subjected to wetting-drying cycles. The DR of Semarang-Bawen clay shale reached zero after 32 days, while the DR of Hambalang clay shale showed a range of values between 0.09 and 0.147 on the 80th day. Wetting-drying cycles showed greater impact than natural drying on shear strength parameters reduction. Triaxial tests could only be performed on samples from Semarang-Bawen and Hambalang which were exposed to wetting-drying cycles up to 24 and 32 days of test, respectively beyond which the samples completely disintegrated.