Effect of photo‐initiators on melt degradation of polypropylene and starch‐filled polymer

Abstract

Six series of the processed polypropylene (pp) samples containing 0.25–1 wt% photo‐initiators (PIs, four aromatic carbonyl, two ferric compounds) and also a series of 6 wt% corn‐starch‐filled pp containing 0.5 wt% of each PI, were prepared using a mixer in a closed system at 180 °C for 5 min. The melt flow index (MFI) and apparent viscosity measurments of the processed pp–PI samples showed a large increase in MFI/or decrease in apparent viscosity at 0.25 wt% of the PIs. Further increase in the amounts of PIs led these properties to reach a constant value at 0.5 wt% of the PIs. The presence of corn starch in the samples corresponded to a much lower increase in the MFI or decrease in the apparent viscosity. Ferric stearate and Irgacure 184 amoung the PIs showed the highest and lowest melt degradation effects, respectively. Carbonyl measurments of all the film samples showed good correlations between chemical changes in the pp structure and variations in the flow properties during processing. UV absorption of the films also evidenced the presence of the aromatic carbonyl PIs in the pp matrix after melt processing. © 2002 Society of Chemical Industry

A UV‐initiated reactive extrusion process for production of controlled‐rheology polypropylene

“…This suggests that the UV irradiation, and not the BP concentration, was the key factor for this degradation reaction. Similar results have been achieved in photodegradation of PP and starch‐filled polymer [40].…”

How to Measure Polymer Degradation? An Analysis of Authors' Choices When Calculating the Carbonyl Index

“…The predominance of indoor degradation experiments (Figure b) is due to the need for better and more reliable assessment under accelerated and controlled conditions in a shorter period. ,,− These experiments provide experimental data to indicate optimal parameters for the best adjustment of products and processes that delay degradation and increase lifespan, improving recycling conditions and formulation. ,,− On the other hand, exposition to the weather in outdoor degradation experiments allows better prediction of how properties change as a function of degradation time in realistic conditions, although the experiments take longer. While indoor experimental conditions provide essential information and predictions regarding the behavior of materials under such controlled experimental conditions, laboratory experimental tests do not encompass all conditions of a true-to-life environment.…”

“…In plastics research, perhaps the most common example of this approach is the carbonyl index (hereafter called CI), which measures the intensity or the area of the carbonyl band compared with the intensity or the area of a reference band. From this perspective, the CI has been used for several purposes, such as the evaluation of resistance to degradation through extrusion processes, the assessment of the resistance of recycled and reprocessed materials, the development of stabilizers and formulations, the prediction of the useful life of a material, and the relationship between the level of degradation and the fragmentation potential …”

Vibration-assisted melt compounding of polypropylene/carbon black composites: Processability, filler dispersion and mechanical properties

“…It is known that the thermal and mechanical loadings during processing cause chain scission in the PP molecules and a decrease of their molecular weight and increase of the MFI of the polymer, respectively. [13][14][15] As shown in Figure 2, MFI of the composites fabricated in vibration regime is higher than MFI of the composites fabricated without vibrations and it enhances with the increase of the oscillations frequency.…”