In‐line analysis of the influence of monomeric and oligomeric hindered amine on the hydrolysis of polycarbonate in a PC/ABS blend

Abstract

ABSTRACT:The polycarbonate/polyacrylonitrile butadiene styrene (PC/ABS) blends lose mechanical properties when exposed to outdoor conditions. This is due to the ultraviolet (UV) induced photo-oxidation of the PC phase and the polybutadiene portion of the ABS. It is known that ABS can be stabilised against terrestrial light by the use of hindered amine in combination with a UV absorber. However, such hindered amine cannot be used when PC is present in a multi component polymer blend. The hydrolysis of PC is accelerated when a small amount of hindered amine light stabilisers (HALS) is incorporated in the resin and is exposed to elevated temperature. In this article the effect of monomeric and oligomeric hindered amine on the hydrolysis of PC during the compounding of PC/ABS blend in a twin screw extruder at 240 C is observed by means of in-line UV-vis spectroscopy. Tinuvin 765 was used as monomeric hindered amine and Tinuvin 622 as oligomeric hindered amine. The molecular weight of the compounded sample was determined by gel permeation chromatography (GPC) and the rheological properties were observed using an online viscometer. It was found that the extent of hydrolysis induced by the oligomeric hindered amine is less compared to monomeric amine. It was also observed that polymeric hindered amine imparts better dispersion of the ABS phase into the polymer blend.

Data on Specific Polymers

“…299,300 HALS accelerates the hydrolysis of PC even if a small amount of HALS is present and temperature elevated. 299,300 Oligomeric HALS are more useful in stabilization than monomeric HALS. 299,300 PC samples exposed to UV radiation prior to environmental stress cracking experience more extensive damage.…”

“…299,300 Oligomeric HALS are more useful in stabilization than monomeric HALS. 299,300 PC samples exposed to UV radiation prior to environmental stress cracking experience more extensive damage. 301 The higher sensitivity of photodegraded PC to the stress cracking effects caused by ethanol is probably due to the presence of oxidation products, inducing a higher polarity to PC and, therefore, a higher affinity to ethanol.…”

“…or from hydroperoxide decomposition: 773 Photodecomposition of PS-hydroperoxides by exposure to radiation above 300 783 Discoloration of the polymer (yellowing) during photolysis is explained by the formation of conjugated double bonds: in a process similar to that which occurs in other vinyl polymers. Conjugations of up to four double bonds in the polymer backbone were found.…”

“…1010 Only the first 50 had a substantially reduced molecular weight. Chain scission occurred mostly on the surface whereas crosslinking extended into the full depth of degradation (300 ). Several additional influences should be mentioned.…”

“…1178 The polycarbonate/polyacrylonitrile-butadiene-styrene blends lose mechanical properties when exposed to outdoor conditions, which is caused by the ultraviolet induced photooxidation of the PC phase and the polybutadiene portion of the ABS. 1179 Using oligomeric HALS UV stability of blend was improved. 1179 A blend of poly(-caprolactone) and polyvinylchloride has undergone morphological changes when exposed to UV radiation.…”