January 1994 Additives for Polymers

Essex, SS15 6TC, UK. Tel: +44-268- 418889. Fax: +44-268-418199. Finn-Plast Ltd, Albany, Sea Road, Kilcoole, County Wicklow, Ireland. Tel: +353-1-287- 4795. Fax: +353-l-287-5597.

TECHNICAL BRIEFS

Use of titanium dioxide in vinyl building products

This article concentrates mainly on vinyl compounds for exterior applications, since they use a much greater titanium dioxide concentration than interior compounds, thus affecting usage of titanium dioxide in vinyl to a greater extent. The other reason for discussing particularly these compounds is that they use titanium dioxide not only as a white pigment and opacifier common for paints and coatings, but also as an ultra violet light absorber. The article describes PVC degradation mechanisms, effect of titanium dioxide on PVC weatherability and finally gives an outlook for use of titanium dioxide in vinyl building products. (14 refs). Polymers Paint Colour J., 1993, 183, (Nov IO) 521

Antioxidants for hydroxy- terminated polybutadiene prepolymer

The efficiency of various antioxidants such as N,N’-diphenyl-p-phenylenediamine (DPPDA), 2,5-di-tert-butylhydroquinone(DTBHQ), 2,2- methylenebis-(4-methyl-6-tert-butyl)phenol

(BKF), 4,4methylenebis-(2,6-di-terr-butyl- phenol) (M bis(DTBPh)), etc., on hydroxy- terminated polybutadiene (HTPB) prepolymer has been studied by differential thermal analysis (DTA) and supplemented by differential scanning calorimetry. The concentration of these antioxidants has also been optimised by DTA, and the results obtained indicate that 1% antioxidant is enough to retard auto-oxidation. The

comparative results on their effectiveness indicate that DPPDA, DTBHQ, Mbis(DTBPh) and BKF appear to be very efficient antioxidants and need further evaluation in HTPB based composite propellants. (14 refs). Rubber Plastics & Composites, Processing & Applications, 1993, (5), 30.5-310

Hydroxyphenol sulphur oligomers as stabilizers

The protective effectiveness of two types of hydroxyphenol sulphur oligomers was evaluated with respect to the photo-oxidation and thermo-oxidation of polypropylene and low density polythene, as monitored by infra- red spectroscopy, and compared with normal antioxidants. While their effect on the process of photo-oxidation was, in both cases, slight, their effect on thermo-oxidation was positive and hardly comparable with normal antioxidants. (8 refs). Int. Polymer Science & Technology, 1993, 20, (7), T/70-74 (Translated from: Plasty a Kaucuk, 1993, (3), 74)

Rheology of plasticized PVC filled with aluminium hydroxide

This study examines the effect of the quantity, specific surface and surface treatment of aluminium hydroxide on the rheological behaviour of a PVC melt plasticized with di(2-ethylhexyl) phthalate using capillary rheometry. The experimental results show that, with an increased content of filler in the PVC blend and with an increase in the specific surface of the filler, there is an increase in viscosity, in the system. Increasing the content of surface treated filler, however, only changes the viscosity insignificantly in comparison with blends containing similar fillers without surface treatment. (9 refs). Int. Polymer Science & Technology, 1993, 20, (91, T/57-59 (Translated porn: Plasty a Kaucuk, 1993, (4), 98)

O1994 Elsevier Science Ltd 9