Naslov
Structural, rheological and mechanicat properties change by thermo-oxidative degradation of HIPS during injection moulding recycling process

Autori
Križaj, V. ; Šegudović, Nikola ; Jelčić, Želimir

Vrsta, podvrsta i kategorija rada
Sažeci sa skupova, sažetak, znanstveni

Izvornik
11th International Symposium on Polymer Analysis and Characterization,Book of Abstracts / Barth, H.G. - : ISPAC, 1998, 116-117

Skup
11th International Symposium on Polymer Analysis and Characterization

Mjesto i datum
Santa Margherita Ligure, Italija, 25.05.1998. - 27.05.1998

Vrsta sudjelovanja
Poster

Vrsta recenzije
Međunarodna recenzija

Ključne riječi
HIPS; structural properties; degradation; recycling

Sažetak
Very considerable quantities of potentially useful thermoplastic, high impact polystyrene (HIPS) materials are annually discarded from industrial and domestic sources and in principle there is strong demand for recycling at least a portion of this resources (1). Ideally, the recyclate should be used for the original application, i.e. resulting in a close circle (2), but in practice it is mixed or added to virgin material in various ratios (3). Thermooxidative degradation of polymer chains induced by recycling is the most important factor which could reduce the stability of plastic products. The level of degradation would be more pronounced by multiplication of recycling. The aim of this work is to study structural, rheological and mechanical properties changes of HIPS due to multiple recycling under the condition of injection moulding process. The structural properties were monitored by measuring molecular mass averages and molecular mass distribution (MMD) (4), the rheological properties were monitored by measuring melt flow index (MFI) and mechanical properties were monitored by measuring notched impact strength (IZOD), tensile strength at yield (TY), elongation (ELONG) and tensile strength at break (TR). Two commercial HIPS samples (I with 5.7 % rubber content and II with 6.9 % rubber content) and sample of general purpose PS (PPS) as a reference were investigated. The samples were processed in injection moulding machine with the zone temperature 210-230 C (PPS) and 180-210 C (HIPS) and specimens for determination of mechanical properties were directly produced in the mould. For melt flow index and molecular mass measurements specimens were chopped by grinding. The virgin material undergoes eight recycling procedures and in the recycled material no additional amount of antioxidants is added. After eight recycling steps there is slight increase in MFI and IZOD values, slight decrease of molecular mass and variable change in mechanical properties. Molecular mass decreasing is more pronounced in the higher molecular mass range (GPPS, HIPS I) and there is no change in HIPS II. Decrease in MNl could be caused by some of the " weak links " known from degradation process of PS at moderately high temperature (200-250 C) (4). Weight average MM is in all cases still over 150000. Melt flow index increases after recycling for all samples and this increasing is in accordance with decrease in MM. The tensile strength at yield of HIPS I is almost the same after recycling but that of HIPS II slightly increases. The tensile strength at break of both samples slightly decreases during recycling. The change in impact strength of HIPS II is not very significant after recycling. The impact strength of HIPS I slightly increases during recycling procedures. The results indicate that after eight recycle steps there is slight decrease in molecular mass, and the processing of HIPS is easier (duo to MFI increase) and there is no significant loss of mechanical properties. The recycled material is still useful for injection moulding processing even in the case where no virgin materiel is added during processing. 1. C.Sadrmohaghegh, G. Scott, E. Setudeh, Polym. Plast. Technol. Eng., 24(2&3)1985,149 2 R. Pfaendner, H. Herbst, K.Hoffmann, F. Sitek, Angew. Makrom. Chem., 232,1995,196 3 M.M.F.AI-Jarrah, S.B.Salman, S.A. Hammo, Polym. Deg. and Stab., 23,1988,75 4. M Guaita, O. Chiantore, L.Costa, Polym.Deg. and Stab., 12,1985, 315

Izvorni jezik
Engleski

Znanstvena područja
Kemija

POVEZANOST RADA