engleski

Crystallization behaviour and thermal stability of compatibilized polystyrene/high density polyethylene blends

Polystyrene (PS), high density polyethylene (HDPE) and their blends were prepared by extrusion. Styrene-ethylene/butylene-styrene (SEBS) compatibilizer was added in two different amounts. Differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) were used for characterisation. In general, addition of HDPE to PS increases Tg values of PS phase. Addition of SEBS (5 phr) increased Tg in PS rich blend, but higher amount (7 phr) of SEBS did not effect Tg value. In HDPE rich blend addition of SEBS did not have influence on Tg compared to noncompatibilized blend. The variation in amorphous component Tg depends strongly on the physical state of the semicrystalline domains. Addition of PS to HDPE decreased crystallization temperature (Tc) of HDPE phase, as well as with SEBS addition in PS rich blend. Effect on Tc in HDPE rich noncompatibilized and compatibilized blends was not archive. Melting temperature (Tm) of HDPE phase was decreased in noncompatibilized blends, as well as with SEBS addition. Blending of HDPE with PS decreased crystallinity degree (Χc) of HDPE phase. Addition of SEBS did not effect Χc in PS rich blend, but slightly decreased was obtained in HDPE rich blend. Since SEBS was found in HDPE phase it slowed the crystallization rate and limits the growth of crystalline domains to smaller size and results therefore in a decrease of Tc, Tm and Χc. Addition of HDPE as well as SEBS shifted the beginning of degradation and maximum degradation temperature of PS phase to higher temperature, while maximum degradation temperature of HDPE phase was shifted to lower temperature. Higher effect on these parameters was obtained in PS rich blend, due to differences in morphology.

Polystyrene; high density polyethylene; differential scanning calorimetry; thermogravimetric analysis

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