Masters Theses

Date of Award

8-1994

Degree Type

Thesis

Degree Name

Master of Science

Major

Polymer Engineering

Major Professor

R.S. Benson

Committee Members

Paul J. Phillips, Jack F. Fellers

Abstract

The following study was an investigation into the characterization of Polyhydroxybutyrate. PHB. and isotactic Polypropylene. 1PP blends. The blends of interest were PHB/1PP and PHB/1PP/g-PP, where g-PP is Polypropylene grafted Maleic Anhydride. The thermal, mechanical, and morphological behavior of PHB/1PP 10/90, 20/80, 25/75. and 50/50 blends along with PHB/1PP/g-PP 25/70/5 and 25/65/10 blends were studied. These blends were produced using a Brabender screw extruder with mixing screw. The investigation was carried out using air cooled, AC. and water quenched. WQ, thin films of each composition.

The thermal analysis showed that IPP melted at approximately 165 °C and crystallized at 109 °C. The melting of PHB occurred at approximately 172 °C and crystallized at 114°C. The crystallization temperature of both PHB and iPP in the blends increased with the concentration of PHB due to unmelted PHB acting as a nucleating agent in the blend. The PHB/iPP/g-PP blends showed decreases in melt temperature and crystallization temperature due to the solubility of g-PP in PHB and 1PP.

Kerner's equation was used to predict the modulus. The tensile stress at fracture was predicted using Passmore's equation, and Nielsen's equation was used to evaluate elongation to break. The addition of g-PP does show an improvement in the modulus and percent elongation, but does not improve the tensile stress at fracture. The use of empirical equations for particulate filled system described the trend in the mechanical properties of these crystalline-crystalline blends.

The glass transition temperature for pure PHB and iPP was 20 °C and 10 °C. respectively. An increase in PHB concentration decreased the Tg of the blends. The storage modulus of PHB/1PP blends showed that PHB acted as a reinforcer to the iPP matrix, The mechanical damping, tan (δ). varied with composition. The amplitude of the damping peaks was greater for the blends than the pure samples due to particle matrix and particle particle friction.

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