Examensarbete för masterexamen
Tari, Zohreh Gorbani
This study was focused on manufacturing of highly filled cellulose fiber reinforced poly (ethylene-co-acrylic acid) composites and evaluation of the mechanical properties of the composites. Main processes compared were mixing chamber-compression molding, mixing chamber-compression molding followed by calendaring. Composites with up to 60 wt% untreated hammer milled fluffed cellulose fibers processed. Poly (ethylene-co-acrylic acid) (EAA) is a polar polymer and better than non-polar polymer could interact with the polar cellulose fiber. After mixing chamber and compression molded, the highest tensile strength was seen for composite with 40 wt% and the highest stiffness for composite with 50 wt% fiber loading. The result illustrated that increasing the compounding parameters such as mixing time and mixing rate improved the mechanical properties of the composites. Further, drying the cellulose fiber improved the tensile strength of the composite. It was revealed that calendering improved the mechanical properties of the composites significantly. Even for 60 wt% fiber content, tensile strength was higher than for neat polymer. The fiber length was measured in order to evaluate the changes of the cellulose fiber during compounding process. The measurements of the average fiber length in different steps of the processing showed that breakage of the long fibers in mixing chamber was considerable. Scanning electron microscopy showed a good interfacial adhesion between cellulose fiber and ethylene-acrylic acid copolymer. A second part of this work was to compare the results obtained through mixing chamber and calendering with the results from conventional extrusion mixing and subsequent injection molding. The result revealed significant advantages with the extrusion-injection molding process due to better mixing.
Materialvetenskap, Funktionella material, Materials Science, Functional materials