Formulation and Testing of Thermoplastic Starch and Cellulose Based Composites

Norvill, Brett (2006). Formulation and Testing of Thermoplastic Starch and Cellulose Based Composites B.Sc Thesis, School of Engineering, The University of Queensland.

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Author Norvill, Brett
Thesis Title Formulation and Testing of Thermoplastic Starch and Cellulose Based Composites
School, Centre or Institute School of Engineering
Institution The University of Queensland
Publication date 2006
Thesis type B.Sc Thesis
Supervisor Rowan Truss
Total pages 71
Language eng
Subjects 0913 Mechanical Engineering
Formatted abstract
Thermoplastic starch (TPS) is a product of dry starch powder, plasticisers and a process known as thermal extrusion. The purpose of this thesis is to determine if TPS can be directly combined with two lengths of cellulose fibre, short (TC90 µm) and long (TC2500 µm), both of which are naturally biodegradable.

Composite mixing techniques were conducted using a co-rotating twin-screw mixing apparatus called a Brabender. Mixing speeds in the Brabender averaged 60 revolutions per minute at a chamber temperature of 100oC for 5 minutes. After such time composites were fully mixed. Hot pressing methods were conducted on a Rondal compression bench at 110oC, 70kN for 5 minutes. Samples were cut into dumbbell shapes according to the American Standard for Testing Materials ASTM D638-97 and stored at constant relative humidity conditions at 23oC and 50 percent relative humidity. Mechanical tensile testing was conducted on an Instron model 4505 machine using the Series Nine automated material testing systems.

Mechanical properties show a doubling in modulus from 330 MPa for non-reinforced TPS to 811 MPa for long cellulose composites (10%wt) and a 43 percent increase to 708 MPa for short cellulose composites (15%wt). Short and long cellulose composites indicate an increase of maximum tensile stress at 9.3 and 8.8 MPa respectively above the non-reinforced TPS average of 6.04 MPa. There were significant difficulties in trying to combine long cellulose with TPS and so thick film layering techniques were employed. This method of composite formation yielded varied erroneous results. Long cellulose (TC2500) cannot be reliably homogeneously combined with TPS via Brabender mixing techniques sp film layering was the best option.

TPS is based on starch powder. Recommendations into further composite research for combining long cellulose with TPS include suspending long cellulose in an aqueous medium, adding starch powder and plasticisers then extruding a fully mixed and coherent product. Other recommendations into film layering techniques included reducing the thickness of the films and increasing the amount of ply layering.
Keyword Thermoplastic starch

Document type: Thesis
Collection: UQ Theses (non-RHD) - UQ staff and students only
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Created: Fri, 07 Nov 2014, 15:17:12 EST by Ahmed Taha Siddiqui on behalf of Scholarly Communication and Digitisation Service