Nylon-6/Agricultural Filler Composites by Yasaman Amintowlieh A thesis presented to the University of Waterloo in fulfillment of the thesis requirement for the degree of Master of Applied Science in Chemical Engineering Waterloo, Ontario, Canada, 2010 © Yasaman Amintowlieh 2010 AUTHOR’S DECLARATION I hereby declare that I am the sole author of this thesis. This is a true copy of the thesis, including any required final revisions, as accepted by my examiners. I understand that my thesis may be made electronically available to the public. ii ABSTRACT Preparation of thermoplastics composites using engineering thermoplastics and plant fibers or fillers is a technical challenge because the processing temperature of the thermoplastics is generally above the temperature of degradation of plant fibers of fillers. There have been numerous attempts for processing high melting point engineering thermoplastics like Nylon-6 with plant natural fibers and fillers. Low temperature processing methods, fiber modification or addition of additives which drops polymer melting point are some of proposed solutions for this problem. The objective of this thesis was to develop a formulation using wheat straw (WS) as a reinforcing fiber for Nylon-6. The concentration of WS was 15 wt-%. The thermoplastic composites were prepared by mixing grinded wheat straw and Nylon-6 using a laboratory scale twin-screw extruder; follow by preparation of samples using injection moulding. The strategy investigated in this thesis was utilization of additives to lower the melting point or to decrease the viscosity of Nylon-6. Lithium chloride salt (LiCl) and N-Butyl benzene Sulfon amide plasticizer (N-BBSA) were used as process additives to decrease melting point and to reduce the processing temperature and time. The addition of the wheat straw (15 wt-%) to the Nylon-6 increased modulus by 26.9 % but decreased the strength by 9.9 %. Effect of different level of these two additives on mechanical, thermal, physical properties and processability of the composite runs were studied. Addition of 4 wt-% LiCl was found to decrease the melting point from 222 °C to 191 °C, to increase modulus by 14 % in comparison to Nylon-6/wheat straw (15 wt-%). However, it decreased the processability and strength by 12.7 %. Plasticizer was investigated to easing processability and decreasing the degradation by reducing the residence time in the extruder, it does not affect the melting point of Nylon-6. The addition of 4 wt-% of plasticizer (N-BBSA) increased modulus and strength only by 2.6 % and 3 %, respectively, in comparison to Nylon-6/wheat straw (15 wt-%) composites. The results of mechanical properties were used as a benchmark for comparisons among samples with different formulations (levels of additives) to find out levels of LiCl and N- iii BBSA for the best mechanical properties. It was found that samples with 2 wt-% LiCl and 2 wt-% of N-BBSA had 29.3 % higher tensile modulus than neat Nylon-6, while its strength was almost same as neat Nylon-6 and 6.3 % higher than Nylon-6/WS (15 wt-%). These results were used to correlate the mechanical properties as a function of percentage of salt and plasticizer in the formulation. Differential scanning calorimetry (DSC) was used to evaluate the percentage of crystallinity and the melting point of the thermoplastic phase and thermal gravimetric analysis (TGA) was used to measure the thermal stability of different formulation. The kinetics of crystallization and degradation were evaluated using results from DSC and TGA, respectively. The activation energy for thermal degradation and the percentage of crystallinity of the thermoplastic composites were correlated to mechanical properties using linear regression. It was found that fiber degradation had a significant effect on strength but the effects of percentage of crystallinity on composites strength were insignificant. On the other hand, the percentage of crystallinity affects stiffness and impact strength. The ductility was a function of both crystallinity and thermal stability. iv ACKNOWLEDGEMENTS I would also like to thank all my friends and colleagues especially Barbara Guettler, Amirpouyan Sardashti, Dr. Ravindra Reddy, Dr. Sang-Young Anthony Shin for all their valuables assistance. I also would like to thank Dr. Tsui and Dr.Yu., my thesis committee members, for accepting to be readers of my thesis, and for all their help and guidance. Further, I would like to acknowledge the financial support and assistance provided by the Ontario BioCar Initiative (ORF-MRI) grant, NSERC-Discovery grant and Omtec Inc. I want to express my sincere appreciation from industrial partners A. Schulman Inc. I would like to thank Dr. Leonardo C. Simon, my supervisor, for giving me opportunity of graduate research. v DEDICATION I like to dedicate this thesis to my mother for all her love and support. vi TABLE OF CONTENTS AUTHOR’S DECLARATION ............................................................................................................................ II ABSTRACT................................................................................................................................................... III ACKNOWLEDGEMENTS ................................................................................................................................ V DEDICATION ............................................................................................................................................... VI LIST OF FIGURES ......................................................................................................................................... IX LIST OF TABLES ........................................................................................................................................... XI LIST OF EQUATIONS .................................................................................................................................. XIII LIST OF ABBREVIATIONS ........................................................................................................................... XIV 1 INTRODUCTION ................................................................................................................................... 1 1.1 MOTIVATION ......................................................................................................................................... 2 1.2 OBJECTIVES ........................................................................................................................................... 4 1.3 OUTLINE OF THE THESIS ........................................................................................................................... 4 2 LITERATURE REVIEW ........................................................................................................................... 6 2.1 PHYSICAL PROPERTIES OF NYLON-6 ........................................................................................................... 6 2.2 PHYSICAL AND MECHANICAL PROPERTIES OF WHEAT STRAW .......................................................................... 9 2.3 ATTEMPTS FOR PROCESSING NYLON AND NATURAL FIBRES .......................................................................... 13 2.3.1 Fiber Treatment .......................................................................................................................... 15 2.3.2 Process Modification ................................................................................................................... 17 2.3.3 Polymer Matrix Modifications ..................................................................................................... 21 2.3.4 Blending with Lower Melting Point Polymers ............................................................................. 31 2.4 NYLON-6/NATURAL FIBER/FILLER MECHANICAL AND INTERFACIAL PROPERTIES ............................................... 31 3 MATERIALS AND METHODS .............................................................................................................. 35 3.1 MATERIALS AND INSTRUMENTS ............................................................................................................... 35 3.1.1 Polymer: Nylon-6 ......................................................................................................................... 36 3.1.2 Antioxidant: Irganox 1098........................................................................................................... 37 3.1.3 Lithium Chloride .......................................................................................................................... 37 3.1.4 Formic Acid .................................................................................................................................. 37 3.1.5 N-Butylbenzenesulfonamide ....................................................................................................... 37 3.1.6 Filler: Wheat Straw Filler ............................................................................................................. 38 3.2 PROCESSING PROCEDURE ....................................................................................................................... 38 3.2.1 Extrusion ..................................................................................................................................... 38 3.2.2 Injection Moulding .....................................................................................................................