Development of Bio-based Phenol Formaldehyde Resol Resins Using Mountain Pine Beetle Infested Lodgepole Pine Barks by Yong Zhao A thesis submitted in conformity with the requirements for the degree of Doctor of Philosophy Faculty of Forestry University of Toronto © Copyright by Yong Zhao 2013 Development of Bio-based Phenol Formaldehyde Resol Resins Using Mountain Pine Beetle Infested Lodgepole Pine Barks Yong Zhao Doctor of Philosophy Faculty of Forestry University of Toronto 2013 Abstract Phenol formaldehyde (PF) resol resins have long been used widely as wood adhesives due to their excellent bonding performance, water resistance and durability. With the growing concern for fossil fuel depletion and climate change, there is a strong interest in exploring renewable biomass materials as substitutes for petroleum-based feedstock. Bark, rich in phenolic compounds, has demonstrated potential to partially substitute phenol in synthesizing bio-based PF resins. In this study, acid-catalyzed phenol liquefaction and alkaline extraction were used to convert mountain pine beetle (MPB; Dendroctonus ponderosae) infested lodgepole pine (Pinus contorta) barks to phenol substitutes, liquefied bark and bark extractives. Two types of bio-based phenol formaldehyde (PF) resol resins, namely liquefied bark-PF resin and bark extractive-PF resins, were then synthesized and characterized. It was found that acid-catalyzed phenol liquefaction and alkaline extraction were effective conversion methods to obtain phenol substitute with the maximum yield of 85% and 68%, respectively. The bio-based PF resol resins had higher molecular weights, higher ii polydispersity indices, shorter gel times, and faster curing rates than the lab synthesized control PF resin without the bark components. Based on the lap-shear tests, the bio-based PF resol resins exhibited comparable wet and dry bonding strength to lab PF resin and commercial PF resin. The post-curing thermal stability of the bio-based PF resins was similar to the lab control PF resin. The liquid-state 13C nuclear magnetic resonance (NMR) study revealed significant influences on the resin structures by the inclusion of the bark components. Methylene ether bridges, which were absent in the lab PF resin, were found in the bio-based PF resins. The bark components favored the formation of para-ortho methylene linkages in the bio- based bark extractive-PF resins. The liquefied bark-PF resin showed a higher ratio of para-para/ortho-para methylene link (-CH2-), a higher unsubstituted/substituted hydrogen (-H/-CH2OH) ratio and a higher methylol/methylene (-CH2OH/-CH2-) ratio than the bark extractive-PF resin. Both tannin components of bark alkaline extractives and phenolated barks contributed to the acceleration of the curing rate of the bio-based resins. This research demonstrated the promise of the bio-based PF resins containing either bark alkaline extractives or liquefied barks as environmentally friendly alternatives to PF adhesives derived solely from fossil fuel based phenol and proposed a novel higher value- added application of the largely available barks from the mountain pine beetle-infested lodgepole pine trees. iii Acknowledgements First and foremost, I would like to express my sincere and profound gratitude to my supervisor, Prof. Ning Yan, for her outstanding and exceptional mentorship. With her inspirational guidance and encouragement, generous support and constant trust and patience, Prof. Yan brought me to the interesting and promising research areas, taught me how to do the research and helped me grow as a scientist. Her ever-lasting dedication to research, endless pursuit of excellence and rigorous working ethnic set up a perfect role model for those want to pursue their career in the academic area like me. I was extremely lucky to be her student and to work with her. Thanks to Prof. Yan, I had a fruitful and joyful PhD student life. I would also like to give my heartfelt appreciations to my co-supervisor, Mr. Martin W. Feng, a senior research scientist, at FPInnovations-Wood Products Division, for his invaluable guidance, support, and encouragement during the course of my PhD study. I have benefited greatly from his advices. I am very grateful to my supervisory committee, Prof. Paul Cooper, Prof. Bruce McKague, and Prof. Mohini Sain for their insightful suggestions and recommendations for my thesis study. I would like to extend my thanks to Dr. Tim Burrow for his help with the NMR measurements and discussions; Dr. Arturo Rodriguez for the FTIR training and help; Dr. Robert Jeng for the MALDI-TOF training; Dr. Syed Abthagir Pitchai Mydeen for his kind, generous and consistent help on the TGA and DSC instruments and other lab work. Mr. Tony Ung for his kind technical support on using the hot press and lab-shear test. Mr. Gireesh Gupta and Dr. Zheng Chen for their generous support and useful discussions. Assistances by other lab members of Prof. Yan’s group at the Faculty of Forestry, University of Toronto are highly appreciated. I would also like to especially thank Jiang Tang, Mingli Sun, Lei Shen, Feng He, Sheng Dai, Haizheng Zhong, Xuping Sun, Jingjing Li, Nan (Crystal) Wu, Jieming Chen, Xiao Han, Jing Wang, Myungjae Lee, Andrew Avsec, Lip Liew, Susan Frye, Luke Hall, Ethan iv McBride, Dana Collins, Brooke Lehman, Adam Palmer, Adam Martin. Their friendship and encouragement are invaluable and important to me. They made my life at the University of Toronto so enjoyable and memorable. I like to express my sincere thanks to my master thesis supervisor and some old friends in China, including, Prof. Benhua Fei, Prof. Songlin Yi, Prof. Xiaoxu Wang, Prof. Zhaohui Wang, Prof. Wenhua Lu, Prof. Haiqing Ren, Prof. Xia Lang, Prof. Yubo Chai, Ms. Dongkun Wang, Ms. Ying Liu, Ms. Yanhui Huang, Ms. Shuqin Zhang, Mr. Xiaoyu Lu, Mr. Zhenyu Wu and Mr. Xiaodong Zhou for their constant support and encouragement. Special thanks are given to my best friend, Yubo Chai, I am deeply indebt to him for all his help. Despite being far away, their constant support made my life in Canada much easier. I cannot imagine what my life would have been without their help. I will remember their kindness forever. I would like to extend my utmost gratitude to my parents, my aunts and uncles, and my cousins as well as my other relatives. Their unconditional love, support and encouragement made all my accomplishments possible. To them, I dedicate this thesis. v Table of contents Abstract ............................................................................................................................... ii Acknowledgements ............................................................................................................ iv List of Tables ....................................................................................................................... x List of Figures .................................................................................................................... xi List of Acronyms ............................................................................................................. xvi Chapter 1 Introduction ......................................................................................................... 1 1.1 Motivation and Significance ...................................................................................... 1 1.2 Scope ......................................................................................................................... 3 1.3 Hypotheses ................................................................................................................. 3 1.4 Objectives .................................................................................................................. 4 1.5 Thesis overview ......................................................................................................... 5 Chapter 2 Literature review ................................................................................................. 7 2.1 Bark ........................................................................................................................... 7 2.2 Chemical composition ............................................................................................... 7 2.3 Bark phenolic compounds ......................................................................................... 8 2.3.1 Lignin .................................................................................................................. 8 2.3.2 Tannins ............................................................................................................... 9 2.4 Reactivity of bark phenolic compounds towards formaldehyde ............................. 11 2.4.1 Reactivity of lignin towards formaldehyde ...................................................... 11 2.4.2 Reactivity of tannins ......................................................................................... 12 2.5 Extraction and adhesive application of phenolic compounds from bark ................. 14 2.5.1 Motivation of using renewable biomass as the feedstock ................................ 14 2.5.2 Extraction of phenolic compounds from bark for phenolic resin synthesis ..... 15 2.5.3 Adhesive application of bark phenolic compounds .......................................... 20 2.6 Mountain pine beetle infested lodgepole pine ......................................................... 25 vi 2.7 Conclusions ............................................................................................................