Bismaleimide and Cyanate Ester Based Sequential Interpenetrating Polymer Networks for High Temperature Application A Thesis Submitted to the Faculty of Drexel University by Xing Geng in partial fulfillment of the requirements for the degree of Doctor of Philosophy January 2005 © Copyright 2005 Xing Geng. All Rights Reserved. ii DEDICATIONS This dissertation is dedicated to my parents, Mrs. Cao Xixian and Mr. Geng Yaozong, my wife Tie Liu, as well as my daughter, Helen, for their understanding and encouragement. What I cannot create, I do not understand. — Richard P. Feynman iii ACKNOWLEDGMENTS If my work achieves recognition, it will be because of the indispensable help that I have received. In particular, I would like to acknowledge valuable suggestions, advice and assistance from my advisor, Dr. Giuseppe R. Palmese, who made my pursuit of a Ph.D. enjoyable and profitable. I am also very grateful to my dissertation committee members, Dr. Charles Weinberger, Dr. Anthony Lowman, Dr. Steve Wrenn as well as Dr. Frank Ko for their efforts in guiding my research. Dr. Klosterman of the University of Dayton has provided a great deal of help in EB facility utilization. Thanks are also due to my group members, John La Scala, Jason Robinette, Vijay Raman, Jihean Lee, Mary Sullivan, Mohamed Aflal, Amutha Jeyarajasingam, for their kind help and encouragement. In particular Jason and Jihean provided great assistance with the EB kinetics study and measurement of mechanical properties. I would also like to express my appreciation to my fellow graduate students, in particular Dr. Veena Pata, Dr. Manasa V. Gudheti, Jonathan Ayutsede and Lei Lou for their kind support. Special thanks are given to my dear friend Dian S. Zhou and his wife Wei Zheng who made my life here friendly and enjoyable. I would like to acknowledge the administrative assistance provided by Dorothy Porter and the technical assistance provided by Dan Luu. Particularly, many thanks are also due to Orit Darwish and professor George for their kind help with draft revisions. I gratefully acknowledge the financial support that I received from Drexel University, iv NASA NCC3-784 [Dr. Michael Meador, Program Monitor] and AFOSR F49620-02-1- 0360 [Dr. Charles Lee, Program Monitor]. Someplace in China far away from here, I owe a considerable debt to my parents, Mrs. Cao Xixian and Mr. Geng Yaozong, as well as my daughter, Helen Geng. My wife Tie has been wonderfully patient in the face of many late nights and early mornings. v TABLE OF CONTENTS LIST OF TABLES............................................................................................................. xi LIST OF FIGURES ......................................................................................................... xiii ABSTRACT................................................................................................................... xxiv CHAPTER 1: INTRODUCTION.......................................................................................1 1.1 Motivation and Objective .................................................................................1 1.2 Outline of This Dissertation..............................................................................4 List of References ....................................................................................................6 CHAPTER 2: MOTIVATION AND LITERATURE REVIEW........................................7 2.1 Overview of High Temperature Composite Materials......................................7 2.1.1 Evolution of high temperature thermosetting polymers .......................7 2.1.2 Processing techniques for high temperature polymer composite fabrication..........................................................................12 2.2 Structure-property-processing Relationship of Bismaleimides ....................13 2.3 Current Research Activities Involving Bismaleimide Modification ..............14 2.3.1 Modification of bismaleimide to improve toughness .........................14 2.3.1.1 Modification with diamines ...................................................16 2.3.1.2 Modification with epoxy resin...............................................17 2.3.1.3 Modification with olefinic compounds..................................17 2.3.1.4 Modification with thermoplastics ..........................................18 2.3.1.5 Toughening with cyanate ester resins....................................18 2.3.2 Modification of bismaleimides to improve processibility ..................21 vi 2.3.2.1 Modification with olefinic compounds..................................22 2.3.2.2 Modification with cyanate ester resins ...................................26 2.4 Interpenetrating polymer networks (IPNs) .....................................................28 2.4.1 Morphology of IPNs ...........................................................................29 2.4.2 Physical and mechanical behavior of IPNs.........................................31 2.4.3 Synthetic routes...................................................................................32 2.4.3.1 Simultaneous IPNs.................................................................32 2.4.3.2 Sequential IPNs......................................................................33 2.5 Disadvantages of Current Technology and Significance of Our Study..........34 List of references....................................................................................................36 CHAPTER 3: SYNTHESIS AND STRUCTURAL CHARACTERIZATION OF BMI- CE IN-SITU SEQUENTIAL IPNs ............................................................45 3.1 Introduction.....................................................................................................45 3.2 Experimental...................................................................................................45 3.2.1 Materials .............................................................................................45 3.2.2 Preparation of sequential IPNs and LIPNs .........................................46 3.2.3 Preparation of simultaneous IPNs and LIPNs ....................................47 3.2.4 EB irradiation......................................................................................48 3.2.5 Chemical and physical characterization..............................................48 3.3 Results and Discussion ...................................................................................49 3.3.1 Selection of cyanate ester resin and appropriate catalyst....................49 3.3.2 Selection of reactive diluent................................................................53 3.3.3 Synthetic route of sequential IPNs and LIPNs ...................................54 3.3.4 Verification and significance of sequential IPNs................................58 vii 3.3.5 Importance of synthetic route ― sequential versus simultaneous IPNs .............................................................................62 3.3.6 Behavior of IPNs.................................................................................63 3.4 Summary.........................................................................................................65 List of references....................................................................................................68 CHAPTER 4: CATALYSIS AND HYDROLYSIS OF LECY........................................69 4.1 Experimental...................................................................................................70 4.1.1 Materials .............................................................................................70 4.1.2 Instruments..........................................................................................71 4.1.3 Preparation of LECY sample and hydrolysis study............................71 4.1.4 Water uptake study .............................................................................72 4.2. Results and Discussion ..................................................................................73 4.2.1 Catalysis by metal and the influence of AMP on the conversion of LECY ..........................................................................73 4.2.2 Influence of catalyst on BMI and AMP stability................................75 4.2.3 Influence of catalyst on the thermal degradation and hydrolysis of LECY ............................................................................80 4.2.4 Comparison of water uptake behavior of LECY and BACY .............90 4.2.5 Determination of processing conditions ― LECY cure kinetics........95 4.3 Summary and Conclusions ...........................................................................100 List of References ................................................................................................102 CHAPTER 5: N-ACRYLOYLMORPHOLINE—A UNIQUE REACTIVE DILUENT FOR BMI COPOLYMERIZATION .......................................................105 5.1 Introduction...................................................................................................105 5.2 Experimental.................................................................................................105 viii 5.2.1 Materials ...........................................................................................105 5.2.2 Instruments and methods ..................................................................107 5.2.3 Electron beam curing parameters......................................................108 5.3 Results and Discussion .................................................................................108