[acs symposium series] chemorheology of thermosetting polymers volume 227 || preface

PREFACE

l o OBTAIN A SOUND SCIENTIFIC UNDERSTANDING of the processes by which thermosetting polymers cure is a difficult task because of the insolu­ble, cross-linked nature of these polymers as the cure reaches completion. Advances in instrumentation over the past 10 years now permit a greater comprehension of the complex character of these materials. Thermosetting polymers are rapidly gaining acceptance in areas that affect our lives on a daily basis: The automotive, aerospace, electronics, housing, and sporting goods industries are good examples. Increasing numbers of scientists are being attracted to thermoset resin studies that use nonempirical, scientific approaches.

The term chemorheology arises from the two areas of concern being studied. The first concern comes early in the cure. The processability or flow (rheology) of the polymer system is of primary importance because process changes such as heating rates, hold temperatures, or pressures normally are made during this early period. The other area of concern is the chemistry of the process: the rate of reaction, the mechanisms, the kinetics, and the cessa­tion of the chemical reaction or the end of the cure. The interactions between these two concerns are obvious because the rate of rheological change in either the liquid or solid state and the development of the optimum glass transition temperatures cannot be separated from the chemical contribution to these effects.

In this all too brief volume the reader will find how advances in liquid chromatography, differential scanning calorimetry, IR spectroscopy, and par­ticularly liquid and solid state rheology have contributed to a better under­standing of the curing of thermosetting polymers. Also discussed are the mathematical models being developed to describe and predict the chemical and physical events occuring during thermoset cure. The use of dielectric measurements to follow the chemical and rheological changes is also con­sidered. Since this volume was compiled, there appears to be a new wave of interest developing in this area.

The field of research on the chemorheology of thermosetting polymers is new and exciting. As our knowledge of the curing processes expands, new materials will come into focus. These too, must be understood. The reader should also look beyond the application of these methodologies to the ther­moset materials discussed herein, and use the information to develop further

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the techniques as they apply to his or her own problems. Because the area of thermoset polymers is complex, no particular technological skill dominates. Through cooperative efforts that knit these individual skills together, we can make rapid advances toward the evaluation of materials that afford the properties necessary to meet the needs of future generations.

C L A Y T O N A. M A Y Lockheed Missiles and Space Company, Inc. Sunnyvale, C A

May 1983

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1982

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In Chemorheology of Thermosetting Polymers; May, C.; ACS Symposium Series; American Chemical Society: Washington, DC, 1982.