Handbook of Adhesives and Sealants

General Knowledge, Application of Adhesives, New Curing Techniques

Philippe Cognard

• Publisher: Elsevier Science
• Year: 2006
• Topic: Technology & Engineering
• eBook ISBN:
  9780080460598
• Subtopic: Chemistry
• Index: Chemistry

Contributions from more than 60 authors, each a well-known specialist in their field, have been co-ordinated to produce the most comprehensive Handbook of Adhesives and Sealants ever published. The handbook will be published as 8 volumes, over a period of 4 years and will contain over 2800 pages, rich with case studies, industrial applications and the latest research. It is a work in progress, enabling the latest new and important applications to be included as they happen. Volume 2 of Elsevier's Handbook of Adhesives & Sealants Series, General knowledge, application of adhesives & new curing techniques, covers the mechanisms of adhesion, its application, and drying and curing techniques. The volume is divided in to the following sections: • Theory of adhesion • Metering and dispensing • Design and calculation of bonded joints• Heat stable adhesives• UV curing • Flexible bonding and sealants Each contributing author is a scientist, practitioner, engineer, or chemist with an abundance of practical experience in their respective field, making this text an authoritative reference source for any materials scientist or engineer, whether in academia or industry.

Chapter 1

Theories of Adhesion

John Comyn

Abstract

Studied chemistry at Bristol University (BSc 1964) and physical chemistry at Leeds and Belfast Universities (PhD Leeds 1967) and then appointed to teach polymer chemistry at Leicester Polytechnic. Resigned in 1989 to work as a consultant but became a visiting fellow at Loughborough University and a visiting professor at De Montfort University (formerly Leicester Polytechnic). Awarded a DSc by Bristol University in 1994. For many years has been joint editor-in-chief of the International Journal of Adhesion and Adhesives.

Keywords

Adhesion by chemical bonding

Adhesion by diffusion

Contact angle

Contact mechanics

Covalent bonds

Critical relative humidity/water concentration

Electrostatic theory

Hydrogen bonds

Ionic forces, ion-pairs

Latex adhesives

Lewis acids and bases

Other coupling agents

Physical adsorption

Pressure sensitive adhesion

Silane coupling agents

Surface tension

Water sensitivity

Wetting

Wood

Work of adhesion

1.1 Introduction

An adhesive must do two things when applied to surfaces which are to be bonded. It must first wet the surfaces, as manifested by spreading and making a contact angle approaching zero. It must then harden to a cohesively strong solid.

Wetting involves making intimate contact between the molecules of the adhesive and the atoms and molecules in the surface. Hardening can be by chemical reaction, loss of solvent or water, or by cooling, but there is an exception in the case of pressure sensitive adhesives which remain permanently fluid. When this intimate contact is made, van der Waals forces are built, but other intermolecular forces such as chemical bonds may be formed at the time of contact or during the hardening process. However, this will depend on the chemistry of the adhesive and the substrate. If the adhesive can penetrate into the substrate before hardening, then mechanical interlocking will contribute to the strength of the adhesive bond. Intertwining of polymer molecules in the adhesive with those in the substrate would be the result of molecular interdiffusion across the interface. These four phenomena underlie the physical adsorption, chemical bonding, mechanical interlocking and diffusion theories of adhesion.

There are two further theories namely electrostatic theory and weak boundary layer theory. All are discussed in detail below.

1.2 Adhesion by Chemical Bonding

The chemical bonding theory of adhesion invokes the formation of covalent, ionic or hydrogen bonds or Lewis acid–base interactions across the interface. Typical strengths of these bonds are shown in Table 1, where they are compared with van der Waals forces, which are the source of physical adsorption. The interactions are listed roughly in the orde...

Table of contents

• Cover image
• Title page
• Table of Contents
• Copyright page
• Preface to Volume 2
• Chapter 1: Theories of Adhesion
• Chapter 2: Equipment for the Application of Adhesives and Sealants: Mixing, Metering, Coating or Applying the Adhesives
• Chapter 3: Design and Stress Calculations for Bonded Joints
• Chapter 4: Heat-Resistant Adhesives
• Chapter 5: UV-Radiation Curing of Adhesives
• Chapter 6: Elastic Bonding and Sealing in Industry
• Index