Polymers: Structure and Temperature

Welcome to Johns Hopkins Engineering: Manufacturing Systems Analysis

Polymer Properties: Structure and Temperature

Chapter 7: Polymers: Structure, General Properties, and Applications

This chapter explores the foundational aspects of polymers, including their structure, how they are formed, their general properties, and various applications. Specific topics covered include:

  • Introduction to polymers.

  • The fundamental structure of polymers.

  • Detailed examination of thermoplastics and thermosetting plastics.

  • The role of additives in plastics.

  • General properties and applications for both thermoplastics and thermosetting plastics.

  • An overview of biodegradable plastics.

  • Discussion of elastomers and gels.

Examples throughout the chapter provide practical context, such as:

  • Dental and Medical Bone Cement.

  • Materials used for a Refrigerator Door Liner.

7.1 Introduction to Polymeric Materials

  • Polymeric materials are characterized by their extremely large molecules, which allow for a diverse range of properties and characteristics.

  • These diverse properties enable polymers to be used in versatile engineering applications.

  • Comparison to Metals:

    • Polymers generally have much lower strength and stiffness values compared to metals.

    • However, polymers can exhibit significantly larger elongation values, in some cases quite substantial, which is a key distinguishing characteristic.

  • Types of Polymers: Polymers encompass both natural and synthetic organic materials.

  • Table 7.1 (Mechanical Properties):

    • The first part of Table 7.1 presents strength, stiffness, and elongation data for typical engineering thermoplastics.

    • The second part of Table 7.1 provides similar data for thermosets and elastomers.

      • Thermosets typically offer substantially lower elongation compared to thermoplastics.

      • Reinforced epoxy, a type of thermoset, can offer ultimate tensile strength superior to many engineering alloys.

      • Elastomers are characterized by very limited strength and stiffness but offer dramatically higher elongation levels than virtually all other materials.

Outline of Chapter 7 Topics (F7.1)

  • The formation of polymer molecules begins with a