The Complete Handbook of Elastic

Chapter 1: Understanding Elastic

What Elastic Actually Is

Elastic is a material that can be stretched to at least twice its original length and will return to its approximate original dimensions when the stretching force is removed. That definition sounds simple, but it conceals a complex engineering problem. The material must be soft enough to stretch easily, strong enough to resist tearing, and durable enough to survive years of repeated cycles. It also must be manufacturable in long, continuous lengths and compatible with cutting, stitching, and gluing. The result is a family of products that vary widely in construction, performance, and cost, and it is a mistake to treat them as interchangeable.

At the heart of nearly every elastic product is a material with a property called elasticity. Natural rubber, synthetic polyisoprene, and spandex (also known as elastane or Lycra, a brand name) share this property at the molecular level: their long polymer chains are coiled and cross-linked. When you stretch the material, those chains uncoil and slide past one another. When you release the tension, the cross-links pull the chains back to their original tangled arrangement. This is what gives the material its "snap". The construction of the elastic - whether it is woven, knitted, braided, or extruded - determines how that spongy core is protected, supported, and attached to your project.

The practical consequence is that elastic is never just "stretch." A piece of elastic is a system of load-bearing strands, protective fibers, and structural geometry. Changing any