Foam Rubber Basics
Latex foam rubber is the general term used to describe latex foam rubber produced with a large enough cross section to be used for mattresses, pillows, and cushions. Block latex foam rubber is produced by two different processes; the Talalay Process, and the Standard (Dunlop) Process. Both processes use the same basic ingredients, but many producer use different % of each; natural rubber latex (NR), polystyrene-butadiene rubber latex (SBR), soap, reinforcing filler, sulfur, and vulcanization agents.
Natural Rubber Latex – Naturally occurring polyisoprene polymer produced by rubber trees and extruded in the sap. The rubber tree sap is collected, concentrated, and preserved with ammonia before being sold.
Polystyrene-butadiene Rubber Latex (SBR) – Polymer produced from styrene and butadiene designed to mimic and improve upon natural rubber. The polymer is produced in water on both batch and continuous production lines. After polymerization, the latex is stripped of residual reactants and concentrated before being sold.
Soap – Natural soaps are used to stabilize the various components in the mixture.
Reinforcing Filler – Hard materials are added to the mixture to increase firmness. Reinforcing fillers are of two general types; mineral or plastic. Mineral fillers are generally aluminosilicates such as Feldspar or calcium carbonate (talc). The most commonly used plastic filler is polystyrene resin. Plastic fillers are typically introduced as a latex and tend to form clusters in the rubber matrix. The plastic clusters are prone to breaking apart under use leading to softening.
Sulfur – Elemental sulfur forms crosslinks between polymer chains when heated giving the latex rubber foam strength and structure.
Vulcanization Agents – Agents used to increase the crosslinking rate and effectiveness of sulfur. The agents are typically consumed in the process.
The above components are mixed together in a water based system to form what is termed compound for both processes.