An Insight into Foam Rubber

An Insight into Foam Rubber

By Manufacturing Technology Insights | Tuesday, February 23, 2021

The molecular composition, quantity, and reaction temperature of each ingredient shall decide the characteristics and eventual use of foam. Therefore, each preparation must be formulated with the correct ingredients to obtain the final material's desired properties.

FREMONT, CA: Foam rubber is used in various uses, from cushioning in car seats and chairs and insulation in walls and fixtures to soles and heels in boots. Foams are created by forming gas bubbles in a plastic mixture using a blowing agent. The manufacturing of foam is either a continuous process for the production of laminate or slab stock or a batch process to produce different forms by cutting or molding.

There are two primary types of foam. Flexible foams possess an open cell structure and can be manufactured in high and low densities. Applications cover chair and automotive cushioning, mattresses and pillows, automotive trim, and shoe soles. Rigid foams are deeply cross-linked polymers with a closed-cell arrangement that avoids gas movements. They are primarily used as insulation for houses, refrigerators and freezers, and refrigerated transport vehicles.

Design

The molecular composition, quantity, and reaction temperature of each ingredient shall decide the characteristics and eventual use of foam. Therefore, each preparation must be formulated with the correct ingredients to obtain the final material's desired properties. For example, a switch in a blowing agent can need an increase in this additive to preserve thermal properties.

Growing the blowing agent volume requires additional water and a switch in surfactants to retain maximum bubble sizes and foaming speeds. The volume of blowing measures the foam density. The stability and hardness of polyurethane can also be changed by adjusting the amount of flexible polyol in the chemical formulation. By combining various variations of the starting materials, the reaction rate and the total cure rate can be regulated during manufacturing.

Raw Materials

Most foams consist of the following ingredients: 50 percent polyol, 40 percent polyisocyanate, and 10 percent water and other chemicals. Polyols and polyisocyanates are liquid polymers that, when mixed with water, create an exothermic reaction (heat generation), forming polyurethane. The two most widely used polyisocyanates are diphenylmethane diisocyanate (MDI) and Toluene Diisocyanate (TDI).

Weekly Brief

Read Also