Introduction

Polyurethane viscoelastic foam, also known as memory foam and low-resilience polyurethane (LRP), was developed for airplane cushions by NASA. At the end of the last century, it was commercialized by a multitude of polyurethane manufacturers and gradually entered ordinary consumers’ life.

The mechanism of conventional VE foam lies on its mechanical characteristics that the strain lags behind the change of stress, so the stress has a relaxation process, and the comfort level of the foam depends on this unique stress-strain relationship. This uniqueness makes the VE foam mold to the shape of the human body, maximizing the contact area to redistribute weight and surface pressure, which leads to its popularity in bedding products such as mattresses and pillows.

JIAHUA is a multinational company dedicated to comfort sleep technology. Puranol™ polyether polyols for VE foam provide a full range of healthy and comfortable sleep solutions globally.

Mechanism Analysis

From the below tanδ curve, we can see that the conventional VE foam presents a glassy state at low temperature, a viscoelastic state at room temperature and a rubbery state at high temperature. When the temperature becomes lower, the foam will get stiff and when the temperature becomes higher, the foam will bounce back faster and lose the "handprint" effect.

JIAHUA Conventional TDI based VE Foam Solutions

Foaming Test based on Puranol VE7321 and Puranol VE7325

From the formulation design and foaming test of conventional TDI VE foam based on VE7321 and VE foam based on VE7325, their physical properties are as follows:

4.1 Airflow performance and compression set test

From the airflow and compression set test, we can see that compared with conventional TDI VE polyol VE7321, VE7325 has better airflow performance and compression set resistance. As a result, using VE7325 can reduce the amount of cell open additives and the dependence on silicone surfactants. Also, combining VE7321 with VE7325 is a good choice, as the foam performance will be better, including the time to recover from deformation and compression hardness.

4.2 Cell structure - Observation 

We observe the cell structures of these two conventional TDI based VE foam as follows: