Polyurethane Foam Foaming Common Terms

Cold Cure

A process for seat foam production, which produces high resilience foam (referred to as HR foam).

During this process, the mold temperature is generally between 50-70 degrees Celsius; the polyether molecular weight is typically between 2500-6500, and the ISO can be TDI/TM/MDI.

This process has high production efficiency, low energy consumption, and is currently widely used.

Pump Capacity

Used to check the stability of the metering pump flow output.

The current method for verifying pump capacity is as follows: at the set flow rate, shoot continuously 35 times, weigh each shot, then calculate the capacity. Based on the pump capacity, determine whether the metering pump needs repair or replacement. Generally, pump capacity is checked every three months.

Pump Linearity

A characterization of the correlation between the metering pump's speed and output.

Usually, five different speeds are selected for flow testing. The output of the metering pump at each speed is then obtained. If these five points align on a straight line, it indicates good linearity between the metering pump's speed and output.

NBT (New Blending Technology)

NBT stands for New Blending Technology.

The previous blending technology involved spraying and mixing one ISO with one POL to react and produce polyurethane foam. When adjusting process parameters with this method, only the POL/ISO mixing ratio and the casting weight could be adjusted, with no other adjustments possible.

NBT involves spraying and mixing one ISO with 2 or 3 groups of POLY materials to react and produce polyurethane foam. (Equipment requires a frequency converter)

NBT can adjust the following variables: formula moisture, formula solids content, formula index, casting weight, and other variables. This allows for greater process tolerance when manufacturing foams of different densities and hardnesses.

TPR (Timed Pressure Release)

TPR stands for Timed Pressure Release, also known as venting or pre-venting.

Typical TPR parameters are: venting starts around 90-120 seconds after mold closure, with the bag dropping down, venting for about 2 seconds, then the bag rising back up.

Common phenomena: Venting too early can result in tender products prone to tearing. Venting too late can lead to stiff products prone to shrinkage after demolding.

Initial Spray

At the start of normal pouring, the ISO and POLY nozzles are opened simultaneously, allowing the materials to mix in the mixing chamber and react to produce polyurethane foam.

If during pouring the ISO and POLY nozzles do not open simultaneously, the one that opens first will cause the material to flow out of the mixing chamber without reacting, resulting in unreacted material at the beginning of the foam. If polyether comes out first, the foam will be sticky and wet at the top (mild initial spraying), while if ISO comes out first, the foam will be crispy, locally thin (mild initial spraying), or have ISO spots (severe initial spraying).

Common phenomena: Another special case is when there is softness at the initially poured area, which could also be a form of initial spraying. This might be due to the component coming out first, causing the foam at the initial pour point to be soft.

Foaming Index

When ISO and POL react, if they react in the exact theoretical amounts, it's called stoichiometric reaction, and the foaming index is defined as 100.

Foaming Index = Actual ISO usage/Theoretical ISO usage * 100. Currently, the foaming index for seat foaming is generally between 90-105.

As the foaming index increases, the foam gradually becomes harder.

Index > 105, the product is prone to being brittle; Index < 85, the product is prone to closed-cell shrinkage.