Here are some important points to be considered for foam applications

Comfort is extremely subjective and will defer from person to person.

• Foam alone is not the only factor influencing comfort. The location and combination of the foam is important in determining this comfort feature.
• Selecting the best foam for a job is difficult as is selecting a foam which will be durable in use.
• Most foam development is constricted by an allocated budget.
• In-use durability is a difficult and complex subject. However, commonsense, technical based methodology for choosing good, durable foam does exists.
• Environmental regulators have forced a need to reformulate many foams within the industry. Reformulation can potentially (sometimes) affect some physical properties, particularly hysteresis and flex fatigue.
• Density is one of the most important (with hardness) and misunderstood properties. It is sometimes referred to as though it was hardness. In fact foams of a given hardness can be made in many densities. The main reasons for this are mainly due for price and the application aspects, for durability concerns. For example: for a sofa, the seat cushion will have to be a higher density than the backing cushion; because the seat cushion will have a greater load upon it over time compared to the backing cushion. Hence density is directly related to durability while hardness or firmness of a cushion is related to the quality.

Therefore:

• Density is expressed in Kg/m3 and is simply the expression of weight or mass for a given volume of foam. Density is measured by first weighing the foam in grams and then measuring the dimension of the sample.
• Hardness (Indentation Force Deflection (IFD)) is measured using a standards test method in which the Australian method is slightly different from that used in the U.S.A. or other in-house used tests.

U.S.A.

The force in pounds required to indent a 50mm2 round indentor foot (hardness machine) into a 20" x 20" x 4" foam sample to 25% of the thickness.

Australia

(according to AS2282.8  1991 Method A) the force in Newtons to indent a 203mm diameter round indentor into a 380 x 380 x 50 (15" x 15" x 2") to 40% of the thickness.

It should be noted that sample size, in addition to thickness drastically affect IFD values so it is very important to report any deviation from standard test sizes.

The typical expression for describing a grade of foam is made in this fashion. For example a foam with a density of 25Kg/m3 and a IFD at 40% (according to Australian test method) of 100N will be written as 25-100 grade. This facilitates the cataloguing of all the different grades of foam available.

Some examples of IFD (at 40%) are recommended for use in particular function   >>>

Note:  years of experience, supported by considerable testing have given strong indications that foams with polymer densities of 30Kg/m3 or higher perform better in seating applications as opposed to foams with lower polymer densities.

The applications from the above table are only examples; application for foam is infinite. If you require any further information or clues on new product application do not hesitate to contact us. PUTech has an endless wealth of ideas.