For the past times, the sponge foam has been classified as 3 categories by the density of the foam which is noted as kg/m3, that is, the weight per cubic meter of the sponge. Generally speaking, the foam we use most are classified as high-density foam, medium density foam and low-density sponge. According to the national custom department’s explanation, high-density foam are those that density ≧45 kg/m3, medium density foam are those density rank between 18 to 45 kg/m3, while the foam whose density ≦18 kg/m3 are named as low density foam.
High density sponge foam usually have a lot of pores, very plump and the hardness are generally high. But there also some high density foam feel very soft as some ultra soft sponge additives are added, these foam are made for sound-absorbing foam, sofa cushions and soft packing material. Medium density and low density foam are used as general protective material. The hardness of the same density sponge is not the same.
Nowadays, with the sponge manufacture technology improved, simply comment the foam by the density method is no longer desirable. In fact, the new high-density foam are much lighter than previous ones. Thus, we introduce a more professional and technical standards for evaluation, that is PPI.
PPI refers spongy per square inch (pore per inch). The PPI index higher, the foam softer; The PPI index lower, the foam harder. Spongy is mesh-like, nested body can be observed with a microscope. The larger nest hole is, PPI index get lower and the sponge become harder (spongy per square inch is smaller)
The foam swab manufactured by Meditech Technology Co., Ltd used with 100 PPI polyurethane foam whose hardness is appropriate and PPI index is reasonable, so as to minimize the fibers shedding from the swab while maintain a normal adsorption capacity. Except the PPI standard, we also refer to the ordinary density standards. For our cleanroom foam swab, we provide both high density foam and medium density foam as head material, whose density listed as 45 kg/m3 and 30 kg/m3. Customers may choose different polyurethane foam according to their specific conditions.
