by Erich Klein and Osamu Yoneji, Kuraray America
Plasticizers are one of the key components of the rubber and adhesives industries. Plasticizers are used to lower hardness, improve processability and reduce raw material costs. On the other hand, mechanical properties deteriorate with plasticizer content. In addition, plasticizers often cause changes in properties with time and staining due to volatilization or bleeding. Phthalate plasticizers and aromatic oils are or possibly will be regulated due to environmental and human health issues. Kuraray liquid rubbers (KLR) are plasticizers which are co-vulcanizable with solid rubbers. Therefore, it is very unlikely that KLR will be subject to these bleeding or volatilization issues. As a result, KLR is expected to have a growth potential as an environmentally friendly plasticizer.
Characteristics of Kuraray liquid rubber – KLR is a low molecular weight polydiene. The molecular weight is designed between a typical solid rubber and plasticizer, as shown in figure 1. KLR, therefore, has characteristics of both rubbers and plasticizers, namely co-vulcanizability with solid rubbers and excellent plasticizing effects. The liquid rubber is called a “reactive plasticizer” due to these properties.