Natural Oil Polyols (NOPs) or bio polyols are derivatives of vegetable oils. The making of polyurethanes is the primary use of NOPs. Despite having similar application and raw materials/sources the NOPs are quite different from each other depending on the method of production.
Physical and chemical property variations:
The physical differences start from colour which ranges from colourless to medium yellow, the viscosity differs as a working of the molecular weight and number of hydroxyl groups per molecule. The odour is also different from one another. Most NOPs are chemically like the vegetable oils from which they are derived; this also makes them prone to become rancid as the parent oils by autoxidation of the fatty acid chains comprising carbon – carbon double bonds. Odour is undesirable in NOPs as well as the products meant from them.
Commercialized Natural Oil Polyols (NOPs):
Castor oil is a NOP which is commercially available and the only one produced directly from a plant source, other NOPs require chemical modifications to the oils from plants. Due to the presence of hydroxyl groups that allow chemical derivatization, modification of properties of the castor oil in comparison to the vegetable oils is quite easy. In the process of producing polyurethanes the reaction of castor oil and diisocyanates is the most important.
Significance of castor oil and its derivatives:
The presence of hydroxyl groups has rendered these oils the front runner seat in terms of chemical derivatization of the oil or the easy modification of properties. Castor oil, amongst natural oil polyols has various applications. Castor oil undergoes various reactions that are quite similar to the pattern of alcohol’s reactions. However, the reaction of castor oil with diisocyanates to manufacture polyurethanes has been pondered industrially important. The production of polyurethane products like coatings and foams require the usage of castor oil. On the other hand, applications pertaining to the derivatives of castor oil have been remarked as an area of consistent significance for research and development. Foam for mattresses incorporate castor oil derivatized with propylene oxide.
Significance of other derivatives: