Bio-based and Renewable Plasticizers in Rubbers and Elastomers
Permanent address of the item is
Kumeissa ja elastomeereissä käytettävät biopohjaiset ja uusituvat pehmittimet
Rubbers used in automotive and tire industries are typically plasticized with mineral oils, which are derived from dwindling fossil sources. Furthermore, the use of certain mineral oils that contain polycylic aromatic hydrocarbons have been restricted in the European Union in the 21st century. Bio-based and renewable oils are considered as possible alternatives for petroleum plasticizers. An important class of bio-based oils are vegetable oils derived from plants and seeds of industrial crops. In addition to being renewable and bio-based, these vegetable oils have advantages of being well-known, their extraction methods are established at industrial scale and global production volumes are significant. Vegetable oils are triglycerides, which are esters derived from glycerol and fatty acids, and therefore give somewhat different properties in rubbers compared to mineral oils. Therefore, there has been significant research in the past decades to find how vegetable oils work as plasticizers, and what properties and advantages vegetable oils give in rubbers compared to mineral oils. In this thesis, the recent literature is reviewed regarding the bio-based plasticizers and focus is mainly on the vegetable oils. The review revealed that vegetable oils cause some common effects on properties of rubbers when compared to mineral oils. However, it was also found crucial to consider each rubber formulation individually, as vegetable oils have difference in details of chemical structure and rubbers are complex mixtures of 5-15 chemicals. Despite the complexity of rubber formulation, there has been some success of using alternative vegetable oils in commercial rubbers like automotive tires, which indicates that the research to these alternative bio-based oils have economical and environmental benefits.