New bio-based polyols for the improvement of structural adhesives based on epoxidized naturals oils

 
Epoxidized natural oils can be cured by cationic polymerisation or polyaddition with anhydrides. Unfortunately, the properties of the cured polymers are often not sufficient for the use as structural adhesives. If cationic polymerisation is used for adhesive curing the properties can be adjusted by polymeric alcohols. Typically polypropyleneglycols are applied for this purpose. Unfortunately, they lead mainly to softer but less strong adhesives and are not biobased which would be preferred in combination with epoxidised natural oils. Therefore, we developed a new biobased class of polyols based on lactic acid and for which pronounced toughening instead of just softening the cured adhesives is observed. If formulated with epoxidised oils and sufficient curing initiators the new polyols lead to tough structural adhesives which can be cured thermally as well as photochemically.