Synthesis and characterisation of castor oil-urethane acrylate oligomers

Castor oil-urethane acrylate (CVA) oligomers have been synthesised and characterised by infra-red spectroscopy (FT-IR), gel permeation chromatography(GPC) to study the relationship between the reaction kinetics and the structure of the products. It is shown that the chain terminating reaction between 2,4-toluene diisocyanate (2,4TDI) and hydroxyethylacrylate (HEA) to form isocyanatoethyl acrylate (IEA) obeys a second order mechanism, as does the chain extension reaction of IEA and castor oil (CAS). From the data of the polymerisation rate constant and the apparent activation energy, it can be seen that the different structure of CVA oligomer is dependent mainly on the different reactivities of both para and ortho NCO groups in 2,4TDI. Whereas the apparent viscosity of the CVA oligomer is related to the structure of diisocyanates. Results from the dynamic mechanical spectrum (DMS, the abstract of dynamic mechanical spectrum, a kind of detection method) indicate that the hard segment content of oligomers is then increased up to 59% (wt.). A phase-separated structure is formed and leads to the highest tensile strength (18.2MPa). When the hard segment content is increased to 67% (wt.), the dynamic modulus is reduced and the single depletion peak from DMS is exhibited at the temperature of 100.7°C.