Establishment and properties of epoxidized natural rubber-graft-poly(N-vinylcaprolactam)/poly(vinyl alcohol) blend

Abstract

Green polymer is made from epoxidized natural rubber (ENR) latex (natural polymer plant), N-vinylcaprolactam (NVCL), and poly (vinyl alcohol) (PVA). Firstly, NVCL was grafted onto the ENR using potassium persulfate as an initiator and its chemical structure was confirmed using ATR-FTIR and 1H NMR. The graft copolymer occurs at amorphous (non-crystalline) region confirmed by XRD. The sharp peak XRD patterns of the ENR-graft-NVCL were found at 24.82, 30.63, 31.18, 37.16, 39.62 and 43.73°, referred to the reflection of (0 0 4), (1 0 1), (1 0 3), (1 1 0), (1 1 2) and (2 0 1), respectively. XRD pattern of the ENR was observed at 2θ = 19.5°, which is amorphous portion. It was then blended with PVA to reduce the swelling ratio in the toluene medium, the moisture content and moisture absorption of the ENR-graft-NVCL/PVA blend, reduced as a function of NVCL (200%, 3% and 7%, respectively) because of its chemical interactions. Moreover, the ENR-graft-NVCL swelled 150% or about 8 times based on the pristine ENR in water medium. The lower critical solution temperature of the ENR-graft-NVCL/PVA blend was observed around 37 °C. The highest tensile strength (around 14 MPa) was observed with NVCL at 1.5 phr. The ENR-graft-NVCL showed the highest thermal stability. A sustained release profile of curcumin from this matrix was found and the release percentage of the loaded curcumin sample at 40 °C and 72 h was much lower than the release percentage of the sample at 25 °C. The biodegradation of ENR-graft-NVCL/PVA blends (25–45%) degraded in natural soils.