Influence of Epoxidized Cardanol Functionality and Reactivity on Network Formation and Properties.

Cardanol is a renewable resource based on cashew nut shell liquid (CNSL), which consists of a phenol ring with a C15 long aliphatic side chain in the meta position with varying degrees of unsaturation. Cardanol glycidyl ether was chemically modified to form side-chain epoxidized cardanol glycidyl ether (SCECGE) with an average epoxy functionality of 2.45 per molecule and was cured with petroleum-based epoxy hardeners, 4-4'-methylenebis(cyclohexanamine) and diethylenetriamine, and a cardanol-based amine hardener. For comparison, cardanol-based diphenol diepoxy resin, NC514 (Cardolite), and a petroleum-based epoxy resin, diglycidyl ether of bisphenol-A (DGEBA) were also evaluated. Chemical and thermomechanical analyses showed that for SCECGE resins, incomplete cure of the secondary epoxides led to reduced cross-link density, reduced thermal stability, and reduced elongation at break when compared with difunctional resins containing only primary epoxides. However, because of functionality greater than two, amine-cured SCECGE produced a Tg very similar to that of NC514 and thus could be useful in formulating epoxy with renewable cardanol content.

Epoxidation of Cardanol's Terminal Double Bond.

In this investigation, the terminal double bonds of the side chain epoxidized cardanol glycidyl ether (SCECGE) molecule were further epoxidized in the presence of Oxone® (potassium peroxomonosulfate) and fluorinated acetone. Regular methods for the double bond epoxidation are not effective on the terminal double bonds because of their reduced electronegativity with respect to internal double bonds. The terminal double bond functionality of the SCECGE was epoxidized to nearly 70%, increasing the epoxy functionality of SCECGE from 2.45 to 2.65 epoxies/molecule as measured using proton magnetic nuclear resonance (1H-NMR). This modified material-side chain epoxidized cardanol glycidyl ether with terminal epoxies (TE-SCECGE)-was thermally cured with cycloaliphatic curing agent 4-4'-methylenebis(cyclohexanamine) (PACM) at stoichiometry, and the cured polymer properties, such as glass transition temperature (Tg) and tensile modulus, were compared with SCECGE resin cured with PACM. The Tg of the material was increased from 52 to 69 °C as obtained via a dynamic mechanical analysis (DMA) while the tensile modulus of the material increased from 0.88 to 1.24 GPa as a result of terminal double bond epoxidation. In addition to highlighting the effects of dangling side groups in an epoxy network, this modest increase in Tg and modulus could be sufficient to significantly expand the potential uses of amine-cured cardanol-based epoxies for fiber reinforced composite applications.

Investigation of PLLA/PCL blends and paclitaxel release profiles.

Blends of poly (L-lactide) (PLLA) and poly (ε-caprolactone) (PCL) with and without paclitaxel were prepared via solution casting. DSC analysis as well as SEM analysis of the PLLA/PCL blend solution cast films showed that these blends are all phase separated.%PLLA crystallinity was found to increase with increasing PCL content (up till 15 wt.%). The PCL phase is found to homogeneously disperse in the PLLA matrix as spherical domains where the pore diameters of the PCL domains significantly increased with increasing PCL content. The degradation profiles matched with the slower degrading component PCL rather than PLLA and also increasing PCL content of the blends increased the degradation rate relatively. The increased crystallinity of the PLLA phase with increasing PCL contents confirmed that the degradation occurred through PCL phase. Cell proliferation on PLLA/PCL blends showed that all these blends were suitable for the support of cellular growth. Apoptosis assay with the paclitaxel-loaded PLLA/PCL blends showed an increase in cell death throughout 7 days of incubation where the cell death was increased with increasing PCL contents. This was attributed to the faster release of paclitaxel which was at least partially affected by the faster degradation rate at increasing PCL contents. The paclitaxel release was shown to be degradation controlled in the initial stages followed by a faster diffusion-controlled release in the later stages. These polymer blends were found to be very suitable paclitaxel release agents for which the paclitaxel release times can be altered with the composition of the blend and the film thickness.