Three different types of benzyl ester were synthesized from vegetable oils (i.e., coconut oil, palm oil, and soybean oil). They were then utilized in styrene butadiene rubber (SBR) compound reinforced with carbon black. First, the benzyl esters were investigated by varying the molar ratio of fatty acids in vegetable oil to benzyl alcohol, the catalyst concentration, the reaction time, and the reaction temperature, observing the yield of benzyl ester. Then SBR was compounded with the benzyl esters, observing cure characteristics, mechanical properties, and morphologies of the SBR compounds, with the control compound containing conventional aromatic oil. The highest 96% yield of benzyl ester was obtained with palm oil fatty acid. Furthermore, the benzyl ester oils consumed less energy during processing but gave comparable carbon black dispersion, in comparison with the conventional aromatic oil. C
The aims of this study were to formulate 5% lidocaine-loaded transdermal patches using STR-5L block rubber as a main component of the patch base and to investigate their physicochemical characteristics, in vitro drug release, and stability. The results suggested that STR-5L block rubber could be feasibly used as a main component of the base of pharmaceutical transdermal patches with acceptable physicochemical properties. STR-5L block rubber patches containing lidocaine exhibited lower moisture absorption when compared with the blank counterparts because the drug molecules inserted between the polymer chains. Lidocaine still showed its own crystallinity characteristics after crushing and mixing in STR-5L block rubber patches. Additionally, no chemical interaction between the drug and polymer base was found. The drug-loaded patches could provide drug release with the best fitted to Higuchi square root of time. They had good stability during the studied period of 3 months when kept at 4 °C.
The mucous liquid of Hevea brasiliensis or Para rubber tree, called natural rubber latex (NRL), composes of cis-1,4-polyisoprene which can form a patch under suitable formulation. In this study, blank and 5% lidocaine-loaded NRL patches were formulated and then characterized for physicochemical properties as well as evaluated in vitro drug release and stability. The patches were observed for their appearances. Surface morphology of the patches was investigated using a SEM. XRD was employed to study the crystallinity of the drug, the patch, and the drug-loaded patch. The extractions of lidocaine-loaded patches were analyzed for drug contents by HPLC. In vitro drug release study was performed using modified Franz diffusion cells. The patches at initial preparation and after kept at 4, 25, and 45 °C for 3 months were investigated for the stability determination. The results suggested that NRL could be used as a main component in pharmaceutical transdermal patches with acceptable physicochemical properties. Lidocaine-loaded NRL patches provided desirable drug release but high storage temperatures could age the patches resulting in darken color and lower release amount.
Benzyl esters of fatty acids based on three types of vegetable oils (i.e., coconut, palm, and soybean oils) were in-house prepared. They were used as alternative rubber processing oil to replace conventional aromatic oil which has been banned by European community since December 2009. Fatty acids were first prepared by hydrolysis of vegetable oils and thereafter esterified with benzyl alcohol in the presence of sulfuric acid as a catalyst. The reaction based on molar ratio of fatty acid:benzyl alcohol:sulfuric acid was set at 1.5:1.0:0.05 gave yield of benzyl esters higher than 80%. Rubber compounds containing different types of benzyl ester were prepared according to the standard formulation of ASTM 3184. It was found that the processing oil in the form of benzyl esters is possible to use instead of aromatic oil in rubber formulation. Various parameters and properties include mixing energy, Mooney viscosity, curing, mechanical and dynamic mechanical properties of rubber compounds and vulcanizates have been investigated.
Modified benzyl esters from coconut, palm, and soybean oil were used as alternative rubber processing oil to replace distillate aromatic extract oil (DAE). The effect of benzyl esters on mixing, curing properties, polymerfiller interaction and Mooney viscosity was investigated in silica filled natural rubber compound. Benzyl ester oil was found to be effective processing oil with decreasing of mixing energy and Mooney viscosity. Furthermore, it was found that coconut and palm benzyl esters showed higher torque difference than the aromatic oil filled compound. Also, benzyl ester oil gave similar level of cure time and dynamic properties compared with the rubber compound with aromatic oils.
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