Influence of Vitamin E TPGS on the properties of hydrophilic films produced by hot-melt extrusion

Films containing hydroxypropylcellulose (HPC) and polyethylene oxide (PEO) were prepared using a Randcastle extruder (Model 750) with and without Vitamin E TPGS (TPGS, D-alpha-tocopheryl polyethylene glycol 1000 succinate) as an additive. Conventional plasticizers including polyethylene glycol 400 (PEO 400), triethyl citrate (TEC), and acetyltributyl citrate (ATBC) were also incorporated into films containing a 50:50 blend of HPC and PEG. The physical-mechanical properties including tensile strength (TS) and percent elongation (%E) were determined on an Instron according to the ASTM standards. Glass transition temperatures (T-g) of the extruded films were determined utilizing a DSC 2920 Modulated differential scanning calorimeter and THERMAL ANALYST 2000 software. Gel permeation chromatography was used to study the stability of the polymer films under the processing conditions. The addition of 1, 3, and 5% Vitamin E TPGS, respectively, decreased the glass transition temperature of the extruded films containing either a 50:50 or 80:20 ratio of HPC to PEO in an almost linear fashion. In addition, the presence of 3% Vitamin E TPGS lowered the T-g over 11 degrees C when compared with the HPC/PEO 50:50 blend film without TPGS, thus Functioning as a plasticizer. The tensile strength decreased with increasing concentrations of TPGS, and the %E increased over 3-fold when compared with the HPC/PEO film that contained no additives. The film cont;lining 3% Vitamin E TPGS had a similar tensile strength to that of the films containing 3% PEG 400, and a 3-fold increase in percent elongation when compared with the films containing 30% TEC and 3% ATBC. In addition, the Vitamin E TPGS facilitated the processing of the HPC/PEO films by decreasing the barrel pressure, drive amps, and torque of the extruder equipment. (C) 2000 Elsevier Science B.V. All rights reserved.