Polypropylene / organoclay nanocomposited for pH-sensitive packaging

Abstract

The processing of pH-sensitive material used fo milk packaging based on polypropylene/organoclay nanocomposites incorporated with indicator dyes was focused on. The nanoclay composites with indicator were compounding through a twin screw extruder using Surlyn as a compatibilizer. The nanoclay composites were fabricated into the sample sheet for the color testing and characterizations including thermal and mechanical properties. Milk deterioration was assessed for titratable acidity (TA), and color changes of the films were measured and expressed as Hunter values as well as total color difference (TCD). TCD values of BMB (Bromothymol blue) type- and BP (Bromocresol purple) type-films also changed continuously with the response of the film. The color changes of the films correlated well with TA value of fresh milk. According to the changes in Hunter color values of the films within the packages of fresh milk during storage at ambient temperature, the result shows that the color of BMB type-film turned from green to yellow whereas those of BP type-film turned from violet to green. The changes of the developed indicator properly represented the degree of deterioration of fresh milk. Consquently, the nanocomposite indicator film could be employed an effective smart packaging technology for evaluating fresh milk.