COLORED PLASTICS BASED ON STARCH?CURCUMIN INCLUSION COMPLEXES AND POLY(VINYL ALCOHOLS) FOR ENVIRONMENTALLY FRIENDLY SMART PACKAGINGS

• Main Author: Siti Nurjanah, Cica
• Format: Final Project
• Language: Indonesia
• Subjects: Kimia
• Online Access: https://digilib.itb.ac.id/gdl/view/87260
• Institution: Institut Teknologi Bandung

Plastic waste that is difficult to degrade encourages the search for substitute materials to replace plastics. Starch has high potential as a bioplastic material because it is easy to renew, inexpensive, and biodegradable. However, applying starch as a bioplastic has drawbacks because the plastic tends to be brittle, rigid, and has low tensile strength. Curcumin can be utilized as a guest molecule forming a complex with starch as the host molecule. This aims to improve the mechanical properties of plastics and allow plastics to change color due to changes in pH. This study aims to formulate a mixture of starch?curcumin (PK) and poly(vinyl alcohol) (PVA) complexes as smart and environmentally friendly packaging bioplastics. The plastic is made by mixing starch and curcumin at 86 °C for 2 hours with variations in curcumin concentrations of 3, 5, and 7% (b/b based on complex weight). The complex is mixed directly with PVA with weight ratios of 2:1, 1:1, and 1:2 (PK:PVA). Then, 25% glycerol plasticizer (b/b based on plastic weight) and 1% citric acid (b/b based on plastic weight) are added to the mixture. The mixture is sonicated for 20 minutes and degassed for 10 minutes at 70 °C. After that, the mixture is molded and left for 24 hours at room temperature, followed by drying in the oven at 45 °C. The resulting plastic film is characterized by atomic force microscopy (AFM), FTIR, X-ray diffraction (XRD), and thermogravimetry (TGA) analysis. Further characterization of plastics includes mechanical properties, contact angles, swelling degrees, water absorption, burial in the soil, and storage tests in solutions of various pHs. PKPVA plastic film has a yellow-orange color that tends to be evenly distributed for the PK:PVA weight ratio of 1:1 at all variations in curcumin concentration. The FTIR data showed that the complex was successfully formed based on the loss of the C=O vibration absorption signal, which indicates that curcumin has entered the amylose canal. XRD data shows that PKPVA plastic has a semicrystalline structure, whose crystallinity increases along with the increase in the amount of curcumin and PVA. TGA data shows that increasing the amount of PVA can increase the thermal stability of PKPVA plastics. This shows that the amount of curcumin does not have much effect on the thermal stability of plastics. Mechanical property test data show that increasing the amount of PVA can increase the tensile strength and elongation of plastics. Plastics with a starch?curcumin complex of 5% produce mechanical properties with a tensile strength of about 2,54?3,88 Mpa and elongation in 28,90?297,50% range. Increasing the amount of PVA can increase Young's Modulus from 9,09 Mpa to 27,56 MPa. Contact angle data shows that plastics become more hydrophobic as the curcumin and PVA contents increase. The swelling degree of PKPVA films in water tends to decrease when curcumin and the amount of PVA are higher (from 256.36% to 111.39%). The plastic storage test at a relative humidity of 53% showed an increase in the mass of PKPVA film from the 3rd to the 9th day, caused by water vapor absorption. The decrease in the mass of PKPVA film on the 14th to 28th days occurred due to the retrogradation process which caused an increase in crystallinity and made it difficult to absorb water. The soil plastic burial test with the PK:PVA weight ratio of 2:1 and starch?curcumin complex of 5% showed a mass reduction of up to 85% on the 7th day, which indicates that the plastic can decompose naturally in the environment. The plastic storage test in the solution showed that the plastic was red at pH 9, and yellow at pH 4. Thus, PKPVA film has great potential as an environmentally friendly plastic and can be used as a smart packaging that can detect food spoilage through pH changes.