The Effect of Spent Coffee Grounds (SCG) as a Natural Filler on the Physio Mechanical Properties of Polyvinyl Alcohol (PVA) Films

Abstract

Polyvinyl alcohol (PVA) is a biodegradable polymer that is safe, colorless, odorless, and non-toxic. It forms strong, flexible, and translucent films, making it highly suitable for various applications such as packaging, adhesives, and coatings. However, despite its excellent swelling capacity, PVA is highly sensitive to water due to the presence of hydrophilic hydroxyl groups in its side chains. This study investigates the incorporation of spent coffee grounds (SCG) as a natural filler to enhance the physio-mechanical and water-resistance properties of PVA films. PVA/SCG composite films were fabricated via solution casting using varying SCG loadings (0–2 g) and citric acid as a crosslinker. FTIR analysis confirmed the presence of characteristic PVA and lignocellulosic SCG functional groups, along with shifts in C=O and O–H regions indicating altered hydrogen-bonding environments. Tensile testing showed that increasing SCG content reduced tensile strength from 2.31 MPa (0 g SCG) to 0.63 MPa (2.0 g SCG), while Young’s modulus increased due to the rigid structure of SCG. Water absorption decreased markedly with filler incorporation, dropping from 21.61% (0 g SCG) to 5.57% (2.0 g SCG), demonstrating improved water resistance. Overall, SCG serves as an effective bio-filler that enhances moisture barrier properties and stiffness of PVA films, suggesting their potential for sustainable packaging applications.