Biodegradable dual-layer Polyhydroxyalkanoate (pha)/Polycaprolactone (pcl) mulch film for agriculture: Preparation and characterization

Abstract

• Biodegradable dual-layer mulch film based on polyhydroxyalkanoate (PHA) and polycaprolactone (PCL) • Produce mulch film with higher biodegradability without generating microplastics • Use of radiation crosslinking technique to improve the adherence between PHA and PCL • Soil burial test with high degradability percentage for dual-layer mulch film. This study focused on preparing biodegradable dual-layered mulch film based on polyhydroxyalkanoate (PHA) and polycaprolactone (PCL). The main aim of this study is to prepare mulch film with higher biodegradability for rice seed germination. Common plastic mulch films are mostly non-readily biodegradable and stay as residual in soil for a very long duration leading to an increase in salt content and reduction in water and nutrient movement in the soil. This makes the farmland unusable for agricultural purposes. The PHA and PCL were the ideal options as both have their merits and demerits which compensates each other while being cast into double layers and are highly biodegradable. The novelty of this study emphasizes the attachment of PHA and PCL as a dual layer at different ratios that offers a higher bio-degradability percentage. The dual-layer mulch film is made of PHA as the first layer and a mixture of PHA and PCL at different ratios as the second layer. The ratio of PHA/PCL used was 90:10, 70:30, and 50:50. The dual-layered mulch film was prepared using the hot-press technique and later cross-linked by using electron beam irradiation in order to ensure the strong adherence between the two layers. The gel content analysis was performed to measure the crosslinking percentage. The radiation dose of 30 kGy was chosen as the minimum amount of crosslinking and approximately 3.00% was attained for the course. The mixture of PHA/PCL films with different ratios, PHA and PCL virgin film were subjected to a soil burial bio-degradability test. The PHA and PCL virgin film had shown the highest degradation percentage, almost 48.34% just in five weeks. Further characterization was performed on virgin dual-layered PHA/PCL (100%) based on their higher degradability tendency. The apparent properties, morphology, thermal stability, chemical composition, and mechanical properties of dual-layer PHA/PCL (100%) were tested thoroughly. The thickness and transparency attained for dual-layer PHA/PCL (100%) were around 175.25μm and 110.45%. The thermal properties of both single layer PHA and PCL showed good stability, Meanwhile, the virgin dual-layered PHA/PCL mulch film had shown a poor thermal stability. The peak positioning in FTIR for single layer PHA and PCL at 3042.37cm −1 , 2942.37cm −1 , 1719.54cm −1 ,1453.33cm −1 ,1378.95cm −1 and 1181.48cm −1 remained unchanged in virgin double-layered PHA/PCL film as well. The outcome of the analyses clearly indicates the possibilities of the dual-layer PHA/PCL (100%) with greater bio-degradability. The soil burial biodegradability test needs to be prolonged up to its full potential. The other characteristics such as water permeability, photo permeability, crystallinity, and heat preservation need to be investigated as well.