Biodegradable Mulches Based on Poly(vinyl Alcohol), Kenaf Fiber, and Urea

Abstract

This paper describes the preparation of poly(vinyl alcohol)/kenaf fiber (PVOH/KF) composites with entrapped urea. The major FTIR peaks of these composites could be identified. These composites are intended for agricultural applications as biodegradable mulches and could be potential carrier materials for fertilizer. The water solubility, release behavior, chemical properties, and thermal stability of the composites were evaluated. The composites lost 25% of their weight after 7 days in water. In a wet environment, urea was released from the composites through its dissolution in water, and around 57% of the urea was released from the composites in 24 h; Thermagravimetric analysis showed that these composites were stable up 150 C. These composites would be able to withstand rain and protect seedlings from the sun when applied in the field as mulches. For around three to four weeks, these biobased mulches could slowly disintegrate as the PVOH binder was gradually dissolved by moisture, releasing the kenaf fibers to serve as soil fertilizer without leaving any undegradable waste for disposal. Hence, they would not pose any risks to the land or biological systems. Keywords INTRODUCTIONThere have been increasing concerns in recent years regarding environmental pollution consisting of non-biodegradable polyethylene mulch films. Previous literature has reported the uses of polyethylene films as mulches in reducing soil erosion and maintaining soil moisture for better crop growth (Adegbidi et al. 2003). Petroleum-based films are widely used due to their properties such as low density, good mechanical properties, excellent water resistance, and low cost (Nurfatimah et al. 2015). However, this synthetic plastic has generated a number of disposal difficulties because it requires huge labor forces for manual disposal. Land application is not a suitable disposal method for non-degradable plastic mulch due to its interference in the root development of subsequent crops (Kasirajan and Ngouajio 2012). An alternative disposal method for agricultural plastic wastes is through biodegradation processes.Many studies have demonstrated the use of biodegradable materials as alternatives to conventional polyethylene mulch films (Moreno and Moreno 2008). Some of the biodegradable materials used were composites developed from a combination of cellulose and starch (Moreno and Moreno 2008). These biodegradable films have not gained widespread use, possibly due to their high production cost and the unpredictable nature of their biodegradation behavior (Kasirajan and Ngouajio 2012). PEER-REVIEWED ARTICLEbioresources.com Tan et al. (2015). "PVOH/kenaf/urea mulches," BioResources 10(3), 5532-5543. 5533Poly(vinyl alcohol) (PVOH) is a non-toxic material that presents no adverse effects to biological systems, and has become highly attractive for various applications (DeMerlis and Schoneker 2003;. In the agriculture sector, PVOH could be a promising material for biodegradable mulches due to its water solubility (Guohua et al. 2006). This material ...

Effects of Substrate Material on Plant Growth and Nutrient Loss

“…The water-retaining agent used in the present study is a type of high-molecular polymer that can absorb water and other molecules and ions. Many adsorbed urea molecules are released slowly from the water-retaining agent [41], and the coating of water-retaining agent will have a slow release effect on nutrients [42]. Therefore, this agent provides a new material for the design of substrate material, in which nitrogen, phosphorus, and potassium fertilizers are coated with the water-retaining agent in the substrate, creating eutrophic conditions [43].…”

A Review of Natural Fiber Reinforced Poly(Vinyl Alcohol) Based Composites: Application and Opportunity

“…The obtained cellulosic structure is in micro and nanoscale. This micro-cellulose is made up of very short fibers while PVA has relatively lower stiffness and strength [23][24][25]. Thus, combining both of them may be a potential way to overcome the limitations.…”

“…The formation of cross-linking through the acetal linkages increased the glass transition temperature while reducing the melting temperature and crystallinity of PVA in the composites, due to the restricted segmental motion [24]. Another environmentally friendly cross-linker is Borax (Na 2 B 4 O 7¨1 0H 2 O) which is recognized as a non-toxic food additive, which has been successfully used in PVA/nanocellulose composites [48,49].…”

“…Moreover, the highly-crystalline nanocellulose not only tangled with PVA chains though numerous hydrogen bonds, but also formed chemically cross-linked complexes with borate ions as well, enhancing the stiffness and strength of hydrogel [48,49]. These crosslinking reactions associated with the effect of microfibrils have successfully strengthened the mechanical and thermal properties of the composites as well as to make the PVA partially water-insoluble [24].…”

Preparation and Characterization of Poly(lactic Acid)-based Composite Reinforced with Oil Palm Empty Fruit Bunch Fiber and Nanosilica

“…Poly(lactic acid) (PLA) reinforced with kenaf (Huda et al 2008), bamboo (Kang and Kim 2011), banana (Shih and Huang 2011), ramie (Yu et al 2010), oil palm (Rayung et al 2014), and other natural fibers have been studied. However, the use of these natural fibers have several drawbacks, such as incompatibility with hydrophobic polymer matrices, poor resistance to moisture, low degradation temperatures, and a higher tendency towards agglomeration during processing (Rayung et al 2014;Tan et al 2015). Therefore, fillers such as silica, aluminium, and zinc oxide have been further introduced into polymer composites to enhance their performance.…”