Thermal Analysis of Cellulose Fibres Extracted from Locally Available Rice Straw

Agriculture sector plays a vital role in Sri Lankan economy. Although the country is moving towards industrialisation, the agricultural sector still contributes substantially to both foreign exchange earnings and GDP. Paddy is cultivated in almost all parts of the country, except at very high altitudes. In 2018, around 3.9 million metric tonnes of paddy was harvested across the country from both Yala and Maha seasons. Rice straw is a by-product from the paddy cultivation and identified as agricultural production residue that is generated in equal or greater quantities than the rice itself with no commercial interest. Therefore, it is of ecological and economical point of view to discover an advantageous utilization of this material. Agricultural crop residues are rich in lignocellulosic materials with cellulose as the principle constituent. Study on the thermal properties of rice straw fibers are important in order to estimate their industrial applications. In this study, cellulose fibers were extracted from rice straw (BG352) via a series of chemical treatments. The structure and chemical composition of cellulose fibers were investigated using Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD) and scanning electron microscopy (SEM). Thermal stability of each sample was determined using TGA SDT Q600 simultaneous thermal analyser (TA instruments, Delaware, USA). Analysis of individual samples was carried out at a constant heating rate of 10 °C/min between ambient temperature to 700o C in a nitrogen atmosphere. FTIR analysis of fibers demonstrate that the chemical purification treatment results in sequential and complete removal of hemicellulose (1729 cm-1, carbonyl stretching), lignin (1516 cm-1, aromatic skeletal vibrations) and silica (796 cm-1 and 466 cm-1, Si–O–Si stretching). XRD results also reveal the removal of lignin (shoulder peak at 16.4o) and hemicellulose (weak peak at 34.76o) from rice straw thus, confirms the final product as cellulose. Three endothermic peaks were observed in thermogravimetric analysis. Initially a small weight loss was observed around 100o C due to the low molecular weight components in the fibers and the evaporation of remained moisture. Hemicellulose pyrolysis was occurred around 260o C. A resistant increase in cellulose was observed due to the removal of almost all hemicelluloses from the rice straw. Pyrolysis of lignin in rice straw started at 200o C and persisted till 700o C. Further, a significant difference between the contents of the residues were remained which indicated that the thermal stability of cellulose was visibly improved. Based on the results obtained, the extracted cellulose fibers from locally available rice straw could be used to produce textiles, composites, all kinds of paper and paper boards, photographic films, moisture proof coatings for food packaging and other fibrous products similar to those produced from the synthetic fibers. Using rice straw as a source of high-quality fibrous applications will add value to the rice crops, mitigate concerns regarding burning or disposing of rice straw, and provide an environmentally friendly alternative to replace the synthetic fibers currently in use.Keywords: Sri Lankan rice straw, Cellulose fibers, Chemical treatment, Thermal decomposition, Thermal propertie

Fabrication of Nanofibrillated Cellulose (NFC) Based Composite Materials for Engineering Applications

Nanomaterials play an important role as modern engineering materials for various engineering, medical and biological applications today. Nanocellulose is a natural polymeric fiber that has a minimum of one dimension within the nanometer scale and exhibits a potential as a reinforcement agent for various materials. Nanocellulose can be extracted from plant materials such as agricultural, agro-industrial and forestry wastes. They are divided into two main classes as nanofibrillated cellulose (NFC) and nanocrystalline cellulose (NCC). Compared to NCC, NFC has gained a considerable attention because of the interesting properties including high mechanical properties, reinforcing ability and aspect ratio. Combination of NFC with synthetic polymer materials is an interesting area in the polymer-based researches to enhance mechanical and thermal properties of the composite. These natural plant based composites deplete the environmental pollution created by traditional synthetic polymers. Polypropylene is a widely used thermoplastic material in engineering composite applications as a matrix material. The objective of this research was to fabricate a polypropylene and NFC based composite material. In nature, NFC is hydrophilic and polypropylene is hydrophobic. Therefore, modification of NFC surface is necessary to prepare a nanocomposite with a better performance. In the present research analyzed the mechanical, thermal, water absorption and processability properties of polypropylene-NFC-based composite with up to 5 wt.% loading of unmodified silane (Si-69) and silane (Si-69) surface modified NFC reinforced composites. The characterization of raw materials and the composites were performed using SEM, FTIR, XRD, TGA and DTA techniques. In addition, the mechanical properties of composites were evaluated by using a universal testing machine and hardness tester. Further, the melt flow rate and water absorption properties of the developed products were evaluated using standard test methods. The best thermal resistance and mechanical properties were given by the 3.5 wt.% of silane surface modified NFC loaded polypropylene composite including tensile strength (28 MPa), hardness (78 Shore D) and impact strength (4 kJ m-2) and these values are 7%, 13%, and 86% higher than that of the pure polypropylene respectively. In addition, the composite sample has the intermediate level of water absorption (0.1 wt. %) and processability (21.1 g/10 min) with respect to all the other fabricated samples including pure polypropylene. The prepared nanocomposite material can be used for many engineering applications such as packaging, constructions, automotive and aerospace as a sustainable material.Keywords: Nanofibrillated cellulose, Polypropylene, Surface modification, Nanocomposit

Fabrication of Antimicrobial Material for Food Packaging Applications

Nowadays, polystyrene is the widely used material in disposable food packaging applications. One of the main disadvantages of polystyrene as a food packaging material is the microbial attack during the food storage. Objective of this research is to fabricate a nano silver based antimicrobial coating on polystyrene based packaging material to extent the self-life. In this research nano silver solution was prepared using polyvinyl alcohol and silver nitrate. Nano silver formation was confirmed by analyzing UV-Vis spectrum. Citric acid was used as the crosslinking agent of polyvinyl alcohol (PVA). UV assisted treatment was used to modify the internal surface of the polystyrene containers to improve the wettability. Fourier transforms infrared spectroscopy - Attenuated total reflection method was used to identify the surface modifications after the UV treatment. Fourier transform infrared spectroscopy test results showed the significant changes occurred on internal surface of Polystyrene samples due to UV treatment. The prepared Ag/PVA/Citric solution was coated on UV treated polystyrene container and kept under the heat to crosslink with the surface. Antimicrobial activity of prepared nano silver coated polystyrene based food packaging was tested against E.coli bacteria. There was a clear inhibition zone in nano silver coated Polystyrene sample under E. coli growth. It indicated that nano silver coated polystyrene containers showed significant antimicrobial activity. There will be various human health, safety, minimum waste generation and economic benefits from these developed nano silver coated polystyrene food packaging products. These products can be used to control the waste generation in near future.Keywords: Food packaging, Nano silver, Antimicrobial, Polystyren

Extraction and Characterisation of Cellulose Materials from Sri Lankan Agricultural Waste

Agriculture is a key sector of Sri Lankan economy today. Sri Lanka’s main food crop is rice. Rice is cultivated mainly in two seasons in the country. Rice production is the predominant form of agriculture which occupies 0.77 million hectares of the total cultivated area in Sri Lanka. Nevertheless, generation of enormous amounts of agricultural residues such as rice straw during rice production has become inevitable According to the statistics it is revealed that one ton of rice paddy produces 290 kg of rice straw. Regardless of these large amounts, rice straw is frequently abolished by open field burning by majority of farmers. However, recent researchers have reported that rice straw burning can be lethal towards human health due to the noxious emissions which cause various forms of environmental pollution. Hence, identifying the means of generating value added products by utilisation of rice straw has become a necessity today. Rice straw is a lingo cellulosic biomass which consists of biopolymers of cellulose, hemicellulose and lignin. Cellulose is the mostly abundant organic polymer on earth that can be identified as one of the most demanded advanced materials in engineering applications such as bio composites production. Therefore, developing a method to isolate cellulose from rice straw would be a convenient means of value addition to the agricultural waste. This research work is based on developing an environmentally friendly, efficient method to synthesise cellulose from rice straws of the most frequently cultivated hybrid rice variety (BG352) in Sri Lanka. BG 352 rice variety is cultivated in most of the areas in Sri Lanka today. High purity cellulose was extracted from rice straw by the removal of non-cellulosic materials. This chemical purification process consisted of dewaxing, delignification and hemicellulose and silica removal treatments. FTIR spectroscopy was used to verify the formation of pure cellulose during the extraction process. Further, morphology of extracted cellulose was studied by SEM analysis. It revealed that isolated cellulose was mostly in the form of fibers with diameters ranging from 2-8μm. This research showed that BG352 variety averagely has 16.1 wt.% wax, 38.2 wt.% lignin, 3.9% wt. hemicellulose and 12.3 wt.% silica content. Ultimately, average cellulose yield from rice straws of BG352 variety was observed as 30 wt.%. This extraction process can be used to synthesis the cellulose from Sri Lankan agricultural waste to convert it into a value added product.Keywords: Rice straw, Agricultural waste, Cellulose, Lignocellulosic, Biopolyme

Fabrication of Surface Modified Microcrystalline Cellulose-Polypropylene Composites for Engineering Applications

There’s a heighten interest in nanometric and micrometric dimensions of cellulose fibers for its greater potential in reinforcement of composites. Microcrystalline cellulose (MCC) gained its peculiar features with its high aspect ratio, large surface area and high mechanical properties making MCC a better candidate as the potential starting material for cellulose fiber reinforced nano-composites. The surge of sustainable development and environmentally benign plastics have attract much attention in biodegradable natural fiber reinforced polymer composites. The objective of this research was to fabricate MCC reinforced polypropylene (PP) composites improving the mechanical, thermal and physical properties. Extreme hydrophilicity of MCC and hydrophobicity of PP leads to weak compatibility with poor performance in the composite. Thus, surface modification is essential to abate the hydrophilicity of MCC and thereby to improve the compatibility and overall performance of the composite. Sunflower oil was converted into its corresponding sunflower oil ethyl esters (SFEEs) and grafted onto the MCC surface in order to improve MCC surface hydrophobicity. Unmodified and SFEE modified MCC were separately added into PP matrix up to 5% loading. Two series were characterised using FTIR, XRD, TGA-DSC, universal testing machines and shore D hardness tester according to its mechanical, thermal and physical properties. Higher thermal stability and mechanical properties were achieved with 5% SFEE surface modified MCC reinforced PP composite. Tensile, impact and hardness properties of neat PP were 27 MPa, 7 kJm-2 and 60 shore D which were improved up to 30 MPa, 12 kJm-2 and 75 shore D respectively, with the addition of 5% SFEE modified MCC-PP composites. This study mainly focused on a low cost, ecologically green and industrially friendly pathway to improve MCC-PP compatibility which can be used as a sustainable material in many engineering applications.Keywords: Microcrystalline cellulose, Polypropylene, Surface modification, Sunflower oil ethyl ester