Microwave Hydrothermal Carbonization of Rice Straw: Optimization of Process Parameters and Upgrading of Chemical, Fuel, Structural and Thermal Properties.

The process parameters of microwave-induced hydrothermal carbonization (MIHTC) play an important role on the hydrothermal chars (hydrochar) yield. The effect of reaction temperature, reaction time, particle size and biomass to water ratio was optimized for hydrochar yield by modeling using the central composite design (CCD). Further, the rice straw and hydrochar at optimum conditions have been characterized for energy, chemical, structural and thermal properties. The optimum condition for hydrochar synthesis was found to be at a 180 °C reaction temperature, a 20 min reaction time, a 1:15 weight per volume (w/v) biomass to water ratio and a 3 mm particle size, yielding 57.9% of hydrochar. The higher heating value (HHV), carbon content and fixed carbon values increased from 12.3 MJ/kg, 37.19% and 14.37% for rice straw to 17.6 MJ/kg, 48.8% and 35.4% for hydrochar. The porosity, crystallinity and thermal stability of the hydrochar were improved remarkably compared to rice straw after MIHTC. Two characteristic peaks from XRD were observed at 2? of 15° and 26°, whereas DTG peaks were observed at 50?150 °C and 300?350 °C for both the materials. Based on the results, it can be suggested that the hydrochar could be potentially used for adsorption, carbon sequestration, energy and agriculture applications

Enhanced Mechanical and Barrier Performance of Poly (Lactic Acid) Based Nanocomposites Using Surface Acetylated Starch Nanocrystals

Poly (lactic) acid (PLA) based nanocomposites reinforced with starch nanocrystals (SNC) extracted from high amylopectin waxy maize starch and acetylated starch nanocrystals (Ac-SNC), were prepared and their influence on the overall properties of PLA nanocomposites were studied. The two nanofillers (SNC and Ac-SNC) were incorporated in PLA at two different loadings (1 and 3 wt%) by solvent casting and evaporation technique. Surface acetylation of SNC was confirmed by Fourier Transform infra-red spectroscopy and nuclear magnetic resonance spectroscopy and the crystalline structure by X-ray diffraction. This paper reports the influence of incorporating unacetylated and surface acetylated starch nanocrystals on morphological, barrier, mechanical, and rheological properties of PLA based nanocomposites. While both nanofillers improved the properties of PLA, the PLA-Ac-SNC had superior properties to that of PLA-SNC nanocomposites, due to better filler dispersion and interaction with the polymer matrix. These sustainable nanocomposites with improved properties will expand the application of these bio-sourced starch nanocrystals

Thermal Properties of Sustainable Thermoplastics Nanocomposites Containing Nanofillers and Its Recycling Perspective

Sustainable thermoplastic nanocomposites are of great importance because they possess the potential to resolve concerns on the emission of greenhouse gases, depletion of fossil fuels and pollution. The thermal characteristics of polymers and nanocomposites play a significant role in determining the suitable application of these materials. This review provides an overview of the thermal properties of sustainable thermoplastic nanocomposites incorporated with various nanofillers. Thermogravimetric/differential thermogravimetric analysis, DSC and thermal conductivity of various thermoplastic nanocomposites have been elaborated in detail. Further, the recycling perspectives of various polymers have been discussed. The thermal properties are essential characteristics to understand the behaviour of the raw material and final product. The performance and properties of the nanocomposite are greatly dependent on the polymer matrix, polymer dispersion in composite, properties and aspect ratio of fiber, the interface of fiber and matrix, and process parameters

Morphological, structural, thermal and degradation properties of polylactic acid and waxy maize starch nanocrystals based nanocomposites prepared by melt processing

Currently used petroleum-based polymers have adversely affected the environment in various ways, mainly due to their non-biodegradability. This undesirable aspect of commercial polymers led to increased interest in the research area of biodegradable polymer nanocomposites. Polylactic acid (PLA) based nanocomposites, with three different loadings of waxy maize starch nanocrystals (WSNC) as nanofiller (1, 3 and 5 wt%), were melt-blended in a Haake Rheomix. The morphological, structural, thermal and abiotic degradation characteristics of the prepared PLA WSNC nanocomposites were studied to determine the effects of adding WSNC at different loadings in PLA. The results indicated that WSNC were dispersed uniformly at lower loadings (0-3 wt%) and agglomerated at higher loadings (5 wt%) within the PLA matrix. All PLA-WSNC nanocomposites were found to be stable over the processing temperature range of 25-220 ºC. In addition, there was no considerable change in the glass transition temperature and the melting point of the nanocomposites. Though, the cold crystallization temperature was reduced with the increase of WSNC loadings. The abiotic degradation studies, used as an initial screening tool, indicated that WSNC can accelerate the degradation process of PLA. As a result, the degradation rate was improved for all the PLA-WSNC nanocomposites. The PLA-WSNC-3 wt% was found to be the optimum concentration to enhance the crystallinity and morphological property of PLA, and beyond that the properties were affected by agglomeration

Preparation of Square-Shaped Starch Nanocrystals/Polylactic Acid Based Bio-nanocomposites: Morphological, Structural, Thermal and Rheological Properties

The development of low-cost bio-nanocomposites based on square-shaped starch nanocrystals (SNCs) is a promising approach for maintaining environmental sustainability. This study reports on a method for the preparation of bio-nanocomposites from polylactic acid (PLA) and SNC derived from acid hydrolysis of waxy maize starch. PLA-SNC bio-nanocomposites were prepared by incorporating SNC at 1, 3 and 5 wt% by dispersing them in PLA matrix using dichloromethane as a solvent. Morphological, thermal, crystalline and rheological properties of neat PLA, neat SNC and PLA-SNC bio-nanocomposites have been investigated to observe the effect of SNC loading. SNC loading at 3 wt% was found to be the optimum loading to improve the storage modulus, complex dynamic viscosity, and crystallinity, while 5 wt% loading caused agglomerations which led to a decrease in the above properties. Thermogravimetric analysis result suggested that both the SNC and PLA-SNC bio-nanocomposites were thermally stable from 25 to 240 °C. Electron microscopy study showed the effective dispersion of SNC in PLA

Structural, thermal, rheological and optical properties of poly(lactic acid) films prepared through solvent casting and melt processing techniques

In this study, structural, thermal, rheological and optical properties of poly(lactic acid) (PLA) films prepared by solvent casting and melt processing were observed and compared, in order to gain a better understanding of processing methods on the properties of the polymer. The structural study revealed that the solvent cast PLA film had a comparatively rough surface when fractured, with longer fibrils and produced strong X-ray diffraction peaks, which suggested different crystalline structures within the film. The melt processed film, on the other hand, appeared to be smooth when fractured and had a broad amorphous X-ray diffraction pattern. Thermal analysis indicated that the solvent cast films tended to form crystalline structure because the cold crystallization temperature was higher for the films prepared by solvent cast method. Both films demonstrated a Newtonian plateau at lower frequency with a zero-shear rate viscosity above 1000 Pa s, and showed a shear thinning behaviour at a higher frequency, with the shear thinning of the solvent cast PLA film being stronger than that of melt processed film. In addition, the structural and molecular changes due to the difference in processing conditions were investigated using polarized light microscopy and synchrotron-FTIR microspectroscopy