Zainoha Zakaria

Properties of polylactic acid composites reinforced with oil palm biomass microcrystalline cellulose

In this work, polylactic acid (PLA) composites filled with microcrystalline cellulose (MCC) from oil palm biomass were successfully prepared through solution casting. Fourier transform infrared (FT-IR) spectroscopy indicates that there are no significant changes in the peak positions, suggesting that incorporation of MCC in PLA did not result in any significant change in chemical structure of PLA. Thermogravimetric analysis was conducted on the samples. The T50 decomposition temperature improved with addition of MCC, showing increase in thermal stability of the composites. The synthesized composites were characterized in terms of tensile properties. The Youngs modulus increased by about 30%, while the tensile strength and elongation at break for composites decreased with addition of MCC. Scanning electron microscopy (SEM) of the composites fractured surface shows that the MCC remained as aggregates of crystalline cellulose. Atomic force microscopy (AFM) topographic image of the composite surfaces show clustering of MCC with uneven distribution.

Isolation and characterization of cellulose nanowhiskers from oil palm biomass microcrystalline cellulose.

The objective of this study is to compare the effect of two different isolation techniques on the physico-chemical and thermal properties of cellulose nanowhiskers (CNW) from oil palm biomass obtained microcrystalline cellulose (MCC). Fourier transform infrared analysis showed that there are no significant changes in the peak positions, suggesting that the treatments did not affect the chemical structure of the cellulose fragment. Scanning electron microscopy showed that the aggregated structure of MCC is broken down after treatment. Transmission electron microscopy revealed that the produced CNW displayed a nanoscale structure. X-ray diffraction analysis indicated that chemical swelling improves the crystallinity of MCC while maintaining the cellulose I structure. Acid hydrolysis however reduced the crystallinity of MCC and displayed the coexistence of cellulose I and II allomorphs. The produced CNW is shown to have a good thermal stability and hence is suitable for a range of applications such as green biodegradable nanocomposites reinforced with CNW.

Mechanical Properties and Morphological Characterization of PLA/Chitosan/Epoxidized Natural Rubber Composites

Poly (lactic acid) (PLA)/chitosan (CS) natural polymer/epoxidised natural rubber (ENR) composites were successfully prepared through a solution casting method. The morphological characteristics of fabricated composites were investigated by scanning electron microscopy (SEM) and optical microscopy. The microstructure of PLA/ENR was significantly altered with the addition of CS. SEM analysis of composites fractured surfaces revealed smooth and homogeneous texture and good dispersion of CS. However for 15 wt% CS composites, the phase segregation and poor adhesion between the polymers were observed. Fourier transform infrared spectroscopy revealed some levels of attractive interaction between CS, PLA, and ENR in the composites. The mechanical properties of composites in terms of tensile strength and tensile modulus were significantly improved with the addition of CS into the matrix while the percent elongation at break decreased. The tensile strength increased up to 5 wt% CS loading for both PLA/CS and PLA/ENR/CS and thereafter decreased while Young’s modulus increased up to 10 wt%. However, when the CS content was increased to 15 wt%, the tensile strength and tensile modulus were slightly decreased. These improvements were attributed to good dispersion of CS at the optimum filler levels and attractive interaction between the composites components.

Rice Husk Filled Polymer Composites

Natural fibers from agricultural wastes are finding their importance in the polymer industry due to the many advantages such as their light weight, low cost and being environmentally friendly. Rice husk (RH) is a natural sheath that forms around rice grains during their growth. As a type of natural fiber obtained from agroindustrial waste, RH can be used as filler in composites materials in various polymer matrices. This review paper is aimed at highlighting previous works of RH filled polymer composites to provide information for applications and further research in this area. Based on the information gathered, application of RH filled composites as alternative materials in building and construction is highly plausible with both light weight and low cost being their main driving forces. However, further investigations on physical and chemical treatment to further improve the interfacial adhesion with polymeric matrix are needed as fiber-polymer interaction is crucial in determining the final composite properties. Better understanding on how the used polymer blends as the matrix and secondary fillers may affect the properties would provide interesting areas to be explored.

Effect of hydrolysed cellulose nanowhiskers on properties of montmorillonite/polylactic acid nanocomposites.

Polylactic acid (PLA) nanocomposites reinforced with hybrid montmorillonite/cellulose nanowhiskers [MMT/CNW(SO4)] were prepared by solution casting. The CNW(SO4) nanofiller was first isolated from microcrystalline cellulose using acid hydrolysis treatment. PLA/MMT/CNW(SO4) hybrid nanocomposites were prepared by the addition of various amounts of CNW(SO4) [1-9 parts per hundred parts of polymer (phr)] into PLA/MMT nanocomposite at 5 phr MMT content, based on highest tensile strength values as reported previously. The biodegradability, thermal, tensile, morphological, water absorption and transparency properties of PLA/MMT/CNW(SO4) hybrid nanocomposites were investigated. The Biodegradability, thermal stability and crystallinity of hybrid nanocomposites increased compared to PLA/MMT nanocomposite and neat PLA. The highest tensile strength of hybrid nanocomposites was obtained by incorporating 1 phr CNW(SO4) [∼ 36 MPa]. Interestingly, the ductility of hybrid nanocomposites increased significantly by 87% at this formulation. The Youngs modulus increased linearly with increasing CNW(SO4) content. This is due to the relatively good dispersion of nanofillers in the hybrid nanocomposites, as revealed by transmission electron microscopy. Fourier transform infrared spectroscopy indicated the formation of some polar interactions. In addition, water resistance of the hybrid nanocomposites improved and the visual transparency of neat PLA film did not affect by addition of CNW(SO4).

Partial replacement effect of montmorillonite with cellulose nanowhiskers on polylactic acid nanocomposites.

In this study, hybrid montmorillonite/cellulose nanowhiskers (MMT/CNW) reinforced polylactic acid (PLA) nanocomposites were produced through solution casting. The CNW filler was first isolated from microcrystalline cellulose by chemical swelling technique. The partial replacement of MMT with CNW in order to produce PLA/MMT/CNW hybrid nanocomposites was performed at 5 parts per hundred parts of polymer (phr) fillers content, based on highest tensile strength values as reported in our previous study. MMT were partially replaced with various amounts of CNW (1, 2, 3, 4 and 5phr). The tensile, thermal, morphological and biodegradability properties of PLA hybrid nanocomposites were investigated. The highest tensile strength of hybrid nanocomposites was obtained with the combination of 4phr MMT and 1phr CNW. Interestingly, the ductility of hybrid nanocomposites increased significantly by 79% at this formulation. The Youngs modulus increased linearly with increasing CNW content. Thermogravimetric analysis illustrated that the partial replacement of MMT with CNW filler enhanced the thermal stability of the PLA. This is due to the relatively good dispersion of fillers in the hybrid nanocomposites samples as revealed by transmission electron microscopy. Interestingly, partial replacements of MMT with CNW improved the biodegradability of hybrid nanocomposites compared to PLA/MMT and neat PLA.

Enzymatic esterification of eugenol and benzoic acid by a novel chitosan-chitin nanowhiskers supported Rhizomucor miehei lipase: Process optimization and kinetic assessments

A biotechnological route via enzymatic esterification was proposed as an alternative way to synthesize the problematic anti-oxidant eugenyl benzoate. The new method overcomes the well-known drawbacks of the chemical route in favor of a more sustainable reaction process. The present work reports a Box-Behnken design (BBD) optimization process to synthesize eugenyl benzoate by esterification of eugenol and benzoic acid catalyzed by the chitosan-chitin nanowhiskers supported Rhizomucor miehei lipase (RML-CS/CNWs). Effects of four reaction parameters: reaction time, temperature, substrate molar ratio of eugenol: benzoic acid and enzyme loading were assessed. Under optimum conditions, a maximum conversion yield as high as 66% at 50°C in 5h using 3mg/mL of RML-CS/CNWs, and a substrate molar ratio (eugenol: benzoic acid) of 3:1. Kinetic assessments revealed the RML-CS/CNWs catalyzed the reaction via a ping-pong bi-bi mechanism with eugenol inhibition, characterized by a Vmax of 3.83mMmin-1. The Michaelis-Menten constants for benzoic acid (Km,A) and eugenol (Km,B) were 34.04 and 138.28mM, respectively. The inhibition constant for eugenol (Ki,B) was 438.6mM while the turnover number (kcat) for the RML-CS/CNWs-catalyzed esterification reaction was 40.39min-1. RML-CS/CNWs were reusable up to 8 esterification cycles and showed higher thermal stability than free RML.

Effects of Micro- and Nano-cellulose on Tensile and Morphological Properties of Montmorillonite Nanoclay Reinforced Polylactic Acid Nanocomposites

In this chapter, the effects of micro- and nano-cellulose; microcrystalline cellulose (MCC) and cellulose nanowhiskers (CNW), on the properties of montmorillonite (MMT)/polylactic acid (PLA) nanocomposites fabricated using solution casting method were investigated. CNW were isolated from MCC using a chemical swelling method. An initial study showed that the optimum MMT content, based on tensile properties, in PLA/MMT nanocomposite is 5 phr (parts per hundred parts of resin). PLA/MMT/MCC hybrid composites and PLA/MMT/CNW hybrid nanocomposites were produced by incorporating of various contents of MCC and CNW into the optimum formulation of PLA/MMT nanocomposites (P/MT5), respectively. The Young’s modulus of PLA/MMT/MCC hybrid composites and PLA/MMT/CNW hybrid nanocomposites increased gradually with increasing MCC and CNW content, respectively. The tensile strength of hybrid composites decreased compared to P/MT5 nanocomposite. However, the tensile strength for the hybrid nanocomposites increased with incorporation of CNW and reached the highest value at 1 phr CNW content. The ductility of hybrid composites and hybrid nanocomposites was also increased significantly from ~10 to ~60 and ~90 % with the incorporation of 1 phr MCC and CNW fillers, respectively. This increase in ductility was proposed to be due to the nucleation of crazes and the formation of shear bands in the PLA. Transmission electron microscopy and X-ray diffraction analyses showed that MCC slightly decreased the MMT interlayer spacing in hybrid composites, while the MMT interlayer spacing in hybrid nanocomposites increased by incorporation of CNW into P/MT5 nanocomposite.

Effects of cellulose nanowhiskers preparation methods on the properties of hybrid montmorillonite/cellulose nanowhiskers reinforced polylactic acid nanocomposites

In this chapter, the effects of two different preparation methods of cellulose nanowhiskers (CNW) on the tensile, thermal, morphological, and biodegradability properties of montmorillonite (MMT)-reinforced polylactic acid (PLA) were investigated. The CNWs were obtained from microcrystalline cellulose using chemical swelling (CNW-CS) and sulfuric acid hydrolysis (CNW-AH). Based on tensile properties, the optimum MMT content in PLA/MMT nanocomposites is five parts per hundred parts of polymer (phr) [P/MT5]. The PLA/MMT/CNW-CS and PLA/MMT/CNW-AH hybrid nanocomposites were produced using solution casting by the addition of various amounts of CNW-CS and CNW-AH fillers into P/MT5 nanocomposite, respectively. The highest tensile strength for the hybrid nanocomposites was obtained at 1 phr CNW-CS and CNW-AH content. Interestingly, the ductility of the hybrid nanocomposites increased significantly from ~10 to ~90 and ~87% with the addition of 1 phr CNW-CS and CNW-AH, respectively. The biodegradability and thermal stability of hybrid nanocomposites improved compared to P/MT5 nanocomposite and neat PLA.

Microcrystalline cellulose from oil palm empty fruit bunches as filler in polylactic acid

Acid hydrolysis method was used to isolate microcrystalline cellulose (MCC) from oil palm empty fruit bunches (OPEFB) total chlorine free bleached pulp. The derived MCC was incorporated into polylactic acid (PLA) using solution casting technique in order to produce PLA/MCC composites. The chemical structure of the cellulose fragments remains unaltered as demonstrated by Fourier transform infrared spectroscopy despite acid hydrolysis. X-ray diffraction showed that the MCC has a cellulose I polymorph with 87% crystallinity index. The addition of MCC into PLA enhanced not only the thermal stability but also the Youngs modulus of the PLA/MCC composites by approximately 30% at 5 phr MCC contents compared to pure PLA. However a decrease in tensile strength and elongation at break of the PLA/MCC composites were observed due to the poor dispersion of MCC in the PLA matrix