Starch Based Rubber Nanocomposites (original) (raw)
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Macromolecular Materials and Engineering, 2012
The structural and mechanical properties of natural rubber (NR) nanocomposites filled with starch nanocrystals (SNC) extracted from four different starch sources are investigated. The aim of this work is to explore the influence of botanic sources on final properties of nanocomposites and SNC reinforcing capability. A general trend seems to be that the higher the amylose content of native starch granules used for preparing SNC, the lower the water uptake and reinforcing effect (except for potato starch). It is postulated that SNC prepared from higher amylose content starch might release loosely bonded amylose chains during preparation and/or soaking in water and thus prevent SNC to participate in the formation of a reinforcing network.
African Journal of Pure and Applied Chemistry
Starch fillers were extracted from three plant sources namely amora tuber, Tacca lentopeteloides; sweet potato, Ipomoea batatas; yam starch, Dioscorea rotundata and their particle size, pH, amylose, and amylopectin percentage decomposition determined accordingly. The starch was introduced into natural rubber in liquid phase (through gelatinization) by the latex compounding method and compounded according to standard method. The prepared starch/natural rubber composites was characterized by Instron Universal testing machine (UTM) for tensile mechanical properties. The composites was further characterized by x-ray diffraction and crosslink density analysis. The particle size determination showed that amora starch granules has the smallest particle size (156 × 47 μm) followed by yam starch (155 × 40 μm) and then sweet potato starch (153 × 46 μm) with the biggest particle size. The pH test also revealed that amora starch has a near neutral pH of 6.9, yam 6.8, and sweet potato 5.2 respectively. Amylose and amylopectin determination showed that yam starch has a higher percentage of amylose (29.68), followed by potato (22.34) and then amora starch with the lowest value (14.86) respectively. The tensile mechanical properties testing revealed that yam starch produced the best tensile mechanical properties followed by amora starch and then sweet potato starch. The structure, crystallinity/amorphous nature of the product composite was confirmed by x-ray diffraction, while the nature of crosslinking was confirmed by swelling test in toluene solvent using the Flory-Rehner approach. The increasing values of crosslink density in the starch/rubber composite is a clear evidence of good interfacial adhesion between the starch fillers and the rubber, hence good dispersion of starch fillers in the rubber. This research has rendered a workable strategy for enhancing interfacial interaction between a hydrophilic filler (Starch) and hydrophobic polymeric matrix (natural rubber) yielding moderately good tensile mechanical properties with prospects for the rubber processing industry. The studied fillers can partially replace carbon black as natural rubber fillers with reduced cost, no risk to human health and also an environment friendly approach.
International Journal of Biological Macromolecules, 2014
The various sizes (15, 30, 80, and 100 nm) of nano-SiO 2 /potato starch films were synthesized and characterized. The gas permeability, antibacterial properties, and mechanical properties of the films were evaluated to their potential for application as food packaging materials. Results indicated that the 100 nm nano-SiO 2 was well dispersed in the starch matrix, which induced an active group on the surface of 100 nm nano-SiO 2 adequately combined with starch macromolecule. The water resistance and mechanical properties of the films were improved with the addition of nano-SiO 2. Notably, resistance to ultraviolet and thermal aging was also enhanced. The nano-SiO 2 /potato starch films were more efficient against Escherichia coli (E. coli) than Staphylococcus aureus (S. aureus). Remarkable preservation properties of the films packaging the white mushrooms were obtained, with those of the 100 nm films considered superior. This study can significantly guide the rational choice of the nano-SiO 2 size to meet the packaging requirements of various agricultural products.
Reinforcing Mechanisms of Starch Nanocrystals in a Nonvulcanized Natural Rubber Matrix
Biomacromolecules, 2011
Unfilled elastomers are known to exhibit linear viscoelastic behavior at shear strains up to 10À20%. 1 To enhance the mechanical properties of elastomers, most of them are reinforced with fillers, notably carbon black, silica, or clays such as montmorillonite. 2,3 It has been shown that unlike unfilled elastomers, reinforced materials exhibit a nonlinear viscoelastic behavior at shear strains as low as a few percent, generally described in terms of Mullins or Payne effects. The Mullins effect or "stress softening effect" is characterized by a pronounced lowering of the storage modulus (or stress) when elastomers are sheared a second time. 4 The Payne effect characterizes the decrease in the real part of the elastic modulus with increasing strain amplitude. This nonlinear behavior has been first evidenced for natural rubber filled with carbon black 2 and has been confirmed by many authors for reinforced synthetic elastomers. 1,5À9 This behavior is of great practical importance and essential for tire applications. It has been related to usage properties, and, in particular, to the rolling resistance or the wet skid resistance of tires. Various mechanisms have been proposed in the literature to explain the origins of the reinforcement of elastomers. They include molecular surface slippage or rearrangements, particle displacements, interparticle chain breakage, strong and weak surface binding, and other network particle surface phenomena. 8 During the last decade, the increase in fossil energy costs and environmental issues has resulted in the development of biodegradable materials from renewable resources. In parallel, polymer nancomposites have attracted considerable interest in both academia and industry, owing to their outstanding mechanical properties like elastic stiffness and strength while using only a small amount of nanoparticles. The enhanced properties include not only mechanical performances but also barrier resistance, flame retardancy, as well as optical and electrical properties. In this context, waxy maize starch nanocrystals have been used as filler in a nonvulcanized natural rubber (NR). 11,12 The NR matrix was not cross-linked to keep the biodegradability and recyclability of such biosourced materials. Waxy maize starch nanocrystals appeared to display interesting barrier properties and to be an effective reinforcing filler for NR at temperatures higher than T g of the matrix. Dynamic mechanical analysis performed in the linear viscoelastic region has shown that the relaxed modulus at room temperature of nanocomposites containing 10, 20, and 30 wt % (around 6.7, 13.4, and 20.1 vol %) of filler was about 10, 75, and 200 times higher, respectively, than the one of the unfilled ABSTRACT: A phenomenological modeling approach was developed to try to understand the reinforcing mechanism of starch nanocrystals in a nonvulcanized natural rubber matrix. Natural rubber was not cross-linked to maintain the biodegradability of the biosourced materials. Nonlinear dynamic mechanical experiments highlighted the significant reinforcing effect of starch nanocrystals and the presence of the Mullins and Payne effects. Two models were used to predict the Payne effect considering that either fillerÀfiller (Kraus model) or ma-trixÀfiller (Maier and G€ oritz model) interactions are preponderant. The use of the Maier and Goritz model demonstrated that phenomena of adsorption and desorption of NR chains on the filler surface governed nonlinear viscoelastic properties, even if the formation of a percolating network for filler contents >6.7 vol % was evidenced by the Kraus model.
Processing and Structural Properties of Waxy Maize Starch Nanocrystals Reinforced Natural Rubber
Macromolecules, 2005
Nanocomposite materials were obtained using a latex of natural rubber as the matrix and an aqueous suspension of waxy maize starch nanocrystals as the reinforcing phase. Starch nanocrystals were obtained after sulfuric acid hydrolysis of waxy maize starch granules. They consisted of crystalline platelets 6-8 nm thick, 40-60 nm long, and 15-30 nm wide. After mixing the latex and the starch nanocrystals, the resulting aqueous suspension was cast and evaporated. The solid nanocomposite films were characterized using scanning electron microscopy, water and toluene absorption experiments, differential scanning calorimetry, and wide-angle X-ray diffraction analysis. The barrier properties of the nanocomposites to water vapor and oxygen were also investigated, and the effect of surface chemical modification of starch nanocrystals was studied.
Springer eBooks, 2015
This article presents a novel method for integrating native corn starch and calcium carbonate (CaCO 3) into a hybrid pigment, which can be applied in papermaking to increase the amount of starch in paper and improve sheet bonding without impairing dewatering. Starch was first thermally treated to partially gelatinize and swell the granules. The aim of the treatment was to change the surface properties of starch and thus to improve the interaction with CaCO 3 particles. CaCO 3 shell was precipitated around the swollen granules and the encapsulated starch was then cooked to achieve complete gelatinization. When the granules were cooked, the starch became active for bonding, but its solubility was very limited due to the encapsulation. Particle size measurement and scanning electron microscopy were used to analyze the sample properties during the preparation. The hybrid pigment was added to paper sheets and its effect on the paper properties was examined. Starch was shown to be effectively bound to the pigment structure. The hybrid pigment allowed a large amount of native corn starch to be added to paper without interfering with the papermaking process. Furthermore, it gave excellent mechanical paper properties.
Modification and Application of Starch in Natural Rubber Latex Composites
Rubber Chemistry and Technology, 2018
This study presents a review of recent studies on starch-filled NR latex composites. Starch is a renewable source of material for fillers in NR latex compounding to obtain composites with multifunctional properties for selected applications. However, starch is a non-reinforcing filler due to its large particle size. The compatibility of NR and starch is another significant issue during the processing of starch-filled NR latex composites due to the nature of both materials. However, based on our research work, a fine dispersion of starch in the rubber matrix can improve the properties of NR latex composites. A good starch dispersion can be achieved through modifications, such as physical or chemical treatments. These treatments include the ball-milling process, ultrasonic process, use of coupling agents, esterification, etherification, and graft copolymerization. The various processing methods of these composites are discussed, specifically pre-vulcanization, latex co-coagulation, an...
Effect of Starch Loading on the Properties of Natural Rubber Compounds
2013
interest in renewable resources and recyclable new materials available at a competitive price. The potential benefits of using naturally occurring materials are many. The use of renewable, rather than petrochemical resources, will extend the nonrenewable petrochemical supplies. It is also possible that less energy will be required to produce and process the bio materials, so reducing carbon dioxide released by energy production and hence, reducing global warming. Biodegradability is an additional benefit of many renewable biological sources of polymers.
Physico-Mechanical Properties of Biodegradable Starch Nanocomposites
Macromolecular Materials and Engineering, 2009
Nanocomposites of cassava starch reinforced with waxy starch nanocrystals were prepared. They showed a 380% increase of the rubbery storage modulus (at 50 8C) and a 40% decrease in the water vapor permeability. X-ray spectra show that the composite was more amorphous than the neat matrix, which was attributed to higher equilibrium water content in the composites. TGA confirmed this result and its thermal derivative suggested the formation of hydrogen bonding between glycerol and the nanocrystals. The reinforcing effect of starch nanocrystals was attributed to strong filler/matrix interactions due to the hydrogen bonding. The decrease of the permeability suggests that the nanocrystals were well dispersed, with few filler/filler interactions.