Olivia V. López

Film forming capacity of chemically modified corn starches.

Native starch can be chemically modified to improve its functionality and to expand its uses. Modified starches were characterized and the rheological behavior of filmogenic suspensions was analyzed. The film forming capacity of different chemical modified corn starches was evaluated. Acetylated starch was selected by the characteristics of the resulted films; its optimum concentration was 5% w/w since their films exhibited the lowest water vapor permeability (WVP, 1.26×10(-10)g/msPa). The effect of glycerol as plasticizer on film properties depend on its concentration, being 1.5% w/w those that allows to obtain the lowest WVP value (1.64×10(-11)g/msPa), low film solubility in water and a more compact structure than those of unplasticized films. Mechanical behavior of plasticized acetylated starch films depends on glycerol concentration, being rigid and brittle the unplasticized ones, ductile those containing 1.5% w/w of glycerol and very flexible those with a higher plasticizer content.

Thermoplastic starch films reinforced with talc nanoparticles

Nanocomposite films of thermoplastic corn starch (TPS) with talc particles were obtained by thermo-compression in order to study the effect of filler on structure, optical, and thermal properties. Talc increased the films rigid phase, thus their cross-sections resulted more irregular. Talc preferential orientation within matrix and good compatibility between particles and TPS was observed by SEM. Slight crystalline structure changes in TPS matrix were measured by XRD and DSC, due to talc nucleating effect. Randomly dispersed talc nanoagglomerates and individual platelets were assessed by TEM. Laminar morphology and nano-sized particles allowed that nanocomposite films were optically transparent. TPS-talc films resulted heterogeneous materials, presenting domains rich in glycerol and others rich in starch. Talc incorporation higher than 3%, w/w increased softening resistance of the nanocomposites as stated by DMA. Relaxation temperatures of glycerol-rich phase shifted to higher values since talc reduces the mobility of starch chains.

Agro-industrial residue from starch extraction of Pachyrhizus ahipa as filler of thermoplastic corn starch films.

Biocomposites films based on thermoplastic corn starch (TPS) containing 0.5% w/w fibrous residue from Pachyrhizus ahipa starch extraction (PASR) were obtained by melt-mixing and compression molding. PASR is mainly constituted by remaining cell walls and natural fibers, revealed by Scanning Electron Microscopy (SEM). Chemical composition of the residue indicated that fiber and starch were the principal components. Biocomposites thermo-stability was determined by Thermo-Gravimetric Analysis. A continuous PASR-TPS interface was observed by SEM, as a result of a good adhesion of the fibrous residue to starch matrix. Likewise, films containing PASR presented fewer superficial cracks than TPS ones, whereas their fracture surfaces were more irregular. Besides, the presence of PASR increased starch films roughness, due to fibers agglomerates. Films reinforced with PASR showed significantly lower water vapor permeability (WVP). In addition, PARS filler increased maximum tensile strength and Youngs modulus of TPS films, thus leading to more resistant starch matrixes.

Modified Starches Used as Additives in Enhanced Oil Recovery (EOR)

Enhanced oil recovery (EOR) implementation arises as a supplementary technology to conventional ones, optimizing the not-easily recoverable oil phase. Estimation of oil remnant in reservoirs approaches to seven billion of barrels, after primary and secondary recoveries. One of the EOR strategies implies the use of displacing fluids, such as water-soluble polymers, which are pumped into the reservoir forcing the oil to flow toward the production wells. Thus, the state of the art related to the use of different starch derivatives in EOR is included in this chapter. Besides, diverse synthesis methodologies of the modified starches are presented, analyzing the optimal conditions of each reaction. Particularly, the synthesis of cationic starches is reported since they are the most used in EOR. Modification degree and physicochemical properties of the derivatives are included. Rheological and flow properties of displacing fluids are also discussed as a function of starch concentration.

Mild microwave-assisted synthesis of aluminum-pillared bentonites

Two types of bentonites were modified using a cleaner method to prepare aluminum-pillared clays. This methodology involved a purifying stage, an intercalation process, and a microwave irradiation step at low energy power. Structural changes induced by pillaring process were demonstrated by thermal behavior, as well as morphological characterization. The effect of pillaring process on thermal stability of clays was studied, and the mass lost associated with the dehydroxylation of the octahedral clay sheets was not detected for modified bentonites. In addition, an analysis of their chemical composition and crystalline structure was also performed. Concerning industrial applications of these bentonites, two potential uses were proposed: (1) as reinforcement of different polymers matrices such as thermoplastic starch (TPS), high-density polyethylene (HDPE), and poly (styrene-b-butadiene-b-styrene), SBS; and (2) as removal agent for cadmium (Cd) species present in wastewaters. Bentonite particles reinforced thermoplastic starch matrix and increased ultraviolet barrier capacity of HDPE composites. Besides, bentonites improved the mechanical performance and modified barrier properties of SBS. Regarding effluents purification, an adequate Cd adsorption from aqueous solutions was observed (77%), proving their feasibility to be used as non-conventional removal agents.

Composites and Nanocomposites Based on Starches. Effect of Mineral and Organic Fillers on Processing, Structure, and Final Properties of Starch

Composites development, by incorporating organic or mineral fillers to starch matrices, can be used to improve their final properties. Accordingly, composites of different starch matrices reinforced with organic fillers, as well as, with mineral particles are described in this chapter. In this sense, it was reported, among others, the use of cellulose fibers from different botanical origins and clays particles. Nowadays, both academic and industrial interest in nanoscale fillers is growing since a nanostructured composite could be developed from a polymeric matrix and layered mineral particles. Thus, in this chapter is also included the development of nanocomposites based on thermoplastic starch and talc nanoparticles from different geological origins and morphologies. Processing methods and structural and final properties of composites are described.