Thermal processing of starch-based polymers

https://digitalcommons.unl.edu/cgi/viewcontent.cgi?article=1024&context=textiles_facpub

Citric acid cross-linking of starch films

Oils, and Polysaccharides Alessandro Gandini,*,†,‡ Talita M. Lacerda,†,‡ Antonio J. F. Carvalho,‡ and Eliane Trovatti†,‡ †Saõ Carlos Institute of Chemistry, University of Saõ Paulo, Avenida Trabalhador Saõ-carlense 400, CEP 13566-590, Saõ Carlos, Saõ Paulo, Brazil ‡Department of Materials Engineering, Saõ Carlos School of Engineering, University of Saõ Paulo, Avenida Joaõ Dagnone 1100, CEP 13563-120, Saõ Carlos, Saõ Paulo, Brazil

Progress of Polymers from Renewable Resources: Furans, Vegetable Oils, and Polysaccharides

Over the coming few decades bioplastic materials are expected to complement and gradually replace some of the fossil oil based materials. Multidisciplinary research efforts have generated a significant level of technical and commercial success towards these bio-based materials. However, extensive application of these bio-based plastics is still challenged by one or more of their possible inherent limitations, such as poor processability, brittleness, hydrophilicity, poor moisture and gas barrier, inferior compatibility, poor electrical, thermal and physical properties. The incorporation of additives such as plasticizers into the biopolymers is a common practice to improve these inherent limitations. Generally, plasticizers are added to both synthetic and bio-based polymeric materials to impart flexibility, improve toughness, and lower the glass transition temperature. This review introduces the most common bio-based plastics and provides an overview of recent advances in the selection and use of plasticizers, and their effect on the performance of these materials. In addition to plasticizers, we also present a perspective of other emerging techniques of improving the overall performance of bio-based plastics. Although a wide variety of bio-based plastics are under development, this review focuses on plasticizers utilized for the most extensively studied bioplastics including poly(lactic acid), polyhydroxyalkanoates, thermoplastic starch, proteinaceous plastics and cellulose acetates. The ongoing challenge and future potentials of plasticizers for bio-based plastics are also discussed.

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Progress in bio-based plastics and plasticizing modifications

Recent advances in starch, polyvinyl alcohol based polymer blends, nanocomposites and their biodegradability

The effects of citric acid on the properties of glycerol-plasticized thermoplastic starch (GPTPS) were studied. In the presence of citric acid and glycerol, native cornstarch granules are transferred to a continuous phase as shown by scanning electron microscopy (SEM). As shown by thermogravimetric analysis (TGA), the improvement in thermal stability confirms that the adhesion between citric acid, glycerol, water and starch in TPS was enhanced with the addition of citric acid. It was proven by Fourier transform infrared (FTIR) spectroscopy that citric acid can form stronger hydrogen-bond interactions with starch than glycerol. Both FTIR spectroscopy and X-ray diffractometry of citric acid-modified GPTPS (CATPS) revealed that citric acid can effectively inhibit starch re-crystallization (i.e. retrogradation), because of the strong hydrogen-bond interaction between citric acid and starch. Rheology studies revealed that citric acid can obviously decrease the shear viscosity and improve the fluidity of TPS. Citric acid can also improve the elongation of GPTPS and ameliorate the water resistance of GPTPS at high relative humidities, but decreased the tensile stress.

The Effects of Citric Acid on the Properties of Thermoplastic Starch Plasticized by Glycerol

The influence of citric acid on the properties of thermoplastic starch/linear low-density polyethylene blends

Mixtures of urea and formamide were tested as plasticizers for thermoplastic starch (TPS). The hydrogen bonding interactions between urea/formamide and starch were investigated by using Fourier-transform infrared spectroscopy (FT-IR). The thermal stability, mechanical properties and starch retrogradation behavior were also studied by thermogravimetric analysis (TGA), tensile testing and X-ray diffraction (XRD), respectively. TPS plasticized by urea (20 wt%) and formamide (10 wt%) showed better thermal stability and water resistance than conventional TPS plasticized by glycerol. Moreover, the tensile stress, strain and energy at break, respectively, reached 4.83 MPa, 104.6 % and 2.17 N m after storing in an atmosphere of relative humidity (RH) of 33 % for one week. At the same time, this mixed plasticizer could effectively restrain the retrogradation of starch. Copyright © 2004 Society of Chemical Industry

Urea and formamide as a mixed plasticizer for thermoplastic starch

In this study, the morphology and the mechanical properties of thermoplastic starch (TPS)/linear low-density polyethylene (LLDPE) blends prepared by one-step and two-step extrusion processing conditions were contrasted. In the presence of citric acid (CA), the compatibility of TPS/PE blends were proved to transfer to a high continuous dispersion in one-step extrusion process by scanning electron microscopy analysis. By increasing the interaction between two phases, the mechanical properties of the blends were markedly improved, even reached the levels of the conventional plastics. The rheological study proved that the viscosity (η) of TPS and TPS/PE blends were both decreasing with increase in the content of CA at the same temperature, which ascribed to the acidity of CA was propitious to fragmentation and dissolution of cornstarch granules, deteriorated the chain entanglement in starch, and weakened the interaction of starch molecules. Both FTIR spectroscopy and thermal properties analysis of TPSs and TPS/PE blends showed that the interactions between starch and plasticizer became stronger in the presence of CA. POLYM. COMPOS. 28:89–97, 2007. © 2007 Society of Plastics Engineers

High performance modified thermoplastic starch/linear low-density polyethylene blends in one-step extrusion

Glycerol and formamide are used as plasticizers to prepare dry thermoplastic starch (DTPS) in a single-screw extruder. Glycerol/formamide—water plasticized starch (TPS) is also studied as a standard. Scanning electron microscopy reveals that more residual granules exist in glycerol-plasticized dry starch than in other blends. After the removal of water, DTPS becomes rigid and fragile. Increasing the formamide content results in a dramatic increase in the elongation of DTPS, and it maintains a high tensile strength. Dynamic mechanical thermal analysis demonstrates that formamide can decrease the glass transition temperature (Tg) of TPS and replace water to form formamide—starch mixtures in DTPS. Thermogravimetric analysis shows that destructurization of the polysaccharide chain is accelerated after removal of water, but it is alleviated by increasing the formamide content. It is also shown using Fourier transform infrared spectroscopy that formamide can form stronger hydrogen-bond interactions with starch ...

Ma Xiaofei

Papers

The Effects of Citric Acid on the Properties of Thermoplastic Starch Plasticized by Glycerol

The influence of citric acid on the properties of thermoplastic starch/linear low-density polyethylene blends

Urea and formamide as a mixed plasticizer for thermoplastic starch

High performance modified thermoplastic starch/linear low-density polyethylene blends in one-step extrusion

An Investigation of the Physical Properties of Extruded Glycerol- and Formamide-Plasticized Cornstarch: