Thermoplastic starch plasticizers

Starch, Main sources, Macromolecular composition. Polymer structure and crystallinity. Granule disruption, Thermoplastic starch. Plasticization, Moisture uptake. Degradation, Blends, Composites... 

J. Yu, N. Wang, and X. Ma, The effects of citric acid on the properties of thermoplastic starch plasticized by glycerol. Starch/Stdrke 57,494-504, (2005). 

Gaumont, A.C., Grohens, Y, Lourdin, D., Pillin, 1., Rolland-Sabate, A., and Leroy, E. (2010) Thermoplastic starch plasticized by an ionic liquid. Carbohydr. Polym., 82, 256-263. 

As a polymer is heated through its glass transition, a sudden change in heat capacity occurs. The heat flow measured by the DSC is proportional to the specific heat capacity and hence reveals this transition.Figure 7.14 shows the identification of this region in scans of thermoplastic starch plasticized with glycerol and containing different amounts of citric acid. 

Granular starch can be converted into thermoplastic starch by applying high shear force, heat, and/or plasticizers (e.g., moisture, glycerol) in a separate compounding step. Compounding of starch in Ecoflex can be efficiently performed in a four-stage process ... 

Granular starch is destmcturized to thermoplastic starch using temperature, pressure and plasticizer (e.g., water, glycerol)... 

Ecoflex is an essential component for the processing of renewable raw materials like starch and for producing high quality biodegradable and bio-based plastic films out of them. Ecoflex /thermoplastic starch compounds are used... 

Cooked but unexpanded thermoplastic starches (TPS) have wider applications, because of the fact that approx. 8% of water can be removed after the cooking process by devolatilization at 300 mbar, corresponding to a cooling by approx. 70 °C down to 100°C. That means that the exiting strand does not expand but yields a glassy, plastic-like pellet that can be dried in a fluidized-bed dryer. 

In nature, starch is based on crystalline beads of about 15-100 microns in diameter. Crystalline starch beads in plastics can be used as fillers or can be transformed into thermoplastic starch, which can either be processed alone or in combination with specific synthetic polymers. To make starch thermoplastic, its crystalline structure has to be destroyed by pressure, heat, mechanical work or use of plasticisers. Three main families of starch polymer can be used pure starch, modified starch and fermented starch polymers. 

Biotec s product portfolio includes thermoplastic starch, which can be substituted for petrochemical based plastic packaging. Stanelco s radio frequency sealing technology can be used to process starch polymers without the degradation caused by other methods such as thermal processing. The purchase of Biotec will help the company develop alternatives to petroleum-based packaging. 

Clearly thermoplastic starch based polymers offer a very attractive base for new biodegradable polymers due to their low material cost and ability to be processed on conventional plastic processing equipment. The engineering of more advanced properties into these low cost base materials will continue to be... 

Other effective plasticizers for starch for imparting melt processibility include a variety of low molecular weight compounds, such as glycerol and diethylene glycol, and also polymers such as poly(ethylene-co-vinyl alcohol) [55]. Furthermore, starch plasticized in that manner can be melt blended with minor amounts of hydrophobic thermoplastics, such as polyethylene and poly( methyl methacrylate), to obtain biodisintegratable molded articles with good mechanical properties. 

Thermoplastic starch can be processed as a plastic material, but it is sensitivity to humidity, what makes it unsuitable for most applications. Thus, its principal use is in compostable foams to replace EPS. 

Starch is the major carbohydrate reserve in higher plants and has been a material of choice since the early days of human technology. Recently starch gained new importance as a raw material in the production of plastics, in particular, for the synthesis of monomers to produce polymers such as polydactic acid) and, after chemical modification (e.g. esterification) and thermomechanical processing, to produce thermoplastic starch. This chapter gives a general overview of the most recent research on the development of materials from starch, focusing on thermoplastic starch and the perspectives for future development in this field. A brief review on reactive extrusion of thermoplastic starch is also provided. 

Here we will briefly discuss two major topics related to thermoplastic starch physical chemistry the starch granule destructuration or gelatinization during TPS production and the macromolecular properties of the semicrystalline plasticized starch which include indistinctly thermoplastic starch, destructurized starch and plasticized starch. 

If starch is modified by partially fermenting it, or esterifying or etherification, the resulting material can be extruded by adding plasticizers. Starch-based plastics are readily biodegraded. In most cases, the polymers are also water-soluble. Several suppliers now offer thermoplastic starch. Major markets include soluble films for industrial packaging, films for bags and sacks, and loose fill. 

Starch Plastic Starches can be converted into thermoplastic or thermoset materials. Properties of the individual starches vary depending upon the size and shape of the granules and the amylose/amylopectin ratio. Amylose is a mostly linear chain, and amy-lopectin is a branched glucan. Most starches eontain approximately 20% amylose. " ... 

Natural polymers such as starch and protein are potential alternatives to petroleum-based polymers for a number of applications. Unfortunately, their high solubility in water limit their use for water sensitive applications. To solve this problem thermoplastic starches have been laminated using water-resistant, biodegradable polymers. For example, polylactic acid and P(3HB-co-3HV) were utilised as the outer layers of the stratified polyester/PWS (plasticized wheat starch)/polyester film strucmre in order to improve the mechanical properties and water resistance of PWS which made it useful for food packaging and disposable articles [65]. Moreover, improved physic-chemical interactions between P(3HB-CO-3HV) and wheat straw fibres were achieved with high temperature treatment. It resulted in increased P(3HB-co-3HV) crystallization, increased Young s moduli and lowered values of stress and strain to break than the neat matrix of P(3HB-co-3HV). There was no difference in the biodegradation rate of the polymer [66]. 

A. Taghizadeh, P. Sarazin, B.D. Favis, High molecular weight plasticizers in thermoplastic starch/polyethylene blends. Journal of Materials Science 48, 1799-1811 (2013)... 

Starch can be destructurized using extrusion technologies in specific conditions. Sufficient work, heat and time have to be applied to a cereal-based starch product in the presence of plasticizers to destructurize it. The best plasticizer for starch is water in quantities lower than 45%. Other plasticizers are glycols such as glycerol and sorbitol. Whereas thermoplastic starch can contain a certain amount of granular residue and a few Maltese crosses can be detected in polarized light microscopy, destructurized starch is substantially free from those features. 

Another term that can be found in the literature is thermoplastically processable starch (TPPS), defined as a thermoplastic starch that is substantially water free. TPPS is a form of destructurized starch that is obtained without water, because, instead of it, other high boiling point plasticizers or additives ai e used [68-73],... 

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