Granular starch composites

Particulate-filled composites generally have greater elastic moduli compared to the unfilled resin, and starch-filled composites are no exception. Various models have been developed to describe this effect, and are generally of the form  

In the early 1970s, environmental concerns about the disposal of plastics generated considerable interest in the development of degradable materials.37 This concern 

Griffin32 demonstrated that the decline in properties of starch-filled composites could be mitigated somewhat by treating the surface of the starch granules to make them more hydrophobic. This treatment improved the adhesion and stress transfer across the particle/matrix interface and resulted in improved properties relative to no treatment, although properties were still generally reduced compared to the unfilled polymer. 

Another approach to improving the properties of starch-filled polyolefin materials involves the use of ethylene-acrylate copolymers in blends with PE.45 Addition of copolymers of ethylene with methyl acrylate, ethyl acrylate or butyl acrylate were shown to improve the properties of PE films, allowing for higher starch contents. Coextrusion of starch-containing films with outer layers incorporating oxidative pro-degradants has also been utilized 46 The inner layer can contain up to 40% starch the 

Pretreatment of starch granules by esterification with ethylene-acrylic acid iono-mers has been reported to improve the properties of compression molded PE-starch materials compared to simple melt mixing of the three components.54 Improvements over no treatment with ionomer were limited to starch contents less than about 20%. 

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A fluid loss additive is described that consists of granular starch composition and fine particulate mica [337]. An application comprises a fracturing fluid containing this additive. A method of fracturing a subterranean formation penetrated by a borehole comprises injecting into the borehole and into contact with the formation, at a rate and pressure sufficient to fracture the formation, a fracturing fluid containing the additive in an amount sufficient to provide fluid loss control. 

DUQOl] Duquesne E., Rutot D., Degee P., et al, Synthesis and characterization of compatibihzed poly(epsilon-caprolactone)/granular starch composites , Macromolecular Symposia, vol. 175, pp. 33 3,2001. 

Ratto et al. (1999) has examined poly butylenes sueeinate adipate (PBSA) terpolymer/granular starch composites for blown films and showed they could produce good film tensile properties and control biodegradation with granular starch addition. Thermoplastic starch/cellulose fibre extrudates and injection moulded products were examined by Funke et al. (1998) and they showed a reduction in water adsorption with increasing fibre content. Work by Halley et al. (2001) examined the use of thermoplastic starch-polyester blends for use in mulch film applications noting excellent field performance and biodegradability for these materials. 

Figure 2. Method for producing plastic composites containing granular starch. See text for details.

Other methods, alternative methods of producing lump-free CWS starch have been described. One employs heat-moisture treatment of a mixture of granular starch, a surfactant containing a fatty acid moiety and (optionally) a gum.214 A process for making a corn starch product giving a uniform viscous dispersion when added to boiling water employs heating a mixture of starch, surfactant and water, followed by microwave radiation.215 Compositions that gel at low solids concentrations were prepared by complexation of starches of moderate (20-30%) amylose content with emulsifiers.216... 

Composites of granular starch with poly(hydroxy alkanoates) (PHAs) have been extensively studied. PHAs are produced as energy storage polymers by a wide range of microorganisms. Poly(hydroxy butyrate-co-valerate) (PHBV) copolymers have been commercialized. These copolymers are completely biodegradable, but currently are several times more costly than commodity polymers such as PE and PS. Because of its low cost, starch is an attractive filler for these materials. 

Ma X, Chang PR, Yu J, Stumboig M et al (2009) Properties of biodegradable citric acid-modified granular starch/thermoplastic pea starch composites. Carbohydr Polym 75 1-8... 

Shogren RL (1995) Poly(ethylene oxide)-coated granular starch-poly(hydroxybutyrate-co-hydroxyvalerate) composite materials. J Environ Polym Degrad 3 75-80 Shogren R (1997) Water vapm pmneability of biodegradable polymers. J Environ Polym Degrad... 

The biodegradabihty of native and compatibilized poly(e-caprolactone) (PCL)-granular starch blends in composting and culture conditions was studied. The inherent biodegradability of the host polyester has been shown to increase with compatibilization within the PCL-starch compositions [131]. It was observed that the weight loss during composting increased with the... 

The biodegradability of PCL was studied in blends and composites of modified and granular starch. Four types of PCL-starch compositions were prepared (i) PCL-granular starch blends (ii) hydrophobic coating of starch particles by -butylisocyanate (C4 starch) and octadecyltrichlorosilane (Cig starch), followed by melt blending with PCL (iii) PCL-starch blends... 

Potato starch exhibits different granular stmcture and composition, as opposed to cereal starches, which are responsible for the variation in functional behavior of these starches. Cereal starches exhibit the t5 ical A type X-ray crystalline pattern, whereas potato starch shows the B-form, andlegumesthe mixed state pattern C . The A, B, and C patterns are the different polymeric forms of starch that differ in the packing of amylopectin double helices. The structure of potato starch is discussed in more detail in Chapter 4. 

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