Thermoplastically processable starch

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],... 

I. Tomka, Thermoplastically processable starch and a method of making it, US Patent 5 362 777, November 8,1994. 

Thermoplastically processable starch is a modified native starch which is obtained without water, since instead of water, use is made of a plasticizer or additive. The starch is thermoplastically processed together with the additive, and the thermal transition taking place here is exothermic (101-106). 

Thermoplastically processable starch Thermoplastic starch Minimum thermosetting temperature Total solid(s)... 

Thermoplastic starch can also be blended with polyolefins [131 ]. In this case about 50% of thermoplastically processable starch is mixed with 40% of polyethylene and 10% of ethyl acrylate-maleic anhydride copolymer. During this mixing process an esterification reaction takes place between the maleic anydride groups in the copolymer and the free hydroxyl groups in starch. 

Thermoplastically processable starch Thermoplastic starch Tryptophan... 

Tomka I, inventor. 1990. Thermoplastically processable starch and a process for producing it. PCT International Application WO 90/05161. 

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. 

In order to relieve the stresses of compression at higher densities by thermoplastic processes instead of with wire or twine, several conditions must occur. A balance between the pressure, and retention time must be found so that the material is exposed to temperatures of 200° to 300°F (93-150°C), and pressures of 1000 psi to 1500 psi (6.9-10.3 MPa) at moisture levels of 12 to 25 (9, 10). Moisture and agglutinant substances such as soluble sugars, starches, extractives, phenolic acids and lignins which will plasticize at these conditions must be evenly distributed throughout the material. The geometry of the material must allow a uniform fiber matrix and intimate contact between adhesive surfaces during compression. 

Modified processing techniques have been useful for thermoplastic starch polymers. Recent work [45, 46] has examined the use of coextruded sheet processing to produce polyester / thermoplastic wheat starch / polyester multilayer films. They found that adhesion strength between the layers and stability of the interface were crucial properties in controlling the final performance properties of the films. Work by Sousa [47] has examined use of the novel shear controlled orientation injection molding (SCORIM) process to control morpholoiges and provide tensile property increases of thermoplastic starch/synthetic blends. 

However, when the modified starch is processed by itself or as the major component in a blend with other materials using conventional thermoplastic processing techniques, such as molding or extrusion. 

In another patented process, starch was destructurized in the presence of low molecular weight polymers such as polyethylene-vinyl alcohol (EVOH), EAA, poly-e-caprolactone and small amounts of moisture and of a high boiling point plasticizer, using a high shear equipment like a twin-screw extruder [77]. From these materials emerged one of the most successful commercial thermoplastic materials based on starch, which took the name of Mate-Bi . 

In 1980s a breakthrough occurred by processing starch at approximately its natural water content (15%) in a closed volume at temperatures above 100°C. Using conventional injection moulding, glassy, amorphous, thermoplastic starch (TPS) polymers (Tg 60 C) were obtained with moduli similar to those of polypropylene and high-density polyethylene. 

De Graaf R.A., Karman A.P., Janssen L.P.B.M. Material properties and glass transition temperatures of different thermoplastic starches after extrusion processing. Starch 55 (2003) 80. 

In its natural form, starch is not meltable and therefore caimot be processed as a thermoplastic. However, starch granules can be thermoplasticized through a gelatinization process. In this process, the granules are disrupted and the ordered crystalline structure is lost under the influence of plasticizers (e.g., water and glycerol), heat, and shear. The resultant melt-processable starch is often termed thermoplastic starch (TPS). Since the advent of TPS,... 

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