Influence of plasticizer with different functional groups on thermoplastic starch (original) (raw)
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Influence of Amphiphilic Plasticizer on Properties of Thermoplastic Starch Films
Polymer-Plastics Technology and Engineering, 2017
Thermoplastic starch powders and films were produced by using different combinations of hydrophilic (malic acid and water) and amphiphilic (isoleucine and butyric acid) plasticizers. Spray drying was used to produce thermoplastic starch powder followed by compression molding for the development of films. In all plasticized formulations, the rate of retrogradation was inhibited until the seventh day. The crystallinity and moisture sensitivity of the freshly prepared films were dependent on amphiphilic plasticizer quantity in formulation. Fourier transform infrared spectroscopy and thermogravimetric analysis showed an effective interaction of starch with isoleucine. Isoleucine formulated films showed the highest tensile strength, whereas malic acid-rich films showed better strain values.
Carbohydrate Polymers, 2015
Starch was combined with plasticizers such as glycerol, sorbitol, glycerol/sorbitol and urea/ethanolamine blends by means of high shear extrusion process to prepare thermoplastic starch (TPS). Effect of storage time and plasticizers on the structural stability of melt processed TPS was investigated. Morphological observation, X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopy reveal that melt extrusion process is efficient in transforming granular starch into a plasticized starch for all plasticizer compositions. XRD analysis highlights major changes in the microstructure of plasticized starch, and dependence of crystalline type and degree of crystallinity mainly on the plasticizer composition and storage time. Dynamical mechanical analysis (DMA) yields a decrease of the peak intensity of loss factor with aging time. The effect of ageing on tensile strength also appears to be highly dependent on the plasticizer composition. Thus, through different plasticizer combinations and ageing, starch-based materials with significant differences in tensile properties can be obtained, which may be tuned to meet the requirements of a wide range of applications.
Some effects of processing on the molecular structure and morphology of thermoplastic starch
Carbohydrate Polymers, 2008
Hydroxypropylated and oxidised potato starch (HONPS) was used together with glycerol and water to produce thermoplastic starch. The amount of glycerol was kept constant at 22 parts by weight per 100 parts of dry starch. The thermoplastic starch was converted into films/sheets using three different processing techniques; casting, compression moulding and film blowing. The last two methods represent typical thermoplastic conversion techniques requiring elevated processing temperatures. By means of size-exclusion chromatography, it was found that compression moulding and film blowing led to some degradation of high-molecular weight amylopectin as well as of highmolecular weight amylose-like molecules. The degradation was significantly less pronounced for the cast films. The morphology of the specimens was quite complex and phase separations on different levels were identified. In the cast films and, to a lesser extent, in the compression-moulded specimens, a fine network structure could be distinguished. Such a structure could however not be ascertained in the film-blown material and this is discussed in terms of the thermo-mechanical treatment of the starch materials.
Preparation and characterization of potato starch films plasticized with polyols
The present study investigated the potato starches and polyols which were used to prepare edible films. The amylose content and the gelatinization properties of various potato starches extracted from different potato cultivars were determined. The amylose content of potato starches varied between 11.9 and 20.1%. Onset temperatures of gelatinization of potato starches in excess water varied independently of the amylose content from 58 to 61°C determined using differential scanning calorimetry (DSC). The crystallinity of selected native starches with low, medium and high amylose content was determined by X-ray diffraction. The relative crystallinity was found to be around 10-13% in selected native potato starches containing 13-17% water. The glass transition temperature, crystallization melting behavior and relaxations of polyols, erythritol, sorbitol and xylitol, were determined using (DSC), dielectric analysis (DEA) and dynamic mechanical analysis (DMA). The glass transition temperatures of xylitol and sorbitol decreased as a result of water plasticization. Anhydrous amorphous erythritol crystallized rapidly. Edible films were obtained from solutions containing gelatinized starch, plasticizer (polyol or binary polyol mixture) and water by casting and evaporating water at 35°C. The present study investigated effects of plasticizer type and content on physical and mechanical properties of edible films stored at various relative water vapor pressures (RVP). The crystallinity of edible films with low, medium and high amylose content was determined by X-ray diffraction and they were found to be practically amorphous. Water sorption and water vapor permeability (WVP) of films was affected by the type and content of plasticizer. Water vapor permeability of films increased with increasing plasticizer content and storage RVP. Generally, Young's modulus and tensile strength decreased with increasing plasticizer and water content with a concurrent increase in elongation at break of films. High contents of xylitol and sorbitol resulted in changes in physical and mechanical properties of films probably due to phase separation and crystallization of xylitol and sorbitol which was not observed when binary polyol mixtures were used as plasticizers. The mechanical properties and the water vapor permeability (WVP) of the films were found to be independent of the amylose content.
Physical properties of starch plasticized by a mixture of plasticizers
European Polymer Journal, 2017
Highlights The effect of mixture of plasticizers glycerol and urea on properties of starch was investigated Urea plasticized starch has much higher tensile strength and Young's modulus. Urea is more efficient then glycerol ine destroying the hydrogen bonding in starch.
On the Plasticization Process of Potato Starch: Preparation and Characterization
This study aimed to gain a deep understanding of the preparation mechanism of the thermoplastic potato starch (TPPS) by using melt-mixing as a production method, to pursue the changes occurred on the microstructure, morphology and thermal properties of potato starch, TPPS was prepared using a mixture of potato starch with glycerol and water as plasticizer in an internal mixer. The steps of the phase transition , happening by applying harsh conditions (60 rpm, 160 °C, and 7 min), were followed by monitoring the evolution of torque during the mixing time. It was shown that the granules structure was destroyed and a new phase was formed. This was proved by SEM which gave the evidence that the morphology of the TPPS was homogeneous with the smooth surface means that the mixing conditions used in this work were good enough to obtain the thermoplastic starch with a high level of homogeneity in all dimensions. FTIR analysis allowed deducing the formation of new H-bonds between the starch and plasticizers molecules instead of intra and intermo-lecular H-bonds in the native starch that was destructed through the melt-mixing process., These caused starch chains gain mobility and as the results decreasing in crystallinity, where the XRD analysis exhibited that the crystallinity decreased from 14.5% resulting from B-type in native potato starch to 9% resulting from B-type and VH-type in TPPS. TGA and DSC analysis proved a decreasing in the thermal stability in the TPPS as compared to the starch granules.
Carbohydrate Polymers, 2003
Ageing of gelatinised and partly gelatinised potato starch and wheat starch were investigated in the presence of plasticisers with increasing size and number of OH groups (ethylene glycol, glycerol, threitol, xylitol, glucose, and for potato starch also maltose). The influences of these plasticisers and of granular remnants (ghosts) on recrystallisation were determined by using X-ray diffraction. Recrystallisation of potato starch samples in the presence of plasticisers resulted in crystallinity indices of ,0.5. The largest reduction in potato starch recrystallisation is found for threitol (4 OH) and xylitol (5 OH). In the plasticiser range examined, the crystallisation inducing effect of granular potato starch remnants is reduced better when the plasticiser contains more OH groups. Wheat starch recrystallises to a lesser extent than potato starch, resulting in crystallinity indices of , 0.4. The results for wheat starch do not show clear trends for the influences of plasticiser size and of ghosts. The difference in behaviour of the two starches is probably caused by wheat starch having shorter amylopectin chains. Resulting from these shorter amylopectin chains, the remaining structure in wheat starch ghosts may resemble A-type crystallinity, making it more difficult to form B-type crystals. Alternatively, the trends as found for potato starch may occur, but are less manifest for wheat starch, due to the lower total extent of recrystallisation. Solid state CP/MAS NMR spectra of the wheat starch samples containing ethylene glycol were obtained, in order to compare completely and partly gelatinised systems. The spectra were identical, confirming that the ghost structures do not influence wheat starch recrystallisation. Apparently, wheat starch ghosts do not act as nuclei for crystallisation.
The main aim of this study is to examine the different film preparation methods (Hot air oven method, Microwave oven method, and UV irradiation method) for development of Bio-thermoplastic films from agro waste polysaccharides. The rheological properties were also studied for different combinations of tamarind seed starch (T), okra mucilage polysaccharide (OK), Residual rice bran starch (R) and sugarcane bagasse cellulose (C). Increase in concentration of okra mucilage polysaccharide and sugarcane bagasse cellulose found to highly influence the rheological viscous properties of tamarind starch solution. Increase in concentration of okra mucilage (above 1.5%) in tamarind film matrix solution significantly increased the elongation properties of starch films. Increase in concentration of cellulose (above 1%) in tamarind film matrix solution significantly increased the tensile strength of starch films. The microwave oven method was found to be the quickest method (~10 to 20 min) for biopolymer film preparation. SEM and AFM analysis revealed that UVirradiation method produces stable biothermoplastic films with low surface roughness and high barrier properties. The interaction of starch molecules with other natural polysaccharide produces stable thermoplastic biopolymer films, that can be developed under different processing conditions to eradicate environmental pollution caused by petrochemical plastics.
Industrial Crops and Products, 2011
Thermoplastic starch (TPS) was modified with ascorbic acid and citric acid by melt processing of native starch with glycerol as plasticizer in an intensive batch mixer at 160 • C. It was found that the molar mass decreases with acid content and processing time causing the reduction in melting temperature (T m ). As observed by the results of X-ray diffraction and DSC measurements, crystallinity was not changed by the reaction with organic acids. T m depression with falling molar mass was interpreted on the basis of the effect of concentration of end-chain units, which act as diluents. FTIR did not show any appreciable change in starch chemical compositions, leading to the conclusion that the main changes observed were produced by the variation in molar mass of the material. We demonstrated that it is possible to decrease melt viscosity without the need for more plasticizer thus avoiding side-effects such as an increase in water affinity or relevant changes in the dynamic mechanical properties.