Starch Acetate Research Articles

Functional properties of extruded foam composites of starch acetate and corn cob fiber

With increasing concerns about environmental protection and garbage handling, natural renewable materials such as starch, cellulose and other natural fibers become more and more popular in packaging materials manufacturing. In this study, physical and mechanical properties of extruded foam composites, prepared from starch acetate and cellulose/corn cob, were evaluated. A split-plot experimental design was used to compare selected functional properties of foams produced from starch acetate blended with ground corncobs, compared to blending with cellulose, and with different ethanol contents. Extrusions were conducted in a twin-screw extruder with 160 °C barrel temperature and 225 rpm screw speed. Physical properties of extrudates were measured including radial expansion ratio, unit density, bulk density, and water absorption index. Mechanical properties including unit spring index, bulk spring index, and compression strength were measured. Scanning electron microscopy was used to compare the macromolecular structures of the two types of starch acetate blends. Blending with corncobs significantly hindered radial expansion of starch acetate foams, whereas cellulose did not affect expansion significantly. Higher compression strength was obtained with higher corncob content. Although ethanol penetration assisted in the formation of a starch acetate–fiber matrix, corncob blends produced inferior linkages and cell development in the foams than foams produced with cellulose blends.

Enhanced film-forming properties for ethyl cellulose and starch acetate using n-alkenyl succinic anhydrides as novel plasticizers.

The aim of this study was to investigate the ability of n-alkenyl succinic anhydrides (n-ASAs) to improve the film-forming characteristics of a novel coating polymer, potato starch acetate degree of substitution 2.8 (SA). n-ASAs were also applied to improve the otherwise brittle properties of ethyl cellulose (EC) aqueous dispersion (Aquacoat) and EC solvent-based films. The effectiveness of two n-ASAs, 2-octenyl succinic anhydride (OSA) and 2-dodecen-1-ylsuccinic anhydride were evaluated as plasticizers. Mechanical properties, both water vapor and drug permeabilities, and glass transition temperatures of the cast free films were measured. Triethyl citrate and dibutyl sebacate were used as reference plasticizers. The long hydrocarbon chain of n-ASA, with its accessible carbonyl groups, enabled a strong plasticization effect on the tested polymers. Due to the excellent mechanical properties (i.e., a tough film structure with considerable flexibility) and low permeability of the plasticized films, n-ASAs, and especially OSA proved to be an ideal plasticizer particularly for EC based coatings. Also, the EC aqueous dispersion plasticized with n-ASAs resulted in a markedly enhanced coalescence of the colloidal polymer particles, even at low drying temperatures. In applications where a coating with high flexibility is required, n-ASAs can be used as plasticizers at moderately high concentrations (up to 60-70%, w/w) without losing the high tensile strength, excellent toughness and low permeability of EC and SA films.

POST-EXTRUSION STEAMING OF STARCH ACETATE FOAMS

Post-extrusion steaming was applied to extruded foam blends of starch acetate and cellulose or polylactic acid(PLA). Extrudates were obtained by twin-screw extrusion at 160.C barrel temperature and 225 rpm screw speed for starchacetate -cellulose blends and 150 rpm screw speed for starch acetate-PLA blends. Extrudates were steamed at atmosphericpressure for six different steaming times and time intervals (steamed once for 1, 2, and 4 min and steamed twice for 1, 2, and4 min with 1 min between cycles.) One sample was steamed at 960.3 kPa. Extrudates without post-extrusion steaming wereused for comparison. Radial expansion ratio, unit and bulk densities, unit and bulk spring indices, and thermal conductivityof the steamed and unsteamed samples were measured. Scanning electron micrographs were taken to observe foam cellstructures. The highest radial expansion ratio of starch acetate-cellulose extrudates was obtained after steaming twice for2 min with a 1 min interval between cycles. Thermal conductivity of the foams decreased slightly as the steaming time wasincreased. Functional properties of the post-extrusion steamed starch acetate foams were strongly dependent on the formationof inter-molecular linkages between cooked starch acetate and melted cellulose or PLA.

Enzymatic degradation of and bovine serum albumin release from starch-acetate films.

The effect of acetylation of potato starch on swelling, enzymatic degradation, and bovine serum albumin (BSA, molecular mass 68 kDa) release rate from polymer films was studied. Potato starch and potato starch acetates (SA), having a degree of substitution of 1.9 or 2.6, were investigated. Polymer films were incubated in phosphate buffer solution pH 7.4 in the absence and presence of enzymes (alpha-amylase, amyloglucosidase, esterase) or in human serum. The acetylation of potato starch decreased its swelling considerably. Increased acetylation of starch also considerably retarded its enzymatic degradation. Due to the decreased swelling and degradation of SA films, BSA was released much slower from SA films than from potato starch films, both in the presence and absence of enzymes.

Effects of physical properties for starch acetate powders on tableting.

The aim of the study was to investigate particle and powder properties of various starch acetate powders, to study the effect of these properties on direct compression characteristics, and to evaluate the modification opportunity of physical properties for starch acetate powders by using various drying methods. At the end of the production phase of starch acetate, the slurry of starch acetate was dried using various techniques. Particle, powder, and tableting properties of end products were investigated. Particle size, circularity, surface texture, water content and specific surface area varied according to the particular drying method of choice. However, all powders were freely flowing. Bulk and tapped densities of powders varied in the range of 0.29 to 0.44 g/cm3 and 0.39 to 0.56 g/cm3, respectively. Compaction characteristics revealed that all powders were easily deformed under compression, having yield pressure values of less than 66 MPa according to Heckel analysis. All powders possessed a significant interparticulate bond-forming capacity during compaction. The tensile strength values of tablets varied between 10 and 18 MPa. In conclusion, physical properties of starch acetate could be affected by various drying techniques. A large specific surface area and water content above 4% were favorable properties by direct compression, especially for small, irregular, and rough particles.

Acetylation Enhances the Tabletting Properties of Starch

ABSTRACTThe aim of this study was the evaluation of starch acetate (SA) powders used as tablet excipients. Deformation during powder volume reduction, strain-rate sensitivity, intrinsic elasticity of the materials, and tensile strength of the tablets were examined. Results showed that SA with the lowest degree of substitution (ds) still possessed characteristics of native starch granules. Due to dissolution in synthesis, the properties of higher ds SAs depended on precipitation and drying processes. The acetate moiety, perhaps in combination with existing hydroxyl groups, was a very effective bond-forming substituent. The formation of strong molecular bonds increased, leading to a very firm and intact tablet structure. Small changes existed in compression-induced deformation due to acetylation. Some fragmentation was induced due to the slightly harder and more irregular shape of high-substituted SA particles. The plastic flow under compression was enhanced. Acetylated material was slightly less sensitive to fast elastic recovery in-die, but somewhat more elastic out-of-die. In spite of their superior bonding, SAs under compression behaved similarly to native starches. It was concluded that deformation properties were more the consequence of the molecular chain structure properties of the starch polymer than the effect of the acetate moiety itself. In contrast, the opposite seemed to be the case with the extensive improvement in bond-forming properties.

Microwave-Assisted Solvent-Free or Aqueous-Based Synthesis of Biodegradable Polymers

Microwave radiation was used as the energy source for various types of chemical derivatizations of polysaccharides and for the synthesis of biodegradable polyesters in solvent-free or aqueous-based reaction systems. A medium to high degree of substitution was obtained for starch acetates, starch succinates, carboxymethyl konjac, aminated starch, and aminated chitosan. Ring-opening polymerization of lactide and e-caprolactone proceeded rapidly even at low power output in the presence of tin octanoate catalyst. Complete monomer conversion and high molecular weight were achieved in less than 6 minutes under nonisothermal conditions. The yield rapidly increased with increasing power output and showed no significant change in a wide range of batch sizes. Polycaprolactone was successfully grafted from starch and konjac acetate in 3 minutes, yielding as high as 24% grafting efficiency and 25% grafting degree.

Predicting plasticization efficiency from three-dimensional molecular structure of a polymer plasticizer.

In polymeric coatings, plasticizers are used to improve the film-forming characteristic of the polymers. In this study, a computerized method (VolSurf with GRID) was used as a novel tool for the prediction plasticization efficiency (beta) of test compounds, and for determining the critical molecular properties needed for polymer plasticization. The film-former, starch acetate DS 2.8 (SA), was plasticized with each of 24 tested compounds. A decrease in glass transition temperature of the plasticized free films (determined by differential scanning calorimeter (DSC)) was used as an indicator for beta. Partial least squares discriminant analysis was used to correlate the experimental data with the theoretical molecular properties of the plasticizers. A good correlation (r2 = 0.77, q2 = 0.58) between the molecular modeling results and the experimental data demonstrated that beta can be predicted from the three-dimensional molecular structure of a compound. Favorable structural properties identified for the potent SA plasticizer were strong hydrogen bonding capacity and a definitive hydrophobic region on the molecule. The VolSurf method is a valuable tool for predicting the plasticization efficiency of a compound. The correlation between experimental and calculated glass transition temperature values verifies that physicochemical properties are primary factors influencing plasticization efficiency of a compound.

Temperatures and ethanol effects on the properties of extruded modified starch

Temperature and blowing agent are major factors influencing the properties of extruded foam materials. This study was conducted to determine the influence of temperature and alcohol content on selected properties and molecular weight of acetylated starch foam. Starch acetate, with degree of substitution of three, was prepared from 70% amylose corn starch and extruded with either 16 or 18% (db) ethanol in a single screw extruder at either 120 or 160°C. Unit and solid densities, specific mechanical energy, compressibility, spring index, water absorption and water solubility indices, glass transition temperature, molecular degradation and degree of substitution (DS) of the starch were measured. The samples extruded at 120°C had lower spring indices and water absorption indices (WAI), but higher compressibility and unit density than acetylated starch extruded at 160°C. The samples extruded with 16% ethanol content on a dry basis had lower spring indices and higher WSI than samples extruded with 18% alcohol. The extruded samples had lower solid density, WSI and WAI as compared to non-extruded acetylated starch. A slight decrease in the average molecular weight was recorded as a result of the extrusion processing. The samples extruded at 160°C had high spring indices and low unit densities and thus were more suitable for use as a loose-fill packaging material.

Dynamic laser speckle pattern in monitoring of local deformation of tablet surface after compression

A method and a sensor device were developed to detect dynamic laser speckle pattern for monitoring of deformation of pharmaceutical tablets after compression. Temporal variations in optical signal revealed local surface deformation of the ibuprofen and the starch acetate tablets as well as anisotropy of tablet surfaces at the inspection location.

Production of short-chain fatty acids followingin vitro fermentation of saccharides, saccharide esters, fructo-oligosaccharides, starches, modified starches and non-starch polysaccharides

A range of carbohydrates including modified starches and short-chain fatty acid esters of di-, tri-, tetra- and polysaccharides were subjected to an in vitro fermentation using human-derived faecal bacteria. The production of the short-chain fatty acids (SCFAs) acetate, propionate and butyrate was monitored at 6, 12, 24 and 36 h for all substrates; however, it was found that the proportions of acids produced were reasonably constant after 6 h. Between substrates there was variation in both the proportions and quantities of acids produced. Relative substrate fermentability as measured by total acid production at 24 h was: sucrose octa-acetate > sucrose > stachyose > pregelatinised starch > Raftilose® > verbascose > raffinose > starch acetate > bleached starch > phosphated distarch phosphate > locust bean gum > corn starch > oxidised starch = starch sodium octenyl succinate > di-starch phosphate > acetylated di-starch adipate = gum arabic > acid-treated starch > gum tragacanth > gum guar > acetylated di-starch phosphate = hydroxypropyl di-starch phosphate > hydroxypropyl starch > pectin > raffinose undeca-acetate > stachyose acetate > gum karaya = cellulose propionate > cellulose acetate > cellulose > cellulose butyrate > hydroxypropyl methyl cellulose > carrageenan > methyl cellulose. Chemically modified starches were similar to corn starch in the amounts of total SCFAs produced at 24 h. Synthetic sugar esters could have potential application as vehicles to deliver supraphysiological amounts of SCFAs during in vivo studies of colonic fermentation. © 2000 Society of Chemical Industry

Polymer Mineralization in Soils: Effects of Cold Storage on Microbial Populations and Biodegradation Potential

Soil retrieval, processing and storage procedures can have a profound effect on soil microorganisms. In particular, changes in soil microbial populations may adversely affect the biological activity of a soil and drastically alter the soil's potential to mineralize added substrates. The effects of cold storage on the biodegradation of a series of test polymers was investigated using two soils—a synthetic soil mix (SM-L8) and a field soil (Bridgehampton silt loam) from Rhode Island (RI-1). Biodegradation tests were conducted using freshly prepared/collected soil and again following storage at 4°C for 3 to 8 months. Prior to each biodegradation test, the soils were incubated at 60% water-holding capacity (WHC) and 25°C to rejuvenate the microbial populations; the soils were incubated for periods of 48 h (freshly collected soil) or 25 days (soils stored at 4°C). Soil microbial populations were assessed by enumerating different segments of the population on agar plates containing different selective media. Mineralization of the test polymers (cellulose, poly-3-hydroxybutyrate, and starch acetate, d.s. 1.5) was monitored using standard respirometric techniques. Our results demonstrated that cold storage had a generally negative effect on the soil microbial populations themselves but that its effect on the capacity of the soil microorganisms to degrade the test polymers varied between soils and polymer type. Whereas cold storage resulted in dramatic shifts in the community structure of the soil microbial populations, substantial restoration of these populations was possible by first conditioning the soils at 60% WHC and ambient temperatures for 25 days. Likewise, although the effects of cold storage on polymer mineralization varied with the test polymer and soil, these effects could be largely offset by including an initial 25-day stabilization period in the test.

Simple Determination Method of Degree of Substitution for Starch Acetate

Abstract To develop a simple method to determine the degree of substitution (dS) for starch ester, we prepared starch acetate with various dS values (0—3) and examined the mode of starch-iodine complex formation for the starch acetate by monitoring the ultraviolet-visible (UV-vis) spectra and their Fourier-transform infrared (FT-IR) spectral changes. The effect of acetylation on the formation of the starch-iodine complex was investigated by monitoring the decrease in absorbance at 680 nm (blue value). The blue value decreased by increasing the standard dS value determined by NMR for starch acetate, but two different correlations between the blue values and the dS values were observed for the low- and highly-substituted starch acetate. The FT-IR spectra for starch acetate particles were measured using a diffuse reflection method. The peak areas and absorbances of the bands assigned to the acetyl group showed a poor correlation with standard dS values from the NMR. On the other hand, the FT-IR peaks assigned to sodium acetate produced by saponification of the starch acetate could be detected using the ATR (attenuated total reflection) method; they showed a good correlation with the standard dS values from the NMR. From these results, it was concluded that the ATR method should be available for the dS determination of starch acetate.

Physical and Molecular Properties of Starch Acetates Extruded with Water and Ethanol

Starch acetate with degrees of substitution of 2 and 3 was extruded with either water or ethanol in a single screw extruder. Properties of the extrudates such as unit and solid density, specific mechanical energy, water absorption and water solubility indices, and molecular degradation and degree of substitution (DS) of the starch were measured. The samples extruded with water had lower spring indices, lower water absorption, and higher solid density than acetylated starch extruded with ethanol. The samples with DS of 2 required less specific mechanical energy and had higher solid density and water absorption indices than starch with DS of 3. Both independent variables influenced unit density and water solubility indices. A slight decrease in the average molecular weight was registered as a result of the extrusion processing.

Optical surface roughness study of starch acetate compacts

Optical surface roughness of starch acetate compacts was investigated by specular reflection of a laser beam as a function of angle of incidence. The intensity data was fitted using the model of Gaussian and Lorentzian curves to solve numerical values for optical surface roughness which was observed to be order of 1 μm with the present samples.

Evaluation of compatibility of poly(vinyl chloride)/starch acetate blends using simple techniques

Evaluation of compatibility of poly(vinyl chloride)/starch acetate blends using simple techniques

Evaluation of compatibility of poly(vinyl chloride)/starch acetate blends using simple techniques

Solution blending of poly(vinyl chloride) (PVC) and starch acetate (d.s. 2.5) synthesized in our laboratory was carried out in 1,4-dioxane. The compatibility of these blends based on the heat of mixing and the free-energy concept was examined theoretically. Experimental evidence for the compatibility of these blends was derived from viscometric and ultrasonic studies and density measurements. Interaction parameters suggest that polymer–polymer interaction is greater than polymer–solvent interaction in the blends under study. All the experimental and theoretical evidence show that the blends are incompatible at the compositions studied. Morphological studies showed a uniform dispersion of starch acetate in PVC. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 71: 1851–1861, 1999

Phase systems of starch acetate and cellulose acetate in acetone:water

Starch acetate (SA) with a degree of substitution (ds) of 2.1–3.0 can be blended with cellulose acetate (CA) with a ds ∼2.5 to make 25–30 wt.% blended solutions in acetone:water to dry spin fibers. To develop solubility and phase information, a modified CCF/CCC statistical designed experiment at 5 to 10 wt.% solids was completed. This was based on five factors: (1) acetyl value, (2) acetone vs. water concentration, (3) ratio of SA to CA, (4) total weight of solids in the solution, and (5) mixing temperature. The resulting solubility information can be used to predict the stability of SA:CA blends at the higher concentration and temperature ranges that are commonly used for fiber spinning. The data were divided into two sets, A and B, based on whether the SA:CA solutions formed one or two phases. Both sets contained 60 experimental runs and only four responses will be discussed in this paper. The phase type (one or two), percent of SA in each phase measured at 25°C and 35°C, and haze. The most significant factors influencing phase type is SA concentration and the interaction of SA percent and the total solids concentration. This is a nonlinear response. Low amounts of SA (<20%) or large amounts (>90%) are predicting to have a one phase system and amounts between 20 to 90% will tend to give a two phase systems. These results are consistent with microscopy and differential scanning calorimetry (DSC), measurements on SA:CA fibers.

A Biogradable Starch Based Coating to Waterproof Hydrophilic Materials

In this work, the efficiency of starch acetylation to reduce water sensitivity of hydrophilic materials was investigated. Starch acetate was either included in foamed starch trays and/or used to coat these trays, wheat gluten based films or paper sheets. The water sensitivity of these foamed trays (quantity and kinetics of water uptake) is shown to decrease when starch acetate content of the foam increases. The coating of the hydrophilic trays with starch triacetate is detailled. The biodegradability of the coating was also unambigously demonstrated. Whatever the nature of the foam, the coating allowed in all cases to slow down the water uptake but best results were obtained in the case of a coated foam prepared with a starch-starch acetate blend. The coating of wheat gluten films was tested with disappointing results because of chemical incompatibility between wheat gluten and starch acetate. In the case of paper sheet coating, the efficiency in water sensitivity reduction increased with the thickness of the coating film. However, the water sensitivity of this coated paper remained higher than paper coated with polyethylene (with a similar coating thickness).

Investigation of the Plasticizing Effect of Dicarboxylic Acid Diesters on Starch Acetate

A study was made of the applicability of dicarboxylic acid diesters for the plasticization of starch acetate. The ratio of the carboxyl and methylene groups was found to be the most important criterion for the use of this group of substances. This ratio should have values between 0.45 and 0.66. From the available dicarboxylic acid diesters, the diethyl esters and dibutyl esters were investigated.