Effect of Glycerol on Water Vapor Sorption and Mechanical Properties of Starch/Clay Composite Films

Plasticized starch/clay composite films were prepared by casting aqueous solutions containing oxidized corn starch, different concentrations of glycerol as a plasticizer and 5% clay (sodium montmorillonite, Na⁺‐MMT) on the basis of dry starch. The water‐binding properties of the composite films were evaluated by water vapor sorption isotherms at room temperature and various relative humidities (RHs). Mechanical properties and abrasion resistance were also analyzed for the films with varying glycerol contents at 68% RH and room temperature. Changes in water sorption isotherms suggested that glycerol interacted with both water and starch in a complicated way. A saturation phenomenon of glycerol, depending on RH, was observed based on the isotherms. Above this saturation content, phase separation of the system occurred with the appearance of free glycerol. According to mechanical performance and abrasion resistance, as well as water vapor sorption of the starch blend films, the three‐stage transition was presented to be related to the state of glycerol in the blend system, i.e. adsorption of glycerol onto H‐bonding sites of starch, supersaturation of glycerol as plasticizer and further supersaturation of glycerol. Only above the supersaturation content can glycerol play a plasticizer role in starch‐based composites.     

淀粉-脂肪酸改性高岭土的制备及其在包装纸上的应用

To improve the bondability between clay filler and lignocellulosic fiber,Kaolin clay particles were modified using a starch-fatty acid complex method.The coating efficiency of starch on clay particle surfaces was investigated by measuring the dissolved starch in the supernatant.The experimental results indicated that more than 98%of the applied starch was precipitated onto the surface of the filler,and the resulting starch-fatty acid-clay composites had relatively good resistance against moderate shear force.The morphology,particle size,andζpotential of the starch modified filler were also determined with scanning electron microscopy,Malvern particle size analyzer,and Malvern Zetasizer,respectively.An aqueous slurry of linerboard pulp containing 5～15wt%modified fillers was used for handsheet preparation,and the effects of the addition of modified filler on the paper properties were studied.At a dosage of 10%of the modified filler(based on filler), the retention of the filler was higher than 75%.The strength properties of paper with starch modified fillers were improved by approximately 15%when compared against those of paper with unmodified fillers.     

Retrogradation of Ethylenebisformamide and Sorbitol Plasticized Corn Starch (ESPTPS)

Several thermoplastic starches (TPSs), i.e. ethylenebisformamide, sorbitol and ethylene‐sorbitol plasticized (EPTPS, SPTPS and ESPTPS) were prepared and their retrogradation was investigated by X‐ray diffraction, Fourier‐transform infrared spectroscopy (FT‐IR) and scanning electron microscopy (SEM). These studies revealed that the mixture of ethylenebisformamide (E) and sorbitol (S) was a good plasticizer for corn starch, restraining the retrogradation of the TPSs. The mechanical properties were also investigated of the TPSs after conditioning for 150 days at ambient atmosphere. It indicated that TPS produced by mixed plasticizer possessed better mechanical properties than TPS produced using a single plasticizer (ethylenebisformamide or sorbitol). From the analysis of X‐ray, FT‐IR and SEM data it was hypothesized that some interaction between ethylenebisformamide and sorbitol occurred, which could prevent the plasticizer form separating out of the TPS matrix. As a result, the retrogradation of ESPTPS was limited, resulting in better mechanical properties compared with those of EPTPS and SPTPS.     

复合增塑剂聚乙二醇200与甘油对淀粉/PHA复合膜性能的影响

本文以羟丙基交联木薯淀粉、聚羟基脂肪酸酯(PHA)为成膜基材,甘油(GLY)为主增塑剂,聚乙二醇200(PEG200)为辅增塑剂,有机改性蒙脱土(OMMT)为增强剂,采用挤压吹塑法制备淀粉/PHA复合膜。研究了PEG200与GLY质量比对淀粉/PHA复合膜性能的影响。采用X-射线衍射(XRD)、扫描电镜(SEM)和红外光谱(FT-IR)分别对膜的结构、微观形貌和分子间相互作用进行了表征,并测试了膜的水蒸气阻隔性、机械性能、透光率和色度。结果表明,主增塑剂甘油对淀粉/PHA共混体系具有较好的增塑效果,且随着辅增塑剂PEG200的加入,促进了淀粉、PHA分子与OMMT间纳米插层结构的形成,所成复合膜表面较为平整光滑,且透光率、白度值增加;当PEG200与GLY质量比为8/92时,所成复合膜阻水性较好,具有较高的断裂伸长率;当PEG200与GLY质量比为12/88时,所成复合膜具有较高的抗拉强度和透光率;辅增塑剂PEG200的添加能够增强各分子间的相互作用。在制备淀粉/PHA复合膜中,PEG200是一种较好的增塑剂和增容剂,PEG200与GLY的质量比不宜超过12/88。     

Use of starch granules melting to control the properties of bio‐flour filled polypropylene and poly(butylene succinate) composites: Mechanical properties

The feasibility and industrial potential of using bio‐flours from tropical crop residues, in particular starch containing bio‐flours, for the manufacture of bio‐composites was investigated. Polypropylene (PP) and poly(butylene succinate) (PBS) were compounded with bio‐flours from pineapple skin (P) and from non‐destarched (CS) and destarched (C) cassava root by twin‐screw extrusion. In CS composites, two levels of starch granules melting were achieved by adjusting the extrusion temperature, enabling control of morphological and mechanical properties. The use of bio‐flours reduced tensile strength by 26–48% and impact strength by 14–40% when the proportion of bio‐flour was increased to 40% w/w, while flexural strength initially increased upon addition of bio‐flours, before decreasing at higher loads. The use of compatibilizers, in particular maleic anhydride‐polypropylene (MAPP) in PP composites with 30% bio‐flour resulted in tensile strength similar to non‐compatibilized composites with 10% bio‐flour (34–35 MPa). MAPP also increased flexural strength to higher levels than pure PP, resulting in a stronger, but less flexible material.     

Synthesis and Preparation of Crosslinked Allylglycidyl Ether‐Modified Starch‐Wood Fibre Composites

Native potato starch has been modified with allylglycidyl ether (AGE) under various reaction conditions including different sodium hydroxide and AGE concentrations, reaction temperatures and times. ¹H‐NMR and FT‐IR were used to analyze the products. AGE‐modified starch, with two degrees of substitution (DS), namely DS = 1.3 and DS = 2.3, was synthesized and used for preparation of a new family of crosslinked composites reinforced with various amounts of bleached softwood fibres. Composite premixes of modified starch, wood fibres and ethylene glycol dimethacrylate (EGDA) were cured in a hot press using 2% (w/w) of benzoyl peroxide at 150°C under high pressure for 10 min. The matrix with high degree of substitution exhibited good processability and was easily processed even for the highest fibre contents, up to 70% (w/w). In addition, scanning electron micrographs showed good dispersion and adhesion between the starch matrix with high degree of substitution and fibre. The original poor mechanical properties of the cured modified starch were markedly improved by the addition of wood fibres. In the extractions tests cured high‐DS and low‐DS composite samples showed weight losses in the range of 1 and 15% (w/w), respectively. No unreacted crosslinker ethylene glycol dimethacrylate was detected in the solutes as determined by NMR.     

Reinforced Thermoplastic Acetylated Starch with Layered Silicates

Montmorillonite (MMT) and organically modified montmorillonite (OMMT) were utilized to reinforce the thermoplastic acetylated starch (TPAS) composite prepared with glycerol as a plasticizer. After the addition of layered silicates, the restriction of the motion of the intercalated acetylated starch molecular chains by the clay layer sheets led to an increase in melt viscosity and equilibrium torque. As expected, the tensile strength and storage modulus of the TPAS composite were remarkably enhanced due to the interaction of layered silicates with the TPAS matrix, but the thermal stability of the TPAS composite was not obviously improved. The greater reinforcing effect of OMMT than that of MMT could be attributed to the better dispersion of OMMT in the TPAS matrix, resulting from the larger distance between OMMT layers after the modification by organic ammonium cations with long alkyl chains.     

Physical and Mechanical Properties of Durum Wheat (Triticum durum) Starch Films Prepared with A‐ and B‐type Granules

The use of starch for the production of biodegradable materials has been increasing. Wheat is an important source, however, durum wheat starch and its separated granular components had not been evaluated for this purpose. The aim of this study was to evaluate the physical and mechanical properties of durum wheat starch films when prepared with a distribution of different granular‐sized starches (A‐ and B‐type). Starch was isolated, and the A and B populations of granules were separated. Films were prepared by casting. Glycerol (G) was used as a plasticizer in concentrations of 25% and 40%, respectively. Starch films were evaluated using scanning electron microscopy (SEM), mechanical properties (tensile strength, TS, elongation at break, E, elastic modulus, EM), solubility, and X‐ray diffraction (XRD). Durum wheat starch films were transparent, flexible, and, according to SEM, highly homogeneous. Films prepared with 25% G showed brittle material behavior (TS = 42–50 MPa, E = 1.4–2.7%, and EM = 31–34 MPa), whereas those prepared with 40% G had ductile material characteristics (TS = 11–17 MPa, E = 4–41%, and EM = 4–11.3 MPa). These mechanical properties of the films were significantly affected by the glycerol concentration and the starch granule type used. The film solubility was low when compared to those reported in other studies. It increased with increasing plasticizer concentration. According to the XRD, the films showed a semi‐crystalline structure.     

Aliphatic Amidediol and Glycerol as a Mixed Plasticizer for the Preparation of Thermoplastic Starch

The synthesis of 2‐hydroxy‐N‐[2‐(2‐hydroxy‐propionylamino)‐ethyl]propionamide (“aliphatic amidediol”) is described. Aliphatic amidediol and glycerol were used as a novel mixed plasticizer for corn starch to prepare thermoplastic starch. Fourier transform infrared (FT‐IR) spectroscopy proved that the mixture of aliphatic amidediol and glycerol could form more stable and strong hydrogen bonds with starch molecules than glycerol alone. By scanning electron microscopy (SEM) and X‐ray diffraction (XRD) it was proven that native starch granules and crystalline structures were broken and starch was plasticized. Tensile testing revealed that TPS plasticized by aliphatic amidediol and glycerol (AGPTPS) showed a better mechanical properties than TPS plasticized by glycerol (GPTPS). Furthermore, the water resistance of AGPTPS was better than that of GPTPS. In addition, dynamic mechanical thermal analysis (DMTA) showed that both storage modulus and glass transition temperature (T_g) of AGPTPS were higher than those of GPTPS.     

Mechanical and Thermal Characteristics of Pea Starch Films Plasticized with Monosaccharides and Polyols

Edible starch films were produced from pea starch and various plasticizers (mannose, glucose, fructose, and glycerol and sorbitol) at the ratio of 4.34, 6.50, 8.69, and 10.87 mmol plasticizer per gram of starch. After film specimens were conditioned at 50% relative humidity, mechanical properties (tensile strength, elongation, and modulus of elasticity), water vapor permeability (WVP), moisture content, and thermomechanical properties (G’ and tan8) were determined as a function of plasticizer concentration. At all concentration levels, monosaccharides (mannose, glucose, and fructose) made the starch films stronger (higher tensile strength) and more stretchable than polyols (glycerol and sorbitol), while WVP of monosaccharide‐plasticized starch films were lower than those of polyol‐plasticized starch films, especially at higher plasticizer concentration levels. Except for 4.34 mmol/g of mannose‐plasticized film, all the other films showed similar modulus of elasticity at the same plasticizer concentration. Polyol‐plasticized films had lower T than the monosaccharide‐plasticized films. Glucose‐ and sorbitol‐plasticized films needed more activation energy to go through glass transition than others. After all, research results showed that not only the polyols but also the monosaccharides were effective in plasticizing starch films. It is concluded that molecular size, configuration, total number of functional hydroxyl group of the plasticizer as well as its compatibility of the plasticizers with the polymer could affect the interactions between the plasticizers and starch molecules, and consequently the effectiveness of plasticization.     

Structure and phase behaviour of microcrystalline cellulose in mixture with condensed systems of potato starch

It has been suggested that microcrystalline cellulose (MCC) can be used in biodegradable films to improve techno‐functionality by providing bulk and enhancing mechanical strength. This study aimed to investigate the effect of MCC addition on the structural properties of potato starch films. Samples were prepared by hot pressing at 120 °C for 7 min to produce systems that covered a broad range of moisture content and relative humidity. Complimentary experimental techniques, including thermomechanical analysis, FTIR, wide‐angle X‐ray diffraction and SEM, were employed to examine the micro‐ and macromolecular characteristics in these mixtures. Both moisture content and the presence of MCC have a plasticising effect on the composites yielding a reduction in its glass transition temperature. It appears that there is no specific and nontrivial interaction between potato starch and MCC, an outcome which indicates that the cellulose fibres act as inert filler in the polymeric composite.     

Effects of Extrusion Temperature and Plasticizers on the Physical and Functional Properties of Starch Films

Cornstarch, at 20% moisture content (dry basis, d.b.), was mixed with glycerol at 3:1 ratio to form the base material for extruded starch films. Stearic acid, sucrose and urea, at varying concentrations, were tested as secondary plasticizers for the starch‐glycerol mixture. The ingredients were extruded at 110 and 120°C barrel temperatures to determine the effects of extrusion temperature, plasticizer type and their concentrations on the film‐forming characteristics of starch, as well as their effects on selected physical and functional properties of the films. The physical and mechanical properties of the films were studied by scanning electron microscopy (SEM) and tensile testing, while the glass transition and gelatinization properties were analyzed using differential scanning calorimetry (DSC). The interactions between the functional groups of starch and plasticizers were investigated using Fourier‐transform infrared (FTIR) spectroscopy. The water vapor permeability (WVP) properties of starch films were determined using ASTM standard E96‐95. Scanning electron micrographs exhibited the presence of native and partially melted starch granules in the extruded films. The tensile stress, strain at break and Young's modulus of starch films ranged from 0.9 to 3.2 MPa, 26.9 to 56.2% and 4.5 to 67.7 MPa, respectively. DSC scans displayed two glass transitions in the temperature ranges of 0.1 to 1°C and 9.6 to 12°C. Multiple melting endotherms, including that of amylose‐lipid complexes, were observed in the thermoplastic extrudates. The gelatinization enthalpies of the starch in the extruded films varied from 0 to 1.7 J/g, and were dependent largely on the extrusion temperature and plasticizer content. The shift in the FTIR spectral bands, as well as the appearance of double‐peaks, suggested strong hydrogen bonding interactions between the starch and plasticizers. The WVP of starch films ranged from 10.9 to 15.7 g mm h^‐1 m^‐2 kPa^‐1, depending on the extrusion temperature and the type of plasticizer used.     

Physical and Mechanical Properties of Pea Starch Edible Films Containing Beeswax Emulsions

ABSTRACT:  Hydrophobic beeswax emulsions were incorporated into hydrophilic starch films to modify physical, mechanical, and thermal properties of the films. Beeswax was added in the film-forming solution of high-amylose pea starch (35% to 40% amylose w/w) at the level of 0%, 10%, 20%, 30%, and 40% w/w of starch with glycerol as a plasticizer (40/60 of glycerol/starch). Addition of beeswax affected mechanical properties, significantly reducing tensile strength and elongation and increasing elastic modulus. Beeswax addition decreased water vapor permeability and increased oxygen permeability. However, the addition of hydrophobic wax particles in starch films marginally affected these physical properties below 30% beeswax in the films. Beeswax addition at the 40% concentration formed amylose–lipid complex that caused the dramatic changes of physical and thermal properties of the films.     

Oxidized banana starch–polyvinyl alcohol film: Partial characterization

Composites of polyvinyl alcohol, native banana starch, oxidized banana starch using glycerol like plasticizer, were studied by mechanical tests (MT), scanning electronic microscopy (SEM), differential scanning calorimetry (DSC) and solubility in water. The oxidized banana starch showed higher level of carboxyl groups than of carbonyl groups. Composites of native banana starch/polyvinyl alcohol and oxidized banana starch/polyvinyl alcohol showed irregularities, indicating incomplete dispersion of the polymers. However, the film elaborated with the blend oxidized banana starch/polyvinyl alcohol showed the highest mechanical properties and the melting temperature of the first transition, as well as the lowest water vapor permeability, indicating higher interaction between both polymers. The composite oxidized banana starch/polyvinyl alcohol showed higher water solubility than the one of its counterpart with native banana starch at 25°C, and similar values were obtained for both films at 60°C. The oxidation of banana starch in order to elaborate a film blended with polyvinyl alcohol improved some mechanical and barrier properties, and this composite could be used for specific applications in the packing of food.     

Composition and Film Properties of Temperature Responsive,Hydrophobically Modified Potato Starch

The film‐forming properties of hydrophobically modified potato starch were studied to optimize coating and surface sizing formulations for improvement of barrier properties of paper and paperboard. The spontaneous fractionation of a potato starch hydrophobically modified with a quaternary dodecylammonium chloride resulted in an amylose‐rich precipitate with properties differing from those of the original starch. Film formation was investigated in the presence of glycerol and poly(vinyl alcohol) plasticizers. Anti‐plasticization was found to occur at low and intermediate plasticizer levels but highly flexible, continuous films were obtained when 30 parts of plasticizer were added to 100 parts of dry starch. The highest transparency and greatest flexibility were obtained with glycerol, while the hydrophobic film properties were maintained with poly(vinyl alcohol). A study of the glass transition temperatures and melting behavior of starch‐plasticizer films by differential scanning calorimetry gave useful information about the crystallinity of the films.     

Preparation and Characterization of Composites Based on Polylactic Acid and Beeswax with Improved Water Vapor Barrier Properties

Beeswax and a plasticizer (ATBC) were added to polylactic acid (PLA) films in order to enhance the water vapor barrier properties of the films. Beeswax improved the barrier properties; the water vapor permeability in the composite containing 1% beeswax was 58% lower than that of the neat PLA. Fourier transform infrared spectroscopy and X‐ray diffraction analysis revealed that the incorporation of beeswax and ATBC had so little effect on the PLA structure. In addition, the structure of PLA did not vary substantially with the additions. The surfaces of the composites were examined by using field emission scanning electron microscopy. Differential scanning calorimetry results showed that the degree of crystallinity of the PLA films increased with the addition of beeswax and ATBC. However, the tensile strength and elongation at break of the composites containing beeswax were up to approximately 50% lower than those of the neat PLA. Although further study is needed to improve the mechanical properties, the aforementioned results showed that the PLA barrier properties can be improved by the incorporation of a small amount of beeswax and ATBC.     

涂层工艺对PVC膜结构复合材料力学性能的影响

采用涂层法制备高经密机织物增强体PVC膜结构柔性复合材料,以实验为基础分析了涂层前后拉伸性能变化的原因,同时研究了涂层工艺(焙烘温度、涂层厚度、增塑剂份数)对PVC膜材的力学性能的影响。结果表明:涂层厚度对力学性能的影响最明显,增加增塑剂份数可导致膜材的力学性能下降;综合考虑各涂层因素对膜材力学性能的影响,选择焙烘温度160℃、涂层厚度0.685 mm、增塑剂份数50份时,可获得力学性能较佳的膜结构复合材料。     

Mechanical properties of pea starch films associated with xanthan gum and glycerol

The aim of this study was to evaluate the effect of the addition of xanthan gum and glycerol to the starch of green pea with high content of AM (cv. Utrillo) in the preparation of films and their physical characteristics. Filmogenic solution (FS) with different levels of pea starch (3, 4, and 5%), xanthan gum (0, 0.05, and 0.1%), and glycerol (glycerol–starch ratio of 1:5 w/w) were studied. The FS was obtained by boiling (5 min), followed by autoclaving for 1 h at 120°C. The films were prepared by casting. Films prepared only with pea starch were mechanically resistant when compared to other films, prepared with corn, cassava, rice, and even other pea cultivars (yellow, commercial). The tensile strength of these films is comparable to synthetic films prepared with high‐density polyethylene and linear low‐density polyethylene. However, they are films of low elasticity when compared to other films, such as rice starch films, and especially when compared to polyethylene films. The increased concentration of starch in the solution increased the puncture force. The increased concentration of glycerol slightly decreased the film crystallinity and interfered in the mechanical properties of the films, causing reduction of the maximum values of tensile strength, strain at break, and puncture force. The plasticizer also caused an increase of elongation at break. Xanthan gum was important to formation of films; however, it did not affect their mechanical properties.     

淀粉-聚乙烯醇-大豆蛋白改性蒙脱土复合薄膜的结构与性能研究

通过大豆蛋白对天然蒙脱土进行改性,制备淀粉-聚乙烯醇-大豆蛋白改性蒙脱土复合薄膜。利用X射线衍射(XRD),透射电子显微镜(TEM)分析其结构,并且对复合薄膜的机械性能和水蒸气阻隔性能进行了研究。结果表明,当蒙脱土经大豆蛋白改性,黏土层之间的分子间力降低;淀粉、聚乙烯醇、黏土层间的相容性增加,这导致黏土片层在聚合物基质中更好的分散,形成了剥离程度较高的纳米结构。纳米结构的形成,使淀粉/聚乙烯醇薄膜水蒸气透过性显著下降,拉伸强度增加,断裂伸长率下降。     

The Effects of Plasticizers Containing Amide Groups on the Properties of Thermoplastic Starch

Several amide groups‐containing plasticizers for thermoplastic starch (TPS), such as formamide, acetamide, and urea, were studied in this paper with glycerol as reference. The hydrogen bond interaction between starch and plasticizers in TPS was tested by Fourier transform infrared (FT‐IR) spectroscopy. Both the oxygen of the C‐O‐H group and the oxygen of the C‐O‐C group in starch could form hydrogen bonds with these plasticizers. The order of the hydrogen bond‐forming abilities is as follows: urea > formamide > acetamide > polyols. The retrogradation of formamide‐plasticized TPS (FPTPS), acetamide‐plasticized TPS (APTPS) and urea‐plasticized TPS (UPTPS) was investigated at three levels of relative humidity (RH=0, 50 and 100%) using X‐ray diffractometry. Urea and formamide could effectively improve the resistance of TPS towards retrogradation. The studied mechanical properties demonstrated that FPTPS had a good breaking strain but poor breaking stress, while UPTPS had opposite characteristics. The properties of TPS mainly relied on the hydrogen bond‐forming abilities between plasticizers and the starch matrix. On the other hand, the water resistance of TPS mainly depended on the plasticizer. The higher the water absorption of the plasticizer was, the better was the water resistance of the TPS.