Formamide as the plasticizer for thermoplastic starch

As a novel plasticizer, formamide was tested in thermoplastic starch (TPS), in which native cornstarch granules were proved to transfer to a continuous phase by scanning electron microscope (SEM) and the hydrogen bond interaction between plasticizer and starch was proved by Fourier transform infrared (FTIR) spectroscopy. Mechanical tests showed that tensile strength and Young's modulus of formamide‐plasticized TPS (FPTPS) were lower than glycerol‐plasticized TPS (GPTPS) and elongation at break and energy break were higher. The effect of formamide and glycerol on the retrogradation of TPS was studied using X‐ray diffractometry. Formamide could effectively restrain the starch retrogradation at three different relative humidity (RH) environments, because it could form the more stable hydrogen bonds with the starch hydroxy group than glycerol. From these results, we found that the elongation at break, energy break, and the retrogradation of TPS were ameliorated by formamide. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 1769–1773, 2004     

纤维增强尿素和甲酰胺混合塑化热塑性淀粉

使用尿素和甲酰胺混合塑化剂制备的热塑性淀粉(UFPTPS)可以有效抑制淀粉的回生。用这种热塑性淀粉作为短棉绒纤维的基质,制备的纤维增强热塑性淀粉(FRTPS)可以提高其力学性能和耐水性能。扫描电镜显示了短棉绒纤维较好地分散在UFPTPS中,纤维和淀粉结合良好。X ray衍射说明加入纤维后作为基质的UFPTPS仍可以抑制淀粉回生。纤维质量分数对FRTPS力学性能影响的研究显示,随着w(纤维)=0%提高到20%,FRTPS拉伸强度翻番达到10 16MPa,杨氏模量达到97 85N/mm2;伸长率从105%降到17%,断裂能从2 158N·m降到0 573N·m。随着水质量分数的增加,增强效应逐渐被弱化,在高水含量[w(水)>30%]时,水分和纤维质量分数对强度没有影响。FRTPS与UFPTPS相比,耐水性明显提高。     

Preparation and properties of thermoplastic pea starch using N,N‐bis(2‐hydroxyethyl)formamide as the plasticizer

N,N‐bis(2‐hydroxyethyl)formamide (BHF) was synthesized efficiently and used as a new plasticizer for pea starch to prepare thermoplastic starch (TPS). The hydrogen bond interaction between BHF and pea starch was proven by Fourier‐transform infrared (FT‐IR) spectroscopy. As detected by scanning electron microscope (SEM), pea starch granules were completely disrupted, and the homogeneous materials were obtained. The crystallinity of pea starch and BHF‐plasticized thermoplastic pea starch (BTPS) was characterized by X‐ray diffraction (XRD). Rheological properties of TPS were analyzed. The water resistance of BTPS was better than that of glycerol‐plasticized thermoplastic pea starch (GTPS). At RH 33%, the tensile strength of BTPS was higher than that of GTPS for TPS containing 30% plasticizer. POLYM. ENG. SCI., 2010. © 2009 Society of Plastics Engineers     

无机纳米材料增强尿素和甲酰胺混合塑化热塑性淀粉

用尿素和甲酰胺混合塑化剂制备的热塑性淀粉(UFPTPS)可以有效抑制淀粉的重结晶,用这种热塑性淀粉作为纳米S iO2或纳米CaCO3的基质,制备了无机纳米增强热塑性淀粉(NRTPS)。扫描电镜(SEM)显示了纳米S iO2和CaCO3含量对UFPTPS塑化后微观形貌的影响。红外光谱(FTIR)显示了纳米S iO2或CaCO3和淀粉可以发生作用,淀粉与纳米S iO2的相互作用要大于纳米CaCO3。X射线衍射说明,加入纳米S iO2或纳米CaCO3后,作为基质的UFPTPS仍可以抑制淀粉重结晶。纳米S iO2和纳米CaCO3均对UFPTPS起到增强的作用,在w(H2O)=10%时,S iO2增强UFPTPS的强度由UFPTPS的5.67 MPa增加到9.67 MPa;CaCO3增强UFPTPS的强度由UFPTPS的5.67 MPa增加到8.61 MPa。水含量再增加,增强效应逐渐弱化,w(H2O)>23%后,水分对材料力学性能影响很小。与UFPTPS相比,NRTPS耐水性明显提高,在100%相对湿度下,S iO2增强UFPTPS材料在w(S iO2)=1%时材料耐水性最好,平衡时w(H2O)=45%;CaCO3增强UFPTPS材料耐水性随着CaCO3含量增加而提高,w(CaCO3)=3%时材料耐水性最好,平衡时w(H2O)=41%。     

Optimizing the mechanical and physical properties of thermoplastic starch via tuning the molecular microstructure through co‐plasticization by sorbitol and glycerol

Nowadays, environmental hazards caused by plastic wastes are a major concern in academia and industry. Utilization of biodegradable polymers derived from renewable sources for replacing common petroleum‐based plastics is a potential solution for reducing the problem. In this regard, starch has become one of the most promising alternatives to non‐biodegradable polymers for depleting plastic waste thanks to its low expense, abundance, renewability and biodegradability. However, the main drawbacks of starch are its poor processability, weak mechanical properties and severe hydrophilicity. In this work, thermoplastic starch (TPS) samples have been prepared using glycerol and sorbitol as co‐plasticizers in a laboratory co‐rotating twin screw extruder. Based on the mechanical test results, glycerol caused higher elongation to break but had lower tensile strength and elastic modulus compared to sorbitol plasticized starch. Fourier transform infrared spectroscopy and DSC results indicated that the hydrogen bond interaction between starch chains and plasticizers could be improved by replacing glycerol by sorbitol, which resulted in higher resistance against retrogradation proved by XRD results. TGA illustrated that the higher the sorbitol to glycerol ratio was, the more stable was the TPS. Using a proper amount of plasticizers (42 wt% total plasticizer, sorbitol to glycerol ratio 2:1) led to the preparation of a TPS sample with optimized properties including enhanced mechanical properties, high thermal stability, strong hydrogen bond formation and high resistance against retrogradation. © 2017 Society of Chemical Industry     

尿素和甲酰胺混合塑化热塑性淀粉／纳米黏土复合材料性能研究

使用尿素和甲酰胺混合塑化剂制备的热塑性淀粉（UFPTPS）可以有效抑制淀粉的重结晶，并用这种热塑性淀粉作为纳米黏土高岭土和蒙脱土的基质，制备了纳米黏土增强UFPTPS。扫描电镜表明，随着黏土含量的增加，塑化效果逐渐变差，3％（质量含量，下同）高岭土或蒙脱土增强的UFPTPS中可以看到残存的淀粉颗粒和未熔融的淀粉。红外光谱表明，淀粉中C-O-H基团和C-O-C基团都参加了与黏土的相互作用。热重分析表明，纳米黏土提高了热塑性淀粉的热稳定性。X射线衍射说明加入纳米黏土后作为基质的UFPTPS仍可以抑制淀粉重结晶。纳米黏土对UFPTPS起到增强的作用。随着水含量的增加，增强效应逐渐被弱化，在高水含量（23％）时，水分对材料力学性能影响很小。与UFPTPS相比，纳米黏土增强UFPTPS耐水性明显提高。     

The Effects of Different Plasticizers on the Properties of Thermoplastic Starch as Solid Polymer Electrolytes

Plasticizers with amide groups (urea and formamide) and polyols (glycerol, glucose, and sorbitol) were used to prepare thermoplastic starch (TPS) containing NaCl salt as solid polymer electrolytes (SPE). Fourier Transform infrared (FT‐IR) spectroscopy revealed that both plasticizers and Na⁺ could form the interaction with starch, and plasticizers containing amide groups had stronger hydrogen bond‐forming abilities with starch than polyols. These interactions prevented starch molecules from crystallizing again, indicated by X‐ray diffraction (XRD). Scanning electron microscope (SEM) showed that starch granules were in a molten state and a continuous phase of TPS was formed. Among TPS as SPE, formamide‐plasticized TPS (FPTPS) had the largest elongation at break and lowest tensile stress. The conductance of TPS was sensitive to water. TPS plasticized by solid plasticizers had the higher sensitivity of the conductance to water contents at the low water contents (<0.1). The relationship of the conductance and water contents was in agreement with the second‐order polynomial correlation when water contents were below 0.45. FPTPS had the best conductance as a whole. At the medium water content (0.2), the conductance of FPTPS containing NaCl was about 10^?3 S · cm^?1.

     

Influence of plasticizer with different functional groups on thermoplastic starch

Retrogradation of amorphous thermoplastic starch (TPS) films obtained by compression molding of spray dried modified potato starch was investigated. The aim was to investigate the influence of plasticizers with similar molecular weight but different functionality, i.e., isoleucine, asparagine and malic acid, on the properties of plasticized powder and TPS films. Combinations of malic acid with glycerol, urea, and maltodextrin were also evaluated. Except for isoleucine formulated starch, all samples were obtained as amorphous powders and films. Malic acid was identified as a strong antiretrogradation agent as it inhibited recrystallization of starch over the full range of humidity levels. Malic acid was also found to inhibit the retrogradation of formulations containing urea, glycerol and maltodextrin. The converse of the strong inhibition implied strong moisture absorption and high strain at break values, and low tensile strengths. Malic acid was also identified as a potential crosslinking agent to control swelling of starch‐based products. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42012.     

Preparation and properties of thermoplastic starch/montmorillonite nanocomposites using N,N‐bis(2‐hydroxyethyl)formamide as a new additive

N,N‐Bis(2‐hydroxyethyl)formamide (BHF) was synthesized efficiently and used as a new additive to prepare thermoplastic starch/montmorillonite (TPS/MMT) nanocomposites. Here, BHF acted as both plasticizer for TPS and swelling agent for MMT. The hydrogen bond interaction among BHF, starch, and MMT was proven by Fourier transform infrared (FTIR) spectroscopy. By scanning electron microscope (SEM), starch granules were completely disrupted. Atomic force microscopy demonstrated that partially exfoliated TPS/MMT nanocomposites were formed. The crystallinity of corn starch, MMT, BHF‐plasticized TPS (BTPS), and TPS/MMT nanocomposites was characterized by X‐ray diffraction (XRD), XRD demonstrated that partially intercalated TPS/MMT nanocomposites were formed. The water resistance of TPS/MMT nanocomposites increased compared with that of pure BTPS. Mechanical properties of BTPS and TPS/MMT nanocomposites were examined. POLYM. COMPOS., 2012. © 2011 Society of Plastics Engineers     

Comparison of sorbitol and glycerol as plasticizers for thermoplastic starch in TPS/PLA blends

This article investigates the structure and properties of thermoplastic starch/PLA blends where the TPS phase is plasticized by sorbitol, glycerol, and glycerol/sorbitol mixtures. The blends were prepared using a twin‐screw extruder where starch gelatinization, water removal, and dispersion of TPS into a PLA matrix were carried out sequentially. The plasticizers were added to starch in the first stage of the extruder to allow complete starch gelatinization. The PLA was added at mid‐extruder and thoroughly mixed with the TPS. The plasticizer concentration was varied from 30 to 42% and the TPS content was varied from 27 to 60% on a weight basis. In all investigated blends, the PLA formed the continuous phase and the TPS was the dispersed phase. The viscosity, blend morphology, tensile mechanical properties as well as the thermal properties of the materials were measured. It was found that the glycerol/sorbitol ratio has an important effect on the blend properties. Finer blend morphologies, higher tensile strength and modulus but lower crystallization rate were found for the sorbitol plasticized blends. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Dynamic mechanical and thermal properties of the composites of thermoplastic starch and lanthanum hydroxide nanoparticles

Nanostructured lanthanum (III)‐oxide (La₂O₃) particles were prepared by a polymer complex solution method and further used for the preparation of lanthanum hydroxide (La(OH)₃) nanoparticles. The La(OH)₃ nanopowder was mixed with glycerol‐plasticized maize starch and the effect of the filler on the thermal, mechanical, and viscoelastic properties of the matrix was investigated. It was expected that this nanofiller, which shows an affinity toward OH groups, would strongly affect the physical properties of thermoplastic starch (TPS). The pure TPS and the TPS‐La(OH)₃ nanocomposite films (with 1, 2, and 3 wt % filler) were conditioned at various relative humidities (RHs) (35, 57, 75, and 99% RH). After conditioning at 99% RH, the pure TPS films exhibited higher affinity toward water than the nanocomposites. Differential scanning calorimetric measurements showed that, due to retrogradation effects, the melting enthalpies of the films increased with increasing RH. Dynamic mechanical analysis revealed that the mechanical properties in the linear range strongly depend on both the humidity conditions and the concentration of the filler. The results also show that La(OH)₃ nanoparticles are good reinforcement for TPS films. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Influence of maleic anhydride on the compatibility of thermal plasticized starch and linear low‐density polyethylene

In the presence of dicumyl peroxide, the compatibility of thermal plasticized starch/linear low‐density polyethylene (TPS/LLDPE) blends using maleic anhydride (MAH) as compatibilizer was investigated. The thermal plasticization of starch and its compatibilizing modification with LLDPE was accomplished in a single‐screw extruder at the same time. We prepared three types of blends containing different percentages of TPS and MAH. The content of MAH based on LLDPE was 0, 1, and 2 wt %, respectively. The morphology of the blends was studied by SEM. It was found that, with the addition of MAH, the blends have good interfacial adhesion and finely dispersed TPS and LLDPE phases, which is reflected in the mechanical and thermal properties of the blends. The blends containing MAH showed higher tensile strength, elongation at break, and thermal stability than those of blends without MAH. The rheologic properties of the blends demonstrated the existence of processing. Finally, the dynamic thermal mechanical analysis results indicated that, with the addition of MAH, the compatibility between TPS and LLDPE in the blends was substantially improved. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 686–695, 2004     

基于体积拉伸流场的TPS/OMMT纳米复合材料制备及性能研究

通过基于体积拉伸流场作用为主的双轴偏心转子挤出机制备了热塑性淀粉(TPS)和TPS/有机蒙脱土(OMMT)纳米复合材料,并研究了TPS/OMMT纳米复合材料的微观结构、力学性能、热稳定性及耐水性能.结果 表明,在甘油和拉伸流场的协同作用下,OMMT片层间距增加,并均匀分散在塑化良好的TPS基体中.低含量时,OMMT在T...     

尿素/甲酰胺增塑PVA的性能研究

采用流延成膜法制备了以尿素/甲酰胺为复配增塑剂改性的聚乙烯醇(PVA)改性薄膜。采用FTIR研究了复配增塑剂尿素/甲酰胺和PVA之间的相互作用,采用XRD、DSC、TGA和拉伸性能测定对改性后的PVA膜性能进行了测试表征。结果表明,尿素/甲酰胺能与PVA形成氢键作用,破坏PVA的结晶结构,降低PVA膜的结晶度。尿素/甲酰胺的加入降低了PVA的熔点,提高了PVA的热分解温度。改性后的PVA膜的拉伸强度降低,断裂伸长率提高。     

Microstructural characterization of corn starch‐based porous thermoplastic composites filled with multiwalled carbon nanotubes

Microstructural characterization of corn starch‐based porous thermoplastic (TPS) composites containing various contents (0.1, 0.5, and 1 wt %) of multiwalled carbon nanotubes (MWCNTs) was performed. Corn starch was plasticized with a proper combination of glycerol and stearic acid. TPS composites with MWCNT were prepared conducting melt extrusion followed by injection molding. TPS containing 1 wt % of MWCNTs exhibited higher tensile strength and elastic modulus values than neat TPS. Moreover, TPS electrical conductivity was determined to increase with increasing content of MWCNTs. X‐ray diffraction measurements revealed that incorporation of MWCNTs increased the degree of TPS crsystallinity to some extent. Scanning electron microscopy examination revealed that MWCNT altered TPS surface morphology and tensile failure modes, significantly. Transmission electron microscopy investigation showed that dispersion characteristics of MWCNTs within TPS were in the form of tiny clusters around micro pores of TPS, which is considered influential on electrical conductivity of the resulting composites. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Effect of Morphology on the Biodegradation of Thermoplastic Starch in LDPE/TPS Blends

In this study, thermoplastic starch (TPS) was mixed with low density polyethylene with different melt flow indexes in a one-step extrusion process to produce LDPE/TPS blends varied from 32% to 62% by weight of TPS. The influence of starch content and LDPE viscosity on morphology, biodegradation and tensile properties of LDPE/TPS blends were evaluated. Starch continuity and biodegradability were studied by hydrolytic, enzymatic and bacterial degradation. The LDPE viscosity had a considerable effect on the morphology and the connectivity of the starch particles. Evaluation of hydrolytic extraction showed that blends having TPS content above 50 wt% possessed a full connectivity. Studies of biodegradation indicated that the bacterial attack on starch resulted in weight loss of TPS of 92%, 39% and 22%, for PE1/TPS having 62% and 32% TPS, and PE2/TPS (31% TPS), respectively. Comparatively, the weight loss was more significant at 100%, 66% and 31% by hydrolytic extraction. Differences between these two techniques were discussed in terms of the accessibility of starch domains to microorganisms. Tensile properties (ε_b and E) decreased with increasing exposure time to activated sludge. Changes in tensile properties were highly dependent on the biodegradation rate. PE1/TPS blends having 32% starch remained ductile after 45 days of exposure to bacterial attack.     

Structural,thermal and physico-chemical properties of high density polyethylene/natural rubber/modified cassava starch blends

The utilization of cassava starch as one of the components in high density polyethylene (HDPE)/natural rubber (NR) blends were investigated. The true challenge in producing new materials based on natural resources is to design materials that could level the mechanical properties of existing conventional polymers. In this study, we have focused on characterizing the HDPE/NR blends incorporated with cassava starch in the form of granulates (native and silanized) as well as plasticized starch. Cassava starch acted as a biodegradation component in the HDPE/NR blends and the incorporation of cassava starch reduced thermal stability and the degree of crystallinity in general. Several series of cassava starch modifications were performed in order to improve the final properties of the blends. Cassava starch was treated with a silane coupling agent, and proved to be effective in improving tensile strength. The better dimensional stability and compatibility between the blend phases were obtained in the silane-treated cassava starch, as observed in the dynamic mechanical analysis results. Cassava starch was also converted into a plasticized form (TPS), and from the results, the degree of TPS adhesion at the inter-phase ofthe HDPE/NR-TPS blend was clearly improved, as indicated in the morphology study. Through the comparison of thermal degradation results, the HDPE/NR/TPS blends proved to be superior to the HDPE/NR/particulate starch counterparts.     

Effects of nanosilica on retrogradation properties and structures of thermoplastic cassava starch

Composites of thermoplastic cassava starch (TPS) and nanosilica (SiO₂) were prepared by the melting method. The effect of nano‐SiO₂ on the retrogradation properties and structures of cassava starch was investigated. The retrogradation degree of TPS/nano‐SiO₂ composites increased with increasing retrogradation time. The retrogradation rate of TPS significantly increased after the addition of nano‐SiO₂, but excessive nano‐SiO₂ content leads to a decrease in the retrogradation rate of TPS. According to the Fourier transform infrared spectroscopy results, the retrogradation degree of TPS/nano‐SiO₂ composites increased with the increase of retrogradation time and addition of nano‐SiO₂. Scanning electron microscopy analysis indicated that nano‐SiO₂ particles were uniformly and finely dispersed in the starch materials, but the nano‐SiO₂ particles aggregated in the cassava starch with a further increase in nano‐SiO₂ content. X‐ray diffraction revealed that the crystalline structure of the starch was gradually altered from A‐type to V‐type with the increase of retrogradation time. TPS/SiO₂ composites indicated a mixture of A+V types, and the intensity of the V‐type strengthened with the increase of retrogradation time and SiO₂ content. Polarized light microscopy analysis revealed clear Maltese cross patterns, and the number of spherulites in TPS/nano‐SiO₂ composites increased with increasing retrogradation time and nano‐SiO₂ content, but the retrogradation of starch was inhibited with further increases of nano‐SiO₂ content. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45687.     

Poly(citrate glyceride): a hyperbranched polyester for starch plasticization

Hyperbranched polyesters (HBPETs), terminated with either hydroxyl or carboxyl groups, were prepared from citric acid and glycerol in simple one‐step syntheses. The HBPET structure and degree of branching were investigated using Fourier transform infrared and ¹H NMR spectroscopies and gel permeation chromatography. The HBPET plasticizers were combined with a maize starch via cooking and film formation. The mechanical, thermal, paste and structural properties of the plasticized starch composites were studied in detail using differential scanning calorimetry, thermogravimetric analysis, rapid viscosity analysis and X‐ray diffraction. The HBPETs reduced the pasting viscosity but slightly increased the pasting temperature of the starch. The smaller breakdown and setback values of the plasticized starch pastes relative to those of native starch suggested weaker retrogradation. Compared with glycerol/starch plasticized films, HBPET/starch composite films had lower crystallinity, lower glass transition temperature and better mechanical and thermal properties. The properties of the plasticized starch samples strongly depended on the terminal groups and the molecular weight of the HBPET plasticizers. © 2017 Society of Chemical Industry     

Preparation and characterization of compatible thermoplastic dry starch/poly(lactic acid)

In the presence of glycerol and formamide, one‐step extrusion processing was used to prepare poly(lactic acid) (PLA)/thermoplastic dry starch (DTPS) blends (50/50 wt%) in a single‐screw extruder. The rheological study proved that formamide could improve the fluidity of DTPS and DTPS/PLA blends. With increasing the fluidity of DTPS, a highly dispersed and compatible DTPS/PLA could be achieved by scanning electron microscope (SEM). It was also certain that the plasticization of DTPS was improved. At the same time, Fourier transform infrared (FT‐IR) spectroscopy proved that formamide not only weakened the interaction of starch molecules, but also improved the interaction between DTPS and PLA. So that the blend could achieve more thermal stability in a compatible blend, as shown in TGA. The improvement of compatible in DTPS/PLA blends was also proved by tensile test and Dynamic mechanical thermal analysis (DMTA) in this article. POLYM. COMPOS., 2008. © 2008 Society of Plastics Engineers