PROPERTIES OF BIODEGRADABLE THERMOPLASTIC STARCH

Thermoplastic starch is a kind of modified starch produced by mixing starch with additives and processing the mixture in an extruder. The mechanical properties, including tensile strength and elongation at break, biodegradability and rheological properties were studied. Glycerol and urea, to some extent, can both decrease the tensile strength and increase percentage elongation at break, because the former acts as a plasticizer and the latter can break down interactions among starch macromolecules. Thermoplastic starch shows thermoplasticity and its melt behaves as a pseudoplastic liquid at a low shear rate. Its biodegrading extent is slightly higher than that of native starch. The molecular weight of starch displays a decreasing tendency after thermoplastic modification.

THE STRUCTURE OF THERMOPLASTIC STARCH

The granular structure, crystal structure and gelatinization temp. of thermoplastic starch were studied with a polarized light microscope and a scanning electron microscope, and the crystallinity and crystalline patterns were determined through X ray diffraction. The results indicate that the original granular structure and spherical crystalline structure of starch were disrupted by the action of pressure, heat and shear force with the help of additives. The starch can be melted during extrusion, and part of the spheric crystal was destroyed and changed into a continual amorphous with a few crystalline fractions dispersed in it. The configuration of starch molecules changed from double helices to single helix, which indicated the formation of the complex.

Synthesis of aliphatic amidediol and used as a novel mixed plasticizer for thermoplastic starch

In this paper,aliphatic amidediol was synthesized and mixed with glycerol used as a plasticizer for preparing thermoplastic starch（AGPTPS）.The yield of aliphatic amidediol was 91%.FF-IR expressed that the mixture of aliphatic amidediol and glycerol formed stronger and stable hydrogen bond with starch molecules compared to the native cornstarch.By scanning electron microscope（SEM）native cornstarch granules were proved to transfer to a homogeneous continuous system.After being stored for a period time at room temperature,the mechanical properties of AGPTPS were also studied.As a mixed plasticizer,aliphatic amidediol and glycerol would be practical to extend TPS application scopes.

Blends of Poly(lactic acid) with Thermoplastic Acetylated Starch

Blends of poly（lactic acid）（PLA） and thermoplastic acetylated starch（ATPS） were prepared by means of the melt mixing method. The results show that PLA and ATPS were partially miscible, which was confirmed with the measurement of Tg by dynamic mechanical analysis（DMA） and differrential scanning calorimetry（DSC）. The mechanical and thermal properties of the blends were improved. With increasing the ATPS content, the elongation at break and impact strength were increased. The elongation at break increased from 5% of neat PLA to 25% of the blend PLA/ATPS40. It was found that the cold crystallization behavior of PLA changed evidently by addition of ATPS. The cold crystallization temperature（Tcc） of each of PLA/ATPS blends was found to shift to a lower temperature and the width of exothermic peak became narrow compared with that of neat PLA. The thermogravimetry analysis（TGA） results showed that the peak of derivative weight for ATPS moved to higher temperature with increasing PLA content in PLA/ATPS blends. It can be concluded that PLA could increase the thermal stability of ATPS. The rheological measurement reveals the melt elasticity and viscosity of the blends decreased with the increased concentration of ATPS, which was favorable to the processing properties of PLA.

Thermoplastic Starch Prepared with Different Plasticizers: Relation between Degree of Plasticization and Properties

Ethylene glycol, glycerol, sorbitol, formamide, and urea were used as plasticizers for the preparation of thermoplastic starch（TPS） from corn starch. The properties of TPS were tested by analysis method. The results showed that TPSs were more highly plasticized with amines than alcohols. For the same type of plasticizer, the degree of plasticization decreased as the molecular weight of plasticizer increased. The relationship between plasticization degree and TPS properties was characterized and described by mechanical properties and water absorption. The experimental results showed that when the degree of plasticization increased, the tensile strength decreased and the elongation at breakage and water absorption increased.

A Mixed Plasticizer for the Preparation of Thermoplastic Starch

In this paper, formamide was firstly used as plasticizer to prepare thermoplastic starch (TPS), which could suppress the retrogradation of TPS by X-ray diffractometry (XRD) and show a good flexibility, but was weaker than conventional glycerol-plasticized TPS (GPTPS). When urea was introduced into plasticizer, both the retrogradation and mechanical properties were ameliorated. The tensile stress, strain and energy break of TPS plasticized by urea (wt. 20%) and formamide (wt.10%), respectively, reached 4.83 MPa, 104.6 % and 2.17 N-m (Newton-meter) after it had been stored at relative humidity (RH) 30% for one week.

Influence of Sugarcane Bagasse Fiber Size on Biodegradable Composites of Thermoplastic Starch

Although thermoplastic starch(TPS)is biodegradable,its low mechanical resistance limits its wide application.Sugarcane bagasse(SB)fibers can be used as reinforcement in TPS matrix composites,but the influence of fiber size on the properties of the composite is still unknown.In this study,TPS composites reinforced with SB short fibers of four sizes were processed and characterized in order to analyze the influence of fiber size on the mechanical properties of the TPS/SB composite.It was observed that the interaction between fiber and matrix was good and optimized when the fibers are sifted in sieves between 30 and 50 mesh,obtaining fibers with average length of 1569±640μm and average diameter of 646±166μm.For these composites,increases of more than 660%in the modulus and more than 100%in the maximum tension were verified when compared to the pure TPS.

A Novel Plasticizer for the Preparation of Thermoplastic Starch

in this paper, ethylenebisformamide was synthesized and used as a novel plasticizer for cornstarch to prepare thermoplastic starch （TPS）. FT-IR expressed that ethylenebisformamide formed stronger and stable hydrogen bond with starch molecules compared to the native cornstarch. X-ray diffraction （XRD） showed that the typical A-style crystallinity in the native starch has been destructed. By scanning electron microscope （SEM） native cornstarch granules were proved to transfer to a homogeneous system. After being stored for one week at RH=33%, the mechanical properties of EPTPS was also studied. The elongation reached to 264% utmost. As a novel plasticizer, ethylenebisformamide would be practical to extend TPS application scopes.

Preparation and Characterization of Thermoplastic Starch from Sugar Palm (Arenga pinnata) by Extrusion Method

Sugar palm(Arenga pinnata)starch is considered an important renewable,biodegradable,and eco-friendly polymer,which is derived from agricultural by-products and residues,with great potential for the development of biocomposite materials.This research was aimed at investigating the development of TPS biocomposites from A.pinnata palm starch using an extrusion process.Palm starch,glycerol,and stearic acid were extruded in a twin-screw extruder.Scanning electron microscopy(SEM)analysis of TPS showed that the starch granules were damaged and gelatinized in the extrusion process.The density of TPS was 1.3695 g/mL,lower than that of palm starch,and the addition of stearic acid resulted in increased TPS density.X-ray diffraction(XRD)results showed that palm starch had a C-type pattern crystalline structure.The tensile strength,elongation at break,and modulus of elasticity of TPS were 7.19 MPa,33.95%,and 0.56 GPa,respectively.The addition of stearic acid reduced the tensile strength,elongation at break and modulus of elasticity of TPS.The rheological properties,i.e.,melt flow rate(MFR)and viscosity of TPS,were 7.13 g/10 min and 2482.19 Pa.s,respectively.The presence of stearic acid in TPS resulted in increased MFR and decreased viscosity values.The peak gelatinization temperature of A.pinnata palm starch was 70°C,while Tg of TPS was 65°C.The addition of stearic acid reduced the Tg of TPS.The thermogravimetric analysis(TGA)analysis showed that the addition of glycerol and stearic acid decreased the thermal stability,but extended the temperature range of thermal degradation.TPS derived from A.pinnata palm starch by extrusion method has the potential to be applied in industrial practice as a promising raw material for manufacturing bio-based packaging as a sustainable and green alternative to petroleum-based plastics.

Oxidative Degradation of Thermoplastic Starch Induced by UV Radiation

Among biopolymers,thermoplastic starch(TPS)is a good candidate to obtain biomaterials because of its natural origin,biodegradable character,and processability.Exposure to ultraviolet(UV)radiation causes significant degradation of starch-based materials,inducing photooxidative reactions which result in breaking of polymer chains,production of free radical,and reduction of molar mass.These changes produce a deterioration of TPS mechanical properties,leading to useless materials after an unpredictable time.In this work,changes induced on TPS by UV radiation,analyzing structural properties and mechanical behavior,are studied.TPS was obtained through thermo-mechanical processing of native corn starch in the presence of water(45%w/w)and glycerol(30%w/w)as plasticizers.Films were obtained by thermocompression and,before testing,specimens were conditioned to reduce material fragility.Photodegradation process was performed by exposing TPS to 264 h UV radiation in a weathering test chamber.Specimen’s weight loss was determined gravimetrically.Chemical changes were studied by Fourier Transform Infrared Spectroscopy(FTIR)and morphological modifications were analyzed by Scanning Electron Microscopy(SEM).Reduction of weight average molar mass was measured by Static Light Scattering(SLS).Changes in mechanical properties were studied from tensile tests.After 96 h exposure,TPS specimens presented a weight reduction of 4-6%,mainly attributed to plasticizers lost by evaporation.SEM observations showed that UV radiation induced morphological changes on TPS,evidenced by an increment of specimens cracking.By FTIR,it was detected the presence of an additional band located at 1726 cm-1 in samples submitted to UV radiation,attributed to the formation of-C=O groups.Weight average molar mass of native starch was in the order of 107 g mol-1.TPS exposure to UV radiation decreased significantly its molar mass,confirming molecular degradation of the biopolymer.When TPS was exposed during 48 h,it was detected a considerable decrease in elongation at break values(~85%),indicating that TPS flexibility was reduced.On the other hand,after 48 h exposure,TPS elastic modulus was 55 times higher than those of the unexposed specimens,evidencing an increase in material rigidity.TPS maximum tensile strength was also increased by UV light,with an increment of^400%after 48 h exposure.Results revealed that starch-based materials can be degraded by exposure to UV radiation,modifying their microstructure and mechanical performance.

光-生物可降解光敏剂/TPS/PBS复合材料的制备及性能研究

为研究聚丁二酸丁二醇酯(PBS)基复合材料的光-生物可降解性能,采用溶融热压法制备了光敏剂/TPS/PBS复合材料,研究了在光敏剂存在条件下TPS对复合材料的机械性能、热性能、光降解性能和生物降解性能的影响。实验结果表明,随着TPS含量的增加,降解速率越快,而复合材料的力学性能随之降低,且材料的结晶性能变化不明显。当TPS质量分数为30%且光敏剂质量分数为0.5%时,复合材料既能保持良好的力学性能,又能表现出良好的降解性能。

Preparation of the Thermoplastic Starch/Montmorillonite Nanocomposites by Melt-intercalation

In this paper, the conception of melt-intercalation was introduced into the natural polymer field, and the thermoplastic starch/ethanolamine-activated montmorillonite (TPS/EMMT) nanocomposites were prepared by extruding the composites of EMMT and TPS, plasticized with ethanolamine/formamide. Wide angle X-ray diffraction (WAXD) and transmission electron microscope (TEM) revealed that TPS was intercalated into the layers of EMMT successfully and formed the intercalation nanocomposites with EMMT. When EMMT content was wt.10%, the mechanical testing indicated that the tensile stress of the nanocomposites reached 9.69 MPa, and the tensile strain reached 74.07%, Youngs modulus increased from the 47.23 MPa of TPS to 184.11 MPa of TPS/EMMT nanocomposites, and breaking energy increased from 1.34 N·m to 2.15 N·m after they had been stored at RH25% for 14 days.

Biocomposites Based on Thermoplastic Starch and Granite Sand Quarry Waste

Granite stone is a by-product of the rock crushing manufacturing.An industrial waste in powder form that causes health problems and environmental pollution.Fine particles fraction can be used as a partial replacement of sand in concrete manufacture.In this work,an alternative exploitation of this waste fraction is proposed.Granite sand(GS)with particles mean size of ~1μm was employed as thermoplastic starch(TPS)filler at different concentrations.Biocomposites were obtained by melt-mixing and thermo-compression,achieving translucent and easy to handle films.A good GS dispersion within the matrix was evidenced by SEM.Mineral presence induced a shift of starch’s melting point to higher values and a better thermal resistance.TPS UV absorption capacity was increased ~90% by GS addition.An increment in TPS Young’s modulus and maximum tensile stress of 5 and 3 times,respectively was observed by adding 5%w/w GS.

Thermal and Mechanical Properties of Thermoplastic Starch and Poly(Vinyl Alcohol-Co-Ethylene)Blends

The interest in thermoplastic starch(TPS)as a substitute material to replace conventional thermoplastics continues especially due its biodegradability,availability,low cost and because it is obtained from renewable sources.However,its poor mechanical properties and its high sensitivity to humidity have limited its use in several applications.Here,the copolymer poly(ethylene-co-vinyl alcohol)(EVOH),with two different ethylene contents,27 and 44 mol%were blended with TPS by extrusion in order to overcome these limitations.The obtained blends were characterized by thermogravimetric analysis(TGA),differential scanning calorimetry(DSC),mechanical tensile testing,Scanning Electron Microscopy(SEM)and moisture absorption test.The addition of EVOH copolymer did not significantly changed the thermal stability of TPS,however it increased the tensile strength in 65%when compared to TPS.The morphology of the blends did not showed two distinct phases,an indication of miscibility or partial miscibility of the components.A decrease of moisture absorption was obtained by the addition of EVOH and is more pronounced for the EVOH with 44% of ethylene.

Extrusion of Thermoplastic Starch: Effect of “Green” and Common Polyethylene on the Hydrophobicity Characteristics

Novel plastics that are biodegradable, environmentally benign, and made from renewable natural resources are currently being researched as alternatives to traditional petroleum-based plastics. One such plastic, thermoplastic starch (TPS) is produced from starch processed at high temperatures in the presence of plasticizers, such as water and glycerol. However, because of its hydrophilic nature, TPS exhibits poor mechanical properties when exposed to environmental conditions, such as rain or humidity. The overall objective of this research work was to produce a thermoplastic starch based material with low water absorption that may be used to replace petroleum-based plastics. With a recent emergence of “green” polyethylene (GPE), sourced from renewable feedstock, it has become possible to develop novel biodegradable polymers for various applications. In this work, GPE was melt blended with starch in three different ways;reactive extrusion of GPE and starch facilitated by maleic anhydride (MAH) and dicumyl peroxide (DCP), melt blending of GPE and starch by extrusion, and melt blending of maleated polyethylene and starch by extrusion. Comprehensive testing and analysis has shown that all methods reduced water absorption significantly with some variations across the board.

Optimization of Extrusion Process Parameters of Recycled High-Density Polyethylene-Thermoplastic Starch Composite for Fused Filament Fabrication

High-density poly-ethylene (HDPE) is a nonbiodegradable recyclable plastic which is widely utilized in single use packaging applications. Consequently, it constitutes a significant amount of plastic waste found in landfills. From literature, it has been shown that parts produced using composites of HDPE with carbohydrate-based polymers, such as thermoplastic starch (TPS), experience mechanical degradation through hydrolytic degradation process. The possible utilization of recycled-HDPE (rHDPE) and TPS composite in nonconventional manufacturing processes such as Fused filament fabrication (FFF) has however not been explored. This study explores the potential application of rHDPE and TPS composites in FFF and optimizes the extrusion process parameters used in rHDPE-TPS filament production process. Taguchi method was utilized to analyze the extrusion process. The extrusion process parameters studied were the spooling speed, extrusion speed and the extrusion temperatures. The response variable studied was the filament diameter. In this research, the maximum TPS content achieved during filament production was 40 wt%. This filament was however challenging to use in FFF printers due to frequent nozzle clogging. Printing was therefore done with filaments that contained 0 - 30 wt% TPS. The experimental results showed that the most significant parameter in extrusion process was the spooling speed, followed by extrusion speed. Extrusion temperature had the least significant influence on the filament diameter. It was observed that increase in TPS content resulted in reduced warping and increased rate of hydrolytic degradation. Mechanical properties of printed parts were investigated and the results showed that increasing TPS content resulted in reduction in tensile strength, reduction in compression strength and increase in stiffness. The findings of this research provide valuable insights to plastic recycling industries and researchers regarding the utilization of recycled HDPE and TPS composites as substitute materials in FFF.

PBAT／TPS共混物的结构、性能和断裂行为

采用双螺杆挤出机,对聚(对苯二甲酸丁二醇酯-己二酸丁二醇酯)(PBAT)和热塑性淀粉(TPS)进行熔融共混,制备了可完全生物降解的PBAT/TPS共混物。采用扫描电子显微镜研究了共混物的微观结构与形态,测试了共混物的性能和应力-应变行为。结果表明,通过注射成型能够得到TPS原位微纤;PBAT/TPS共混物中存在PBAT相、甘油富集相和TPS富集相,TPS在PBAT中以微纤和颗粒状存在,在剪切较强的区域,TPS以微纤为主,伴有少量的TPS颗粒,在剪切较弱的芯层,TPS主要以颗粒为主;TPS同PBAT间具有较好的相容性,在拉伸过程中,通过原位微纤增强和TPS颗粒变形成纤两种增强模式提高了共混物的拉伸强度,使得共混物在高TPS含量下仍具有较好的力学性能。

可生物降解TPS／PBAT复合材料的制备

将热塑性淀粉(TPS)与聚(对苯二甲酸丁二醇酯-己二酸丁二醇脂)(PBAT)熔融共混并挤出,制备了可完全生物降解的TPS/PBAT复合材料。采用X射线衍射仪和扫描电子显微镜研究了复合材料的微观结构与形态,测试了不同组分复合材料的性能。结果表明:加入PBAT后,复合材料的熔体流动性明显提高;拉伸强度从6.36MPa先下降到3.31MPa,然后升高到12.98MPa;PBAT的加入抑制了支链淀粉分子的重结晶,降低了复合材料的吸水率。

亚麻纤维/PBS/TPS复合材料的制备及性能研究

以玉米淀粉为原料,通过挤出加工制得热塑性淀粉(TPS)。再将TPS与聚丁二酸丁二醇酯(PBS)共混,加入亚麻纤维强化,制得复合材料。分析了TPS试样和复合材料试样的断面微观结构,研究了PBS含量、纤维添加量和硅烷偶联剂(KH-550)对TPS/PBS共混物力学性能的影响。进一步通过正交试验分析优化了复合材料的制备工艺参数。实验研究表明,丙三醇是制备TPS的合适的增塑剂,挤出加工能够较好地改变淀粉分子结构,使其具有热塑性。共混物的力学性能随着PBS含量的增加而增加。亚麻纤维和KH-550都能够明显地增加复合材料的拉伸强度和弯曲强度,但是复合材料的断裂伸长率降低。对于复合材料的拉伸强度来说,最优化工艺为:PBS质量分数60%、纤维质量分数0.5%、偶联剂质量分数0.2%,注塑加工温度(注塑机温控区温度)为155、160、160、150、145℃。