Poly(lactic acid)/coplasticized thermoplastic starch blend: Effect of plasticizer migration on rheological and mechanical properties

Polylactic acid (PLA) and thermoplastic starch (TPS) are known as bio‐based and biodegradable thermoplastic polymers that can be used in different applications owing to their inherent physical and mechanical properties. In order to reduce the higher costs of PLA and tuning its physical and mechanical properties suitable for short life packaging applications, blending of PLA with the TPS, more economical biodegradable polymer, has been considered in academic and industrial researches. However, melt blending of PLA with TPS without compatibilization process caused some drawbacks such as coarsening morphology and declining mechanical properties and ductility because of thermodynamic immiscibility, which may restrict its usage in packaging applications. Subsequently, our approach in this research is compatibilization of PLA/TPS blends by utilization of primary well tuning of TPS formulation with a combination of sorbitol and glycerol plasticizers. In this work, the wide composition range of melt mixed PLA/TPS blends was prepared using a laboratory twin screw extruder. The effects of microstructure on the rheological and mechanical properties of PLA/TPS blends were studied using different methods such as scanning electron microscopy (SEM) images, contact angle, oscillatory shear rheological measurements, and tensile and impact strength mechanical tests. The rheological and mechanical properties were interpreted according to the morphological features and considering the possibility of plasticizer migration from TPS to PLA phase during melt blending. Reduction in complex viscosity and storage modulus of PLA matrix samples indicates the improved melt processability of blends. Finally, in comparison with mechanical results reported in literature, our simple approach yielded the blends with elastic modulus and ductility comparable with those of chemically compatibilized PLA/TPS blends.     

接枝聚乳酸/塑化淀粉共混物的制备与性能研究

为提高聚乳酸(PLA)/淀粉共混物界面作用和降低成本,引入甲基丙烯酸缩水甘油酯(GMA)接枝聚乳酸和塑化淀粉(TPS),通过挤出和注射成型制备接枝聚乳酸/塑化淀粉共混物(PLA-g-GMA/TPS)。红外光谱分析证实,GMA成功接枝到PLA分子链上。对共混物的力学性能、热机械性能、微观形貌、热性能及亲水性等进行了系统研究,结果表明,选择GMA用量为6%(接枝率为1.51%)和TPS用量为10%时的拉伸强度、断裂伸长率及弹性模量最佳,分别为42.6MPa、8.9%及260MPa。FE-SEM观察结果表明,低含量TPS中颗粒被基体包覆或嵌入,界面平整,界面结合力强。DMA和DSC结果显示,不同质量配比的PLA-g-6%GMA/TPS共混物的Tg、储存模量、结晶度、结晶温度及熔融温度仅在小范围内发生变化。吸水率和接触角结果表明,低含量TPS的共混物吸水率和接触角变化幅度均小于高含量TPS体系。     

Ethanolamine as a novel plasticiser for thermoplastic starch

Ethanolamine plasticised thermoplastic starch (ETPS) was prepared using a novel plasticiser ethanolamine. SEM images show that the native starch granules were destroyed, and the ethanolamine made them come into a uniform continuous phase. FTIR spectroscopy showed that the hydrogen bonds between the ethanolamine and starch molecules weakened the strong effect of starch intermolecular and intramolecular hydrogen bonds. The ETPS successfully restrains the re-crystallization of traditional thermoplastic starch plasticised by glycerol (GTPS), which was proved by XRD. The mechanical properties of ETPS, such as Young's modulus and breaking energy and the water absorption were improved. The glass-transition temperature (T_g) and thermal stability were also studied by DSC and TGA.     

Evaluation of some methods of determination of starch for legislative purposes in the European Community.

A newly developed enzymic method for starch purity determination has been designed in response to the search by the European Community (EC) for a reliable and accurate official method for direct total starch measurement of high purity starches. This new method, the Birmingham method, utilizes a multi-enzyme regime, consisting of an (-amylase (E.C. 3.2.1.1), a glucoamylase (E.C. 3.2.1.2) and a pullulanase (E.C. 3.2.1.41), for the complete and specific hydrolysis of starch to glucose. Greater than 99.5 % conversion of most starches to glucose is achieved which is higher than that afforded by other enzymic methods being considered for adoption. In this communication the reliability and accuracy of this method are assessed and demonstrated. Also, some results during its development are presented. Advantages and drawbacks of the other methods for starch purity measurement being investigated/assessed for permanent adoption as an official method of the EC are also discussed.     

The Influence of Pair Spiral Extrusion Equipment on Thermoplastic Potato Starch

Owing to contain a great deal of hydroxyl in Potato Starch, between the molecules and inside of molecules have very strong hydroxyl action. Thus, the liquate temperature is higher than disintegrate temperature, so it is difficult to process. Under the microscope, the microcosmic construction is a polar crystal molecule, and it appears globe predicament.To make the original potato starch into possession thermoplastic, we must make molecule of starch to change construct into amorphous state to form thermoplastic starch colophony. Besides auxiliary agent, shearing stress, temperature, time, pressure and hydrous quantity can affect the quality of starch thermoplastic too. The pair spiral extrude machine is used widely as the machines that are based of the pressure difference, and this extrude course may suffice require.Using the machine of pair spiral extrude of specific combination in the test of thermoplastic starch, the potato starch can be turned into thermoplastic starch of denaturalization preferably under auxiliary agent, shearing stress, temperature, pressure and the certain hydrous quantity.By the action of the technology process condition and the spiral combination, potato starch grains expand and fragmentate; hydroxyl bond cleave between and inside of molecules. Thus, crystallize state is changed into amorphous state. The transmutation of starch molecule property may be seen clearly from X diffraction chart and analyses of the construction property,By means of the denaturation, the crystal area of potato starch is broken,its crystallization degree is decreased,and its molecular chains are in amorphous state. The hydrogen bond among the molecular chain is broken or removed so that the starch structure is changed, making the starch thermoplastic.The processing of thermoplastic starch advances a higher requirement of ingredient water content, and technical conditions. A remodeled twin-screw extruder is used to create an environment to realize the condition of denaturalizing and plasticizing reactions. After the continuous probing, we have successfully developed three types of thermoplastics starch plastic from the potato starch (starch content of all of them is greater than 90%). The fluidity of the thermoplastics starch will be better if the processing is performed under the condition of 4.0-6.0Mpa (pressure) and 80-110℃ (temperature). By doing so, it is shown that there is the possibility of further thermoplastic fabrication upon it.     

Effect of the Extender on Form and Structure of the Thermoplastic Starch

The thermoplastic starch is a complete biodegradable plastic materials, in the fullstarch plastic the thermoplastic starch attained amount to 90% or higher. For the improve on machine properties, general added a extender of 5-10% according to the process method and/or claim of the use properties, the process and use properties of full-starch depend on a kind of the extender to a certainly extent1 As a type of polysaccharide compound, the starch contained a great amount of the polar group-hydroxyl (-OH), These hydroxyl on the chain bounded chain and chain closely together via association of the hydrogen bond, the chain cannot free revolve and twist, so it has not the thermoplasicity. But through thermoplastic denaturation of the starch, the plasticity agent breaked associated of the hydrogen bond between chain and chain, the starch chain may be freely revolved or tensional formation when is heated or forced. So it's plasticity2,3     

Synergistic effect of graphene oxide nanoplatelets and cellulose nanofibers on mechanical,thermal, and barrier properties of thermoplastic starch

In recent years, because of the limited availability of oil resources and the increasing concerns regarding environment protection, much attention has been drawn to produce packaging films based on degradable biopolymers instead of synthetic polymers. On the other hand, because of the high costs of oil extraction, raw materials and film production, and disposing of the waste products of synthetic films, the need to replace these films with less pollutant and more cost‐effective films is growing globally. In this study, to answer the need for replacing synthetic polymer films, nanocomposite films based on thermoplastic starch reinforced with cellulose nanofibers and graphene oxide nanoplatelets were produced and characterized. The results implied that the synergistic effect of cellulose nanofibers and graphene oxide nanoplatelets has played an important role in improving the mechanical properties of the films. The results showed that with the addition of cellulose nanofibers and graphene oxide nanoplatelets, the tensile strength and elastic modulus of starch film were increased from 3 and 32 MPa to 13 and 436 MPa, which corresponds to 438% and 1435% improvement, respectively. In addition, the oxygen permeability resistance and the water vapor transmission for samples containing 3 wt% of graphene oxide nanoplatelets was decreased by 78% and 30% compared with the thermoplastic starch film, respectively. The permeability coefficient of the samples containing 3 wt% graphene oxide nanoplatelets for oxygen, nitrogen, and carbon dioxide have proved to be 0.051, 0.054, and 0.047 barrer, which shows that these films can perform well as packaging films.     

Starch Nanocrystal Fillers in an Acrylic Polymer Matrix

Aqueous suspensions of nanocrystals can be obtained by acid hydrolysis of native waxy maize starch granules. The disruption of waxy maize starch granules by 2.2N HCl hydrolysis has been followed by scanning and transmission electron microscopy and laser granulometry. The mechanical properties of composite materials made of poly(styrene-co-butyl acrylate) filled with starch nanocrystals were characterized by dynamic mechanical analysis. These nanocrystals appeared to be an interesting reinforcing phase in a thermoplastic matrix.     

Mechanical and thermal properties of poly(3-hydroxybutyrate) blends with starch and starch derivatives

Poly(3-hydroxybutyrate) (PHB) is a highly crystalline, biodegradable and biocompatible thermoplastic. However, its limited utilization as a commodity plastic is associated to both high cost and very poor mechanical properties. Blending PHB with a natural polymer, such as starch, is one way to improve its properties and to get low price raw materials, though they are not miscible since there are no strong interactions between the hydrophilic starch and the hydrophobic PHB. In this study binary blends of PHB were prepared with natural starch, starch-adipate and grafted starch-urethane derivatives. The PHB blends were characterized in terms of their mechanical and thermal properties. For all blends a decrease of the Young modulus was observed as compared to the pure PHB. However, blends containing natural starches and starch adipate resulted in brittle materials. A significant decrease of both glass transition temperature (Tg) and melting point (Tm) was observed for all formulations. The best results, lower modulus and Tg were obtained with grafted starch-urethane blends using poly(propylene glycol).     

Research progress in the heat resistance,toughening and filling modification of PLA

Due to its high strength, high modulus, excellent clarity, good biodegradability and biocompatibility, poly(lactic acid) (PLA), a bio-based thermoplastic polyester, has evolved into a competitive commodity material with potential to replace conventional petrochemical-based polymers. However, the wide applications of PLA have been hampered by its native drawbacks, such as low heat distortion temperature (HDT), inherent brittleness and relatively high cost. In recent years, researchers have devoted to breaking above-mentioned bottleneck and attempted to extend the application of PLA. This review will summarize recent work about the modification of PLA, especially focusing on enhancing HDT, toughening and reducing cost.     

A Novel Plasticizer for the Preparation of Thermoplastic Starch

TPS was a biodegradable material based on starch. Starch was an inexpensive and natural renewable polysaccharide, which was widely investigated as the substitute of petroleum-derived plastics. Native starch commonly existed in granule structure with about…     

Thermoplastic toughening of epoxy resins: a critical review

Thermoplastic toughening of epoxy resins has been actively studied since the early 1980s with considerable progress in property improvement and understanding having been made since then. The main advantage in using thermoplastics to toughen epoxy resins is that their incorporation need not result in significant decreases in desirable properties such as modulus and yield strengths as is generally the case when rubbers are used as toughening agents. However, the predominant criteria for achieving optimum toughness enhancement in the thermoplastic toughening of epoxy resins are still not all that clear from the literature. This review has focused upon the importance of the thermoplastic endgroups, the material's morphology, the ductility of the matrix and the chemical structure of the thermoplastic, it summarizes what the authors believe are the important requirements for good thermoplastic toughening. © 1998 John Wiley & Sons, Ltd.     

Thermoplastic elastomers for microfluidics: towards a high-throughput fabrication method of multilayered microfluidic devices

Multilayer soft lithography of polydimethylsiloxane (PDMS) is a well-known method for the fabrication of complex fluidic functions. With advantages and drawbacks, this technique allows fabrication of valves, pumps and micro-mixers. However, the process is inadequate for industrial applications. Here, we report a rapid prototyping technique for the fabrication of multilayer microfluidic devices, using a different and promising class of polymers. Using styrenic thermoplastic elastomers (TPE), we demonstrate a rapid technique for the fabrication and assembly of pneumatically driven valves in a multilayer microfluidic device made completely from thermoplastics. This material solution is transparent, biocompatible and as flexible as PDMS, and has high throughput thermoforming processing characteristics. We established a proof of principle for valving and mixing with three different grades of TPE using an SU-8 master mold. Specific viscoelastic properties of each grade allow us to report enhanced bonding capabilities from room temperature bonding to free pressure thermally assisted bonding. In terms of microfabrication, beyond classically embossing means, we demonstrate a high-throughput thermoforming method, where TPE molding experiments have been carried out without applied pressure and vacuum assistance within an overall cycle time of 180 s. The quality of the obtained thermoplastic systems show robust behavior and an opening/closing frequency of 5 Hz.     

Mechanical properties and enzymic degradation of thermoplastic and granular sago starch filled poly(ε-caprolactone)

The mechanical, morphological and biodegradation properties of two types of poly(ε-caprolactone)/sago starch (PCL/sago) composites were investigated i.e. dried granulated sago starch and undried thermoplastic sago starch (TPSS). Thermoplastic starch was extruded with a twin screw extruder model Haake Rheomix (TW100 attached to a Haake Rheometer (Haake Rheodrive 5000). The composites were compounded with a Haake internal mixer (Haake Rheomix 3000) attached to the Haake Rheometer. Tensile properties were determined with the Monsanto Tensometer T10. A Shimadzu UV-160A visible UV spectrophotometer was used to monitor the liberation of carbohydrate as a consequence of starch hydrolysis by α-glucoamylase. Determining the weight loss of composites as well as the acid liberated from PCL also monitored biodegradation. The results indicate that dried granulated sago starch function better as fillers in terms of mechanical properties and the ease of biodegradation. However, TPSS imparted better yield strength to the composites. Poor wetting of starch accounts for the decreased mechanical properties at higher starch concentration as agglomeration occurs. While the rigid granular starch retained their shape in the composites, thermoplastic starch that is surrounded by microvoids is easily deformed due to plasticization.     

Properties of Starch Blends with Biodegradable Polymers

Abstract

Starch, one of the most inexpensive and most readily available of all natural polymers, can be processed into thermoplastic materials only in the presence of plasticizers and under the action of heat and shear. Poor water resistance and low strength are limiting factors for the use of materials manufactured only from starch, and hence the modification of starch is often achieved by blending aliphatic polyesters. In this review, the literatures concerning the properties of various blends of starch and aliphatic polyesters have been summarized. The biodegradable rates of blends can be controlled to a certain extent depending on the constitutions of blends, and the mechanical properties of blends are close to those of traditional plastics such as polyethylene and polystyrene. The reduction of their sensitivity to humidity makes these materials suitable for the production of biodegradable films, injection-molded items, and foams.     

Plant-Based Synthesis of Gold Nanoparticles and Theranostic Applications: A Review

Bionanotechnology is a branch of science that has revolutionized modern science and technology. Nanomaterials, especially noble metals, have attracted researchers due to their size and application in different branches of sciences that benefit humanity. Metal nanoparticles can be synthesized using green methods, which are good for the environment, economically viable, and facilitate synthesis. Due to their size and form, gold nanoparticles have become significant. Plant materials are of particular interest in the synthesis and manufacture of theranostic gold nanoparticles (NPs), which have been generated using various materials. On the other hand, chemically produced nanoparticles have several drawbacks in terms of cost, toxicity, and effectiveness. A plant-mediated integration of metallic nanoparticles has been developed in the field of nanotechnology to overcome the drawbacks of traditional synthesis, such as physical and synthetic strategies. Nanomaterials′ tunable features make them sophisticated tools in the biomedical platform, especially for developing new diagnostics and therapeutics for malignancy, neurodegenerative, and other chronic disorders. Therefore, this review outlines the theranostic approach, the different plant materials utilized in theranostic applications, and future directions based on current breakthroughs in these fields.     

Preparation,characterization and performances of biodegradable thermoplastic starch

A biodegradable thermoplastic starch (TPS) was successfully prepared from plasticizer ethanolamine and native cornstarch. The hydrogen bonding interaction between starch and ethanolamine was investigated using Fourier transform infrared (FT‐IR). When the ethanolamine mass content was 30%, after the ethanolamine‐plasticized thermoplastic starch (ETPS) was stored at RH 50% for 14 days, the mechanical testing showed that the maximum tensile stress of the ETPS reached 5.98 MPa, the tensile strain reached 106.52%, Young's modulus increased from 38.14 MPa of glycerol‐plasticized thermoplastic starch (GTPS) to 75.32 MPa of ETPS, and the breaking energy increased from 1.921 N·m to 2.305 N·m, which indicated that the mechanical properties of ETPS evidently excelled those of the GTPS. The effects of water contents on the mechanical properties of ETPS and GTPS were studied. A differential scanning calorimetry (DSC) analysis revealed that the low‐temperature transition and the glass transition temperature (T_g) of the ETPS were ?58 and 22°C respectively, which were lower than that of the GTPS. The ETPS effectively restrained the re‐crystallization of traditional GTPS, which was proved by the X‐ray diffraction (XRD). The scanning electron microscopy (SEM) images presented that ethanolamine made starch uniform. Copyright © 2007 John Wiley & Sons, Ltd.     

改性淀粉材料生物降解性分析体系的建立及应用

测定了热塑性淀粉(TPS)和热塑性双醛淀粉(TPDAS)在堆肥条件下的生物降解能力。根据ISO 14855建立了一套新的测试体系并且验证了这个体系测定高分子材料生物降解性能的可行性。对热塑性淀粉材料生物降解性的测试结果发现化学改性对于淀粉的降解速率和降解速度都有很大的影响。在可控堆肥条件下TPS比TPDAS降解的要快。TPDAS的降解速度和最终的生物降解百分率和双醛淀粉(DAS)的氧化度有密切的关系。文中讨论了存在这种关系的可能原因。有不同降解速率的TPS和TPDAS的降解过程呈现出三个阶段,即迟滞阶段。降解阶段和平稳阶段。     

Hydrostatic pressure–dependent wear behavior of thermoplastic polymers in deep sea

It is generally acknowledged that wear behavior of approved water‐lubricated thermoplastic polymers are not susceptible to hydrostatic pressure in seawater environment. However, in our recent study reported in this letter, it has been shown that the wear behavior of thermoplastic polymers sliding in seawater is strongly dependent on the hydrostatic pressure. The correlation between hydrostatic pressure and wear rates of thermoplastic polymers can be expressed in an identical form of exponential function, which has been found to be susceptible to some factors, such as polymer property, seawater absorption, filler type, sliding condition, and counterpart material. Moreover, in this letter, a primary model has been proposed to illuminate the effect of hydrostatic pressure on the wear behavior of thermoplastic polymers sliding in deep sea.     

甲酰胺塑化热塑性淀粉的性能研究

用甲酰胺作为塑化剂制备了热塑性淀粉 (TPS) ,扫描电镜显示甲酰胺可以使淀粉塑化 ,形成均一的连续相 ;流变性能说明在加工温度范围内 ,甲酰胺塑化淀粉 (FPTPS)的剪切应力对温度变化敏感性要小于甘油塑化淀粉 (GPTPS) ;用热重和DSC研究了热稳定性和玻璃化转变 ;FPTPS在 13%～ 2 3%的水含量时有较好的力学性能 ,水含量为 13%时 ,FPTPS有最大的断裂强度 3 9MPa ;水含量为 17%时 ,FPTPS最大的伸长率为 95 % ;与GPTPS相比 ,在RH(Relativehumidity) =0 5 0 %and 10 0 %环境下 ,FPTPS有良好的耐回生性能 ,这主要是因为甲酰胺可以和淀粉羟基形成更稳定的氢键