Effect of starch ratio and compatibilization on the viscoelastic behavior of POE/starch blends

In this research, polyolefin elastomers (POE)/starch blends were prepared using an internal mixer with 0 to 55 wt% starch content, and MAH was added into POE/starch blend to prepare a composite that improves its biodegradation, while tuning the viscoelastic behavior and morphology. The effect of the composition and the compatibilizer addition on properties, such as morphology, rheology, and the creep behavior, was investigated. The observations of microstructures through thescanning electron microscope (SEM) showed that in the incompatibilized blends, the interfacial adhesion of the phases was very weak. In contrast, in compatibilized samples, the broken surface of starch was observed confirming the enhanced interfacial tension. Additionally, the increase in the starch content led to the rise in the relaxation times. The creep test results revealed that with the increment of starch content, the creep of the blends increased. The compatibilizer improved the creep recovery of the blends. Moreover, by addition of the compatibilizer, the values of the creep parameters including η, E₁, E_2, and τ_R obtained from the standard linear solid model (SLS), was higher than those for the incompatibilized blends. The addition of POE-MA compatibilizer can improve the properties of POE/starch blends, while keeping their biocompatibility. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48877.     

Physicomechanical and hydrophobic properties of starch foams extruded with different biodegradable polymers

Blends of hydroxypropylated high amylose starch and various functional aids listed below were extruded into foams using a twin‐screw extruder ZSK ‐ 30. In this study, the hydrophobic character and mechanical properties of starch foams were improved by using other biodegradable polymers, such as poly‐caprolactone (PCL), poly (butylene adipate‐co‐terephthalate) (PBAT), cellulose acetate (CA), methylated pectin (MP), and polyvinyl alcohol (PVA), and crosslinkers like glyoxal. The hydrophobic character was improved in terms of a reduction in steady state weight gain, and an increase in dimensional stability (reduction in loss of radial and longitudinal dimensions) on moisture sorption. At the same time, efforts were made to maximize the expansion ratios by reduction of unit densities. Formulations of these foams (in terms of additive content and other processing parameters) were optimized. Particular formulations with PVA, polyesters like PCL and PBAT, and glyoxal with PVA gave foams with unit densities lower than 25 kg/m³. The dimensional stability increased with an increase in the polyester content, but the density increased beyond an optimum polyester content, too. The loss in radial and longitudinal dimensions under steady state conditions was 12–20% with polyesters as compared to about 50–55% for control starch. Addition of these processing aids did decrease the water sensitivity of the starch foams. Foams with CA and methylated pectin, in the presence/absence of glyoxal, had marginally lower unit densities and slightly higher expansion ratios, as compared to those of control starch. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 58–68, 2006     

Biodegradable blends of poly(butylene adipate-co-terephthalate) and polyglycolic acid with enhanced mechanical,rheological and barrier performances

Blends of poly(butylene adipate-co-terephthalate)/polyglycolic acid (PBAT/PGA) were prepared by melt blending, in which PGA was used as reinforcing component. Impacts of PGA content on tensile property, microstructure, crystallization property, melt viscosity, barrier performance of the blends were researched. Compared with very soft behavior of PBAT, the tensile yield strength and modulus of PBAT/PGA (65/35) sample increased from 7.67, 62.6 MPa of neat PBAT to 12.05, 158.9 MPa, respectively. However, owing to poor PBAT/PGA interface compatibility, its elongation at break decreased significantly from 1082.1% to 88.7%. An epoxy chain extender (ADR) was used as reactive modifier to improve its interface compatibility and rheological property. The related physical properties of PBAT/PGA/ADR (65/35/x) samples with various ADR contents were evaluated in detail. It was found that ADR exerted relatively complex influences on the properties. Overall, compared with neat PBAT and PBAT/PGA (65/35) sample, the PBAT/PGA/ADR (65/35/x) samples exhibited better stiffness-ductility balance and higher processing stability.     

Effect of compatibilizer concentration on dynamic rheological behavior and morphology of thermoplastic starch/polypropylene blends

The reactive compatibilization of blends consisting polypropylene (PP) and thermoplastic starch (TPS) (70/30) with different portions of PP-grafted maleic anhydride (PP-g-MA) is carried out by melt mixing. The esterification reaction between the starch hydroxyl and the PP-g-MA groups proved by the FTIR leads to a compatibility improvement. The dynamic rheological properties, morphology, elongation at break, and the impact strength of the blends were studied. The SEM images show that increasing the compatibilizer concentration reduces the dispersed TPS droplet size. The generalized Zener model states that an elastic interface is established (minimum α value) and enables us to predict the dynamic rheological properties of our blends in a longer frequency range to where the current experimental limitation exists. The modified Cross model is implemented to confirm better adhesion between phases when 20 wt % PP-g-MA is used (minimum a_c value). The increase in the dynamic viscoelastic moduli at concentrations up to 20 wt % and the observed plateau at the elongation at break point at this concentration confirmed that this concentration is the optimum for the maximum stress transfer. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48742.     

生物可降解热塑性淀粉的开发

简要地介绍了热塑性淀粉（ＴＳ）的研究动态，重点介绍热塑性淀粉的加工原理，加工设备，热塑性淀粉的结构和性能，讨论热塑性淀粉的品种和其相应的应用领域，热塑性淀粉开发中存在的问题和应用前景。     

Processing aids for biodegradable polymers

The melt fracture behavior of several commercial polylactides (PLAs) and poly(ε‐caprolactone) (PCL) is investigated. PLAs and PCL with molecular weights greater than a certain value were found to exhibit melt fracture phenomena in capillary extrusion, which manifests itself as distortions on their surface once the extrusion rate exceeds a critical value. It was found that the addition of a small amount of PCL (typically 0.5 wt %) into the PLA and vice versa is effective in eliminating and delaying the onset of melt fracture to higher shear rates in the capillary extrusion of PLA and PCL, respectively. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Engineering extruded collagen fibers for biomedical applications

Extruded collagen fibers constitute a promising biomimetic scaffold for tissue engineering applications. In this study, we compared the structural, thermal, and mechanical properties of fibers produced from either NaCl or poly(ethylene glycol) with a number-average molecular weight of 8000 (PEG 8K), the only two coagents that have been used in the fabrication process. As novel, we report the fabrication of fibers with properties similar to native or synthetic fibers using other coagents. NaCl derived fibers were characterized by higher thermal stability (p < 0.026), stress (p < 0.001), and modulus (p < 0.0025) values than PEG 8K, whereas the latter yielded more extendable fibers (p < 0.012). Poly(ethylene glycol)s with number-average molecular weights of 200 and 1000 produced fibers with similar mechanical properties (p > 0.05) that were thinner (p < 0.033), stiffer (p < 0.022), and less extendable (p < 0.0002) than those of PEG 8K. Poly(vinyl alcohol) (PVA) with a number-average average molecular weight of 9–10,000 and PEG 8K yielded fibers with similar diameters and stress-at-break values (p > 0.05); however, the poly(ethylene glycol) derived fibers were more extendable (p < 0.0003), whereas the PVA fibers were stiffer (p < 0.029). Gum-arabic- and soluble-starch-derived fibers were of similar tensile strength, extendibility, and stiffness (p > 0.05). In this in vitro study, the thickest (p < 0.011) and the weakest (p < 0.0066) fibers were produced in the presence of sodium sulfate. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Biodegradable blends based on polyvinyl pyrrolidone for insulation purposes

Polyvinyl pyrrolidone/polyvinyl alcohol (PVP/PVA) and polyvinyl pyrrolidone/starch (PVP/St) blends were prepared with different compositions. The compatibility studies indicate that PVP/PVA is compatible while PVP/St is incompatible. The addition of glycerol and glutaraldehyde can improve to some extent the phase separation behavior between PVP and St. The permittivity ε′ and the dielectric loss ε″ were measured in the frequency range 0.01 Hz up to 10 MHz and temperatures from 30 up to 90°C. It is found that the blend ratio (50/50) of both investigated systems is preferable for insulation purposes in comparable with the other blends under investigation. The data of the loss electric modulus M″ was calculated from the dielectric parameters ε′ and ε″and analyzed into three relaxation mechanisms ascribing the cooperative motion of the main and side chains τ₁ (αβ), the side chain motion τ₂ (β) and the segmental motion of the groups attached to the side chains τ₃ (βγ). The activation energy corresponds to the second relaxation process ΔH₂ was calculated using Arrhenius equation and found to be in the range which justifies the presumption of β‐relaxation process. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Preparation and properties of biodegradable poly(butylene succinate)/starch blends

The vital differences between the use of untreated starch and gelatinized starch in blends with poly(butylene succinate) (Bionolle) were thoroughly examined in this study. The melting temperature decreased slightly with increasing dosages of untreated and gelatinized starch. The added starch perhaps tended to disrupt the intermolecular hydrogen bonding within the Bionolle matrix. On the other hand, a large increase in the crystallinity was seen with the addition of starch. Starch appeared to play a nucleating role in the blends. The trend of the glass‐transition temperature decreasing with the starch level was similar to the trend of the melting temperature. For the same starch content, the glass‐transition temperature showed some variations. For blends containing a certain amount of gelatinized starch, the thermal stability remained to a certain degree but continued to decrease. This was ascribed to the relatively low heat stability of starch. As for the mechanical properties, a significant increase in the tensile strength (up to 2 times) was observed when untreated starch was replaced with gelatinized starch in the blends. Similarly, the tear strength increased up to 1.5 times if gelatinized starch was employed. Apparently, the gelatinization of starch was efficiently achieved for promoting its compatibility with Bionolle. In all cases, the mechanical properties of Bionolle blended with gelatinized starch were better than those of Bionolle blended with untreated starch. A morphological investigation provided evidence in support of these findings. This relatively low‐cost gelatinization approach provides an alternative to a high‐cost compatibilizer approach for improving the performance of biodegradable blends. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 257–264, 2005     

Solvent-Cast 3D Printing of Biodegradable Polymer Scaffolds

3D printing is a popular fabrication technique because of its ability to produce complex architectures. Melt-based 3D printing is widely used for thermoplastic polymers like poly(caprolactone) (PCL), poly(lactic acid) (PLA), and poly(lactic-co-glycolic acid) (PLGA) because of their low processing temperatures. However, traditional melt-based techniques require processing temperatures and pressures high enough to achieve continuous flow, limiting the type of polymer that can be printed. Solvent-cast printing (SCP) offers an alternative approach to print a wider range of polymers. Polymers are dissolved in a volatile solvent that evaporates during deposition to produce a solid polymer filament. SCP, therefore, requires optimizing polymer concentration in the ink, print pressure, and print speed to achieve desired print fidelity. Here, capillary flow analysis shows how print pressure affects the process-apparent viscosity of PCL, PLA, and PLGA inks. Ink viscosity is also measured using rheology, which is used to link a specific ink viscosity to a predicted set of print pressure and print speed for all three polymers. These results demonstrate how this approach can be used to accelerate optimization by significantly reducing the number of parameter combinations. This strategy can be applied to other polymers to expand the library of polymers printable with SCP.     

Biodegradable starch particles for controlled release applications: Swelling and leaching mechanisms

Starch-extruded particles have only found infrequent use as delivery systems for active ingredients. We have previously shown that these particles are attractive for releasing hydrophobic compounds in water media. Here, we cover a range of amylose–amylopectin ratios and evaluate the presence of the thyme essential oil (TEO) as active compound to understand the dominant release mechanism in relation to the physicochemical properties of the starch matrices. Starch blends with high amylopectin content (1.8 and 15% amylose) could not be shaped into regular particles. For amylose contents higher than 28%, the equilibrium degree of swelling in water decreased with increasing amylose contents, from nearly 300% for an amylose content of 28–90% at an amylose content of 70%. For both lowest amylose contents, 1.8 and 15%, leaching of solids and disintegration of the particles resulted in a low apparent degree of swelling. The presence of TEO reduces the degree of swelling of the gelatinized starch matrix. This is explained by the formation of thymol–amylose complexes, which is confirmed by Fourier transform infrared spectroscopy analysis and X-ray diffraction.     

可生物降解材料

叙述了可生物降解材料的分类及开发现状,综述了可生物降解材料研究的成果和进展,介绍了可生物降解材料、淀粉系列生物降解材料、二氧化碳树脂生物降解材料与医用可生物降解材料     

Reactive compatibilization of PLA/TPU blends with a diisocyanate

This study focuses on the compatibilization of poly(lactic acid) (PLA)/thermoplastic polyurethane (TPU) blends by using 1,4 phenylene diisocyanate (PDI) for the first time, as the compatibilizer. Because of the potential interactions of diisocyanates with ? OH/? COOH, they are useful for reactive processing of PLA/TPU blends in the melt processing. To have insight on the reactively compatibilized structure of PLA/TPU blends, phase morphologies are observed by means of scanning electron microscopy. The mechanical, thermal, and rheological responses of the blends are investigated. The observations are that the brittle behavior of PLA changes to ductile with the addition of TPUs. The addition of PDI improves the tensile properties of the blends. The compatibilization action of PDI is monitored with DMA and rheological experiments. Cross‐over in the G′ and G″ curves of compatibilized blends indicates the relaxation of branches formed in the presence of PDI. The dispersed phase size of TPU decreases in PLA in the presence of PDI due to the improved compatibility. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40251.     

Effect of the processing techniques on the properties of ecocomposites based on vegetable oil‐derived Mater‐Bi® and wood flour

Polymer composites based on biodegradable polymers and natural‐organic fillers are becoming more and more important because of their interesting properties in terms of environmental impact, manufacturing cost, and esthetic features. In particular, the use of biodegradable polymer matrices allows obtaining a full biodegradability. One of the most interesting biodegradable polymer families is the Mater‐Bi® one. In this work, we investigated the processability, the influence of different processing techniques, and the influence of the filler particle size on the properties of Mater‐Bi/wood flour composites. Injection molding caused a partial degradation of the macromolecular chains, whereas single‐screw extrusion followed by calendering and twin‐screw extrusion provoked an increase of the elastic modulus and of the viscosity. The use of wood flour led to a significant increase of the rigidity, whereas a reduction of the ductility was observed. Because of the very similar aspect ratios of the two different filler size classes, no dramatic differences in the properties were found. These results are useful in order predicting and setting up the optimum preparation and processing strategy for the production of fully biodegradable polymer composites. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Effects of emulsion parameters on relaxation behaviors for immiscible polymer blends

The relaxation behaviors of the binary immiscible blends reflected on the plots of the storage modulus and the imaginary part of complex viscosity were investigated using the Maxwell and the Palierne models. It was revealed that the peaks in the high‐ and low‐frequency regions on the complex viscosity imaginary part plot are owing to the relaxations of the blend and deformed dispersed droplets, respectively. Based on these two models, six emulsion parameters (interfacial tension, relaxation times and viscosities of two components, and dispersed phase volume fraction) were investigated in terms of their effects on the shape features of the plots of the imaginary part of complex viscosity and the Cole–Cole. The results showed that the viscosities of two components and dispersed phase volume fraction play key roles in the radii of the two circular arcs on the Cole–Cole plot. Furthermore, the two circular arcs are well separated in the case of lower interfacial tensions and dispersed phase viscosities, shorter matrix relaxation times, and higher matrix viscosities and dispersed phase volume fractions. The total relaxation time of the deformed dispersed droplets increases with increasing the viscosities of two components, especially with decreasing the interfacial tension. Three types of polymer blends were prepared and their dynamic frequency sweep testing results demonstrated the effectiveness of the corresponding predicted results. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 39690.     

Compatibility study in natural rubber and maize starch blends

Blends containing various ratios of natural rubber (NR) and maize starch (MS) were prepared on a two roll mill. The effect of starch contents on physico-mechanical properties and curing characteristics of the prepared blend vulcanizates was investigated. The data indicate poor mechanical properties, delayed cure rate index, and decreased maximum torque with increasing starch content in the blend formulation. This indicates that the interfacial interaction between the blend components was poor. Various contents of the compatibilizers, maleic acid anhydride (MAH) and glycidyl methacrylate (GMA), were mixed with the blend NR/MS (90/10). The effect of the compatibilizer contents on the physico-mechanical properties and curing characteristics of the binary blend was investigated. Compatibilized blends with GMA (1 phr) showed an improvement in the physico-mechanical properties in comparison with uncompatibilized blend samples. Blends with MAH exhibited higher modulus and hardness values with respect to GMA blends. The efficiency of the compatibilizers was also evaluated by studies of phase morphology (scanning electron microscope), Fourier transform infrared spectroscopy, and thermal stability (thermogravimetric analysis). © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Dynamic rheological properties of high‐density polyethylene/polystyrene blends extruded in the presence of ultrasonic oscillations

The linear rheological properties of high‐density polyethylene (HDPE), polystyrene (PS), and HDPE/PS (80/20) blends were used to characterize their structural development during extrusion in the presence of ultrasonic oscillations. The master curves of the storage shear modulus (G′) and loss shear modulus (G″) at 200°C for HDPE, PS, and HDPE/PS (80/20) blends were constructed with time–temperature superposition, and their zero shear viscosity was determined from Cole–Cole plots of the out‐of‐phase viscous component of the dynamic complex viscosity (η″) versus the dynamic shear viscosity. The experimental results showed that ultrasonic oscillations during extrusion reduced G′ and G″ as well as the zero shear viscosity of HDPE and PS because of their mechanochemical degradation in the presence of ultrasonic oscillations; this was confirmed by molecular weight measurements. Ultrasonic oscillations increased the slopes of log G′ versus log G″ for HDPE and PS in the low‐frequency terminal zone because of the increase in their molecular weight distributions. The slopes of log G′ versus log G″ for HDPE/PS (80/20) blends and an emulsion model were used to characterize the ultrasonic enhancement of the compatibility of the blends. The results showed that ultrasonic oscillations could reduce the interfacial tension and enhance the compatibility of the blends, and this was consistent with our previous work. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 3153–3158, 2004     

Biodegradable poly(ethylene succinate) blends and copolymers containing minor amounts of poly(butylene succinate)

Poly(ethylene succinate) (PES), poly(butylene succinate) (PBS), and PES‐rich copolyesters were synthesized using an effective catalyst, titanium tetraisopropoxide. PES was blended with minor amounts of PBS for the comparison. The compositions of the copolyesters and the blends were determined from NMR spectra. Their thermal properties were studied using a differential scanning calorimeter (DSC), a temperature modulated DSC (TMDSC), and a thermogravimetric analyzer. No significant difference exists among the thermal stabilities of these polyesters and blends. For the blends, the reversible curves of TMDSC showed a distinct glass‐rubber transition temperature (T_g), however, the variation of the T_g values with the blend compositions was small. Isothermal crystallization kinetics and the melting behavior after crystallization were examined using DSC. Wide‐angle X‐ray diffractograms (WAXD) were obtained for the isothermally crystallized specimens. The results of DSC and WAXD indicate that the blends have a higher degree of crystallinity and a higher melting temperature than those of the corresponding copolymers. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Rheological behavior and flow instability in capillary extrusion of ultrahigh-molecular-weight polyethylene/high-density polyethylene/nano-SiO2 blends

Rheological behaviors of ultrahigh-molecular-weight polyethylene (PE)/high-density PE/SiO₂ blends are investigated using parallel-plate rheometer and capillary rheometer. The molecular chain conformational change mechanism is used to explain flow instabilities during extrusion. The viewpoints are proposed: (1) critical shear rate depends on the relative strength of irreversible viscous loss and reversible elastic orientation for molecular chains in transverse velocity gradient field inside the die and (2) critical shear stress depends on the extent of molecular chain conformational change inside the die, and the ease of conformational recovery after leaving the die. Modified nano-SiO₂ particles are detected a certain interfacial adhesion in PE matrix. The interfacial interaction limits viscous flow inside the die and conformational recovery after leaving the die, thus causing not only the flow instabilities to occur prematurely on shear rate and delaying sharkskin on shear stress, but also an alternate “sharkskin-melt fracture” appearance after global extrusion fracture. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47713.     

Bio-based blends from poly(3-hydroxybutyrate-co-3-hydroxyvalerate) and natural rubber for packaging applications

Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) is a promising bioplastic but has limited packaging applications due to its brittleness and poor processability. Incorporation of highly viscous high-molecular-weight natural rubber (HMW-NR, gel extracted from NR) into PHBV can improve these properties. HMW-NR is not commercially available, impeding commercialization of the PHBV/rubber blends. Therefore, an organic peroxide was used to selectively crosslink NR to increase its viscosity during its melt blending with PHBV. The PHBV/NR blends were fabricated through a two-step extrusion process using a twin-screw extruder. The blends contained two phases with crosslinked rubber being dispersed in PHBV, and had clear rubber loading-dependent differences in performance. The thermal stability and melt strength of the blends were enhanced over pristine PHBV, indicating improved processability. The flexibility and toughness of the blends were improved by 59 and 20%, respectively, compared with pristine PHBV, and were comparable to commercial petroleum-based plastics. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47334.