Rheology and sheet extrusion of Novatein thermoplastic protein/polybutylene adipate-co-terephthalate blends

Novatein is a thermoplastic polymer made from blood meal proteins, but it has rheological properties very different from commodity thermoplastics. Capillary rheometry revealed an apparent time dependent shear viscosity for Novatein, evident from a decreasing pressure drop over time, measured at constant shear rate. However, blending with polybutylene adipate-co-terephthalate (PBAT) reduced the time dependence for uncompatibilized blends and virtually eliminated time dependence for compatibilized blends containing 30 wt % PBAT. Novatein's extensional viscosity is three orders of magnitude more than its shear viscosity and explained the difficulty in sheet extrusion. In contrast, 30% compatibilized blends had an extensional viscosity similar to neat PBAT and was also the only blend that could be successfully sheet extruded. Although uncompatibilized blends at the same or lower PBAT content also had a lower extensional viscosity, they could not be sheet extruded and the difference was the 30% compatibilized blends had a fine PBAT phase structure (co-continuous in this case), which was sufficiently adhered to the Novatein phase. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47977.     

In situ compatibilization of polylactide/thermoplastic polyester elastomer blends using a multifunctional epoxide compound as a processing agent

In situ compatibilized poly(lactic acid)/thermoplastic polyester elastomer (PLA/TPEE) (80/20) blends are prepared by using multifunctional epoxide oligomer (coded as ADR) as a reactive modifier. Experiments such as torque, melt mass flow rate (MFR), SEM, DSC and tensile test were conducted to characterize properties of the PLA/TPEE/ADR blends. In situ reactions between PLA, TPEE and ADR were researched using a lab torque rheometer. It was proposed that ADR may initiate a variety of chain extension/branching reactions between PLA and TPEE under mixing process. In particular, the formed copolymer PLA‐ADR‐TPEE could be viewed as an in situ compatibilizer to improve the compatibility of PLA and TPEE. As expected, the value of MFR decreased greatly with increasing the ADR addition. The morphology reveals that interface adhesion of PLA/TPEE blend was enhanced with the incorporation of ADR, which led to a reduction in TPEE domain size. Moreover, tensile ductility of PLA/TPEE (80/20) blend was improved greatly by addition of the reactive modifier, e.g. the elongation at break was increased from 53% to the maximum value of 213% with addition of 1.2 phr ADR. The toughening effect can be explained by crazing with shear yielding mechanism. Attempts were made to produce ductile films from these PLA/TPEE/ADR blends by using extrusion blowing method. Effect of ADR on blowing stability and tensile property of these blends was investigated. Improvement on blowing stability and tensile ductility of PLA/TPEE/ADR films also shows that ADR is an efficiently reactive compatibilizer, as well as a viscosity enhancer for PLA/TPEE blends. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43424.     

Encapsulation of Rhodopseudomonas palustris KTSSR54 using beads from alginate/starch blends

Alginate beads are a promising carrier for biofertilizer delivery, but still possess drawbacks of low mechanical strength and bead shrinkage that result in poor appearance and inadequate cell protection. Blending alginate with starch was proposed as a solution to these problems, and here alginate hydrogels were prepared using a 2% (w/v) alginate dispersion blended with varying contents of gelatinized starch (0–5% w/v). The interaction produced a viscosity synergism that increased the complexity of the matrix network in the alginate/starch blends, producing a more suitable matrix for cell entrapment. Hydrogen bonding between alginate and starch influenced the viscosity of the various solutions in a way that was consistent with the FTIR spectra. The starch content also helped beads retain their spherical shape after drying. The starch supported the entrapment of bacterial cells (plant growth-promoting bacterium Rhodopseudomonas palustris KTSSR54 as biofertilizer) in the matrix, which reduced cell loss. The highest entrapment efficiency of 70.83% was obtained at 4% (w/v) starch, while the entrapment efficiency of control beads was 50.56%. Overall, the appropriate content of starch mixed with alginate is conducive to changes in the morphology of microcapsules and increases in the amount of biological encapsulation.     

Investigation of structure and mechanical properties of toughened poly(l‐lactide)/thermoplastic poly(ester urethane) blends

In this study, poly(l ‐lactide) (PLA) is melt‐blended with thermoplastic polyurethane (TPU) to modify the brittleness of PLA. An aliphatic ester‐based TPU was selected in order to have an ester sensitivity for degradation and an inherent biocompatibility. Using this compatible TPU, there was no need to apply problematic compatibilizers, so the main positive properties of PLA such as biocompatibility and degradability were not challenged. The detected microstructure of PLA/TPU blends showed that when the TPU content was lower than 25 wt %, the structure appeared as sea‐islands, but when the TPU content was increased, the morphology was converted to a cocontinuous microstructure. A higher interfacial surface area in the blend with 25 wt % TPU (PLA25) resulted in a higher toughness and abrasion resistance. The various analyses confirmed interactions and successful coupling of two phases and confirmed that melt‐blending of PLA with the aliphatic ester‐based TPU is a convenient, cost‐effective, and efficient method to conquer the brittleness of PLA. The prepared blends are general‐purpose plastics, but PLA25 showed an optimum mechanical strength, toughness, and biocompatibility suitable for a wide range of applications. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43104.     

Rheological behavior and morphology of poly(lactic acid)/low-density polyethylene blends based on virgin and recycled polymers: Compatibilization with natural surfactants

Blends based on poly(lactic acid) and low-density polyethylene were compatibilized exploiting an innovative strategy involving the introduction of different mixtures of two sustainable liquid surfactants characterized by dissimilar hydrophilic–lipophilic ratios. The compatibilization method was first applied on blends made of virgin polymers, aiming at assessing the surfactant mixture inducing a more significant morphology refinement. Besides, to verify the effectiveness of the selected compatibilizers on recycled materials, the same process was carried out on blends based on reprocessed polymers. Interestingly, the compatibilization caused a significant microstructure modification, with a decrease of 54% of the mean size of the dispersed particles, in the case of virgin polymers-based blends, with a consequent increase of 19% of the dynamic elastic modulus. On the other hand, in the case of reprocessed polymers-based blends, a different compatibilizer efficiency was observed, as the noncompatibilized blend showed amore regular microstructure compared to the compatibilized counterpart.     

Compatibilization effects in thermoplastic protein/polyester blends

Novatein thermoplastic protein was extrusion blended with poly(butylene adipate‐co‐terephthalate) (PBAT) in the presence of dual compatibilizers to produce blends with greater energy absorbing properties than pure Novatein. Compatibilizer pairs were Joncryl ADR‐4368 (glycidyl methacrylate‐functionalized) with 2‐methylimidazole (2MI), and poly‐2‐ethyl‐2‐oxazoline (PEOX) with polymeric diphenyl methane diisocyanate (pMDI). Uncompatibilized Novatein/PBAT blends had decreased tensile mechanical properties, attributed to phase separation, and poor interfacial adhesion. PBAT became finely dispersed in both compatibilized systems, but PEOX/pMDI blends showed embrittlement and large Novatein domains, which acted as stress concentrations. Tensile strength and elongation at break for Joncryl/2MI blends did not decrease compared with Novatein, even at 10 wt % PBAT, and impact strength increased threefold. Dynamic mechanical analysis and solvent extraction showed that PBAT coalesced in all systems, at compositions as low as 2 wt %. It was concluded that using Joncryl/2MI as a dual compatibilizer system can successfully produce a morphology that enhances energy absorption during fracture. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45808.     

Study of the effect of processing conditions on the co‐injection of PBS/PBAT and PTT/PBT blends for parts with increased bio‐content

This work studies the effect of processing parameters on mechanical properties and material distribution of co‐injected polymer blends within a complex mold shape. A partially bio‐sourced blend of poly(butylene terephthalate) and poly(trimethylene terephthalate) PTT/PBT was used for the core, with a tough biodegradable blend of poly (butylene succinate) and poly (butylene adipate‐co‐terephthalate) PBS/PBAT for the skin. A ½ factorial design of experiments is used to identify significant processing parameters from skin and core melt temperatures, injection speed and pressure, and mold temperature. Interactions between the processing effects are considered, and the resulting statistical data produced accurate linear models indicating that the co‐injection of the two blends can be controlled. Impact strength of the normally brittle PTT/PBT blend is shown to increase significantly with co‐injection and variations in core to skin volume ratios to have a determining role in the overall impact strength. Scanning electron microscope images were taken of co‐injected tensile samples with the PBS/PBAT skin dissolved displaying variations of mechanical interlocking occurring between the two blends. © 2014 The Authors Journal of Applied Polymer Science Published by Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41278.     

Biopolymer foams from Novatein thermoplastic protein and poly(lactic acid)

A batch processing method is used to fabricate foams comprising of a blend of poly(lactic acid) (PLA) and Novatein, a protein‐based thermoplastic. Various compositions of Novatein/PLA are prepared with and without a compatibilizer, PLA grafted with itaconic anhydride (PLA‐g‐IA). Pure Novatein cannot form a cellular structure at a foaming temperature of 80 °C, however, in a blend with 50 wt % of PLA, microcells form with smaller cell sizes (3.36 µm) and higher cell density (8.44 × 10²¹ cells cm^?3) compared to pure PLA and blends with higher amounts of PLA. The incorporation of 50 wt % of semicrystalline Novatein stiffens the amorphous PLA phase, which restrains cell coalescence and cell collapse in the blends. At a foaming temperature of 140 °C, NTP₃₀–PLA₇₀ shows a unique interconnected porous morphology which can be attributed to the CO₂‐induced plasticization effect. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134 , 45561.     

Super-tough poly(lactic acid) using a fully bio-based polyester containing malic acid via in-situ interfacial compatibilization

Reactive interfacial compatibilization is the most efficient way to prepare super-tough poly (lactic acid) (PLA) materials. Introducing a post-reactive group into a toughening agent that can react with PLA is the key issue. Herein, we reported a series of fully bio-based polyesters (PBSePM) synthesized with sebacic acid, diethyl malate, 1,3-propanediol, and 1,4-butanediol via transesterification in one pot. Super-tough PLA materials can be obtained by reactively blending with PBSePM in the presence of hexamethylene diisocyanate (HDI). In the processing, the side hydroxyl group of the PBSePM reacted with HDI and formed polyurethane elastomer to improve the toughness of PLA. Moreover, the in-situ formed PLA-g-PBSePM grafted copolymer enhanced the interfacial adhesion. With increasing diethyl malate moiety in PBSePM, the PBSePM phase morphology transformed from co-continuous phase structure to semi-continuous and “sea-island” phase structure. When adding 20 wt% PBSePM, all PLA/PBSePM blends have a notched impact strength higher than 53 kJ m⁻², suggested a super toughness effect. Maximum impact strength of 83 kJ m⁻² was realized while the PBSePM containing 20% diethyl malate moiety. In addition, super-tough PLA materials can be achieved by only adding 15 wt% PBSePM20, exhibited a highly efficient toughening effect.     

Mechanical,thermal, and barrier properties of nanocomposites based on poly(butylene succinate)/thermoplastic starch blends containing different types of clay

Nanocomposites based on blends of poly(butylene succinate) (PBS) and thermoplastic cassava starch (TPS) were prepared using a two‐roll mill and compression molding, respectively. Two different types of clay, namely sodium montmorillonite (CloisiteNa) and the organo‐modified MMT (Cloisite30B) were used. The morphological and mechanical properties of the nanocomposite materials were determined by using XRD technique and a tensile test, respectively. Thermal properties of the composite were also examined by dynamic mechanical thermal analysis and thermal gravimetric techniques. Barrier properties of the nanocomposites were determined using oxygen transmission rate (OTR) and water vapor transmission rate (WVTR) tests. From the results, it was found that by adding 5 pph of the clay, the tensile modulus and the thermal properties of the blend containing high TPS (75 wt %) changed significantly. The effects were also dependent on the type of clay used. The use of Cloisite30B led to a nanocomposite with a higher tensile modulus value, whereas the use of CloisiteNa slightly enhanced the thermal stability of the material. OTR and WVTR values of the blend composites containing high PBS ratio (75 wt %) also decreased when compared to those of the neat PBS/TPS blend. XRD patterns of the nanocomposites suggested some intercalation and exfoliation of the clays in the polymer matrix. The above effects are discussed in the light of different interaction between clays and the polymers. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 1114‐1123, 2013     

Compatibility improvement of poly(lactic acid)/thermoplastic polyurethane blends with 3‐aminopropyl triethoxysilane

Poly(lactic acid) (PLA)/thermoplastic polyurethane (TPU) blends were prepared via a melt‐blending process with or without the addition of a 3‐aminopropyl triethoxysilane (APTES) compatibilizer at different dosages. The addition of the compatibilizer showed improved compatibility between TPU and PLA; this led to an enhanced dispersion of TPU within the PLA matrix. With the addition of 1‐phr APTES, the crystallization behavior did not vary much, but this exacerbated the formation of a second melting temperature for PLA at higher temperature. However, the addition of 5‐phr APTES into the PLA/TPU blends depressed the crystallization temperature and resulted in a melting temperature depression phenomena with the disappearance of the second melting peak because of the lubricated effect of low‐molecular‐weight species of APTES. The addition of a low dosage of APTES improved the impact strength further from 29.2 ± 1.4 to 40.7 ± 2.7 J/m but with a limited improvement in the tensile properties; this indicated that a higher dispersion of the dispersed phase did not always improve all of the mechanical properties because of the low‐molecular‐weight nature of the compatibilizer used. The physical properties of the added modifier needed to be considered as well. A low dosage of APTES (1 phr) also increased the viscosity because of the improved interaction between TPU and PLA at all of the investigated shear rate regions, but a higher dosage of compatibilizer induced another plasticizing effect to reduce the viscosity. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42322.     

Functionalized liquid natural rubber and liquid epoxidized natural rubber: A promising green toughening agent for polyester

Toughened unsaturated polyester resins (UPRs) were prepared using two different reactive rubbers, namely, liquid natural rubber (LNR) and liquid epoxidized natural rubber (LENR). The effect of varying amounts of LNR and LENR on the morphology, thermal, and mechanical properties of UPR were evaluated. Fourier Transform Infrared spectroscopy was used to investigate the probable crosslinking reaction and changes in the functional groups on crosslinking. Field emission scanning electron microscopy and infinite focus microscopy were used to study the morphology of fracture surfaces. Tensile test showed that both the rubber‐modified resins (1.5 wt %) improved tensile strength. The viscoelastic properties and thermal stability of the toughened polyesters were evaluated using dynamic mechanical thermal analysis and thermogravimetric analysis, respectively. A slight reduction in the glass transition temperature (T_g) of the polyester was reported on the addition of both the rubbers. An increment in impact strength and fracture toughness was observed at 1.5 wt % for LNR and 4.5 wt % for LENR‐modified UPR. The results showed that both the liquid rubbers improved the mechanical properties of UPR. However, LENR‐modified UPR exhibited a more significant improvement in the mechanical properties compared to LNR‐modified UPR. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41292.     

Morphology,rheology, crystallization behavior,and mechanical properties of poly(lactic acid)/poly(butylene succinate)/dicumyl peroxide reactive blends

The reactive blends were prepared by the blending of poly(lactic acid) (PLA) with poly(butylene succinate) (PBS) in the presence of dicumyl peroxide (DCP) as a radical initiator in the melt state. The gel fractions, morphologies, crystallization behaviors, and rheological and mechanical properties of the reactive blends were investigated. Some crosslinked/branched structures were formed according to the rheological measurement and gel fraction results, and the crosslinked/branched structures played the role of nucleation site for the reactive blends. The PLA–PBS copolymers of the reactive blends acted as a compatibilizer for the PLA and PBS phases and, hence, improved the compatibility between the two components. Moreover, it was found that the reactive blends showed the most excellent mechanical properties as the DCP contents were 0.2 and 0.3 phr. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 39580.     

Evaluation of interactions of biopolymers using dynamic rheological measurements: Effect of temperature and blend ratios

Herein, a robust scheme is defined to elaborate interaction behavior of biopolymers and the effect of temperature on it using dynamic rheological measurements. As a case study, sage seed gum‐xanthan gum (SSG‐XG) interaction at different ratios (1‐0, 3‐1, 1‐1, 1‐3, 0‐1) and temperatures (10, 30, 50, 70, and 90 °C) were experimentally evaluated. SSG‐XG of 3‐1 showed the highest temperature tolerance of almost all rheological parameters and relaxation time in amplitude sweep and frequency sweep measurements, respectively. Higher elastic component and higher extent of temperature dependency of this parameter were observed with increasing SSG fraction. At high temperature, XG molecules in aqueous solution illustrated an ordered (helix) –disordered (coil) conformational transformation while SSG exhibited more rigidity at higher temperature. Only 3‐1 and 1‐1 SSG‐XG at 50 °C showed synergistic interaction of A_a (stiffness parameter) among all blends, which suggested the use of 3‐1 SSG‐XG blend in systems where enhanced structure at high temperature is desirable. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44414.     

Hydrolytic stability of polylactide and poly(methyl methacrylate) blends

The hydrolytic stability of polylactide/poly(methyl methacrylate) (PLA/PMMA) blends prepared using a twin‐screw extrusion process was investigated. The effects of hydrolysis were monitored in neutral and alkaline media at 80 °C by tracking the changes in molecular weight distribution, weight loss, water uptake, and crystallization behavior. The crystallinity of PLA in blends prior to hydrolysis was shown to be largely hindered by the presence of PMMA. However, PLA recrystallized rapidly during hydrolysis. The PMMA in the blends was shown to provide increased hydrolytic and structural stability to the blends. In the neutral medium, the presence of PMMA delayed and reduced the weight loss but did not significantly affect PLA degradation kinetics. On the other hand, in the alkaline medium, the weight loss rate was strongly decreased in presence of PMMA and the kinetics of degradation was shown to be depend on PMMA content. The microstructure of these blends throughout the hydrolysis process was also examined by scanning electron microscopy. A porous structure, with interconnected pores in the 20–50 nm range, was developed due to the selective removal of PLA. Based on these morphological observations, erosion mechanism of PLA/PMMA blends was discussed. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45991.     

Design of highly tough poly(l‐lactide)‐based ternary blends for automotive applications

Technical renewable poly(l ‐lactide) (PLA)‐based blends represent an elegant way to achieve attractive properties for engineering applications. Recently, the miscibility between PLA and poly(methyl methacrylate) (PMMA) gave rise to new formulations with enhanced thermo‐mechanical properties but their high brittleness still remains a challenge to be overcome. This work here focuses on rubber‐toughened PLA/PMMA formulations for injection‐molding processes upon the addition of a commercially available ethylene‐acrylate impact modifier (BS). The miscibility between PLA and PMMA is not altered by the presence of BS but the incorporation of BS (17% by weight) into a PLA/PMMA matrix could enhance both ductility and toughness of PLA/PMMA blends for PMMA content up to 50 wt %. An optimum range of particle sizes (d_n ～0.5 µm) of the dispersed domains for high impact toughness is identified. These bio‐based ternary blends appear as promising alternatives to petro‐sourced blends such as ABS‐based blends in engineering injection‐molding parts. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43402.     

Shear and extensional viscosity of thermally aggregated thermoplastic protein

Novatein is a thermoplastic produced from blood meal and is used in different agricultural applications. Novatein has some unique processing challenges and its rheology was studied using screw-driven capillary rheometry, with a particular focus on sheet extrusion using ethylene glycol, glycerol, propylene glycol (PG), or triethylene glycol (TEG) as plasticizers. The entrance pressure drop contributed up to 44% of the total pressure drop (entrance and capillary pressure drop), but this was significantly reduced by plasticization or increased temperature. Polyol addition led to higher shear viscosities in comparison to no polyol plasticization, most likely due to improved chain mobility resulting in orientation effects. Elongational flow was dominated by primary plasticization of the protein-rich phase and changes in secondary structure, whereas secondary plasticization (phase separation into a polyol-rich phase) played a significant role in the reduction of the shear viscosity. Of the selected plasticizers, PG showed the most efficient plasticization in both shear and elongational flow. When combined with the beneficial secondary structural changes brought about by TEG, the sheet forming ability of Novatein was drastically improved.     

Natural weathering studies of biobased thermoplastic starch from agricultural waste/polypropylene blends

Thermoplastic starch (TPS) obtained from agricultural waste was blended with polypropylene (PP) for natural weathering studies. The agricultural waste material was obtained from seeds and tubers with a starch content of approximately 50%. Commercial‐grade TPS and native tapioca‐based TPS were also prepared for comparison. The biobased TPS/PP extruded sheets were exposed to natural weathering for six months and their deterioration in weight, tensile properties, thermal properties, and relative molecular weight were monitored. SEM micrographs revealed the formation of surface cracking and the presence of microorganisms. FTIR spectrum indicated an increase in the carbonyl index over time as a result of the formation of degradation products. TPS/PP blends made from agricultural waste showed a better resistance to natural weathering compared to the other high starch formulation. The higher starch content in the blend system encouraged the rapid degradation process due to the combined effect of UV radiation with oxidation, moisture, temperature, and microbial attack. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

PBAT/TPS-nanowhiskers blends preparation and application as food packaging

About 85–90% of the market for new materials in biodegradable packaging is served by various blends and composites containing starch in some portion. In an attempt to satisfy the increasing consumer demand, innovative materials are being developed. This includes the concept of active packaging, which, in addition to protecting, interacts with the packaged product. In this context, flexible films have been prepared from blends of poly(butylene adipate-co-terephthalate), thermoplastic starch (TPS), and cellulose nanowhiskers (CNW) at different concentrations (0–3.0 wt %) and with distinct compatibilizing agents (glycerol, stearic acid, and citric acid) by flat extrusion. Palm oil was packaged in the films, and was stored under accelerated oxidation conditions as a model system. The films were also used for packing lettuce. The TPS increased the rate of water vapor permeability of the blends. The micrographs showed the films with very porous surface as a function of the CNW concentration. In addition to the antimicrobial action pronounced within 10 days (fungi—molds and yeasts; bacteria—mesophilic and psychrotrophic), the film showed a prooxidant action, indicating its suitability for fruit and vegetable packaging. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47699.     

Cocontinuous morphology in vinylidene fluoride based polymers/poly(ethylene oxide) blends

In this work, blends of three different vinylidene fluoride (VdF) based homopolymers and copolymers with poly(ethylene oxide) were investigated. We focused on the continuity domain and, more particularly, on the cocontinuous morphology of these systems. The melt‐mixed blends were characterized by different techniques. The morphology was identified through a selective extraction technique and was confirmed by scanning electron microscopy. Dynamic oscillatory shear measurements were performed with a constant stress rheometer in the linear viscoelastic domain in the whole composition range. Because of the high viscosities and long relaxation times of the VdF‐based polymers, the interfacial effects were hidden by the intrinsic behavior of the neat components. Nevertheless, the combination of the different techniques highlighted the similarity of the systems toward morphological development, whatever the VdF monomers. The experiments and theoretical analysis indicated that the rheological behavior dominated the interfacial effects in such systems with a large viscosity ratio and that it also dictated the boundaries of the continuity domain. The originality of this study came from the use of three different VdF‐based polymers. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013