Compatibilization of poly(lactic acid)/ethylene‐propylene‐diene rubber blends by using organic montmorillonite as a compatibilizer

This work focuses on phase morphology and properties of immiscible poly(lactic acid)/ethylene‐propylene‐diene rubber (PLA/EPDM) blends compatibilized with organic montmorillonite (OMMT). Effect of OMMT loading on phase morphology, mechanical properties, and blown film bubble stability was investigated. Transmission electron micrographs show that a large number of OMMT nanolayers locate at interfacial region between PLA and EPDM phase, as well as in EPDM phase due to higher affinity of OMMT with EPDM. Scanning electron micrographs show that EPDM domain size decreases largely with increasing OMMT loading, which is associated with reduction of interfacial energy and inhibition of coalescence by the OMMT locating at the interface, acting as an emulsifier to enwrap the discrete domains. As OMMT loading increases from 0 to 1 phr, elongation at break increases from 20.4 to 151.7% and notched impact strength is enhanced from 8.2 to 31.7 kJ?m^?2. The reduced EPDM domain is the main reason for enhanced toughness of PLA/EPDM/OMMT samples according to crazing with shear yielding mechanism. However, with more than 2 phr of OMMT, the toughness decreases largely due to excessive stress concentration and OMMT aggregation. Attempts were made to produce ductile films from the PLA/EPDM/OMMT nanocomposites by using blown film extrusion. Improvement in blown film bubble stability and tensile ductility of PLA/EPDM/OMMT films also shows that OMMT is an efficient compatibilizer, as well as a processing aid for PLA/EPDM blends. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 44192.     

Compatibilization of poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate)–poly(lactic acid) blends with diisocyanates

Poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate) (PHBV) was blended with poly(lactic acid) (PLA) with various reactive processing agents to decrease its brittleness and enhance its processability. Three diisocyanates, namely, hexamethylene diisocyanate, poly(hexamethylene diisocyanate), and 1,4‐phenylene diisocyanate, were used as compatibilizing agents. The morphology, thermomechanical properties, and rheological behavior were investigated with scanning electron microscopy, thermogravimetric analysis, differential scanning calorimetry, tensile testing, dynamomechanical thermal analysis in torsion mode (dynamic mechanical analysis), and oscillatory rheometry with a parallel‐plate setup. The presence of the diisocyanates resulted in an enhanced polymer blend compatibility; this led to an improvement in the overall mechanical performance but did not affect the thermal stability of the system. A slight reduction in the PHBV crystallinity was observed with the incorporation of the diisocyanates. The addition of diisocyanates to the PHBV–PLA blend resulted in a notable increase in the final complex viscosity at low frequencies when compared with the same system without compatibilizers. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44806.     

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     

Biodegradable polypropylene/thermoplastic starch nanocomposites incorporating halloysite nanotubes

In this work, polypropylene/thermoplastic starch (PP/TPS) with and without halloysite nanotubes (HNTs) was prepared via melt mixing in order to obtain environmentally friendly plastics. PP‐grafted maleic anhydride (PP‐g‐MA) was used to improve the compatibility among the highly incompatible polymers. The mechanical characterization showed a reduction in the tensile properties of the polymer when TPS increased; however, HNT successfully compensated for some of the observed losses. The results from the thermogravimetric analysis (TGA) indicated that HNT is an efficient reinforcement for the thermal stability improvement. TPS caused an increase in the storage modulus (G′) and the complex viscosity (η*) which marks a change in the viscoelastic properties of the system. The scanning electron microscope (SEM) images showed the effective plasticization of starch and better dispersion of TPS in the presence of HNT. Some samples were also buried in the soil to measure their sustainability after their lifetime lapse. The results indicated that TPS improves the biodegradability of the PP/TPS system. PP considerably lowered the moisture uptake of TPS; nevertheless, HNT caused a slight increase in the moisture absorption. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45740.     

Crystallinity and mechanical properties of polylactide/ether‐amide copolymer blends

The present study focuses on the improvement of impact properties and particularly on the interaction between crystallinity development and mechanical properties of impact modified polylactide (PLA). The PLA was toughened by the addition of a random linear ether‐amide copolymer (PEBAX 3533?). A random copolymer of ethylene, methyl‐acrylate, and glycidyl‐methacrylate (LOTADER AX8900?) was also used to reactively compatibilize the ether‐amide copolymer with the PLA matrix. Melt rheology of the blends was investigated in small amplitude oscillatory shear and showed that the impact modifier could significantly influence the viscoelastic response of the material. The Izod impact resistance and tensile properties were measured using standard testing protocols. The blend morphology was also examined using scanning electron microscopy on cryofractured and microtomed surfaces, while the crystalline morphology was assessed by optical microscopy. A sub‐micron dispersion of the impact modifier was achieved in the presence of the reactive compatibilizer. Significantly improved impact strength was found with 10 wt % impact modifier. High crystallinity samples showed the highest impact strength with values reaching 68 kJ/m², hence a 20‐fold improvement with respect to the neat PLA. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134 , 44677.     

Bio‐based diblock copolymers prepared from poly(lactic acid) and natural rubber

New bio‐based diblock copolymers were synthesized from poly(lactic acid) (PLA) and natural rubber (NR). NR polymer chains were modified to obtain hydroxyl telechelic natural rubber oligomers (HTNR). Condensation polymerization between PLA and HTNR was performed at 110°C during 24 or 48 h. The molecular weight of PLA and HTNR and the molar ratio PLA : HTNR were varied. The new ester linkage in the diblock copolymers was determined by ¹H‐NMR. The molecular weight of the diblock copolymers determined from SEC agreed with that expected from calculation. The thermal behavior and degradation temperature were determined by DSC and TGA, respectively. The diblock copolymers were used as a toughening agent of PLA and as a compatibilizer of the PLA/NR blend. PLA blended with the diblock copolymer showed higher impact strength, which was comparable to the one of a PLA/NR blend. The former blend showed smaller dispersed particles as showed by SEM images, indicating the increase in miscibility in the blend due to the PLA block. The compatibilization was effective in the blends containing ～10 wt % of rubber. At a higher rubber content (>10 wt %), coalescence of the NR and diblock copolymer was responsible of the larger rubber diameter in the blends, which causes a decrease of the impact strength. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41426.     

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.     

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.     

Cassava starch‐based nanocomposites reinforced with cellulose nanofibers extracted from sisal

Cellulose nanofibers were extracted from sisal and incorporated at different concentrations (0–5%) into cassava starch to produce nanocomposites. Films' morphology, thickness, transparency, swelling degree in water, water vapor permeability (WVP) as well as thermal and mechanical properties were studied. Cellulose nanofiber addition affected neither thickness (56.637 ± 2.939 µm) nor transparency (2.97 ± 1.07 mm^?1). WVP was reduced until a cellulose nanofiber content of 3.44%. Tensile force was increased up to a nanocellulose concentration of 3.25%. Elongation was decreased linearly upon cellulose nanofiber addition. Among all films, the greatest Young's modulus was 2.2 GPa. Cellulose nanofibers were found to reduce the onset temperature of thermal degradation, although melting temperature and enthalpy were higher for the nanocomposites. Because cellulose nanofibers were able to improve key properties of the films, the results obtained here can pave the route for the development and large‐scale production of novel biodegradable packaging materials. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134 , 44637.     

Properties of Bloodmeal/Linear Low‐density Polyethylene Blends Compatibilized with Maleic Anhydride Grafted Polyethylene

Novatein thermoplastics from bloodmeal (NTP) were blended with linear low‐density polyethylene (LLDPE) using maleic anhydride grafted polyethylene (PE‐g‐MAH) as compatibilizer. The compatibilizing effect on mechanical, morphology, thermal properties, and water absorption were studied and compared with blends without compatibilizer. The amount of polyethylene added was varied between 20 and 70% in NTP with addition of 10% compatibilizer. An improvement in compatibility between NTP and LLDPE was observed across the entire composition range and the difference were more pronounced at higher NTP contents where the tensile strength of blends was maintained and never dropped below that of pure NTP. Theoretical models were compared to the results to describe mechanical properties. A finely dispersed small particles of NTP in compatibilized blends were observed using SEM. Improved compatibility has restricted chain movement resulting in slightly elevated T_g revealed by DMA. On the other hand, water absorption of the hydrophilic NTP has been decreased when blending with hydrophobic LLDPE. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 1890–1897, 2013     

Transparent low‐density polyethylene/starch nanocomposite films

Low‐density polyethylene (LDPE)/starch nanocomposite films were prepared by melt extrusion process. The first step includes the preparation of starch–clay nanocomposite by solution intercalation method. The resultant product was then melt mixed with the main matrix, which is LDPE. Maleic anhydride‐grafted polyethylene (MAgPE), produced by reactive extrusion, was used as a compatibilizer between starch and LDPE phases. The effects of using compatibilizer, clay, and plasticizers on physico‐mechanical properties were investigated. The results indicated that the initial intercalation reaction of clay layers with starch molecules, the conversion of starch into thermoplastic starch (TPS) by plasticizers, and using MAgPE as a compatibilizer provided uniform distribution of both starch particles and clay layers, without any need of alkyl ammonium treatment, in LDPE matrix. The nanocomposite films exhibited better tensile properties compared to clay‐free ones. In addition, the transparency of LDPE film did not significantly change in the presence of TPS and clay particles. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Esterification of Kraft lignin as a method to improve structural and mechanical properties of lignin‐polyethylene blends

Lignin is a promising candidate for blends with thermoplastic polymers. Still, this endeavour is a challenge due to poor compatibility between both components. In this article, the effect of lignin esterification on the improvement of the compatibility between hardwood Kraft lignin and high‐density polyethylene (PE‐HD) is investigated. For this purpose, lignin was esterified with acetic, propionic, and butyric anhydride; its amount in the blends varied from 10 to 40%. Light microscopic images of blends show a reduction in particle size and a more homogeneous distribution with increasing length of the ester carbon chains (C2 to C4). Modification of lignin enhances the moduli and strength characteristics of the blends. Butyrated lignin performs best, as tensile strength of blends can be retained near that of pure PE‐HD with up to 40% lignin content. An additional investigation of unmodified lignin with reduced particle size confirms that modification is the decisive factor to enhance blend properties; a sole reduction of particle size is insufficient. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44582.     

Freezing/thawing effects on the exfoliation of montmorillonite in gelatin‐based bionanocomposite

Freezing/thawing is used as a new method to elaborate exfoliated gelatin‐Montmorillonite (MMT) bionanocomposites. The data of X‐ray diffraction and transmission electron microscopy indicate that freezing/thawing is an effective approach to exfoliate the clay for concentrations higher than 5 mass% in gelatin matrix. In addition, after freezing/thawing process to introduce, the crystallinity (triple‐helix content) of gelatin‐MMT bionanocomposites is improved, revealing that freezing/thawing method has the advantages for gelatin molecules to renature into triple‐helix. Specially, the data of Fourier transform infrared indicate that freezing/thawing may be induce more hydrogen bond interactions in gelatin‐MMT bionanocomposites due to the better dispersion of MMT. The mechanical measurements and thermogravimetric analysis show that gelatin‐MMT bionanocomposites prepared by freezing/thawing display enhanced mechanical properties and thermal stability in comparison with the ones prepared by conventional blending at the same clay content. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Evaluating PE/PLA interfacial tension using ternary immiscible polymer blends

Blending with ethylene-based flexible polymers such as polyethylene (PE) is one of the strategies to toughen poly(lactic acid) (PLA), an inherently brittle biodegradable plastic enjoying growing demands worldwide. Interfacial tension plays a crucial role in blend formulation. Yet several literature reports on the PE/PLA interfacial tension contradict each other, giving ~5 mN/m and ~11 mN/m. In this work, we demonstrate that the PE/PLA interfacial tension is at least 9 mN/m. We use a cocontinuous PE/polystyrene (PS)/PLA ternary blend. Scanning electron microscopy (SEM) revealed complete wetting morphology with PS phase separating PE and PLA phases in the ternary blend. In addition, the complete wetting behavior was maintained at a PS volume fraction as low as 3%. This morphology together with the Harkins equation, indicate that the PE/PLA interfacial tension is higher than 10.5 ± 1.4 mN/m at 180°C.     

Small‐molecule‐induced miscibility of isosorbide‐based polycarbonate with bisphenol A polycarbonate

In this study, we investigated the influence of the small molecule 4,4′‐thiobis(6‐tert‐butyl‐m‐methyl phenol) (AO300) on the miscibility of poly(isosorbide‐co‐1,4‐cyclohexanedimethanol carbonate) (IcC–PC) with bisphenol A polycarbonate (BPA–PC) through the formation of hydrogen‐bonding networks. Differential scanning calorimetry and morphological observation revealed that the initially, immiscible BPA–PC/IcC–PC blends become miscible through the addition of small molecules. Fourier transform infrared spectroscopy confirmed that intermolecular hydrogen bonds formed between the hydroxyl groups of AO300 and the carbonyl groups of the studied polycarbonates. These polycarbonates exhibited different hydrogen‐bonding behaviors and various degrees of glass‐transition temperature composition dependence. Dynamic mechanical analysis demonstrated that AO300 played an antiplasticization role in the BPA–PC/IcC–PC blends with improved storage moduli. To our knowledge, this article is the first to describe the miscibility of isosorbide‐based polycarbonate with BPA–PC. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44537.     

Improving the barrier character of polylactide/phenoxy immiscible blend using poly(lactide‐co‐ɛ‐caprolactone) block copolymer as a compatibilizer

The improvement of the barrier character of polylactide by the addition of poly(hydroxy ether) of bisphenol A (Phenoxy) and poly(lactide‐co ‐?‐caprolactone) copolymer that acts as a compatibilizer is studied. First, differential scanning calorimetry, Fourier transformed infrared spectroscopy, and scanning electron microscopy show that the addition of the copolymer allows to obtain a miscible ternary system. The permeability of polylactide to water vapor, oxygen, and carbon dioxide is enhanced with the addition of phenoxy but better improvement in its barrier character is obtained with the addition of the compatibilizer. The effects of different factors such as miscibility, glass transition temperature, and crystallinity on the transport properties are analyzed. Several permeability prediction models for heterogeneous systems have been applied obtaining quite good results for water vapor and oxygen permeability. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134 , 45396.     

Improving the toughening in poly(lactic acid)‐thermoplastic cassava starch reactive blends

Poly(lactic acid) (PLA), a physical blend of PLA and thermoplastic cassava starch (TPCS) (PLA‐TPCS), and reactive blends of PLA with TPCS using maleic anhydride as compatibilizer with two different peroxide initiators [i.e., 2,5‐bis(tert‐butylperoxy)‐2,5‐dimethylhexane (L101) and dicumyl peroxide (DCP)] PLA‐g‐TPCS‐L101 and PLA‐g‐TPCS‐DCP were produced and characterized. Blends were produced using either a mixer unit or twin‐screw extruder. Films for testing were produced by compression molding and cast film extrusion. Morphological, mechanical, thermomechanical, thermal, and optical properties of the samples were assessed. Blends produced with the twin‐screw extruder resulted in a better grade of mixing than blends produced with the mixer. Reactive compatibilization improved the interfacial adhesion of PLA and TPCS. Scanning electron microscopy images of the physical blend showed larger TPCS domains in the PLA matrix due to poor compatibilization. However, reactive blends revealed smaller TPCS domains and better interfacial adhesion of TPCS to the PLA matrix when DCP was used as initiator. Reactive blends exhibited high values for elongation at break without an improvement in tensile strength. PLA‐g‐TPCS‐DCP provides promising properties as a tougher biodegradable film. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46140.     

Compression molding and melt‐spinning of the blends of poly(lactic acid) and poly(butylene succinate‐co‐adipate)

Poly(lactic acid) (PLA) is a biobased polymer made from biomass having high mechanical properties for engineering materials applications. However, PLA has certain limited properties such as its brittleness and low heat distortion temperature. Thus, the aim of this study is to improve toughness of PLA by blending with poly(butylene succinate‐co‐adipate) (PBSA), the biodegradable polymer having high toughness. Polymer blends of PLA and PBSA were prepared using a twin screw extruder. The melt rheology and the thermal property of the blends were examined. Further the blends were fabricated into compression molded parts and melt‐spun fiber and were subjected to tensile and impact tests. When the PBSA content was low, PBSA phase was finely dispersed in the PLA matrix. On the other hand, when the PBSA content was high, this minor phase dispersed as a large droplet. Mechanical properties of the compression molded parts were affected by the dispersion state of PBSA minor component in PLA matrix. Impact strength of the compression molded parts was also improved by the addition of soft PBSA. The improvement was pronounced when the PBSA phase was finely dispersed in PLA matrix. However, the mechanical property of the blend fibers was affected by the postdrawing condition as well as the PBSA content. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41856.     

Use of poly(ethylene‐co‐vinyl alcohol) as compatibilizer in LDPE/thermoplastic tapioca starch blends

Poly(ethylene‐co‐vinyl alcohol) (EVOH) was used as a compatibilizer to make blends of low‐density polyethylene (LDPE) and plasticized starch (TS). The tensile properties and impact strength were measured and compared with those of neat LDPE. The morphology of the blend specimens, both fractured and unfractured, was observed by scanning electron microscopy. Comparison of the properties showed that the impact strength of the blend improves significantly by the addition of a compatibilizer even with a high TS loading of 40 and 50% (by weight). A high elongation at break almost matching that of neat polyethylene was also obtained. The blend morphology of the etched specimens revealed fine dispersion of the starch in the polyethylene matrix, while the fracture surface morphology clearly indicate that the failure of compatibilized blends occurs mainly by the ductile mode. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 3126–3134, 2002     

Elaboration and characterization of bioblends based on PVC/PLA

With the aim to develop new biomaterials (bioblends) to be used in the field of waste elimination, this contribution focuses on the elaboration and characterization of new materials based on poly (vinyl chloride) (PVC) and poly (lactic acid) (PLA). The bioblends based on PVC/PLA were prepared by melt mixing in the absence and presence of maleic anhydride (MAH). The binary blends were first characterized in terms of thermal (glass transition temperature) and mechanical properties (tensile and micro‐hardness). Their thermal stability was investigated by thermogravimetric analysis (TGA). The results showed that this pair of polymers is not miscible and exhibited lower properties than those of the separated polymers. The in situ compatibilization was then performed using MAH and dicumyl peroxide (DCP) as an initiator. The presence of MAH enhanced the processability of the bioblends by decreasing the temperature of mixing. The properties of subsequent PVC/PLA bioblends were investigated through tensile and micro‐hardness testing, thermal analysis (DSC and TGA), and SEM. From the mechanical results, high level of compatibility was found when introducing MAH. The TGA studies indicated that the incorporation of PLA in PVC (matrix) increased thermal stability of the bioblend. Microscopic observations revealed uniformly dispersed PLA in the PVC matrix, confirming that phase separation has disappeared in the presence of MAH. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40045.