Biobased PLA/NR-PMMA TPV with balanced stiffness-toughness: In-situ interfacial compatibilization,performance and toughening model

Using rubber to toughen polylactide (PLA) is always accompanied by the sharp reduction in stiffness. Herein, PLA/poly (methyl methacrylate) grafted natural rubber (NR-PMMA) thermoplastic vulcanizates (TPVs) with balanced stiffness-toughness were fabricated. With the addition of 40 wt % NR-PMMA, the impact strength and tensile toughness of PLA/NR-PMMA TPV significantly improved to about 102.7 kJ/m² and 66.1 MJ/m³, respectively, compared with those of 2.7 kJ/m² and 2.4 MJ/m³ for the pure PLA. Meanwhile, the yielding stress was maintained at 34.5 MPa. Fourier transform infrared spectroscopy (FTIR) confirmed the formation of in-situ interfacial compatibilization between PLA and rubber phases. Both tensile and impact toughening mechanism were studied and deduced as considerable energy dissipation provided by the continuous rubber phase. Instrumented notched impact tests demonstrated that the energy dissipating in crack propagation process contributed to the main part of impact toughness. In addition, a novel toughening model based on bicontinuous structure was incorporated, which showed good applicability in predicting the impact strength of PLA/NR-PMMA TPVs.     

Toughening Poly(lactic acid) with Imidazolium-based Elastomeric Ionomers

Imidazolium-based elastomeric ionomers (i-BIIR) were facilely synthesized by ionically modified brominated poly(isobutylene-co-isoprene) (BIIR) with different alkyl chain imidazole and thoroughly explored as novel toughening agents for poly(lactic acid) (PLA). The miscibility, thermal behavior, phase morphology and mechanical property of ionomers and blends were investigated through dynamic mechanical analyses (DMA), differential scanning calorimetry (DSC), scanning electron microscopy (SEM), tensile and impact testing. DMA and SEM results showed that better compatibility between the PLA and i-BIIR was achieved compared to the PLA/unmodified BIIR elastomer. A remarkable improvement in ductility with an optimum elongation at break up to 235% was achieved for the PLA/i-BIIR blends with 1-dodecylimidazole alkyl chain (i-BIIR-12), more than 10 times higher than that of pure PLA. The impact strengths of PLA were enhanced from 1.9 kJ/m² to 4.1 kJ/m² for the PLA/10 wt% i-BIIR-12 blend. Toughening mechanism had been established by systematical analysis of the compatibility, intermolecular interaction and phase structures of the blends. Interfacial cavitations initiated massive shear yielding of the PLA matrix owing to a suitable interfacial adhesion which played a key role in the enormous toughening effect in these blends. We believed that introducing imidazolium group into the BIIR elastomer was vital for the formation of a suitable interfacial adhesion.     

Preparation of core‐shell structured particle and its application in toughening PA6/PBT blends

Combining the excellent mechanical strengths of polyamide 6 (PA6) with the low water absorption of poly(butylene terephthalate) (PBT) was supposed to be a feasible way to prepare a high comprehensive performance material. However, the poor compatibility between PA6 and PBT resulted in low‐notched impact strength of PA6/PBT blends. Poly(n‐butyl acrylate)/poly(methyl methacrylate‐co‐methacrylic acid) (PBMMA), a core‐shell structured modifier with controlled particle sizes, was prepared by seed emulsion polymerization and confirmed by Transmission electron microscope (TEM). The PBMMA particles as toughening modifier and compatilizer were employed to toughen PA6/PBT blends. The notched impact strength of the PA6/PBT blends was significantly increased and the water absorption was reduced with the addition of PBMMA particles. With 23.0 wt% modifier loading, the notched impact strength of the blends was 25.66 kJ/m², which was 4.04 times higher than that of pure PA6/PBT. Meanwhile, the water absorption of the blends was only 1.3%, dropping 53.6% compared with pure PA6 and reducing by 26.6% than PA6/PBT. Scanning electron microscope results showed that the PBMMA particles were dispersed in the PA6/PBT blends homogeneously, and the toughening mechanism was the cavitation of rubber particles and shear yielding of the matrix. Thermo‐gravimetric analysis analysis demonstrated that the compatibility between PA6 and PBT was improved with the addition of core‐shell PBMMA particles. The core‐shell particles could be used as an effective modifier to achieve the high toughness and low water absorption for PA6/PBT blends. Copyright © 2016 John Wiley & Sons, Ltd.     

Improvement of Impact Strength of Polylactide Blends with a Thermoplastic Elastomer Compatibilized with Biobased Maleinized Linseed Oil for Applications in Rigid Packaging

This research work reports the potential of maleinized linseed oil (MLO) as biobased compatibilizer in polylactide (PLA) and a thermoplastic elastomer, namely, polystyrene-b-(ethylene-ran-butylene)-b-styrene (SEBS) blends (PLA/SEBS), with improved impact strength for the packaging industry. The effects of MLO are compared with a conventional polystyrene-b-poly(ethylene-ran-butylene)-b-polystyrene-graft-maleic anhydride terpolymer (SEBS-g-MA) since it is widely used in these blends. Uncompatibilized and compatibilized PLA/SEBS blends can be manufactured by extrusion and then shaped into standard samples for further characterization by mechanical, thermal, morphological, dynamical-mechanical, wetting and colour standard tests. The obtained results indicate that the uncompatibilized PLA/SEBS blend containing 20 wt.% SEBS gives improved toughness (4.8 kJ/m²) compared to neat PLA (1.3 kJ/m²). Nevertheless, the same blend compatibilized with MLO leads to an increase in impact strength up to 6.1 kJ/m², thus giving evidence of the potential of MLO to compete with other petroleum-derived compatibilizers to obtain tough PLA formulations. MLO also provides increased ductile properties, since neat PLA is a brittle polymer with an elongation at break of 7.4%, while its blend with 20 wt.% SEBS and MLO as compatibilizer offers an elongation at break of 50.2%, much higher than that provided by typical SEBS-g-MA compatibilizer (10.1%). MLO provides a slight decrease (about 3 °C lower) in the glass transition temperature (T_g) of the PLA-rich phase, thus showing some plasticization effects. Although MLO addition leads to some yellowing due to its intrinsic yellow colour, this can contribute to serving as a UV light barrier with interesting applications in the packaging industry. Therefore, MLO represents a cost-effective and sustainable solution to the use of conventional petroleum-derived compatibilizers.     

Morphologies,interfacial interaction and mechanical performance of super-tough nanostructured PK/PA6 blends

Nanostructured polyketone (PK)/polyamide 6 (PA6) blends can be readily prepared via melt blending technologies and exhibit ultra-high toughness when PA6 is present as the nanoscale phase domains. When PA6 content is 30 vol%, the impact strength of the blends increases from 21.4 kJ/m² of pure PK to 103.2 kJ/m². The impact strength of the PK/PA6 blends with a 5:5 composition ratio reaches as high as 113 kJ/m². The strong intermolecular force between PK and PA6 molecular chains enables the PA6 nanophase to cavitate to dissipate a significant amount of impact energy and effectively prevents the crack propagation or even terminates the cracks. The fracture mechanism of the PK/PA6 blends was further examined by the essential work of fracture method which proves that PK/PA6 blends show improved ability to prevent crack propagation. This work may deepen the understanding of polymer blend systems with strong hydrogen bonding interaction.     

Properties and morphologies of UV‐cured epoxy acrylate blend films containing hyperbranched polyurethane acrylate/hyperbranched polyester

The properties and morphologies of UV‐cured epoxy acrylate (EB600) blend films containing hyperbranched polyurethane acrylate (HUA)/hyperbranched polyester (HPE) were investigated. A small amount of HUA added to EB600 improved both the tensile strength and elongation at break without damaging its storage modulus (E′). The highest tensile strength of 31.9 MPa and an elongation at break around two times that of cured pure EB600 were obtained for the EB600‐based film blended with 10% HUA. Its log E′ (MPa) value was measured to be 9.48, that is, about 98% of that of the cured EB600 film. The impact strength and critical stress intensity factor (K_1c) of the blends were investigated. A 10 wt % HUA content led to a K_1c value 1.75 times that of the neat EB600 resin, and the impact strength of the EB600/HPE blends increased from 0.84 to 0.95 kJ m^?1 with only 5 wt % HPE addition. The toughening effects of HUA and HPE on EB600 were demonstrated by scanning electron microscopy photographs of the fracture surfaces of films. Moreover, for the toughening mechanism of HPE to EB600, it was suggested that the HPE particles, as a second phase in the cured EB600 film, were deformed in a cold drawing, which was caused by the difference between the elastic moduli of HPE and EB600. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 3159–3170, 2005     

Construction of crosslinking network structures by adding ZnO and ADR in intumescent flame retardant PLA composites

Different proportion of nano zinc oxide (nano ZnO) and chain extender (ADR) were combined with the intumescent flame retardant and then added into the PLA matrix. The thermal stability, flame retardant performance, and mechanical properties were studied. The gel content results showed that crosslinking structures were obtained after the addition of nano ZnO and ADR, which were generated by the catalytic chain scission effect of nano ZnO and chain extension effect of ADR. With addition of 1% nano ZnO and 1.6% ADR, the gel content of flame retardant PLA composite reached the highest value (14.2%). Meanwhile, the corresponding flame retardant PLA composite with 1% nano ZnO and 1.6% ADR, named FRPLA/ZnO/ADR-1, exhibited an overall improved properties including the flame retardant properties and mechanical performance, which passed the UL94 V-0 level with a limiting oxygen index value of 40.1%. Compared to FRPLA (flame retardant PLA without ZnO and ADR), the peak heat release rate and the total smoke production of FRPLA/ZnO/ADR-1were reduced by 60% and 67% respectively, and the final mass improved from 12% to 38%. In addition, the tensile strength and elongation at break of FRPLA/ZnO/ADR-1 increased by 25%, 14% compared with that of FRPLA. The impact strength was 15.1 kJ/m², which is similar to the pure PLA (15.6 kJ/m²). It indicated that the addition of nano ZnO and ADR could balance the flame retardant performance and the mechanical properties of the flame retardant PLA.     

Highly toughened poly(lactic acid) (PLA) prepared through melt blending with ethylene-co-vinyl acetate (EVA) copolymer and simultaneous addition of hydrophilic silica nanoparticles and block copolymer compatibilizer

In this study, a highly toughened PLA was prepared through physical melt-blending with EVA at the presence of hydrophilic nanosilica and SEBS-g-MA block copolymer compatibilizer. The effect of nanosilica and compatibilizer on the morphology, mechanical properties, and linear rheology of the PLA/EVA blends was also investigated. According to TEM images, nanosilica was selectively located in the PLA matrix while some were placed on the interface between the two polymers as was also predicted by thermodynamic and kinetic analysis. Upon the addition of nanoparticles, the interfacial adhesion between the phases was enhanced and the average droplet size decreased. Interestingly, incorporation of SEBS-g-MA induced morphological changes as the spherical EVA droplets turned into a cylindrical shape. DSC results indicated that blending with EVA copolymer resulted in the reduction of crystallization of PLA matrix; however, the crystallinity increased at the presence of nanoparticles up to 5 wt%. The addition of compatibilizer considerably hindered the crystallization of the PLA phase. PLA/EVA blend containing optimum levels of nanosilica exhibited considerably enhanced tensile toughness, elongation at break, and impact strength. On the other hand, the simultaneous addition of nanoparticles and SEBS-g-MA led to synergistic toughening effects and the compatibilized blend containing nanosilica exhibited excellent impact toughness. For instance, the elongation at break of the compatibilized PLA/EVA blend containing the optimal content of nanosilica was increased from 7% to 121% (compared to neat sample). The notched Izod impact strength was also increased from 5.1 to 65 kJ/m². Finally, the microstructure of the blends was assessed by rheological measurements.     

High-Toughness Poly(lactic Acid)/Starch Blends Prepared through Reactive Blending Plasticization and Compatibilization

In this study, poly(lactic acid) (PLA)/starch blends were prepared through reactive melt blending by using PLA and starch as raw materials and vegetable oil polyols, polyethylene glycol (PEG), and citric acid (CA) as additives. The effects of CA and PEG on the toughness of PLA/starch blends were analyzed using a mechanical performance test, scanning electron microscope analysis, differential scanning calorimetry, Fourier-transform infrared spectroscopy, X-ray diffraction, rheological analysis, and hydrophilicity test. Results showed that the elongation at break and impact strength of the PLA/premixed starch (PSt)/PEG/CA blend were 140.51% and 3.56 kJ·m⁻², which were 13.4 and 1.8 times higher than those of pure PLA, respectively. The essence of the improvement in the toughness of the PLA/PSt/PEG/CA blend was the esterification reaction among CA, PEG, and starch. During the melt-blending process, the CA with abundant carboxyl groups reacted in the amorphous region of the starch. The shape and crystal form of the starch did not change, but the surface activity of the starch improved and consequently increased the adhesion between starch and PLA. As a plasticizer for PLA and starch, PEG effectively enhanced the mobility of the molecular chains. After PEG was dispersed, it participated in the esterification reaction of CA and starch at the interface and formed a branched/crosslinked copolymer that was embedded in the interface of PLA and starch. This copolymer further improved the compatibility of the PLA/starch blends. PEGs with small molecules and CA were used as compatibilizers to reduce the effect on PLA biodegradability. The esterification reaction on the starch surface improved the compatibilization and toughness of the PLA/starch blend materials and broadens their application prospects in the fields of medicine and high-fill packaging.     

Highly toughened poly (acrylonitrile–styrene–acrylic)/chlorinated polyethylene blends: Mechanical,rheological and thermal properties

The effect of chlorinated polyethylene (CPE) on the properties of poly (acrylonitrile-styrene-acrylic) (ASA) was investigated. As an impact modifier, CPE effectively toughened ASA. With the addition of 15 phr CPE, the impact strength increased from 25.1 kJ/m² to 41.7 kJ/m². The morphology of the blends exhibited heterogeneous structure and correlated well with the results of impact strength. The glass transition temperature corresponding with ASA remained constant, indicating that CPE did not change the dual-phase structure of ASA. In rheological tests, the enhancement of storage modulus and complex viscosity of ASA, together with Cole-Cole plots, indicated that certain changes in phase structure existed after CPE content exceeded 8 phr. Thermogravimetric analysis results suggested that CPE slightly decreased the onset degradation temperature. Our study showed that CPE, as an impact modifier, can effectively improve the toughness of ASA.     

New insights into the impact toughness of ASA (acrylonitrile-styrene-acrylate) with controllable core–shell structure synthesized by three-stage seeded emulsion polymerization

Acrylonitrile-styrene-acrylate (ASA) with controllable core–shell structure was prepared through three-stage seeded emulsion polymerization. A series of characterizations had been performed to study the effect of different core–shell ratios on the properties of ASA. The most interesting was that the impact strength of ASA exhibited a “wave” variation instead of a linear variation with the increasing loading content of poly(butyl acrylate) (PBA) core. Moreover, the threshold of impact strength appeared at 49.725?wt% PBA content, nearly 33 kJ/m². To explain this unusual variation, an impact schematic was proposed.     

Determination and comparison of the essentialwork of fracture (EWF) of two polyester blends

The fracture toughness of blends of polypropylene terephthalate (PPT) with polyethylene terephthalate (PET) and polybutylene terephthalate (PBT) were investigated. Binary blends were prepared comprising 10:90, 30:70, 50:50, 70:30 and 90:10 mass/mass%. The fracture toughness was determined for each blend using the essential work of fracture (EWF) method and thin film double edge notched tension (DENT) specimens. The specific essential work of fracture, w _e, values obtained for blends of PET/PPT ranged from 27.33 to 37.38 kJ m^–2 whilst PBT/PPT blends yielded values ranging from 41.78 to 64.23 kJ m^–2. Differential scanning calorimetry (DSC) was employed to assess whether or not crystallinity levels influence the mechanical properties evaluated. The fracture toughness of PPT deteriorated with PET incorporation. However, high we values exceeding that of pure PPT were obtained for PBT/PPT blends across the composition range studied.     

Effect of unsaturated hydroxyl-fatty acid modified nano-CaCO3 on the morphological and rheological behavior of PP

A modified nano-calcium carbonate (R-CCR) was prepared by coating a layer of unsaturated hydroxylfatty acid on the surface of CCR powders using a solid state method; the latter were commercial nano-CaCO₃ modified with stearic acid. FTIR studies indicate that the modifier is combined on the surface of CaCO₃. PP/EPDM/nano-CaCO₃ ternary composites were prepared by a melt-mixing method. SEM and TEM were utilized to examine the morphology of the composites. The tensile fractured surface of PP/EPDM/R-CCR showed a fibroid morphology and large-scale yield deformation. The impact fractured surface showed that the amount of cavities in the PP/EPDM/R-CCR system was increased, however their size diminished obviously. R-CCR particles were dispersed uniformly in the PP matrix, and their compatibility was distinctly improved as compared to CCR when the amount of R-CCR was 15 h⁻¹. The tensile strength remained nearly constant (reduced from 27.6 MPa to 27.5 MPa), while the impact strength increased from 9.6 kJ/m² to 15.4 kJ/m² as CCR was replaced by R-CCR. Meanwhile, the bending strength and bending modulus also increased correspondingly. Furthermore, the impact strength of PP/EPDM/R-CCR was maintained at a high level (15.4 kJ/m²), which was more than the sum of that of PP/EPDM and PP/R-CCR (6.6 kJ/m² and 6.1 kJ/m² respectively). This indicates that the R-CCR and EPDM have a significant synergistic toughening effect on PP while maintaining the strength and modulus of virgin PP. Both the storage modulus G′ and loss modulus G″ of PP/EPDM and PP/EPDM/R-CCR composites increase with increasing frequency, but the values of G′ and G″ of the tertiary composite are relatively higher than those of the binary system. The loss factor and viscosity decrease with increasing frequency, but there is little difference between tertiary and binary composites. The apparent viscosity η of the tertiary system containing R-CCR is lower than that of the tertiary system containing CCR and virgin PP. The viscosity of the composites sig-nificantly decreases with increasing shear rate. The mea-sured mechanical properties of the composites indicate that replacing CCR with R-CCR for binary composites could simultaneously enhance the toughness and strength of PP. __________ Translated from Acta Polymerica Sinica, 2008, 4 (in Chinese)     

Poly(lactic acid)/poly(butylene succinate)/calcium sulfate whiskers biodegradable blends prepared by vane extruder: Analysis of mechanical properties,morphology, and crystallization behavior

Ternary blends of PLA/PBS/CSW with different weight fractions were prepared using a vane extruder. The mechanical properties, morphology, crystallization behavior and thermal stability of the blends were investigated. For the PLA/CSW blend, the tensile strength decreased, the flexural strength and modulus increased compared with pure PLA. For PBS, the addition of CSW had little influence on the mechanical properties. For the ternary blends PLA/PBS/CSW, the tensile strength, flexural strength and modulus decreased compared with pure PLA, while the elongation at break and the impact strength increased significantly. The brittle-ductile transition of the blends took place when the PBS weight fraction reaching 30 wt%. As a soft component in the blends, PBS was beneficial to improve the tensile ductility and the toughness of PLA. SEM measurements reveal that PLA/PBS/CSW blends were immiscible. When the weight fraction of PBS was 50 wt%, significant phase separation was observed, and CSW had preferential location in the PBS phase of the blend. DSC measurement and POM observation reveal that CSW had a heterogeneous nucleation effect on PLA and PBS matrix. The addition of PBS improved the crystallization of PLA and the thermal resistance of the PLA/PBS/CSW blends significantly.     

Miscibility and Mechanical Behavior of SAN/NBR Blends

Summary: Aiming the development of high toughness polymer materials, blends of poly(styrene-co-acrylonitrile) (SAN) and poly(butadiene-co-acrylonitrile) (NBR) rubbers, with contents of acrylonitrile (AN) varying from 21 to 45%, were prepared by casting, coprecipitation and monoscrew extrusion followed by injection molding. SAN/NBR blends, prepared in the compositions (w/w) 90/10, 80/20, 70/30, 60/40, and 50/50, were characterized by differential scanning calorimetry (DSC) and Izod impact tests. DSC analyses showed that blends with 33% AN NBR prepared by casting, and with 39% AN NBR prepared by coprecipitation, are partially miscible at 60/40, 70/30 and 80/20 (SAN/NBR) compositions and immiscible for 50/50 compositions. On the other hand, 90/10 SAN/NBR systems were totally miscible. The blends with 45% AN NBR prepared by coprecipitation showed partial miscibility to 50/50, 60/40, 70/30 and 90/10 compositions and total miscibility to 80/20 composition. The NBR addition results in a significant increase in the impact resistance, strongly dependent on the blend composition and the NBR AN content. The best result of impact resistance — 75.2 ± 8.6 (kJ · m⁻²) — was obtained for SAN/NBR 50/50, using 45% AN NBR. This value is 15.7 times bigger than that for pure SAN -4.8 ± 0.7 (kJ · m⁻²).     

Highly efficient toughening effect of ultrafine full-vulcanized powdered rubber on poly(lactic acid)(PLA)

A unique ultrafine full-vulcanized powdered ethyl acrylate rubber (EA-UFPR) was used as the toughening modifier for poly (lactic acid) (PLA). Largely improved tensile toughness was successfully achieved with the incorporation of only 1 wt% EA-UFPR, while the tensile strength and modulus of the blends were almost the same as pure PLA. The highly efficient toughening of PLA by UFPR is mainly ascribed to the strong interfacial interaction between PLA and UFPR and good dispersion of UFPR particles in PLA matrix. Our work provides an effective toughening method to largely improve the mechanical properties of PLA without sacrificing its stiffness, which is very important for the wide application of PLA materials.     

环氧基团功能化弹性体增韧聚乳酸的性能

以2种不同结构的弹性体乙烯-辛烯共聚物接枝甲基丙烯酸缩水甘油酯(POE-g-GMA)和乙烯-丙烯酯甲酯-甲基丙烯酯缩水甘油酯三元共聚物(E-MA-GMA)增韧聚乳酸(PLA), 研究了接枝型与嵌段型弹性体的结构对聚乳酸增韧效果的影响. 结果表明, 接枝型聚合物POE-g-GMA与基体PLA之间具有良好的界面相互作用, 当POE-g-GMA的质量分数为15%时, 共混体系的缺口冲击强度为72.4 kJ/m², 而E-MA-GMA的质量分数为15%时, 共混体系的缺口冲击强度为32.4 kJ/m², 结果表明, 接枝型聚合物POE-g-GMA增韧效果明显优于嵌段型E-MA-GMA.     

Co-continuous phase structure formed in melt processing inducing shear bands to prevent crack propagation: Significant improvement in impact toughness of PMMA

High toughened polymeric materials have a wide application in many fields. Poly(methyl methacrylate) (PMMA) is a typical brittle polymer and it has been difficult to prepare high toughened PMMA material for a long time. To work on this issue, co-continuous phase structure was devised in PMMA/chlorinated polyethylene (CPE) blends through controlling the interfacial tension and viscosity in this work, resulting in the pronounced enhancement of impact toughness. The notched impact strength of co-continuous blends with 40 wt% CPE was up to 28.5 kJ/m², increased by 26 times compared with pure PMMA. Selective extraction experiments, scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS) showed that the CPE network was thin and weak when CPE addition was low, but became dense and strong once the content was more than 20 wt%. Two toughening mechanisms, i.e. cavitation and shear yielding, were put forward based on the micrographs of impact-fractured surfaces and double-notch four-point-bending test. This work may broaden the application prospects of PMMA and provide a new strategy to prepare high toughened polymeric materials through fabricating co-continuous in polymer blends.     

Preparation of Polylactide Composite with Excellent Flame Retardance and Improved Mechanical Properties

Despite the good biodegradable and mechanical properties, poly(lactic acid) still suffers from a highly inherent flammability, which restricts its applications in the electric and automobile fields. In order to improve the flame retardancy of PLA, in this work, melamine polyphosphate (MPP) and zinc bisdiethylphosphinate (ZnPi) were firstly incorporated into PLA, and the synergistic effect of them on flame retardance of PLA was investigated using limiting oxygen index (LOI), UL-94 vertical measurement, scanning electron microscopy (SEM) and cone calorimeter tests etc. The results showed that PLA composite with 15 wt% of MPP/ZnPi (3:2) had the best flame-retardant efficiency with LOI value of 30.1 and V0 rating in UL-94 tests, which was far better than using MPP or ZnPi alone. What is more, although a wide range of flame retardants have been developed to reduce the flammability, so far, they normally compromise the mechanical properties of PLA. On the premise of maintaining good flame-retardant performance, we improved the toughness of flame-retardant PLA composite, and the impact strength of flame-retardant PLA composite was more than tripled (8.08 kJ/m²) by adding thermoplastic urethanes (TPU). This work offers an innovative method for the design of the unique integration of extraordinary flame retardancy and toughening reinforcement for PLA materials.     

Simultaneously toughening and reinforcing poly(lactic acid)/thermoplastic polyurethane blend via enhancing interfacial adhesion by hydrophobic silica nanoparticles

This work focuses on satisfactorily toughening and reinforcing poly(lactic acid)/thermoplastic polyurethane (PLA/TPU) blend with low TPU content (10 wt%) using appropriate amounts of hydrophobic silica nanoparticles (SiO₂) via simple melt mixing. Both thermodynamic prediction and transmission electron microscopy micrographs demonstrate that most SiO₂ nanoparticles distribute at interfaces between the PLA and TPU phases. This improves interfacial adhesion between the phases, which is attributed to good bonding strength between the PLA and SiO₂ via hydrophobic interaction and formation of hydrogen bonds between the TPU and SiO₂. The PLA/TPU (90/10) ternary blend nanocomposite with 2 wt% SiO₂ exhibits obviously high impact strength (about 5.0 and 12.6 times that of the corresponding blend and PLA, respectively) and higher tensile strength than the blend and even the PLA. Crazing is the main reason for improved impact toughnesses of the blend nanocomposites. This work provides a simple and effective strategy to endow PLA/elastomer blends with optimum strength–toughness balance by adding appropriate amounts of nanoparticles.