Co-continuous Structure Research Articles

Co-continuous structure enhanced magnetic responsive shape memory PLLA/TPU blend fabricated by 4D printing

ABSTRACT Combining poly (L-lactic acid) (PLLA) with thermoplastic polyurethane elastomer (TPU) can integrate the advantages of excellent biocompatibility and intrinsic shape memory ability of PLLA and high elasticity and excellent shape memory properties of TPU in the application of minimally invasive surgery for bone tissue engineering. However, TPU easily forms a sea-island-like structure in PLLA matrix, decreasing shape memory properties. In this study, a co-continuous structure of TPU phase in PLLA matrix was constructed by adding Fe3O4 nanoparticles due to the changed interfacial tension and flow behavior of TPU, which endowed the TPU/PLLA/Fe3O4 blend fabricated via selective laser sintering (SLS) with excellent shape memory properties. As a result, the morphology of TPU in the blend changed from sea-island-like structure to complete co-continuous structure with increasing Fe3O4 content (0 to 10wt%), and shape recovery ratios in 50 °C water increased from 66.67 to 95.92%. The introduction of Fe3O4 endowed the blend with magnetic responsive shape memory in alternating magnetic field because Fe3O4 could heat it by generating heat from relative friction and particle collisions. Besides, the tensile modulus and hardness of the specimen with 10wt% Fe3O4 nanoparticles increased. In addition, the blend demonstrated excellent biocompatibility by promoting cell adhesion, spreading, and proliferation.

Solvent-free extrusion of a LiFePO4-based monofilament for three-dimensional printing of a lithium-ion battery positive electrode

To meet the final objective of 3D printing a high-performance liquid-electrolyte lithium-ion battery using Fused Filament Fabrication (FFF), a positive electrode filament formulation based on LiFePO4 and carbon nanofibers (CNF) is, herein, in-depth investigated. A highly-loaded composite monofilament containing a co-continuous structure of an immiscible non-polar (polypropylene-PP) and polar (polycaprolactone-PCL) thermoplastic polymers blend is successfully produced by hot-melt extrusion. This specific formulation confers desirable properties to the 3D printed electrode such as a mechanical integrity during cycling and good affinity with the electrolyte. Furthermore, for up-scale purpose, the incorporation of an optimal amount of thermoplastic elastomers (TPE) into the filament composite to gain in flexibility is examined and its ability to be rolled around a spool at the extruder exit is modelled on the basis of experimental values of mechanical properties. In addition, it is shown that the larger-scale extruded filament has better electronic properties and the corresponding 3D-printed electrode exhibits excellent electrochemical behavior, making it possible to envisage an industrial scale-up production.

Super Toughened PLLA/PBAT Blends with Modified Phase Interface via Constructing Cocontinuous Structure with the Aid of Stereocomplex Crystallites Toward Preparation of a Fully Degradable Material

Super Toughened PLLA/PBAT Blends with Modified Phase Interface via Constructing Cocontinuous Structure with the Aid of Stereocomplex Crystallites Toward Preparation of a Fully Degradable Material

The structural effect of SiC form ceramic on the compressive strength and thermal expansion properties of Cu–SiC composites

With the development of transportation vehicles towards to the direction of heavy load and high speed, the requirement of Cu matrix brake materials was proposed for improving performance in both mechanical and thermal properties. The Cu-SiCf composites is a new kind of friction brake material. To investigate the structural effect of 3D network structured SiC form ceramic on the compressive strength and thermal expansion properties of Cu-SiCf composites, SiCf was synthesized using a template method in conjunction with reaction sintering, while Cu-SiCf composites were prepared using squeeze casting, and exhibiting a co-continuous phase structure. The results reveal that SiC form ceramic reinforcement and constraint mechanisms enhance the overall strength of the Cu alloy through the 3D network structure. SiC form ceramic plays a role in load transfer and overall strengthening of the Cu alloy. With the synergistic effects of these mechanisms, increasing the SiC form ceramic volume fraction improves the compressive strength and reduces the coefficient of thermal expansion of the Cu-SiCf composites.

Ultrahigh tough, self-healing copolymer elastomer crosslinked by reversible imine system

Improvement of toughness is still a challenge for self-healing materials. Most of self-healing materials difficultly balance the mechanical and self-healing property. Here, a molecular design strategy of copolymer is proposed based on three combinations of reversible imine bond, chain motion and thermosensitive hydrogen bond together. The approach initially forms a co-continuous microphase separation structure and then cross-linked by aromatic imine via esterification reaction and Schiff base reaction, which features efficient self-healing, ultrahigh strength and toughness. The resultant elastomer exhibits a high stress at break (≈3 MPa) and high fracture strain (≈600 %). Additionally, the elastomer can reach 95 % self-healing efficiency after healing at 100 °C for 12 h. Extra reversible imine crosslinking displays a doubly promotion for fracture stress, and unchanging strain as well as 1times increase for self-healing efficiency, compared with merely chain motion and hydrogen bonding. This elastomer can be successfully spun into stretchable, conductive, self-healing filaments with core-shell structure by wet spinning and coating methods. It shows excellent corrosion resistance against NaCl, and conductive and self-healing property after coating by PANI polymer. This new type of self-healing polymer is promising to expand the application in future tissue engineering, soft robotics, and biomedical devices.

4D printable maleated poly(styrene-b-ethylene/butylene-b-styrene) / Poly(ethylene-co-vinyl acetate) thermoplastic elastomer blends; effects of blend composition on shape memory and mechanical properties

Shape memory polymers are attracting attention in materials science with their responsive properties and their application areas are gradually developing. By adapting these materials to the additive manufacturing process, four-dimensional (4D) printing technology has been developed. In this study, novel thermo-responsive shape memory polymer blends were prepared for high temperature applications from commercially available polymers using maleated poly(styrene-b-ethylene/butylene-b-styrene) (SEBS-g-MA) and poly(ethylene-co-vinyl acetate) (EVA) and their applicability in three-dimensional (3D) printing was explored. The presence of SEBS-g-MA led to an increase in the degree of crystallization and glass transition temperature of EVA, accompanied by a decrease in crystallization temperature. As the EVA content increased, the blend morphology transitioned from droplet to co-continuous structure. Higher EVA content resulted in an increase in Young's modulus, but a decrease in tensile strength. Nevertheless, these blends exhibited exceptional elongation at break, surpassing 1200%. The blend comprising 70 wt% SEBS-g-MA and 30 wt% EVA demonstrated a synergistic effect, yielding the highest values for elastic modulus, creep resistance, and storage modulus. Furthermore, the blend with 60 wt% SEBS-g-MA and 40 wt% EVA exhibited optimal shape memory performance, achieving a shape fixing ratio of 93.1% and a shape recovery ratio of 98.7%. The conducted analyses demonstrated that the shape recovery of the produced blends could be adjusted according to temperature, and the blends were able to consistently replicate the shape memory effect across multiple cycles. A filament was manufactured for a 3D printer from the blend of 60 wt% SEBS-g-MA and 40 wt% EVA. Using this filament, 4D models having complex geometries were successfully printed. The produced models were able to maintain their temporary shapes to a significant degree. When triggered by heat, these models rapidly returned to their original shapes within a very short period.

Eco-Friendly Blends of Recycled PET Copolymers with PLLA and Their Composites with Chopped Flax Fibres.

The structure and properties of blends of a novel polyethylene terephthalate copolymer (COPET) obtained by chemical recycling of commercial PET with high-molar-mass poly-L-lactide (PLLA) are investigated and compared to corresponding composites with chopped flax fibres. The focus is on the morphology at nano- and micro-scales, on the thermal characteristics and on the mechanical behaviour. The blends are immiscible, as evidenced by virtually unchanged glass transition temperatures of the blend components compared to the neat polymers (49 °C for COPET and 63 °C for PLLA by DSC). At low PLLA content, the blends display a sea-island morphology with sub-micron to micron droplet sizes. As the composition approaches 50/50, the morphology transitions to a coarser co-continuous elongated structure. The blends and composites show strongly improved stiffness compared to COPET above its glass transition temperature, e.g., from melt behaviour at 60 °C for COPET alone to almost 600 MPa for the 50/50 blend and 500 MPa for the 20% flax composite of the 80/20 COPET/PLLA blend. The flax fibres increase the crystallisation rate of PLLA in blends with dispersed PLLA morphology. The evidence of cavitation on the fracture surfaces of blends shows that despite the immiscibility of the components, the interfacial adhesion between the phases is excellent. This is attributed to the presence of aliphatic ester spacers in COPET. The tensile strength of the 80/20 blend is around 50 MPa with a Young's modulus of 2250 MPa. The corresponding 20% flax composite has similar tensile strength but a high Young's modulus equal to 6400 MPa, which results from the individual dispersion and strong adhesion of the flax fibres and leads close to the maximum possible reinforcement of the composite, as demonstrated by tensile tests and nano-indentation. The Ashby approach to eco-selection relying on the embodied energy (EE) further clarifies the eco-friendliness of the blends and their composites, which are even better positioned than PLLA in a stiffness versus EE chart.

Nano Co-Continuous Structure Poly(imide-siloxane)/Phenolic Hybrid Resin Fabricated by Copolymerization for the Thermal Protection System

Nano Co-Continuous Structure Poly(imide-siloxane)/Phenolic Hybrid Resin Fabricated by Copolymerization for the Thermal Protection System

Relationship Between The Co-Continuous Morphology of Immiscible Polymer Blends and the Structure of An In Situ Formed Graft Copolymer.

Suitable compatibilizers are essential to prepare immiscible polymer blends with stable co-continuous morphologies. From the thermodynamic point of view, such compatibilizer should not only reduce the interfacial tension, but also promote the formation of flat interface between different phases. Meanwhile, it must not hinder the coalescence of dispersed phase. Therefore, asymmetric structures are required for those block or graft copolymer compatibilizers. However, from the kinetic point of view, copolymers with asymmetric structures are prone to be dragged out from the interface and form micelles in one phase under the processing conditions, which will lose their compatibilization effects. The balance between such thermodynamic and kinetic factors remains unclear. In this paper, the relationship between the morphology of the compatibilized polystyrene/nylon 6/styrene-maleic anhydride copolymers (PS/PA6/SMA) immiscible polymer blends and the structures of the in-situ formed SMA-g-PA6 graft copolymers as well as the processing conditions are studied. Two kinds of SMA are used as compatibilizers: SMA28 (Mw = 110,000g/mol, MAH content 28wt.%) and SMA11 (Mw = 110,000g/mol, MAH content 11wt.%). After melt blending with PA6 into an internal mixer, the in-situ formed copolymer SMA28-g-PA6 has an average four PA6 side chains grafted on one SMA backbone, while that of SMA11-g-PA6 has only one PA6 side chain. Dissipative particle dynamics (DPD) simulation results indicate that both SMA28-g-PA6 copolymer and PS/PA6/SMA28 blends tend to form co-continuous structure, while SMA11-g-PA6 copolymer and PS/PA6/SMA11 blends form sea-island morphologies. However, these results are confirmed experimentally only at relatively low rotor speed of the internal mixer (60rpm). When the rotor speed of the mixer is higher (105rpm), sea-island morphologies are obtained in PS/PA6/SMA28 blends and co-continuous ones are found in PS/PA6/SMA11 systems. These results indicate that higher shear stress will favor to elongate the minor phase domains and form flat interfaces, which is benefit for the formation of co-continuous morphologies; meanwhile, high shear stress may pull the graft copolymers with asymmetric structures (SMA28-g-PA6) out from the interface of PS and PA6 and induce the formation of sea island morphologies. This article is protected by copyright. All rights reserved.

Fabricating super tough polylactic acid based composites by interfacial compatibilization of imidazolium polyurethane modified carbon nanotubes

The interfacial compatibilization and dispersion of carbon nanotubes (CNTs) in incompatible poly(lactic acid)/poly(butylene terephthalate adipate) (PLA/PBAT) composites are key points for evaluating the performance of the composites. To address this, a novel compatibilizer, sulfonate imidazolium polyurethane (IPU) containing PLA and poly(1,4-butylene adipate) segments modified CNTs, employed in conjunction with multi-component epoxy chain extender (ADR) to toughen synergistically PLA/PBAT composites. The thermal stability, rheological behavior, morphology, and mechanical properties of PLA/PBAT composites were performed by TGA, DSC, dynamic rheometer, SEM, tensile, and notched Izod impact measure. Moreover, the elongation at break and notched Izod impact strength of PLA5/PBAT5/4C/0.4I composites achieved 341 % and 61.8 kJ/m2 respectively, whose tensile strength was 33.7 MPa. The interfacial compatibilization and adhesion were enhanced because of the interface reaction catalyzed by IPU and the refined co-continuous phase structure. The CNTs non-covalently modified by IPU that bridged at the PBAT phase and interface transferred the stress into the matrix, prevented the development of microcracks, and absorbed impact fracture energy in the form of pull-out of the matrix, inducing shear yielding and plastic deformation. This new type of compatibilizer with modified CNTs is of great significance for realizing the high performance of PLA/PBAT composites.

Optimisation of extrusion process parameters to make ABS-PC filament for 3D printing using Taguchi-GRA technique

ABSTRACT This paper attempts to optimise the single screw extrusion (SSE) process parameters for extruding Acrylonitrile-butadiene-styrene (ABS) and Polycarbonate (PC) blend filament, having improved tensile strength and melt flow rate. The melt flow and mechanical properties of ABS-PC blend filament are highly reliant on the SSE process parameters. Thus, optimising the process parameters to fabricate the blend filaments with high performance has become essential. Grey relational analysis has been integrated with the Taguchi method to optimise the SSE process parameters by evaluating the grey relational grades in terms of the performance index. Experimentation has been carried out according to Taguchi’s L9 orthogonal array (OA), which has been designed considering three SSE process parameters, i.e. screw rotation, blend composition and chamber temperature. The co-continuous structure and compatibility between the phases of the blend obtained at ABS:PC 50:50 by wt%. Micrographs and thermographs support the results. The tensile strength of the 3D printed ABS:PC 50:50 by wt.% composite specimen has improved by 38.02% as compared to virgin ABS.

Selective removal of La(III) from mine tailwater using porous titanium phosphate monolith: Adsorption behavior and mechanism

The separation of rare earth elements from mine tailwater has received extensive attention because of the harm to the surrounding environment caused by the low concentrations of rare earth elements in tailwater produced by rare earth mining, and the high demand for rare earth elements in modern society. In this study, a porous titanium phosphate (TP) monolith material was prepared via a sol-gel process accompanied by a phase separation method for the adsorption of La(III) in mine tailwater. The results show that the adsorbent had a stable co-continuous porous skeletal structure. The adsorption performance of the adsorbent was almost unaffected when the solution pH was greater than 2. The PSO kinetic model and Langmuir isotherm model fit the experimental data well, and the maximum adsorption capacity at 30 °C was 253.97 mg·g−1. The TP monolith material exhibited excellent properties such as easy solid-liquid separation, good acid resistance and high adsorption capacity. In addition, the porous TP monolith had not only a certain selectivity for La(III), but also excellent adsorption-desorption and regeneration properties, which promote the application of TP monolith in the recovery of La(III) in actual wastewater. Finally, it was inferred from the mechanistic analysis that the phosphate groups on the material surface played a key role in the adsorption of La(III) by TP monolith materials.

Mixed matrix membranes comprising 6FDA-based polyimide blends and UiO-66 with co-continuous structures for gas separations

Membrane gas separation is considered a highly promising alternative to conventional gas separation. Recently, mixed matrix membranes containing UiO-66 metal–organic frameworks (MOFs) have been demonstrated to achieve high gas separation performance, especially in CO2-related separation. To date, few studies have used morphological control strategies to enhance the gas transport properties of mixed matrix membranes. In this study, we fabricated mixed matrix membranes comprising porous UiO-66 nanoparticles and immiscible 6FDA-based polyimide blends with co-continuous structures. The selective location of UiO-66 nanoparticles within one polymer phase of the co-continuous polymer blend was observed. However, this co-continuous structure cannot be referred to as a double-percolative morphology since the percolative UiO-66 networks did not successfully form. The gas permeability and gas sorption properties of pure gases (H2, CO2, N2, O2, and CH4) in the dense membranes and mixed matrix membranes were measured using the constant-volume variable-pressure method and the dual-volume pressure decay method, respectively. On the basis of the solution–diffusion mechanism, the contributions of gas sorption and gas transport to the overall gas permeation properties were determined and examined. When the UiO-66 content reached 35 wt%, the CO2 permeability of the mixed matrix membranes was significantly increased from 16.5 Barrer to 104.7 Barrer (by 635 %) without scarifying the permeability selectivities of CO2/N2 (16.5 ± 1.5) and CO2/CH4 (31.7 ± 5.8). The results suggest that both the addition of porous UiO-66 nanoparticles and the co-continuous structures contributed to the strongly enhanced gas separation performance of the mixed matrix membranes.

Design of fully biodegradable super-toughened PLA/PBAT blends with asymmetric composition via reactive compatibilization and controlling morphology

• PLA/PBAT blends with co-continuous structure have been fabricated. • Diisocyanate and stereocomplex crystallites of PLA are simultaneously used, for the first time, to achieve co-continuous structure in PLA/flexible polymer blend with asymmetric composition. • The fully biodegradable PLA/PBAT blends exhibit supertoughness with the notched impact strength of 62.6 kJ/m 2 . Super-toughened poly(lactic acid) (PLA)/poly(butylene-adipate-co-terephthalate) (PBAT) blends with co-continuous structure were successfully prepared by taking the advantage of reactive blending and stereocomplex (SC) crystallites located at the interface and poly(l-lactic acid) (PLLA) matrix. In order to generate SC crystallites, poly(d-lactic acid) (PDLA), PBAT and an isosorbide-based diisocyanate (IBDI) were firstly melt blended to prepare masterbatch. Then, it was melt mixed with PLLA to in situ form SC crystallites. Based on this two-step processing strategy, the influence of rotating speed of second mixing step on the formation of co-continuous structure is also investigated. Relatively low rotating speed (30 r/min) would lead to a more perfect co-continuous structure with superior impact strength of 62.6 kJ/m 2 compared with the blends mixed at the intermediate rotating speed (60 r/min). When the rotating speed increases to 90 r/min, the co-continuous structure breaks into irregular particles and the impact strength decreases to 30.0 kJ/m 2 .

High-performance co-continuous Al-Ce-Mg alloy with in-situ nano-network structure fabricated by laser powder bed fusion

A novel Al-Ce-Mg alloy with an in-situ nano-network structure and improved tensile properties was fabricated using laser powder bed fusion (LPBF). The microstructure of the as-fabricated alloy exhibited an extremely fine eutectic Al/Al 11 Ce 3 co-continuous structure, i.e., Al 11 Ce 3 intermetallics with an in-situ nano-network surrounding the interconnected Al matrix. It forms an equiaxed grain in the scanning direction (SD) and columnar grain in the building direction (BD). The yield strength (YS) and ultimate tensile strength (UTS) in SD and BD are 300 ± 11.5 MPa, 438 ± 6.9 MPa, and 303 ± 5.0 MP, 442 ± 3.3 MPa, about three times higher than those of as-cast alloy. The elongations (El) are 9.3 ± 0.7% and 6.2 ± 1.2% in SD and BD, respectively, exhibiting anisotropy. The perfect interfacial bonding between the Al 11 Ce 3 phase and Al matrix combined with nano-scale network structures provided a strong ability to hinder the propagation of microcracks formed within Al 11 Ce 3 particles. Besides, the alloy retained outstanding strength at elevated temperatures with 200 MPa at 300 °C and 100 MPa at 400 °C, which may be attributed to the heat resistance of nano-network Al 11 Ce 3 intermetallics and the extremely low diffusion coefficient of Ce in the Al matrix. This work provides a new idea for developing heat-resistant aluminum alloys with a good combination of strength and ductility via AM processing technique. • Microstructure featured extremely fine eutectic Al/Al 11 Ce 3 co-continuous structure. • Al 11 Ce 3 network is connected by nanocrystalline grains with different orientations. • The as-fabricated Al-Ce-Mg alloy displays superior strength-ductility combination. • The as-fabricated Al-Ce-Mg alloy maintains high strength at elevated temperature.

The effect of tailoring morphology on rheology and dielectric properties of poly (lactic acid) /thermoplastic polyurethane/graphene oxide nanocomposites

To develop eco-friendly elastomeric nanocomposites with high dielectric response, poly(lactic acid) (PLA) was melt compounded with varying amounts of thermoplastic polyurethane(TPU) and a fixed loading of (3 wt.%) graphene oxide(GO). The electrical and dielectric properties of the nanocomposites, in terms of TPU and GO loadings and selective localization of GO nanoplatelets, were correlated with morphological and rheological properties. The results exhibit that inclusion of 3 wt.% GO to PLA/TPU blend leads to nearly 400% improvement in the dielectric constant at high TPU loadings. Increasing the TPU content results in morphological transformation in which a sea-island structure changes to a near co-continuous structure. In addition, in the near co-continuous structure, the selective localization of GO nanoplatelets in the TPU phase and at the interface results in the formation of nano-network percolation at a lower frequency, reflected in both rheological and electrical properties. More conductive paths as well as denser nano-networks in near co-continuous nanocomposite are responsible for higher electrical properties. Near Co-continuous nanocomposites with higher dielectric and electrical properties exhibit higher storage and loss modulus. In short, selective localization of GO and strong conductive path in conjunction with a near co-continuous morphology result in 100% improvement in dielectric response as compared to the system with the sea-island morphology. • Found higher dielectric properties for systems with near co-continuous morphology • Percolated nano-network formed by selective localization of GO in TPU continuous phase • Obtained higher electrical properties, storage and loss moduli for co-continuous nanocomposites • Nearly 400% improvement in dielectric constant achieved at high TPU loadings

Influence of Polymer Processing on the Double Electrical Percolation Threshold in PLA/PCL/GNP Nanocomposites

For the first time, the double electrical percolation threshold was obtained in polylactide (PLA)/polycaprolactone (PCL)/graphene nanoplatelet (GNP) composite systems, prepared by compression moulding and fused filament fabrication (FFF). Using scanning electron microscopy (SEM) and atomic force microscopy (AFM), the localisation of the GNP, as well as the morphology of PLA and PCL phases, were evaluated and correlated with the electrical conductivity results estimated by the four-point probe method electrical measurements. The solvent extraction method was used to confirm and quantify the co-continuity in these samples. At 10 wt.% of the GNP, compression-moulded samples possessed a wide co-continuity range, varying from PLA55/PCL45 to PLA70/PCL30. The best electrical conductivity results were found for compression-moulded and 3D-printed PLA65/PCL35/GNP that have the fully co-continuous structure, based on the experimental and theoretical findings. This composite owns the highest storage modulus and complex viscosity at low angular frequency range, according to the melt shear rheology. Moreover, it exhibited the highest char formation and polymers degrees of crystallinity after the thermal investigation by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC), respectively. The effect of the GNP content, compression moulding time, and multiple twin-screw extrusion blending steps on the co-continuity were also evaluated. The results showed that increasing the GNP content decreased the continuity of the polymer phases. Therefore, this work concluded that polymer processing methods impact the electrical percolation threshold and that the 3D printing of polymer composites entails higher electrical resistance as compared to compression moulding.

Non-destructive observation of internal structures of epoxy monolith and co-continuous network polymer using X-ray CT imaging for elucidation of their unique mechanical features and fracture mechanism

New kind of polymer composites, i.e., co-continuous network polymers (CNP), were fabricated by the filling of the continuous pores of an epoxy monolith (EM) with a cross-linked acrylate polymer. The internal structures of EM and CNP were non-destructively observed by X-ray CT imaging. The mechanical properties of EM were highly dependent on the pore and epoxy frame sizes. Increasing the molar ratio of the amino groups to glycidyl groups during the monolith fabrication process created a coarser co-continuous structure. It greatly enhanced the stretching property of EM. Filling the pores of EM with a rubbery cross-linked acrylate polymer as the second component increased the maximum strength of CNP, independent of the pore size. Furthermore, the gap formation at the boundary between the hard phase and the soft phase of CNP was observed by X-ray CT imaging for the broken test piece used for a tensile test. We discussed a mechanism for the deformation and fracture of EM and CNP.

Control of graphene nanoplatelets at the interface of the co-continuous polypropylene/polyamides 6 blend under the elongational flow

Controlling the filler selective distribution at the interface of co-continuous polymer blend is an effective way to fabricate high performance composites. In this work, the graphene nanoplatelets (GNPs) were distributed at the interface of co-continuous polypropylene (PP)/polyamides 6(PA6) blend by melt blending under the elongational flow generated by convergent-divergent channels. And the formation of co-continuous structure and migration mechanism of GNPs in the PP/PA6 blend under the elongational flow were discussed based on the analysis of rheological measurement, scanning electron micrographs, selective etching experiment and thermal conductivity measurement. The results show that both PP and PA6 phase are elongated into fibrous phase structure under the elongational flow. This indeed enlarge the volume ratio range of composites forming co-continuous structure. And GNPs are oriented along the phase interface and stay at the interface during migration under the elongational flow, which can improve its in-plane thermal conductivity. The in-plane thermal conductivity of the PP/PA6/GNPs composites prepared under the elongational flow are all higher than those prepared under the shear flow. Particularly, the composite prepared under the elongational flow with the 65/35 vol ratio of PP/PA6 still kept a co-continuous structure and the GNPs distributed at the interface. Its in-plane thermal conductivity reached a maximum value of 1.13 W/m K.

Self-healing of reversibly cross-linked thermoplastic vulcanizates

To improve the sustainability, reliability and lifetime of polymer-based materials, the researchers show great passion to fabricate polymers with self-healing capacity. However, there are few reports about the self-healing thermoplastic vulcanizates (TPVs), which is ascribed to the fact that the sea-island structure of general TPVs hinders the introduction of self-healing property. In this work, carboxylic carbon nanotubes (S-CNTs) were introduced into polylactide (PLA)/epoxidized natural rubber (ENR) TPV, in which the reconstruction of dynamic reversible bonds and the co-continuous structure of the TPV were utilized to design a PLA/ENR/S-CNTs TPV with excellent self-healing properties and great mechanical strength. The fabricated TPV exhibited the highest self-healing efficiency of 99.7%, while the maximum tensile strength of TPV could exceed 7 MPa. We hope that the experience of this work can provide a basis for more research in self-healing TPV field.