Reinforced polymer blend is a well-practiced area of interest adopted by materials scientist throughout the world due to its tunable end properties. The present study has been fueled by developing an ...immiscible thermoplastic elastomeric blend (polystyrene/ethylene-co- methyl acrylate copolymer) with loading of conducting carbon black (Vulcan XC 72); an overworked conductive clustered carbon filler. The work emphasized selective dispersion of carbon particulates in one phase (ethylene-co-methyl acrylate copolymer) resulting lowering of electrical percolation and excellent EMI shielding effectiveness in low loading. The conductive blend was also cross-checked to establish their superiority in physico-mechanical, rheological behaviors and thermal stability. The microscopic analysis has implied dispersed islands of clustered carbon particles inside blend ensuing path for electronic hopping. The segregated microstructure also has been correlated to their frequency dependent conductivity, skin depth analysis and EMI shielding measurement.
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Morphological transformation only occurs in polymer blends via changing their components, which can be utilized to form double percolation structures. However, the weight percentage of either polymer ...in the blend generally ranges from 40 wt% to 60 wt%, which does not favor the construction of a densely conductive path. Herein, a double percolation structure had been successfully constructed in a polylactide-polycaprolactone (PLA/PCL) blend with only 30 wt% PCL by adding silicon dioxide (SiO2) to the PLA phase. The added SiO2 effectively strengthens the viscosity and elasticity of the PLA phase, which results in the morphological transformation of the PCL phase from segregated to continuous. In the blend, multi-wall carbon nanotubes (MWCNTs) were selectively distributed in the PCL phase to construct a more efficient conductive network, which brings about an enormous increase in conductivity for the nanocomposites. The electrical conductivity of PLA/PCL nanocomposite increases from 1.19 × 10−14 S/m to 4.57 × 10−4 S/m with the addition of 1.0 wt% MWCNTs and 6.0 wt% SiO2. The percolation threshold of the MWCNTs in the nanocomposite (0.11 wt%, i.e. 0.06 vol%) is 125% lower than that without SiO2 (0.28 wt%, i.e. 0.14 vol%). Furthermore, the nanocomposites with SiO2 were found to exhibit an electromagnetic interference (EMI) of approximately 26 dB with only 3.0 wt% MWCNTs, which means it can block 99.997% of microwaves. This study would provide a critical method to design eco-friendly nanocomposites with ultralow percolate threshold and excellent EMI shielding.
The addition of SiO2 can change the viscosity ratio of PLA:PCL, then the morphology inversion occurs. The PCL (30 wt%) phase change from segregated to continue, and the MWCNTs was selectively dispersed in the PCL phase so that the conductive polymer nanocomposites with low percolation threshold and excellent EMI was achieved. Display omitted
•A low percolation threshold of CPCs with excellent EMI was achieved.•It is first time to use the SiO2 to alter the morphology and form the conductive network.•The MWCNTS was selectively dispersed in the PCL phase (30 wt%).
Polycarbonate (PC) has a very low environmental stress crack resistance (ESCR). This work aims at increasing its ESCR as well as its tensile strength and toughness via a hybrid ternary blend (HTB) ...which is composed of PC, hydroxyl-rich polyvinyl butyral (PVB) and hydroxyl-rich silica (SiO2). Selective distribution and fine dispersion of SiO2 in the dispersed phase (PVB) through hydrogen bonding between the PVB and SiO2 endows the HTB with high ESCR, tensile strength and toughness. Two processes are compared to develop the HTB. One is composed of two steps: the SiO2 is dispersed in the PVB dissolved in anhydrous ethanol; after the removal of the ethanol, the resulting (PVB/SiO2) is then blended with the PC in the molten state. The other process is composed of a single step: PVB, SiO2 and PC are directly blended in the molten state. The two-step process yields better properties: The PC/(PVB-10/SiO2-2) containing 10 wt% of PVB and 2 wt% of SiO2 shows higher melt flow index, tensile strength and toughness. More importantly, its ESCR in carbon tetrachloride is 5 times that of the PC. We envision that this work provides a new perspective to the theory of HTB, and opens a promising route to prepare high-performance PC with excellent practicality.
Polycarbonate-based hybrid ternary blends (HTBs) with high environmental stress crack resistance, high strength and high toughness are controllably fabricated by manipulating the distribution and fine dispersion of silica in polyvinyl butyral dispersion phase. This work provides a new perspective to the theory of HTB, and opens a promising route to prepare high-performance PC with better practicality. Display omitted
•HTBs composed of PC, hydroxyl-rich PVB and hydroxyl-rich SiO2 are prepared.•The HBTs exhibit high ESCR, high tensile strength and high toughness.•The two-step process with premixed PVB/SiO2 yields better properties than the one-step process.
Selective distribution of carbon nanotubes and morphology of conductive polymer composites were very important factors to their electrical conductivity and electromagnetic waves (EMW) shielding ...performance. Herein, the migration behavior of carbon nanotubes (CNTs) in co-continuous poly(lactic acid)/poly(ε-caprolactone) (PLA/PCL) blend was investigated via pre-compounding CNTs in one phase and controlling the mixing time. Because of the higher interaction between CNTs and PCL phase, the migration of CNTs happened from PLA phase to PCL phase when CNTs were pre-mixed with PLA. Due to the viscosity enhancement of pre-compounding PCL/CNT and PLA/CNT, the matching viscosity-dependent morphology was obvious in the composites with different mixing sequences. The better viscosity matching of two polymer phases resulted in the smaller size of two phases, which had more interfaces to enhance microwave attenuation. The effect of CNTs migration and mixing rates on morphological size and EMW shielding performance of the composites were also evaluated. Specifically, the composites with pre-mixing PCL/CNT and then PLA at low shear stress exhibited the smaller size of phases and higher EMW shielding effectiveness (SE) values because of higher interfacial polarization and higher multiple reflection/scattering.
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•Carbon nanotubes prefer to disperse in PCL phase in all the composites.•Migration of CNTs is the thermodynamic and kinetic behavior.•Interfacial driving-separating-dividing-coalescing is repeated to migrate CNTs.•Matching viscosity-dependent morphology is found in the composites.•Smaller size of phases lead to more interfaces and enhance EMW shielding.
Tailoring the distribution of functional fillers in co-continuous polymeric matrix is a new approach for fabricating high-performance composites. Herein, the selective distribution of strontium ...titanate (SrTiO3, ST) in a co-continuous poly(methyl methacrylate)/chlorinated polyethylene (PMMA/CPE, 70/30) matrix was achieved via altering the mixing sequence and adjusting the wetting coefficient (ωa). The results showed that the SrTiO3 distributed in CPE phase was more helpful to improve the dielectric constant and had little influence on the dielectric loss factor. The dispersibility of surface modified SrTiO3 in PMMA phase was the most uniform and promoted the composite keeping the best mechanical properties among all composites. The selective distribution of SrTiO3 in co-continuous structure also significantly influenced the rheological properties. The conclusions obtained in this work are beneficial to the manufacture of composites with appropriate dielectric properties and excellent mechanical properties by the selective distribution of inorganic particles in a co-continuous polymeric matrix.
In this work, we successfully designed remotely, locally thermal/magnetic/light triggered shape memory biobased polylactide/epoxidized natural rubber thermoplastic vulcanizates (PLA/ENR TPVs) via ...regulating the distribution of ferriferrous oxide (Fe3O4). The TPVs exhibited novel bicontinuous structure, which played a vital role in shape memory effect (SME). The distribution of Fe3O4 in the TPVs was regulated by changing the feeding sequence of Fe3O4 during the dynamic vulcanization. Exhilaratingly, when Fe3O4 was selectively distributed in the ENR phase, the biobased TPVs exhibited the highest Rf (~99%) and Rr (>90%) even after five cycles because of the impeccable structure and reinforcement of ENR. Meanwhile, the TPVs also exhibited super-toughness (88.06 kJ/m2) without sacrificing its tensile strength. Moreover, the incorporation of Fe3O4 provided the TPVs with remotely/locally triggered SME, in which the TPVs could quickly recover to their initial shape in an alternating magnetic field or under near-infrared light (808 nm), which showed great potential in intelligent medical devices.
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In this work, multi-stimuli-responsive shape memory PLA/epoxidized natural rubber (ENR)/ferriferrous oxide (Fe3O4) thermoplastic vulcanizates (TPVs) with balanced stiffness–toughness were designed ...via dynamic vulcanization. Regulated by thermodynamic factors and kinetic factors, Fe3O4 was selectively distributed in the continuous ENR phase or at the PLA/ENR interface, which played a crucial role in reinforcing rubber and interfacial compatibilization. Therefore, excellent multi-stimuli-responsive shape memory behavior and significantly improved impact strength were achieved without decreasing its tensile strength. With 30 phr Fe3O4, impact strength reached 90.08 kJ/m2 (without fracture), which was 31 times that of neat PLA. Meanwhile, the TPVs could recover their original shape in merely several seconds along with the shape recovery ratio of 96.63% in the thermal field. Additionally, Fe3O4 also endowed the TPVs with a magnetic-/light-induced shape memory effect in an alternating magnetic field and under the near-infrared light (808 nm) irradiation, which exhibited great potential in intelligent biomedical areas.
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•Reactive nanoparticles promotes the transformation of the core-shell structure into a cocontinuous morphology in polymer blends.•The strength of polypropylene blends is improved by ...reducing the content of elastomer and strengthening the elastomer.•A novel method for preparing magnetic non-polar polymer composites with balanced strength and toughness was proposed.
Herein, a new magnetic super-tough polypropylene (PP) composite was developed via one-step melt blending with maleic anhydride grafted ethylene-octene copolymer (POE-g-MAH) and reactive nano-Fe3O4. The reactive nano-Fe3O4 with polyamide (PA) tails (PA-Fe3O4) was prepared by in situ ring-opening polymerization PA with amino-modified Fe3O4. By regulating the ratio of POE-g-MAH to PA-Fe3O4, PA-Fe3O4 nanoparticles can selectively and uniformly distribute in the POE-g-MAH phase, reinforcing the POE-g-MAH phase and reducing its processing viscosity synchronously as a new plasticizer and compatibilizer. Meanwhile, a cocontinuous morphology was formed in the PP/POE-g-MAH/PA-Fe3O4 composite at a low elastomer content, contributing to the dramatically enhanced toughness of the PP matrix without deteriorating the processing flowability. In particular, adding 4 wt% PA-Fe3O4 into PP/POE-g-MAH (weight ratio: 80/20), the notched Izod impact strength of the composite reached 74.2 kJ/m2, which was enhanced by approximately 247%. In addition, these super-tough PP composites have excellent flexibility and room temperature soft magnetic performance. This study provides a novel and feasible strategy to fabricate magnetic polymer composites with excellent mechanical properties via manipulating the morphology of the composites.
Engineering blend structure with interfacial distribution of nanoparticles is a cost-effective strategy for achieving materials with extraordinary performances. Herein, poly (methyl methacrylate) ...(PMMA) homopolymer was sparsely grafted onto the surface of hydroxylated multi-walled carbon nanotubes (MWCNTs-OH) by miniemulsion polymerization and such modified MWCNTs-g-PMMA were introduced into immiscible engineering blend of polycarbonate (PC) and polyvinylidene fluoride (PVDF) to prepare conductive polymer composites (CPCs). With the help of the miscibility of PMMA with PC and PVDF, MWCNTs-g-PMMA were selectively located at the interface of co-continuous PC/PVDF blend, while MWCNTs-OH were distributed in the PC phase. The interfacial distribution and aggregation of MWCNTs-g-PMMA endowed the ternary nanocomposite with long-term stable excellent electrical conductivity and ultralow percolation threshold of 0.002 vol%.
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•PMMA is sparsely grafted on the surface of MWCNTs via miniemulsion polymerization.•The interfacial location of MWCNTs-g-PMMA remarkably improves electrical properties.•MWCNTs-g-PMMA has an ultralow percolation threshold (0.002 vol%) in PC/PVDF blends.•PC/PVDF/MWCNTs-g-PMMA may have potential applications in EMI shielding.
A stable co-continuous morphology was achieved in immiscible polycarbonate (PC)/polyamide 66 (PA66) blend by controlling the selective distribution of multi-walled carbon nanotubes (MWCNT) and ...aluminum nitride (AlN) nanoparticles. SEM and TEM tests proved that hybrid fillers were both located in PA66 phase. Selective etching process was applied to confirm the gradual variation of morphologies. It indicated that the compatibilities between PC and PA66 were gradually enhanced since the phase size reduced significantly and the interface of two phases blurred after the fillers were incorporated. DMA confirmed that the glass transition temperature of PC and PA66 appeared a trend to merge, besides, the tensile properties were enhanced. TGA indicated that the in-situ generated PC-b-PA66 copolymer played an important role in the compatibilization effect. Besides, the raised interconnectivities were proved by theoretical models and the maximum thermal conductivity of 1.3 W/mK at hybrid fillers loading of 24.78 vol% was obtained.
