Conventional Melt Blending Research Articles

Enhancing electrical characteristics and electromagnetic interference shielding effectiveness in thermoplastic elastomeric polymer blends by utilizing the selective distribution of conductive black

The selective distribution of filler within polymer blends presents a compelling advantage, notably manifesting as a reduced percolation threshold when compared to an individual polymer matrix with a random filler dispersion. In this context, a thermoplastic elastomeric (TPE) blend comprising ethylene propylene diene rubber (EPDM) and linear low-density polyethylene (LLDPE), denoted as EL, has been meticulously formulated. The incorporation of varying amounts of conductive carbon black (Vulcan XC 72; VCB) into this TPE matrix has been achieved through conventional melt blending, yielding a composite material with exceptional electromagnetic interference (EMI) shielding effectiveness of -27.80 dB at 50 phr (parts per hundred rubber). This success is credited to the creation of a linked structure resulting from a dual-step percolation process. The selective distribution of carbon black (CB) throughout the TPE mixture results in a decreased critical concentration for connectivity and enhanced electromagnetic interference (EMI) shielding performance. This advancement underscores the potential of EPDM-LLDPE-VCB (ELV) composites to safeguard against electromagnetic radiation. It paves the way for their utilization in various techno-commercial applications, where a balance of mechanical strength, thermal stability, and flexibility is crucial.Graphical

Coumarin-DPPO a new bio-based phosphorus additive for poly(lactic acid): Processing and flame retardant application

This study addresses very important aspects of the sustainable development of new flame retardant materials: (i) the preparation of a novel flame retardant (FR) additive from bio-resource, (ii) its use as FR additive in poly(lactic acid) (PLA) based composites and, (iii) the in vitro toxicity assessment of the FR. The synthesis of this bio-based FR additive was achieved through a phospha-Michael addition of diphenylphosphine oxide (DPPO) and the naturally occurring compound coumarin, yielding 4-(diphenylphosphoryl)chroman-2-one (CU-DPPO). The flame-retarded CU-DPPO PLA composites were prepared either via conventional melt blending of commercially available PLA or through reactive extrusion (REX) of L-lactide. Characterization of the composites was performed through nuclear magnetic resonance (NMR), size exclusion chromatography (SEC) and thermogravimetric analysis (TGA). TGA analysis of the FR-PLA composites showed an increase in thermal stability, confirming the beneficial effect of the CU-DPPO additive. Direct insertion probe mass spectrometry (DIP-MS) analysis was used to gain insight on the mechanism of action of the FR additive, suggesting gas-phase activity. Rheological measurements exhibited the thermo-oxidative stabilizing effect in the modified PLA. The flame retardancy of the melt-blended PLA composites with CU-DPPO was investigated by limited oxygen index (LOI), cone calorimetry and vertical burning tests (UL 94 and BKZ-VB). Samples containing 10 wt.% of CU-DPPO showed improved fire performance with a limiting oxygen index (LOI) of 29%, passing Swiss vertical burning test (BKZ-VB) and obtaining a V-0 rating in the UL 94 test. Moreover, a preliminary toxicity assessment of the CU-DPPO, carried out using an established in vitro platform, showing no adverse effects on cell viability.

Double percolation behavior through the preferential distribution of conductive black in polymer blends to boost electrical properties and EMI shielding effectiveness

The preferential distribution of the filler in the polymer blends leads to a lower percolation threshold in comparison to a single polymer matrix with random filler distribution. Poly(ethylene methyl acrylate) (EMA) and carboxylated acrylonitrile butadiene rubber (XNBR) composites of EMA-XNBR (EX) with a variable amount of conductive carbon black (Vulcan XC 72; VXC) has been prepared by conventional melt blending. These composites have superior electromagnetic interference (EMI) shielding effectiveness to attenuate the hazardous effects and save society from proliferating electromagnetic radiation. The suitable distribution of carbon black lowers the electrical percolation threshold of 12.5 phr by the formation of interconnected architecture following the two-step percolation phenomenon and results in an improved EMI SE of 33.5 dB. The morphological analysis demonstrates that the formation of a polymer-filler network of VXC in an EX technologically compatible blend increases the mechanical and thermal stability of composites by retaining their flexibility, which facilitates the application of EXV composites in techno-commercial fields.

The Fabrication of High-Hardness and Transparent PMMA-Based Composites by an Interface Engineering Strategy.

The high-hardness and transparent PMMA-based composites play a significant role in modern optical devices. However, a well-known paradox is that conventional PMMA-based composites with high loadings of nanoparticles usually possess high surface hardness at the cost of poor transparency and toughness due to the aggregation of nanoparticles. In this work, ideal optical materials (SiO2/PMMA composites) with high transparency and high surface hardness are successfully fabricated through the introduction of the flow modifier Si-DPF by conventional melt blending. Si-DPF with low surface energy and high transparency, which is located at the SiO2/PMMA interface, and nano-SiO2 particles are homogeneously dispersed in the PMMA matrix. As an example, the sample SiO2/PMMA/Si-DPF (30/65/5) shows outstanding transparency (>87.2% transmittance), high surface hardness (462.2 MPa), and notched impact strength (1.18 kJ/m2). Moreover, SiO2/PMMA/Si-DPF (30/65/5) also presents a low torque value of composite melt (21.7 N⋅m). This work paves a new possibility for the industrial preparation of polymer-based composites with excellent transparency, surface hardness, processability, and toughness.

Fluorine-Containing Flow Modifier for BN/PPS Composites Enabled by Low Surface Energy.

In this study, a fluorine-containing flow modifier (Si-DF) with low surface energy is successfully synthesized, which is applied to fabricate ideal electronic packaging materials (BN/PPS composites) with high thermal conductivity, excellent dielectric properties, processability, and toughness by conventional melt blending. Si-DPF is located at the interface between the BN fillers and the PPS matrix, which not only improves the dispersion of BN fillers but also strengthens the interaction. With the help of 5 wt% Si-DF, BN/PPS/Si-DF (70/25/5) still exhibits the high thermally conductive coefficient (3.985 W/m·K) and low dielectric constant (3.76 at 100 MHz) although BN fillers are loaded as high as 70 wt%. Moreover, the sample processes a lower stable torque value (2.5 N·m), and the area under the stress-strain curves is also increased. This work provides an efficient way to develop high-performance polymer-based composites with high thermally conductive coefficients and low dielectric constants for electronic packaging applications.

Foaming of Polylactic Acid/Cellulose Nanocrystal Composites: Pickering Emulsion Templating for High-Homogeneity Filler Dispersions

Polylactic acid (PLA)/cellulose nanocrystal (CNC) composite foams have attracted much attention due to their biodegradability and potential to replace petroleum-based foams. However, the dispersion of (unmodified) CNCs in PLA remains challenging. Here, we used the Pickering emulsion templating method of unmodified CNCs to stabilize PLA microspheres and prepare a concentrated masterbatch. This masterbatch was used in conventional melt blending of pristine PLA to obtain well-dispersed CNCs in PLA with a CNC loading of up to 5 wt %. In comparison, PLA/CNC composites prepared by direct melt blending of CNCs in PLA showed visual agglomerates of CNCs. PLA/CNC composites were batch foamed with CO2 as a physical blowing agent. We demonstrate that the good CNC dispersion obtained by the Pickering emulsion route is favorable for preparing PLA foams with smaller and more uniform cell sizes and with a higher cell density. These results demonstrate that the Pickering emulsion approach to prepare CNC masterbatches for subsequent dispersion in thermoplastics by conventional processing seems promising for numerous industrial applications.

Enhanced thermal conductivity of epoxy composites by constructing thermal conduction networks via adding hybrid alumina filler

AbstractHigh thermal conductivity of polymer composites could be achieved through constructing 3D continuous thermally conductive networks into polymer composites. Herein, we demonstrate a simple, effective method to optimize the segregated alumina networks by using ternary mixture of alumina particles with different diameter ratios (5.8 μm + 2.6 μm + 0.5 μm) at the fixed total content of 60 wt% via conventional melt blending method. The thermal properties of epoxy composites were investigated as a function of the weight fraction and particle size of alumina particles. The thermal conductivity (TC) values of composites with coarse fillers (13.2 μm) are in agreement with Agari model at high filler loading (57 ~ 67 wt%). And the value of C2 was ~0.949 (close to 1), indicating that the formation of heat conduction paths in the composites. The addition of 60 wt% smaller fillers (2.6 μm) facilitates a higher interaction degree between the polymer/fillers, consequently, leads to a higher Tg of 147.8°C. A high TC of 1.109 W m−1 K−1 is achieved as the ratio of alumina filler with different particle sizes is 7/2/1, corresponding to a TC enhancement of 23%–32% compared to the composites with a single particle size filler. A suitable proportion of hybrid fillers is crucial for constructing three‐dimension continuous network, in which nano‐particles filled between the micro‐particles could increase the particle‐to‐particle connectivity.

Shielding Effectiveness, Mechanical and Dielectric Properties of NiO/PCL Nano Composites at Microwave Frequency for Electronic Devices

There is a continuous generation of electromagnetic fields through operations of electronic devices for this reason it is paramount that these fields be shielded so as to prevent interferences. The, conventional method for shielding these fields are by the use of thin metal foils or sheets. The metals foils are heavy, difficult to fabricate, costly and in many cases not suitable for use in many applications. For these reasons, this work is focused on using materials that is flexible, cost effective and durable, with considerable shielding effectiveness (SE). Hence, polycaprolactone (PCL) and nickel oxide (NiO) nanocomposite were synthesized using the conventional melt blending (CMB) technique. The synthesis method used is fast, easy and produces large mass of controlled composites within a short period. Rectangular waveguide, vector network analyzer, coaxial cable and open ended coaxial probe were used in the measurement of microwave properties. Measured scattering parameter was used to calculate the shielding effectiveness of the NiO/PCL composites. Findings indicates that the dielectric constant increased with increasing filler content, where the highest dielectric property was 5.09 for the 62.5 % filler and it was able to shield electromagnetic fields by up to -9.35 dB at the frequency range measured. The average particle size of the NiO nano particles was 40.5 nm using TEM analysis. The best hardness and tensile strength was recorded for the highest loading percentage. It is then concluded that the substrate produced can be tailored for electronic, telecommunication, medical applications and military shield applications.

A statistical approach to investigate the effects of multicomponent fractions on the mechanical properties of PP/PPMA/Talc/POE composites

An immense technological challenge of polypropylene-based composites is in optimising the effect of multicomponent fractions on their mechanical properties. Hence the main aim of the present study is to carry out a systematic statistical approach to investigate the impact of multicomponent fractions on the mechanical properties of Polypropylene (PP)/Talc/ Polyolefin Elastomer (POE) and maleic-anhydride-grafted Polypropylene (PPMA) composites. Response Surface Methodology (RSM) based on Central Composite Design (CCD) has been implemented as the design of experiment technique. With respect to CCD and three different weight percentages of Talc (0, 15, 30 wt%), POE (0, 10, 20 wt%), and PPMA (0, 2.5, 5 wt%), 17 experiments were designed and prepared via a conventional melt blending technique. Analysis of variance (ANOVA) with diagnostic figures has been proposed to derive mathematical models to predict the mechanical properties of the utilised PP based composite. The findings showed that the concentration of POE, particularly at a lower amount, play a significant role and can predominantly affect the properties of the composites. The results also revealed that in spite of Talc and PPMA, adding of POE caused a noticeable rise in ductility and toughness of composite and a reduction in the stiffness. It was also found that all the assessed properties can be maximized simultaneously, providing the content of Talc, POE, and PPMA set to be 30%, 6.228%, and 2.514%, respectively. The findings are found to be aligned with the scanning electron microscopy micrographs and the DSC analysis data.

Recycled poly(lactic acid)–based 3D printed sustainable biocomposites: a comparative study with injection molding

With the objective of giving a new economic life to postindustrial waste poly(lactic acid) (PLA), biocomposites based on recycled PLA were manufactured using conventional melt blending, and the strands produced were successfully used for three-dimensional (3D) printing of American Society for Testing and Materials (ASTM) samples by means of the fused deposition molding (FDM) method. This article further discusses the processing advantages and challenges associated with void formation, anisotropic behavior, and the quality of the 3D printed (3DP) samples in comparison with injection-molded (IM) counterparts. The blends were manufactured containing 30 wt % of recycled PLA in a matrix of virgin PLA. Similarly, blends were also prepared with addition of an epoxy-based chain extender (CE) and as well as with the CE and a reinforcing phase of microcrystalline cellulose (MCC). One of the limitations of recycled PLA in FDM-based 3D printing is its high melt flow due to the reduced molecular weight after recycling, which results in excessive material flow during extrusion, and hence limits its application in FDM-based 3D printing. Consequently, the main effect of the CE, Joncryl, was to control the Melt Flow Index (MFI) of the biocomposites containing the recycled PLA. The addition of CE also resulted in improvement of the impact strength of 3DP samples. In general, the CE in combination with the natural fibers (MCC) allowed the incorporation of postindustrial PLA. Data suggest that more recycled PLA may be incorporated by using this blend combination. In general, owing to the void formation, 3DP samples presented lower values of density (lightweight) and mechanical properties as compared with IM samples. However, the tensile strength, modulus and Izod impact strength of 3DP biocomposites were increased by up to 88%, 127%, and 11%, respectively, by the addition of 5 wt % MCC, as compared with 3DP samples based on postindustrial PLA without additives.

An improved technique for dispersion of natural graphite particles in thermoplastic polyurethane by sub-critical gas-assisted processing

Dispersing fillers uniformly is the main technological challenge when considering nanocomposites. In this paper, a novel and efficient sub-critical gas-assisted processing (SGAP) technique is explored—an environmentally benign process that utilizes compressed CO2 to help effectively disperse aggregated natural graphite particles (NGPs) (3 wt%) in a thermoplastic polyurethane (TPU) matrix. A twin-screw extruder (TSE) equipped with a simple CO2 injection unit consisting of a standard gas cylinder, regulator, valve, and metal hose is employed for the melt mixing. Results from the structural, thermal, rheological, mechanical, microcellular injection molding, dielectric, and thermal conductive properties of the SGAP pellets, in addition to the resultant TPU/NGP nanocomposites, confirmed significantly improved dispersion compared to those obtained via conventional melt blending in the TSE. This technique offers a simple, cost-effective approach to the large-scale production of high-performance polymer nanocomposites without the requirement for complicated processing steps such as supercritical fluid (SCF) processes or chemical treatments.

Silanized silica compatibilization of NBR/gelatin blends for the production of green rubber products

In this study, acrylonitrile butadiene rubber (NBR)–gelatin blends were prepared by conventional melt blending process at 40°C processing temperature and 50 r min−1rotor speed in a Brabender-Plasticorder. Gelatin loading was varied from 10 to 50 phr. The extent of reinforcement was more prominent at 30 phr gelatin loading without compatibilization. Up to 30 phr gelatin loading, the tensile strength, abrasion resistance, and morphological properties of blends increased. After 30 phr gelatin loading, the toughness and abrasion resistance declined for samples containing 40 and 50 phr gelatin. However, cross-link density and hardness kept on increasing beyond 30 phr loading. At optimum loading of 30 phr of gelatin, 3, 3.5, and 4 phr of nano-silanized silica was added as a compatibilizer for further improvement in properties. After compatibilization of 30 phr gelatin sample with 4 phr of nano-silanized silica, the extent of reinforcement in terms of tensile strength was improved from 8.97 to 9.92 MPa.

Morphology of polycaprolactone/needle-shaped hydroxyapatite (PCL/HAN) nanocomposite blends using ultrasound assisted melt blending

Polycaprolactone/Hydroxyapatite (PCL/HA) composite is an excellent material for fabricating tissue engineering scaffolds, especially as bone scaffolds. However, polarity differences between the hydrophilic HA and the hydrophobic PCL often leads to poor dispersion during the blending process. This is due to the tendency of the HA particles to agglomerate, and the difficulty to efficiently mix the polymer melt at high loading. The objective of this study is to introduce ultrasound waves during the conventional melt blending to overcome the problem. PCL and needle-shaped hydroxyapatite (HAN) were blended using an ultrasonically assisted extruder. The morphology of the PCL/HAN blend was investigated using field emission scanning electron microscopy (FESEM). This study found that the presence of ultrasound waves during melt blending was helpful in breaking up the HAN agglomerates. Thus, better dispersion of HAN was obtained, although some small agglomerates of HAN were still observed.

Enhanced dispersion of nanoclays in poly(ethylene terephthalate)/clay nanocomposites using supercritical carbon dioxide

Nanoclays were prepared using supercritical carbon dioxide (scCO2) as a medium, and then blended with polyethylene terephthalate (PET) via conventional melt blending processing. The structure and morphology of nanoclays were investigated using wide‐angle X‐ray diffraction (WAXD) and scanning electron microscopy (SEM). It was found that, compared with the original organically modified layer silicates, smaller nanoclay tactoids and individual platelets morphology could be obtained after they were processed by scCO2, indicating scCO2 processing could enhance exfoliation of nanoclays. WAXD and transmission electron microscopy measurements were used to evaluate the dispersion of nanoclays in the nanocomposites. The results indicated the conventional blending extrusion processing could help to improve the dispersion of nanoclays, and the nanocomposites containing scCO2 pretreated nanoclays formed a looser clay stack and an improved intercalation structure, compared with those containing as‐received nanoclays. Thermal and mechanical properties of the nanocomposites were also studied by differential scanning calorimetry (DSC) and dynamic mechanical analysis, and the results showed that crystallization rate, crystallinity, and storage modulus of the well‐dispersed nanocomposites containing scCO2 pretreated nanoclays were increased, compared with the neat PET and nanocomposites containing as‐received nanoclays or nanoclays prepared by conventional organomodification process in water. J. VINYL ADDIT. TECHNOL., 23:E58–E67, 2017. © 2016 Society of Plastics Engineers

Enhanced dielectric properties of polyamide 11/multi‐walled carbon nanotubes composites

ABSTRACTComposites with multi‐walled carbon nanotubes (MWNTs) involved in polyamide 11 (PA11) were prepared via a conventional melt blending method. The structure, morphology, crystallization behavior, electrical, and dielectric properties of composites were investigated. The results demonstrated that the dispersed uniformly MWNTs favored the formation of α crystal of PA11 when the composites were quenched from melt. The dielectric constant of composites was dependent on the electric field frequency and MWNTs content, and the highest value of dielectric constant was as high as 350 for the composite with 1.21 vol % MWNTs at 103 Hz, accompanied by a low dielectric loss. The enhanced dielectric properties could be interpreted by the formation of abundant nanocapacitors within the composites and the interfacial polarization effect resulting from accumulation of charge carriers at the internal interfaces between MWNTs and PA11. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 42642.

Development of novel melt-processable biopolymer nanocomposites based on poly(l-lactic acid) and WS2 inorganic nanotubes

The use of tungsten disulphide inorganic nanotubes (INT-WS2) offers the opportunity to produce novel and advanced biopolymer-based nanocomposite materials with excellent nanoparticle dispersion without the need for modifiers or surfactants via conventional melt blending. The study of the non-isothermal melt-crystallization kinetics provides a clear picture of the transformation of poly(L-lactic acid) (PLLA) molecules from the non-ordered to the ordered state. The overall crystallization rate, final crystallinity and subsequent melting behaviour of PLLA were controlled by both the incorporation of INT-WS2 and the variation of the cooling rate. In particular, it was shown that INT-WS2 exhibits much more prominent nucleation activity on the crystallization of PLLA than other specific nucleating agents or nano-sized fillers. These features may be advantageous for the enhancement of mechanical properties and processability of PLLA-based materials. PLLA/INT-WS2 nanocomposites can be employed as low cost biodegradable materials for many eco-friendly and medical applications, and the exceptional crystallization behaviour observed opens new perspectives for scale-up and broader applications.

The Crystallinity Behavior of Polyethylene/Clay Nanocomposites Under the Influence of Water-Assisted Melt Blending

High-density polyethylene (HDPE)/clay nanocomposites were prepared via water-assisted and conventional melt blending. The influence of exfoliated/intercalated domains on crystallinity of nanocomposites was then investigated. X-ray diffraction and electron microscopy evidenced for enhanced intercalation and partial exfoliation of clay platelets pursuing rheological measurements. The methane permeability of water-injected nanocomposites was lower compared to melt-blended specimens implying the influence of intercalated domains. A theoretical/experimental analysis was performed to roughly determine the lamellar thickness distribution of the crystalline regions. Contribution of clay platelets to crystallization mechanisms was indicative of clay impact as heterogeneous nucleating agent, whereas mechanical properties were dependent on interface situation.

Significant reinforcement of poly(propylene carbonate): Nanostructured polymer composites of poly(propylene carbonate)/poly(methyl methacrylate) via a supercritical carbon dioxide route

Biodegradable poly(propylene carbonate) (PPC) matrix composite with a significant improvement in yield strength was successfully prepared by incorporating a low content of poly(methyl methacrylate) (PMMA) via a supercritical carbon dioxide route. Atomic force microscopy measurement shows that the size of the dispersed PMMA phase in the PPC substrate is in the range from 50nm to 200nm, which is much smaller than the smallest ones that can be obtained by conventional melt blending method. Tensile tests demonstrate the excellent mechanical properties of the composites prepared in this study. By incorporating only 5wt% PMMA, the obtained composites show approximately 4 times higher yield strength than pure PPC and the elongation at break of the composites is well remained. By comparing with the reported works, this method shows the highest enhancement efficiency of PPC. The significant reinforcement of PPC is ascribed to the nano size phase-separated domains of rigid PMMA. These findings show an effective modification method of PPC for the potential alternative to the non-biodegradable polymers.

Conductivity of microfibrillar polymer-polymer composites with CNT-loaded microfibrils or compatibilizer: A comparative study

Conductive polymer composites have wide ranging applications, but when they are produced by conventional melt blending, high conductive filler loadings are normally required, hindering their processability and reducing mechani- cal properties. In this study, two types of polymer-polymer composites were studied: i) microfibrillar composites (MFC) of polypropylene (PP) and 5 wt% carbon nanotube (CNT) loaded poly(butylene terephthalate) (PBT) as reinforcement, and ii) maleic anhydride-grafted polypropylene (PP-g-MA) compatibilizer, loaded with 5 wt% CNTs introduced into an MFC of PP and poly(ethylene terephthalate) (PET) in concentrations of 5 and 10 wt%. For the compatibilized composite type, PP and PET were melt-blended, cold-drawn and pelletized, followed by dry-mixing with PP-g-MA/CNT, re-extrusion at 200°C, and cold-drawing. The drawn blends produced were compression moulded to produce sheets with MFC structure. Using scanning electron microscopy, CNTs coated with PP-g-MA could be observed at the interface between PP matrix and PET microfibrils in the compatibilized blends. The volume resistivities tested by four-point test method were: 2.87·10 8 and 9.93·10 7 !·cm for the 66.5/28.5/5 and 63/27/10 (by wt%) PP/PET/(PP-g-MA/CNT) blends, corresponding to total CNT loadings (in the composites) of 0.07 vol% (0.24 wt%) and 0.14 vol% (0.46 wt%), respectively. For the non-compatibilized MFC types based on PP/(PBT/CNT) with higher and lower melt flow grades of PP, the resistivities of 70/(95/5) blends were 1.9·10 6 and 1.5·10 7 !·cm, respectively, corresponding to a total filler loading (in the composite) of 0.44 vol% (1.5 wt%) in both MFCs.

Preparation and characteristic of magnetic LDPE/Fe3O4 nano-composite films

Magnetic LDPE/Fe3O4 composite films have been successfully prepared using conventional melt blending technique in a sigma internal mixer. The magnetic Fe3O4 nanoparticles using in compositing were perpared by chemical co-precipitation method and characterized by TEM, XRD, FTIR and their magnetism was analyzed by VSM. The LDPE/Fe3O4 composite films were measured with SEM, XRD, FTIR and VSM. The magnetic measurement showed that both the Fe3O4 nanoparticles and the composite films made through doping of Fe3O4 nanoparticles in original LDPE displayed a super-paramagnetic property. And other results showed that the composite films were dispersed homogeneously and the structure of original LDPE were not destroyed with the doping of Fe3O4 nanoparticles.