iPP Matrix Research Articles

A nonequilibrium constitutive equation for tensile behavior of polyolefinic thermoplastic vulcanizates

Polyolefinic thermoplastic vulcanizates (TPVs) composed of iPP (isotactic polypropylene) and crosslinked EPDM (ethylene-propylene-diene rubber) prepared by dynamic vulcanization process exhibit rubber domains dispersed in the iPP matrix, even though the EPDM component is the major component. Here we proposed a kinetic nonequilibrium constitutive equation that considers the transition of the mechanical nature from plasto-rigid deformation to rubbery deformation during uniaxial extension to explore the origin of the thermoplastic elastomer behavior of TPV (thermoplastic vulcanizate) materials. Fitting of the constitutive equation to the experimental stress‒strain curves quantitatively revealed the critical transition point of the mechanical properties. The transition shifted to higher strains with decreasing EPDM content. In situ wide-angle X-ray diffraction profiles monitored during the uniaxial extension confirmed the mechanical transition process.

Isothermal crystallization of polyethylene droplets within the self-nucleated isotactic polypropylene matrix of a 70/30 iPP/PE immiscible blend via fast scanning chip calorimetry (FSC)

The escalating volume of waste related to polyolefins poses recycling challenges. Given the mixed composition of the post-consumer feedstock, studying blends of virgin polyolefins is a fruitful strategy to simulate such compositions. For the first time, this study investigates crystallization, self-nucleation (SN), and kinetics of a 70/30 iPP/PE blend, characterised by a "sea-island" morphology, using fast scanning calorimetry (FSC). Preliminary experiments on different chip sensors proved the technique's sensitivity and representativeness for polymer blends, even with minimal sample quantities. Application of the self-nucleation thermal protocol (employing fast scanning rates, from 500 to 1000 °C/s) to the iPP matrix phase revealed insights into the characteristic SN domains. The crystallization kinetics of PE-dispersed droplets within a SN iPP matrix was also investigated. Results indicate a 30 °C crystallization window for PE droplets within the self-nucleated iPP matrix, expanding the understanding of crystallization rates (up to four decades) compared to standard DSC measurements.

Effects of process conditions and nano-fillers on the cell structure and mechanical properties of co-injection molded polypropylene-polyethylene composites

Compared with traditional injection foaming, co-injection foaming serves as a method to prepare products with high-quality surfaces and enhanced mechanical properties, demonstrating excellent technical advantages and economic benefits. The effects of high-density polyethylene (HDPE) content, foaming agent content, melting temperature of core material, and nano-organic montmorillonite (OMMT) content on the cell structure, mechanical properties, and crystallization behavior of isotactic polypropylene (iPP)/HDPE composite foam prepared by co-injection foaming were systematically studied. At a foaming agent content of 2 wt.%, HDPE content of 30 wt.%, OMMT content of 3 wt.%, and the melting temperature of core material of 190 °C, the composite foam exhibited a cell size measuring 85 μm, a cell density of 2.5 × 105 cells/cm3, a tensile strength of 25.8 MPa, and an impact strength of 12.5 kJ/m2. The addition of HDPE reduced the crystallinity of iPP matrix, while enhancing the solubility of carbon dioxide within the matrix. The non-miscible interface between HDPE and iPP helped reduce the energy barrier for cell nucleation. Furthermore, the introduction of OMMT as a nucleating agent in iPP/HDPE composite material dramatically decreased the energy barrier for cell nucleation. These synergistic effects result in foam with the smaller cell size and the higher cell density, exhibiting excellent comprehensive mechanical properties. This work provides a feasible method for preparing composite foam with excellent comprehensive performance.

Fused Deposition Modeling of Isotactic Polypropylene/Graphene Nanoplatelets Composites: Achieving Enhanced Thermal Conductivity through Filler Orientation.

High-performance thermally conductive composites are increasingly vital due to the accelerated advancements in communication and electronics, driving the demand for efficient thermal management in electronic packaging, light-emitting diodes (LEDs), and energy storage applications. Controlling the orderly arrangement of fillers within a polymer matrix is acknowledged as an essential strategy for developing thermal conductive composites. In this study, isotactic polypropylene/GNP (iPP/GNP) composite filament tailored for fused deposition modeling (FDM) was achieved by combining ball milling with melt extrusion processing. The rheological properties of the composites were thoroughly studied. The shear field and pressure field distributions during the FDM extrusion process were simulated and examined using Polyflow, focusing on the influence of the 3D printing processing flow field on the orientation of GNP within the iPP matrix. Exploiting the unique capabilities of FDM and through strategic printing path design, thermally conductive composites with GNPs oriented in the through-plane direction were 3D printed. At a GNP content of 5 wt%, the as-printed sample demonstrated a thermal conductivity of 0.64 W/m · K, which was 1.5 times the in-plane thermal conductivity for 0.42 W/m · K and triple pure iPP for 0.22 W/m · K. Effective medium theory (EMT) model fitting results indicated a significantly reduced interface thermal resistance in the through-plane direction compared to the in-plane direction. This work shed brilliant light on developing PP-based thermal conductive composites with arbitrarily-customized structures.

Necessity of interfacial interaction on toughness improvement for iPP/mSEBS blends

Isotactic polypropylene (iPP) is a thermoplastic polymer, however, its use as an engineering plastic has been limited because of its poor impact toughness, and for improving that, appropriate elastomers are usually added to modify its toughness. In the present work, maleic anhydride grafted styrene-b-(ethylene-co-butylene)-b-styrene triblock copolymer (mSEBS) has been blended with iPP for investigating the interfacial effect on the toughness improvement. A normal mSEBS sample has been chosen to use to compare with an aged one (over nine-year aging time) for this comparison purpose. Our study shows that the aged one (as a type of waste) does not function well to toughen the iPP, whereas the normal one with no ageing functions well to improve the toughness of iPP blend. It is further disclosed that the interfacial interaction between mSEBS particles and iPP matrix plays a key role for this effect.

Study of Mechanical, Thermal, and Microstructural Properties of Polypropylene/Ceramic Waste Composites

In this work, the effect of reinforcement of the iPP with ceramic waste (CW), and the use of maleic anhydride compatibilizing agent grafted with polyolefin elastomer (POE-g-MAH) are studied. The composites were fabricated by extrusion and injection processes, and their morphology and microstructure, as well as fracture surface and mechanical and thermal properties were analyzed. Characterization by polarized optical microscopy showed that the ceramic waste particles were well-dispersed into the iPP matrix without the presence of agglomerates. However, the POE-g-MAH did not show good compatibility when it was added to the iPP/CW composite. Hardness Rockwell R, tensile and flexural measurements showed that the hardness, Young´s modulus, and flexural modulus increased with the incorporation of CW and without the POE-g-MAH. The ductility of the composites was several decreased with the addition of CW. POE-g-MAH affected the hardness, ductility, strength tensile, Young´s modulus, flexural modulus, and interfacial interaction in the iPP/CW composite. Analysis by X-ray diffraction showed that the CW also acted as a nucleating agent, increasing the crystallization degree, and forming the β-phase. Analysis of the Fourier transformed infrared showed transmittance bands of the iPP, CW, POE-g-MAH and composites. The bands were similar and there were no major changes in characteristic bands of composites, but CW and POE-g-MAH produced changes in the shape and intensity of band peaks of the iPP matrix. The CW addition to the iPP matrix modified the thermal properties of pure iPP, such as the degree of crystallization and melting temperature in the iPP/CW composites. The incorporation of POE-g-MAH decreased the crystallization temperature and crystallinity degree in the iPP/CW composite.

Induction of the β-phase in isotactic polypropylene with pimelic acid modified graphene nanoplatelets

In this work, graphene nanoplatelets (GnPs) were oxidized to functionalize them with molecules of pimelic acid (PA). This fact was confirmed by the presence of two characteristic bands assigned to CH bonds of the aliphatic chains of the pimelic acid (2939 cm−1 and 2860 cm−1). Furthermore, the IR spectra show two vibration bands about 1575–1570 cm−1 and 1413–1410 cm−1, which could be attributed to an ionic bridging linkage between the oxygenated sites of the oGnPs and the organic molecules. The chemical modification was followed by XRD and RAMAN, where an increase in the D/G ratio would suggest a major disorder in the structure because of the attaching in the first instance of oxygen and the pimelic acid during the functionalization. The modified ones were added at different percentages of 0.05, 0.5, and 1 wt% into an iPP matrix to demonstrate the β nucleating ability of our nanofiller. The relative percentages of the β-crystal for all samples were determined by DSC and WAXD, 72% and 75% for the oGnP and 0.05%-PA, respectively. DMA measurements were carried out to follow the influence of the reinforcements on the visco- elastic properties of the iPP matrix. The results showed an increase in the storage modulus of 161.2% at −40 °C and an improvement in the loss modulus of 54.2% for the composite with 1 wt% of the modified ones. The impact strength for this nanocomposite was 39% higher than the raw iPP.

Polystyrene: A Self-Dispersing, Ultralow Loading Additive for Improving the Breakdown Strength of Polypropylene for High Voltage Power Cable Applications

Voltage stabilizers (VSs) with benzene derivatives have received great interest as high-performance additives for improving the electrical durability of polypropylene (PP)-based insulation materials for high voltage (HV) power cable applications. In this work, atactic polystyrene (aPS) was first used as a thermoplastic VS (TVS) to efficiently dope the benzene units into isotactic PP (iPP). The aPS TVS was incorporated in the iPP matrix through melt-mixing, and the domain size of immiscible aPS decreased with the decrease of aPS content. The smaller amount of aPS doping increased the direct current (DC) breakdown strength (BDS) of iPP, even at ultralow loading levels below 0.01 phr. The enhancement ratio of the BDS value of iPP with 0.001 phr of aPS was higher compared to the results obtained for other types of additives reported in the previous literature.

Reversible nucleation behavior of N, N′-dicyclohexylterephthalamide to polypropylene with the aid of polyamide 12

Through the hydrogen bonding between polyamide 12 (PA12) and N, N′-dicyclohexylterephthalamide (DCHT) nucleator, the intentionally controlled self-assembly of DCHT and the crystallization behavior of isotactic polypropylene (iPP) matrix are investigated. The introduction of PA12 could severely postpone the condensation of DCHT vapor in iPP matrix due to the reduced vapor concentration. As a result, the nucleating efficiency of DCHT at lower concentration for example iPP/PA12/0.05DCHT even failed at a relatively higher final heating temperature Tf. Such a failure of nucleating efficiency could be recoverable after a step-cycle treatment at lower Tf, where the sublimation of DCHT can hardly occur. The changes from a cluster-like structure to a network structure driven by hydrogen bonding between DCHT and PA12 could be a reason of nucleation failure and recovery. This means that the nucleating efficiency of DCHT and crystallization of iPP could be tuned by controlling the absorption and release of DCHT vapor at the surface of PA12 particles. For iPP/PA12/0.5DCHT with a higher concentration of DCHT, the absorption of PA12 could only reduce the DCHT vapor concentration in the iPP melt and thus, the dendrite structure of DCHT shows more and thinner branches, which results in better nucleating efficiency of DCHT than that in iPP/0.5DCHT.

Synergy of Fiber Surface Chemistry and Flow: Multi-Phase Transcrystallization in Fiber-Reinforced Thermoplastics.

Fiber-reinforced polymer composites are largely employed for their improved strength with respect to unfilled matrices. Considering semi-crystalline materials under relevant processing conditions, the applied pressure and flow induce shear stresses at the fiber-polymer interface. These stresses may strongly enhance the nucleation ability of the fiber surface with respect to the quiescent case. It is thus possible to assume that the fiber features are no longer of importance and that crystallization is dominated by the effect of flow. However, by making use of an advanced experimental technique, i.e., polarization-modulated synchrotron infrared microspectroscopy (PM-SIRMS), we are able to show that the opposite is true for the industrially relevant case of isotactic polypropylene (iPP). With PM-SIRMS, the local chain orientation is measured with micron-size spatial resolution. This orientation can be related to the polymer nucleation density along the fiber surface. For various combinations of an iPP matrix and fiber, the degree of orientation in the cylindrical layer that develops during flow correlates well with the differences in nucleation density found in quiescent conditions. This result shows that the morphological development during processing of polymer composites is not solely determined by the flow field, nor by the nucleating ability of the fiber surface alone, but rather by a synergistic combination of the two. In addition, using finite element modeling, it is demonstrated that, under the experimentally applied flow conditions, the interphase structure formation is mostly dominated by the rheological characteristics of the material rather than perturbations in experimental conditions, such as shear rate, layer thickness, and temperature. This once again highlights the importance of matrix-filler interplay during flow and, thus, of material selection in the design of hybrid and lightweight composite technologies.

3D printing of a composite iPP/quill of chicken feathers functionalized with pimelic acid

AbstractIn this work, the thermomechanical properties of an isotactic polypropylene (iPP)/quill composite were evaluated. This reinforcement was added at 0.5, 1.0 and 5.0 wt% in the iPP matrix. The reinforcement was previously subjected to alkaline treatment with NaOH (QT) and chemical functionalization with pimelic acid (PA) to produce an effective β‐crystal nucleating agent. This functionalization was characterized by Fourier transform infrared spectroscopy (FTIR), showing the presence of a new band at 1571 cm−1 associated with the carboxylate group of pimelic acid, indicating a bond between PA and the quill surface. The internal geometry of the specimens obtained by 3D printing were studied by scanning electron spectroscopy (SEM). The effectiveness of the modified reinforcement as a promoter of the β‐crystalline phase was evaluated by differential scanning calorimetry (DSC) and wide angle X‐ray scattering (WAXD) under non‐isothermal crystallization conditions due to the 3D printing process. The composite that showed a higher index was 1.0% with a value of 64% by DSC and 65% by WAXD. Furthermore, the thermomechanical properties were characterized by dynamic mechanical analysis (DMA) where, for the 0.5% and 1.0% composites, the storage modulus (E') was higher compared to neat iPP. However, for the 5.0% composite the E' values were lower.

Microcellular foaming and mechanical properties of iPP-iPPF using supercritical CO2

Isotactic polypropylene (iPP) is one of the most widely used commercial polymers in the industry. However, it is difficult to foam iPP due to its low melt strength. In this work, the foamability and mechanical properties of iPP were investigated by incorporating isotactic polypropylene fiber (iPPF), using a batch foaming method. Compared to the neat iPP foams, smaller cell size and more uniform cell size distribution were obtained for iPP–iPPF. When 30 % iPPF was added, the cell density of iPP-iPPF foam was 1.1 × 1010 cells/cm3 which was twice that of the neat iPP foam. It was attributed to the improved melt strength and heterogeneous nucleation of iPPF in the iPP matrix. In addition, the impact strength of foamed iPP-30iPPF was found to be increased by 136 % compared to its neat iPP counterpart. Furthermore, the tensile strength of the foamed samples also increased with the increasing iPPF content.

Crystallization kinetics of melt-mixed 3D hierarchical graphene/polypropylene nanocomposites at processing-relevant cooling rates

Knowledge of the solidification behaviour of isotactic polypropylene (iPP) composites with reduced graphene oxide nanoplatelets is key to open the possibility to widespread use of these high performing nanocomposites. The crystallization behaviour of these systems, with filler content in the range of 0.2–3.5 wt% has been investigated by differential scanning calorimetry (up to 100 °C/min) and ex-situ structural and morphological characterization of samples prepared at processing-relevant cooling conditions (up to 2000 °C/s). Compared to the self-nucleated neat iPP, the nucleation efficiency was estimated to vary from 44 to 93% when increasing the filler content. Such a high nucleating efficiency has not been reported yet for a nanocomposite with iPP matrix. This result is due to the very good dispersion of the filler in these melt-mixed graphene-based polypropylene systems. The nucleation ability of the graphene filler does not reach a saturation in the concentration range studied. The gap between laboratory and industrial cooling rate scale is here reduced thanks to the information achieved from the fast-cooling experiments. By varying the filler amount in the investigated range, a significant shift of the cooling rate window in which the transition from α-to mesophase dominated crystallization takes place was detected. Notably, with 3.5 wt% graphene platelets, α-phase crystals are predominantly present in the material even after quenching at 1000 °C/s, similar to highly nucleated commercial iPP grades.

The Influence of Metal Lithium and Alkyl Chain in the Nucleating Agent Lauroyloxy-Substituted Aryl Aluminum Phosphate on the Crystallization and Optical Properties for iPP

In this work, a kind of aryl phosphate salt nucleating agent (APAl-12C) was synthesized, which was replaced in the hydroxyl group on the aluminum hydroxy bis [2,2′-methylene-bis(4,6-di-tert-butylphenyl) phosphate] (APAl-OH) by lauroyloxy, which could improve the dispersion between the nucleating agent and the iPP matrix and reduce the migration potential of the nucleating agent in the iPP matrix by increasing the molecular weight. The structure of the nucleating agent APAl-12C was analyzed by fourier infrared spectroscopy (FT-IR ) and 1H NMR. The differential scanning calorimeter (DSC) results indicated that the addition of APAl-OH or APAl-12C alone was inferior to the commercial nucleating agent NA-21 (compounds of APAl-OH and Lithium laurate) in terms of the crystallization behavior, which may be due to the importance of metal Li in the crystallization property. Thus, the iPP/A12C-Li composites were prepared with APAl-12C, lithium laurate (lilaurate) and the iPP matrix. The crystallization behavior, morphology, optical and mechanical properties for the iPP/A12C-Li composites were systematically studied and compared with that of the iPP/NA-21 composite. Among the iPP/A12C-Li composites with the addition of 0.5 wt%, APAl-12C/Lilaurate had the fastest crystallization rate and reduced the haze value of the neat iPP from 36.03% to 9.89% without changing the clarity, which was better than that of the iPP/NA-21 composite. This was due to the weakening of the polarity of the APAl-12C after lauroyloxy substitution and better dispersion in the iPP matrix, resulting in a significant improvement in the optical properties.

A ternary hybrid nucleating agent for isotropic polypropylene: Preparation, characterization, and application

Abstract A ternary hybrid nucleating agent (THNA) powder was prepared by co-spray drying the fluid mixture of Si-MP/SNa slurry. The THNA was characterized by Fourier transform infrared and thermogravimetric analyses; the results showed that THNA was prepared successfully. The results of scanning electron microscopy (SEM) and transmission electron microscopy (TEM) showed that THNA was ring-shaped or mushroom cap-shaped and it was uniformly dispersed in the iPP matrix. With the incorporation of THNA (0.2 wt%), the crystallization peak temperature of iPP/THNA increased effectively. The nucleation efficiency and crystallinity were improved to 69% and 58%, respectively. Moreover, the flexural strength, flexural modulus, tensile strength, and impact toughness of iPP/THAN were enhanced to 49.3 MPa, 1,988 MPa, 42 MPa, and 4.93 kJ·m−2, respectively. The transparency was increased to 77.7%, and the haze was reduced to 14.1%. The compound of sodium laurate and inorganic silica/aromatic phosphate had an obvious synergistic effect.

Physical Properties of Isotactic Polypropylene Blended with Less Crystalline Polypropylene

AbstractThe physical properties of polymeric materials, which are mixtures of various molecules, are determined by the sum of their contributions. Industrially important isotactic polypropylene (iPP), which is produced using heterogeneous Ziegler–Natta catalysts, shows broader distributions of molecular weight and stereoregularity because of the multisite nature, compared to molecular catalysts. However, systematic studies on the effects of these distributions on physical properties are lacking, especially for variations in stereoregularity. In this study, polypropylene (PP) additives with various molecular weights and stereoregularities (and their distributions) are added to an iPP matrix to clarify the effects of low‐concentration components on the overall physical properties. The results indicate the importance of incorporating the PP additives into the crystal structure of the iPP matrix.

Engineered PP impact copolymers in a single reactor as efficient method for determining their structure and properties

Impact polypropylene (PP) copolymers (IPCs) are important materials for many commercial applications. These materials are usually synthetized through different methods involving two consecutive reactions in the same phase or in different phases. Here, a laboratory-scale synthesis method based on a sequential liquid- and gas-phase two-step process in a single reactor is developed. Propylene homopolymers and IPCs were synthesized with varying amounts of comonomers and hydrogen. The IPC materials obtained were fully characterized via analytical temperature rising elution fractionation (TREF), differential scanning calorimetry (DSC), 13C nuclear magnetic resonance (13C NMR), gel permeation chromatography with an infrared detector (GPC-IR5), Charpy impact, scanning electron microscopy (SEM), and cross-fractionation chromatography (CFC). The addition of only ethylene to the second step in the absence of hydrogen led to the creation of an ethylene-propylene (EP) copolymer with similar impact strength to that of a propylene homopolymer. The addition of hydrogen to the first step dramatically shortened the length of the PP chains and inhibited catalytic active centers that led to EP copolymer synthesis. This material exhibited very low molecular weight, low ethylene incorporation, and rubbery phases irregularly distributed along the isotactic polypropylene (iPP) matrix, resulting in the formation of an EP copolymer material with poor impact properties. IPCs synthesized without hydrogen and with a 50/50 (v/v) mixture of propylene/ethylene monomers in the second step enhance ethylene incorporation, facilitating adequate homogeneous and heterogeneous ethylene distribution and resulting in a high increment of amorphous ethylene-propylene-rubber (EPR) domains, which remarkably improves impact properties. Additionally, a criterion based on the ratio between EEE and EPE + PEP triads ranging between 1 and 2 was also established to predict the impact resistance of any heterophasic PP. Fractionation of the optimal sample provided a detailed understanding about the microstructure of this copolymer through the study of the molecular weight and composition of the fractions via GPC-IR, analytical TREF, and DSC measurements. Finally, the liquid–gas-phase two-step IPC material was compared, by means of SEM and CFC measurements, with synthesized IPC using liquid–liquid-phase two-step polymerization, and the results showed that the range of EP composition as well as ethylene distribution in the molar mass molecules of the IPCs was correlated to their mechanical behavior. This proves that crystalline families composed of high-molecular-weight EP copolymers in the liquid–gas-phase process can act as a compatibilizing agent between the iPP matrix and the elastomeric rubbery phase, allowing one to improve the impact resistance of the IPC, more so than that of IPCs obtained in the gas–gas and liquid–liquid phases. The results indicate that the synthesis of IPC resins in a single reactor is an efficient experimental method for fundamental research on IPCs.

Effects of crystal planes of ZnO nanocrystal on crystalline, thermal and thermal-oxidation stability of iPP

The nanocrystalline with different crystal planes often displayed diverse physical and chemical properties. However, the effects of crystal planes of inorganic nano-particle have been few focused on. Here, two kinds of nano-crystal ZnO with different crystal planes were used to explore their effect on the crystallization nucleation, crystal morphologies, thermal and thermal-oxidation stability of iPP. The results shown that the (1010) and (0002) planes possessed different effects for iPP. The (1010) planes with non-polar and low surface energy has highly nucleating effective for iPP, the crystallization temperature increased by 11 °C, the size of spherulites decreased, the number of spherulites increased, the nucleation efficiency and crystallization rate up to 57.81% and 1.27 min−1, the thermal and thermal oxidation stability (TG, OIT, OOT) of iPP improved by 6 °C, 6 min and 12 °C. In contrast, the (0002) planes with polar and high surface energy have no effect for iPP. Our research results indicate that the wettability and interface compatibility between crystal planes and iPP matrix, which was caused by the polarity and surface energy of (1010) or (0002) planes played key role in improving the performance of polymers.

Enhancement of crystallization and mechanical properties in isotactic polypropylene via adding liquid-phase exfoliated graphene

In this work, liquid-phase exfoliated graphene (G) was introduced into isotactic polypropylene (iPP) via melt blending. Wide-angle X-ray diffraction measurements revealed that liquid-phase exfoliated graphene is a strong α-nucleating agent, making the iPP crystal grow preferentially on the (040) crystal plane. Differential scanning calorimetry and polarized optical microscopy results showed that the increase in both the nucleation density and crystal growth rate brings about the remarkable elevation of overall crystallization rate of iPP with the addition of liquid-phase exfoliated graphene. Moreover, remarkable enhancements in mechanical properties especially the toughness were obtained at low graphene loading. With the addition of 0.5 wt.% graphene, the impact strength and elongation at break of iPP increased by 103 % and 510 %, respectively. The significant enhancement of crystallization and mechanical properties of the composites could be attributed to favorable dispersion of liquid-phase exfoliated graphene in the iPP matrix. A possible toughening mechanism was proposed.

Well dispersion of poly(acrylonitrile‐butadiene‐styrene) in isotactic polypropylene mediated by incorporation of graphene and the elevated toughness

Polymers with benzene rings in structures including polystyrene (PS) and poly(acrylonitrile‐butadiene‐styrene) (ABS) could function as rigid organic particles and macromolecular β nucleating agents to toughen isotactic polypropylene (iPP), and the toughening effect mainly depends on their dispersibility in iPP matrix. In this work, a third component of graphene (G) was introduced into the iPP/PS and iPP/ABS blends, respectively, to mediate the dispersibility of these polymers in the iPP via melt blending. Selective dispersion of graphene in these immiscible blends has been investigated with SEM, DSC, and a rheometer. It was interesting to obtain a more favorable dispersion of ABS in the iPP/ABS/G blend compared with the iPP/ABS blend, and the corresponding toughness showed a prominent improvement accompanied with an elevation in rigidity. The underlying mechanism for the improved dispersion of ABS in the iPP/ABS/G blends has been discussed in detail. However, because of a better affinity of the graphene to the PS than the iPP matrix, graphene could only locate in the PS phase, resulting in poor compatibilization for the iPP/PS blend followed by the deterioration of mechanical properties.