Loss Factor Peak Research Articles

Physical origin of the second damping peak in ionomers as traced by enthalpy relaxation

Ionomers possess two loss factor peaks, thus providing a possibility for the fabrication of novel damping materials. Eisenberg et al. assigned the second damping peak to the glass transition of restricted regions in the ionic cluster. However, the ordinary heat flow curves showed only one glass transition corresponding to the first loss factor peak. Moreover, the conventional view by multiplet/cluster model has been questioned by Simmons due to their different conclusions on the size of restricted regions (Macromolecules 2015, 48, 2313−2323). Meanwhile, we found that the storage modulus of the second damping peak was right in the modulus range of the Rouse relaxation mode. In view of these confusions, enthalpy relaxation characteristics were investigated to clarify the nature of the second loss factor peak. It was found that all the ionomers possessed anomalous enthalpy hysteresis due to the existence of two different but partly coupled glass transitions, while Rouse motion did not cause anomalous enthalpy hysteresis. Furthermore, the heat capacity curves after physical aging clearly showed two glass transition behaviors. These experimental evidences confirmed that the second loss factor peak originated from the glass transition in cluster rather than Rouse relaxation, thus further validating the view by multiplet/cluster model.

Recycling Waste Nonmetallic Printed Circuit Boards for Polyvinyl Chloride Composites.

To reduce environmental threats, such as land filling, incineration and soil pollution, which are associated with the improper waste management of waste printed circuit boards, the utilization of NMPCBs from waste PCBs as a filler in composites was pursued. Untreated and treated NMPCBs in varying ratios, 10–30 wt.%, were blended with PVC to produce NMPCB/PVC composites, using the melt-mixing method via an internal mixer, in order to solve the remaining NMPCB waste problem after the valuable metals in PCBs were recovered. The incorporation of the NMPCB with PVC resulted in an increase in the tensile modulus and the thermal stability of the resulting composites. Scanning electron microscopy (SEM) results indicated improved interfacial adhesion between the treated NMPCB and the PVC matrix. The FTIR results of the NMPCB treated with 3-glycidyloxypropyltrimethoxysilane (GPTMS) revealed the formation of Si-O-Si bonds. The densities of the composites were found to increase with an increase in the content of the treated NMPCB, and compatibility improved. The tensile properties of the treated NMPCB/PVC composites were higher than those of the untreated NMPCB/PVC composites, suggesting improved compatibility between the treated NMPCB and PVC. The PVC composite with 10 wt.% of the treated NMPCB showed the optimum tensile properties. It was observed that the tensile modulus of the treated NMPCB/PVC composite increased by 47.65% when compared to that of the neat PVC. The maximum thermal degradation temperature was 27 °C higher than that of the neat PVC. Dynamic mechanical analysis results also support the improved interfacial adhesion as a result of the improvement in the storage modulus at the glassy region, and the loss factor (tan δ) peak shifted to a higher temperature range than that of the PVC and the untreated NMPCB/PVC composite. These studies reveal that the NMPCB was successfully modified with 1 wt.% of GPTMS, which promoted the dispersion and interfacial adhesion in the PVC matrix, resulting in better tensile properties and better thermal stability of the PVC composite.

Characterization of interwoven roselle/sisal fiber reinforced epoxy composites

AbstractThe present work deals with the characterization of interwoven roselle/sisal fiber fabric reinforced epoxy composites. All the composites are manufactured using the hand layup technique, and the physical (density), mechanical (tensile, flexural, and impact) and dynamic mechanical characteristics are determined as per ASTM standards. The findings reveal that roselle fabric composite has superior mechanical properties than interwoven roselle/sisal fabric composites. The tensile and impact strengths of the sisal fabric composite are lower than those of the roselle fabric composite. However, the roselle fabric composite and sisal fabric composite have similar flexural properties. The sisal fabric composite yields the highest peak value of the loss factor. The loss factor peak height for the roselle/sisal fabric composites increases with increased sisal fiber content. Morphological analysis revealed proof of yarn pullout and matrix damage near the yarn, indicating inadequate stress transfer between the fabric and epoxy. The property map is presented in comparison with available literature.

Graphene으로 개질된 폴리우레탄-에폭시 복합체의 기계적 물성과 Damping 특성

Polyurethane (PU) has received extensive attention in structural engineering due to its excellent mechanical properties and damping properties. In this research, graphene-modified PU-epoxy composites are prepared for the application in structural engineering. The mechanical properties and damping properties of the composites with different contents of graphene are investigated. The damping properties of the composites were also investigated by performing dynamic mechanical analysis (DMA). The results showed that with the increase of graphene content, the tear strength of the composites decreased from 52 to 39 ㎫. Due to the enhancement of appropriate amount of graphene, the tensile strength and elongation at break increase to the maximum value, being 16 ㎫ and 675%, respectively. And DMA tests showed that the damping properties reach the optimal values when the graphene content is 0.2%. The large damping temperature range (ΔT<SUB>0.5</SUB>) is 33 ℃, from -2.9 to 30.1 ℃. The peak of loss factor (η<SUB>max</SUB>) is 0.92 and the integral area (TA) is 36 ℃, much higher than those of the pure PU-epoxy composites. In addition, scanning electron microscopy (SEM) results show that agglomeration appears with higher graphene content.

Research on the viscous flow transition of styrene-isoprene-styrene triblock copolymer by Rheology

The viscous flow transition of triblock copolymer styrene-isoprene-styrene (SIS5562) was studied by rheological methods. A broad loss factor (tan $$\delta$$ ) peak at 152.5 ℃ appeared on the dynamic viscoelastic spectrum under experimental conditions. Some similar peaks had been attributed to order-order transition (OOT) or order-disorder transition (ODT) in some research. In this system, the SAXS, time-temperature superposition (TTS) and Han plots proved that the microstructure of the SIS5562 did not undergo OOT or ODT transition in the temperature range. It may be the viscous flow transition as we supposed previously. The rheology study by capillary and rotation rheometer verified that the viscous flow transition temperature (Tf) was around 150 ℃.

Comparison of Contemporary Elm (Ulmus spp.) and Degraded Archaeological Elm: The Use of Dynamic Mechanical Analysis Under Ambient Moisture Conditions.

This paper describes dynamic mechanical analysis (DMA) experiments on archaeological and contemporary elm tested under air-dry conditions, to explore the suitability of this technique for increasing understanding of the viscoelastic behaviour of archaeological wood. A strong reduction of storage modulus of archaeological elm (AE) was seen in comparison with contemporary wood (CE), resulting from the high degree of wood degradation, notably the reduction in hemicelluloses and cellulose content of AE, as demonstrated by Attenuated Total Reflection–Fourier Transform Infra-Red spectroscopy (ATR-FTIR). The γ relaxation peak was observed in all samples. The γ peak in AE shifted to a higher temperature, and the activation energy for γ-peak motions was lower in AE (29 kJ/mol) than in CE (50 kJ/mol) indicating that motion is less restricted within the degraded AE cell wall, or possibly a difference in the monomer undergoing rotation. Detection of changes in storage modulus are well known, but the DMA temperature scan technique proved to be useful for probing the degree of wood degradation, relating to the changes in location and intensity of secondary relaxation peaks. The γ peak in loss factor can be used to confirm that cell wall degradation is at an advanced stage, and to improve understanding of the internal spatial structure of the degraded wood cell wall.

Effect of Hindered Phenol AO‐80 on the Damping Properties for Nitrile‐Butadiene Rubber/Phenolic Resin: Molecular Simulation and Experimental Study

AbstractA combined study of molecular dynamics (MD) simulation, experimental, and linear regression analysis method is presented for hindered phenol of 3,9‐bis[1,1‐dimethyl‐2‐{b‐(3‐tertbutyl‐4‐hydroxy‐5‐methylphenyl)propionyloxy}ethyl]‐2,4,8,10‐tetraoxaspiro‐[5,5]‐undecane (AO‐80)/nitrile‐butadiene rubber/linear phenolic resin (AO‐80/NBR/PR) composites with different AO‐80 contents to quantitatively establish the relations between microstructure and damping performance. The number of hydrogen bonds (NHBs), the fractional free volume (FFV), and the binding energy (Ebinding) of AO‐80/NBR/PR composites with different AO‐80 content are calculated by MD simulation from the microscopic scale. Damping parameters, including the loss factor peak (tan δmax) and the loss peak area (TA) (tan δ &gt; 0.3), are obtained by dynamic mechanical analysis from macroscopic scale. The quantitative relationships between microstructure parameters (NHBs, Ebinding, and FFV) and macroscopic damping properties (tan δmax and TA) are obtained by linear regression analysis. This research is expected to provide a theoretical guidance for improving the damping performance of rubber‐based organic hybrid composites.

Effect of Graphene Oxide Modified with Organic Amine on the Aging Resistance, Rolling Loss and Wet-skid Resistance of Solution Polymerized Styrene-Butadiene Rubber.

Graphene oxide (GO) was modified by p-phenylenediamine (PPD), aiming at improving the wet-skid resistance and reduce the rolling loss of solution polymerized styrene-butadiene rubber (SSBR). PPD with amino groups enabled GO to obtain anti-aging function. The structure of modified GO (PPD-GO) was characterized by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) and Raman spectroscopy. Mechanical tests showed that the mechanical properties of SSBR before and after aging were improved by adding PPD-GO. The results of thermogravimetric-differential scanning calorimeter synchronization analysis (TGA-DSC) indicated that SSBR/PPD-GO obtained good thermo-oxidative stability. The dynamic mechanical analysis (DMA) of SSBR composites showed that the mechanical loss factor (tanδ) peak moved to high temperature with the content of PPD-GO. The tanδ values of SSBR composites showed that it had a good effect on improving the wet-skid resistance and reducing the rolling loss of SSBR by adjusting the content of PPD-GO. In particular, with the addition of 4 phr GO, SSBR was effectively improved in mechanical properties, aging resistance, wet-skid resistance and low rolling loss.

Different component ratio of polyamide 1212/thermoplastic polyurethane blends: Effect on phase morphology, mechanical properties, wear resistance, and crystallization behavior

In this work, blends of polyamide 1212 (PA1212) and thermoplastic polyurethane (TPU) elastomer of different group distribution ratios were prepared by melt blending. The effects of different TPU additional ratios on static and dynamic mechanical properties, crystallization, and wear resistance were investigated. Scanning electron microscopy images show that the phase morphology of the blended alloy changes from an island structure to a co-continuous phase structure and then to a sea-island structure. Mechanical tests show that as the proportion of TPU in the blend increases, the flexural modulus increases, and the tensile strength and notched impact strength decrease first and then increase. Dynamic mechanical analysis shows an increase in the storage modulus ( G′) and a broadening of the loss factor peak. In addition, with the increase of TPU content, the crystallinity of PA1212 in the system decreased slightly first, and the crystallinity of PA1212 increased remarkably after the TPU content was further increased to 80 wt%.

Complex permittivity and microwave heating behavior of rod-shaped SiC and oxide (SiO2, Al2O3) mixtures

Permittivity measurement and microwave heating characteristics of rod-shaped SiC (fragmented SiC fiber) mixed with SiO2 or Al2O3 were investigated, comparing with the mixtures of other two kinds of SiC materials. Rod-shaped SiC mixtures had larger permittivity (both real and especially imaginary parts) than the other SiC mixtures, and a broad peak of loss factor (εr”) appeared around 1 GHz. Effective permittivity of mixtures was not successfully fitted by Maxwell-Garnett mixing law to the rod-shaped SiC mixtures but well fitted to other kinds of SiC mixtures.The microwave heating ability of rod-shaped SiC mixtures were much superior to that of other SiC mixtures, as expected from the larger loss factors. However, differences were observed between the mixture of rod-shaped SiC with SiO2 and with γ-Al2O3 in heating behavior and in the mixture permittivity. Interactions of the rod SiC are considered different between SiO2 and γ-Al2O3 and influenced the experimental heating data.

A facile and environmentally friendly approach to fabricate hybrid crosslinked nitrile butadiene rubber with comprehensively improved mechanical performances by incorporating sacrificial ionic bonds

It is a challenge to develop advanced elastomers with a combination of high strength, stiffness and toughness by a relatively convenient and environmentally friendly approach. Herein, we reported a facile and environmentally friendly method to prepare hybrid crosslinked nitrile butadiene rubber (NBR) comprised of covalent and ionic bonds, and this hybrid crosslinked rubber possesses comprehensively improved mechanical properties, higher crosslinking density, deformation recovery and shape memory ability. The hybrid crosslinked NBR was prepared by incorporating 2-acrylamido-2-methyl propane sulfonic acid (AMPS) and zinc oxide (ZnO) into NBR via internal milling together with dicumyl peroxide (DCP), and then vulcanization, which is a very simple and environmentally friendly method without extra procedure or treatment. The hybrid crosslinked network in NBR has randomly distributed covalent and ionic bond crosslinks, the strong covalent bonds serve as permanent crosslinks, imparting the elasticity, whereas the weak ionic bonds reversibly rupture and reform, dissipating the energy. Because of the restricting effect of ionic bonds on segmental movement, the hybrid crosslinked NBR shows higher glass transition temperature, lower loss factor peak value and longer relaxation time. By tuning the ionic bond strength via temperature, a much smaller range of linear viscoelastic region is observed for hybrid crosslinked NBR with high content of AMPS and ZnO at a relatively higher temperature, which endows the sample with shape memory ability. This design principle of incorporating ionic bonds to strengthen vulcanized NBR should be applicable to other diene rubber materials.

A strengthening approach for damping property and shape memory property of acrylic rubber/polylactide blends

In this work, a damping material was successfully prepared by blending acrylic rubber (ACM) and polylactide (PLA) with sulfur and soap salt as the curing agents. A phenol-formaldehyde (PF) resin was used as a modifier. The effects of PF on the mechanical properties, damping properties, compatibility and shape memory properties of the blends were studied. The compatibility and damping properties were characterized by dynamic mechanical analysis, Fourier transform infrared spectroscope and microstructure analysis. The shape memory properties were examined by thermal mechanical analyser. The results revealed that the tensile strength of the blends was decreased and the toughness was increased with the increase of PF loadings. The introduction of PF improved the compatibility between PLA and ACM, which was deduced from the fact that the glass transition temperature of ACM was increased and the two loss factor peaks became closer. It was also found that the loss factor peak became higher and the effective damping temperature range became wider due to the formation of hydrogen bonding, implying that the damping properties of ACM/PLA blends were significantly improved. The ACM/PLA blends exhibited good dual-shape memory effect and its shape recovery ratio was increased by introduction of PF and raising the trigger temperature. The blends also exhibited good triple-shape memory property, which was dramatically improved by the introduction of PF. The mechanisms for the enhanced shape memory effects were then analysed.

Digital image processing and thermo-mechanical response of neat epoxy and different laminate orientations of fiber reinforced polymer composites for vibration isolation applications

In this study, tensile tests are performed under quasi-static loading on neat epoxy and for different laminate configurations [(0/90), (0/90/30/–60), (0/90/45/–45) and (30/–60/60/–30)] of glass/epoxy, carbon/epoxy and cross ply interply hybrid (glass/carbon/epoxy) composites. A camera-based advanced image processing technique called as digital image correlation is employed to obtain the full-field strain fields and identify the direction of failure of the matrix and composites as a function of fiber orientation angle. Further, the viscoelastic properties (storage modulus, loss modulus and loss factor) are measured over the temperature range from 20 °C–140 °C for five different frequencies (1, 10, 20, 33 and 50 Hz) using the dynamic mechanical analyzer. The glass transition temperature (Tg) is found out from temperatures corresponding to the loss modulus and loss factor peak values. The results revealed that as the temperature increases, the storage and loss moduli decrease attributed to the softening of the material because of free molecular movements. The cross ply laminates of GFRP and CFRP exhibit higher storage and loss moduli at all frequencies due to strong fiber network as compared to the other laminate configurations. The hybrid composites possess higher storage and loss moduli than GFRP and neat epoxy. The neat epoxy has higher loss factor values than composites. As the frequency increases, the Tg shifts to higher values. Loss modulus Tg values are found to be lower than that of loss factor Tg values.

Enhanced thermal and mechanical properties by cost-effective carboxylated nanodiamonds in poly (vinyl alcohol)

In this study, the high-energy ball-milled nanodiamonds (MNDs) are carefully treated with low-temperature annealing and mixed acids to obtain carboxylated MNDs (cMNDs). This process not only removes impurities but also grafts oxygen containing functional groups onto MNDs surfaces. Then poly (vinyl alcohol) (PVA)/cMND nanocomposites are prepared by a facile aqueous solution casting method. Compared with PVA/MND, an improved dispersion of nanoparticles in the matrix and higher nanoparticles content can be achieved by PVA/cMND. It is found that glass transition temperature (Tg) and loss factor peak temperature (Ttanδ) of PVA/cMND nanocomposites are both shifted to higher values than pure PVA. Thermal decomposition of PVA is obviously suppressed by cMNDs. The onset and maximum decomposition temperatures increases by over 17 °C and 24 °C, respectively. The thermal conductivity increases by 57.5%. Furthermore, tensile strength and Young’s modulus of PVA are improved by 62.3% and 166.7% with the addition of cMNDs.

Evaluation of Filler Effects on the Dynamic Mechanical Behavior of HTPB-Elastomer Used as Binder in Exemplary Composite Formulations

This study aims to evaluate the dynamic mechanical properties of a binder, used in composite propellants, with increasing amount of different solid fillers. Dynamic Mechanical Analysis (DMA) is performed to determine the region of glassrubber transition temperature (Tg). Further parameters were obtained from the description of the loss factor curves (tanδ) with models based on exponentially modified Gauss (EMG) distribution function. Polyurethane binders employing the polyol HTPB and diisocyanate were filled with 20,40,and 60 mass-% of ammonium perchlorate (AP), aluminum (Al) or cyclotrimethylene trinitramine (RDX) particles, using fine and coarse mean sizes. A special turning device manufactured by Fraunhofer ICT was installed inside the curing oven in order to avoid sedimentation during curing. The cured composites were characterized by DMA in torsion mode from ‑100 °C to 70 °C. The good homogeneous distribution of fillers in the samples was evaluated by computational X-ray micro-tomography. The data on tanδ showed a complex structure describable at first with 2 overlapping peaks. The peak at lower temperatures is due to mobility of unrestricted binder parts (Tg unr) and the second broader peak at high temperature is due to mobility of restricted binder parts (Tg res). Results of tanδ, calculated areas of EMG curves and apparent activation energies of the distinct relaxation processes indicate that Al particles have higher interaction with HTPB-based polyurethane than AP and RDX. Probably Al is bonded to the binder network via isocyanate coupling with OH groups present in the surface. Ammonium perchlorate and cyclotrimethylene trinitramine particle sizes and its morphology influenced the viscoelastic properties. AP and RDX cause more changes in intensity of first peak of loss factor than Al. Increasing amount of these both particles enhances storage (G’) and loss (G”) shear moduli. As a whole tanδ intensity is lowered in the main peak and Al showed an intensity increase in the second apparent peak.

Epoxy resin modified maleic anhydride‐grafted‐liquid polybutadiene on the properties of short aramid fiber reinforced natural rubber composite

A novel compatibilizer with high grafting degree (GD%) of maleic anhydride (MA) onto liquid polybutadiene (LPB) was synthesized via a solution method, in particular, very low gel rate was produced by the synergetic effects of acetanilide and epoxy resin (EP), and the GD% was improved by adding the EP resin and acetanilide. The structure and thermal stability of the MA‐grafted‐liquid polybutadiene (LPB‐g‐MA) were characterized by acid base titrations, FTIR, and TGA techniques. The results showed that both MA and EP resin have been grafted onto the macromolecular chains of LPB with a good thermal stability. Then, it was used as compatibilizer in short aramid fiber (AF) reinforcing natural rubber (NR)/carbon black (CB). The synthetic compatibilizer (LPB‐g‐MA) enhanced the interfacial interaction between the fiber and the rubber matrix with a lower swelling degree and lower peak of loss factor, and the mechanical properties including tensile strength, tensile modulus 100%, tear strength and elongation at break of the final composites increased with the increase of m (E51)/m (LPB). AF and CB had a synergistic effect to reinforce the properties of NR. The dynamic stiffness of the rubber was obviously improved by the short AF, especially in the presence of the compatibilizer. POLYM. COMPOS., 39:E2006–E2015, 2018. © 2017 Society of Plastics Engineers

Dielectric Properties of Biomass/Biochar Mixtures at Microwave Frequencies

Material dielectric properties are important for understanding their response to microwaves. Carbonaceous materials are considered good microwave absorbers and can be mixed with dry biomasses, which are otherwise low-loss materials, to improve the heating efficiency of biomass feedstocks. In this study, dielectric properties of pulverized biomass and biochar mixtures are presented from 0.5 GHz to 20 GHz at room temperature. An open-ended coaxial-line dielectric probe and vector network analyzer were used to measure dielectric constant and dielectric loss factor. Results show a quadratic increase of dielectric constant and dielectric loss with increasing biochar content. In measurements on biochar, a strong dielectric relaxation is observed at 8 GHz as indicated by a peak in dielectric loss factor at that frequency. Biochar is found to be a good microwave absorber and mixtures of biomass and biochar can be utilized to increase microwave heating rates for high temperature microwave processing of biomass feedstocks. These data can be utilized for design, scale-up and simulation of microwave heating processes of biomass, biochar, and their mixtures.

Three-Dimensional Modeling and Measurement of Coupling AC Loss in Soldered Tapes and Striated Coated Conductors

Coupling ac loss between superconducting filaments or tapes produces additional heating, complicating the cryogenics of superconducting applications and reducing their efficiency. Predicting the coupling currents and the loss that they generate in general 3-D samples require numerical computations. These may reduce the coupling loss by sample optimization and are necessary for the device design. In this work, we model and measure coupling (and hysteresis) loss of soldered and striated tapes. Coupling loss is measured at 72 and 144 Hz for applied fields up to 100-mT amplitude and frequencies from 2.4 to 576 Hz for applied magnetic fields around 4 mT. Modeling is based on an original variational principle. This model is also benchmarked with finite-element method computations, showing good agreement. For both models, we assume an isotropic power law relation between the electric field and the current density. We also introduce a simpler 3-D model that assumes zero resistivity in the superconductor. The latter model, together with cross-sectional methods for the hysteresis loss, is enough to satisfactorily predict the ac loss, except for applied field amplitudes above the loss factor peak and very short samples. The variational method is promising for more complicated 3-D situations.

Processing and characterization of reclaimed rubber composite materials

The dynamic mechanical properties of environment-friendly elastomeric composites consisting of reclaimed rubber (r-rubber), a waste product of roller processing of textile mill, and organic hindered phenol compound 4,4′-thio-bis(6-tert-butyl-m-methyl phenol) (AO-300) were investigated. With incorporation of AO-300 into the r-rubber, the storage modulus (E′) and loss modulus (E′′) of r-rubber were found to increase sharply, the maximum loss factor (tanδ) peak value increased from 0.49 to 1.01, and tanδ peak position was significantly shifted from 6.19 to 34.42 °C, indicating that r-rubber/AO-300 composite is a promising damping material. Furthermore, r-rubber/AO-300 systems exhibited an exceptional damping performance in the wide temperature range and with increasing AO-300 content, the effective temperature range increased from 55.32 to 63.14 °C. Meanwhile, the presence of intermolecular hydrogen bonds in the composite was confirmed by FTIR. Furthermore, from the SEM analysis of various r-rubber/AO-300 systems, it could be seen that by introduction of a small amount of AO-300 to the r-rubber, a typical complex morphology and hybrid state were coexistent in the composites. When the AO-300 content was larger than the critical value, more excess AO-300 molecules were crystallized. Thus, a new type of environment-friendly r-rubber based high-performance damping materials with a broad temperature range of damping behavior was developed.

Toughening with little rigidity loss and mechanism for modified polypropylene by polymer particles with core–shell structure

Toughening with little rigidity loss was achieved by adding high density polyethylene (HDPE) into polypropylene/ethylene-propylene random copolymer (PP/EPR) blends to fabricate a series of PP/EPR/HDPE ternary blends with core–shell dispersed particles. Morphology observations revealed that the addition of HDPE leads to the appearance of core–shell dispersed particles in PP matrix, i.e., HDPE core encapsulated in EPR shell. Dynamic mechanical analysis results showed that the introduction of HDPE could increase glass transition temperature (Tg) and loss factor peak area of EPR in PP/EPR/HDPE blends, which is similar to the effect of adding EPR in PP/EPR. The shrinkage behavior results suggested that the increase of glass transition temperature of EPR was induced by the mismatch of thermal expansion coefficients of components and the larger peak area was ascribed to the stronger relaxation friction of EPR. According to percolation of stress volumes, the interparticle distance was proposed to be a key factor of toughening effect of rubber particles in thermoplastic and thereby a toughening mechanism about the equivalent rubber content was established to explain balanced toughness-strength improvement of PP/EPR/HDPE blends with core–shell particles. The rubber particles with core–shell structure lead to the increase of particle size and the decrease of interparticle distance on the premise of not increasing actual rubber content, resulting in a notable improvement of toughness, while the ‘hard’ core made from HDPE component provides a satisfied rigidity.