Rubbery Core Research Articles

Nano-cavitation structure toughness mechanism and optical properties of amphiphilic acrylate block copolymer modified epoxy system

A series of amphiphilic acrylate block copolymer (ABC) modified epoxy were prepared by the solution casting method. The mechanical strength, thermal stability, and light transmittance of the modified epoxies were characterized, and the fracture surfaces of the ABC modified epoxy were characterized with multi techniques for the toughening mechanism exploration. The results indicated that the glass transition temperature (Tg) and tensile strength of the ABC modified epoxy would be slight increased as 10 phr ABC was incorporated into epoxy matrix compared with neat epoxy. Surprisingly, the critical strain energy release rate (GIC) and plan strain fracture toughness (KIC) of the blend with 10 phr ABC/epoxy were 8 times and 2 times higher than that of the neat epoxy at room temperature, respectively. When the addition amount of ABC reached up to 30 phr, the ABC modified epoxy showed superior adhesion strength and still remained excellent optical property. The nano-cavitation of rubbery core which facilitated shear yielding of the epoxy matrix was found to be the main toughening mechanism. Both theoretical and experimental results strongly indicate that ABC modified epoxy is a new type of composite material with excellent mechanical properties and light transmittance.

Fracture properties of epoxy polymers modified with cross-linked and core–shell rubber particles

To improve the toughness of epoxy polymers, cross-linked rubber (CLR) particles or core–shell rubber (CSR) particles can be blended into the epoxy matrix. Particle cavitation is thought to be the main toughening mechanism of rubber-modified epoxies. Although CLR-modified epoxies have not been studied in depth previously, it is expected that the toughening mechanism differs from that of CSR-modified epoxies because void formation is less likely to occur. We formed the CLR- and CSR-modified epoxy resins using nanosized acrylonitrile butadiene CLR particles, which showed good compatibility with the epoxy matrix and the CSR particles with a rubbery core surrounded by a glassy shell. The toughening mechanism was examined by comparing the fracture behavior, fracture surfaces, and process zones via tensile and fracture toughness testing, scanning electron microscopy (SEM), transmission electron microscopy (TEM), and transmission optical microscopy (TOM). There was a difference in the characteristics of the R-curves between the CLR- and CSR-modified epoxies. In addition, the SEM and TEM observations indicated that there was a difference in the fracture mechanism.

Synthesis and characterization of core-shell nanoparticles and their application in dental resins

The aim of this study was to synthesize acrylic core-shell particles and silica-loaded core-shell hybrid particles through emulsion polymerization. Also this work examined the influence of synthesized nanoparticles loading in a Bis-GMA/TEGDMA resin matrix on some mechanical properties of the dental composite resins. Core-shell particles consisting of polybutyl acrylate (PBA) rubbery core and polymethyl methacrylate (PMMA)/polystyrene (PS) shell were synthesized by seeded emulsion polymerization. For preparing the core-shell hybrid particles, first silica particles with diameters of about 68nm were synthesized based on the Stöber process. Then the surface of silica particles was treated with ɣ-MPS. Afterwards, polymeric shell was coated on silica nanoparticles through emulsion polymerization. The morphology of core-shell particles was examined by SEM/TEM. Mechanical properties (fracture toughness, flexural strength and flexural modulus) of the photo-cured Bis-GMA/TEGDMA dental resins/composites filled with different mass fractions of synthesized nanoparticles were tested, and analysis of variance (ANOVA) was used for the statistical analysis of the acquired data. Formation of glassy shell on PBA core in core-shell particles, grafting of ɣ -MPS onto the silica particles and encapsulation of modified silica by polymeric shell in core-shell hybrid particles were confirmed using various analytical techniques. The results of mechanical tests showed that fracture toughness of Bis-GMA/TEGDMA dental resins improved about 35% by the inclusion of 5wt% silica-loaded core-shell hybrid particles with little effect on flexural strength. This study shows that incorporation of proper amount of hybrid core-shell particles in dental composites can improve their fracture toughness and thus may extend their service life.

Toughening epoxy asphalt binder using core-shell rubber nanoparticles

Abstract Core-shell rubber (CSR) has been widely applied in the improvement of the toughness for the brittle epoxy resin. In this study, an epoxy asphalt (EA) binder has been toughened by the inclusion of CSR nanoparticles with approximately 100–200 nm in diameter. The incorporation of CSR nanoparticles significantly increased the viscosity of the pure EA during curing. Even with 5 wt% CSR, the EA blend exhibited extremely long operational lifetime (more than 2.5 h) for mixture pavements. The glassy shell of CSR nanoparticles was broken and the rubbery core of CSR nanoparticles swelled in the EA. New micro-scale CSR domains formed and uniformly dispersed in the epoxy phase of the cured EA. The inclusion of CSR nanoparticles altered the phase separation mechanism of the pure EA. The sea-island morphology of the pure EA took place through the nucleation and growth (NG) mechanism, while co-continuous microstructures in the EA blends with 3 wt% and 5 wt% CSR formed through the spinodal decomposition (SD) mechanism. Both sea-island and co-continuous microstructures via combined the NG and SD mechanisms were observed in the EA blend containing 1 wt% CSR. The glass transition temperature and thermal stability of the pure EA was improved by the inclusion of higher CSR loadings. The incorporation of CSR greatly enhanced the mechanical properties of the pure EA. In the case of 1 wt% CSR inclusion, 29% increase in the tensile strength, 60% improvement in the elongation at break and 2-fold increment in the toughness were obtained.

Damage Evolution and Fracture Events Sequence Analysis of Core-Shell Nanoparticle Modified Bone Cements by Acoustic Emission Technique.

In this research, damage in bone cements that were prepared with core-shell nanoparticles was monitored during four-point bending tests through an analysis of acoustic emission (AE) signals. The core-shell structure consisted of poly(butyl acrylate) (PBA) as rubbery core and methyl methacrylate/styrene copolymer (P(MMA-co-St)) as a glassy shell. Furthermore, different core-shell ratios 20/80, 30/70, 40/60, and 50/50 were prepared and incorporated into the solid phase of the bone cement formulation at 5, 10, and 15 wt %, respectively. The incorporation of a rubbery phase into the bone cement formulation decreased the bending strength and bending modulus. The AE technique revealed that the nanoparticles play an important role on the fracture mechanism of the bone cement, since a higher amount of AE signals (higher amplitude and energy) were obtained from bone cements that were prepared with the nanoparticles in comparison with those without nanoparticles (the reference bone cement). The SEM examination of the fracture surfaces revealed that all of the bone cement formulations exhibited stress whitening, which arises from the development of crazes before the crack propagation. Finally, the use of the AE technique and the fracture surface analysis by SEM enabled insight into the fracture mechanisms that are presented during four-point bending test of the bone cement containing nanoparticles.

In situ formation of PLA-grafted alkoxysilanes for toughening a biodegradable PLA stereocomplex thin film.

Poly(lactide) (PLA) has received tremendous attention recently from researchers and industrialists due to its ability to solve environmental problems related to plastic pollution. However, PLA's brittleness, poor thermal stability, low elongation at break, and poor melt processing prevent its use in a broader spectrum of applications. Herein, we produced a very tough and thermally more stable PLA stereocomplex by simply mixing PLA with organoalkoxysilane. The stereocomplex PLA/silane (sc-PLA–silane) composite was prepared by simple mixing of three types of organoalkoxysilanes in sc-PLA followed by in situ formation of a silane-based rubbery core with a cross-linked PLA shell. Mechanical and thermal properties were improved by stereocomplexation of PLA with a small amount (1–5 wt%) of PLA-grafted silanes. The addition of organoalkoxysilane with different functional groups resulted in a plasticizer of rubbery silica-PLA core–shell gel through in situ condensation and grafting of long PLA chains at the interface between the stereocomplex and silane particles. The results revealed that the toughness of sc-PLA was improved dramatically with only a small addition (only 2.5%) of 3-(triethoxysilyl)propyl isocyanate (ICPTES). The morphology and mechanical and thermal properties of the toughened stereocomplex films were characterized. The results revealed that elongation at break was increased from 16% to 120%, while other mechanical properties such as tensile strength and modulus were retained. Surface analysis confirmed that this toughness was achieved by formation of a silica-PLA core–shell gel. The mechanical properties of PLA were improved without any significant reduction in modulus and tensile strength using this simple methodology.

Effect of particle size and crosslinking on the toughening of core-shell-type rubber-modified poly(lactic acid) composites

Abstract The toughness of poly(lactic acid) (PLA) has been improved without loss of its intrinsic physical properties by incorporating core-shell-type rubber particles (CSRs) which have a rubbery core of poly(n-butyl acrylate) and a rigid shell of poly(methyl methacrylate). The CSRs of different sizes were prepared via emulsion polymerization and mixed into PLA in different amounts using a twin-screw extruder. The size and distribution of the CSRs were measured by an electrophoretic light scattering photometer and their morphology was observed by scanning electron microscopy and transmission electron microscopy. The core size of the CSRs was determined to be ∼120–650 nm, and it was confirmed that relatively uniform rubber particles with a core-shell structure had been produced. The mechanical properties of PLA/CSR blends were measured using a universal testing machine and Izod impact tester. It was found that the impact strength and elongation at break increased without the loss of thermal properties in PLA mixed with rubber particles of a specific particle size. The fractured surface of the specimen after the impact test and the toughening mechanism of rubber-toughened PLA was studied by examining the fracture morphology.

Damage accumulation studied by acoustic emission in bone cement prepared with core–shell nanoparticles under fatigue

Analysis of acoustic emission signals generated during the fatigue testing of core–shell nanoparticles filled acrylic bone cements is reported. Core–shell nanoparticles composed of a poly(butyl acrylate) rubbery core and a poly(methyl methacrylate-co-styrene) (P(MMA-co-St)) outer glassy shell with varying compositions (20/80, 30/70, 40/60, and 50/50) were incorporated into the solid phase of bone cement at 10 wt%. Acoustic emission data revealed that the damage accumulation process was discontinuous for all bone cement formulations, being less pronounced in formulations with higher fatigue resistance (20/80 and 30/70) which emitted a higher number of events before the final fracture. The capability of both 20/80 and 30/70 core–shell nanoparticles to hinder the microcracks or crazes propagation was attributed to their poor interfacial adhesion with the matrix in comparison with formulations with 40/60 and 50/50 core–shell nanoparticles. Based on the acoustic emission data and SEM micrographs, a crack propagation scheme for bone cements containing core–shell nanoparticles was proposed. In this regard, core–shell nanoparticles had a double role on the bone cement as reported for other systems; firstly, the nanoparticles promoted nucleation sites for crazes or microcracks, and secondly, they could also hinder the propagation of these defects, acting as a barrier to their growth. Crack propagation mechanism consisted mainly in crazing ahead of the cracks tip as well as the coalescence of these cracks which were responsible of the acoustic emission detected.

Evaluation of damage progression and mechanical behavior under compression of bone cements containing core–shell nanoparticles by using acoustic emission technique

In this work, the effect of the incorporation of core-shell particles on the fracture mechanisms of the acrylic bone cements by using acoustic emission (AE) technique during the quasi-static compression mechanical test was investigated. Core-shell particles were composed of a poly(butyl acrylate) (PBA) rubbery core and a methyl methacrylate/styrene copolymer (P(MMA-co-St)) outer glassy shell. Nanoparticles were prepared with different core-shell ratio (20/80, 30/70, 40/60 and 50/50) and were incorporated into the solid phase of bone cement at several percentages (5, 10 and 15 wt%). It was observed that the particles exhibited a spherical morphology averaging ca. 125 nm in diameter, and the dynamic mechanical analysis (DMA) thermograms revealed the desired structuring pattern of phases associated with core-shell structures. A fracture mechanism was proposed taking into account the detected AE signals and the scanning electron microscopy (SEM) micrographs. In this regard, core-shell nanoparticles can act as both additional nucleation sites for microcracks (and crazes) and to hinder the microcrack propagation acting as a barrier to its growth; this behavior was presented by all formulations. Cement samples containing 15 wt% of core-shell nanoparticles, either 40/60 or 50/50, were fractured at 40% deformation. This fact seems related to the coalescence of microcracks after they surround the agglomerates of core-shell nanoparticles to continue growing up. This work also demonstrated the potential of the AE technique to be used as an accurate and reliable detection tool for quasi-static compression test in acrylic bone cements.

Toughening of epoxy resin with functionalized core‐sheath structured PAN/SBS electrospun fibers

ABSTRACTCore‐sheath structured electrospun fibers with styrene‐butadiene‐styrene (SBS) block copolymer as a rubbery core and polyacrylonitrile (PAN) as a hard sheath were prepared by coaxial electrospinning, and used to improve the toughness of epoxy resin. The surface of the fibers was aminated by reacting PAN with diethylenetriamine to improve the interfacial interaction between the fibers and epoxy. Scanning and transmission electron microscopies confirm the core‐sheath structure of the PAN/SBS fibers. The Charpy impact energy is increased by the addition of electrospun fibers. When the content of aminated core‐sheath fibers is 4 wt %, the Charpy impact energy is increased by 150%. Dynamic mechanical analysis shows that the glass transition temperature of epoxy is not decreased by the addition of core‐sheath fibers. The high impact resistance is attributed to the rubbery core of the fibers that can absorb and dissipate impact energy, and the chemical bonding between the fibers and epoxy. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 41119.

Biodegradable “Core–Shell” Rubber Nanoparticles and Their Toughening of Poly(lactides)

Poly(lactide) (PLA) nanocomposites were fabricated by solution blending of commercial poly(l-lactide) (PLLA) and biodegradable core–shell particles, in which the core–shell particles were synthesized via octa polyhedral oligomeric silsesquioxane (octaPOSS)-initiated ring-opening copolymerization of a mixture of e-caprolactone and l-lactide to form poly(e-caprolactone-co-lactide) (PCLLA) as rubbery core, followed by polymerization of d-lactide to form poly(d-lactide) (PDLA) as outer shell. The outer PDLA layer could facilitate strong interactions between core–shell rubber particles and PLLA matrix via formation of stereocomplex. The randomness of PCLLA and the subsequent grafting of PDLA were monitored using nuclear magnetic resonance (NMR). The rubbery characteristic of PCLLA was confirmed by differential scanning calorimetry (DSC) which showed a Tg of ∼−7 °C. Stereocomplexation between PLLA and POSS-rubber-D was confirmed using Fourier transform infrared spectroscopy (FT-IR), DSC, and X-ray diffraction (...

Synthesis and characterization of core–shell nanoparticles and their influence on the mechanical behavior of acrylic bone cements

Core-shell nanoparticles consisting of polybutyl acrylate (PBA) rubbery core and a polymethyl methacrylate (PMMA) shell, with different core-shell ratios, were synthesized in order to enhance the fracture toughness of the acrylic bone cements prepared with them. It was observed by TEM and SEM that the core-shell nanoparticles exhibited a spherical morphology with ca. 120 nm in diameter and that both modulus and tensile strength decreased by increasing the PBA content; the desired structuring pattern in the synthesized particles was confirmed by DMA. Also, experimental bone cements were prepared with variable amounts (0, 5, 10 and 20 wt.%) of nanoparticles with a core-shell ratio of 30/70 in order to study the influence of these nanostructured particles on the physicochemical, mechanical and fracture properties of bone cements. It was found that the addition of nanostructured particles to bone cements caused a significant reduction in the peak temperature and setting time while the glass transition temperature (Tg) of cements increased with increasing particles content. On the other hand, modulus and strength of bone cements decreased when particles were incorporated but fracture toughness was increased.

Role of Localized Network Damage in Block Copolymer Toughened Epoxies.

The underlying mechanisms responsible for the toughening of block copolymer modified thermoset epoxies are not completely understood. A current theory targets cavitation of the rubbery cores in dispersed micelles as the key event that triggers shear yielding, resulting in enhanced toughness. To evaluate this hypothesis, we prepared spherical micelle forming block copolymers with rubbery cores (prone to cavitation) and glassy cores (unable to cavitate). Surprisingly, both systems enhance fracture toughness, although the rubbery core micelles outperform the glassy core counterparts. This finding challenges previous deductions regarding the toughening mechanism. We propose that the mechanical integrity of the region immediately surrounding the micelle core is compromised by the presence of the corona blocks, facilitating local deformation of the matrix. We speculate that the compliant nature of the rubber amplifies this effect.

Shear-induced gelation of soft strawberry-like particles in the presence of polymeric P(BA-b-AA) surfactants

The effect of polymeric surfactants, copolymers of n-butyl acrylate (BA) and acrylic acid (AA), on shear-induced gelation of a colloidal system in the absence of additional electrolytes is studied. One random (PBA-co-PAA) and two block copolymer (PBA-b-PAA, with different PAA lengths) surfactants have been synthesized by ATRP and used in this work. The colloidal system is composed of strawberry-like particles with a rubbery core, partially covered by a few grafted plastic patches. In the absence of any surfactant, as the colloidal system passes through a microchannel at a Peclet number of 220 and a particle volume fraction of 0.15, shear-induced gelation occurs and the particles coalesce partially, due to the rubbery core, leading to a fractal dimension of the clusters constituting the gel equal to 2.78. On the other hand, in the presence of any of the three polymeric surfactants, shear-induced gelation occurs only in the range of low surfactant surface density. Meanwhile, the fractal dimension of the clusters decreases with adsorption of the two block surfactants, reaching a plateau value of about 2.58, while for the random surfactant it remains constant and equal to 2.78, like in the absence of any surfactant. This indicates that adsorption of the block surfactants can reduce the particle coalescence, while adsorption of the random surfactant cannot. Moreover, for all three surfactants, as their surface density increases progressively, a transition from solid-like gel to a liquid-like state occurs and finally no shear-induced gelation or even aggregation occurs. Since the three surfactants comprise carboxylic groups, considering also the results in the literature (Zaccone et al., J. Phys. Chem. B, 2008, 112, 1976; 6793), we can reach a general conclusion that carboxylic groups on the particle surface not only stabilize the particles through electrostatic repulsion, but also generate very short-range, strongly repulsive (e.g. hydration, steric) forces, which when high enough protect the particles from intense shear-activated aggregation.

Colloidal Ionic Assembly between Anionic Native Cellulose Nanofibrils and Cationic Block Copolymer Micelles into Biomimetic Nanocomposites

We present a facile ionic assembly between fibrillar and spherical colloidal objects toward biomimetic nanocomposites with majority hard and minority soft domains based on anionic reinforcing native cellulose nanofibrils and cationic amphiphilic block copolymer micelles with rubbery core. The concept is based on ionic complexation of carboxymethylated nanofibrillated cellulose (NFC, or also denoted as microfibrillated cellulose, MFC) and micelles formed by aqueous self-assembly of quaternized poly(1,2-butadiene)-block-poly(dimethylaminoethyl methacrylate) with high fraction of the NFC reinforcement. The adsorption of block copolymer micelles onto nanocellulose is shown by quartz crystal microbalance measurements, atomic force microscopy imaging, and fluorescent optical microscopy. The physical properties are elucidated using electron microscopy, thermal analysis, and mechanical testing. The cationic part of the block copolymer serves as a binder to NFC, whereas the hydrophobic rubbery micellar cores are designed to facilitate energy dissipation and nanoscale lubrication between the NFC domains under deformation. We show that the mechanical properties do not follow the rule of mixtures, and synergistic effects are observed with promoted work of fracture in one composition. As the concept allows wide possibilities for tuning, the work suggests pathways for nanocellulose-based biomimetic nanocomposites combining high toughness with stiffness and strength.

Effect of Surfactants on Shear-Induced Gelation and Gel Morphology of Soft Strawberry-like Particles

The role of surfactant type in the aggregation and gelation of strawberry-like particles induced by intense shear without any electrolyte addition is investigated. The particles are composed of a rubbery core, partially covered by a plastic shell, and well stabilized by fixed (sulfate) charges in the end group of the polymer chains originating from the initiator. In the absence of any surfactant, after the system passes through a microchannel at a Peclet number equal to 220 and a particle volume fraction equal to 0.15, not only shear-induced gelation but also partial coalescence among the particles occurs. The same shear-induced aggregation/gelation process has been carried out in the presence of an ionic (sulfonate) surfactant or a nonionic (Tween 20) steric surfactant. It is found that for both surfactants shear-induced gelation does occur at low surfactant surface density but the conversion of the primary particles to the clusters constituting the gel decreases as the surfactant surface density increases. When the surfactant surface density increases above certain critical values, shear-induced gelation and eventually even aggregation do not occur any longer. For the sulfonate surfactant, this was explained in the literature by the non-DLVO, short-range repulsive hydration forces generated by the adsorbed surfactant layer. In this work, it is shown that the steric repulsion generated by the adsorbed Tween 20 layer can also protect particles from aggregation under intense shear. Moreover, the nonionic steric surfactant can also protect the strawberry-like particles from coalescence. This implies a decrease in the fractal dimension of the clusters constituting the gel from 2.76 to 2.45, which cannot be achieved using the ionic sulfonate surfactant.

Effect of a Thin Soft Core on the Impact Behaviour of CFRP Laminates

Low-velocity impact tests were carried out on sandwich plates having CFRP facings and thin rubbery core. Two types of cores, differing in the material nature and thickness, were used. For comparison, similar tests were performed on the monolithic laminate. Various impact parameters, among which indentation, first failure energy, perforation energy, absorbed energy and maximum contact force, were analyzed, to highlight the effect of the core on the material response. The influence of the core on the macroscopic behaviour of the panels was quite limited, except in the elastic phase, where the lower stiffness of the sandwich configurations resulted in a higher energy at first failure. More relevant differences were found from the study of failure modes, carried out combining ultrasonic C-scan and a limited number of microscopic observations. In particular, in correspondence of the energy for barely visible impact damage, besides considerable facing-core debonding, both the facings of the sandwich structures exhibited fibre breakage at their back side.

Effect of Primary Particle Morphology on the Structure of Gels Formed in Intense Turbulent Shear

We study the effect of primary particle morphology on intense shear-induced gelation without adding electrolytes. The primary particles are composed of a rubbery core grafted with a polystyrene shell. Depending on the shell-to-core mass ratio, the core can be partially covered by the shell, leading to strawberry-like morphology. It is found that at a fixed core mass the fractal dimension of the clusters constructing the gel decreases (i.e., more open cluster structure) as the shell mass increases, until reaching a plateau. The SEM pictures of the gels reveal that the structure variations are due to the occurrence of partial coalescence among particles, which decreases as the shell mass increases. In the region where the fractal dimension reaches a plateau, the coalescence is negligible. The conversion of the primary particles to gels is incomplete and increases as the extent of coalescence decreases. This is related to the fact that the smaller the extent of coalescence, the larger the cluster size. Thus, because of its cubic dependence on the cluster size, the aggregation rate increases as the extent of coalescence decreases, leading to increased conversion. It is therefore evident that the key parameter controlling the gel structure and the particle conversion is the core surface coverage by the shell. To further verify this conclusion, we have carried out the shear-induced gelation of another set of particles with varying core mass. It is found that the only parameter that can well correlate the values of the fractal dimension and particle conversion from the two sets of particles is the core surface coverage.

Kinetics of re‐embrittlement of (anti)plasticized glassy polymers after mechanical rejuvenation

AbstractMechanical rejuvenation is known to dramatically alter the deformation behavior of amorphous polymers. Polystyrene (PS)—for example, typically known as a brittle polymer—can be rendered ductile by this treatment, while a ductile polymer like polycarbonate (PC) shows no necking anymore and deforms homogeneously in tensile deformation. The effects are only of temporary nature, as because of physical aging the increasing yield stress, accompanied by intrinsic strain softening, renders PS brittle after a few hours, while for PC necking in tensile testing returns in a few months after the mechanical rejuvenation treatment. In this study, it is found that physical aging upon rejuvenation in both PS and PC can be delayed in two different ways: (1) by reducing the molecular mobility through antiplasticization and (2) by applying toughening agents (rubbery core–shell particles). For the first route, even though progressive aging is found to decrease with increasing amounts of antiplasticizer added, dilution of the entanglement network results in enhanced brittleness. Besides antiplasticization effects, also some typical plasticization effects are observed, like a reduction in matrix Tg. For the second route, traditional rubber toughening using acrylate core–shell modifiers also results in a reduced yield stress recovery, and ductile tensile deformation behavior is observed even 42 months after mechanical rejuvenation. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 134–147, 2008

Effect of the Shell Thickness of Methacrylate-Butadiene-Styrene Core–Shell Impact Modifier on Toughening Polyvinyl Chloride

The shell thickness of methyl methacrylate-butadiene-styrene (MBS) graft copolymer with a core–shell structure is found to be the most important factor in the toughening of rigid polyvinyl chloride (PVC). When the total shell thickness is too thin, the shell layer is simply unable to fully protect and cover the inner rubbery core, and these MBS particles tend to connect with one another through the partially exposed core, which leads to the aggregation of MBS in PVC and results in the poor toughening efficiency of MBS. However, when the total shell thickness is too thick, the shell thickness results in a hard core of these core–shell MBS particles and the loss of the rubbery nature required of an efficient impact modifier. Both the PMMA thickness and PS thickness in the shell structure have also significantly influenced the toughening efficiency of MBS; the thickness of PMMA and PS should be between the critical values of 4.2 nm ∼ 6.7 nm for PMMA and 7.4 nm∼9.8 nm for PS, and MBS displays high efficiency in toughening rigid PVC. γc/Vf2 and γy/Vf2, which are relative to the critical characteristic ligament of polymer materials, are used as the criterions of the brittle–ductile transition, and the brittle–ductile transitions of PVC and MBS with various shell structures was investigated in this paper.