Synergistic Effect of Polycarbonate on Reactive Core-Shell Particles Toughened Poly(Butylene Terephthalate)

Glycidyl methacrylate functionalized methyl methacrylate-butadiene-styrene copolymer (MBS-g-GMA) core-shell particles were prepared via an emulsion polymerization process. MBS-g-GMA was used to toughen poly(butylene terephthalate) (PBT) and the synergistic toughening effect of polycarbonate (PC) on PBT/MBS-g-GMA blends were investigated. Notched impact tests showed the percolation threshold became lower with the increase of PC content. Transmission electron microscopy displayed a very good dispersion of MBS-g-GMA particles in the PBT matrix with the different PC contents. The synergistic toughening effect was due to the encapsulation structure of PC which could facilitate the whole PBT matrix to yield. The more perfect the encapsulation structure formed, the more obvious the synergistic toughening the PC achieved. Sufficient strength of the phase interface was important to ensure the stress transfer effectively and facilitate the whole PBT matrix to yield. The interface strength between PC and MBS-g-GMA could be ensured by the good miscibility between Poly(methyl methacrylate) (PMMA) (grafted onto the polybutadiene-based rubber core) and PC. For the PBT/PC, the transesterification between PBT and PC improved the interface strength of the PBT and PC phases, as demonstrated by Fourier transform infrared spectroscopy (FTIR) scans. Scanning electron microscopy results showed shear yielding of the matrix and cavitation of the rubber particles were the major toughening mechanisms.     

Mechanical,Water-swelling,and Morphological Properties of Water-swellable Thermoplastic Vulcanizates Based on Polyvinyl Chloride/Crosslinked Sodium Polyacrylate/Chlorinated Polyethylene Blends

A novel water-swellable rubber (WSR) was prepared by dynamically vulcanizing polyvinyl chloride (PVC)/chlorinated polyethylene (CPE) blends where a crosslinked poly(sodium acrylate) (CPNaAA) was used as a super water-absorbent resin and dispersed in the CPE rubber. The mechanical, water-swelling, and morphological properties were investigated. The results showed that the dynamically vulcanized PVC/CPNaAA/CPE blends exhibited obvious elastomeric behavior and could be considered as thermoplastic vulcanizates (TPVs). The PVC/CPNaAA/CPE TPVs showed strong water-swelling ability, with the water-swelling ratio of the PVC/CPNaAA/CPE TPV with 30/60/70 weight ratio reaching 2400% at 200 h immersion. Moreover, compared with the first water-swelling behavior, the second and third water-swelling behaviors of the TPVs showed significantly improved water-swelling ratio and a remarkable decrease of weight loss. Morphological study showed that the interface interaction between the CPNaAA and CPE was weak. The CPNaAA particles in the blends could be separated and even be pulled out from the matrix under tensile stress, leading to the formation of suspended CPNaAA particles on the fracture surface of PVC/CPNaAA/CPE TPVs. The surface of the dried TPVs was rough and significant cavities could be found. The dynamic mechanical properties were investigated and the TPVs showed the typical Payne effect.     

玻璃-橡胶混合颗粒的力学响应研究

通过直剪实验和离散元模拟, 研究掺杂了橡胶软球的玻璃体系的力学响应. 改变颗粒固体中橡胶颗粒的含量, 研究体系剪切强度以及剪胀变化等特性, 发现随着橡胶颗粒的增加, 会出现剪胀到剪缩的相转变现象, 且混合颗粒固体的弹性有了很大的提高. 实验研究发现, 随着体系中橡胶颗粒含量的增加, 剪切屈服强度值逐渐减小, 体积发生从剪胀到剪缩的相转变现象, 但临界剪切强度在一定橡胶颗粒含量范围内保持一致; 实验所采取的剪切速率下, 应力应变曲线能较好重合, 即实验处于率无关区域; 混合样品的屈服强度值随正压力的增大而增大. 离散元模拟也得到了上述结果, 另外模拟还发现, 随着橡胶颗粒含量的增加, 颗粒的平均配位数增大; 橡胶颗粒含量和正压力对剪胀-剪缩相转变的位置有影响, 橡胶颗粒含量较小时, 在较大的正压力下易发生相转变现象, 且剪胀-剪缩相转变点对应的平均配位数在5.6-5.9之间; 在橡胶颗粒含量小于30%时, 混合颗粒样品的残剪强度与不掺杂的颗粒体系相近; 大于30%时, 残剪强度随橡胶颗粒含量的增加而减小; 残剪强度随正压力加大而增加.     

Mechanical and Morphological Properties and Deformation Mechanisms of Acrylonitrile-Butadiene-Styrene/Poly(ϵ-Caprolactone) Blends with Varied Matrix Composition

Acrylonitrile-butadiene-styrene and poly(?-caprolactone) blends (ABS/PCL) were prepared by mixing styrene-co-acrylonitrile (SAN), polybutadiene-g-SAN (PB-g-SAN), and PCL with varied SAN and PCL composition. PCL is miscible with SAN and can improve the matrix toughness. The impact strength and elongation at break of the ABS/PCL blends increased with the PCL content. When the PCL content was lower than 20 wt%, the improvement of impact strength for the blends was not obvious. A significant increase of impact strength took place when the PCL content was between 20 and 25 wt%. When PCL content was more than 20 wt%, the impact strength was higher than 800 J/m which shows the super toughness. The addition of PCL improved the dispersed phase morphology of PB-g-SAN in the matrix and the interfacial adhesion increased. Deformation observations showed that, when the PCL content was lower than 20 wt%, crazing was the major deformation mode. When the PCL content was 20 wt%, crazing and slight shear yielding could be found. When the PCL content was more than 20 wt%, cavitation of rubber particles and shear yielding of the matrix were the major deformation modes. The cause of the change of the deformation mode lies in the varied matrix composition which modifies the crazing and yielding stresses of the matrix and the final fracture mode and impact toughness.     

The Effect of OMMT on the Morphology and Mechanical Properties of PVC/ABS Blends

Poly(vinyl chloride) (PVC)/acrylonitrile-butadiene-styrene (ABS) blends containing organically modified montmorillonite (OMMT) were prepared using a twin-screw extruder followed by injection molding. The OMMT dispersion was evaluated by X-ray diffraction and transmission electron microscopy. The clay was preferentially situated in the PVC phase and across the interfaces of PVC/ABS. The effect of the addition of OMMT on the morphology and mechanical properties was also evaluated. Scanning electron microscopy revealed a large reduction in domain size when OMMT was used. The mechanical properties were studied through tensile and impact tests. The yield stress increased when an appropriate amount of OMMT was used without impairing the impact strength.     

Effect of Unplasticized Poly Vinyl Chloride (UPVC) Molecular Weight and Graft-Acrylonitrile-Butadiene-Styrene (g-ABS) Content on Compatibility and Izod Impact Strength of UPVC/g-ABS Blends

In this study three grades of rigid poly vinyl chloride (PVC) having different molar masses were melt blended with graft-acrylonitrile-butadiene-styrene (g-ABS) in different compositions. The effect of PVC molecular weight and g-ABS composition on the compatibility and Izod impact strength of the blends were investigated. Differential scanning calorimetry (DSC) results showed a single glass transition temperature (T_g) for all the blends, representative of miscibility between the PVC phase and the styrene-acrylonitrile copolymer (SAN) phase of g-ABS which, in turn, led to compatibility of the PVC/g-ABS blends. It was observed that in all the PVC grades the blends Izod impact strength increased with increasing g-ABS content. Also, at a given composition of g-ABS, by increasing the molecular weight of the PVC phase the impact strength of the blends increased. The morphology of the fracture surfaces from the impact tests were analyzed using scanning electron microscopy (SEM) micrographs and the results showed that with increasing g-ABS content in the blend, cloudy regions increased and eventually begin to overlap each other, and the deformed material on the fracture surfaces increased. This was attributed to the blend compatibility causing greater energy dissipation in the fracture process.     

Polyvinylidene Fluoride/Acrylonitrile Butadiene Rubber Blends Prepared Via Dynamic Vulcanization

Dynamically vulcanized blends based on polyvinylidene fluoride (PVDF)/acrylonitrile butadiene rubber (NBR) were prepared and characterized. The mixing torque and dynamic rheology analyses showed that the NBR phase increased the viscosity of the blends. Scanning electron microscopy (SEM) results showed that the NBR phase was in the form of spherical particles dispersed in the PVDF phase during dynamic vulcanization. Comparing PVDF-rich and NBR-rich blends, the size of the rubber particles in the NBR-rich blends were larger than those in PVDF-rich blends. Differential scanning calorimetry (DSC) results showed that the addition of the NBR phase reduced the PVDF crystallinity and T_m. Thermal gravimetric analysis (TGA) results showed that the dynamically vulcanized PVDF/NBR blends had a higher residual char mass than the neat PVDF and NBR. For PVDF-rich blends, the PVDF can be highly toughened by NBR; the Izod impact strength of the PVDF/NBR (70/30) blend was 77.5 kJ/m², which was about six times higher than that of pure PVDF. For rubber-rich blends, the PVDF component was beneficial to the mechanical properties of the blends, which can be used as thermoplastic elastomers.     

Properties of blends of poly(vinyl chloride) and chlorinated polyethylene. I. Optical methods of characterization of PVC multiphase systems

Hitherto it has not been possible to produce a microscopic image with adequate resolution of the high-impact two-phase system poly(vinyl chloride) (PVC)/chlorinated polyethylene (CPE) due to inadequate phase contrast. With the aid of various chemical staining methods and through ion etching, a way has been found for studying the microstructure of the PVC/CPE system by light microscopy and electron microscopy. These independent visualization techniques and scanning electron micrographs of fracture surfaces show, as the morphology with optimal mechanical and rheological properties, networklike distribution of the rubber phase and, imbedded in this, a PVC phase consisting of primary particles.     

Preparation and Evaluation of the Morphology,Flammability, and Mechanical Properties of the Acrylonitrile‐Butadiene‐Styrene/Poly (vinyl chloride) Blends

Blends of two grades of acrylonitrile‐butadiene‐styrene (ABS) with three different compounds of poly (vinyl chloride) (PVC) were prepared via melt processing and their morphology, flammability, and physical and mechanical properties were investigated. SEM results showed that the ABS/PVC blend is a compatible system. Also, it can be inferred from fracture surface images that ABS/PVC blends are tough, even at low temperatures. It was found that properties of these blends significantly depend on blend composition and PVC compound type; however, the ABS types have only a small effect on blend properties. On blending of ABS with a soft PVC compound, impact strength, and melt flow index (MFI) increased, but tensile and flexural strength decreased. In contrast, blending of ABS with a rigid PVC compound improved fire retardancy and some mechanical properties and decreased MFI and impact strength.     

Effect of Surface Structure of Nano-CaCO3 Particles on Mechanical and Rheological Properties of PVC Composites

To study the effect of different surface structures on resultant mechanical and rheological properties, nano-CaCO₃ particles were treated with isopropyl tri-stearyl titanate (H928), isopropyl tri-(dodecylbenz-enesulfonyl) titanate (JN198), and isopropyl tri-(dioctylpyrophosphato) titanate (JN114). Scanning electron microscopy (SEM) and dynamic mechanic analysis (DMA), carried out to characterize the effective interfacial interaction between the nano-CaCO₃ particles and a poly(vinyl chloride) (PVC) matrix, indicated that JN114 treated nano-CaCO₃ particles had the strongest interfacial interaction with a PVC matrix, while H928 treated nano-CaCO₃ had the weakest. The rheological and mechanical properties of PVC/nano-CaCO₃ composites were investigated as a function of surface structure and filler volume fraction. The tensile yield stress and elongation at break decreased with the increasing of calcium carbonate content while tensile modulus increased. PVC filled with JN114 treated nano-CaCO₃ had the highest tensile modulus and tensile yield stress, while those filled with H928 treated nano-CaCO₃ had the highest elongation at break at the same filler content. The impact strength of PVC/nano-CaCO₃ composites increased with the increasing of CaCO₃ content, and PVC composites filled with JN198 treated nano-CaCO₃ particle had a higher impact strength than those with JN114 or H928 treated, with the value reaching 23.9 ± 0.7 kJ/m² at 11 vol% CaCO₃, four times as high as that of pure PVC. Rheological properties indicated that a suitable interfacial interaction and a good dispersion of inorganic filler in a PVC matrix could reduce the viscosity of PVC/nano-CaCO₃ composites. The interfacial interaction was quantitatively characterized by semiempirical parameters calculated from the tensile strength of PVC/nano-CaCO₃ composites to confirm the results from the SEM and DMA experiments.     

A Study on Properties of Poly(vinyl chloride)/Poly(α-methylstyrene-acrylonitrile) Binary Blends

Blends of poly(vinyl chloride) (PVC) and poly(α-methylstyrene-acrylonitrile) (α-MSAN) with variable composition of 0 to 100 wt% were prepared by melt mixing. Properties of binary blends were extensively studied by differential scanning calorimetry (DSC), dynamic mechanical thermal analysis (DMTA), attenuated total reflection-Fourier transform infrared spectroscopy (ATR-FTIR), heat distortion temperature (HDT), mechanical properties, melt flow rate (MFR), and scanning electron microscope (SEM). A single glass transition temperature (T_g ) was observed by DSC and DMTA, indicating miscibility between PVC and α-MSAN. The results of ATR-FTIR indicated that specific strong interactions were not present in the blends and the miscibility was due to interaction between –CN and PVC. With increasing amount of α-MSAN, considerable increase occurred in HDT, flexural strength, and flexural modulus compared with reverse s-shaped decrease in impact strength and elongation at break. Synergism was observed in tensile strength and MFR. No phase separation was observed in SEM photographs, indicating miscibility between PVC and α-MSAN. In addition, morphology of the impact-fractured surfaces, including roughness and non-fused particles, correlated well with the mechanical properties and MFR.     

Influence of Mixing Technique on Microstructure and Impact Properties of Isotactic Polypropylene/ Poly(Cis-Butadiene) Rubber Blends

Isotactic polypropylene/poly(cis-butadiene) rubber (iPP/PcBR vol%: 80/20) blends were prepared by melt mixing with various mixing rotation speeds. The effect of mixing technique on microstructure and impact property of blends was studied. Phase structure of the blends was analyzed by scanning electron microscopy (SEM). All of the blends had a heterogeneous morphology. The spherical particles attributed to the PcBR-rich phase were uniformly dispersed in the continuous iPP matrix. With increase of the mixing rotation speed, the dispersed phase particle's diameter distribution became broader and the average diameter of the separated particles increased. The spherulitic morphology of the blends was observed by small angle light scattering (SALS). Higher mixing rotation speed led to a more imperfect spherulitic morphology and smaller spherulites. Crystalline structure of the blends was measured by wide angle X-ray diffraction (WAXD) and small angle X-ray scattering (SAXS). The introduction of 20 vol% PcBR induced the formation of iPPβ crystals. Higher rotation speed led to a decrease in microcrystal dimensions. However, the addition of PcBR and the increase of mixing rotation speed did not affect the interplanar distance. The long period values were the same within experimental error as PcBR was added or the mixing rotation speed quickened. The normalized relative degree of crystallinity of the blends slightly increased under lower rotation speeds (30 and 45 rpm) and decreased under higher rotation speeds. The notched Izod impact strength of the blends was enhanced as a result of the increase of mixing rotation speed.     

Damping Properties of Blends Based on EVM

The mechanical and damping properties of blends of ethylene-vinyl acetate rubber (VA content >40% wt) (EVM)/ethylene-propylene-diene copolymer (EPDM) and EVM/nitrile butadiene rubber (NBR), both with 1.4 phr BIPB (bis (tert-butyl peroxy isopropyl) benzene) as curing agent, were investigated by dynamic mechanical analysis (DMA). The effect of added polyvinyl chloride (PVC), amido donor N-cyclohexyl-2-benzothiazole sulfonamide (CZ), and dicumyl peroxide (DCP) as a substitute curing agent, on the damping and mechanical properties of both rubber blends were studied. The results showed that in EVM/EPDM/PVC blends, EPDM was immiscible with EVM and could not expand the damping range of EVM at low temperature. PVC was miscible with EVM and dramatically improved the damping property of EVM at high temperature while keeping good mechanical performance. In EVM/NBR/PVC blends, PVC was partially miscible with EVM/NBR blends and remarkably widened the effective damping temperature range (EDTR) from 41.1°C for EVM/NBR to 62.4°C. Curing agents BIPB and DCP had a similar influence on EVM/EPDM blends. DCP, however, dramatically raised the height of tan δ peak of EVM/NBR = 80/20 and expanded its EDTR to 64.9°C. CZ had no obvious influence on the EVM/EPDM blends cured with BIPB. However, a small content of CZ enlarged the tan δ peak of EVM/NBR = 80/20 in both height and width, but at the cost of a deterioration of mechanical performance.     

Toughened Poly(Trimethylene Terephthalate) by Blending with a Functionalized Metallocenic Poly(Ethylene-Octene) Copolymer

New toughened poly(trimethylene terephthalate) (PTT) materials were obtained by melt blending with maleic anhydride grafted poly(ethylene-octene) (POEg). Rheological properties, mechanical properties, and morphological characteristics of PTT/POEg blends at four different compositions—95/5, 90/10, 80/20, and 70/30—were studied. The melt viscosity of the blends shows a linear decrease on increasing the POEg content. The addition of rubbery POEg to the PTT matrix increases the impact strength, while tensile properties decrease. Scanning electron microscopy (SEM) displayed a very good dispersion of POEg particles in the PTT matrix. Differential scanning colorimetry (DSC) experiments showed that for all samples the melting point was almost constant and the crystallinity did not show obvious differences. SEM results showed shear yielding of the PTT matrix was the major toughening mechanism.     

Flame-Retarding and Mechanical Properties of Flexible Polyvinyl Chloride with Surface-Treated Lamellar Magnesium Hydroxide

The effects of hydrophobic magnesium hydroxide (Mg(OH)₂) particles, prepared by a surface modification method with oleic acid, on the flame-retarding and mechanical properties of polyvinyl chloride (PVC) were investigated. Comparison between the use of modified and unmodified Mg(OH)₂ in the preparation of PVC composites showed that the former could provide excellent optical and flame-retarding properties. The dispersion of the modified Mg(OH)₂ particles in the PVC matrix was investigated through scanning electron microscopy. Compared with a composite containing unmodified Mg(OH)₂, the rheological and impact strength properties of that containing the modified Mg(OH)₂ filler were found to be significantly improved. These improvements were mostly attributed to the better dispersion of the modified Mg(OH)₂ particles and the strong adhesion between the filler and matrix.     

Percolation of electrical conductivity in solution-cast blends containing polyaniline

The potential offered by intrinsically conductive polymers is limited by their poor mechanical properties. Blending with common thermoplastics can improve processability and mechanical properties and still preserve the electrical conductivity. In such blends, the morphology determines the mechanical and electrical properties. In this research, blends of polyaniline (PANI)-dodecyl benzene sulfonic acid (DBSA) with either polystyrene (PS) in xylene or polyvinylchloride (PVC) in bromobenzene were solution cast. The morphologies of the blends were characterized by optical microscopy (OM), electron microscopy, and small-angle X-ray scattering (SAXS). Electrical conductivity was measured for various compositions. The formation of a continuous network was strongly associated with percolation and conductivity. The morphologies of the two blends are significantly different. This difference arises from the different solvents used and their ability to swell the PAN1 aggregates and to promote their disintegration into small particles. Molecular calculations show that, indeed, bromobenzene, used in the PVC system, is able to penetrate the PANI-DBSA aggregates, while xylene, used in the PS system, cannot. Nevertheless, the small PANI-DBSA particles in the PVC matrix form a conductive network only at a relatively high content, while the coarse aggregates in the PS matrix form conductive paths at a relatively low content. These results are discussed in terms of the formation and stability of the PANI-DBSA dispersion.     

Fracture Micromechanisms of Polypropylene/Polycarbonate/Poly(styrene-b-(ethylene-co-butylene)-b-styrene) (PP/ PC/SEBS) Ternary Blends: The Effects of SEBS Content

Ternary blends of polypropylene/polycarbonate/poly(styrene-b-(ethylene-co-butylene)-b-styrene) (PP/PC/SEBS) with varying SEBS contents were produced via melt blending in a co-rotating twin-screw extruder. The phase morphology of the resulting ternary blends and its relationship with bending and impact behaviors were studied. Transmission optical microscopy (TOM) of the crack tip damage zone and scanning electron microscopy (SEM) of impact fractured surfaces were performed to characterize the fracture mechanism. With increasing SEBS content in the PP/PC/SEBS ternary blends, the number of PC/SEBS core-shell particles increased and the size of the core-shell particles enlarged. It was shown that with an SEBS content of 5%, the crack initiation resistance decreased and then was almost unchanged with further increase of SEBS content, while resistance to crack growth increased continuously with increasing of SEBS content. Preliminary analysis of the micromechanical deformation suggested that the high impact toughness observed for samples containing 20 and 30 wt% of SEBS could be attributed to cavitation of the rubbery shell and, consequently, shear yielding of the matrix. This plastic deformation absorbed a tremendous amount of energy. Due to low interfacial adhesion between PC particles and PP matrix in samples containing 5 and 10 wt% of SEBS, debonding occurred too early, so the occurrence of matrix shear yielding was delayed and resulted in premature interfacial failure and, hence, rapid crack propagation.     

Microscopical study of the formation of adiabatic shear bands in 4340 steel during dynamic loading

In this study, optical microscopy, scanning electron microscopy, transmission electron microscopy, X-ray diffraction and electron probe microanalyser were used to analyse the changes in microstructure of AISI 4340 steel specimens caused by impact at high strain rates and large strains. The structures of the steel prior to dynamic deformation and after dynamic deformation were examined to understand on a microscale level, the mechanism of formation of adiabatic shear bands (ASBs). The study also includes the structural changes that occur during post-deformation annealing processes which may relate to understanding of the mechanism of formation of ASBs. Prior to deformation, the tempered steel specimens consisted of lenticular laths of α-ferrite with precipitated platelet and spherical M₃C carbides. After impact, the structure inside the shear band was characterized by refined and recrystallized grains immersed in dense dislocation structures. In addition, residual carbide particles were observed inside the shear bands due to deformation induced carbide dissolution. Regions away from the shear bands developed ‘knitted’ dislocation walls, evolving gradually into sub-boundaries and highly misoriented grain boundaries at increasing strains, leading to grain refinement of the ferrite. After impact, annealing the shear bands at 350?°C resulted in an increase in hardness regardless of the heat treatment before impact, amount of deformation and the time of annealing. This is because of the occurrence of extensive reprecipitation of dissolved carbides that existed in the steel structure prior to deformation. It is concluded that dynamic recovery/recrystallization, development of dislocation structures and carbide dissolution all contribute simultaneously to the formation of ASBs in quench-hardened steels.     

Morphology and Physical Properties of ABS/NBR: The Effect of Melt Viscosity of SAN and the Content of NBR

In several acrylonitrile-butadiene-styrene (ABS) copolymers, some amounts of polybutadiene (PB) laTeX grafted with styrene-acrylonitrile (SAN) copolymer were replaced by acrylonitrile-butadiene rubber (NBR) copolymer, and the variations of morphology, mechanical properties, and rheological properties were examined. The impact strength of ABS, with a bimodal distribution of rubber size, was improved by the presence of the NBR, which distributes coarsely in the SAN matrix. Yield behavior in the rheological response due to the presence of rubber particles in the SAN matrix was enhanced by the coarser NBR particles, especially at high temperature.     

In Situ Dynamic Vulcanization of Poly(Vinyl Chloride)/Acrylonitrile-butadiene Rubber Blends

Poly(vinyl chloride) (PVC)/acrylonitrile-butadiene rubber (NBR) blends can be obtained through a dynamic vulcanization process as a melt-processible thermoplastic elastomer which produces parts that look, feel and perform like vulcanized rubber with the advantage of being processible as a thermoplastic material. In this study, a vulcanized thermoplastic was obtained by in situ dynamic vulcanization of PVC/NBR blends using a sulphur/ tetramethylthiuram disulphide (TMTD) and mercaptobenzothiazyl disulphide (MBTS) curative system during processing at the melt state. The blends were melt-mixed using a Haake Rheomix 600. The curing behavior of NBR was then investigated by a Monsanto rheometer. The thermal analyses were performed and the cross-linking at different mixing times was calculated using DSC. FT-IR was also performed for characterization of the blends. The cross-link densities of the samples were measured by a swelling method. The degree of cure increases with the mixing time. The cross-linking formation was verified through the formation of C─ S bonds in the blends.