Enhancement of viscoelastic property of MABS processed by melt compounding and injection molding

This work is focused on developing a new type of polymer blend to improve the viscoelastic property of methyl methacrylate acrylonitrile butadiene styrene (MABS). A multi-phase binary polymer blend was prepared by melt mixing in a twin screw extruder with three different weight ratios (10, 20, and 30 wt%) with a dynamically vulcanized alloy consisting mostly of fully cured ethylene propylene diene rubber (EPDM) particles encapsulated in a polypropylene (PP) matrix trade name Santoprene and an engineered styrene based thermoplastic elastomer trade name VDT to enhance the viscoelastic property of the blends. The compatibility and performance of the binary blend were studied by differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), Fourier transform infrared (FT-IR) spectroscopy, nuclear magnetic resonance (NMR), laser microscopy, scanning transmission electron microscopy (STEM) and tensile analysis. The DMA analysis of the samples revealed that the damping performance was significantly increased with the incorporation of the elastomeric phase into the MABS matrix. In addition, the morphological analysis revealed that VDT is more compatible with MABS compared to Santoprene. The NMR and FT-IR analysis further supported the reason for higher compatibility of VDT and MABS blend. The improvement of the damping properties has been observed with the increased wt % of the VDT and Santoprene in the blends.     

Rubber modification of unsaturated polyester resin with core–shell rubber particles: Effect of shell composition

Poly(butyl acrylate)/poly(vinyl acetate‐co‐methyl methacrylate) PBA/P(VAc‐co‐MMA) core–shell rubber particles with various shell compositions, i.e., VAc/MMA weight ratios, were used to toughen unsaturated polyester. The morphology and surface‐free energy of the rubber particles were determined by transmission electron microscopy (TEM) and contact angle measurements, respectively. The effect of shell structure on the dispersion state of rubber particles inside the unsaturated polyester resin was studied by scanning electron microscopy and TEM. Increasing MMA units in the shell changed the particle dispersion state from small agglomerates or globally well‐dispersed particles to large aggregates in the cured‐resin matrix. For the blends that contain 5 wt% rubber, the highest un‐notched impact toughness, stress‐intensity factor (K_IC), and fracture energy (G_IC) were observed for the blend containing PVAc shell particles. The results showed that by increasing the particle level from 5 to 10 wt%, the highest K_IC and G_IC values were obtained for the blend containing rubber particles with VAc/MMA (80/20 wt/wt) copolymer shell. The crack‐tip damage zone in the neat and rubber‐modified unsaturated polyester resins was observed by means of transmission optical microscopy. In addition, using PVAc shell particles exhibited a minimum reduction in the volume shrinkage and tensile properties of the rubber‐modified resin. POLYM. ENG. SCI., 52:1928–1937, 2012. © 2012 Society of Plastics Engineers     

Modification of Epoxy by a Liquid Elastomer and Solid Rubber Particles

Summary This work covers studies on epoxy resin systems modified with two different rubber phases. The first modification was the use of recycled car tire rubber particles; while in the second one a silicon based liquid elastomer (Tegomer) was mixed with the epoxy resin matrix. In the third method epoxy resin was modified with both solid rubber particles and liquid elastomer together.Mechanical tests showed that these modifications resulted in no significant improvements in the mechanical performance of the epoxy resin system. Fractographic studies indicated that poor interfacial adhesion was occurred between the epoxy matrix and the solid rubber particles, while liquid elastomer resulted in formation of round rubbery domains and some plastic deformation lines in the epoxy matrix. For better improvements interfacial phenomenon will be explored.     

MBS树脂的合成、表征与应用

采用本体聚合方法将苯乙烯、甲基丙烯酸甲酯与丁苯嵌段共聚物接枝合成MBS树脂.研究了引发剂种类、丁苯嵌段共聚物用量对接枝聚合反应和树脂综合性能以及对共聚物的组成微观形态结构的影响,考察了MBS树脂作为增韧剂对PVC的增韧效果.结果表明,三元复合引发剂的接枝效果最好;丁苯嵌段共聚物用量增加,接枝效率提高.MBS起到了良好的增韧作用并基本保持了PVC树脂原有的透光率.     

MBS树脂的合成及表征

采用适时补皂、种子乳液聚合方法合成粒径大、分布窄的SBR胶乳。该胶乳接枝St—MMA共聚单体合成MBS树脂。研究了SBR粒径大小度其分布、MBS玻璃化转变温度以度其微观形态。实验结果表明，MBS树脂具有两个玻璃化转变温度，分别为MBS树脂的橡胶相和树脂相的玻璃化转变温度。且MBS树脂呈现规整的核壳结构。     

Toughening effect of EPDM-graft-methyl methacrylate and styrene (EPDM-g-MMA-St) on methyl methacrylate-styrene copolymer (MS resin)

EPDM-graft-methyl methacrylate and styrene (EPDM-g-MMA-St) was synthesized by solution graft copolymerization of methyl methacrylate (MMA) and styrene(St) onto ethylene-proplene-diene terpolymer (EPDM) in toluene/n-heptane cosolvent using benzoyl peroxide as an initiator. Fourier transform infrared spectroscopy provides a substantial evidence of grafting of MMA and St onto EPDM. EPDM-g-MMA-St/MS resin blends (MES) were prepared by melt blending EPDM-g-MMA-St and MS resin, and the toughening effects of EPDM-g-MMA-St on MS resin were studied. The results showed that the synthesized conditions of EPDM-g-MMA-St influenced the toughening effect of EPDM-g-MMA-St on MS resin. Notched Izod impact strength of MES increased with increasing grafting ratio, grafting chain polarity of EPDM-g-MMA-St, and EPDM content in MES. Differential scanning calorimetry showed that EPDM-g-MMA-St and MS resin are compatible partially and the compatibility improves with increasing grafting chain polarity of EPDM-g-MMA-St. Transmission electron microscopy and scanning electron microscopy analysis showed that the phase structure was “sea-island” structure, and the particle diameter of EPDM-g-MMA-St increased, meanwhile, surface to surface interparticle distance decreased with an increase in EPDM content, which resulted in the toughening mechanism of MES changed into slight shear yielding of matrix from the damage mode of cavitation. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Structure and adhesive properties of epoxy resins modified with acrylic particles

The morphology and physical properties of dicyandiamide (DICY)-cured epoxy resin modified with acrylic particles were studied. We used one homopolymer of methyl methacrylate (MMA) and three copolymers of MMA and glycidyl methacrylate (GMA) [P(MMA-GMA)] containing different amounts of GMA as the acrylic particles. When a mixture of the acrylic particles and the epoxy resin was heated, the particles were swollen with the epoxy resin and thus a soft gel with no fluidity was formed. Further heating to the reaction temperature of the DICY cured the soft gel. The structure of the acrylic particles strongly affected the physical properties of the soft gel and the cured epoxy resin. The cured system containing 5 mol% of GMA showed the best physical properties (impact strength and adhesive property), but there was a tendency for the physical properties to decline with a higher GMA content. We have determined that the GMA content of the acrylic particles affects the concentration of network chains in the system.     

Compositionally-tunable surface nanostructuration of microspheres obtained from a self-stabilizing copolymerization of methylmethacrylate and vinylpyrrolidone

The high differential reactivity of methylmethacrylate (MMA) and vinylpyrrolidone (VP) in standard radical copolymerization allows the one-pot preparation of stable methylmethacrylate (MMA)-based solid particles by a surfactant-free process. The copolymers obtained in methanol exhibit a high compositional heterogeneity and a phase separation at high conversion. Partitioning of copolymer chains between the phases as a function of their composition has been observed, being the dispersed phase rich in copolymers with high content of hydrophobic MMA monomer and the continuous phase rich in copolymers with high content of hydrophilic VP monomer. The addition of water under stirring leads to formation of solid particles. The particles have shown a hierarchical structure composed of micron-size particles decorated with nano-size structures on their surface. The size of the nanostructures depends on the initial MMA/VP feed molar ratio in the copolymerization.     

Characterization of UV curable hybrid hard coating materials prepared by sol-gel method

Using sol-gel method, UV-curable urethane acrylate resin system was hybridized with inorganic silicate network to produce hybrid coating materials with high anti-abrasive property. In preparation of acrylate/SiO₂ hybrid materials, various acrylic reactants with multi-functional groups in addition to urethane acrylate oligomer as the main network former were employed to obtain more densified organic network structure with a high degree of cross-linking. As a silane coupling agent, 3-methacryloxypropyl-trimethoxysilane (MPTMS) was used to promote interfacial attraction between UV-cured organic acrylate resin and inorganic silicate component in the hybrid. The addition of MPTMS offered significant effect on the improvement of phase compatibility between organic and inorganic phases, which resulted in stable and homogeneous morphology with a dispersion of nano-sized fine silica particles. The results of morphological observation, glass transition behavior, and optical transparency for the hybrid gels provided an evidence for the increased interfacial attraction between two phases. From the Taber abrasion test for the hybrid coating films, it was revealed that there existed optimal ranges of inorganic silicate precursor TEOS and silane coupling agent MPTMS contents for the preparation of UV cured acrylate/SiO₂ hybrid with high abrasion resistant property.     

Structure-property relationships in rubber-toughened epoxies

Epoxies toughened with two reactive liquid rubbers, an epoxy-terminated butadiene acrylonitrile rubber (ETBN) and an amino-terminated butadiene acrylonitrile rubber (ATBN), were prepared and studied in terms of their structure property relationships. A two-phase structure was formed, consisting of spherical rubber particles dispersed in an epoxy matrix. A broad distribution of rubber particles was observed in all the materials with most of the particles ranging in size from 1 to 4 μm, but some particles exceeding 20 μm were also found. Impact strength, plane strain fracture toughness (K_IC), and fracture energy (G_IC) were increased, while Young's modulus and yield strength decreased slightly with increasing rubber content and volume fraction of the dispersed phase. Both G_IC and K_IC were found to increase with increasing apparent molecular weight between crosslinks and decreasing yield strength. The increased size of the plastic zone at the crack tip associated with decreasing yield strength could be the cause of the increased toughness. An ATBN-toughened system containing the greatest amount of epoxy sub-inclusion in the rubbery phase demonstrated the best fracture toughness in this series. In the present systems, rubber-enhanced shear deformation of the matrix is considered to be the major toughening mechanism. Curing conditions and the miscibility between the liquid rubber and the epoxy resin determine the phase morphology of the resulting two-phase systems. Kerner's equation successfully describes the modulus dependence on volume fraction for the two-phase epoxy materials.     

Polymer compatibility: Nylon-epoxy resin blends

Dynamic mechanical and differential scanning calorimetric studies of cured blends of alcohol soluble nylon with up to 40 percent epoxy resin indicate that the blends contain three phases: crystalline nylon phase, crosslinked nylon-epoxy resin phase, and crosslinked epoxy resin phase. There are unreacted nylon chains distributed in the former two phases. The crystalline nylon phase is composed of partially reacted nylon chains and a small amount of unreacted nylon chains. Degree of ordering in this phase, both unreacted and partially reacted nylon chains, decreases with increasing epoxy resin content. Stress-strain studies show that stress-induced crystallization in partially reacted nylon chains in the crystalline nylon phase does occur during elongation resulting in the occurrence of a maximum tensile strength (at 5 percent epoxy resin content) as in the case of crosslinked rubber. Lap shear studies using the blend as an adhesive indicate a maximum strength at 30 percent epoxy resin content, implying that adhesion and crosslinking effects due to incorporation of epoxy resin play a major role in the adhesion performance.     

Contribution of physico-chemical properties of interfaces on dispersibility, adhesion and flocculation of filler particles in rubber

Reinforcing fillers are added to elastomeric compounds to improve and adjust several mechanical, dynamical, tribological, etc. properties with respect to different applications, i.e. for automotive tires, or technical rubber goods. Carbon black and precipitated silica are widely used as rubber reinforcing fillers; however, some new classes of nanosized substances like organophilic modified clay or carbon nanotubes are presently intensive studied as possible future filler systems in combination with carbon black or silica.An important parameter for the dispersibility and compatibility of the filler in the polymer matrix of rubber compounds is the surface energy and surface polarity of the solid filler particles. Therefore, we systematically measured and compared the dynamic contact angles of a collection of different filler types (carbon blacks, silica, carbon nanotubes and organoclays) using the Wilhelmy method, whereby the particles were fixed as a thin layer at a double-sided adhesive tape. From the contact angle values the polar and disperse part of the surface energies of the filler particles were calculated by fitting Fowkes formula. For an estimation of the compatibility of the fillers with different types of rubber polymers we additionally analyzed the surface energy and polarity of the gum (unfilled) elastomers. From the evaluated surface energies and polarities, thermodynamic predictors for the dispersibility (enthalpy of immersion), the adhesion between filler particles and polymer matrix in the nanocomposite, and for the flocculation behaviour of the particles in a rubber matrix (difference in the works of adhesion) were derived. These thermodynamic predictors improve considerably the compounding process of novel rubber nanocomposites with respect to target-oriented adjustment of rubber properties.     

Zn(MMA)_2对硫黄硫化天然橡胶性能的影响

甲基丙烯酸锌(Zn(MMA)_2)在自由基存在下可以与橡胶发生接枝和交联反应,在橡胶中引入金属离子键交联结构,发生自聚合反应生成纳米聚盐粒子等,使得硫化橡胶具有多元的交联网络结构和多元的填充网络结构,这使得硫化胶的物理力学性能大大提高。为了获得Zn(MMA)_2所给出的优异性能,需采用过氧化物硫化体系,虽然过氧化物与硫黄并用的体系有很多报道,但是都没有单纯采用过氧化物硫化时的性能好。由于硫黄硫化是不饱和橡胶最广泛采用的硫化体系,因此在硫黄硫化条件下,获得Zn(MMA)_2的优异性能,无疑是非常有意义的。从化学计量角度设计了胶料中硫黄的摩尔用量远远大于Zn(MMA)_2的摩尔用量(14:1/mol:mol)的情况,对比了三种硫化体系(S、Zn(MMA)_2/S、Zn(MMA)_2/S*)硫化天然橡胶的特点。结果表明Zn(MMA)_2/S体系硫化胶料的物理力学性能显著提高,这使在硫黄硫化体系中实现Zn(MMA)_2的优异性能成为可能。论文分析阐述了产生这些结果的原因并提出了可能的机理     

Styrene butadiene rubber/epoxidized natural rubber/carbon filler nanocomposites: microstructural development and cure characterization

Microstructural development of elastomeric nanocomposites based on (50/50 wt%) styrene butadiene rubber (SBR) and epoxidized natural rubber (50 mol% epoxidation, ENR50) as the rubber matrix including two types of carbon fillers, carbon black (CB) and functionalized multiwall carbon nanotube (NH₂-MWCNT), which were prepared through melt mixing, was studied. The results from FTIR analysis show that there is interaction between functional groups on MWCNT surface and the rubber chains. The AFM analysis also indicates good dispersion of filler particles in the rubber phases. FESEM images from cryo-fractured surface of samples have revealed that nanotubes were rarely pulled out of matrix and their diameter increased, resulting from good interaction between MWCNTs and rubber chains. The DMA results confirm good interfacial interaction between them. Furthermore, the reduced difference between the two T_gs of phases (ΔT_g) shows that the incorporation of 3 phr MWCNT into the blend leads to increment in rubber phase compatibility but at higher MWCNT content (5 phr) due to lower Mooney viscosity of SBR phase, MWCNTs tend to remain in this phase. The bound rubber was adopted to characterize the polymer–filler interaction, showing that bound rubber content has an increasing trend with increasing in fillers content. The cure rheometric studies reveal that MWCNTs accelerate the cure process due to the presence of amine groups on the nanotube surface. In addition, the mechanical properties of samples show an increasing trend by increasing nano-filler content.

     

The Effect of Modification of an Epoxy Resin Adhesive with ATBN on Peel Strength

The effects of rubber content, rate of peel and temperature on peel strength of ATBN modified DGEBA based epoxy resin adhesives have been investigated. The fracture surfaces of peel test specimens and the distribution of rubber particles in cured bulk epoxy resin have been observed with SEM and TEM, respectively. The mechanical properties of bulk rubber modified epoxy resin have been also measured. The peel strengths increased with increasing rubber content, peel rate, and decreasing temperature. The peel strengths were superposed as a function of rate and temperature. Plots of the shift factors against temperature gave two straight lines, which followed an Arrhenius relationship. The region of temperature below the intersection of the two straight lines, temperature somewhat lower than T_g of epoxy adhesive, gave markedly high peel strengths and a stick-slip failure due to plastic deformation of the adhesive, and a number of micro holes produced by the rupture of rubber micro particles on the fracture surface. The region of temperature above the intersection gave lower peel strengths and an apparent interfacial failure with ductile fracture of the adhesive, and larger, shallow holes or no holes. From these results, the marked increase of peel strength was concluded to be mainly attributed to the plastic or viscoelastic deformation of epoxy matrix, the strong bond at the interface between rubber particles and epoxy matrix, and the dilation and rupture of a number of rubber particles.     

Morphology and Characterization of Epoxy-acrylate Composite Particles

Summary  Epoxy-acrylate sample was prepared by two-stage feed emulsion polymerization. Gel permeation chromatography (GPC) and Ultraviolet-Visible (UV-Vis) spectra indicated the acrylic and styrene monomer were grafted onto epoxy resin. Transmission electron microscope (TEM) showed that epoxy-acrylate composite particles with different epoxy resin content stained by pH1.5 phosphotungstic acid (PTA) had an obvious core-shell structure, with styrene-acrylate as the core and epoxy resin as the shell. TEM micrographs also showed the acrylate cores concentrically or eccentrically were positioned inside epoxy resin shells, which was consonant with the particle structures designed. But the Epoxy Resin/Methyl Methacrylate (EP/MMA) particles showed a strange quadrangle-like structure and Epoxy Resin/Methyl Methacrylate/ Butyl Acrylate (EP/MMA/BA) particles showed a hexagon-like structure, which were different from the normal particle structures.     

三元乙丙橡胶/聚丙烯动态硫化热塑性弹性体的相态结构

用扫描电镜研究了三元乙丙橡胶(EPDM)聚/丙烯(PP)动态硫化热塑性弹性体(TPV)相态结构的形成过程,探讨了交联密度、制备工艺、螺杆转速对EPDM/PP TPV相态结构的影响。结果表明,采用以酚醛树脂为硫化剂的动态硫化工艺制备的EPDM/PP TPV,其相态结构实现了由EPDM和PP组成的双连续相到以EPDM为分散相、PP为连续相的转变;当硫化剂用量为7份时,橡胶相硫化速率和交联密度最大;当螺杆转速为180 r/m in时,反应性挤出工艺较之密炼机工艺制备的EPDM/PP TPV的橡胶粒子更细小、分散更均匀。     

表面原位化学组合改性Al（OH）3粉体的机理研究

采用表面原位化学组合的方法，在Al（OH）3表面分批结合上甲苯二异氰酸酯（TDI）、烷基酚醛树脂（PF）、丁腈橡胶（NBR）等几种改性剂，形成极性逐渐过渡的梯度界面层。电镜分析表明，Al（OH）3颗粒的平均粒径随改性剂种类的增加依次减小。通过红外光谱、热分析证明了改性剂在Al（OH）3的表面原位形成多层化学键合结构，得到“硬核-软壳”结构的粒子，从而提出表面原位化学组合改性Al（OH）3粉体的微观相界面模型，解释了表面原位化学组合方法改性Al（OH）3填充PVC复合材料具有良好力学性能的原因。     

Preparation of high-performance epoxy-containing silicone rubber via hydrosilylation reaction

A novel epoxy-containing silicone rubber network was constructed by hydrosilylation reaction among the synthesized vinyl-containing epoxy resin prepolymers, vinyl terminated silicone oil and hydrogen-containing silicone oil. The structure of the vinyl-containing epoxy resin prepolymers was characterized by Fourier transform infrared spectroscopy and ¹H nuclear magnetic resonance spectroscopy. Morphology observations revealed that uniform “sea-island” phase separation structure was present in modified silicone rubbers. The compatibility between silicone rubber and epoxy resin was enhanced, thanks to the good dispersion of vinyl-containing epoxy prepolymers in silicone rubber matrix. The adhesion and tensile properties of modified silicone rubbers were greatly enhanced when compared with those of unmodified counterparts. The thermal degradation behavior of cured silicone rubbers was studied using thermogravimetric analysis and thermogravimetric/infrared spectrometry analysis. Results showed that the formation of epoxy-containing silicone rubber network altered the degradation process of silicone rubber, thereby yielding a higher residue at 800 °C under nitrogen atmosphere. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48397.     

PU改性TDE-85/ MeTHPA环氧体系的显微形貌特征研究

本实验选用聚醚二元醇、甲苯二异氰酸酯（TDI）作为原料，合成了聚醚型聚氨酯预聚体。采用该预聚体扩链剂1，4-丁二醇（1，4-BDO）、交联剂三羟甲基丙烷（TMP）对TDE-85／甲基四氢苯酐（MeTHPA）环氧树脂体系行改性。利用扫描电镜分析，探讨了聚氨酯（PU）改性TDE-85／甲基四氢苯酐（MeTHPA）环氧树脂体系结构特征。结果表明，当合成PＵ预聚体的PPG相对分子质量不同时，改性环氧树脂体系的表面形貌随聚氨酯预聚体加入量的变趋势是相同的。当聚氨酯含量较小时，呈明显的“海岛”结构。随着聚氨酯加入量增多到一定量时，两网络互穿程度高，相分离程度不明显，具有互穿网络聚合物结构特征。随着聚氨酯含量的继续增多，相区尺寸明显增大，两相相容变差，相界面变得较清晰。