Mechanical properties and microstructure of acrylonitrile–butadiene rubber vulcanizates reinforced by in situ polymerized phenolic resin

The phenolic resin (PF) was incorporated into acrylonitrile–butadiene rubber (NBR) vulcanizates by in situ polymerization during the vulcanization process. It was found that the tensile strength, tearing strength, and tensile strength (300% elongation) could be considerably enhanced 59.4, 80.2, and 126.4%, respectively, at an optimum PF content of only 15 phr, but the elongation at break and shore A hardness were only slightly affected on the basis of silica‐reinforced NBR vulcanizates. A systematic study of the PF structure formed within the NBR matrix using various experimental schemes and procedures has revealed that the PF resin would form the localized discontinuous three‐dimensional interconnected network structures in the NBR matrix. The substantial reinforcement of PF on the mechanical properties of vulcanized NBR were attributed to the morphology, high flexibility, and moderate stiffness of the PF phases and their excellent bonding with rubbers through “rubber to rubber” and interface layer. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007     

Effect of functionalized elastomer addition on mechanical and interfacial properties of poly (butylene terephthalate)/glass fiber composites

In this study the effect of incorporation of ethylene‐co‐glycidylmethacrylate (GMA)‐co‐n‐butyl acrylate (nBA) terpolymer with an epoxy functional group, on the mechanical performance of short glass fiber (SGF)/Poly (butylene terephthalate) (PBT) composites has been investigated. Tensile test showed that incorporation of rubber phase in PBT/SGF composites results in loss of strength. However impact measurement exhibited an increase in impact strength with an increase in rubber content. Tensile and impact properties are discussed in terms of interfacial shear strength and morphology of composites. Morphological observation by SEM revealed a thin layer of polymer adhering to the surface of glass fibers indicating that epoxy functional group in the modifier reacts with fiber surface and PBT matrix. This reactivity of epoxy functional group is also supported by FTIR observations. The composites are also analyzed for % crystallinity using DSC and a strong correlation is found to exist between interfacial shear strength and % crystallinity. POLYM. COMPOS., 2012. © 2011 Society of Plastics Engineers     

In‐situ polymerized phenolic resin for reinforcement of chloroprene and ethylene–propylene rubber vulcanizates

Phenolic resin (PF) was incorporated into rubbers by in situ polymerization at the vulcanization conditions of rubbers. The PF with a localized three‐dimensional network structure was formed in chloroprene rubber (CR), whereas the fabric PF was formed in ethylene–propylene rubber (EPDM). The study results showed that the PF phase was effective on reinforcing these rubbers. Depending on the morphologies of the formed PF phases, various rubber properties could be significantly enhanced. In the case of CR rubber, the tensile strength, tear strength, and modulus could be considerably enhanced, but the elongation and resilience properties were limitedly affected by PF addition. For EPDM rubber, all mechanical properties were improved, particularly the elongation, about 26% increase. The substantial improvements of mechanical properties of CR and EPDM rubbers were attributed to their morphology, high flexibility, moderate stiffness, and excellent bonding with rubber matrix. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Mechanical properties and deformation behaviors of acrylonitrile‐butadiene‐styrene under Izod impact test and uniaxial tension at various strain rates

Two polybutadiene‐graft‐acrylonitrile‐styrene copolymer (PBD‐g‐SAN) impact modifiers with different rubber particle size were synthesized by seeded emulsion polymerization. Acrylonitrile‐butadiene‐styrene (ABS) blends with a constant rubber concentration of 15 wt% were prepared by blending those impact modifiers and SAN resin. The major focus was the mechanical properties and deformation mechanisms of ABS blends under Izod impact test and uniaxial tension at various strain rates from 2.564 × 10^?4 S^?1 upto 1.282 × 10^?1 S^?1. By the combination of transmission electron microscope and scanning electron microscope, it was concluded that crazes and cavitation coexisted in ABS blends. The deformation mechanisms of ABS blend containing large rubber particles was rubber particles cavitation and shear yielding in the matrix including crazes, and they do not change with the strain rate. Different from ABS blend with large rubber particles, deformation mechanism of ABS with small rubber particles under tensile condition was only involved in shear yielding in the matrix and no crazes were formed. POLYM. ENG. SCI., 2011. © 2011 Society of Plastics Engineers     

The roles of polyacrylate in poly(vinyl chloride)‐lignin composites

A novel method was adopted to improve the adhesion between lignin particles and poly(vinyl chloride) (PVC) matrix in PVC‐lignin composites. Lignin was treated with a polyacrylate, poly(ethyl acrylate‐co‐acrylic acid), and the composites was prepared with PVC and the treated lignin. The mechanical properties and morphology of the composites were investigated, and the roles of polyacrylate in the composites were discussed. The results show that both the tensile and impact strengths of the composites are improved when both the content of carboxyl in polyacrylate and its dosage are low, and the optimum is: yield strength, 24.17 MPa, higher than that of PVC control (21.88 MPa); breaking strength, 33.59 MPa, close to that of PVC control (35.62 MPa); and impact strength, 8.0 kJ m⁻², 31% higher than that of PVC control (6.1 kJ m⁻²). Microscopic morphology analysis suggests that polyacrylate improved the adhesion between lignin particles and PVC matrix. The roles of polyacrylate are as the following: polyacrylate is combined with lignin by hydrogen bond and ester bond, and most of its chains spread into PVC matrix due to its good compatibility with PVC, thereby lignin particles can be well bound with PVC matrix. POLYM. COMPOS., 2011. © 2011 Society of Plastics Engineers     

橡胶改性酚醛树脂的研究

通过冲击试验、热分析、摩擦试验等手段研究了硼改性酚醛树脂、腰果壳油改性酚醛树脂、苯并恶嗪开环聚合酚醛树脂作为摩擦材料基体树脂的各自特点，以及丁腈、羧基丁腈、丁苯、丁苯吡四种橡胶改性硼改性酚醛树脂的效果。结果表明，硼改性酚醛树脂可使纤维与填料较好匹配；羧基丁腈橡胶改性的硼改性酚醛树脂的磨损率最低，综合性能优于其它三种橡胶改性的酚醛树脂。     

Effects of PBO fiber and clay on the mechanical,morphological, and dynamic mechanical properties of NR/HDPE blends

Poly(p‐phenylene‐2,6‐benzobisoksazole) (PBO) and natural rubber (NR)/high density polyethylene (HDPE) composites were melt‐blended in a Haake internal mixer. The tensile strength, tensile modulus, and impact strength increased with fiber loading and optimized at 20%. Incorporation of clay into the NR/HDPE/PBO composites resulted in an improvement of tensile strength for NR/HDPE/PBO composites compared to the systems without clay. However, addition of clay was only effective at low contents (5–7.5%). Additional improvement of tensile strength, tensile modulus, and impact strength of the hybrid composite was observed on addition of liquid natural rubber (LNR). Scanning electron micrographs of the samples had indicated that the presence of clay decreased the domain size of the dispersed phase. Results on dynamic response showed that incorporation of clay and LNR into the composites had increased the storage modulus and reduced the tan δ. The shift of glass transition temperature (T_g) to higher values for composites also indicated good interaction between the fiber and the matrix. POLYM. ENG. SCI., 2011. © 2010 Society of Plastics Engineers.     

Effect of potassium persulfate on graft copolymerization and mechanical properties of cassava starch/natural rubber foams

The aim of this study was to improve the mechanical properties of thermoplastic starch foams prepared from cassava starch blended with natural rubber latex by reactive blending. Potassium persulfate was used as an initiator for graft copolymerization between the starch and natural rubber during baking. The starch–natural rubber graft copolymer (starch‐g‐NR copolymer) was successfully produced during both suspension and melt blending based on ¹H‐NMR and FTIR characterization. Natural rubber increased the flexural modulus of starch/natural rubber foams without potassium persulfate, thus indicating the compatibility of the blends. The starch‐g‐NR copolymer, acting as a compatibilizing agent, enhanced the impact strength of foams, but it did not improve the flexural modulus. This may be due to the potassium persulfate decreasing the molecular weight of the natural rubber. Relative humidity also played an important role on the mechanical properties. Foams became more ductile at higher relative humidities. Since foam density increased with an increasing natural rubber content, the specific impact strength was also considered. A soil burial test showed that the cassava starch foams and foams containing 15 pph of natural rubber were fully biodegraded within 8 and 18 weeks, respectively. The starch‐g‐NR copolymer delayed biodegradation of foams and foams containing high natural rubber content, i.e., 35 pph, showed a low ability to be biodegraded. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

The toughening effect and mechanism of styrene‐butadiene rubber nanoparticles for novolac resin

In this article, phenolic nanocomposites were prepared using styrene–butadiene rubber (SBR) nanoparticles with an average particle size of about 60 nm as the toughening agent. The mechanical and thermal properties of phenolic nanocomposites and the toughening mechanism were studied thoroughly. The results showed that when adding 2.5 wt % SBR nanoparticles, the notched impact strength of phenolic nanocomposites reached the maximum value and was increased by 52%, without sacrificing the flexural performance. Meanwhile, SBR nanoparticles had no significant effect on the thermal decomposition temperature of phenolic nanocomposites. The glass‐transition temperature (T_g) of phenolic nanocomposites shifted to a lower temperature accompanying with the increasing T_g of loaded SBR, which showed there was a certain compatibility between SBR nanoparticles and phenol‐formaldehyde resin (PF). Furthermore, the analysis of Fourier transform infrared spectroscopy and X‐ray photoelectron spectroscopy indicated that there existed a weak chemical interaction between SBR nanoparticles and the PF matrix. The certain compatibility and weak chemical interaction promoted the formation of a transition layer and improved the interfacial bonding, which might be important reasons for the great enhancement of the toughness for phenolic nanocomposites. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41533.     

马来酸酐接枝天然橡胶在废报纸粉填充聚氯乙烯材料中的应用

研究了马来酸酐接枝天然橡胶（MNR）作为改性剂，对废报纸粉（PF）填充聚氯乙烯（PVC）复合材料的力学性能和热学性能的影响。研究结果表明，MNR可以较好地改善PF与PVC基体的相容性，显著提高材料的冲击强度。当PF用量（质量份）为5份、MNR为4份时PF／PVC复合材料的综合性能最好，其拉伸强度为48．8MPa，缺口冲击强度达10．1kJ／m^2，后者比改性前提高了87％。热重分析表明：PF／MNR／PVC复合材料的耐热性比纯PVC树脂有所提高。而PF／PVC复合材料的维卡软化温度随着PF填充量的增加而提高，但随着MNR的增加而略有降低。冲击断面扫描电镜分析证实MNR改善了报纸粉与基体树脂的相容性。     

Research of styrene‐butadiene rubber/silicon‐aluminum oxides nanotube binary nanocomposites

A novel silicon‐aluminum oxides (Si‐Al) nanotubes with length ranging from 500 to 1000 nm were introduced to fabricate the styrene‐butadiene rubber (SBR)/Si‐Al nanotube binary nanocomposites. Scanning electron microscope observation showed the Si‐Al nanotubes up to 20 parts per hundred parts of rubber (phr) loading level were dispersed well in SBR matrix. Mechanical properties tests, thermogravimetry analysis and dynamic mechanical thermal analysis revealed that the Si‐Al nanotubes have the effects on improving shore A hardness, tensile strength, tear strength, initial decomposition temperature, and storage modulus while lower the maximum loss factor (tan δ) of the SBR/Si‐Al nanotube binary nanocomposites. FTIR spectra analysis showed that new Si O bond was generated between the hydroxyl group of Si‐Al nanotube and the coupling reagent Si69. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Mechanisms of plastic deformation in biodegradable polylactide/poly(1,4‐cis‐isoprene) blends

Polylactide (PLA), a main representative of biodegradable and made from renewable resources polymers, is surprisingly brittle at ambient temperature. In this article it is investigated how to increase its toughness by a strategy called “rubber toughening” using poly(1,4‐cis‐isoprene), a major component of natural rubber, which is immiscible with PLA, could be well dispersed in PLA matrix and is biodegradable. Immiscible blends of PLA with poly(1,4‐cis‐isoprene) were prepared by melt blending and their properties were studied and optimized. Incorporation of as low as 5 wt % of rubber increased the strain at break of compression molded film during uniaxial drawing, and also improved its tensile impact strength by 80%. The complex mechanism of plastic deformation in the blends leading to improvement of ductility and toughness was revealed. The rubbery particles initiated crazing at the early stages of deformation, as evidenced by transmission and scanning electron microscopy and also by small angle X‐ray scattering. Crazing was immediately followed by cavitation inside rubber particles, which further promoted shear yielding of PLA. The sequence of those mechanisms was proven by microscopic investigation. All three elementary mechanisms acting in the sequence indicated are responsible for surprisingly efficient toughening of PLA by a major component of natural rubber. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Physical properties and cure characteristics of natural rubber/nanoclay composites with two different compatibilizers

The effects of epoxidized natural rubber (ENR) and maleic anhydride‐grafted polybutadiene (PB‐g‐MA) as compatibilizers to rubber formulations with and without organo‐modified layered silicates are investigated. The physical properties and curing characteristics of composites are studied by moving die rheometer, rubber process analyzer, tensile, tear, and hardness testing. The state of organoclay intercalation was determined by X‐ray diffraction method. The addition of compatibilizers, especially ENR 50, results in further intercalation or exfoliation of the organoclay that increased the clay dispersion in the rubber matrix. ENR 50 with organo‐modified clay improves the physical properties and changes the curing profile. The addition of PB‐g‐MA without organoclay increases the tensile strength (σ_max) by increasing the stock viscosity of the rubber compound. Interestingly, simultaneous increase in hardness and σ_max is achieved in the presence of both compatibilizers, a characteristic that is difficult to achieve and sometimes required in rubber processing. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Influence of the tert‐dodecyl mercaptan content in poly(acrylonitrile‐butadiene‐styrene) on properties of chlorinated polyvinyl chloride/poly(acrylonitrile‐butadiene‐styrene) blends

A series of poly(acrylonitrile‐butadiene‐styrene) (ABS) grafting modifiers were synthesized by emulsion grafting poly(acrylonitrile‐styrene) (SAN) copolymer onto polybutadiene (PB) latex rubber particles. The chain transfer reagent tert‐dodecyl mercaptan (TDDM) was used to regulate the grafting degree of ABS and the molecular weight of SAN copolymers. By blending these ABS modifiers with Chlorinated polyvinyl chloride (CPVC) resin, a series of CPVC/ABS blends were obtained. The morphology, compatibility, and the mechanical properties of CPVC/ABS blends were investigated. The scanning electron microscope (SEM) studies showed that the ABS domain all uniformly dispersed in CPVC matrix. Dynamic mechanical analyses (DMA) results showed that the compatibility between CPVC and SAN became enhanced with the TDDM content. From the mechanical properties study of the CPVC/ABS blends, it was revealed that the impact strength first increases and then decreases with the TDDM content, which means that the compatibility between CPVC and the SAN was not the only requirement for maximizing toughness. The decreasing of tensile strength and the elongations might attribute to the lower entanglement between chains of CPVC and SAN. POLYM. ENG. SCI., 2011. © 2011 Society of Plastics Engineers     

Deformation mechanism of polystyrene toughened with sub‐micrometer monodisperse rubber particles

Core–shell polybutadiene‐graft‐polystyrene (PB‐g‐PS) rubber particles with different ratios of polybutadiene to polystyrene were prepared by emulsion polymerization through grafting styrene onto polybutadiene latex. The weight ratio of polybutadiene to polystyrene ranged from 50/50 to 90/10. These core‐shell rubber particles were then blended with polystyrene to prepare PS/PB‐g‐PS blends with a constant rubber content of 20 wt%. PB‐g‐PS particles with a lower PB/PS ratio (≤70/30) form a homogeneous dispersion in the polystyrene matrix, and the Izod notched impact strength of these blends is higher than that of commercial high‐impact polystyrene (HIPS). It is generally accepted that polystyrene can only be toughened effectively by 1–3 µm rubber particles through a toughening mechanism of multiple crazings. However, the experimental results show that polystyrene can actually be toughened by monodisperse sub‐micrometer rubber particles. Scanning electron micrographs of the fracture surface and stress‐whitening zone of blends with a PB/PS ratio of 70/30 in PB‐g‐PS copolymer reveal a novel toughening mechanism of modified polystyrene, which may be shear yielding of the matrix, promoted by cavitation. Subsequently, a compression‐induced activation method was explored to compare the PS/PB‐g‐PS blends with commercial HIPS, and the result show that the toughening mechanisms of the two samples are different. Copyright © 2006 Society of Chemical Industry     

Fabrication of polypropylene blends with excellent low‐temperature toughness and balanced toughness‐rigidity by a combination of EPR and SEEPS

To overcome serious rigidity depression of rubber‐toughened plastics and fabricate a rigidity‐toughness balanced thermoplastic, a combination of styrene‐[ethylene‐(ethylene‐propylene)]‐styrene block copolymer (SEEPS) and ethylene‐propylene rubber (EPR) was used to toughen polypropylene. The dynamic mechanical properties, crystallization and melting behavior, and mechanical properties of polypropylene (PP)/EPR/SEEPS blends were studied in detail. The results show that the combination of SEEPS and EPR can achieve the tremendous improvement of low‐temperature toughness without significant strength and rigidity loss. Dynamic mechanical properties and phase morphology results demonstrate that there is a good interfacial strength and increased loss of compound rubber phase comprised of EPR component and EP domain of SEEPS. Compared with PP/EPR binary blends, although neither glass transition temperature (T_g) of the rubber phase nor T_g of PP matrix in PP/EPR/SEEPS blends decreases, the brittle‐tough transition temperature (T_bd) of PP/EPR/SEEPS blends decreases, indicating that the increased interfacial interaction between PP matrix and compound rubber phase is also an effective approach to decrease T_bd of the blends so as to improve low‐temperature toughness. The balance between rigidity and toughness of PP/EPR/SEEPS blends is ascribed to the synergistic effect of EPR and SEEPS on toughening PP. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45714.     

Facile preparation of nylon 6 nanocomposites based on clay reinforcement and core‐shell latex toughening: Morphology,properties, and impact fracture behavior

This work is focused on a facile route to prepare a new type of nylon 6‐based nanocomposites with both high fracture toughness and high strength. A series of nylon 6‐matrix blends were prepared via melting extrusion by compounding with poly (methyl methacrylate‐co‐butadiene‐co‐styrene) (MBS) or poly(methyl methacrylate‐co‐methylphenyl siloxane‐co‐styrene) (MSIS) latices as impact modifier and diglycidyl ether of bisphenol‐A (DGEBA) as compatibilizer. Layered organic clay was also incorporated into above nylon 6 blends for the reinforcement of materials. Morphology study suggests that the MBS or MSIS latex particles could achieve a mono‐dispersion in nylon 6 matrix with the aid of DGEBA, which improves the compatibilization and an interfacial adhesion between the matrix and the shell of MBS or MSIS. High impact toughness was also obtained but with a corresponding reduction in tensile strength and stiffness. A moderate amount of organic clay as reinforcing agent could gain a desirable balance between the strength, stiffness and toughness of the materials, and tensile strength and stiffness could achieve an improvement. This suggests that the combination of organic clay and core‐shell latex particles is a useful strategy to optimize and enhance the properties of nylon 6. Morphology observation indicates that the layered organic clay was completely exfoliated within nylon 6 matrix. It is found that the core‐shell latex particles and the clay platelets were dispersed individually in nylon 6 matrix, and no clay platelets were present in MBS or MSIS latex particles. So the presence of the clay in nylon 6 matrix does not disturb the latex particles to promote high fracture toughness via particle cavitation and subsequent matrix shear yielding, and therefore, provides maximum reinforcement to the polymer. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Some interesting phenomena in silica‐filled HNBR with the addition of silane coupling agent

Hydrogenated nitrile rubber (HNBR)/silica nanocomposites were prepared by in‐situ modification dispersion technology, and the silane coupling agent γ‐methacryloxypropyl trimethoxy silane (KH570) was chosen to promote the interfacial strength between silica particles and HNBR matrix and further improve the dispersion of silica particles. Rubber Process Analyzer (RPA2000) was used to test the Payne effect of HNBR/silica compounds, from which some interesting phenomena were found: the Payne effect became stronger after KH570 was added to HNBR/silica compound at room temperature, which was a contrary result compared to SBR/silica system. However, after stored for a month at room temperature, the Payne effect weakened, which was contrary to the traditional phenomenon of storage hardening of filled rubber. All these results are related to filler–filler interaction and filler–rubber interaction. The modulus at small strain amplitude of HNBR/silica compound with KH570 gradually decreased with the increase of times of circulatory strain sweep but that of compound without KH570 had almost no change, which was explained by Fourier Transform Infrared (FTIR) results that the reaction between silica and KH570 almost completed at the test condition: 80°C and about 1 h. The effects of silane amount, heat‐treated temperature and time on the Payne effect of compounds and the mechanical properties of vulcanizates were also investigated. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Effect of blending sequence on the morphology and properties of polyamide 6/EPDM‐g‐MA/epoxy blends

The ternary blends of polyamide 6/maleated ethylene‐propylene‐diene rubber/epoxy (PA6/EPDM‐g‐MA/EP) were prepared by a twin‐screw extruder with four different blending sequences. With the variation of blending sequence, the ternary blends presented distinct morphology and mechanical properties because of different interactions induced by various reactive orders. The addition of epoxy could increase the viscosity of the PA6 matrix, but a considerably larger size of the dispersed rubber phase was observed while first preblending PA6 with epoxy followed by blending a premix of PA6/EP with EDPM‐g‐MA, which was attested by rheological behaviors and SEM observations. It was probably ascribed to the fact that the great increase of the interfacial tension between the matrix and rubber phase aroused a great coalescence of rubber particles. The presence of epoxy in the rubber phase reduced the rubber's ability to cavitate so that the toughening efficiency of the EPDM‐g‐MA was decreased. The results of mechanical testing revealed that the optimum blending sequence to achieve balanced mechanical properties is blending PA6, EPDM‐g‐MA, and epoxy simultaneously in which the detrimental reactions might be effectively suppressed. In addition, thermal properties were investigated by TG and DSC, and the results showed that there was no distinct difference. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Curing characteristics and mechanical properties of rattan‐powder‐filled natural rubber composites as a function of filler loading and silane coupling agent

Curing characteristics, tensile properties, morphological studies of tensile fractured surfaces using scanning electron microscopy (SEM), and the extent of rubber filler interactions of rattan‐powder‐filled natural rubber (NR) composites were investigated as a function of filler loading and silane coupling agent (CA). NR composites were prepared by the incorporation of rattan powder at filler loading range of 0–30 phr into a NR matrix with a laboratory size two roll mill. The results indicate that in the presence of silane CA, scorch time (t_s2), and cure time (t₉₀) of rattan‐powder‐filled NR composites were shorten, while, maximum torque (M_H) increased compared with NR composites without silane CA. Tensile strength and tensile modulus of composites were enhanced whereas elongation at break reduced in the presence of silane CA mainly due to increase in rubber‐filler interaction. It is proven by SEM studies that the bonding between the filler and rubber matrix has improved. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012