马来酸酐接枝天然橡胶对纤维素纤维增强天然橡胶复合材料的增容作用

在无引发剂的熔融状态下,利用剪切力将马来酸酐接枝于天然橡胶分子链上,并将马来酸酐接枝天然橡胶(MNR)作为增容剂添加到纤维素纤维增强天然橡胶复合材料中,研究其对复合材料性能的影响.结果表明,在熔融状态下利用剪切力能够发生自由基反应或Diels-Alder反应,将马来酸酐接枝于天然橡胶分子链上而制得MNR.添加了MNR的纤维增强天然橡胶硫化胶的物理机械性能,尤其是定伸强度比未添加MNR的硫化胶有明显提高,应力弛豫程度减小;扫描电镜分析也说明添加MNR使填料与橡胶基质之间有了更强的界面黏合力.     

Reinforcement of maleated natural rubber by precipitated silica

Graft copolymers of maleic anhydride and natural rubber or so‐called maleated natural rubbers (MNRs) were prepared in a molten state with varying maleic anhydride contents from 4 to 10 phr. In this work, the filler–filler and filler–rubber interactions of the MNR and precipitated silica were investigated. The MNR compounds containing 40 phr of silica both with and without 9 wt % of silane coupling agent were prepared. By increasing the maleic anhydride contents, the Mooney viscosity and cure times were increased, but the torque differences and cure rate indices were decreased. Bound rubber was increased with increasing maleic anhydride content, indicating an increase of filler–rubber interaction. In case of the compounds without silane, the MNR with 6 phr of maleic anhydride showed the lowest filler–filler interaction as indicated by a decrease of storage modulus upon an increase of strain in the filled compound i.e., Payne effect. This MNR compound also yielded the optimum mechanical properties. It has been demonstrated that a use of MNR with appropriate maleic anhydride content can reduce filler–filler interaction dramatically and hence improve a silica dispersion, as confirmed by SEM micrographs, resulting in an enhancement of the mechanical and dynamical properties. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Effect of glycidyl methacrylate-grafted natural rubber on physical properties of polylactic acid and natural rubber blends

Natural rubber (NR) was melt blended with polylactic acid (PLA) at various ratios using an internal mixer. The impact strength and elongation at break of PLA/NR blend dramatically increased with increasing NR content up to 10% (w/w). Glycidyl methacrylate-grafted natural rubber (NR-g-GMA) was used as a compatibilizer for PLA/NR blend. The effects of content and %grafting of NR-g-GMA on mechanical properties of PLA/NR blend were studied. The experimental result showed that the addition of NR-g-GMA in PLA/NR blend significantly improved impact strength and elongation at break of PLA/NR blend when compared with that of neat PLA and PLA/NR blend without NR-g-GMA. The impact strength and elongation at break of PLA/NR blend increased with increasing NR-g-GMA content up to 1% (w/w). Moreover, with increasing % grafting of NR-g-GMA in PLA/NR blend up to 4.35, the impact strength and elongation at break of the blend increased. Morphological and thermal property of PLA, PLA/NR, and PLA/NR/NR-g-GMA were elucidated as well. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Effects of fillers,maleated ethylene propylene diene diene rubber,and maleated ethylene octene copolymer on phase morphology and oil resistance in natural rubber/nitrile rubber blends

The phase morphology and oil resistance of 20/80 NR/NBR blends filled with different types of fillers and copolymers were investigated. In the case of filler effect, N220, N330, and N660 carbon blacks with different particle sizes were used. Additionally, the blends filled with nonblack‐reinforcing fillers, that is, precipitated and silane‐treated silica, were investigated. To study the compatibilization effect, maleated ethylene propylene diene rubber (EPDM‐g‐MA) and maleated ethylene octene copolymer (EOR‐g‐MA) were added to the blends. The results revealed that the addition of filler, either carbon black or silica, to the blend caused a drastic decrease in NR dispersed phase size. Carbon blacks with different particle sizes did not produce any significant difference in NR dispersed phase size under the optical microscope. Silica‐filled blends showed lower resistance to oil than did the carbon black–filled blends. In addition, it was determined that neither EOR‐g‐MA nor EPDM‐g‐MA could act as a compatibilizer for the blend system studied. The oil resistance of the blends with EPDM‐g‐MA is strongly affected by the overall polarity of the blend. In the case of EOR‐g‐MA, the oil resistance of the blends is significantly governed by both overall polarity of the blend and phase morphology. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 1156–1162, 2003     

Effects of palm ash loading and maleated natural rubber as a coupling agent on the properties of palm‐ash‐filled natural rubber composites

Natural rubber composites were prepared by the incorporation of palm ash at different loadings into a natural rubber matrix with a laboratory‐size two‐roll mill (160 × 320 mm²) maintained at 70 ± 5°C in accordance with the method described by ASTM D 3184–89. A coupling agent, maleated natural rubber (MANR), was used to improve the mechanical properties of the natural rubber composites. The results indicated that the scorch time and cure time decreased with increasing filler loading, whereas the maximum torque exhibited an increasing trend. Increasing the palm ash loading increased the tensile modulus, but the tensile strength, fatigue life, and elongation at break decreased. The rubber–filler interactions of the composites decreased with increasing filler loading. Scanning electron microscopy of the tensile fracture surfaces of the composites and rubber–filler interaction studies showed that the presence of MANR enhanced the interfacial interaction of the palm ash filler and natural rubber matrix. The presence of MANR also enhanced the tensile properties and fatigue life of palm‐ash‐filled natural rubber composites. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Effect of addition of polyoxypropylenediamine on the morphology and mechanical properties of maleated polypropylene/maleated rubber blends

Blends of maleated polypropylene and maleated ethylene propylenediene (EPDM-g-MA) were compounded in a twin-screw extruder with a polyetheramine (PEA), polyoxypropylenediamine, as a compatibilizer. The effect of the compatibilizer concentration and molecular weight on the physical properties was investigated. FTIR data showed that the addition of the compatibilizer caused an imide linkage to form between the amine functionality on the PEA and the maleic anhydride (MA) functionality on both the polypropylene (PP) and the rubber backbone. This bond improved the interfacial adhesion between the rubber and the PP matrix, resulting in an improvement in the toughness of the blends. Other improvements in the physical properties of the blends with a compatibilizer compared to the blends without it included notched Izod impact, elongation at yield, and elongation at break. The optimum improvement in properties was found when the level of the compatibilizer was about 3 wt %. These changes in properties correlated well with the morphology observed via optical and scanning electron microscopy. © 1998 John Wiley & Sons, Inc. J Appl Polm Sci 68: 1451–1472, 1998     

Epoxidation of natural rubber latices: Methods of preparation and properties of modified rubbers

Studies in the epoxidation of natural rubber latices are described. Investigated epoxidation routes include the use of bromohydrin intermediates, hydrogen-peroxide-catalyzed systems, and preformed peracetic acid. The latter reagent allows almost quantitative epoxidation of natural rubber up to high modification levels with no detectable side reactions. Kinetic studies show that the peracetic acid epoxidation is second order in peracid and rubber hydrocarbon with an overall activation energy of 56.2 kJ/mol. Epoxidation leads to a progressive increase in T_g and polymer density with increase in modification level. The effect of modification on solvent swelling and mechanical properties of the DICUP-crosslinked rubbers are reported.     

New crosslinked polyurethane elastomers with various physical properties from natural rubber derivatives

New hydroxytelechelic cis‐1,4‐oligoisoprenes exhibiting variable values and distributions of the hydroxyl functionality were successfully prepared. The synthesis reactions involved chemical modifications of carbonyl telechelic cis‐1,4‐polyisoprene, which was obtained by controlled degradation of synthetic or natural rubber. These new oligomers were reacted with toluene diisocyanate to elaborate crosslinked polyurethane elastomers. The thermomechanical properties of the prepared polyurethanes were investigated. The results show a strong relationship between the chemical structures and properties. This work mainly shows the potentiality of making new crosslinking polyurethane materials with controlled and various properties from natural rubber, a renewable resource. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Rheology,cure characteristics,physical and mechanical properties of tire tread reclaimed rubber/natural rubber compounds

This work aimed to examine the effect of addition of tire‐tread reclaimed rubber on the properties of two natural rubber (NR) compounds with respect to the reclaimed rubber concentration and mastication time, the properties of interest including rheological and cure characteristics, physical and mechanical properties. The results under the test conditions suggested that Mooney Plasticity and shear viscosity increased with reclaimed rubber content, but decreased with mastication time. The greater the molar mass of the natural rubber the higher the sensitivity to the change in compound viscosity due to mastication and reclaimed rubber content. The die swell was more dependent on the reclaimed rubber than the molar mass of the rubbers. The cure rate and scorch time were found to increase and decrease with reclaimed rubber content, respectively, whereas the cure time was independent of the reclaimed rubber content. For vulcanized rubbers, it was also observed that 100% modulus of the rubber increased with reclaimed rubber content, but this was not the case for tensile stress and elongation at break. The hardness and heat buildup properties of the vulcanizates increased with reclaimed rubber content whereas the tear strength became independent of the reclaimed rubber. The findings in this work suggested that the variations in the rheological and cure characteristics for the unvulcanized rubber were very much dependent on the molar mass of the rubber whereas the mechanical properties for the vulcanized rubber were influenced by crosslink density. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 1723–1731, 2003     

Some physical characteristics of double-networked natural rubber

A double-networked natural rubber (DNNR) was prepared by a “two-step crosslinking” method, in which the crosslinking was achieved while the natural rubber was in a stretched condition. The swelling behavior, tensile properties, creep, recovery, and permanent set were investigated. Generally, the observed mechanical properties of DNNR, such as the Young's modulus, tensile strength, toughness, creep, recovery, and permanent set, were considerably improved as the residual extension was increased. They were, however, rather inferior to those of a single-networked natural rubber and showed a minimum at a lower residual extension of about 1.55. The degree of crosslinking and elongation at break were not greatly affected by the residual extension. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 65:917–924, 1997     

Ionic elastomer blends of zinc salts of maleated natural rubber and carboxylated nitrile rubber: Effect of grafted maleic anhydride

Zinc neutralized maleated natural rubbers (Zn‐MNR) were prepared by solution grafting and neutralization with zinc acetate in one‐step. It was later used for blending with carboxylated nitrile rubber (XNBR) in the composition of 50/50 parts by weight. The effect of grafted anhydride content (1.2, 1.6, 2.0, and 2.5% wt of NR) on the tensile properties of ionic rubber blends (Zn‐MNR/XNBR) was investigated. The tensile strength of the ionic blends was found to be greater than those of pure rubbers. The modulus, tensile, and tear strength of the blends dramatically increased with increasing levels of grafted anhydride. The ionic rubber blends also possessed superior physical properties compared to those of the corresponding nonionic rubber blends (MNR/XNBR). Dynamic mechanical thermal analysis and scanning electron microscopic studies were performed to verify the process of mixing. Fourier transform infrared spectroscopic studies were carried out to characterize the nature of specific intermolecular interactions between Zn‐MNR and XNBR chain segments. The results indicated that the ion‐ion (Zn⁺ ‐COO^?) interactions between Zn‐MNR and XNBR are formed at the interface, which provides the mean of compatibilization in the ionic rubber blends. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Cure characteristics and mechanical properties of hydrogenated natural rubber/natural rubber blends

The cure characteristics and mechanical properties of blends consisting of hydrogenated natural rubber (HNR) and natural rubber (NR) blends were investigated. The HNR/NR blends at 50/50 wt ratio were vulcanized using various cure systems: peroxide vulcanization, conventional vulcanization with peroxide, and efficient vulcanization with peroxide. The HNR/NR vulcanizates cured by the combination of peroxide and sulfur donor (tetramethylthiuram disulfide, TMTD) in the efficient vulcanization with peroxide exhibited the best mechanical properties. It was also found that the hydrogenation level of HNR did not affect the tensile strength of the vulcanizates. The tensile strength of the blends decreased with increasing HNR content because of the higher incompatibility to cause the noncoherency behavior between NR and HNR. However, the HNR/NR vulcanizate at 50/50 wt ratio showed the maximum ultimate elongation corresponding to a co‐continuous morphology as attested to by scanning electron micrographs. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

HEMA接枝改性天然胶乳的制备及其粘接性能研究

以甲基丙烯酸羟乙酯(HEMA)作为天然胶乳(NRL)的接枝改性剂,采用乳液聚合法制备了NR-g-HEMA[HEMA接枝NR(天然橡胶)]胶乳;然后以此为基体,并以水溶性松香树脂为增黏树脂、邻苯二甲酸二丁酯(DBP)为增塑剂等,制备相应的NR-g-HEMA胶粘剂;最后,用该胶粘剂压制胶合板,并对胶合板的粘接性能进行了测定。结果表明:采用单因素试验法优选出制备NR-g-HEMA胶乳的最佳工艺条件为m(干态单体)∶m(NRL)∶m(引发剂)∶m(活化剂)∶m(交联剂)=20∶100∶0.2∶0.2∶0.1、反应时间为8 h和反应温度为16℃,此时相应胶合板的剪切强度(1.88 MPa)符合Ⅲ类胶合板的指标要求。     

Understanding the reinforcing efficiency of waste eggshell‐derived nano calcium carbonate in natural rubber composites with maleated natural rubber as compatibilizer

Calcium carbonate nanoparticles were synthesized from eggshell waste using ball mill treatment and characterized by Fourier transform infrared (FTIR), X‐ray diffraction (XRD), and field‐emission scanning electron microscopy (FESEM) analysis. Then, waste eggshell‐derived nano calcium carbonate (WESNCC) was used as filler to reinforce natural rubber (NR) composites with and without the presence of maleated natural rubber (MNR) as compatibilizer. MNR‐compatibilized NR/WESNCC composites showed remarkable enhancement in the torque difference, tensile, and thermal properties as compared to either uncompatibilized NR/WESNCC composites or unfilled NR system. Crosslinking degree measurements indicated excellent interfacial interaction between NR matrix and WESNCC in presence of MNR as compatibilizer. A probable mechanism is suggested to explain the interaction between NR matrix and WESNCC in the presence of MNR. This study provides unique way to develop WESNCC‐based rubber composites for future industrial and engineering application. POLYM. ENG. SCI., 59:1428–1436 2019. © 2019 Society of Plastics Engineers     

Grafting of natural rubber for preparation of natural rubber/unsaturated polyester resin miscible blends

Graft copolymers of natural rubber and polystyrene were synthesized by free‐radical grafting of styrene monomer onto natural rubber in latex form. The obtained graft copolymers and unsaturated polyester (UPE) resin were mixed and cast at room temperature using methyl ethyl ketone peroxide as an initiator and Co‐octoate as an accelerator. The samples prepared from ungrafted natural rubbers exhibited the aggregation of the rubber component, whereas the samples prepared from grafted natural rubbers showed good dispersion of the rubber component in a glassy matrix of UPE resin. It was found that the amount of polystyrene grafted onto natural rubber and the graft copolymer content in polymer blend significantly affect the mechanical properties of the blend samples. An increase in the amount of hard and brittle polystyrene in glassy matrix of UPE resin overshadowed the impact‐absorbing ability of the rubber component, causing the impact strength of the blend samples to be lower than that of pure UPE resin. On the other hand, an increase in easily elongated uncrosslinked rubber molecules, as the graft copolymer content in blend samples increased, resulted in a decrease in their flexural strength. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 1496–1503, 2004     

Influence of chloroacetate group on physical properties of natural rubber and its interaction with fillers

Filler–rubber composites were prepared by mixing chloroacetated natural rubber (CNR) with silica, carbon black (CB), or calcium carbonate using a two‐roll mill. The interactions between the CNR and fillers, including silica, carbon black, and calcium carbonate, were characterized based on glass transition temperature (T_g) and shear storage modulus (G′). The results showed that both the T_g and G′ values of the CNR‐Si composite were found to be higher than those of the CNR–CB and CNR–CaCO₃ composites, indicating the existence of the CNR and silica interaction. The outstanding direct interaction between the CNR rubber matrix and silica without using a coupling agent was believed to be due to hydrogen bonds that formed between the hydroxyls of the silanol groups of silica and the carbonyls in the chloroacetate groups of CNR molecules. Moreover, it was also found that silica dispersed and distributed in the CNR matrix much better than in the natural rubber matrix. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43076.     

Synthesis and properties of hydrogenated natural rubber

A series of hydrogenated natural rubbers, HNRs, were prepared by homogenous hydrogenation using H₂ gas with a rhodium catalyst (chlorotris(triphenylphosphine)rhodium) in toluene. The HNRs were linear polymers with molecular weights greater than 800,000. These rubbers were vulcanized using sulfur and peroxide compounds. Vulcanized 100% HNR has a low glass transition temperature (T_g = ?43°C) and excellent abrasion resistance, and is resistant to oxidation and ozonolysis ageing. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 3957–3963, 2007     

聚丙烯酸钠制备吸水膨胀天然橡胶的研究

采用氧化还原引发体系,引发丙烯酸钠聚合并接枝到天然橡胶分子链上,并采用硫磺硫化体系进行硫化,制备高性能吸水橡胶。通过考察单体用量和多种配合剂对吸水橡胶的吸水和力学性能的影响,得出单体用量的增加引起吸水橡胶的物理机械性能的降低,但吸水性能得到了提高。FTIR分析可知,产物是天然橡胶和聚丙烯酸钠的接枝共聚物。TG分析表明天然橡胶和聚丙烯酸钠的接枝共聚物的热力学稳定性得到很大程度的提高。     

Effect of grafted maleic anhydride content and recyclability of dynamically cured maleated natural rubber/polypropylene blends

Maleated natural rubbers (MNRs) were prepared using various levels of maleic anhydride (MA) at 4, 6, 8, 10, and 12 phr. Dynamically cured 60/40 MNR/PP blends with phenolic‐modified polypropylene (Ph‐PP) compatibilizer at a loading level of 5 wt % of PP were prepared by melt mixing process using sulfur vulcanization system. The influence of the level of MA on properties of the thermoplastic vulcanizates (TPVs) was studied. It was found that the mixing torque, apparent shear stress, shear viscosity, tensile strength, and hardness properties increased with increasing levels of the MA or grafted succinic anhydride groups in the MNR molecules. This is attributed to an increase in chemical interaction and reaction between methylol groups in the Ph‐PP molecules and polar functional groups in the MNR molecules upon increasing levels of the grafted succinic anhydride groups. As a consequence, compatibilizing block copolymers of MNR and PP blocks were formed. The block copolymers were capable of compatibilizing with MNR and PP blend components via the respective blocks. Recyclability of the MNR/PP TPVs was also studied. It was found that, after processing through a number of cycles by injection molding and extrusion processing, the TPV exhibited marginal decreases in mechanical properties. This corresponded to slightly increasing size of the dispersed vulcanized rubber domains. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Physical properties of natural rubber/organoclay nanocomposites compatibilized with epoxidized natural rubber

Onium ion‐modified montmorillonite (organoclay) was melt compounded with natural rubber (NR) in an internal mixer and cured by using a conventional sulfuric system. Epoxidized natural rubber with 50 mol % epoxidation (ENR 50) was used in 10 parts per hundred rubber (phr) as a compatibilizer. The effect of organoclay with different filler loading up to 10 phr was studied. Cure characteristics were determined by a Monsanto MDR2000 rheometer, whereas the tensile, compression, and tear properties of the nanocomposites were measured according to the related ASTM standards. While the torque maximum and torque minimum increased slightly, both scorch time and cure time reduced with the incorporation of organoclay. The tensile strength, elongation at break, and tear properties went through a maximum (at about 2 phr) as a function of the organoclay content. As expected, the hardness, moduli at 100% (M100) and 300% elongations (M300) increased continuously with increasing organoclay loading. The compression set decreased with incorporation of organoclay. The dispersion of the organoclay in the NR stocks was investigated by X‐ray diffraction and transmission electron microscopy. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 1083–1092, 2006