Stress relaxation in short jute fiber-reinforced nitrile rubber composites

Stress relaxation measurements in tension have been made on nitrile rubber vulcanizates containing short jute fibers. The effects of strain level, bonding system (silica-resorcinol-hexa), fiber orientation, fiber content, temperature, and prestraining on the rate of stress relaxation have been investigated. Existence of a relaxation mechanism within the first 200 s is reported.     

Preparation,morphology and properties of natural rubber composites filled with untreated short jute fibres

Green composites were obtained by incorporation of short jute fibres in natural rubber matrix using a laboratory two-roll mill. The influence of untreated fibre content (1, 2.5, 5, 7.5 and 10 phr) on the mechanical properties, dynamic mechanical properties, swelling properties was examined. The behaviour of prepared green composites under cyclic compression was also investigated. Fibre dispersion in rubber matrix was studied by scanning electron microscopy. The highest tensile strength (21.1 MPa) and highest tear strength (39.9 N/mm) were found for composites containing 2.5 and 5 phr of short jute fibres, respectively. The results also suggested that increasing fibrous filler content resulted in increasing of tensile moduli 100, 200 and 300 % of elongation and hardness, and decreasing of rebound resilience and abrasion resistance of prepared jute/natural rubber composites. The cyclic compression test showed that increasing the amount of short jute fibres in the rubber matrix is related to increase of the energy dissipated in the composite. The incorporation of short jute fibres into the rubber matrix improves the stiffness of the composites, and it is related to the interaction between fibre surface and rubber matrix. The application of short fibres in higher amounts leads to formation of fibre agglomerates reducing the mobility of the rubber polymer chains. The mentioned agglomerates act as defects in rubber matrix, which caused decreasing of some properties, e.g. relative elongation at break.     

Short jute fiber-reinforced polypropylene composites: Effect of compatibilizer

Jute fibers were chopped to approximately 100 mm in length and then processed through a granulator having an 8-mm screen. Final fiber lengths were up to 10 mm maximum. These fibers along with polypropylene granules and a compatibilizer were mixed in a K-mixer at a fixed rpm, 5500, and dumped at a fixed temperature, 390°F, following single-stage procedure. The fiber loadings were 30, 40, 50, and 60 wt %, and at each fiber loading, compatibilizer doses were 0, 1, 2, 3 and 4 wt %. The K-mix samples were pressed and granulated. Finally, ASTM test specimens were molded using a Cincinnati injection molding machine. At 60% by weight of fiber loading, the use of the compatibilizer improved the flexural strength as high as 100%, tensile strength to 120%, and impact strength (unnotched) by 175%. Remarkable improvements were attained even with 1% compatibilizer only. Interface studies were carried out by SEM to investigate the fiber surface morphology, fiber pull-out, and fiber–polymer interface. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 69: 329–338, 1998     

短切碳纤维对天然橡胶/顺丁橡胶复合材料性能的影响

以天然橡胶(NR)和顺丁橡胶(BR)为基料,以短切碳纤维(SCF)为添加剂,制备了SCF/NR/BR复合材料,考察了SCF用量对NR/BR的摩擦性能及力学性能的影响。结果表明,SCF可增强NR/BR基体的强度,增大其硬度。在NR/BR混合胶中加入15份SCF可以降低混合胶的摩擦系数,减少混合胶的磨损量,提高混合胶的耐磨性能。SCF增强的NR/BR在摩擦过程中发生了磨粒磨损和黏着磨损,形成了卷曲磨屑。     

不同种类短纤维对天然橡胶/丁苯橡胶复合材料性能的影响

分别以尼龙66短纤维、芳纶短纤维及聚酯短纤维作为增强剂,天然橡胶（NR）和丁苯橡胶（SBR）作为基体制备了短纤维增强NR/SBR（短纤维/NR/SBR）复合材料,采用正交实验方法研究了短纤维种类、长度及用量对短纤维/NR/SBR复合材料的拉伸性能、硬度、撕裂强度的影响。结果表明,经过浸渍处理后的尼龙66短纤维与NR/SBR基体之间的结合最为紧密;浸渍处理后的尼龙66短纤维可以有效提高NR/SBR复合材料的拉伸强度,在一定范围内,随着短纤维长度和用量的增加,短纤维/NR/SBR复合材料的拉伸强度有所提高;短纤维的加入提高了NR/SBR复合材料的撕裂强度和硬度,但扯断伸长率则有所下降。     

Stress relaxation in short sisal-fiber-reinforced natural rubber composites

Stress relaxation behavior of chemically treated short sisal fiber-reinforced natural rubber composite was studied. The effect of bonding agent, strain level, fiber loading, fiber orientation, and temperature has been studied in detail. The existence of a single relaxation pattern in the unfilled stock and a two-stage relaxation mechanism for the fiber-filled composite is reported. The relaxation process is influenced by the bonding agent, which indicated that the process involved fiber-rubber interface. The rate of stress relaxation increased with fiber loading, whereas it decreased with aging. © 1994 John Wiley & Sons, Inc.     

Coating of jute with natural rubber

Jute fabric was coated with natural rubber to develop double‐texture rubberized waterproof fabric and fabric‐reinforced rubber sheeting for hospitals. The vulcanization of such natural‐rubber‐coated flexible composites at 120°C for 3 h produced optimum effects. The jute/natural‐rubber composite was much superior to a conventional polyester/natural‐rubber composite for producing such double‐texture rubberized fabric with respect to the fabric‐to‐natural‐rubber adhesion, breaking strength, tear strength, abrasion resistance, puncture resistance, and biodegradability. For fabric‐reinforced rubberized sheeting, the jute/natural‐rubber composite was superior to a conventionally used cotton/natural‐rubber composite with respect to the fabric‐to‐natural‐rubber adhesion, breaking strength, tear strength, and abrasion resistance. However, for both applications, the jute‐based products were commonly found to be less extensible, heavier, and thicker. Unsaturation in the lignin fraction of jute established a chemical linkage with the unsaturation of natural rubber via sulfur at the jute/natural‐rubber interface. An examination of the surface morphology of uncoated and coated jute fabrics by scanning electron microscopy revealed a good degree of deposition and filling even in the intercellular regions of jute by a cohesive mass of natural rubber, which remained unseparated from the fiber, when mechanical force was applied. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 484–489, 2005     

Short silk fiber-reinforced polychloroprene rubber composites

The reinforcement of polychloroprene rubber by short silk fiber has been studied in the presence of three different dry bonding systems, viz.: (a) “cohedur RK–cohedur A–silica”; (b) “cohedur RK–cohedur A–carbon black”; (c) “resorcinol–hexamethylenetetramine–silica.” The degree of fiber–rubber adhesion of the different bonding systems follows the order (a) > (b) > (c). Scanning electron microscopy studies of tensile, tear, abrasion, and flex failed surfaces of both unfilled and fiber–filled composites containing “cohedur–silica” bonding system have also been made in order to gain an insight to the mechanism of failure.     

天然短纤维增强橡胶复合材料的研究进展

介绍了短纤维的预处理方法,总结了短纤维在橡胶中的混合、分散及取向状态,综述了短纤维-橡胶复合材料在轮胎、胶带和胶管中的应用进展,并提出了复合材料的研究方向.     

填料和测试温度对天然橡胶蠕变性能的影响

本文探讨了填料和测试温度对天然橡胶蠕变性能的影响。实验结果表明：随着炭黑用量的减少,NR的蠕变性能先变差后变好,并与交联密度分析的结果相吻合;测试温度越高,NR的蠕变性能越好。     

Effect of coal gangue/carbon black/multiwall carbon nanotubes hybrid fillers on the properties of natural rubber composites

The objective of this study was to investigate three kinds of filler with completely different morphology on mechanical properties of natural rubber (NR). Coal gangue (CG) are derived from natural deposits are composed principally by illite and quartz. CG, carbon black (CB), and multiwalled carbon nanotube (CNT) were used as hybrid fillers in NR. CNTs were dispersed into NR latex by ultrasonic irradiation and then the mixed latex were coagulated to obtain the CNTs/NR masterbatch, then mechanical mixing method was employed to prepare the CG/CB/CNTs/NR composites. The addition of CG, CB, and CNTs to NR was varied with the total filler loading fixed at 35 phr. The mechanical properties of NR composites were studied in terms of tensile and dynamic mechanical analysis (DMA). The results showed that the tensile strength and modulus 300% (M300) of all hybrid samples were higher than the composites only loaded CG; and the highest tensile strength of NR loaded with hybrid fillers achieved at sample of loading amount of CG 17.5, CB 15.5, and CNTs 2 phr, whose M300 and elongation at break was obviously higher than that of only CB loaded NR composites; The inclusion CG improves the tensile strength of NR without the sacrifice of its extensibility, while CB and CNTs brings together the enhancement in the ultimate strength and the reduction in the extensibility. DMA results revealed that the existence of CG can improve the dispersion of CB and CNTs in NR matrix. POLYM. COMPOS., 37:3083–3092, 2016. © 2015 Society of Plastics Engineers     

白炭黑填充剂对硅橡胶性能的影响

研究了白炭黑对硅橡胶CKTB—Б性能的影响。在胶料中，气相白炭黑的最佳用量为30～40质量份。在使用气相白炭黑的同时加入定量的钛白粉，可提高硫化胶的强度和弹性。     

Tensile properties of short sisal fiber-reinforced polyethylene composites

Sisal fibers (Agave-Veracruz) have been used as reinforcements in low-density polyethylene (LDPE). The influence of the processing method and the effect of fiber content, fiber length, and orientation on tensile properties of the composites have been evaluated. The fiber damage that normally occurs during blending of fiber and polyethylene by the meltmixing method is avoided by adopting a solution-mixing procedure. The tensile properties of the composites thus prepared show a gradual increase with fiber content. The properties also increased with fiber length, to a maximum at a fiber length of about 6 mm. Unidirectional alignment of the short fibers achieved by an extrusion process enhanced the tensile strength and modulus of the composites along the axis of fiber alignment by more than twofold compared to randomly oriented fiber composites. © 1993 John Wiley & Sons, Inc.     

Guayule natural rubber composites: impact of fillers on their cure characteristics,dynamic and mechanical behavior

Guayule natural rubber (GNR) is an alternative resource of Hevea natural rubber (HNR) with 99.9% cis content in its 1,4-polyisoprene chemical backbone. In this study, compounds were formulated independently with four different reinforcing fillers such as carbon black (HAF), precipitated silica (VN3), fume silica (FUM) and nanofly ash (NFA) for the advancement of GNR based products. The cure characteristic, dynamic-mechanical performance and mechanical properties of GNR composite were studied with the reinforcing effect of different fillers on GNR. The cure characteristic results demonstrated that HAF and FUM silica filled compounds had more processing safety than VN3 and NFA filled compounds. Viscoelastic parameters of the vulcanizates were studied by dynamic mechanical analysis to estimate the glass transition characteristics and dynamic behavior. The higher storage modulus of FUM silica vulcanizate was an indication of superior filler reinforcing nature and improved rolling resistance than other filled systems. Additionally, HRTEM analysis also proved the better filler dispersion ability of FUM silica in GNR matrix. The mechanical properties were studied with a variation of each filler loading of 8, 16, and 32 phr in GNR vulcanizates. The tensile strength of each filled system increased with an increase of filler content from 8 to 32 phr. In comparison, FUM silica GNR vulcanizates exhibited better mechanical properties, therefore, it was considered as a better structure-performance composite than those of HAF, VN3 and NFA filled composites.

     

Effect of chemical treatment on the thermal properties of hybrid natural fiber-reinforced composites

The main objective of this work is to study the effect of chemical treatment on the thermal properties of hybrid natural fiber-reinforced composites (NFRCs). Different chemical treatments [i.e., alkalized and mixed (alkalized+ silanized)] were used to improve the adhesion between the natural fibers (jute, ramie, sisal, and curauá) and the polymer matrix. A differential scanning calorimetry, thermogravimetry, and a dynamic mechanical analysis were performed to study the thermal properties of hybrid NFRC. It was found that the chemical treatments increased the thermal stability of the composites. Scanning electron microscopy images showed that the chemical treatments altered the morphology of the natural fibers. A rougher surface was observed in case of alkali treated fiber, whereas a thin coating layer was formed on the fiber surface during the mixed treatment. However, for some fibers (i.e., sisal and rami), the chemical treatment has a positive impact on the composite properties, whereas for the jute and curauá composites, the best behavior was found for untreated fibers. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47154.     

粉状填充剂对橡胶复合材料拉断伸长率的影响

以不同粒径的氢氧化镁、轻质碳酸钙和炭黑N110填充SBR、EPDM、NBR和硅橡胶，探讨粉状填充剂（简称粉体）对其填充橡胶复合材料拉断伸长率的影响。结果表明，粉体的表面活性、粒径、分散性、用量以及基体橡胶的拉伸强度和拉断伸长率等因素对橡胶复合材料拉断伸长率的影响存在着竞争关系。粉体的粒径和基体橡胶的交联密度影响橡胶复合材料拉断伸长率随粉体用量增大而提高的幅度。粉体对基体橡胶表现出较强的补强作用时，使橡胶复合材料的拉断伸长率出现峰值的粉体用量较小。与传统观点不同，试验得出大多数情况下填充粉体有利于橡胶复合材料拉断伸长率提高的结论。     

改性天然沸石对橡胶复合材料性能的影响

为了提高沸石在橡胶中的分散，增强沸石与橡胶的界面相互作用，本文采用硝酸（H）和双-（γ-三乙氧基硅基丙基）四硫化物（S）对天然沸石（NZ）进行复合改性（S-HNZ），然后将改性沸石与天然橡胶（NR）混炼制备沸石/天然橡胶复合材料，研究不同改性沸石对天然橡胶性能的影响。采用FTIR、XRD、SEM等测试手段对改性前后NZ的结构进行表征，研究了橡胶复合材料的硫化性能，动态热机械性能（DMA）及力学等性能。结果表明：经酸处理后天然沸石（HNZ）骨架脱铝呈疏水性，且硅烷成功接枝到天然沸石表面。添加S-HNZ的橡胶复合材料焦烧时间和正硫化时间均缩短，硫化反应速率加快；另外，与NR相比，NR/S-HNZ的300%定伸应力和抗拉强度分别提高了46.7%和10.8%；DMA结果显示，NR/S-HNZ储能模量（E''）和玻璃化转变温度（Tg）均高于NR，表明经复合改性后，复合材料的交联密度增加，形成较强的交联网络，极大提高了沸石与橡胶大分子链之间的界面结合力。     

Effect of natural rubber on wood‐reinforced tannin composites

Natural rubber latex was added to composite materials formulated from a quebracho tannin adhesive crosslinked with hexamethylenetetramine and wood flour as a reinforcing filler. The final microstructure of the thermoset modified by the addition of different concentrations of latex was observed by scanning electron microscopy. The flexural and impact behavior of the modified materials was analyzed and related to the final microstructure of the composites. The effect of exposing the materials to humid environments was also evaluated. The measurements indicated that the addition of latex did not significantly reduce water absorption. However, it facilitated the preparation process of samples with low filler contents because of the increased viscosity of the mixture, which inhibited particle settling. On the other hand, the flexural properties increased with the addition of latex‐containing proteins through a reaction similar to tanning in leathers. The impact properties presented a similar trend, with the largest change occurring between 0 and 5% natural rubber in the matrix formulation. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

马来酸酐对聚酰胺6短纤维/天然橡胶复合材料的增容作用

将马来酸酐直接与天然橡胶混炼，得到的马来酸酐-天然橡胶接枝物既能与聚酰胺6短纤维也能与天然橡胶形成良好的结合，有助于提高短纤维增强橡胶复合材料的物理机械性能。