Surface modification of nanocrystalline cellulose and its application in natural rubber composites

As a biopolymer with high mechanical strength, nanocellulose was generally considered as a green filler for reinforcing polymer. In this study, nanocrystalline cellulose (NCC) isolated from softwood pulp was successfully modified by cetyltrimethyl ammonium bromide (CTMAB), a cationic surfactant, and the modified nanocrystalline cellulose (m-NCC) was used to reinforce natural rubber (NR). In this composite architecture, it was found that when the filler content was 5 or 10 phr, the surface modification of NCC improved the dispersion state of NCC in NR matrix and the interfacial interaction between NR and NCC. Therefore, the NR/m-NCC composites exhibited outstanding mechanical properties, and its tensile strength, elongation at break and tear strength was increased by 132.8, 20, and 66.1%, respectively, compared to pristine NR composites. Besides, the modified NCC could accelerate the vulcanization and improve wet-skid resistance and aging resistance of NR composites. It is envisioned that the modified NCC has the potential to be generalized to manufacturing other polymer matrix composites strengthened with nanocellulose.     

Fly ash particles and precipitated silica as fillers in rubbers. I. Untreated fillers in natural rubber and styrene–butadiene rubber compounds

In this study, we investigated the effects of untreated precipitated silica (PSi) and fly ash silica (FASi) as fillers on the properties of natural rubber (NR) and styrene–butadiene rubber (SBR) compounds. The cure characteristics and the final properties of the NR and SBR compounds were considered separately and comparatively with regard to the effect of the loading of the fillers, which ranged from 0 to 80 phr. In the NR system, the cure time and minimum and maximum torques of the NR compounds progressively increased at PSi loadings of 30–75 phr. A relatively low cure time and low viscosity of the NR compounds were achieved throughout the FASi loadings used. The vulcanizate properties of the FASi‐filled vulcanizates appeared to be very similar to those of the PSi‐filled vulcanizates at silica contents of 0–30 phr. Above these concentrations, the properties of the PSi‐filled vulcanizates improved, whereas those of the FASi‐filled compounds remained the same. In the SBR system, the changing trends of all of the properties of the filled SBR vulcanizates were very similar to those of the filled NR vulcanizates, except for the tensile and tear strengths. For a given rubber matrix and silica content, the discrepancies in the results between PSi and FASi were associated with filler–filler interactions, filler particle size, and the amount of nonrubber in the vulcanizates. With the effect of the FASi particles on the mechanical properties of the NR and SBR vulcanizates considered, we recommend fly ash particles as a filler in NR at silica concentrations of 0–30 phr but not in SBR systems, except when improvement in the tensile and tear properties is required. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 2119–2130, 2004     

Thiol‐containing ionic liquid for the modification of styrene–butadiene rubber/silica composites

To introduce thiol–ene chemistry in the modification of composites by ionic liquid (IL), a novel functional IL, 1‐methylimidazolium mercaptopropionate (MimMP), was synthesized and investigated as a modifier for styrene–butadiene rubber/silica composites. MimMP could be hydrogen‐bonded with silica and react with the double bonds of rubber chains via thiol–ene chemistry. The filler networking, curing behavior, filler dispersion, crosslink density, and mechanical performance were fully studied. The filler networking in the uncured rubber compounds was effectively restrained. The vulcanization was largely accelerated by MimMP. The interfacial interaction was quantitatively evaluated and found to consistently increase with increasing MimMP. The mechanical performance and abrasion resistance of the modified vulcanizates improved considerably. The remarkable improvements were mainly ascribed to the improved interfacial structure comprised of MimMP–silica hydrogen bonding and MimMP–rubber covalent bonds via thiol–ene chemistry. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Synthesis of polychloroprene–silica composites by sol‐gel method in the presence of modified polychloroprene containing triethoxysilyl group

Triethoxysilyl‐modified polychloroprene (CR) latex was synthesized by the emulsion copolymerization of 2‐(3‐triethoxysilylpropyl)‐1,3‐butadiene with chloroprene. This latex was mixed with unmodified CR latex and tetraethoxysilane to obtain CR–silica composites by sol‐gel reaction in the latex. SEM observation showed that the silica particles in unvulcanized composites have various diameters ranging from 0.1 to 0.6 μ m, and their size became larger with the decrease of the silica content. Vulcanized CR–silica composites showed that the tensile modulus and tear strength improved with an increase of the amount of modified CR. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 1545–1552, 2005     

Simultaneously reduced viscosity and enhanced strength of liquid silicone rubber/silica composites by silica surface modification

Silica is the most widely‐used filler to reinforce liquid silicone rubber (LSR), but the high viscosity of LSR/silica suspension significantly limits its processing flexibility. To balance the processibility and reinforcing efficiency of LSR/silica systems, two kinds of enols (propenol and 1‐undecylenyl alcohol) and a saturated alcohol (1‐undecylic alcohol) were employed to modify the silica surface. Various rheological tests were carried out to investigate the processibility as well as filler networking and crosslinking processes of the modified systems. Tensile tests were also adopted to verify the reinforcing effect. It was found that surface modification of silica by 1‐undecylenyl alcohol could significantly reduce the viscosity of its suspension with LSR. Meanwhile, the mechanical strength of LSR could be largely enhanced by six times with 10 wt % modified silica. This work will merit design and production of LSR materials with balanced processibility and mechanical performance. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45544.     

Composition,tensile properties,and dispersion of polypropylene composites reinforced with viscose fibers

The reinforcement mechanics of viscose‐fiber‐reinforced polypropylene (PP) composites were studied. The effect of the coupling agent, maleated polypropylene (MAPP), was of special interest. The fibers, coupling agent, and PP were extruded and injection‐molded. The composition, mechanical properties, fracture morphology, and dispersion of the composites were examined. Thermogravimetric analysis showed that the fiber content in the tensile specimens varied slightly with the sample location; however, the differences in the values were within 1.0%. Scanning electron microscopy images of the fracture surfaces of the composites showed that the surfaces of the composites without MAPP were covered with fibers pulled out from the matrix. A lack of adhesion further appeared as a cracked matrix–fiber interface. A new scanning thermal microscopy method, microthermal analysis, was used to study the dispersion of the fibers in the composites. Local thermal analyses gave further information about the location of the fibers. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 2676–2684, 2004     

Promoting the dispersibility of silica and interfacial strength of rubber/silica composites prepared by latex compounding

The dispersibility of precipitated silica and its interfacial interaction with rubber matrix can affect the performances of tires which is a difficult problem to be solved. A well-dispersed silica dispersion was obtained through ball milling and modification process followed by heat treatment to enhance the properties of NR composites prepared by latex compounding. Benefiting from the modifier Si-747, the well-dispersed silica/NR composite (Silica-MSH-C) shows excellent tensile strength of 30.8 ± 0.5 MPa, which is 17.6 ± 3.8% higher than latex compounding pure silica/NR composite (Silica-C) and 21.7 ± 4.3% higher than traditional mechanical blending pure silica/NR composite (T-Silica-C). The tan delta values indicate that Silica-MSH-C has better dynamic properties and also has stronger interface strength according to swelling tests, heat capacity curves and Mooney-Rivlin equation. The molecular dynamics (MD) simulation further shows the binding energy between NR and Si-747 modified SiO₂ is 58.88 Kcal/mol larger than the value of NR and pure silica.     

针状硅酸盐的表面改性及其橡胶复合材料的力学性能

考察了不同改性剂及其用量对针状硅酸盐(FS)表面改性和FS／橡胶复合材料力学性能的影响。结果表明,FS存在结构羟基,其中一些羟基具有化学反应活性。硅烷偶联剂、钛酸酯偶联剂和十六烷基三甲基溴化铵对FS具有较好的改性效果。硅烷偶联剂Si69改性FS增强效果最好,其最佳用量为2．4质量份;改性FS用量的增加改善了复合材料的力学性能;改性FS对丁苯橡胶、三元乙丙橡胶、丁腈橡胶、羧基丁腈橡胶具有良好的增强效果。     

Using a silanized silica nanofiller to reduce excessive amount of rubber curatives in styrene‐butadiene rubber

In recent years, the rubber industry has come under pressure to improve health and safety at work, minimize damage to the environment, reduce costs, and increase competitiveness. Rubber compounds contain additives including curing chemicals, which are hazardous and harmful. Reducing their use or eliminating them altogether will be beneficial to rubber compounders and manufacturers of rubber articles. A styrene‐butadiene rubber (SBR) was cured and reinforced with a high loading of precipitated amorphous white silica nanofiller. The silica surfaces were pretreated with bis(3‐triethoxysilylpropyl) tetrasulfide (TESPT), which is a sulfur‐bearing bifunctional organosilane to chemically adhere silica to the rubber. The chemical bonding between the filler and rubber was optimized via the tetrasulfane groups of TESPT by adding accelerator and activator. The rubbers were subsequently cured and their hardness, tensile strength, elongation at break, stored energy density at break, tearing energy, tensile modulus, Young's modulus, and bound rubber content were measured. This study showed that using the filler in combination with a sulfur‐donor accelerator was the most efficient method for curing and reinforcing the rubber. This led to a significant reduction in the use of the curing chemicals, a faster curing cycle, and very good mechanical properties for the rubber vulcanizate. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

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     

Influences of purification and surface treatment of sugarcane bagasse ash on mechanical properties of natural rubber composites

Attempts to use bagasse ash (BA) as a filler in natural rubber (NR) have been made. Acidolysis/alkaline extraction method was used to purify BA. The purified BA (PBA) was subsequently characterized by various techniques such as X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and so forth. After the purification, PBA had a lower particle size and a higher specific surface area. XRD results showed that silica was the main composition of PBA while FTIR results revealed the existence of hydroxyl groups on the PBA surface. The reinforcement magnitude of PBA in NR was subsequently evaluated both without and with the addition of surface modifying agents, namely, bis-3-triethoxysilylpropyl tetrasulfide (TESPT) and epoxidized natural rubber (ENR). Due to its large particle size, PBA acted as a semi-reinforcing filler for NR, that is, the small increases of hardness, modulus and tensile strength were observed in the presence of PBA. As TESPT and ENR could improve the extent of rubber-filler interaction, mechanical properties of the NR vulcanizates filled with PBA-TESPT and PBA-ENR were slightly higher than those of the PBA-filled NR vulcanizate. For instance, tensile strength exhibited approximately 22% increase after the surface treatment. In this study, both PBA-TESPT and PBA-ENR showed comparable degree of reinforcement.     

Dichlorocarbene modification of natural rubber and its role as a modifier in blends of natural rubber and hydrogenated nitrile rubber

Dichlorocarbene modification of natural rubber (NR) carried out by alkaline hydrolysis of chloroform in presence of cetyl trimethyl ammonium bromide as phase‐transfer catalyst was investigated. Extent of chemical reaction was characterized by estimation of chlorine content and FTIR studies. Rate of dichlorocarbene addition depends on the time and temperature of reaction. Reaction carried out at 60°C for 2 h yielded a material with a chlorine content of 15%. Chemical modification of NR was accompanied by introduction of chlorine through cyclopropyl ring to the main chain of NR as revealed from FTIR studies. As level of chlorination increased, the physical nature of NR changed from a soft flexible state to a hard nontacky form. Blends of NR with hydrogenated nitrile rubber (HNBR) containing three to seven parts of dichlorocarbene‐modified NR (DCNR) of chlorine content 15% could be prepared by conventional mill mixing. Incorporation of DCNR into blends of NR and HNBR promoted polar interaction between the chlorine segments and acrylonitrile segments of the blend as shown from the shift in characteristic IR absorption peaks and shift in T_g from DSC studies. As a consequence, DCNR acted as an interface modifier in blends of NR and HNBR. Blends of NR and HNBR containing DCNR showed a considerable improvement in cure behavior, physical properties, and ageing characteristics in oil, ozone, and high temperature compared to pure blends of NR and HNBR. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 4401–4409, 2006     

Preparation and properties of polyimide/silica hybrid composites based on polymer‐modified colloidal silica

A new type of polyimide/silica (PI/SiO₂) hybrid composite films was prepared by blending polymer‐modified colloidal silica with the semiflexible polyimide. Polyimide was solution‐imidized at higher temperature than the glass transition temperature (T_g) using 3,3′,4,4′‐biphenyltetracarboxylic dianhydride (BPDA) and 4,4′‐diaminodiphenyl ether (ODA). The morphological observation on the prepared hybrid films by scanning electron microscopy (SEM) pointed to the existence of miscible organic–inorganic phase, which resulted in improved mechanical properties compared with pure PI. The incorporation of the silica structures in the PI matrix also increased both T_g and thermal stability of the resulting films. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 2053–2061, 2006     

改性粉煤灰填充废胶粉复合材料研究

以废胶粉（URP）为基体相,粉煤灰（FA）为增强相,烷偶联剂为相容性制备了粉煤灰/废胶粉复合材料。研究了废胶粉和粉煤灰的最佳用量和偶联剂的用量,混合方式和最佳的硫化条件。通过扫描电镜（SEM）和红外光谱（FT-IR）分析了粉煤灰/废胶粉试样的结构和形貌。结果表明：用Si-69对粉煤灰的改性效果好于KH-550。废胶粉最佳用量为100份,粉煤灰40份,Si-69 1.0份。最佳的初混方式为热混,偶联剂先与粉煤灰混合,而后再与废胶粉混合。最佳硫化条件为：温度160℃,压力8MPa,时间25 min。Si-69/FA/URP比KH-550/FA/URP的相容性要好。硅烷偶联剂中的Si—OH和粉煤灰表面的—OH发生脱水缩合,形成了Si—O键;偶联剂的有机端和废胶粉形成了C—H键,从而改善了FA/URP复合材料相容性和力学性能。     

超细粉碎硅灰石的表面改性及在橡胶中的应用

由粒度、SEM和长径比分析得出"气流磨"是硅灰石超细粉碎的最佳设备.通过对超细硅灰石粉体的表面化学改性效果的研究,确定了最佳工艺条件:改性剂为硬脂酸,改性剂用量2%,改性时间15～20min,改性温度70℃.并探讨了超细改性硅灰石在橡胶中的应用.     

Enhancing the mechanical properties of styrene–butadiene rubber by optimizing the chemical bonding between silanized silica nanofiller and the rubber

The reinforcing effect of a large amount of synthetic precipitated amorphous white silica nanofiller on the mechanical properties of styrene–butadiene rubber was studied. The silica surfaces were pretreated with bis(3‐triethoxysilylpropyl)tetrasulfane (TESPT). TESPT is a bifunctional organosilane that chemically adheres silica to rubber and also prevents silica from interfering with the reaction mechanism of sulfur cure in the rubber. The silica particles were fully dispersed in the rubber and the chemical bonding between the rubber and filler was optimized by the incorporation of accelerator and activator in the rubber. This study showed that the mechanical properties of the rubber vulcanizate improved substantially when the filler was added. The addition of elemental sulfur affected the rubber properties, although there was no overall advantage, as some properties improved and others deteriorated. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Two advanced styrene‐butadiene/polybutadiene rubber blends filled with a silanized silica nanofiller for potential use in passenger car tire tread compound

Styrene‐butadiene rubber (SBR) and polybutadiene rubber (BR) were mixed together (75:25 by mass) to produce two SBR/BR blends. The blends were reinforced with a precipitated amorphous white silica nanofiller the surfaces of which were pretreated with bis(3‐triethoxysilylpropyl)‐tetrasulfide (TESPT). TESPT is a sulfur‐bearing bifunctional organosilane that chemically bonds silica to rubber. The rubbers were primarily cured by using sulfur in TESPT and the cure was optimized by adding non‐sulfur donor and sulfur donor accelerators and zinc oxide. The hardness, Young's modulus, modulus at different strain amplitudes, tensile strength, elongation at break, stored energy density at break, tear strength, cyclic fatigue life, heat build‐up, abrasion resistance, glass transition temperature, bound rubber and tan δ of the cured blends were measured. The blend which was cured with the non‐sulfur donor accelerator and zinc oxide had superior tensile strength, elongation at break, stored energy density at break and modulus at different strain amplitudes. It also possessed a lower heat build‐up, a higher abrasion resistance and a higher tan δ at low temperatures to obtain high‐skid resistance and ice and wet‐grip. Optimizing the chemical bonding between the rubber and filler reduced the amount of the chemical curatives by approximately 58% by weight for passenger car tire tread. This helped to improve health and safety at work and reduce damage to the environment. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Deformation and fracture behaviors of vinylester/fly ash composites

In this work, the deformation and fracture behaviors of a commercial vinylester resin reinforced with fly ash were investigated. Tensile, compressive, and fracture tests were performed on the matrix and the composites with different ash content. Most composites exhibited improved stiffness, tensile strength, and fracture properties in comparison to the vinylester matrix. From scanning electron microscopic analysis of fracture surfaces, the toughening mechanisms of crack pinning, crack deflection, particle debonding, and localized shear yielding were identified. In addition, the dependence of tensile and compressive modulus and fracture energy toward ash content was adequately fitted by simple models available in the literature. From the results of these models and energy‐dispersive X‐ray spectroscopy analysis, some interaction between vinylester and ash seemed to exist. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Fly‐ash particles and precipitated silica as fillers in rubbers. II. Effects of silica content and Si69‐treatment in natural rubber/styrene–butadiene rubber vulcanizates

This article explored the possibility of using silica from fly‐ash particles as reinforcement in natural rubber/styrene–butadiene rubber (NR/SBR) vulcanizates. For a given silica content, the NR : SBR blend ratio of 1 : 1 (or 50 : 50 phr) exhibited the optimum mechanical properties for fly‐ash filled NR/SBR blend system. When using untreated silica from fly‐ash, the cure time and mechanical properties of the NR/SBR vulcanizates decreased with increasing silica content. The improvement of the mechanical properties was achieved by addition of Si69, the recommended dosage being 2.0 wt % of silica content. The optimum tensile strength of the silica filled NR/SBR vulcanizates was peaked at 10–20 phr silica contents. Most mechanical properties increased with thermal ageing. The addition of silica from fly‐ash in the NR/SBR vulcanizates was found to improve the elastic behavior, including compression set and resilience, as compared with that of commercial precipitated silica. Taking mechanical properties into account, the recommended dosage for the silica (FASi) content was 20 phr. For more effective reinforcement, the silica from fly‐ash particles had to be chemically treated with 2.0 wt % Si69. It was convincing that silica from fly‐ash particles could be used to replace commercial silica as reinforcement in NR/SBR vulcanizates for cost‐saving and environment benefits. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007     

Preparation and performance of oleylamine modified silica-reinforced natural rubber composites

Oleylamine (OA) modified silica (SiO₂-g-OA) was prepared using γ-(2,3-epoxypropoxy) propytrimethoxysilane (KH560) and OA, silica/natural rubber (NR) and SiO₂-g-OA/NR composites were prepared by mechanical blending in an internal mixer, and SiO₂-g-OA was characterized by Fourier transform infrared spectroscopy, thermal gravimetric analyzer, and contact angle analyzer. The mechanical properties, abrasion resistance, curing characteristics, Payne effect, and morphology of silica/NR and SiO₂-g-OA /NR composites were investigated using universal testing machine, Akron abrasion tester, rubber processing analyzer, and scanning electron microscope, respectively. The results showed that SiO₂-g-OA became more hydrophobic and had better compatibility with NR. Moreover, SiO₂-g-OA/NR had weaker Payne effect, better vulcanization performance, and more excellent mechanical properties. As the content of filler was more than 30 phr, SiO₂-g-OA/NR had lower rolling resistance and higher wet skid resistance. Compared with silica modified by other coupling agents, SiO₂-g-OA had the best reinforcement effect on NR.