Adhesion and self-adhesion of immiscible rubber blends

Rubber blends of synthetic polyisoprene rubber (IR) and hydrogenated acrylonitrile butadiene rubber (HNBR) are prepared with different compositions. First, DSC results confirm that IR and HNBR are incompatible rubbers. A tensile testing machine equipped with a tack probe test allows us to measure the level of adhesion at rubber blends/glass as well as rubber blends/pure rubber interfaces, for contact times ranging from 0.1 s to a few hours. The adhesive properties of rubber blends were compared with those of pure rubbers. Adhesion energy G of IR/HNBR blends onto glass increases with the IR content in disagreement with a simple law of mixtures because of the influence of bulk properties of blends (morphology and mechanical behaviour). For a given blend, G increases with contact time certainly due to an interfacial reorganisation. Self-adhesion energies G_S of pure rubbers and IR/HNBR blends increase also with contact time, thanks to mainly an interdiffusion phenomenon of the rubber chains through the interface. Self-adhesion energy of blends in contact with pure IR follows a simple law of mixtures as a function of IR content. On the contrary, the variation of self-adhesion energy of these blends in contact with pure HNBR is more complex.     

Unlubricated rolling wear of HNBR/FKM/MWCNT compounds against steel

The rolling friction and wear of the compounds of peroxide‐cured hydrogenated acrylonitrile/butadiene rubber (HNBR) and fluororubber (FKM) (HNBR‐FKM) with and without multiwalled carbon nanotube (MWCNT) contents were studied against steel in orbital rolling ball (steel)‐on‐plate (rubber) test rig (Orbital‐RBOP). The phase structure of the rubber compounds in the presence and absence of MWCNT was studied by dynamic mechanical thermal analysis (DMTA), transmission electron and atomic force microscopy (TEM and AFM, respectively). It was established that HNBR formed the matrix in which micron‐scaled FKM domains were dispersed. MWCNT was preferentially embedded in the HNBR. The network‐related and surface tension properties of the rubber compounds were derived from DMTA tests and contact angle measurements, respectively. The Martens hardness of the rubbers was also measured. The coefficient of friction (COF) and specific wear rate (W_s) were determined in Orbital‐RBOP. Blending of HNBR with FKM increased the COF slightly and decreased the specific wear rate prominently when compared with pure HNBR. Additional MWCNT reinforcement (10 parts per hundred part rubber, phr) of the HNBR and HNBR‐FKM further increased the COF and at the same time improved the wear resistance. The wear mechanisms were concluded by inspecting the worn surfaces in scanning electron microscope (SEM) and discussed as a function of FKM and MWCNT modifications. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Cure characteristics and mechanical properties of styrene-butadiene rubber/hydrogenated acrylonitrile-butadiene rubber/silica composites

Composites of styrene butadiene rubber (SBR), hydrogenated acrylonitrile–butadiene rubber (HNBR) and silica were prepared. Sulfur (S), dicumyl peroxide (DCP) and a combination of S and DCP (M) were used as curing agents, respectively. The morphology of the composites with different blend ratio was examined to correlate with observations on mechanical properties by scanning electron microscopy. The effects of blend ratio and curing systems on the curing characteristics and mechanical properties, such as stress–strain behavior, tensile strength, elongation at break and hardness of SBR/HNBR/Silica composites, were studied. Composites prepared by M curing systems showed comparatively better mechanical properties, wet traction and rolling resistance than S and D curing systems. The tensile strength, tear strength, and elongation at break were improved by adding HNBR for M curing systems. The wet traction of the vulcanizates containing HNBR was better than that of the vulcanizates without HNBR. A relatively uniform dispersion of silica was observed for SBR/HNBR/silica compositions compared with SBR/silica composites.     

ACM/FKM并用胶的性能研究

研究了不同并用比的氟橡胶（FKM）和丙烯酸酯橡胶（ACM）并用胶的硫变特性、物理机械性能、耐老化性、热稳定性和压缩永久变形性能。实验结果表明：ACM与FKM可以很好地混合并且各自交联,从而制备综合性能优异的并用胶;并用比为30/70的ACM/FKM并用胶综合性能较佳,二段硫化后其物理机械性能和压缩永久变形性能明显改善,且耐热空气老化性能优异;热重分析结果表明,并用胶有很好的热稳定性。     

Preparation and characterization of 3-chloropropyl polysiloxane-based heat-curable silicone rubber using polyamidoamine dendrimers as cross-linkers

A series of high-temperature vulcanization (HTV) silicone rubber was prepared with polyamidoamine (PAMAM) dendrimers as concentrative cross-linkers and polysiloxane containing 3-chloropropyl groups (CPPS) as gums in a novel curing system. The curing, mechanical, and thermal properties of this novel HTV silicone rubber (MCSR) were studied through rheometry, mechanical testing, thermogravimetric analysis (TGA), and differential scanning calorimetry (DSC). The curing process was analyzed on the basis of the cure curves obtained by rheometry. The optimal conditions to prepare MCSR were determined by changing curing conditions, including cross-linker concentration, curing temperature, and postcuring temperature. MCSR exhibited a tensile strength of 9.34 MPa and a tear strength of 47.71 kN/m when the molar ratio of [3-chloropropyl]/[N–H] was 1:1.5. These excellent mechanical properties were attributed to the concentrative cross-linking effect from PAMAM dendrimers. Meanwhile, the mechanical properties slightly changed as the generation of PAMAM dendrimers increased because of steric hindrance. In addition, TGA results indicated that MCSR was thermally stable in a nitrogen atmosphere even at high degradation temperatures, such as T_{5 wt.% loss} (MCSR-3) = 451.7 °C and T_{50 wt.% loss} (MCSR-3) = 659.0 °C. DSC analysis revealed that a glass transition peak followed by a melt was identified for MCSR at − 160 °C to 30 °C. The experimental results showed that using PAMAM dendrimers as cross-linkers is a practical way to obtain silicone rubber with excellent properties.     

不同硫化体系对氟橡胶/氯醚橡胶共混物性能的影响

在固定氟橡胶(FKM)硫化体系(双酚AF)的条件下,研究了改变氯醚橡胶(CO)硫化体系对FKM/CO共混物硫化特性以及硫化胶的物理机械性能、耐老化性能、耐油性能及热稳定性的影响。结果表明,采用促进剂NA-22/MgO体系时,FKM/CO共混物具有较好的硫化特性,硫化胶的综合物理机械性能较好,但耐老化性能仍需改善;采用促进剂TCY/MgO/CaCO3体系时需要较长的硫化时间,且焦烧性能较差;并用促进剂TMTD或促进剂DTDM后混炼胶的交联效果变差;FKM/CO共混物具有较好的热稳定性且热失重起始温度高于300℃。     

丙烯酸酯橡胶的研究与应用

采用丙烯酸酯类单体通过乳液聚合制备了丙烯酸酯橡胶（ＡＣＭ）。试验研究了ＡＣＭ硫化胶的性能。结果表明,ＡＣＭ引入—ＣＯＯＨ基团,用环氧树脂作硫化剂,可以实现高温快速硫化,且其硫化胶性能良好;增大带有柔性基团的单体（增塑剂）的比例,可以改善ＡＣＭ硫化胶的耐低温性;增大极性大的单体（丙烯腈）的比例,可以改善ＡＣＭ硫化胶的耐油性和耐热性。ＡＣＭ与氟橡胶（ＦＫＭ）并用初步研究结果显示,ＦＫＭ的用量在５０份以上时,并用硫化胶性能接近ＦＫＭ     

Thermal conductivity of PVDF/PANI-nanofiber composite membrane aligned in an electric field

Poly(vinylidene fluoride)(PVDF) is a semi-crystalline thermoplastic polymer with excellent thermal stability,electrochemical stability and corrosion resistance, which has been widely studied and applied in industrial nonmetallic heat exchanger and piezoelectric-film sensor. In this study, polyaniline(PANI) nanofibers were synthesized using dodecylbenzene sulfonic acid as the surfactant. The obtained PANI nanofibers were blended in PVDF matrix to enhance thermal conductivity and tensile strength of composite materials. Electric field was applied for the orientation of membrane structure during membrane formation. Scanning electron microscope(SEM) images exhibited that the PANI nanofibers were well-dispersed in the composite membranes. The structure of composite membranes was more orderly after alignment. X-ray diffraction(XRD) and differential scanning calorimetry(DSC) indicated that the content of PANI nanofibers contributed to the transformation of PVDF from α-phase to β-phase. Both the tensile strength and thermal conductivity of composite membranes were significantly improved. This tendency was further enhanced by the application of electric field. The maximum tensile strength was obtained when the content of PANI nanofibers was 3 wt%, which was 46.44% higher than that of pure PVDF membrane. The maximum thermal conductivity of composite membranes after alignment was 84.5% greater than that of pure PVDF membrane when the content of PANI nanofibers was 50 wt%. The composite membrane is a promising new potential material in heat transfer field and the mechanism explored in this study would be informative for further development of similar thermal conductive polymeric materials.     

Mechanochemical devulcanization and gamma irradiation of devulcanized waste rubber/high density polyethylene thermoplastic elastomer

Waste rubber (WR) powder was introduced in a two-roll mill in the presence of various ratios of curatives to develop sheets of devulcanized waste rubber (DWR). The product has been investigated by FTIR, TGA and SEM. A thermoplastic elastomer (TPE) was prepared by blending the obtained DWR with high density polyethylene (HDPE) at different feed ratios under conditions of gamma irradiation, 25, 50, 100, and 150 kGy. The mechanical parameters of the blend: tensile strength, elongation at break, and hardness (Shore D) were studied. In addition, blend characterization using FTIR spectra, gel fraction, TGA and SEM was discussed.     

The effects of technological compatibility for silicone rubber/fluororubber blends

In this study, silicone rubber (SR) and fluororubber (FKM) blends were prepared and their properties were investigated. The crosslinking rate in the blends was increased with increase of SR content due to the silica filler existing into SR. As the content of FKM in the blends increases, the thermal decomposition temperature of the blends tended to increase and the thermal stability of 25/75 SR/FKM blend was higher than that of any other blends ratios. With the increase of FKM content in the blends, the contact angle of SR/FKM blends decreased and the surface energy increased owing to the change of the polarity of the surface. Dynamic mechanical analysis of 25/75 SR/FKM blend showed two transitions peak at −60.5 and −12.7°C, respectively, indicating the immiscibility. Fourier transform infrared attenuated total reflectance studies showed shifts in the peaks due to specific interactions in the blends, and field emission scanning electron microscopy (FE-SEM) studies revealed that the domain sizes of the blends come to be smaller with increasing FKM content. In the blend with 75 wt % of FKM, we observed that it is technologically compatible due to the increase of physical properties and the decrease of the domain size of FE-SEM in 25/75 SR/FKM blend. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Electron beam irradiation of polycarbonate reinforced acrylonitrile butadiene rubber

The effects of electron beam irradiation and polycarbonate (PC) concentration on the properties of acrylonitrile butadiene rubber (NBR) were investigated. The electron beam irradiation doses were from 25 to 150 kGy, whereas the PC contents were from 10 to 30 phr. It was found that the mechanical properties of NBR such as tensile strength (TS), hardness and tear strength (Ts) were remarkably improved by the incorporation of PC, while elongation at break (E_b) and thermal properties were decreased. However, the improvement in TS of NBR/PC blends was strongly dependant on PC content, in which maximum improvements need higher doses. On the other hand, the maximum value of Ts for all the blend ratios was at 25 kGy, whereas the hardness increases with increasing irradiation dose. Moreover, it was observed that the fuel resistance of NBR/PC was higher than NBR and decreases by increasing the content of PC.     

氟橡胶/三元乙丙橡胶并用胶的性能

研究了不同并用比(质量比)时氟橡胶(FKM)/三元乙丙橡胶(EPDM)并用胶动态硫化和静态硫化后的低温性能、物理机械性能、耐老化性能和热稳定性,并用扫描电子显微镜表征了并用胶.结果表明,当并用比为30/70时,并用胶有较好的相容性;EPDM可以改善FKM的低温性能;随着EPDM用量的增加,并用胶的拉伸强度及邵尔A硬度降低;动态硫化FKM/EPDM并用胶比静态硫化FKM/EPDM并用胶具有更好的耐老化性能,但老化前前者的拉伸强度稍低于后者;FKM/EPDM并用胶的热稳定性优于纯EPDM;静态硫化FKM/EPDM并用胶中片层现象严重,动态硫化FKM/EPDM并用胶的EPDM包覆在FKM中,但相畴偏大.     

Thermal and thermomechanical characteristics of monolithic refractory composite matrix containing surface-modified graphite

The thermomechanical analysis (TMA) and thermal characteristics of carbon-containing refractory castable matrix with 20.0 wt% graphite have been compared with graphite-free high alumina based similar castable matrix. Graphite has been added both in uncoated and coated forms, the latter having a thin sol–gel calcium aluminate coating on as-received graphite flakes. The influence of systematic variation of microfine constituents e.g. reactive alumina, high alumina cement etc in the matrix has been investigated in terms of the heat flow studies obtained by differential scanning calorimetry (DSC) and thermogravimetry analysis (TGA). The densification behavior of graphite-free and graphite-containing castable matrices has been critically estimated by the dimensional changes in dynamic heating regime up to 1500 °C. The role of coated graphite on improved densification behavior of refractory was explored by microstructure and phase assemblage studies of the respective fired castable. It was further corroborated by the transmission electron microscope (TEM) studies of surface-modified graphites.     

氢化丁腈橡胶与聚氯乙烯或聚乙烯共混

研究氢化丁腈橡胶（HNBR）与聚氯乙烯（PVC）或聚乙烯（PE）的共混，该HNBR是用偶氨法常压氢化丁腈胶乳制得的。共混物的力学性能表明，在HNBR质量分数为40％以上时，2种共混物均呈现热性橡胶性能。HNBR／PVC共混物在拉伸强度方面呈现加和关系。热老化后HNBR／PE共混物的力学性能比NBR／PE共混物的好得多。用扫描电镜观察HNBR／PE 混物的断面形态。并用DSC曲线研究了HNBR／PE共混物的结晶变化。     

Electron beam processing of nylon 6 and hydrogenated nitrile rubber (HNBR) blends: 1. Development of high strength heat‐ and oil‐resistant thermoplastic elastomers

The effects of electron beam irradiation on the morphology, mechanical properties and heat and hot oil resistance of a thermoplastic elastomeric blend of 50/50 nylon 6 and HNBR rubber were investigated. The morphology of the blend was studied by scanning electron microscopy, with special reference to the effects of processing via injection moulding and the radiation dose. Irradiation of extruded pellets at low doses and subsequent injection moulding improved the blend morphology, thereby enhancing the mechanical properties. The tensile strength of the blend increased with radiation dose. The irradiated blends had excellent hot oil resistance and the tensile strength of the blends did not change much after ageing at 150 °C for 72 h. Incorporation of 10 phr SRF black to the blend greatly improved the tension set property. Copyright © 2005 Society of Chemical Industry     

Flame retardancy and thermal stability of ethylene-vinyl acetate copolymer nanocomposites with alumina trihydrate and montmorillonite

The development of fire retardant for wire and cable sheathing materials has oriented toward low smoke and halogen-free flame retardant technology to achieve better safety for electrical equipment and devices and to satisfy standards. However, many polymer flame resistance materials require a very high proportion of metal hydrate filler within the polymer matrix (60 wt%) to achieve a suitable level of flame resistance, which may lead to inflexibility, poor mechanical properties and problems during compounding and processing. In this study, the alumina trihydrate (ATH) was added to montmorillonite (MMT) as the halogen-free flame retardant of ethylene-vinyl acetate (EVA) copolymer, with various ratios of EVA/ATH/MMT. The prepared nanocomposites were characterized through various techniques of XRD, tensile test, DSC analysis, TGA, LOI evaluation, and FE-SEM to explore the effects of organic modified clay (OMMT) and the layer distance on the mechanical, thermal, and flame resistance properties. In the XRD examinations, the layer-distance of MMT increased from 1.27 to 1.96 nm when polymer was added to the octadecylamine modified MMT. The best tensile strength was obtained at 3 wt% MMT. In addition, the halogen-free flame resistance grade of EVA containing 3 wt% OMMT and 47 wt% ATH revealed the best elongation and fire resistance (LOI = 28). The tensile and flame resistance properties of the nanocomposites were also significantly improved.     

Self-assembled natural rubber/multi-walled carbon nanotube composites using latex compounding techniques

Functionalization of multi-walled carbon nanotubes (MWCNTs) plays an important role in eliminating nanotube aggregation for reinforcing polymeric materials. We prepared a new class of natural rubber (NR)/MWCNT composites by using latex compounding and self-assembly technique. The MWCNTs were functionalized with mixed acids (H2SO₄/HNO₃ = 3:1, volume ratio) and then assembled with poly (diallyldimethylammonium chloride) and latex particles. The Fourier transform infrared spectroscopy, transmission electron microscopy, and scanning electron microscopy were used to investigate the assembling mechanism between latex particles and MWCNTs. It is found that MWCNTs are homogenously dispersed in the natural rubber (NR) latex as individual nanotubes since strong self-aggregation of MWCNTs has been greatly depressed with their surface functionalization. The well-dispersed MWCNTs produce a remarkable increase in the tensile strength of NR even when the amount of MWCNTs is only 1 wt.%. Dynamic mechanical analysis shows that the glass transition temperature of composites is higher and the inner-thermogenesis and thermal stability of NR/MWCNT composites are better, when compared to those of the pure NR. The marked improvement in these properties is largely due to the strong interfacial adhesion between the NR phase and MWCNTs. Functionalization of MWCNTs represents a potentially powerful technology for significant reinforcement of natural rubber materials.     

Acrylic rubber‐fluorocarbon rubber miscible blends: Effect of curatives and fillers on cure,mechanical, aging,and swelling properties

The cure characteristics and mechanical properties of gum and filled acrylic rubber (ACM), fluorocarbon rubber (FKM), and their blends of varying compositions were studied both under unaged and aged conditions. The rheometric study showed that optimum cure properties were obtained using a mixed curing system of blocked diamine, hexamethylenediamine carbamate (Diak #1), and ammonium benzoate. From varying the curing agents, the optimum levels of Diak #1 and ammonium benzoate were found to be 1.5 and 2.5 phr, respectively. The addition of different fillers and their loading influenced the cure properties, with increased torque and reduced scorch safety. The gum and filled 50:50 (w/w) ACM‐FKM showed overall performance in strength properties. Postcuring improved the strength of all the systems, especially the systems with a higher proportion of FKM. None of the properties changed significantly during aging of the blends. FKM and the blends containing a higher proportion of FKM were affected least by aging. Swelling of the blends was reduced by the addition of fillers. Dynamic mechanical thermal analysis showed a single tan δ peak corresponding to a single phase transition for both cured and filled blends. The storage modulus of the blend increased from the gum blend to the filled blend, indicating the presence of polymer‐filler interaction. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 1442–1452, 2003     

Preparation and properties of heat curable blended methylfluorosilicone rubber

Heat curable blended methylfluorosilicone rubber (MFSR) was prepared by combination of methylsilicone rubber (MSR) and fluorosilicone rubber (FSR). 2,5‐Bis(tert‐butylperoxy)‐2,5‐dimethylhexane (DBPMH) was chosen as a curing agent. Poly(methylsiloxane‐co‐fluorosiloxane) with low molecular weight was used as an interfacial agent. Curing characteristics, mechanical properties, low temperature performance, and hot oil resistance of blended MFSR was studied in details. The results showed that MSR and FSR could reach co‐vulcanization by DBPMH in blended MFSR. Higher FSR content could improve the scorch safety, lower the rate of curing reaction, and lead to the poor processability of blended MFSR. An increase of FSR content also improved the hot oil resistance of blended MFSR. Interfacial agent could limit the phase separation of MSR and FSR, make the blended system more thermodynamically stable and elevate the mechanical properties of blended MFSR. Differential scanning calorimetry (DSC) measurements revealed that increasing MSR content lowered the glass transition temperature (T_g) and improved the low‐temperature flexibility of blended MFSR when MSR was no more than 15%. POLYM. ENG. SCI., 2013. © 2012 Society of Plastics Engineers     

Study of the miscibility and mechanical properties of NBR/HNBR blends

In this study, hydrogenated acrylonitrile butadiene rubber (HNBR, ZETPOL‐2010L) and nitrile butadiene rubber (NBR, NIPOL‐DN4555) were blended at different ratios in a Haake melt blender at 130°C. The HNBR and the NBR were of very similar acrylonitrile content and Mooney viscosity. The melt miscibility and solid‐state properties were investigated by rheological, thermal, and mechanical testing and scanning electron microscopy (SEM) techniques. The dynamic viscosity of the blends followed the log‐additivity rule, while the flow activation energy closely followed the inverse additivity rule. On the other hand, the storage modulus showed synergistic effects at all compositions, suggesting the presence of emulsion morphology at both ends of the composition range. For the 50/50 HNBR/NBR blend, the SEM micrographs suggest a uniform elongated structure. The thermal analysis showed the presence of two glass transitions, representing the pure components, at all blend ratios, suggesting the absence of segmental miscibility of the blends. The small‐strain mechanical properties such as tensile modulus and yield stress followed linear additivity. However, HNBR and HNBR‐rich blends were observed to strain harden at a rate higher than that of NBR. Induced crystallization of HNBR was suggested to be the reason for the strain hardening. The different rheological, thermal, and mechanical testing techniques agree in suggesting that the structurally similar HNBR and NBR are not thermodynamically miscible but mechanically compatible. Polym. Eng. Sci. 44:2346–2352, 2004. © 2004 Society of Plastics Engineers.