硬质橡胶载体硫磺的制备及其在橡胶中的应用

通过在橡胶中添加大量硫磺,采用低温硫化得到高玻璃化温度的硬质橡胶,粉碎清洗烘干得到载体硫磺,并研究载体硫磺硫化胶的各项性能。结果表明：载体硫磺在其玻璃化温度以下不参与硫化,能有效的避免早期焦烧,高温下正常参与硫化,其硫化胶的各项性能和普通硫磺硫化胶相近。载体硫磺能抑制混炼胶喷霜,且生产成本低,可考虑代替不溶性硫磺。     

Preparation of high-performance deproteinized natural rubber/chitosan composite films via a green and sulfur-free method

To solve the environment and health issues arose from the sulfur vulcanization, a facile and completely eco-friendly method of latex-assembly and in situ cross-linking is developed to prepare fully bio-based and high-performance rubber films. The films are featured by a “reinforced concrete” structure composed of dynamically cross-linked chitosan framework and unvulcanized deproteinized natural rubber (DPNR) matrix. The self-assembly of DPNR latex particles and chitosan, as well as the in situ cross-linking of chitosan in the film forming process are confirmed by transmission electron microscope and dynamic light scattering. As green rubbers without vulcanization, the as-designed composite films possess excellent mechanic properties comparable to those of the sulfur vulcanized DPNR film, whose tensile strength and toughness reach 15.2 MPa and 77.6 MJ m⁻³ respectively. Moreover, the films exhibited appropriate permeability to moisture and achievable reprocessing, which have potential applications in wearable devices.     

The effect of dynamic vulcanization on mechanical properties and water absorption of silica and rubberwood filled polypropylene/natural rubber hybrid composites

Dynamic vulcanized silica and rubberwood filled polypropylene (PP)/natural rubber (NR) hybrid composites were prepared using a Brabender plasticorder at 150°C and a rotor speed of 50 rpm for 12 minutes. The effectiveness of the dynamic vulcanization was indicated by the Brabender plastograms. The mechanical and water absorption properties of hybrid composites with different concentration of sulfur were investigated. Significant enhancement in mechanical properties, viz. tensile strength, stress at peak, Young modulus and flexural modulus were observed for dynamically vulcanized hybrid composites compared to unvulcanized hybrid composites. This has been attributed to the increase in crosslink density, which was manifested by a reduction of water absorption and increase of stabilization torque at the end of mixing stage with increasing sulfur concentration.     

Novel dynamic vulcanization of polyethylene and ozonolysed natural rubber blends: Effect of curing system and blending ratio

Dynamic vulcanization was studied in terms of the change in α‐relaxation temperatures of the LDPE matrix, morphology, and mechanical properties of LDPE/ozonolysed NR blends which were vulcanized at various blend ratios and with different curing systems, i.e., peroxide and sulfur systems. The ozonolysed NR with M _w = 8.30 × 10⁵ g mol⁻¹ and M _n = 2.62 × 10⁵ g mol⁻¹, prepared by the in situ ozonolysis reaction of natural rubber latex, was used in this study. The significant change in the α‐relaxation temperature of LDPE in the LDPE/ozonolysed NR, dynamically vulcanized using the sulfur system, suggested that sulfur vulcanization of the blend gave a higher degree of crosslink density than using peroxide and corresponded with the improved damping property and homogenous phase morphology. However, the peroxide cured blends of LDPE/ozonolyzed NR gave more improvement of tensile strength and elongation at break than the sulfur cured system. Furthermore, the mechanical properties of tensile strength, elongation at break, and damping were improved by increasing the ozonolyzed natural rubber content in both DCP and sulfur cured blends. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

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     

不同硫化体系对环保型硬丁腈橡胶性能的影响

以松香酸皂与油酸皂组成的复合乳化体系制备的中试产品丁腈橡胶(NBR)为基胶,分别用硫黄体系和过氧化物体系进行硫化,研究了NBR混炼胶的硫化特性和硫化胶的物理机械性能、耐老化性能、耐油及耐寒性能,并与传统产品NBR 3604进行了比较。结果表明,采用硫黄体系时,NBR混炼胶的硫化程度较浅,硫化速率较慢;采用过氧化物体系时,NBR混炼胶的硫化程度较深,硫化速率较快,NBR胶料宜采用过氧化物硫化体系进行硫化;2种硫化体系下制得NBR硫化胶的物理机械性能与NBR3604硫化胶相差不大,过氧化物硫化体系制得NBR硫化胶的耐老化性能较好;与NBR 3604硫化胶相比,2种硫化体系下制得NBR硫化胶的耐寒性稍好,耐油性稍差。     

Based on transalkylation reaction the rearrangeable conventional sulfur network facile design for vulcanized diolefin elastomers

Achieving the reversibility of conventional sulfur crosslinking network is beneficial for the sustainability of rubber products. However, sulfur crosslinking network has been considered as an irreversible network. Here, natural rubber (NR) is chosen as an example and trimethylsulfonium iodide (TMSI) can enable the transalkylation reaction between aliphatic sulfonium salts and the alkyl chains of vulcanized NR, which further realizes the rearrangements of sulfur crosslinking network in the elastomers. Such rearrangement reaction enhances the interfacial adhesion and fuse the fractured surface of vulcanized NR. Moreover, the rearrangements of sulfur crosslinking network induced by TMSI conforms to the characteristics of vitrimer network. This work solves the rearrangement problem of conventional sulfur crosslinking network, which is beneficial for the sustainability of rubber products.     

Effect of Grafted Carbon Black on Properties of Vulcanized Natural Rubber

Summary To modify carbon black (CB) surface, in situ grafting of natural rubber (NR) onto the CB surface by solid-state method was used to get grafted carbon black (GCB). The vulcanization characters of NR compounds employed CB and GCB were investigated. Crosslinking density of vulcanized NR was measured by equilibrium swelling method. As a result, it was found that GCB could improve both cure rate and crosslinking density. Moreover, the mechanical properties of vulcanized NR filled with GCB were enhanced to a large extent compared with vulcanized NR filled with CB. No Payne Effect was observed in GCB filled NR compounds during dynamic properties testing, indicating that there was no filler network and GCB was dispersed uniformly in NR matrix, which was proved by SEM micrographs. Based on above results, it was considered that the grafting modification weakened filler-filler interaction and enhanced filler-polymer interaction.     

天然橡胶与甲基硅油的相容性研究

研究了不同硫化体系和不同硫化剂用量的天然橡胶与甲基硅油的相容性。结果表明,硫黄硫化胶与甲基硅油具有较好相容性,其中半有效硫化体系硫化胶在85℃硅油中浸泡168h后力学性能最好,拉伸强度仍高达17.8MPa,质量变化率只有1.41%,基本不溶胀。     

改性氯化聚乙烯橡胶（MCM）含硫化合物硫化的研究

所研究的含硫硫化体系S-LS-1能有效地硫化改，巨氯化聚乙烯橡胶（MCM）C-20H。硫化胶具有优良的机械性能和耐含醇燃油性能两者都优于丁腈橡胶。此体系适合于用模压和挤出工艺加工改性氯化聚乙烯橡胶。     

Carbon nanotubes as Raman sensors of vulcanization in natural rubber

A method has been developed to synthesize composites with cross-linked natural rubber (NR) and dispersed single-wall carbon nanotubes (SWNT). The mechanical response of the NR samples was observed to change as a function of the amount of sulfur used for cross-linking, based on the number density of cross-links resulting from the vulcanization process. The relationship between SWNTs D^∗ wavenumber shift and the amount of sulfur have been obtained by means of Raman spectroscopy. The cross-link densities of the NR and SWNT/NR samples have been calculated from uniaxial stress-strain measurements, and plotted as the function of the amount of added sulfur. Comparison of the results from mechanical measurements and Raman spectroscopic measurements showed that SWNT Raman sensors are sensitive to the cross-link density in natural rubber and can be used to evaluate the cross-linking process of rubbery materials.     

Hydrogenated natural rubber blends: Aspect on thermal stability and oxidative behavior

Hydrogenated natural rubber (HNR) prepared from natural rubber (NR) is a new sustainable elastomer with excellent thermal properties. This study reports on the effect of vulcanization system and blend ratio on the thermal and oxidative resistance of HNR/NR vulcanizates. The various HNR/NR ratios vulcanized by peroxide and sulfur donor system exhibited the highest retention of tensile strength after thermal aging due to the formation of zinc‐dimethyldithiocarbamate (ZDMDC) which is an efficient antioxidant. The results from thermogravimetric analysis (TGA) indicated that the saturated structure of HNR had higher decomposition temperature and activation energy to enhance the thermal stability of HNR/NR vulcanizates. The initial and maximum decomposition temperatures of NR and HNR phases in vulcanizates were not affected by rubber blend ratio. This suggests that the decomposition pattern of HNR has no influence on another constituent. The increase in HNR content in the blends could retard the ozonolysis resulting in the surface cracking attacked by ozone. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Cure behavior and antimicrobial performance of sulfur‐cured natural rubber vulcanizates containing 2‐hydroxypropyl‐3‐piperazinylquinolinecarboxylic acid methacrylate or silver‐substituted zeolite

This work used 2‐hydroxypropyl‐3‐piperazinylquinolinecarboxylic acid methacrylate (HPQM) or silver‐substituted zeolite (SSZ) as antibacterial agents for natural rubber (NR) compounds vulcanized by conventional vulcanization (CV), semi‐efficient vulcanization, and efficient vulcanization (EV) systems. The cure behavior and antibacterial performance of the NR vulcanizates were studied by varying the loadings of HPQM or SSZ, contact times, and vulcanization systems. The antibacterial performance of the rubber compounds was examined by halo test and plate‐count‐agar methods against Escherichia coli (E. coli, ATCC 25922) and Staphylococcus aureus (S. aureus, ATCC 25923) as the testing bacteria. The cure time and crosslink density were dependent on the vulcanization recipe used but were not affected by the addition of HPQM or SSZ. Diphenylguanidine at the level of 1.0 phr (parts by weight per hundred parts of resin) in NR vulcanized by the EV system had the ability to kill the E. coli and S. aureus bacteria. The NR vulcanized by the CV system showed the most pronounced antibacterial performance, as compared with the other two vulcanization systems, via migration and diffusion of HPQM or SSZ onto the NR surfaces, this being identified by the relatively large reduction of contact angle values. The HPQM showed the most preference for NR compounds vulcanized with the CV system with a contact time of 120 min or longer to achieve a bacteria‐killing efficacy of 99.0–99.9%, the efficacy being more pronounced for E. coli bacteria. J. VINYL ADDIT. TECHNOL., 19:123–131, 2013. © 2013 Society of Plastics Engineers     

Influence of reversion in compounds containing recycled natural rubber: In search of sustainable processing

The influence of rubber devulcanization by microwaves in the reversion behavior is still modestly explored in the literature. The reversion occurs due to thermal degradation of unstable crosslinkings formed during the vulcanization process. This phenomenon results in poor final mechanical properties of the artifacts. In this work, some formulations based on natural rubber (NR) with the incorporation of NR devulcanized by microwaves at different exposure times to the microwaves were vulcanized by compression molding at the same temperature and time used for the study of their vulcanization characteristics, in order to correlate the properties obtained and understand the influence of the reversion on the mechanical properties. The results showed that levels of devulcanization/degradation of the recycled phase, as well as the additional heating time influenced on the behavior of reversion and, consequently, on the mechanical properties. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45325.     

Influence of Type of Vulcanization on Rheological and Thermal Properties of PP/NR Blends

Summary Rheological and thermal behavior of isotactic polypropylene (PP) and natural rubber (NR) blends were studied, with special reference to the type of vulcanization (dynamic and static). It was found that dynamic crosslinking of the NR phase increases the viscosity of the system, while it decreases crystallinity degree. Statically vulcanized blends show similar properties regardless curing time while dynamically vulcanized blends show enhanced properties if compared to the corresponding uncured blends.     

Improving blood compatibility of natural rubber by UV‐induced graft polymerization of hydrophilic monomers

Natural rubber (NR) latex films surface‐grafted with hydrophilic monomers, poly(ethylene glycol) methacrylate (PEGMA), N‐vinylpyrrolidone (VPy), and 2‐methacryloyloxyethyl phosphorylcholine (MPC), were prepared by UV‐induced graft polymerization using benzophenone as a photosensitizer. The grafting yield increases of vulcanized NR latex films as a function of time and monomer concentration were of lesser magnitude than those of the unvulcanized NR latex films. This can be explained as a result of the crosslinked network generated during vulcanization acting as a barrier to the permeation of the photosensitizer and the monomer. The appearance of a characteristic carbonyl stretching in the attenuated total reflectance‐Fourier transform infrared spectroscopy (ATR‐FTIR) spectra of NR latex films after the surface grafting of PEGMA and MPC indicates that the modification has proceeded at least to the sampling depth of ATR‐FTIR (∼ 1–2 μm). According to the water contact angle of the modified NR latex films, the surface grafting density became higher as the grafting time and monomer concentration increased. The complete absence of plasma protein adsorption and platelet adhesion on the surface‐modified NR latex films having grafting yield above 1 wt % is a strong indication of improved blood compatibility. Results from tensile tests suggest that graft polymerization does not cause adverse effects on the mechanical properties of vulcanized NR latex films. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

The Effect of Dicumyl Peroxide Vulcanization on the Properties & Morphology of Polypropylene/Ethylene-Propylene Diene Terpolymer/Natural Rubber Blends

ABSTRACT

This article discusses some properties such as tensile properties, chemical and oil resistance, gel content, crystallinity, and morphology of polypropylene (PP)/ethylene-propylene diene terpolymer (EPDM)/natural rubber (NR) blends. Dicumyl peroxide (DCP) was applied as a crosslinking agent. In terms of tensile properties, peroxide vulcanized blend shows higher tensile strength and tensile modulus (stress at 100% elongation, M₁₀₀) as compared with the unvulcanized blend. The elongation at break of the peroxide vulcanized blend is higher for the blend with NR rich content compared with the EPDM rich content. The improvements in chemical and oil resistance as well as gel content of peroxide vulcanized blends have also proved the formation of crosslinks in the rubber phase. Scanning electron microscopy (SEM) micrographs from the surface extraction of the blends support that the crosslinks have occurred during dynamic vulcanization. Dynamical vulcanization with DCP has decreased the percent crystallinity of blends that can be attributed to the formation of crosslinks in the rubber.     

The Effect of Dynamic Vulcanization on the Properties of Polypropylene/Ethylene-Propylene Diene Terpolymer/Natural Rubber (PP/EPDM/NR) Ternary Blend

The effects of dynamic vulcanization on the process development and some properties, such as tensile properties, swelling index, gel content, crystallinity, and morphology, of the polypropylene (PP)/ethylene-propylene diene terpolymer (EPDM)/natural rubber (NR) blends were investigated. Dynamically vulcanized blends show higher stabilization torque than unvulcanized blends. In terms of tensile properties, the tensile strength and tensile modulus (stress at 100% elongation, M₁₀₀) of the vulcanized blends have been found to increase as compared with the unvulcanized blends, whereas the elongation at break is higher in the blend with richer EPDM content. These results can be attributed to the formation of cross-linking in the rubber phase. The formation of cross-links in the rubber phase has also been proved by swelling index and gel content. The percentage of crystallinity of the blends is decreased by dynamic vulcanization. Scanning electron microscopy (SEM) micrographs from the surface extraction of the blends support that the cross-links occurred during dynamic vulcanization.     

Preparation of zinc‐oxide‐free natural rubber nanocomposites using nanostructured magnesium oxide as cure activator

The effect of sol–gel synthesized magnesium oxide (MgO) nanoparticles as cure activator is studied for the first time in the vulcanization of natural rubber (NR) and compared with conventional zinc oxide (ZnO) in terms of cure, mechanical, and thermal properties. The NR vulcanizate with 1 phr (Parts per hundred parts of rubber) nano MgO shows an excellent improvement in the curing characteristics and the value of cure rate index is about 400% greater for NR vulcanizate containing 1 phr nano MgO in comparison to the NR vulcanizate with 5 phr conventional ZnO. Both mechanical and thermal properties of NR vulcanizate are found to be satisfactory in the presence of 1 phr nano MgO as cure activator in comparison to conventional NR vulcanizate. This study shows that only 1 phr nano MgO can successfully replace 5 phr conventional ZnO with better resulting properties in the sulfur vulcanization of NR. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42705.     

天然橡胶超声硫化

成功地利用超声波对天然橡胶进行了硫化,所得试件展示了与传统硫化方法制得的试件相同的性能,但该工艺表现出许多传统硫化方法所不具备的优点.用滞后能量损失理论及声化学作用,解释了超声硫化的机理.用温频转换法,得到了天然橡胶混炼胶在高频条件下的动态力学性能,由此得到硫化开始阶段的温升曲线,该曲线与实验结果吻合.