As diene rubber products are generally fabricated with complicated curing package involving toxic additives, the exploration of alternative green curing chemistry for diene rubber is of great importance. In this contribution, we demonstrate a curing chemistry based on oxa-Michael reaction for diene rubber to achieve the combination of simple curing system and tunable mechanical properties. Specifically, pendent hydroxyls are introduced onto the solution-polymerized styrene-butadiene rubber (SSBR) via thiol-ene click reaction and the modified SSBR is effectively cured by various acrylates without the use of any additional additives. The mechanical behaviors of vulcanizates can be widely regulated by manipulating the network structures, which is tuned by curing temperature, hydroxyl content of SSBR, content and functionality of acrylates. The correlation between mechanical properties and network structure is accordingly achieved, which provides essential basis for the future application of the diene rubbers cured by oxa-Michael reaction.
Hybrids consisting of graphene oxide (GO) sheets and butadiene-styrene-vinyl pyridine rubber (VPR) were prepared by a co-coagulation process with different flocculants, hydrogen chloride and calcium chloride, in order to form two kinds of bonding interfaces, namely ionic bonding (HVPR) and hydrogen bonding (CaVPR) interfaces. To reveal the effects of interfacial interaction on the chain dynamics, the dielectric relaxation spectra of these hybrids have been investigated. The results show that all hybrids exhibit two distinct relaxation processes, segmental relaxation and interfacial relaxation. The concentration of GO has no impact on the segmental dynamics of CaVPR, but the segmental dynamics of HVPR slow down at 1.5 vol% of GO. Meanwhile, the segmental relaxation of HVPR is always a little faster than its CaVPR counterpart. In the temperature range of 5–35 °C, a new relaxation mode, which is slower than the segmental relaxation and attributed to the interphase with restricted chain dynamics, has been observed for all the hybrids with a GO loading lower than 2.5 vol%. The interfacial relaxation time of HVPR decreases with decreasing GO concentration. However, in CaVPR it first decreases and then increases with decreasing GO concentration. Most interestingly, the interfacial relaxation of HVPR is slower than that for CaVPR. The dielectric strength (Δε), the calculated fragility parameter and the effective activation enthalpy of the interfacial chains in HVPR are always higher than those in CaVPR with the same GO concentration. All the evidence indicates the stronger interfacial interactions in HVPR than in CaVPR.
It has been commonly acknowledged that particle dispersion and interfacial interactions are vital in determining the ultimate performance of polymer composites. However, the interplay between dispersibility and interfacial interaction in polymer composites has not been explicitly unraveled. In this contribution, a series of silica with controlled surface chemistry are prepared to reveal the effects of subtle change in surface property of filler on the structures and mechanical performance of the rubber composites. On the basis of thermodynamic theory, the dispersibility of modified silica in rubber is quantitatively evaluated by using surface energy. The modified silica was introduced into styrene-butadiene rubber (SBR) to investigate the effects of surface modification on the dispersion of silica and interfacial interaction of the rubber composites. It has been demonstrated that subtle change in surface chemistry of silica drastically improves its dispersibility in rubber matrix, leading to much improved accessible surfaces and hence much complete interfacial reaction. At very low grafting content (0.2 molecule/nm2), improved modulus (44%) and wet-traction (54%), together with reduced rolling-resistance (11%), are concurrently observed.
The reinforcement effects of halloysite nanotubes (HNTs) on styrene-butadiene rubber (SBR) and the modification effect of epoxidized natural rubber (ENR) on SBR/HNTs composites were studied. The structure, morphology and properties of SBR/HNTs composites before and after the incorporation of ENR were investigated. The results indicated that ENR can promote the dispersion and orientation of HNTs in SBR matrix at nanoscale and strengthen interfacial combination between HNTs and SBR by the formation of covalent bonds and hydrogen bonds between ENR and HNTs. Consequently ENR can improve the mechanical properties of the vulcanizates of SBR/HNTs composites. Besides ENR can decrease the rolling resistance of the vulcanizates and increase the wet grip property of the vulcanizates.
High performance light-colored rubber-inorganics nanocomposites were fabricated by the direct incorporation of sorbic acid (SA) in the filled rubber compounds. The mechanisms of largely improved performance were studied in details. The strong interfacial bonding between rubber matrix and the filler and significantly improved dispersion of the filler were resulted through SA intermediated linkages. Effect of SA on the vulcanization behavior, morphology and mechanical properties were studied. Formation of zinc disorbate (ZDS) and its reinforcing effect on rubber was investigated. High content of ZDS leaded to high ionic crosslink density and had a more significantly effect on enhancing the performance of rubber. The composites with high nanotubular clay content were found to be highly ionic crosslinked, optical transparent and exhibited high mechanical strength and heat resistance. The properties of the composites were ascribed to the strong interfacial interactions and the excellent dispersion of nanotubular clay.
Summary: Attempts were made to prepare thermoplastic elastomers (TPE) from scrap rubber powder (SRP) and linear low‐density polyethylene (LLDPE) as thermoplastic polymer matrix. The solid‐phase grafted copolymer of LLDPE (LLDPE‐g‐VM) and epoxidized natural rubber (ENR) were used as dual compatibilizers to improve the interfacial adhesion between SRP and LLDPE. The compatibilized SRP/LLDPE blends had obviously improved the interfacial properties between SRP particles and LLDPE. Using this method, thermoplastic elastomer was prepared successfully. The mechanical properties especially elongation at break was improved significantly. SEM and TEM studies showed that the ENR/LLDPE‐g‐VM dual compatibilizer improved the distribution state of SRP particles in LLDPE and the adhesion between SRP and LLDPE. DSC results showed a distinct glass transition at 74 °C of the interfacial region. The improvement in mechanical properties was attributed to the enhanced interfacial properties of the blend. Surface of SRP particles of the composites compatibilized by the dual compatibilizer. image Surface of SRP particles of the composites compatibilized by the dual compatibilizer.
State-of-the-art processes cannot achieve rubber/multi-walled carbon nanotube (MWCNT) composites with satisfactory performance by using pristine MWCNTs and conventional processing equipment. In this work, high performance rubber/MWCNT composites featuring a combination of good mechanical properties, electrical and thermal conductivities and damping capacity over a wide temperature range are fabricated based on a well-developed master batch process. It is demonstrated that the MWCNTs are dispersed homogeneously due to the disentanglement induced by well-wetting and shearing, and the elastic-resilience-induced dispersion of the MWCNTs by rubber chains via the novel processing method. To further enhance the efficacy of elastic-resilience-induced dispersion for MWCNTs, a slightly pre-crosslinked network is constructed in the master batch. Consequently, we obtain rubber/MWCNT composites with unprecedented performance by amplifying the reinforcing effect of relatively low MWCNT loading. This work provides a novel insight into the fabrication of high performance functional elastomeric composites with pristine CNTs by taking advantage of the unique elastic resilience of rubber chains as the driving force for the disentanglement of CNTs.
Clay-philic benzothiazole sulfide, capable of donating electrons, is grafted onto polypropylene (PP) backbones when N-cyclohexyl-2-benzothiazole sulfonamide (CBS), a commonly used accelerator in the tire industry, is included in the processing of PP/halloysite nanotubes (HNTs) composites. CBS decomposes at elevated temperature and yields benzothiazole sulfide radicals, which react with the PP polymeric free radicals generated during the processing of the composites. On the other hand, the benzothiazole group of CBS is reactive to HNTs via electron transferring. The compatibilization between HNTs and PP is thus realized via interfacial grafting and electron transferring mechanism. The interfacial interactions in the compatibilized systems were fully characterized. Compared with the control sample, the dispersion of HNTs and the interfacial bonding are enhanced substantially in the compatibilized composites. The significantly improved mechanical properties and thermal properties of benzothiazole sulfide compatibilized PP/HNTs composites are correlated to the enhanced interfacial property. The present work demonstrates a novel interfacial design via interfacial grafting/electron transferring for the compatibilization of PP/clay composites.
No abstract is provided for this article.
No abstract is provided for this article.
Halloysite nanotubes (HNTs) were utilized to prepare polypropylene (PP) nanocomposites by simple melt-compounding approach. Compared with other silicates such as montmorillonite and kaolinite, HNTs show much better dispersion property. The PP nanocomposites with HNTs exhibit concurrence increase in tensile and flexural strength, flexural modulus and impact toughness. Surface modification of HNTs lends the PP nanocomposites higher strength, modulus and lower toughness. The increase in mechanical properties is correlated with the well dispersion of the high aspect ratio HNTs and the orientation of HNTs in PP matrix. Morphology studies show that HNTs can be dispersed in PP uniformly at lower HNTs loading and excessive loading of HNTs causes a little aggregation. Surface modification of HNTs can alleviate the aggregation effectively. The storage modulus of the nanocomposites increases consistently with the HNTs concentration. The surface modification is beneficial to the further improvement in storage modulus. Similar to other silicates, HNTs facilitate the crystallization of PP due to the heterogeneous nucleation
