4 results
Search Results
Now showing 1 - 4 of 4
- ItemTuning the Properties and Self-Healing Behavior of Ionically Modified Poly(isobutylene-co-isoprene) Rubber(Washington, DC : Soc., 2017) Suckow, Marcus; Mordvinkin, Anton; Roy, Manta; Singha, Nikhil K.; Heinrich, Gert; Voit, Brigitte; Saalwächter, Kay; Böhme, FrankThe focus of this work is on the nature of self-healing of ionically modified rubbers obtained by reaction of brominated poly(isobutylene-co-isoprene) rubber (BIIR) with various alkylimidazoles such as 1-methylimidazole, 1-butylimidazole, 1-hexylimidazole, 1-nonylimidazole, and 1-(6-chlorohexyl)-1H-imidazole. Based on stress-strain and temperature dependent DMA measurements, a structural influence of the introduced ionic imidazolium moieties on the formation of ionic clusters and, as a consequence, on the mechanical strength and self-healing behavior of the samples could be evidenced. These results are fully supported by a molecular-level assessment of the network structure (cross-link and constraint density) and the dynamics of the ionic clusters using an advanced proton low-field NMR technique. The results show distinct correlations between the macroscopic behavior and molecular chain dynamics of the modified rubbers. In particular, it is shown that the optimization of material properties with regard to mechanical and self-healing behavior is limited by opposing tendencies. Samples with reduced chain dynamics exhibit superior mechanical behavior but lack on self-healing behavior. In spite of these limitations, the overall performance of some of our samples including self-healing behavior exceeds distinctly that of other self-healing rubbers described in the literature so far.
- ItemTailor-Made Functional Polymethacrylates with Dual Characteristics of Self-Healing and Shape-Memory Based on Dynamic Covalent Chemistry(New York, NY [u.a.] : Wiley InterScience, 2020) Mondal, Prantik; Behera, Prasanta K.; Voit, Brigitte; Böhme, Frank; Singha, Nikhil K.New shape memory polymers with self-healing behavior are obtained by thermoreversible Diels–Alder (DA) cross-linking of a furfuryl group-containing star-block copolymer with 1,1'-(methylenedi-4,1-phenylene)bismaleimide. The star-block copolymer consisting of a 3-arm polycaprolactone (PCL) core and a polyfurfuryl methacrylate shell is synthesized by reversible addition–fragmentation chain transfer (RAFT) polymerization. For this, a 3-arm macro-RAFT agent based on PCL is converted with an appropriate amount of furfuryl methacrylate in the presence of a radical initiator. Films of the DA network are partly insoluble at ambient temperatures. After annealing at 120 °C the films become completely soluble because of the progressing retro-DA reaction. Evaporation of the solvent and subsequent annealing at 60 °C restores the original insoluble state of the material. By means of a scratch test and tensile tests on cut and subsequently mended samples it is shown that the retro-DA reaction facilitates self-healing. Additionally, the films show pronounced shape memory effects with reasonable shape recovery and fixity ratios, which are attributed to the melting and crystallization of the PCL phase. © 2020 The Authors. Published by WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
- ItemTemperature Scanning Stress Relaxation of an Autonomous Self-Healing Elastomer Containing Non-Covalent Reversible Network Junctions(Basel : MDPI, 2018-01-19) Das, Amit; Sallat, Aladdin; Böhme, Frank; Sarlin, Essi; Vuorinen, Jyrki; Vennemann, Norbert; Heinrich, Gert; Stöckelhuber, Klaus WernerIn this work, we report about the mechanical relaxation characteristics of an intrinsically self-healable imidazole modified commercial rubber. This kind of self-healing rubber was prepared by melt mixing of 1-butyl imidazole with bromo-butyl rubber (bromine modified isoprene-isobutylene copolymer, BIIR). By this melt mixing process, the reactive allylic bromine of bromo-butyl rubber was converted into imidazole bromide salt. The resulting development of an ionic character to the polymer backbone leads to an ionic association of the groups which ultimately results to the formation of a network structure of the rubber chains. The modified BIIR thus behaves like a robust crosslinked rubber and shows unusual self-healing properties. The non-covalent reversible network has been studied in detail with respect to stress relaxation experiments, scanning electron microscopic and X-ray scattering.
- ItemViscoelastic and self-healing behavior of silica filled ionically modified poly(isobutylene-co-isoprene) rubber(London : RSC Publishing, 2018) Sallat, Aladdin; Das, Amit; Schaber, Jana; Scheler, Ulrich; Bhagavatheswaran, Eshwaran S.; Stöckelhuber, Klaus W.; Heinrich, Gert; Voit, Brigitte; Böhme, FrankRubber composites were prepared by mixing bromobutyl rubber (BIIR) with silica particles in the presence of 1-butylimidazole. In addition to pristine (precipitated) silica, silanized particles with aliphatic or imidazolium functional groups, respectively, were used as filler. The silanization was carried out either separately or in situ during compounding. The silanized particles were characterized by TGA, 1H-29Si cross polarization (CP)/MAS NMR, and Zeta potential measurements. During compounding, the bromine groups of BIIR were converted with 1-butylimidazole to ionic imidazolium groups which formed a dynamic network by ionic association. Based on DMA temperature and strain sweep measurements as well as cyclic tensile tests and stress-strain measurements it could be concluded that interactions between the ionic groups and interactions with the functional groups of the silica particles strongly influence the mechanical and viscoelastic behavior of the composites. A particularly pronounced reinforcing effect was observed for the composite with pristine silica, which was attributed to acid-base interactions between the silanol and imidazolium groups. In composites with alkyl or imidazolium functionalized silica particles, the interactions between the filler and the rubber matrix form dynamic networks with pronounced self-healing behavior and excellent tensile strength values of up to 19 MPa. This new approach in utilizing filler-matrix interactions in the formation of dynamic networks opens up new avenues in designing new kinds of particle-reinforced self-healing elastomeric materials with high technological relevance.