This work was focussed on materials from renewable sources for the preparation of rubber composites. Natural rubber from hevea brasiliensis (HNR) and from taraxacum kok-saghyz (TKS) was studied. A sample of HNR with very high molar mass and low content of non rubber components developed unprecedented high level of crystallinity, about 30% after storing for some months at room temperature, with melting point close to 45°C. TKS sample was fully amorphous and remained fully amorphous. In both HNR and TKS samples, fatty acids were the most abundant non rubber components. In the case of TKS, the largely prevailing amount of the unsaturated acids, that have been reported to act as plasticizers for NR, could be responsible of its amorphous nature. Amorphous rubber samples developed strain induced crystallization only at large strain ratios, achieving low degrees of crystallinity, high degrees of axial orientation and superior mechanical properties. The rubber sample being already semicrystalline in the unstretched state revealed a poor development of crystallinity and rather low degree of orientation under strain, with worse mechanical properties. It is thus demonstrated that larger crystallinity and better mechanical properties when stretching is applied to a fully amorphous polymer, as crystallization occurs when polymer chains have a high degree of alignment. Natural rubber was coagulated from hevea latex by using ionic liquids, a quaternary ammonium and an imidazolium salt and sulphur based curing was then investigated. Both such ILs are efficient coagulating agents and secondary accelerators. It is thus demonstrated that ILs can be multifunctional ingredients for rubber compounds. The effect of proteins on sulphur based curing of poly(1,4-cis-isoprene) was studied, by using the bovine serum albumin and the proteins contained in egg white. In spite of the acidic nature of BSA, EW as well as of HNR proteins, faster curing and higher values of MH modulus were obtained. The effect of the bases, constitutional units of proteins, can be hypothesized. Innovative compatibilizer of carbon allotropes was used. It is 2-(2,5-dimethyl-1H-pyrrol-1- yl)-1,3-propanediol, that comes from a biosourced molecule such as serinol. Adduct of SP with CB was prepared by simply heating their mixture and was dispersed in HNR via latex blending. Compound prepared with the CB-SP adduct revealed appreciably lower Payne effect than the compound based on neat CB

Nanometric high aspect ratio fillers and chemical reactivity with the polymer matrix

M. Galimberti;V. Cipolletti;G. Peli;V. Barbera;A. Bernardi;D. Locatelli;
2018

Abstract

This work was focussed on materials from renewable sources for the preparation of rubber composites. Natural rubber from hevea brasiliensis (HNR) and from taraxacum kok-saghyz (TKS) was studied. A sample of HNR with very high molar mass and low content of non rubber components developed unprecedented high level of crystallinity, about 30% after storing for some months at room temperature, with melting point close to 45°C. TKS sample was fully amorphous and remained fully amorphous. In both HNR and TKS samples, fatty acids were the most abundant non rubber components. In the case of TKS, the largely prevailing amount of the unsaturated acids, that have been reported to act as plasticizers for NR, could be responsible of its amorphous nature. Amorphous rubber samples developed strain induced crystallization only at large strain ratios, achieving low degrees of crystallinity, high degrees of axial orientation and superior mechanical properties. The rubber sample being already semicrystalline in the unstretched state revealed a poor development of crystallinity and rather low degree of orientation under strain, with worse mechanical properties. It is thus demonstrated that larger crystallinity and better mechanical properties when stretching is applied to a fully amorphous polymer, as crystallization occurs when polymer chains have a high degree of alignment. Natural rubber was coagulated from hevea latex by using ionic liquids, a quaternary ammonium and an imidazolium salt and sulphur based curing was then investigated. Both such ILs are efficient coagulating agents and secondary accelerators. It is thus demonstrated that ILs can be multifunctional ingredients for rubber compounds. The effect of proteins on sulphur based curing of poly(1,4-cis-isoprene) was studied, by using the bovine serum albumin and the proteins contained in egg white. In spite of the acidic nature of BSA, EW as well as of HNR proteins, faster curing and higher values of MH modulus were obtained. The effect of the bases, constitutional units of proteins, can be hypothesized. Innovative compatibilizer of carbon allotropes was used. It is 2-(2,5-dimethyl-1H-pyrrol-1- yl)-1,3-propanediol, that comes from a biosourced molecule such as serinol. Adduct of SP with CB was prepared by simply heating their mixture and was dispersed in HNR via latex blending. Compound prepared with the CB-SP adduct revealed appreciably lower Payne effect than the compound based on neat CB
Proceedings - ACS Rubber Division
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11311/1122980
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