The ozonolysis of butyl and halobutyl elastomers

The ozonolysis of butyl elastomer and its halogenated derivatives, as well as their model compounds in hexane, was studied. It was found that while the ozonolysis of butyl and chlorobutyl elastomers involves the normal cleavage of olefinic double bonds, the mechanism of ozonolysis of bromobutyl elastomer is more complicated. In the presence of ozone, bromobutyl elastomer was found to rearrange from the exomethylene structure to the bromomethyl structure, thereby generating more in-chain double bonds. This reaction provides an explanation as to why bromobutyl elastomer degrades faster and to a greater extent than chlorobutyl elastomer containing the same number of olefinic double bonds. Different additives were found to have different effects on the chain scission and rearrangement of bromobutyl elastomer. Diphenylamine and triisopropyl phosphite are much more effective than hexylamine and 2,6-di-tert-butyl cresol in inhibiting the chain scission of the bromobutyl elastomer and diphenylamine is more effective than triisopropyl phosphite in suppressing the rearrangement of this elastomer     

The Influence of Flame Retardants on the Thermal Stability of CIS-1,4-Polyisoprene

The effect of flame retardants such as chloroparaffin, antimony trioxide, mixtures of antimony trioxide and chloroparaffin, melamine cyanurate and pentabromotoluene on the thermal properties of cis-1,4-polyisoprene peroxide vulcanizate has been studied. The thermoanalytical curves of elastomers were interpreted. The flame retardants used, except Sb2O3 were found to change the characteristic thermal transitions of polyisoprene and to cause a decrease in its thermal stability. From among the investigated flame retardants only pentabromotoluene favoured the degradation of the elastomer in the range of its first exothermic transition. This revised version was published online in July 2006 with corrections to the Cover Date.     

Effect of the spatial network structure and cross-link density of diene rubbers on their thermal stability and fire hazard

The paper presents the results of investigating the effect of the density and spatial network structure of diene rubbers (NBR and SBR) on their thermal properties and fire hazard. The rubbers were either conventionally cross-linked by means of sulfur and organic peroxide or nonconventionally with the use of iodoform (CH₃I). Based on thermo-kinetic analysis, the destruction activation energy of the elastomers investigated and their vulcanizates was determined under air and inert gas. The analysis of particular stages of their thermal decomposition was also presented. During the combustion of the elastomeric materials obtained, it has been found that their fire hazard depends not only on the elastomer chemical structure but also on the method of its cross-linking.     

Interfacially modified LDPE/GTR composites with non-polar elastomers: From microstructure to macro-behavior

This paper provides some new insights into the mechanism of interaction and modifications in thermoplastic composites based on low density polyethylene (LDPE), ground tire rubber (GTR) and non-polar elastomer. The composites were prepared using a co-rotating twin-screw extruder at variable LDPE/GTR ratio and constant elastomer content. Two types of commercial elastomer were applied: styrene-butadiene-styrene (SBS) block copolymers (Kraton^®) with different topologies (linear/branched) and partially cross-linked butyl rubbers (Kalar^®) with different Mooney viscosities. Processing characteristics, static mechanical properties (tensile strength, elongation at break, hardness), dynamic mechanical properties, thermal properties and morphology of the resulting thermoplastic composites were investigated. Microstructure analysis shows that modification of LDPE/GTR composites with non-polar elastomers caused encapsulation of GTR particles within the elastomer phase. This phenomenon has significant influence on macro-behavior of thermoplastic composites based on LDPE/GTR blends. The results indicate that SBS copolymer improves interfacial interactions between GTR and LDPE, which enhances mechanical and thermal properties of the composites. On the other hand, cross-linked butyl rubber showed partial compatibility with LDPE and low compatibility with GTR particles.     

Activity of fillers in elastomer networks of different structure

The paper deals with interactions between low molecular weight substances and silica. Activity of SiO₂ towards ethylene-propylene-diene rubber (EPDM) also depends on the kind of crosslinking system used. Calcium carbonate, the filler exhibiting low interactions with elastomers does not show any changes in activity, due to application of different crosslinking systems. In our opinion, the observed increase of the fillers activity results from the modification of elastomer chains by crosslinking agents, influence of the latter on the formation of its own network (the so called “structure”) in the elastomer matrix, and above all from nanoheterogeneous distribution of network crosslinks in vulcanizates. The non Gaussian probably bimodal distribution of crosslinks is likely to influence positively properties of elastomers. A similar effect is observed in peroxide vulcanizates of EPM produced with the use of the crosslinking coagents of polar nature. Behaviour of different kinds of carbon black in natural rubber (NR) crosslinked with dicumyl peroxide (DCP), sulphur donors or sulphur with accelerators is discussed. Reinforcing action of carbon black, particularly the active ones, showed to be more effective in sulphur than in peroxide vulcanizates.     

Synthesis of silica in elastomer's matrix

We tried to synthesise silica's fillers in polar and nonpolar elastomers. Di-, tri- and tetraalkoxysilanes were used as a precursor of silica. Such functionality allowed us to obtain a filler with different ratio of crosslinking. We could expect some interactions between elastomer and silanes, which contained additional functional groups. We investigated vulcanizates by using the following methods: crosslink density in toluene and 10% solution of ethylenediamine in toluene, mechanical properties, IR microscopy, DMA. It appeared that alkoxysilanes influenced advantageously on elastomers and properties.     

Thermal properties of diene elastomers

The paper presents the results of investigating the effect of the macromolecule chemical structure and the spatial network structure of butadiene (BR), butadiene-styrene (SBR) and butadiene-acrylonitrile (NBR) rubbers on their thermal properties. The rubbers were cross-linked by the conventional method by means of dicumyl peroxide or sulfur as well as by the non-conventional way using iodoform (CH₃I). The rubber and their vulcanizates were assessed by the derivatographic method (under air) and by means of differential scanning calorimetry (DSC) under inert gas. The thermal cross-linking degree of the polydienes and the efficiency of the cross-linking processes, dependent on both the chemical structure of elastomer macromolecules and their spatial network structure were determined. The cross-linking of elastomers with iodoform changes the thermal properties of polymers, significantly increasing their glass transition temperature during both sample heating and cooling, which results from the increase in mutual interaction of macromolecules connected with their modification with iodine compounds.     

High‐power ultrasonic treatment of butyl rubber gum: Structure and properties

The ultrasonic treatment of butyl rubber gum during extrusion with a grooved‐barrel ultrasonic reactor was carried out at a mean residence time of 3.6 s and at different ultrasonic amplitudes. Gel permeation chromatography, NMR spectroscopy, differential scanning calorimetry, thermogravimetric analysis, and dynamic and mechanical property measurements were performed. The changes in the structure, curing behavior, and physical properties of the gum were found to be highly dependent on the applied ultrasonic amplitude. In particular, the molecular weight of the treated gum decreased and the molecular weight distribution increased with the ultrasonic amplitude. The number of double bonds in the ultrasonically treated gum was less than that in the virgin gum. The dynamic properties of the ultrasonically treated gums also indicated the occurrence of degradation during the ultrasonic treatment. The tensile strength and modulus of the vulcanizates prepared from the treated gums were reduced in comparison with those of the virgin vulcanizate because of degradation. In contrast, the elongation at break was higher. However, no significant changes in the thermal stability between the virgin and treated gums and among the vulcanizates were observed. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 334–344, 2005     

Chemical modification of butyl rubber. III. Butyl rubber with D-maltose derivative as pendant groups

A new type of amphiphilic elastomer was synthesized, which consisted of butyl rubber and a D-maltose derivative as a backbone and side groups, respectively. The synthesis was accomplished by the sequence of the three following reactions: (1) Hydroxyl groups of D-maltonolactone were protected by a trimethylsilyl group. (2) The resulting maltonolactone derivative was subjected to a reaction with chemically modified butyl rubber having pendant amino groups. (3) The protecting trimethylsilyl groups on the maltose residues were removed by treating with tetra-n-butylammonium fluoride. This new amphiphilic elastomer behaved as a thermoplastic elastomer and showed good mechanical properties. The saccharide seg-ments aggregated in the hydrophobic butyl rubber matrix to form a microphase-separated structure, as confirmed by differential scanning calorimetry, transmission electron mi-croscopy, small-angle x-ray scattering, and dynamic mechanical measurements. The ag-gregated saccharide domains are estimated to function both as crosslinking sites and rein-forcing fillers in the rubber matrix. © 1995 John Wiley & Sons, Inc.     

Thermal analyses of polymers. III. Influence of isocyanate structure on the molecular interactions in segmented polyurethanes,

The thermal responses of various polyurethane elastomers in the form of changes in heat capacity, linear expansion, and tensile strain have been examined. Most of the change which can be attributed to the backbone of polyethylene adipate, found in several modes of thermal analysis, are still apparent, though shifted somewhat, among most of the diisocyanate extended elastomers used in this study. Tolylene diisocyanate extension changes the modulus properties markedly, low modulus properties being observed at ambient temperatures. Both hydrogenated MDI and MDI elastomers show comparable expansion and modulus response, whereas the hydrogenated TDI elastomer does not have the same characteristics as TDI-based elastomers. The thermal properties of the hydrogenated TDI elastomer resemble more those exhibited by the polyol mixture extended with hexamethylene diisocyanate, and in addition this latter elastomer exhibits more crystallinity, as shown by the large endotherm in the specific heat measurement. The structure of the diisocyanate naturally changes the behavior of the hard segment.     

Chemical modification of butyl rubber. II. Structure and properties of poly(ethylene oxide)-grafted butyl rubber

Poly(ethylene oxide)-grafted butyl rubbers (IIR-g-PEOs), which were synthesized from potassium salt of polyethylene glycol monomethyl ether (PEGM) and chlorinated butyl rubber, were found to behave like thermoplastic elastomers. The poly(ethylene oxide) (PEO) content of these amphiphilic polymers was ca. 10 wt %, and their PEO lengths were 750, 2000, and 5000, respectively. The grafted segments of PEO in butyl rubber (IIR) aggregated to form the PEO domains in IIR matrix. At constant PEO content, the longer the PEO segment length, the larger the size and the crystallinity of PEO domains became. This PEO domain worked as a cross-linking site and a reinforcing filler. The degree of swelling in water of IIR-g-PEO film that was prepared from PEGM-5000 was largest, but its emulsification ability was smallest among them. © 1995 John Wiley & Sons, Inc.     

Aromatic polyamides. XI. Effect of the halogen substitution on the thermal and flammability behavior of poly(1,4-phenylene terephthalamide)

This article concerns the synthesis and characterization of poly(1,4-phenylene terephthalamide) and halogenated derivatives thereof. It was found that the halogen substitution affected significantly the thermal characteristic and flame resistance of that polyamide. In a nonoxygen atmosphere two-step decomposition process for the halogenated, while only one-step for unsubstituted polyamides were observed. The results supported the previous suggestion, that in the case of the halogenated polyamides the char yield enhancement and the flame resistance improvement are associated with halogen release and ring-forming reactions during their pyrolysis.     

Thermal degradation of butyl acrylate-methyl acrylate-acrylic acid-copolymers

The thermal degradation of copolymers based on butyl acrylate-methyl acrylate-acrylic acid used as acrylic pressure-sensitive adhesives, especially for bonding of plasticizer containing materials, has been investigated using thermogravimetry and pyrolysis-gas chromatography at 250°C. It was observed that during the pyrolysis of butyl acrylate-methyl acrylate-acrylic acid copolymers unsaturated monomers as methyl acrylate, methyl methacrylate, butyl acrylate and butyl methacrylate were formed. During the side-chain butyl acrylate-methyl-acrylate-acrylic acid-copolymer degradation the presence of methyl alcohol and butyl alcohol was observed.     

Solvent‐free fabrication of proton‐conducting membranes based on commercial elastomers

Five different types of elastomers were examined as the matrix materials in the preparation of non‐fluorinated proton exchange membranes utilizing a solvent‐free route via the in situ reaction of sodium 4‐styrenesulfonate (NaSS). The morphology of the elastomer/NaSS vulcanizates was studied to evaluate the effect of polarity, viscosity and saturation degree of the elastomer matrixes. Much better dispersion of NaSS was found in chlorosulfonated polyethylene rubber (CSM) and hydrogenated nitrile butadiene rubber (HNBR) matrixes than in the other three types of elastomer matrixes. For CSM/NaSS and HNBR/NaSS proton exchange membranes, distinctive membrane properties were observed and correlated with their different structure and morphologies. The CSM/NaSS membranes exhibited the proton conductivity as high as ~0.03 S cm^?1 and the selectivity (the ratio of proton conductivity to methanol permeability) higher than that of Nafion. Copyright © 2015 John Wiley & Sons, Ltd.     

Synthesis and characterization of novel fluorinated polyurethane elastomers based on 2,2‐bis[4‐(4‐amino‐2‐trifluoromehyloxyphenyl) phenyl]propane

2,2‐Bis[4‐(4‐amino‐2‐trifluoromehyloxyphenyl) phenyl]propane (BAFPP) was synthesized based on 2‐chlorobenzotrifluoride and bisphenol A and characterized by Fourier transform infrared spectroscopy and nuclear magnetic resonance. BAFPP was used as a chain extender to prepare a series of fluorine‐containing polyurethane elastomers (FPUEs) with different fluorine contents by changing the soft segments and isocyanate index (R). The FPUEs were investigated by water absorption, contact angle, X‐ray photoelectron spectroscopy, thermogravimetric analysis, and microscale combustion calorimetry. The results show that the FPUEs prepared from BAFPP were elastomers that have low surface tension, low water absorption, and good thermal stability. Furthermore, FPUEs also exhibit good flame resistance, and the peak heat release rate of FPUE based on BAFPP (282.9 W/g) is much lower than that of polyurethane elastomer without the F element (537.2 W/g). Copyright © 2011 John Wiley & Sons, Ltd.     

环氧液晶弹性体材料的制备与力学性能研究

传统的液晶弹性体材料多采用丙烯酸酯类或聚硅氧烷类分子,通过自由基聚合制备.然而由于自由基聚合易被氧气阻聚,固化过程收缩率高且内应力大,传统液晶弹性体材料的力学性能并不是很优异.为解决这一问题,本文合成了带有环氧基团的液晶单体和交联剂,使用碘盐作为引发剂,通过光引发阳离子反应,用原位聚合交联法制备了环氧液晶弹性体材料....     

Thermal characterization of the effect of fillers and ionic liquids on the vulcanization and properties of acrylonitrile–butadiene elastomer

Different thermal analysis techniques were used to study the effect of fillers and ionic liquids (ILs) on the vulcanization process, thermal and dynamic mechanical properties of acrylonitrile–butadiene elastomer (NBR). The products of the studies were composites of NBR filled with hydrotalcite, nanosized silica or carbon black. ILs such as 1-butyl-1-methylpyrrolidinium (BMpyrrolBF₄), 1-butyl-4-methylpyridinium (BMpyrBF₄) or 1-butyl-1-methylpiperidinium (BMpipBF₄) tetrafluoroborates were applied to improve the dispersion degree of the curatives and filler particles in the elastomer and to increase the efficiency of vulcanization. The differential scanning calorimetry results indicated that ILs reduced the vulcanization temperature of NBR compounds and increased the homogeneity of cross-link distribution in the elastomer network. NBRs filled with carbon black or silica exhibited similar thermal stabilities, whereas hydrotalcite reduced the temperature of thermal decomposition. The lowest mechanical loss factors were determined for vulcanizates filled with nanosized silica.

     

Synthesis of fullerenol-derived elastomers and conductive elastomers

Utilization of polyhydroxylated C₆₀ in a condensation reaction with diisocyanated oligo(tetramethylene oxide) led to the successful fabrication of elastomeric poly(urethane-ether) networks. These polymer networks exhibit interesting thermal behavior at low temperatures, improved tensile strength and elongation at ambient temperatures, and enhanced thermal mechanical stability at high temperatures. Design of conducting elastomers was made by carrying out an in situ polymerization of conductive polymer precursors in an interpenetrating fashion at the near-surface of polyhydroxylated C₆₀-hypercrosslinked elastomers. Results demonstrated that elastomers with an appreciable conductivity while retaining desirable elastic properties of the network can be achieved. The room-temperature conductivity of polyaniline interpenetrated (IPN) conducting elastomer was found to be 2.0 Scm⁻¹. The tensile strength and elongation at break of one conductive IPN elastomer was found to be 20 MPa and 480%, respectively. Interestingly, the strain dependent conductivity of these conducting elastomers was found to increase progressively above 200% of elongation. These results demonstrated, for the first instance, conductivity measurements of organic conducting elastomers at an elongation length of higher than 300%, showing a r.t. conductivity of >4.0 Scm⁻¹.     

Preparation of microcapsulated ammonium polyphosphate,pentaerythritol with glycidyl methacrylate,butyl methacrylate and their synergistic flame‐ retardancy for ethylene vinyl acetate copolymer

A new series of microcapsules containing pentaerythritol (PER) and ammonium polyphosphate (APP) with glycidyl methacrylate and butyl methacrylate as shell materials were synthesized by in situ polymerization. The structure and performance of the microencapsulated APP and microencapsulated PER were characterized by Fourier transform infrared spectroscopy, X‐ray photoelectron spectroscopy, scanning electron microscopy, and water contact angle. The flame retarded ethylene‐vinyl acetate copolymer (EVA) composites were studied by limiting oxygen index, UL‐94 test, and cone calorimeter. It was found that the microencapsulation of flame retardants (FRs) with the glycidyl methacrylate and butyl methacrylate lead to a decrease in the particle's water solubility and an improvement of the hydrophobicity. Results also demonstrated that the FR properties of EVA/microencapsulated APP/microencapsulated PER composites were better than those of the EVA/APP/PER composites at the same loading of FRs. The thermogravimetric analysis results reflected that the microencapsulated EVA composites had better thermal stability because of the forming of stable char during the combustion. Copyright © 2013 John Wiley & Sons, Ltd.     

Natural rubber biocomposites containing corn,barley and wheat straw

The development of high-performance materials made from available and cheap natural resources is increasing worldwide. A new solution – composites of natural rubber, containing barley, corn and wheat straw as biofillers, was reported and researched. The latest developments and trend's exams of the elastomers filled with cereal straw represent a scientific and technological innovation. The use of straw as a filler for elastomer composites bradens the range of functional properties and reduces the costs of production. The biocomposites are more ecofriendly and give the opportunity to increase the possibility of straw management which is a problematic agricultural waste. The rubber mixtures containing lignocellulosic materials demonstrate a favorable characteristic kinetics of crosslinking. The addition of filler, in an appropriate amount, modified natural rubber vulcanizates, improving mechanical and barrier properties of composites and the ability to damp under the influence of compression stress. Dynamic mechanical analysis showed change in the G′ values of the vulcanizates upon addition of straw. That indicates the presence of strongly developed network of fillers into polymer matrix which ensure of reinforcing character. The negative impact of natural fillers on resistance to thermo-oxidative aging was not observed.