Chlorobutyl Rubber Research Articles

Static and Dynamic Mechanical Properties of Chlorobutyl Rubber Composites with Variable Sulfur/Accelerator Ratio

The Composite based on CIIR and variable sulfur/accelerator ratio were prepared by compounding and vulcanizing process. Tensile properties and dynamic mechanical properties of CIIR were studied. The results indicate that tensile strength and loss factor are influenced by sulfur/ accelerator ratio. Tensile strength and modulus are improved with increasing sulfur/accelerator ratio while loss factor decrease with increasing sulfur/ accelerator ratio.

Sieciowanie i reakcje interelastomerowe w mieszaninach kauczukow butadienowo-styrenowego i chlorobutylowego

Blends of styrene butadiene and chlorobutyl rubber in various mass ratios were prepared according to standard procedures in a laboratory mill. The blends were heated to 433 K in the presence of a metal ion donor (ZnO, Fe 2 O 3 or zinc powder). The influence of the blend composition and amount of metal ion donor on the degree of interelastomer crosslinking of the rubbers was investigated. Thermal treatment and the resultant crosslinking of the blends led to changes in their morphology. On the basis of IR spectra (Figs. 2, 7, Table 2, 7), it was confirmed that crosslinking proceeds as a result of Friedel-Crafts interelastomer alkylation of the SBR phenyl ring by the CIIR polihalogenic elastomers (Scheme A). Moreover, the autoalkylation of these rings by SBR vinyl side groups and 1,4-cis-butadiene monomers were catalyzed by aprotic Lewis acids (ZnCl 2 , FeCl 3 ) generated in situ in the reaction of CIIR with the metal ion donor. The degree of blend crosslinking increased with an increase in the content of CIIR and the metal ion donor. The best results were obtained for mixtures containing more that 50 % CIIR and 2—4 parts by wt. of ZnO in respect to 100 parts by wt. of CIIR (Figs. 1, 4, 6; Tables 1, 3, 4, 6). The new, unconventional method could be applied for the crosslinking of rubber blends with selected fillers (Fig. 5, Table 5).

Degradation of chlorinated butenes and butadienes in granular iron columns

Manufacturing facilities for production of chlorobutyl rubber have the potential to release a mixture of at least 5 chlorinated butenes and butadienes including trans-1,4-dichlorobutene-2 (1,4-DCB-2), 3,4-dichlorobutene-1 (3,4-DCB-1), 2,3,4-trichlorobutene-1 (TCB), 2-chlorobutadiene-1,3 (chloroprene) and 2,3-dichlorobutadiene-1,3 (DCBD) into groundwater environment. To evaluate the potential of using granular iron in the remediation of the above contaminants, a series of column experiments were conducted. Degradation of all 5 compounds followed pseudo–first-order kinetics. The three chlorinated butenes degraded much faster (surface area normalized half-lives, t1/2′, ranged from 1.6 to 5.2 min m2/mL) than the 2 chlorinated butadienes (t1/2′ ranged from 102 to 197 min m2/mL). All contaminants fully dechlorinated by granular iron to 1,3-butadiene as a common reaction intermediate that then degraded to a mixture of relatively non-harmful end products consisting of 1-butene, cis-2-butene, trans-2-butene and n-butane. Based on the kinetic data, product distributions, and chlorine mass balances, reaction pathways for these compounds are proposed. For the chlorinated butenes, 3,4-DCB-1 and TCB, undergo reductive β-elimination reactions resulting in 1,3-butadiene and chloroprene intermediates. Dechlorination of 1,4-DCB-2 to 1,3-butadiene occurs through a reductive elimination similar to reductive β-elimination. For dechlorination of the two chlorinated butadienes, chloroprene and DCBD, dechlorination occurs through a hydrogenolysis pathway. The common non-chlorinated intermediate, 1,3-butadiene, undergoes catalytic hydrogenation resulting in a mixture of butane isomers and n-butane. The results suggest that granular iron is an effective material for treatment of groundwater contaminated with these compounds.

Dielectric Properties of PMN/CB/CIIR Composites

The Magnesium Niobate-Lead Titanate (PMN) / conductive carbon black (CB)/ chlorobutyl rubber(CIIR) composites were prepared by blending-vulcanization method, and the dielectric properties were studied. The results showed that the dielectric constant and dielectric loss of composites increased nonlinearly when increasing the content of PMN or CB. From the curve of dielectric constant vs frequency, it is obtained that in the frequency range from 103 to 106 Hz, the dielectric constant of PMN/CB/CIIR composites decreased with the frequency increasing and the dielectric constants are more stable under high frequency.

Damping characteristics of chlorobutyl rubber/poly(ethyl acrylate)/piezoelectric ceramic/carbon black composites

AbstractIn this study, a new kind of damping composite consisting of chlorobutyl rubber, poly(ethyl acrylate), piezoelectric ceramic (PZT), and carbon black (CB) was prepared, and some efforts were made to characterize the damping behavior and explore the damping mechanism. The damping behaviors of the composites were mainly decided by the contents of CB and PZT. When an external vibration was exerted on the composites, the mechanical energy of vibration was transformed into electric energy by PZT; if the resistance was adjusted to a suitable range by the variation of the CB content, the composites could behave as semiconductors: the electric energy could not be transferred to the surface of the material but rather was dissipated as thermal energy. For this system, when the contents of CB and PZT were between 10 and 30 vol %, respectively, the volume resistivity was between 105 and 109.5 Ω cm, and a good damping performance could be achieved. On the basis of the results, a theoretical model is proposed to explain the damping performance of the composites. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008

Damping mechanism of chlorobutyl rubber and phenolic resin vulcanized blends

An intensive study has been undertaken on the damping mechanism of chlorinated butyl rubber (CIIR) and phenolic resin (PR) vulcanized blends. Evidence from morphology observations of blend sections by scanning electron microscopy, extraction experiments, molecular weight analysis by gel permeation chromatography indicates that except a part of PR crosslinked with CIIR, the others remain linear and disperse in the CIIR matrix to form a two-phase continuity. The tan δ curves of blend without striking peak split from the dynamic mechanical spectra and inward shift of glass transition of linear PR suggests that cured CIIR and linear PR is miscible to a certain extent, thus, the phase separation in the blends can be described as slight phase separation. There observations are interpreted in terms of variations of free volume characterized by positron annihilation lifetime spectroscopy.

EPDM/CIIR Blends: Effect of EPDM Grade on Mechanical Properties

Blends of chlorobutyl rubber (CIIR) with two grades of ethylene-propylene diene monomer rubber (EPDM) were prepared and the effect of blend ratio on the cure characteristics, hot air ageing resistance, steam ageing resistance, and mechanical properties were evaluated. The blend of CIIR with EPDM grade 301 T showed additive behavior and the blend with the other grade of EPDM (NDR 4640) showed synergistic behavior.

BIMS/filler interactions. I. Effects of filler structure

AbstractPolymer/filler interactions have been found to affect the performance of tire tread, sidewall, innerliner, or carcass and other industrial rubber products that are all based on filled elastomers. Identification of types of various polymer/filler interactions and ranking of their impacts have been elusive. Isobutylene‐based polymers have relatively saturated structures and contain very low concentrations of functional group. Examples are BIMS (a brominated isobutylene/p‐methylstyrene copolymer) containing p‐bromomethylstyrene and p‐methylstyrene; bromobutyl rubber containing Br and olefin; chlorobutyl rubber containing Cl and olefin; and butyl rubber containing olefin. On the other hand, high diene rubbers, such as polybutadiene rubber, polyisoprene rubber, and styrene/butadiene rubber, have unsaturated backbones and high olefin contents. Hence, different types and extents of interaction with reinforcing fillers, such as carbon black (CB) or silica, are expected in these two classes of elastomer. This work employs bound rubber (solvent extraction), viscoelasticity, stress–strain measurements, and solid state NMR to identify, differentiate, and scale polymer/filler interactions in unvulcanized BIMS/CB, BIMS/silica, SBR/CB, and SBR/silica composites, where SBR denotes a styrene/butadiene rubber. Four different types of CB and one type of silica have been studied. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 4943–4956, 2006

Influence of turbulent mixing on fast polymerization reactions

AbstractInvestigations on development of a macrokinetics approach were generalized to the analysis of fast chemical reactions, mainly using cationic polymerization of isobutylene as an example, which is a new class of liquid‐phase processes. The removal of diffusional constraints on polymer synthesis, by intensification of turbulent mixing in the reaction zone, makes it possible to calculate the kinetic parameters of polymerization and polymer‐analogous reactions, to optimize the molecular characteristics of polymeric products obtained, and to control the character of the process as a whole. The laws pertaining to the progression of fast processes are considered for the synthesis of separate polymers, in particular stereoregular polydienes, ethylene–propylene copolymers, and chlorobutyl rubber. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 613–624, 2004

Effect of butyl rubber type on properties of polyamide and butyl rubber blends

AbstractPolyamide‐12 was blended with butyl rubber, bromobutyl rubber, and chlorobutyl rubber with and without a sulfur curing system. Mechanical properties for dynamically vulcanized blends generally exceed those made with no vulcanization. Chlorobutyl‐containing blends prepared by dynamic vulcanization have higher tensile strength and elongation at break values in comparison to those made from other butyl rubbers. For a variety of polyamide/rubber blends made by dynamic vulcanization, there is very little effect of rubber percentage unsaturation and Mooney viscosity on the mechanical properties of the blends. In chlorobutyl‐containing blends prepared by dynamic vulcanization, the swelling index values attributed to the rubber portion decrease as rubber content decreases, and it is likely that the polyamide phase completely surrounds the rubber particles at compositions exceeding approximately 25% polyamide. Swelling index results can be correlated with elongation at break values for similar blends. The results of differential scanning calorimetry suggest that the polyamide phase is not a neutral component in high shear mixing with butyl rubbers with or without curing agents. Rheological studies indicate strong non‐Newtonian behavior for all blends of polyamide‐12 with butyl rubbers. Scanning electron microscopy on polyamide‐12/butyl rubber blends indicates compatibility for butyl rubbers in the order of chlorobutyl > bromobutyl > butyl rubber. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 1423–1435, 2004

A study of dynamic vulcanization for polyamide‐12 and chlorobutyl rubber

AbstractPolyamide‐12 and chlorobutyl rubber were blended by dynamic vulcanization in a high shear environment using curing systems based on sulfur, dithiocarbamate/ZnO, and 4,4‐methylenebiscyclohexylamine/MgO. As expected, all blends with curing agents show increased tensile strength and elongation at break in comparison to blends without curing agents. Maximum mechanical properties are obtained at relatively low levels of curing agent in all systems. Hexane extraction of the mixtures and measurement of percentage of insolubles along with the swelling index of the rubber phase confirm that a high level of cure is achieved at low levels of curing agent. Although the curatives are designed for the rubber phase, differential scanning calorimetry results indicate that both phases are affected during the dynamic vulcanization process, with polyamide‐12 showing a reduced melting temperature that is indicative of molecular weight reduction, structure changes, or reaction with the rubber phase. Scanning electron microscopy results indicate that phase size is reduced with increased blending time and level of curing agent. Rheological studies indicate that blends containing curing agents exhibit non‐Newtonian behavior to a greater extent than polyamide or nonvulcanized polyamide/chlorobutyl rubber blends. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 871–880, 2003

Adhesion of elastomers: Dwell time effects

The strength of adhesion of elastomers to rigid substrates generally increases with time of contact. This effect has been studied for samples of butyl and chlorobutyl rubber adhering to some rigid substrates. The peel strength increased continuously over long periods of contact until in some cases failure became cohesive within the elastomer layer. At higher temperatures the strength increased more rapidly, consistent with the WLF relation governing molecular motions. It is postulated that slow molecular rearrangements occur at the interface and increase the bond strength. A criterion for the observed transition from interfacial to cohesive failure is suggested.

Characteristics of Dehydrochlorination of Industrial and Purified Chloro-Butyl Rubber

Characteristics of Dehydrochlorination of Industrial and Purified Chloro-Butyl Rubber

Covulcanisation of natural rubber and chlorobutyl rubber. Effect of curative diffusion between phases and ZnCl2 addition

Natural rubber (NR) and chlorobutyl rubber (CIIR) were compounded with various formulations containing tetramethylthiuram disulphide (TMTD), sulphur, and ZnO, and masterbatches of these compounds were blended in a 70 : 30 NR/CIIR ratio and vulcanised in a press at 150°C. Crosslink densities of vulcanisates were determined by swelling and tensile properties measured. In formulations in which the concentration gradient permitted the diffusion of TMTD and sulphur to a CIIR phase containing ZnO, tensile strengths were slightly better than 70% of the values of NR compounds of similar crosslink densities. In formulations in which TMTD and sulphur diffused to the faster curing NR phase, blend properties were also better than 70% of those of NR compounds, but at higher crosslink densities, tensile strengths and elongation at break decreased in parallel. This was attributed to failure in a layer of more highly crosslinked material formed within the NR phase close to the interface. Although ZnCl2 can crosslink CIIR to NR, thus ensuring good interfacial bonding, the addition of ZnCl2 to the CIIR masterbatch led to attack on the TMTD accelerator and a significant reduction in crosslink density and tensile properties of blends.

Vulcanization of chlorobutyl rubber. I. The identification of crosslink precursors in compounds containing ZnO/ZnCl2

Chlorinated poly(isoprene-coisobutylene) (CIIR or chloro-butyl) was characterized by Nuclear Magnetic Resonance. Compounds with ZnO, ZnCl2, and ZnO/ZnCl2 were vulcanized in a DSC at a programmed heating rate and isothermally at 150°C in a press. Crosslink densities were determined by swelling and extracted ZnCl2 analyzed by atomic absorption. ZnCl2 formation precedes crosslinking, and at equilibrium only 50% of the chlorine in the rubber is extractable as ZnCl2. ZnCl2 promotes crosslinking, and its addition to formulations decreases but does not eliminate the induction period prior to crosslinking. Dehydrohalogenation, which is catalyzed by ZnCl2 in an autocatalytic process, is accompanied by the formation of conjugated diene butyl on the polymer chain. It is demonstrated that both species, not only ZnCl2, are necessary precursors to crosslink formation. Moist ZnCl2 catalyzes dehydrohalogenation but not crosslinking, while ZnO does not promote either reaction. CIIR can be crosslinked to polybutadiene and to polyisoprene, no induction period applying when ZnCl2 is present in the formulation, and high crosslink densities develop in blends precipitated from solution. Severe reversion occurs in formulations where there is insufficient ZnO to trap all of the HCl evolved. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 2290–2301, 2000

Vulcanization of chlorobutyl rubber. III. Reaction mechanisms in compounds containing combinations of zinc dimethyldithiocarbamate, tetramethylthiuram disulfide, sulfur, and ZnO

Poly(isoprene-co-isobutylene) (IIR or butyl) and chlorinated poly(isoprene-co-isobutylene) (CIIR or chlorobutyl) compounds containing combinations of zinc dimethyldithiocarbamate [Zn2(dmtc)4], tetramethylthiuram disulfide (TMTD), sulfur, and ZnO were vulcanized at 150°C, the reaction was stopped at various points, crosslink densities were determined by swelling, and the concentrations of residual curatives and extractable reaction intermediates and products were determined by high-performance liquid chromatography and atomic absorption (ZnCl2). In compounds that did not contain zinc, CIIR crosslinked more slowly than IIR and crosslinking could be explained by the same mechanism as applies to the vulcanization to highly unsaturated rubbers like polyisoprene. In zinc containing compounds, CIIR crosslinked faster because of dehydrohalogenation reactions that led to carbon–carbon crosslinks. As found with ZnO/ZnCl2 formulations, both ZnCl2 and conjugated diene butyl are essential precursors to crosslink formation. Zn2(dmtc)4 can trap HCl, thus preventing reversion and may also initiate dehydrohalogenation. When the equilibrium crosslink density is reached, 50% of the chlorine originally present in the rubber is extractable as ZnCl2 and the remainder as dimethylthiocarbamic acid chloride. A mechanism to account for dehydrochlorination and crosslinking in the presence of Zn2(dmtc)4 is presented. In compounds with sulfur, crosslinking occurs via accelerated sulfur vulcanization and chlorine abstraction, leading to higher crosslink densities than is achieved with either curative system on its own. Carbon–carbon crosslinks predominate, the slower, accelerated sulfur reaction, making a lesser contribution to the overall reaction. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 79: 1309–1316, 2001

Vulcanization of chlorobutyl rubber. II. A revised cationic mechanism of ZnO/ZnCl2 initiated crosslinking

Data relating to the ZnO/ZnCl2-accelerated vulcanization of chlorinated poly(isoprene-coisobutylene) (CIIR or chloro-butyl) is examined. ZnCl2 and conjugated diene butyl units on the polymer chain are both precursors to crosslinking, and a revised cationic mechanism is proposed to account for crosslinking, taking into account the involvement of conjugated diene butyl in the process. It is demonstrated that Zn2OCl2 will catalyze dehydrohalogenation, and the formation of catalytic amounts of Zn2OCl2 by the reaction of ZnCl with ZnO, followed by H+ abstraction to give Zn2OCl2 and HCl, is essential in the overall crosslinking reaction sequence. The HCl is trapped by ZnO as ZnCl2. It is proposed that the abstraction by Zn2OCl2 of HCl in a concerted reaction leads to Zn(OH)Cl and ZnCl2. Zn(OH)Cl remains in the polymer as an unextractable salt, while 50% of the chlorine in the rubber is extracted as ZnCl2 when compounds reach their equilibrium crosslink density. ZnCl2 initiates crosslinking by the abstraction of chlorine from the chain, but a crosslink will only result when a carbocation on a dechlorinated isoprenoid unit is close to a conjugated diene butyl on an adjacent chain; if not, dehydrohalogenation will result in the formation of a further conjugated diene butyl unit at that point in the chain. The maximum crosslink density achieved is only 1/4 that theoretically possible, as crosslinking restricts chain movement and limits the number of chance meetings between carbocations on the polymer and conjugated diene butyl units. Zinc stearate promotes dehydrohalogenation, ZnCl2 being the only chloro-zinc salt formed. Reversion occurs in compounds where there is insufficient ZnO to trap all of the chlorine present in the rubber. HCl per se does not attack the polymer, but promotes reversion only in the presence of carbocations on the chain, i.e., during the crosslinking process. Trapping of HCl by ZnO prevents reversion. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 2302–2310, 2000

Use of pyrolysis-GC–MS to assess the thermal degradation behaviour of polymers containing chlorine II. Thermal stability characteristics of Neoprene/chlorobutyl rubber composites, before and after artificial ageing

Some composites containing a cross-linked blend of Neoprene and “chlorobutyl rubber” have been artificially aged at temperatures of 35 and 80°C for up to 3 months. Overall rate constants for their degradation at 387°C, before and after the ageing, have been measured by pyrolysis-GC–MS in order to assess whether the ageing has had any effect on their thermal stability. The results show that the low-temperature ageing treatment has caused no detectable deterioration in the thermal stability of the composites as measured at the higher temperature. The mean value of the first order rate constant, determined from a reproducibility test using 21 data points, is 0.0205±0.0036 s −1 at 387°C (68% confidence limit). The scatter is attributed to macro inhomogeneity in the composition of the samples. With respect to the different batch samples, the mean values of the specific rates of degradation of the two samples were found to lie within the standard deviation of the overall scatter. The effects of the artificial ageing have also been assessed by comparing the resolved gas chromatograms of the many products obtained from the 387°C pyrolyses of the control and the aged samples. These chromatograms are virtually identical, and this suggests that not only is the thermal stability unaffected, but also that the detailed mechanisms of the degradation have not changed with ageing. Mass spectra and mass chromatograms have also been examined in order to assess the general structures present within the wide variety of degradation products. High-yield low molecular weight components include isomeric butenes (butene-1, butene-2, and 2-methyl-propene-1), but it is difficult to distinguish between these because of the similarities in their mass spectra. There is also evidence for oligomeric butenes and many other aliphatic hydrocarbons (both saturated and unsaturated, linear and cyclic) with molecular weights up to several hundred. Other products include hydrogen chloride and chlorinated hydrocarbons, plus a few other hetero-compounds which can be related to known minor additives in the composites. Hydrogen chloride has also been established as a product at its detection limit when 100 μg of the chlorobutyl rubber component alone were heated at 100°C for 10 s, despite the fact that this material contains less than 2 wt% of chlorine.

Graft copolymerization of polyisobutylene and polychlorobutyl onto polystyrene waste

Poly(styrene-graft-isobutylene) (PS-graft-PIB) and poly(styrene-graft-chlorobutyl) (PS- graft-Cl-IIR) have been synthesized by the grafting of PIB and Cl-IIR onto polystyrene waste in conjunction with AlCl3/HCl as catalyst. The grafting efficiency (GE) and overall graft composition have been studied. The synthesized graft polymers were purified and characterized by IR and 1 HN MR analysis. Thermogravimetric analysis (TG) and differential scanning calorimetry (DSC) were used to study the thermal characteristics of the graft. It is shown that the grafting induces better thermal stability for polystyrene. # 1999 Society of Chemical Industry grafting of chlorobutyl rubber (Cl-IIR), polyisobuty- lene (PIB) and modified polyisobutylene (MPIB) onto PS using AlCl3/HCl as catalyst is considered. The main objectives of this study were to demonstrate the synthesis of pure or virtually pure polystyrene-graft- chlorobutyl rubber (PS-graft-Cl-IIR), polystyrene- graft-polyisobutylene (PS-graft-PIB) and polystyrene- graft-modified polyisobutylene (PS-graft-MPIB), and to study the influence of synthesis conditions on GE, graft composition and graft properties. The character- ization of the micro-architecture of the graft copoly- mer, together with an examination of its physical properties and correlation of synthetic variables with polymer structure of these novel materials, are other goals of this paper.

Moisture absorption and desorption of different rubber lyophilisation closures

Rubber closures form a critical barrier in the protection of freeze-dried products against the uptake of moisture. In this study, the moisture absorption of different rubber lyophilisation closures at different temperatures and relative humidities (RH) was evaluated, using a Karl Fischer titration–oven combination. Also, the moisture absorption during steam sterilisation and the moisture desorption during subsequent drying of the stoppers was investigated. Five chlorobutyl and three bromobutyl rubber stoppers were used in this study. The moisture level from the stoppers stored during 85 days at 95% RH–40°C was in the range 0.85–1.49% for the bromobutyl stoppers and in the range 1.71–1.99% for the chlorobutyl stoppers, depending on the stopper formulation. The same trend in moisture absorption was seen during steam sterilisation, where the moisture uptake of the chlorobutyl rubber closures was higher (0.82–0.9%) compared with the bromobutyl closures (0.41–0.57%). Moisture desorption after steam sterilisation, during drying at 100°C, depended on the treatment of the stopper, e.g., siliconation. Finally the moisture absorption of a freeze-dried formulation was evaluated after venting the lyophilisation chamber with air, dry nitrogen, dry helium or closing the vials under vacuum with two different rubber closures. There was no moisture desorption in the rubber closures during the lyophilisation process. Moisture uptake of the freeze-dried cakes depended on the venting procedure of the lyophilisation chamber after freeze-drying.