Effect of zinc stearate on the rheology of ionic elastomer based on carboxylated nitrile rubber

Monsanto rheometry, melt viscometry, differential scanning calorimetry, and dynamic mechanical spectroscopy have been used to study the effects of zinc stearate on the rheological behavior of ionomer based on carboxylated nitrile rubber (XNBR) - zinc oxide (ZnO) system. At temperatures below its melting point, zinc stearate functions as a reinforcing agent for ionomer formation. Above its melting point, it acts as a plasticizer for the ionic domains, thereby facilitating easy processing of the ionomer.     

低温热塑性改性氯醋树脂的研究

对氯醋树脂进行改性以得到具有较低软化点、能用于外科矫形材料的低温热塑性材料。采用共混方式将氯醋树脂、热稳定剂、增塑剂及润滑剂熔合在一起。结果表明。二月桂酸丁基锡用作主热稳定剂，硬脂酸锌和硬脂酸钙作为辅助热稳定剂可以有效延缓氯醋村脂的降解。以DOP（邻苯二甲酸二辛酯）为主增塑剂，ESBO（环氧大豆油）为助增塑剂可以调控树脂的软化点。采用最佳配方可以制得软化点为55℃左右的低温热塑性改性氯醋树脂材料。     

Plasticization of poly(styrene-b-isobutylene-b-styrene) ionomers by acid salts of 2-ethylhexyl-p-dimethylaminobenzoate

Poly(styrene-b-isobutylene-b-styrene) block copolymer ionomer (overall molecular weight = 71,200 g/mole; 25.5 wt% polystyrene, 4.7% sulfonation of phenyl units, 100% neutralized with KOH) was compounded with various organic and inorganic acid salts of 2-ethylhexyl-p-dimethylaminobenzoate (ODAB) to explore the efficacy of these compounds as ionic plasticizers. Results were compared to the same polymer plasticized by zinc stearate. Plasticizers were added to the polymer at levels of ≈5 wt%. Films were prepared by solution casting from tetrachloroethylene. Thermogravimetric analysis (TGA) showed all ODAB derivatives to have lower decomposition temperatures than zinc stearate. Dynamic mechanical analysis (DMA) of the films showed varying degrees of ionic plasticization as evidenced by a lowering of the temperature at which the onset of flow occurred. With the exception of the stearic acid salt of ODAB, all ODAB derivatives were more efficient ionic plasticizers than zinc stearate. Among the ODAB derivatives, the degree of ionic plasticization varied, with the methane sulfonic and p-toluene sulfonic acid salts being most effective, leading to the conclusion that processing temperatures could be tailored to specific applications by choice of plasticizer and level of incorporation.     

New polyisobutylene-based model elastomeric ionomers: RheoLogical behavior

The rheological behavior of sulfonated polyisobutylene based elastomeric ionomers has been studied. The effects of molecular architecture, type of cation, and addition of excess neutralization agent were investigated. The effect of temperature was studied to a limited extent. In a specific case, the influence of an ionic plasticizer, zinc stearate was also examined. It was found that in these telechelic ionomers where the ionic groups are located exclusively at the chain ends, significant Ionic interactions may persist even at 180°C. The zinc-neutralized ionomers had the lowest viscosity as compared to the corresponding potassium- or calcium-neutralized ionomers. The covalent character of zinc is believed responsible for this behavior. Other factors being constant, the triarm based ionomers are more viscous than the monofunctional ionomers. A mixture of monofunctional ionomers with the triarm, species is a model for dangling chain ends, and results in a slight lowering of the viscosity under the conditions studied. Zinc stearate acts as an ionic plasticizer. Upon the addition of 15 percent by weight of zinc-stearate to the ionomer, the low shear rate viscosity drops by several orders of magnitude and renders the ionomer thermally processable at moderate temperatures.     

Ionic thermoplastic elastomer based on maleated epdm rubber. I. Effect of zinc stearate

Neutralization of maleated EPDM rubber by zinc oxide results in an ionic elastomer. The rate and extent of the neutralization reaction increase by addition of stearic acid. Although the rubber is not easy processable as such, incorporation of zinc stearate at a loading of 30 phr makes the rubber behave the rubber behave like a thermoplastic during high temperature (≥ 150°C) processing. Furthermore, zinc stearate causes improvement in the physical properties of the rubber under ambient conditions. It is believed that zinc stearate acts as a reinforcing filler under ambient conditions and as a plasticizer for the ionic domains at higher temperature (that is, above its melting point, 128°C). The conclusions are based on the results of dynamic mechanical, rheological, and infrared spectroscopic studies. © 1996 John Wiley & Sons, Inc.     

Viscoelastic properties of sulfonated ethylene–propylene terpolymer neutralized with zinc cation

Stress–relaxation measurements in uniaxial extension, in the terminal zone, were made of sulfonated ethylene–propylene terpolymer (EPDM), neutralized with zinc cation. The sulfonation levels were 15 to 20 meq/100 g polymer (0.47 and 0.62 mol %), and for each level the effect of the ionic plasticizer, zinc stearate, was investigated. For all the polymers, the decay of the modulus with elapsed time was gradual and featureless, reflecting a broad distribution of relaxation times. Sensitivity of the ionomers' structures to thermal history before an experiment was suggested by irreproducibility in the magnitudes, but not the distribution, of relaxation times at a given temperature. For polymers containing zinc stearate measured at 80°C, the amount of permanent set was low for relaxation up to about 20h, but increased rapidly with additional hours of stretch. Time–temperature superposition did not apply. Composite curves were constructed by matching the stress–relaxation response at short times; moduli measured at long times fell above the composite curve. The shapes of the composite curves were similar, regardless of the level of EPDM sulfonation or the presence of zinc stearate. The apparent Arrhenius activation energy for short-time relaxation at similar levels of the modulus was about 35 kcal/mol at 140°C for the unplasticized polymers and about 70 kcal/mol at 90°C for the polymers containing zinc stearate, in contrast to the usual effect of plasticizer on the rate of relaxation of amorphous polymers except near the glass transition temperature.     

Sulphonated polyisobutylene telechelic ionomers: 12. Solid-state mechanical properties

The solid-state mechanical properties of well defined sulphonated polyisobutylene telechelic ionomers are presented. Specifically, the effect of (1) molecular architecture, (2) molecular weight, (3) type of cation used for neutralization and (4) excess neutralizing agent has been investigated. In addition, the effect of moisture and ionic plasticizer on the stress-strain behaviour has also been studied.

These ionomers do not display the characteristic small-angle X-ray scattering (SAXS) peak, which is indicative of the presence of clusters, above a number-average molecular weight of about 10 000. However, below this molecular weight a weak shoulder is sometimes observed on the SAXS curve. The tri-arm species form a network structure at ambient temperatures which results in materials with good mechanical properties. The mechanical properties of the linear difunctional species are inferior to those of the three-arm star trifunctional species due to a less well developed network structure. The monofunctional species are very tacky at ambient temperatures and cannot be handled as solid materials. However, by their incorporation into the trifunctional systems they do serve as a model for ‘dangling ends’. As expected, these blends display significantly different properties than those possessed with the pure trifunctional species.

Addition of excess neutralizing agent significantly increases the high deformation properties with little effect on Young's modulus. A simple morphological model has been postulated in which it is suggested that the excess neutralizing agent resides at the ionic sites rather than being uniformly distributed throughout the matrix. Zinc-neutralized ionomers show stress-strain behaviour which is comparable to the potassium- and calcium-neutralized materials at ambient conditions, but the softening temperature is lower for the zinc neutralized material. Water absorption in these materials is relatively low. Addition of zinc stearate, an ionic plasticizer, facilitates melt processing by lowering the viscosity at high temperatures yet at ambient temperatures it crystallizes and acts as a reinforcing filler thus increasing Young's modulus.     

Additive interactions in the stabilization of film grade high-density polyethylene. Part I: Stabilization and influence of zinc stearate during melt processing

The melt stabilization activity of some of the most commercially significant phenolic antioxidants and phosphites (alone and in combination), without and with zinc stearate, was studied in high-density polyethylene (HDPE) produced by Phillips catalyst technology. Multiple pass extrusion experiments were used to degrade the polymer melt progressively. The effect of stabilizers was assessed via melt flow rate (MFR) and yellowness index (YI) measurements conducted as a function of the number of passes. The level of the phenolic antioxidant remaining after each extrusion was determined by high-performance liquid chromatography (HPLC). Phenolic antioxidants and phosphites both improved the melt stability of the polymer in terms of elt viscosity retention; the influence of zinc stearate was found to be almost insignificant. However, phosphites and zinc stearate decreased the discoloration caused by the phenolic antioxidants. A correlation was found between the melt stabilization performance of phosphites and their hydroperoxide decomposition efficiency determind via a model hydroperoxide compound. Steric and electronic effects associated with the phosphorus atom influenced the reactivity towards hydroperoxides. Furthermore, high hydrolytic stability did not automatically result in lower efficiency. Besides phosphite molecular structure, stabilization activity was also influenced by the structure of the primary phenolic antioxidant and the presence of zinc stearate.     

Effect of zinc stearate on properties of melt processable ionomer based on sodium salt of sulphonated maleated EPDM rubber

Abstract

Sulphonation of maleated copoly (ethylen/propylen/diene), followed by its neutralisation by sodium hydroxide produces an ionomer containing both carboxylate and sulphonate anions on the backbone. Addition of zinc stearate lowers the melt viscosity of the ionomer, which is higher than the corresponding non-ionomer. Dynamic mechanical thermal analysis shows that zinc stearate acts as a low reinforcing filler under ambient conditions and as a plasticiser above 100°C (i.e. above the melting point of zinc stearate). For example, incorporation of zinc stearate causes an increase in storage modulus E′ at 25°C, but a sharp decrease in E′ at 110°C. Furthermore, the plot of tan δ v. temperature reveals that tan δ at the low glass–rubber transition temperature T _g decreases, while tan δ at the high temperature ionic relaxation temperature T _i increases in the presence of zinc stearate. Incorporation of carbon black lowers tan δat T _g and increases tan δ at T _i, thus strengthening the biphasic structure of the ionomer. The ionomer shows higher tensile strength and modulus than the corresponding non-ionomer. Addition of zinc stearate increases the tensile strength and elongation at break, with marginal decrease in modulus. Carbon black increases the stress–strain properties of the zinc stearate filled ionomer. Reprocessability studies of the ionomer filled with zinc stearate and carbon black show that the material can be recycled without a decrease in properties.     

Improving the processability of biodegradable polymer by stearate additive

Maleated poly(propylene carbonate)/calcium stearate (MAPPC/CaSt₂) composite was prepared through melt‐extruding poly(propylene carbonate) (PPC) with maleic anhydride and CaSt₂. The processability, thermal stability, interaction between two components as well as the morphology of the composites were systematically characterized. The flow instability of biodegradable PPC was greatly alleviated due to the incorporation of stearate additive in polymer matrix. It was found that the MAPPC and MAPPC/CaSt₂ composites were more thermostable than pristine PPC under melt‐processing conditions. The melt fluidity of the composites was noticeably superior to that of MAPPC, arising from the lubricating effect of CaSt₂ on the polymer/barrel wall interface as well as from the improvement of resistance to thermal degradation of the composite. The coordination interaction between MAPPC and calcium ion also contributes to the enhanced thermal stability and high melt stability of composites. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Bismaleimide and bisazomethine high temperature polymers

Conjugated aromatic bisazomethine, resulting from the reaction of terephthaldicarboxaldehyde and aniline, has been found to react with bismaleimidodiphenylmethane to provide polymeric compositions with glass transition temperature higher than 300°C. These two materials form a low viscosity melt at ca. 150°C and the melt shows only a small viscosity increase when maintained at 120°C over a period of 8 h. Differential scanning calorimetry (DSC) of this composition shows that upon heating above 200°C, it cures rapidly to produce a thermally stable polymer. Thermal mechanical analysis (TMA) of the cured composition does not detect any softening up to 350°C. In the thermal gravimetric analysis (TGA), no weight loss is observed up to 400°C in air and the material leaves a rather large amount of residue (ca. 60%) even up to 600°C. Dynamic mechanical thermal analysis (DMTA) shows that the polymer maintains its high modulus with increasing temperature up to 250°C.     

Flow properties of plasticized PVC: Reduction to composition and interaction variables

Existing theory of polymer flow has been applied to a definition of shift factors which reduce the widely different melt viscosity/shear rate diagrams of plasticized PVC compounds to well-defined master curves. The master curves are temperature dependent and also define the flow properties of the unplasticized polymer on which a group of plasticized compounds is based. For given plasticizers, the value of the shift factor was found to depend on melt temperature and plasticizer volume fraction. Explicit relationships have been generated for three plasticizer systems; for these, melt viscosity/shear rate data can be precalculated over several decades of shear, and in the temperature range of 150–200°C. Absolute values of the shift factors depend on the type of plasticizer, and a correlation with polymer/diluent interaction parameters has been attempted. Initial results, valid only at high plasticizer volumes and near the reduced melt temperature of a polymer/plasticizer mixture, support the existence of such a correlation.     

Melt flow and mechanical properties of sulfonated butyl rubber ionomers

Study of melt flow properties and mechanical properties of sulfonated butyl rubber ionomers showed that in the case of lithium ionomers addition of zinc stearate lowered obviously the melt viscosity, represented by torque value of a Brabender rheometer, and enhanced tensile strength of the ionomer up to 25% of zinc stearate, while in the case of ethylamine neutralized ionomer addition of zinc stearate lowered the melt viscosity not so obviously as in the case of lithium ionomer and slightly affected the tensile strength. Amine neutralized ionomers exhibited very low permanent sets, while the lithium ionomer showed much higher permanent set, which increased with sulfonate group and amount of zinc stearate added. Increase of neutralization degree below equivalent ratio of 1 significantly raised the melt viscosity and tensile strength. For monovalent cation ionomer, melt viscosity and tensile strength diminished with decreasing ionic potentials, but for divalent cation ionomers with increasing ionic potentials and with decreasing covalent character tensile strength decreased and melt viscosity increased. For different amine neutralized ionomers tensile strength decreased in the following orders: ethylamine > triethylamine > diethylamine; isopropylamine > ethylamine > tertiary butylamine > methylamine; ethylamine > hexylamine > dodecylamine > octadecylamine.     

乙烯/乙酸乙烯酯/甲基丙烯酸离聚体的合成、表征及性能

以乙烯/乙酸乙烯酯/甲基丙烯酸三元嵌段聚合物为基体合成了它的钠、锌盐离聚体。通过FT IR谱图以及DSC、TGA曲线证明了钠、锌离子与甲基丙烯酸发生了反应,玻璃化温度、熔点有提高;同时经过力学性能测试表明合成的离聚体在力学性能方面有改进。硬脂酸锌是离聚体的有效增塑、增强剂,离聚体的拉伸强度随着硬脂酸锌用量的增加而增加,其最大用量为30%。     

不同金属离子及胺中和的磺化丁基橡胶离聚体的性能

研究了不同金属离子及胺中和的磺化丁基橡胶离聚体的熔融流动性及力学性能。结果表明,随着硬脂酸锌加入量的增加,锂离聚体的熔融黏度降低,拉伸强度增大;随离聚体中磺酸基含量的增加,锂离聚体的熔融黏度和拉伸强度增大。对于一价金属离子中和的离聚体,其熔融黏度及拉伸强度随着离子电位的降低而减小;对于二价金属离子中和的离聚体,随着离子电位的下降及共价性的增加,熔融黏度下降而拉伸强度增大。用胺中和的离聚体,硬脂酸锌的影响较小,未加硬脂酸锌的离聚体具有较高的扯断伸长率及较低的永久变形,是良好的热塑性弹性体;随离聚体中磺酸基含量的增加,乙胺离聚体的拉伸强度增大。对于不同胺中和的离聚体,其拉伸强度按下列顺序依次降低：乙胺,三乙胺,二乙胺;乙胺,己胺,十二胺,十八胺。     

The thermal stabilization of polyethylene sulfide

It has been shown that the resistance of certain polyethylene sulfides to thermal degradation can be markedly improved by the addition of small amounts of metal dithiocarbamates, thioureas, or diphenyl acetylene together with a suitable carbodiimide. The extent of degradation, as indicated by the concurrent changes in polymer melt viscosity in the temperature range 220°–250°C, was dramatically reduced, in particular, by a stabilizer comprised of 4% hexamethylenebis(tert-butyl)carbodiimide and 2% diphenylacetylene. At 250°C polyethylene sulfide (Dabco initiated) was stable in the melt viscometer for a period of 8–10 min and the resulting extrudate showed little sign of discoloration. The detailed mechanism of stabilizer action cannot be put forward at this stage because of uncertainty regarding the mode of polymer degradation which could occur by radical or ionic processes.     

Solid polymer electrolytes. VII. Preparation and ionic conductivity of gelled polymer electrolytes based on poly(ethylene glycol) diglycidyl ether cured with α,ω‐diamino poly(propylene oxide)

Crosslinked polymer electrolyte networks were prepared from poly(ethylene glycol) diglycidyl ether blended with an epoxy resin (diglycidyl ether of bisphenol A) in different ratios and then cured with α,ω‐diamino poly(propylene oxide) in the presence of lithium perchlorate (LiClO₄) as a lithium salt. The ionic conductivities of these polymer electrolytes were determined by alternating current (AC) impedance spectroscopy. Propylene carbonate (PC) was used as a plasticizer to form gelled polymer electrolyte networks. The conductivities of the polymer electrolytes containing 46 wt % PC plasticizer were approximately 5 × 10^?4 S cm^?1 at 25°C and approximately 10^?3 S cm^?1 at 85°C. These polymer electrolytes were homogeneous and exhibited good mechanical properties. The effects of the polymer composition, plasticizer content, salt concentration, and temperature on the ionic conductivities of the polymer electrolytes were examined. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 1264–1270, 2004     

Terpolymers. III. Isochronal viscoelastic parameters for terpolymers of vinyl stearate,vinyl acetate,and vinyl chloride

Isochronal viscoelastic parameters were collected for many of the copolymers, terpolymers, and diluent mixtures whose mechanical properties at ambient temperatures were reported in the preceding paper. In the polymeric systems, vinyl stearate, acting as the primary internal plasticizer, was introduced into terpolymers by displacing vinyl acetate from base copolymers of vinyl acetate and vinyl chloride, across the range of composition. In the diluent mixtures, poly(vinyl chloride) was plasticized by di-2-ethylhexyl phthalate across the range of compositions. For direct comparison with the mixtures, vinyl chloride was plasticized by copolymerization with vinyl stearate across the same range of compositions. Moduli for the co- and terpolymers reached the low values characteristic of soft materials at room temperature only through a short range of vinyl stearate composition. At higher internal plasticizer compositions, side-chain crystallization stiffened the samples and raised their moduli. In contrast, moduli for the mixtures decreased steadily with increase in diluent at ambient temperature. The effective use temperature ranges were narrow for the co- and terpolymers but broad for the mixtures. Curve broadening was similar for both types of systems, but reached a maximum at about 40 weight-% plasticizer for the diluent mixtures. The slopes of the glassy modulus with decreasing temperature at 50°C below T_g for the vinyl stearate copolymers were relatively large. However, moduli close to that of poly(vinyl chloride) were reached only near the temperature range associated with the γ-transition. Consequently, this behavior was attributed to motions of the side chains in the glassy matrix. Room temperature moduli, which could be obtained before the onset of melting, were correlated with the fractional side-chain crystallinity for polymers having a high vinyl stearate content. From this relation, the modulus for the hexagonal crystal form of the side-chain crystallites of poly(vinyl stearate) was estimated to be 1.2×10¹⁰ dynes/cm². Moduli for the glassy amorphous phase of this same polymer appeared to have one sixth of this value at 40°C below the glass transition. The glass transition temperature occurred about 10° below the inflection temperature at 10⁹ dynes/cm², as an average for all of the systems studied.     

吡嗪⁃2，3⁃二羧酸镧的合成及其对聚氯乙烯稳定性的作用

以吡嗪?2，3?二羧酸（2，3?PDA）为配体，用硝酸镧和氨水合成了吡嗪?2，3?二羧酸镧（2，3?LPDA）稀土热稳定剂，通过红外光谱分析、元素分析和热分析确定了其分子式；通过静态热稳定实验研究了2，3?LPDA、其他辅助热稳定剂以及2，3?LPDA与硬脂酸锌、硬脂酸钙、季戊四醇的二元和三元复配体系的热稳定性，并对其对聚氯乙烯（PVC）塑化性能和力学性能的影响进行了表征；最后，探究了2，3?LPDA的热稳定机理。结果表明，2，3?LPDA的分子式为La₂（C₆N₂O₄）₂（NO₃）₂·3H₂O；当2，3?LPDA∶硬脂酸锌∶季戊四醇的复配质量比为2∶1∶2时，PVC的热稳定时间可以达到44 min，且复配体系对PVC的塑化性能有明显提高作用，使PVC的拉伸强度显著提升；2，3?LPDA能够减少PVC中的C—Cl的存在，并且可以吸收PVC降解产生的Cl^-，与稀土离子结合生成LaCl₃，从而抑制PVC的降解，达到热稳定效果。