Disruption of the multiplets in poly(styrene-co-methacrylate) ionomers by the addition of aliphatic diacid salts

Dynamic mechanical properties and morphology of poly(styrene-co-sodium methacrylate) ionomers containing disodium salts of aliphatic diacid were investigated. It was found that upon the addition of diacid salts to the ionomers, the position of the matrix loss tangent peak remained constant, but the cluster loss tangent peak shifted to lower temperatures; the size of the matrix loss tangent peak increased, but that of the cluster peak decreased. In addition, the ionomers containing diacid salts showed X-ray diffraction patterns at relatively wide angles but no DSC melting peak. Thus, it was postulated that the organic salts prohibit the ionic groups of the ionomer from forming multiplets, and that the ionic groups of the ionomer, not forming the multiplets, participate in the formation of ionic aggregates with the ionic groups of the diacid salts.     

Ethylene/(meth)acrylic acid ionomers plasticized and reinforced by metal soaps

Metal soaps, also known as fatty acid salts, resemble oligomers of ethylene/methacrylic or ethylene/acrylic acid (E/(M)AA) ionomers, in that they contain carboxylic salt headgroups and long methylene sequences in their hydrocarbon tails. Such soaps might thus be expected to form miscible blends with E/(M)AA ionomers under suitable conditions, providing a separate route to increasing an ionomer's ion content and modifying its physical properties. We show here that the structure and property modifications induced by blending metal soaps into E/(M)AA ionomers are complex, and depend on both the neutralizing cation and on whether the hydrocarbon tails are crystallizable. In the melt at sufficiently high temperatures, all blends show a coassembled structure, where the salt groups of the soap coaggregate with the salt groups on the ionomer; despite the high ion content of these blends, they retain the melt processability characteristic of neat E/(M)AA ionomers of much lower ion content. Non-crystallizable magnesium oleate and magnesium erucate act as permanent plasticizers, lowering the matrix glass transition temperature. Magnesium stearate, whose alkyl tails easily form a rotator phase, can slowly ‘cocrystallize’ with ethylene sequences in the ionomers, leading to high moduli; however, primary crystallization is suppressed in these blends. Finally, while sodium stearate is miscible with the ionomers at elevated temperatures, it phase-separates on cooling, prior to crystallization of the ionomer; such blends are essentially composites of pure stearate and ionomer phases, with their associated individual properties, rather than possessing new structures or properties resulting from coassembly.     

Viscoelastic properties of poly(styrene-co-vinylphosphonate) ionomers

Viscoelastic properties of neat and glycerol plasticized poly(styrene-co-diethyl vinylphosphonate) ionomers were investigated. Nanophase separation of a polar phase occurred due to hydrogen bonding or ionic interactions in the acid derivatives and the metal salts, respectively. Metal–phosphonate ion–dipole interactions were much stronger and more temperature persistent than the hydrogen bonding in the phosphonic acid derivatives, which were manifested by a much broader rubbery region in their viscoelastic behavior. The phosphonate interactions were thermally stable up to >250 °C, and the physically crosslinked network produced suppressed viscous flow of the ionomers to very high temperatures. Time–temperature superposition was not applicable for the SVP ionomers even at an ion content as low as 2.4 mol%. The addition of a polar plasticizer, e.g., glycerol, preferentially solvated the ionic associations and diminished the extent of the rubbery plateau of the ionomer and substantially decreased the terminal relaxation time.     

Structural effects of ionomers on the morphology, isothermal crystallization kinetics and melting behaviors of PET/ionomers

Morphology, isothermal crystallization kinetics and melting behaviors of PET modified by low molecular weight of ionomers with different structures, ethylene-sodium acrylate (AClyn) and styrene-sodium acrylate (SAA-Na), have been investigated by scanning electron microscopy (SEM), differential scanning calorimeter (DSC) and polarizing optical microscopy (POM). At both high and low temperature regions, AClyn and SAA-Na act as heterogeneous nucleating agent to induce the formation of PET nuclei. The presence of benzene side group in SAA-Na increased the interactions between PET and SAA-Na, leading better compatibility of PET/SAA-Na than that of PET/AClyn. Although SAA-Na had less sodium ions than AClyn at the same content, SAA-Na exhibited similar efficiency to enhance the crystallization rate of PET with AClyn. Isothermal kinetic analysis showed that the same growth dimension was obtained for PET/ionomers regardless of the structural difference between AClyn and SAA-Na. After isothermal melt-crystallization, the second peak of multiple melting endotherms of PET/SAA-Na had almost the same value with PET/AClyn.     

Synthesis, physical properties and enzymatic degradation of poly (oxyethylene-b-butylene succinate) ionomers

A series of poly(oxyethylene-b-butylene succinate) (POBS) ionomers were synthesized by a two-step polycondensation of succinic acid and mixed monomers of sodium sulfonated polyethylene glycol (SPEG) and 1,4-butanediol. The composition and chemical structure of these segmented ionomers were determined by ¹H NMR spectroscopy. To evaluate the potential uses of POBS copolymer in disposable applications, we investigated the crystallinity, dynamic mechanical properties and susceptibility to enzymatic hydrolysis. The crystallinity of POBS copolymer decreased considerably with increasing SPEG content because ionic interaction led to retardation of chain folding. Even so, POBS with 0.5 mol% SPEG showed the highest storage modulus among tested samples. This result is attributed to intermolecular interactions. Enzymatic hydrolysis of POBS copolymer occurs more rapidly than homo poly(butylene succinate) and was drastically accelerated with increasing ionic contents. This is attributed to the presence of the ionic group, which not only reduced the crystallinity but also improved hydrophilicity on the POBS surface.     

Dynamic mechanical properties of lightly sulfonated polystryrene ionomers

The effects of counterion type and addition of plasticizers on the dynamic mechanical properties of sulfonated atactic polystyrene (SaPS) containing 2.1 mole percent ionic groups have been investigated. For SaPS neutralized with alkali metal counterions at temperatures below 180°C, the matrix T_g and elastic modulus were not significantly affected by counterion type. However, above 180°C, the breadth of the rubbery plateau significantly decreased with increasing counterion size. Neutralization of SaPS with alkyl ammonium counterions decreased both the matrix T_g and the breadth of the rubbery plateau with increasing counterion size. By incorporating an ionic plasticizer in Na⁺ neutralized SaPS, dynamic mechanical properties were observed to be intermediate of systems neutralized with the alkali metal and alkyl ammonium counterions.     

LDPE接枝马来酸锌离聚物对PP／PA6共混体系相容性的影响

采用ＳＥＭ和动态粘弹谱研究了不同接枝率的ＬＤＰＥ接枝马来酸锌离聚物（ＬＤＰＥ－ｇ－ＭＡＺｎ）对ＰＰ／ＰＡ６共混体系相容性的影响。ＬＤＰＥ－ｇ－ＭＡＺｎ采用熔融法合成,所制样品接枝率分别为１．５％（质量,下同）、４．５％和５．４％。研究结果表明,ＬＤＰＥ－ｇ－ＭＡＺｎ能有效地改善ＰＰ／ＰＡ６共混物的相容性,其相容性随离聚物接枝率的提高而增强。在ＰＰ（９０）／ＰＡ（１０）体系中,加入离聚物后分散相（ＰＡ６）更均匀、粒子尺寸更小,而且随着离聚物接枝率的提高,ＰＡ６颗粒的粒径就越小,分散越匀;在ＰＰ（５０）／ＰＡ（５０）的体系中,离聚物的加入使两相互相贯穿,在动态粘弹谱上表现出Ｔｇ相互靠近,熔断温度有所提高。     

离聚物Surlyn对PBT及PBT／PP共混体系热稳定性的影响及其动力学研究

制备了ＰＢＴ／ＰＰ／Ｓｕｒｌｙｎ的共混样品，用热重分析（ＴＧＡ）、差示热重分析（ＤＴＧ）等方法研究了离聚体Ｓｕｒｌｙｎ对ＰＢＴ及ＰＢＴ／ＰＰ共混体系热稳定性的影响，并进行了动力学处理。结果表明，在所研究的含量范围内（＜１０ＰＨＲ），Ｓｕｒｌｙｎ可提高ＰＢＴ的热稳定性，二者在热降解反应过程中不是彼此独立进行的，而是存在一定的相互作用；ＰＢＴ／ＰＰ共混物呈现一个较简单的热降解过程，Ｓｕｒｌｙｎ的加入可使ＰＢＴ／ＰＰ共混体系热稳定性有所提高，在Ｓｕｒｌｙｎ含量为４～６ＰＨＲ时达到最佳。ＰＢＴ／ＰＰ／Ｓｕｒｌｙｎ三元共混物的动力学参数是：在空气和Ｎ２中的热降解反应级数为１；频律因子为１０２１～１０２３数量级；表观活化能约为２９０ｋＪ／ｍｏｌ。     

Roles of mono- and di-functional organic salts as plasticizer and/or filler in styrene-based ionomers

The plasticization and/or filler effects of sodium salts of hexanoate (Na6), adipate (Na6Na), dodecanedioate (Na12Na), and dodecylbenzenesulfonate (Na12) on the dynamic mechanical properties of styrene-based ionomers were investigated. When a small amount of Na6, having one carboxylate ionic group at one end of alkyl chain, was added to a styrene-methacrylate ionomer, the salt acted as a very effective plasticizer for the ionomer cluster regions. With increasing salt contents, however, the salts became phase-separated and formed bilayer crystalline domains that acted as filler. In the case of the Na12Na and Na6Na salts, containing two carboxylate ionic groups, one at each end of alkyl chain, they formed phase-separated domains, acting as filler, in the methacrylate ionomers. Na12, possessing one sulfonate ionic group at only one end of a long alkyl chain, acted as a plasticizer in a sulfonated polystyrene ionomer. However, an excess amount of Na12 salt also formed phase-separated domains. It was also found that Na12 showed a filler effect only at much higher salt contents in comparison with Na6.     

Fracture behavior of nanocomposites based on poly(ethylene-co-methacrylic acid) ionomers

The fracture behavior of nanocomposites formed from an organoclay, based on montmorillonite (MMT), and a poly(ethylene-co-methacrylic acid) ionomer prepared by melt compounding was investigated using an instrumented impact test. The data were analyzed using the essential work of fracture (EWF) methodology. Transmission electron microscopy revealed that the clay platelets were well-exfoliated in this matrix. The fracture energy of these nanocomposites increased with organoclay addition at low concentrations but decreased with further increase in organoclay concentration with a maximum between 2 and 3 wt% MMT. The initial increase in fracture energy is a result of the higher forces during loading caused by the increase in modulus and yield stress upon addition of clay; however, the fracture energy eventually decreases with further addition of clay owing to the continuous decrease in ductility or deflection during testing. The EWF of fracture analysis showed that the energy per unit area of crack surface formed exhibits a maximum at 2-3 wt% MMT while the energy dissipated per unit volume in the surrounding process zone decreases monotonically for all clay loadings with a transition from ductile to brittle behavior occurring at 7-8 wt% MMT.     

Interactions and mechanical properties of rod-coil ionomer blend

Polymer-polymer blends of rigid-rod and random-coil macromolecules are obtained by ionomer blend formation. The molecular dispersion of the rod molecules in the matrix polymer is achieved by acid-base interactions. The reinforcement effect in terms of the Young's modulus is discussed as a function of the degree of polymerization of the rods. By treating the reinforcer molecule as a fuzzy cylinder the reinforcement effect can be correlated to the reinforcers' size and shape.     

Effect of organoclay on the morphology, phase stability and mechanical properties of polypropylene/polystyrene blends

The effect of organically modified clay on the morphology, phase stability and mechanical properties of polypropylene (PP) and polystyrene (PS) blends was studied using three molecular weight grades of PP. Maleated polypropylene was used, at a PP-g-MA/organoclay ratio of 1, to preferentially promote dispersion of the organoclay in the PP matrix. The MMT content was fixed at 3 wt% based on the PP/PP-g-MA/MMT phase and the PS content was varied from 0-100 wt% in the blend. All blends were processed using a twin screw extruder. The organoclay resides in the PP phase and at the PP/PS interface. The dispersed PS particle size is significantly reduced by the presence of MMT, with maximum decrease observed for the low viscosity PP compared to its blend without MMT. The blends with MMT did not show any change in onset of co-continuity, though MMT shifts the phase inversion composition toward lower PS contents. The phase stability of the blend was significantly improved by the presence of MMT; for blends annealed at 210 °C for 2 h the dispersed phase particle size increased by as much as 10x without MMT with little change was noted with MMT present in the blend. The tensile modulus of blends improved with the addition of MMT at low PS contents. Blends based on the highest molecular weight grade PP showed increase in the tensile yield stress up to 40 wt% PS in the absence of MMT. The tensile strength at break for blend increased slightly with MMT while elongation at break and impact strength decreased in the presence of MMT. Surface energy analysis model was used to predict the orientation and equilibrium position of the clay platelet at the interface based on the surface energies.     

充油SEBS/PP/PS力学性能的研究

以PP、PS为改性剂对充油SEBS进行了改性。研究结果表明:加入PP时,材料的拉伸强度、熔体流动速率和压缩永久变形增大,但其断裂伸长率迅速下降,回弹性逐渐降低;加入PS时,材料的最佳综合性能为硬度54A,拉伸强度16.75MPa,断裂伸长率740%,熔体流动速率0.159g/10min,回弹性64%。     

Ionomer blends: Morphology and mechanical properties

Polymer blends, having one component as an ionomer, can develop an interesting combination of mechanical properties. These properties give such blends some specific advantages as compared to non-ionic homo-polymers. Primary attention is given to blends involving an ionomer and the ionomer precursor polymer. In such blends, synergistic effects can occur in several of the mechanical properties, such as modulus, strength and fracture energy. The enhanced mechanical properties, which occur for relatively low concentrations of the ionomer in the blends, are well above values predicted by the rule of mixtures. This behavior is attributed to the presence in the ionomer component of a higher chain entanglement density and to good adhesion between the dispersed ionomer particles and the polymer matrix. Some discussion, with examples, is also given of other blends having an ionomer as one component and of blends in which a small amount of ionomer is added in order to enhance the miscibility of two otherwise incompatible polymers.     

Conductivity and mechanical properties of well-dispersed single-wall carbon nanotube/polystyrene composite

The morphologies, electrical and mechanical properties and structure of polystyrene (PS) composites with varying concentrations of single-wall carbon nanotubes (SWNT) are analyzed. Using Raman spectroscopy and electron microscopy, we demonstrate that initial thermal annealing of SWNT significantly improves their dispersion in PS. In dielectric measurements, the annealed SWNT/PS composites show higher electrical conductivity and a lower percolation threshold (less than 0.3 wt%) than the raw SWNT/PS composites, which provides further evidence of good dispersion of the annealed SWNT in PS. Raman spectra of composites under tension show good transfer of an applied stress from the polymer matrix to SWNT. However, mechanical moduli of the annealed SWNT/PS composites are only increased slightly. The reason for this discrepancy remains unclear.     

Dynamic mechanical and melt rheological properties of sulfonated poly(butylene succinate) ionomers

A series of poly(butylene succinate) ionomers (PBSi) containing 5-sodium sulfoisophthalate units were prepared by bulk polymerization of succinic acid and 1,4-butanediol in the presence of dimethyl 5-sulfoisophthalate sodium salt (DMSI) up to 5 mol% of diacid monomer. Conspicuous variation of the storage modulus for PBSi was observed, depending on the content of DMSI. The increasing rate of cluster T_g was lower compared to those of amorphous polymer-based ionomers. These results were probably due to the lower clustering ability of semi-crystalline PBSi as compared with amorphous-based ionomers. Non-contact atomic force microscopy confirmed that the size of PBSi-3 clusters was about 40∼50 nm, demonstrating that the clusters were aggregated. Melt rheological analysis was carried out to investigate the effects of ionic groups on the rheological properties as a function of temperature or shear force in the molten state. The melt viscosities of PBSi showed higher values than the parent PBS up to about 190 °C, while with further increasing temperature a falling inflection region of melt viscosity was observed. It was suggested that the relaxation of PBSi chains was due to the thermal dissociation of ionic aggregates.     

Ionomer compatibilised PA6/EVA blends: mechanical properties and morphological characterisation

The compatibilisation of PA6/EVA blends with the addition of an ionomer on the mechanical properties and morphology were studied as a function of ionomer concentration with the primary aim of enhancing the impact strength of PA6 by EVA. The level of EVA was kept at 20%, which formed the dispersed phase, and the ionomer content was varied from 0 to 1.6 wt%. It was found that notched Izod impact strength of PA6/EVA/ionomer blends increased with the incorporation of ionomer to about three times of the value for uncompatibilised PA6/EVA blends. Further, it was observed that on incorporation of the ionomer the tensile strength also increased significantly. Analysis of the tensile data using predictive theories indicated an enhanced interaction of the dispersed phase and the matrix. SEM studies of cryogenically fractured surfaces indicated a decrease in dispersed phase domain size with the addition of the ionomer, while the impact fractured surfaces of PA6/EVA blends indicated extensive deformation with the formation of rumples indicating increased interfacial adhesion as compared to PA6/EVA blends. An attempt has been made to evaluate the compatibilising efficiency of ionomer in PA6/EVA blends.     

磺化乙丙橡胶离聚体的熔融流动性及力学性能

研究了不同因素包括相转移催化剂、磺化度、中和度、中和用阳离子及增塑剂等对磺化乙丙橡胶离聚体的熔融流动性及力学性能的影响。结果表明,在合适条件下可得到Ｂｒａｂｅｎｄｅｒ扭矩为３５～４０Ｎｍ、拉伸强度为２０～２８ＭＰａ、断裂伸长率为５００％～６００％、永久变形小于１０％的热塑性弹性体     

Dynamic mechanical properties and morphology of sulfonated polystyrene ionomers neutralized with mixtures of various cations

Summary The effects of the addition of mixed cations to the acid form sulfonated styrene copolymers on their mechanical properties and morphology were investigated. It was found that the matrix T _g, does not Change with the type of cations. However, the Cluster T _g, ionic moduli, and the Position of the SAXS peak were affected by the type of cations. The decreasing trends of Cluster T _g with increasing the amount of cesium and zinc cations in Na/Cs, Bai Cs, and Ba/Zn mixtures, were explained on the basis of the considerations of the size, Charge, and type of cations, which alter the degree of clustering as weil as ion-hopping mechanism. Received: 7 October 2002/Revised Version: 13 December 2002/ Accepted: 14 December 2002 Correspondence to Joon-Seop Kim     

Miscibility, crystallization and morphologies of syndiotactic polystyrene blends with isotactic polystyrene and with atactic polystyrene

Two-component blends of differing polystyrene (PS), one syndiotactic (sPS) and the other isotactic (iPS) or atactic (aPS), were discussed. The phase behavior, crystallization and microstructure of binary polystyrene blends of sPS/iPS and sPS/aPS with a specific composition of 5/5 weight ratio were investigated using optical microscopy (OM), differential scanning calorimetry, wide-angle X-ray diffraction, scanning and transmission electron microscopy (SEM and TEM). Based on the kinetics of enthalpy recovery, complete miscibility was found for the sPS/aPS blends where a single recovery peak was obtained, whereas phase separation was concluded for the sPS/iPS blends due to the presence of an additional recovery shoulder indicating the heterogeneity in the molten state. These findings were consistent with OM and SEM observations; sPS/iPS exhibits the dual interconnectivity of phase-separated phases resulting from spinodal decomposition.Both iPS and aPS have the same influence on the sPS crystal structure, i.e., dominant β-form sPS and mixed α-/β-form sPS obtained for melt-crystallization at high and low temperatures respectively, but imperfect α-form sPS developed when cold-crystallized at 175 °C. Co-crystallization of iPS and sPS into the common lattice was not observed regardless the thermal treatments, either cold or melt crystallization. Due to its slow process, crystallization of iPS was found to commence always after the completion of sPS crystallization in one-step crystallization kinetics. Segregation of rejected iPS component during sPS crystallization was extensively observed from TEM and SEM images which showed iPS pockets located between sPS lamellar stacks within spherulites, leading to the interfibrillar segregation, which was similar with that observed in the sPS/aPS blends. The addition of iPS (or aPS) component will reduce the overall crystallization rate of the sPS component and the retardation of crystal growth rates can be simply accounted by a dilution effect, keeping the surface nucleation intact. The phase-separated structure in the sPS/iPS blend shows a negligible effect on sPS crystallization and the signature of phase separation disappears after sPS crystallization. Depending on the relative dimensions of the segregated domains and iPS lamellar nucleus, subsequent crystallization of iPS can proceed to result in a crystalline/crystalline blend, or be inhibited to give a crystalline/amorphous blend morphology similar with that of sPS/aPS blends.