Influence of acrylate processing aid‐based ionomer containing lanthanide (La(III)) ion on thermal stability,fusion, transparency and mechanical properties of rigid poly(vinyl chloride)

An acrylate processing aid (ACR)‐based ionomer containing lanthanide (La(III)) ion was synthesized and the influences of the ionomer on thermal stability, fusion time, transparency and tensile properties of rigid poly(vinyl chloride) (PVC) were investigated. Results revealed that the ionomer with a suitable La(III) content behaved as a good stabilizer as well as processing aid to the rigid PVC product. The ionomer could accelerate fusion of PVC much more quickly than ACR because of the strong interaction between La(III) carboxylate and PVC. Moreover, it exhibited a stabilizing efficiency comparable to lanthanum and calcium stearates (LaSt₃ and CaSt₂). The composite stabilizer of ionomer/zinc stearate (ZnSt₂) exhibited an ability to improve initial discoloration better than LaSt₃/ZnSt₂ and CaSt₂/ZnSt₂ because the ionomer could form a complex with ZnSt₂ much more slowly than LaSt₃ and CaSt₂. The compounds stabilized using ionomer/ZnSt₂ exhibited a transparency comparable to those stabilized using organotin or liquid barium/zinc stabilizers, which was much better than those stabilized using LaSt₃/ZnSt₂ and CaSt₂/ZnSt₂. Copyright © 2011 Society of Chemical Industry     

ESR and FTIR studies on electron beam‐irradiated low‐density polyethylene blends

Low‐density polyethylene (LDPE) composites modified with a resin based on ethylene/methacrylic acid copolymer (surlyn) and/or citric acid were electron beam‐irradiated and investigated by electron spin resonance (ESR) at room temperature. ESR studies were carried out directly after irradiation and after various time intervals up to 72 h postirradiation. The irradiated samples showed the ESR spectrum of seven lines that was assigned to the formation of allyl radical. The nature and yield of the allyl radical of the different LDPE samples were analyzed as a function of time after irradiation. Also, the radical concentration, decay, decay rate, and kinetics of radical decay were evaluated. Fourier transform infrared (FTIR) analysis at a series of different temperatures upon cooling from room temperature to ?175°C and the reverse heating to +125°C was also carried out. The structural changes while cooling and heating of LDPE samples were investigated using FTIR spectrometry. The results showed that cooling of unirradiated LDPE samples to ?175°C results in a decrease of the intensities of IR bands. However, heating the samples from ?175°C up to +125°C led to a consequence increase in the intensities of the IR bands. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 3461–3469, 2007     

Effects of neutralization on the structure and properties of an ionomer

The structure, morphology, and properties of an ionomer, poly(ethylene‐acrylic‐acid) neutralized by zinc salts (PI) depend on the free carboxylic acid content. In this work, metal acetates (Na, Zn, and Al acetates) were used to control the neutralization levels. A wide range of techniques were used, such as spectroscopic Fourier transform infrared spectroscopy (FTIR), thermal [thermogravimetric analysis, modulated differential scanning calorimetry (MDSC), and dynamic mechanical analysis (DMA)], mechanical (tensile measurement), and small angle neutron scattering (SANS). The melt rheological properties of the samples were also examined. The results show that metal acetate neutralizes free acrylic acid in the ionomer, which has the primary role in controlling ionic association. The number of ionic groups in ionic domains and multiplets in the matrix is dependent on the neutralization level. Metal valence determines the ionic domain or multiplet structure (FTIR), further properties of PI. Dynamic mechanical properties, the ionic transition behaviour, and the mechanical properties are improved compared with PI using monovalent cation (Na⁺), but decreased using trivalent cation (Al³⁺) or shows less significant changes due to steric effects. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Synthesis and ex-situ evaluation of quaternized polysulfone as an anion exchange ionomer for AEM technologies

Anion exchange ionomer (AEI) is a critical component used on anion exchange membrane fuel cell (AEMFC) and alkaline water electrolyzer (AWE). In this work, quaternized polysulfone with different functionalization degree were used as an ionomer to evaluate the performance in the oxygen reduction reaction (ORR) and hydrogen oxidation reaction (HOR), both implied in the operation of AEMFC and AWE. The synthesized ionomer exhibited a better performance in both reactions in comparison to the commercial AEI Aemion®. PSf-130 exhibited better performance, since IEC and surface area increases twice regarding the same parameters in the PSf-60. The PSf-130 conductivity increases three times regarding the value exhibited by PSf-60. Finally, the J_lim and J_k increases 67% and 100% for ORR. On the other hand, the same catalytic parameter increased 44% and 35% for HOR comparing both polysulfone-based ionomers. The Tafel slope values do not showed drastically changes for different ionomers indicating the same rate determining step (RDS) and the same mechanism in both reactions for all the ionomers.     

Thermodynamics of Nafion™-vapor interactions. I. Water vapor

Interaction between water vapor and Nafion™ perfluorosulfonate ionomer has been investigated via combined flow microcalorimetry and isothermal sorption over a wide range of water relative pressure. The molar enthalpy of sorption was determined for the untreated polymer, the residual polymer after extraction by aqueous propanol, and the extracted fraction. The extract appears to be low molecular weight Nafion™ but with an equivalent weight more than double that of the unextracted polymer. The equivalent weight of the residual polymer is slightly lower than that of the original Nafion™, apparently due to partial alkylation. Molar enthalpy for formation of the sulfonic acid monohydrate is about the same for the residual and unextracted polymers, but much greater for the extracted fraction. For untreated Nafion™, the magnitude and concentration dependence of the molar enthalpy indicates that sorption of water exhibits a clear progression from hydronium ion formation (≤1 H₂O/SO₃H) through growth of isolated hydrated clusters (≤6 H₂O/SO₃H) to a continuous internal water phase. A more complicated process occurs for the extract and residual polymer fractions in that an endotherm associated with elastic compression of the polymer matrix surrounding isolated water clusters is superimposed on the hydration exotherm over the concentration range of cluster growth. There is only a minor indication of this endotherm for unextracted Nafion™ because of more facile relaxation of the polymer structure due to plasticization by the low molecular weight fraction.     

Poly(styrene-b-isobutylene-b-styrene) block copolymer ionomers (BCPI) and BCPI/silicate nanocomposites. 2. NaBCPI sol-gel polymerization templates

Polystyrene (PS) blocks in poly(styrene-b-isobutylene-b-styrene) (PS-PIB-PS) block copolymers were partially sulfonated and the acid groups converted to Na⁺SO₃⁻ groups to create ionomers. Then, dimethylacetamide was used to selectively swell the ionic PS domains and the swollen films were exposed to sol-gel reactive tetraethylorthosilicate solutions. (EtO)_4−xSi(OH)_x monomers then permeated films so that sol-gel reactions occurred within/around the ionic PS domains. Environmental scanning electron microscopy/energy dispersive X-ray spectroscopy investigations showed that silicate structures can be incorporated within the interior of the ionomer films. Differential scanning calorimetry studies indicated that there is no variance in the PIB block T_g with respect to ionomer formation, or with respect to silicate loading of the ionomer at low levels, which suggests that the silicate component does not reside in the PIB phase. ²³Na solid state NMR spectroscopy detected isolated Na⁺SO₃⁻ groups as well as aggregated SO₃⁻Na⁺ ion pairs for ‘as cast’ and ‘dry’ non-silicate containing ionomer samples. In a hydrated sample, almost all Na⁺ ions were solvent-separated. AFM analysis showed that phase separation exists, but that the degree of order is significantly less than that for hybrids based on the corresponding benzyltrimethylammonium ionomer. This frustrated morphology was also seen in the results of small angle X-ray scattering experiments. Given the scale of organic/inorganic heterogeneity, these hybrids are properly classified as nanocomposites.     

树脂类催化剂在酯化反应中的应用进展

回顾了近年来离子树脂作为酯化催化剂的发展情况。介绍了聚苯乙烯类树脂和Nafion树脂在各类酯化反应中的应用以及发展,对树脂类催化剂的应用前景以及该类催化剂在绿色化学中的重要作用提出展望。     

丁基橡胶的磺化反应

本工作研究了丁基橡胶的浓度、磺化剂的组成与用量、相转移催化剂、反应温度和时间对丁基橡胶磺化反应的影响。结果表明,增加丁基橡胶的浓度和磺化剂的用量,升高反应温度,丁基橡胶的磺化反应速度加快,延长反应时间能提高产物的磺化度。相转移催化剂c—1则降低磺化反应速度及产物的磺化度。     

Viscoelastic properties and morphology of sulfonated poly(styrene-b-ethylene/butylene-b-styrene) block copolymers (sBCP), and sBCP/[silicate] nanostructured materials

Self-assembled organic/inorganic hybrid materials were created via domain targeted sol-gel reactions of tetraethylorthosilicate in solution with sulfonated poly(styrene-b-[ethylene-co-butylene]-b-styrene) (sSEBS) copolymers. Dynamic mechanical analyses (DMA) of these hybrid materials suggest that the silicate component preferentially incorporates within the sulfonated polystyrene (PS) domains. An irreversible order-order transition (OOT) for unmodified SEBS, sSEBS, and the organic/inorganic hybrids was identified using DMA in shear mode. The OOT temperature increases with sulfonation as well as by adding a silicate phase by the sol-gel process. The DMA results imply a morphological shift with sulfonation, and reflect modified interactions within and between phases. Atomic force microscopy (AFM) indicated a shift from hexagonally packed cylinders in unmodified SEBS to a lamellar morphology in the sulfonated materials, but silicate incorporation did not affect the morphology or domain dimensions. The latter result is evidence for sol-gel polymerization templating in a self-assembly process. The phase-separated morphology is stable up to the degradation temperature of the polymer and thermogravimetric analysis revealed that the degradation temperature is unaffected by silicate incorporation. Small angle X-ray scattering data are in harmony with the structures revealed by AFM in terms of degree of order and scale of features. These results are largely rationalized in terms of chain mobility restrictions due to hydrogen-bonding interactions between different sulfonated PS blocks, an increase in the PS-ethylene/butylene block mixing parameter, increased interfacial surface tension and chain restrictions posed by inserted silicate nanostructures in the case of the hybrid materials.