Temperature dependence of molecular motions in the polyurethane-based membranes studied with paramagnetic spin probe

Wolińska‐Grabczyk, Aleksandra; Bednarski, Waldemar; Jankowski, Andrzej; Waplak, S.

doi:10.1016/j.polymer.2005.01.052

Cited by 9 publications

(3 citation statements)

References 28 publications

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“…Electron spin resonance (ESR) spectroscopy (spin probe method) has been widely used to obtain information about motional behaviour and relaxation processes in polymers . This technique generally uses paramagnetic species, commonly stable nitroxide radicals, which are dispersed (spin probes) or covalently attached (spin labels) to the polymer matrix.…”

Section: Introductionmentioning

confidence: 99%

Relaxations and chain dynamics of sequential full interpenetrating polymer networks based on natural rubber and poly(methyl methacrylate)

et al. 2013

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The relaxations of natural rubber (NR)/poly(methyl methacrylate) (PMMA) interpenetrating polymer networks (IPNs) were studied using dynamic mechanical analysis, electron spin resonance (ESR) and solid state NMR spectroscopy. Samples with a lower concentration of PMMA in IPNs (25 wt%) showed only one relaxation, which corresponds to NR with a slight shift to higher temperature. IPNs with 35 wt% of PMMA showed very broad transitions arising from βand α-relaxations in PMMA, with the β-relaxation slightly shifted to lower temperature. These compositions also showed a higher modulus at all temperatures. Highly phase separated IPNs showed a complete drop of modulus at 423 K. Higher crosslinking in the NR phase increases the miscibility and decreases the temperature difference between transitions, while in PMMA it increases the phase separation and does not affect the β-relaxation of the PMMA chains. The ESR results showed that PMMA chains located in the PMMA-rich and NR-rich domains have different motional characteristics. The strong interaction between PMMA and NR chains was also observed by carbonyl relaxation in solid state NMR spectra. It was found that medium level crosslinking is needed for better interpenetration between phases. EXPERIMENTAL MaterialsHigh molecular weight NR (M w ≈ 500 000-900 000) was supplied by Rubber Research Institute of India, Kottayam, Kerala. Dicumyl peroxide (99%), the crosslinker for NR, was purchased from Aldrich and used as received. Methyl methacrylate (MMA, Aldrich) and ethylene glycol dimethylacrylate (EGDMA, Aldrich), the crosslinker for MMA, were distilled under vacuum prior to use. Azobisisobutyronitrile (AIBN, Aldrich), the initiator for MMA polymerization, was purified by recrystallization from methanol. Preparation of IPNsSheets of crosslinked NR (1-2 mm thick) were weighed and kept immersed in a homogeneous mixture of MMA, EGDMA and AIBN (0.7 g per 100 g of MMA). The NR sheets were swollen for various time intervals to obtain different weight percentages of PMMA. The swollen samples were kept for a few hours at 273 K to achieve an equilibrium distribution of the MMA monomer in the matrix. These swollen networks were heated at 353 K for 6 h and at 373 K for 2 h in an atmosphere of MMA to complete the polymerization and crosslinking of MMA. Four IPN samples were made with the following ratios of NR and PMMA: 75:25 (NIM 25 ), 65:35 (NIM 35 ), 50:50 (NIM 50 ) and 40:60 (NIM 60 ). Concentrations of crosslinker in weight percentage per 100 g for the NR and PMMA phases are denoted as superscripts before ( x ) and after ( y ) the sample's symbol, respectively. Thus, a general symbol for all the IPN samples is x NIM y z where x stands for wt% of crosslinker for the NR phase, y stands for wt% of crosslinker for the PMMA phase and z stands for wt% of the PMMA phase in the IPN sample. The obtained IPNs were kept in vacuum to eliminate residual unreacted MMA. The composition of the IPN samples was determined on wileyonlinelibrary.com

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Section: Introductionmentioning

confidence: 99%

Relaxations and chain dynamics of sequential full interpenetrating polymer networks based on natural rubber and poly(methyl methacrylate)

et al. 2013

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“…Temperature is a very important operating factor in PV because it can affect the thermal motion of the PDMS polymer chains and the driving force of the separated compounds, thereby altering the flux and separation factor . It is obvious in Figure a that separation factor changes little with the increase of temperature, which can mainly be ascribed to the similar apparent activation energies of methanol and methyl acetate as shown in Figure a,b.…”

Section: Resultsmentioning

confidence: 85%

Pervaporative separation of methyl acetate–methanol azeotropic mixture using high‐performance polydimethylsiloxane/ceramic composite membrane

Zong

Zhou

et al. 2019

Asia-Pacific J Chem Eng

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Methyl acetate is a very important green solvent, which is often produced by esterification using excess methanol as one of the reagents. Therefore, costefficient separation of the methyl acetate/methanol mixture is important. However, the formation of a methanol/methyl acetate azeotrope at atmospheric pressure results in high energy consumption for their separation using distillation such as extractive distillation. In order to reduce the energy consumption, pervaporation (PV) was used to replace the distillation in this study. Two membranes, polydimethylsiloxane and polyoctylmethylsiloxane, were first compared in the PV separation of the methyl acetate/methanol mixture. Then the effects of different operating parameters such as temperature, feed flow rate, permeate pressure, and so on were investigated. Total flux was up to 100 kg/(m 2 ·hr) at 50°C, whereas the separation factor ranges from 1.2 to 5.0.Results showed that the methyl acetate/methanol azeotrope could be broken in the studied concentration range and high flux could be obtained. Furthermore, the change of activation energy with feed methyl acetate concentration and membrane thickness with temperature was investigated. To demonstrate the potential of the industrial applications, the stability in separation of 32 wt.% methyl acetate-methanol mixtures for 15 days was investigated. ORCIDWanqin Jin https://orcid.org/0000-0001-8103-4883 FIGURE 15 Membrane stability in the PV of 32 wt.% methyl acetate-methanol mixture at 25°C FIGURE 14Effects of downstream pressure on separation factor and total flux at 20°C and a fixed flow rate of 1,000 ml/min 10 of 12 LI ET AL.

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“…All PA6-AQS with different reaction temperatures accelerated the decolourization efficiency of AR14 and the optimal reaction temperature was 30 C. The temperature dependence of the molecular motion may be an important factor. [26] When enhancing the temperature, the thermal energy, volume expansion, intermolecular distance and activity space for molecular motion were increased to help the diffusion and reaction of the low molecular reagent. However, the reaction temperature should not be too high, because it may cause an exothermic reaction of the sulphonation process.…”

Section: Optimization Of the Reaction Temperaturementioning

confidence: 99%

Preparation characteristics and accelerating denitrification effectiveness of polyamide 6 modified by AQS

Guo

Niu

et al. 2015

Biotechnology & Biotechnological Equipment

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In this study, the functional polymer biocarrier polyamide 6 (PA6) modified by anthraquinone-2-sulphonate (AQS) was synthesized by hydrolysis and sulphonation reactions. The optimal hydrolysis conditions of PA6 were 35 C, 3 mol/L HCl and 72 h reaction time. The optimal sulphonation conditions of PA6 modified by AQS (PA6-AQS) were 30 C and 6 h reaction time. The morphology and heat resistance of PA6-AQS were analysed by scanning electron microscopy, thermogravimetric analysis and differential scanning calorimetry. The AQS content of PA6-AQS, determined by an elemental analysis, was approximately 0.11 mmol/g. The denitrification efficiency was enhanced by 1.78-fold with PA6-AQS. Repeated-batch operations showed that the denitrification efficiency with PA6-AQS became stabilized above 80% of the original value and exhibited a better catalytic activity and durability.

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Temperature dependence of molecular motions in the polyurethane-based membranes studied with paramagnetic spin probe

Cited by 9 publications

References 28 publications

Relaxations and chain dynamics of sequential full interpenetrating polymer networks based on natural rubber and poly(methyl methacrylate)

Relaxations and chain dynamics of sequential full interpenetrating polymer networks based on natural rubber and poly(methyl methacrylate)

Pervaporative separation of methyl acetate–methanol azeotropic mixture using high‐performance polydimethylsiloxane/ceramic composite membrane

Preparation characteristics and accelerating denitrification effectiveness of polyamide 6 modified by AQS

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