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Journal of Thermal Analysis and Calorimetry
Authors: Mayté Paredes Zaldivar, Norma Galego Fernández, Cristina Gastón Peña, Manuel Rapado Paneque, and Sonia Altanés Valentín

Introduction Interpenetrating polymer networks (IPNs) are a new class of polymer blends in a network form in which at least one component is polymerized and/or crosslinked in the immediate presence of the other(s) [ 1 – 4

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Abstract  

Positron lifetime measurements were performed to study the swelling dynamics of an amphiphilic polymer network (APN). Lifetime spectroscopy proved to be suitable to investigate APNs. Very quick structural changes were indicated by lifetime parameters at very low swelling ratios. On the basis of the results a possible mechanism is proposed for the hydration of the investigated materials.

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Abstract

The thermal decomposition kinetics of polyurethane/polyethyl acrylate interpenetrating polymer networks (PU/PEA IPN) were studied by means of thermogravimetry and derivative thermogravimetry (TG-DTG), and compared with those of polyurethane (PU) and polyethyl acrylate (PEA). The decomposition temperature (T i) of PU/PEA IPN was found to be higher thanT i of PEA, but lower thanT i of PU. Thermal decomposition kinetic parameters,n andE, estimated using Coats-Redfern method, are found for PU/PEA IPN, PU and PEA to be 1.6, 1.9 and 1.1, and 196.6, 258.6 and 139.2 kJ mol−1, respectively. The results show that PU/PEA IPN is neither a simple mixture of PU and PEA nor a copolymer of them. The mechanism of thermal decomposition of PU/PEA IPN is different from those of PU and PEA. The special network in PU/PEA IPN effectually protects weak bonds in the molecular chain of PU and PEA.

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Summary A series of semi-interpenetrating polymer networks (semi-IPN) of polyurethane (PU) and poly(vinyl chloride) (PVC) has been obtained by prepolymer method and characterised by FTIR; morphological features were examined by SEM-EDS. It has been found that PVC spherical aggregates are dispersed in the PU matrix, but Cl atoms location indicates partial miscibility of both polymers at the interphase which is probably due to hydrogen bonding and/or dipole-dipole interactions. The PVC component influences the phase behaviour of PU’s hard segments, as evidenced by DSC results. Thermogravimetric analysis (TG) reveals a complex, multi-step decomposition process with the main mass loss at 503-693 K, while the DTG maxima are located between 540 and 602 K.

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In this study NMR and DSC are used to probe the structure, thermal characteristics and morphology of a network formed from a diepoxide/acrylate system. Separate chemistries are employed to polymerize the diepoxide and acrylate components. The cationic polymerization of the diepoxide exhibits excellent selectivity in producing a crosslinked polyether network without affecting the acrylate monomer. Subsequent photoinitiated free-radical polymerization of the acrylate produces a phase separated, semi-interpenetrating polymer network (SIPN).

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Abstract  

Interpenetrating polymer network (IPN) hydrogels were prepared by grafting of acrylamide (AAm), N-methylol acrylamide (NMA) and acrylic acid (AAc) onto preirradiated polypropylene (PP) membrane. To obtain PP-g-AAc/AAm/NMA IPN hydrogels, at first, AAc were grafted onto preirradiated PP and then AAm were grafted onto the PP-g-AAc membranes. Finally NMA were grafted onto PP-g-AAc/AAm membranes. In the different stages of grafting under different reaction conditions, trapped radicals in the membrane samples were probed by electron spin resonance (ESR). The temperature response behaviors of the IPN hydrogels were studied. Reversible behavior and controlled release of drug tests made reflecting the switching to on state at higher temperatures and to off state at lower temperatures were achieved. By increasing the grafted content of NMA, higher transition temperature of the hydrogel could be attained.

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Thermal behaviors of POTMDM-net-PMMA and POTMG/PMMA blends were studied by DDSC. Tg of the polymer network was lowered by increasing the POTMDM in feed for copolymerization of POTMDM and MMA. A crystallization peak was observed only when MMA in feed was less than 30%. Tg of POTMG/PMMA was also lowered by decreasing the content of PMMA, however, the change was observed only when PMMA content was more than 70%. These results suggest that thermal transitions of the polymer network are restricted by the mesh size. POTM chains of the polymer network effectively play as a plasticiser.

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Abstract  

The predicted crossover to a fractal-like vibrational regime above 8–10 K was apparently proved by precise measurements of heat capacity of a series of cross-linked heterocyclic polymers.

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Thermal analysis of polymer networks consisting of different homopolymers

Poly(methacrylic acid)-net-poly(oxytetramethylene)

Journal of Thermal Analysis and Calorimetry
Authors: T. Kojima, M. Tsuchiya, and K. Tago

Abstract  

TG and DSC were carried out on PMAA-net-POTM in order to elucidate the relation between the heterogeneity and the thermal changes; moreover, TG and DSC were carried out on PPOTMDM and PMAA to compare the results. The onset temperature in the last stage in the TG curve of PMAA-net-POTM increases as the concentrations of DMF and POTMDM in the polymerization decrease. This is explained in terms of plasticizers effects. A single peak due to fusion of POTM chains appears in the DSC curves of most copolymers. However, it is not seen in the DSC curves of copolymers with high heterogeneity. This is explained in terms of the freezing of POTM chains by frozen heterogeneous moieties.

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Abstract  

The adsorption of uranyl ions from aqueous solutions was studied by using three different measurement techniques. Results obtained by γ-spectrometry, UV-visible spectrophotometry and gravimetry have been compared. It was observed that the results obtained by γ-spectrometric and gravimetric methods were in good agreement and consequently they gave similar deviation error values, whereas the error values for UV-spectrophotometric method were higher than these values. As a conclusion, γ-spectrometric method was found to be more suitable for analysis of uranium in solid and aqueous phases and may be preferred over the UV-spectrophotometric method.

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