No abstract

A series of interpenetrating polymer networks (IPNs) based on carboxylated nitrile rubber (XNBR) and poly(alkyl methacrylate)s such as poly(methyl methacrylate) (PMMA), poly(ethyl methacrylate) (PEMA) and poly(butyl methacrylate) (PBuMA) were synthesized. The compositions of the IPNs were also varied by changing the swelling time of the rubber in the methacrylate monomer. The tensile and dynamic mechanical properties of the IPNs were studied. The dynamic mechanical properties in the range of 1–105 Hz were obtained by the time‐temperature superposition of the data under multifrequency mode, which indicated high tanδ with good storage modulus in the entire frequency range. This indicates the suitability of these IPNs as vibration and acoustic dampers.

Copolymers of styrene and methyl acrylate were synthesized in the form of spherical beads (0.4 -1.2 mm) and sulfonated with concentrated sulfuric acid. The sulfonated copolymer shows an in-built acid-base indicator property; the yellow color in the acid medium changes to an intense pink color at the equivalence point. Also, the ion-exchange capacity of the sulfonated copolymer increases with time, reaches a maximum, and decreases thereafter. The results were explained in terms of Fourier transform infrared spectroscopic analysis considering internal Friedel-Craft acylation followed by cyclic dehydration leading to a conjugated structure. The developed ionexchange resin also demonstrated better performance in demineralization of water as compared with the conventional polystyrene-based beads. MaterialsSt (Fluka) and MA (Fluka) were purified by washing twice with aqueous NaOH solution (5% w/v) to

Sequential interpenetrating polymer networks (IPNs) based on nitrile rubber and poly(methyl methacrylate) (PMMA) were synthesized. IPN compositions were varied by varying the swelling time. Two methods were adopted for making IPNs. The first method is "singlestep IPN" (SIPN) and the second method is "multistep IPN" (MIPN). The compositions were fixed around 90, 80, 70, 60 and 50% of NBR. In SIPN mode, swelling in monomer and subsequent curing was done once. In MIPN mode, swelling in monomer and curing was repeatedly done. Tensile strength of IPNs was found to increase with PMMA content, MIPN showing higher strength compared to SIPN. Dynamic modulus showed a similar trend. The tan ␦ value was found to decrease with PMMA content. At 62/38 nitrile rubber (NBR)/PMMA, MIPN composition isolated tan ␦ peaks appeared near glass transition temperatures of NBR and PMMA, respectively. Scanning electron micrograph showed phase-separated morphology at the same MIPN composition. Solvent resistance increased with IPN formation maintaining higher resistance for MIPN compared to SIPN.

Interpenetrating polymer networks (IPN) are model polymeric systems for vibration damping applications owing to their unique viscoelastic properties. They are characterized by presence of static frozen inhomogeneities at molecular scale and are dynamically heterogeneous at a segmental level. These fundamental and characteristic features of IPNs need to be characterized in order to deduce their structure–macroscopic property correlations. In the present study, we report sequential IPNs prepared from a polyether diamine cross-linked epoxy and triethylene glycol dimethacrylate (TEGDM) cross-linked poly­(methyl methacrylate) (PMMA). Positron annihilation lifetime spectroscopy (PALS) studies revealed a decrease in free volume hole sizes with increased PMMA content in the IPNs, implying interpenetration of polymer chains at a molecular level. Dynamic mechanical analysis measurements were carried out to get insight into the structural relaxations and viscoelastic properties of the IPNs. The IPNs exhibited dissipation factor (tan δ) values >0.3 over a broad temperature (∼10–120 °C) and frequency range (20–20000 Hz), which qualify them as efficient vibration dampers. Stress strain profiles of the IPNs evolved from an elastic to a glassy response with strain-hardening characteristics as the PMMA content was increased in the IPNs. Simultaneous strengthening, stiffening, and toughening of the epoxy matrix were observed with increased PMMA content in the networks. The IPNs were also characterized for liquid water and toluene sorption characteristics to obtain mechanistic insights into the transport properties of the synthesized IPNs. Increasing water uptake and decreasing toluene sorption characteristics were observed with increased PMMA content in the IPNs. The free volume size plausibly governs the water transport properties, while toluene sorption in the IPNs could be influenced by its thermodynamic interaction with the networks. In both cases, non-Fickian sorption kinetics was observed. We posit that the present studies and results provide the basis for designing and characterizing vibration damping networks for practical applications.