Interpenetrating Polymer Network Composites Research Articles

Damping Characteristics of Polyurethane-Based Simultaneous Interpenetrating Polymer Networks

A brief overview of damping with polymers is given. The highest energy absorbing potential of polymers is centred around their glass transition temperature ( T g). In order to broaden the transition, partially miscible polymer pairs with fairly widely separated T gs can be used to give broad and high transition regions. This can be obtained by the use of interpenetrating polymer network (IPN) technology. The damping ability of the IPNs was assessed from the tan δ and loss modulus versus temperature curves. The area under the linear tan δ curve (TA) and the loss modulus equivalent (LA) were calculated and correlated with the IPN composition. An incompatible polyurethane/polystyrene IPN was chemically modified by internetwork grafting and the use of compatibilizers, resulting in a high and broad transition with tan δ values > 0.3 over 80°C and 135°C respectively. Conducting a stirred polymerization of a 60:40 PUR/PS IPN resulted in a very complicated morphology with phases within phases within phases, Values for tan δ were greater than 0.3 from −19°C to 145°C combined with a high TA area of 85.4 K. The influence of the composition on the damping ability was studied in a semicompatible polyurethane/polyethyl methacrylate IPN. At the 70:30 composition, a broad temperature range (> 130°C) of tan δ values greater than 0.3 and a high TA area of 62.1 K resulted. LA was found to increase with increasing PEMA content, but with values well below those expected from applying the linear rule of mixing to LA of the homonetworks. TEM micrographs further elucidated the multiphase morphologies.

Studies on sequential interpenetrating polymer network (IPN) based on nitrile rubber and poly(vinyl acetate)

AbstractSeveral elastomeric sequential interpenetrating polymer networks (IPNs) based on nitrile rubber (NBR) and poly(vinyl acetate) (PVA) have been synthesized. Cross‐linked NBR was swollen in vinyl acetate monomer containing benzoyl peroxide (BPO) as initiator and tetraethylene glycol dimethacrylate (TEGDM) as cross‐linker and then the swollen mass was polymerized. The composition of the IPNs could be varied by varying the swelling time and concentration of BPO and TEGDM. The properties of these IPNs were investigated by tensile test, differential scanning calorimetry (DSC), dynamic mechanical analysis, and swelling measurement. On increasing the PVA content as well as cross‐linking level, the tensile strength increased because of better mixing. DSC showed a single Tg value for all the individual IPNs, the Tg values changing regularly with composition. The tan δ peak for IPNs appeared at higher temperature compared to NBR and was found to be dependent on both the composition of IPNs as well as cross‐linking level. IPNs having 2 and 5% cross‐linker (TEGDM) showed splitting in the tan δ peak. On increasing the cross‐linker concentration to 9% and beyond, the splitting disappeared. The damping capability of the IPNs has been explained in terms of the magnitude of tan δ, area under the tan δ curve, and ½ peak width. The IPNs also showed better solvent‐resistance properties. © 1993 John Wiley & Sons, Inc.

Transition broadening and WLF relationship in polyurethane/poly(methyl methacrylate) interpenetrating polymer networks

A range of simultaneous fully interpenetrating polymer networks (IPNs) based on polyurethane (PU) and poly(methyl methacrylate) (PMMA) were prepared and evaluated using dynamic mechanical analysis. The tests were conducted at resonance frequencies over a wide temperature range. The IPNs produced broad glass transitions, with a unique tan δ peak of rectangular waveform occurring at approximately 70 30 by weight PU/PMMA composition. Tan δ broadening was explained in terms of the patterns of behaviour of the dynamic loss and real moduli during the transition. The type of tan δ broadening was not experienced in PU by crosslinking variation alone. Multiplexed dynamic mechanical runs for the time-temperature superposition were conducted at various frequencies. The Williams-Landel-Ferry (WLF) equation fitted the experimental shift factors over the wide transition regions. The resultant WLF coefficients indicated the presence of larger-than-expected free volumes in the PU-dominated IPN compositions, which, in turn, precipitated glass transitions.

Computer simulation for the pervaporation process of wate/ethanol mixture through interpenetrating polymer network (IPN) membranes

In this study, the pervaporation behavior of EtOH-water mixture through interpenetrating polymer network (IPN) membranes was predicted. The pervaporation characteristics of single component membranes were modelled according to the “six coefficients model” proposed by Brun [J. Membrane Sci., 23 (1985) 257]. In the case of the IPN membrane, two models were proposed according to the phase structure of the IPN. For a uniphase membrane with no phase separation, the compositional averages of the single component membrane coefficients were used. In the case of the phase separated IPN, two cases exist. The first is the island and sea model: one phase is continuous and the other is discrete. The second is the cocontinuous model, in which two continuous phases exist. For these cases the permeation rate and separation factor of the IPN membrane were calculated using the experimental sorption data and pure component values for each IPN composition. Comparison with the experimental data indicates that these models could be to predict the performances of IPN membranes depending on the morphology of the IPN.

Cationic/anionic interpenetrating polymer network membranes for the pervaporation of ethanol-water mixture

The pervaporation of ethanol-water mixtures was examined on cationic/anionic interpenetrating polymer network (IPN) membranes. The cationic polyurethane prepared by quaternizing the tertiary amine from N-methyldiethanolamine and the anionic acrylic copolymer from acrylic acid were used as the cationic and anionic component. The permselectivity of the membrane was investigated with variations in the IPN composition and the ion concentration in the membrane. The separation factor increased as the content of the anionic component in the membrane increased. The ion content in the membrane was also found to be an important factor for the optimum permseparation of water. Better performance was achieved by using PEG-based polyurethane as the cationic component of the IPN membrane. Moreover, the highest selectivity was observed for the IPN membrane with 10 wt.% of PEG-based polyurethane. This result could be explained by high swelling restriction due to the increase in physical crosslinking between networks.

The application of bulk polymerized acrylic and methacrylic interpenetrating polymer networks to noise and vibration damping

AbstractNovel acrylic/methacrylic interpenetrating polymer networks (IPNs) were examined by dynamic mechanical spectroscopy for their damping capabilities. While simple homopolymers exhibit high damping properties only over a 20–30°C range, multicomponent polymer systems with controlled degree of miscibility, such as IPNs, may exhibit high damping properties over temperature ranges as broad as approximately 100°C. Two series of IPNs based on poly(n‐butyl acrylate) and poly(n‐butyl methacrylate) were synthesized and the dynamic mechanical properties were investigated using a Rheovibron. Graphite was incorporated into the poly(n‐butyl acrylate) homopolymer and a few IPNs to measure the change in the damping properties. For important IPN compositions, tan δ values between 0.4 and 0.85 were observed over a 75°C plus temperature range. Graphite increased the damping properties of poly(n‐butyl acrylate) and the IPNs, as indicated by the tan δ values.

Characterization of anionic/cationic sequential IPNs. II. Studies of swelling, modulus, and alternate phase staining with CsF and LiI

AbstractAnionic/cationic interpenetrating polymer networks (IPNs) were synthesized by sequential polymerization from crosslinked polystyrene, PS, as polymer I and crosslinked poly(4‐vinyl pyridine), P(4‐VP), as polymer II. Ionomeric substitution of the two networks was based on sulfonation and quaternization of the phenyl and pyridine rings, respectively. The swelling, morphological, and dynamic mechanical behavior of ionomeric and unsubstituted IPNs was explored as a function of overall IPN composition. A theoretical analysis of the unsubstituted IPNs via the Thiele–Cohen equation showed that essentially no additional physical or chemical crosslinks were developed in the swollen state. Modulus studies showed that network I tends to dominate the mechanical properties in the bulk state. Swelling studies on the ionomeric IPNs as a function of pH demonstrated a complex change in behavior with the addition of NaCl, possibly due to an ionic screening effect. Electron microscopy involved alternate staining of the anionic and cationic phases using CsF and Lil and showed a two‐phase structure, with the possibility of additional phases within phases due to separation of the ionomeric components. Comparison of the two staining techniques yielded strong evidence of a positive/negative–negative/positive phase contrast, depending on the phase being stained. In each case, domains were less than 100 nm (1000 Å), with the domain size decreasing as the P(4‐VP) content increased. Also, a phase inversion appeared to occur between 50 and 80% P(4‐VP). The dynamic mechanical studies supported the two‐phase morphology and gave evidence of significant molecular mixing between the phases.