Modification of the mechanical and thermal properties of PVC by semi IPN formation with poly(butyl acrylate)

Semi1 and semi2 interpenetrating polymer networks of poly(vinyl chloride) PVC and in situ formed poly(butyl acrylate) (PBA) have been synthesized and characterized using diallyl phthalate (DAP) and ethylene glycol dimethacrylate (EGDM) as the crosslinkers of PVC and PBA, respectively. These two types of IPNs have been compared with respect to their mechanical and thermal properties. The semi1 IPNs displayed a decrease in their mechanical parameters and the physical properties as well, while in contrast, the semi2 IPNs exhibited a marginal increase in the corresponding values when compared to the crosslinked PVC in the case of semi1 IPN and linear PVC in case of semi2 IPN. The representative samples of semi1 and semi2 IPNs revealed a two‐stage‐degradation typical of PVC while confirming the increased stability of the samples with higher onset temperature of degradation. The softening characteristics as detected by thermomechanical analysis are in conformity with their mechanicals. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Engineering properties of poly(vinyl chloride)–poly(butyl methacrylate) semi‐1 and semi‐2 interpenetrating polymer networks

Semi‐1 and semi‐2 interpenetrating polymer networks (IPNs) of poly(vinyl chloride) (PVC) and in situ formed poly(butyl methacrylate) (PBMA) have been synthesized using diallyl phthalate and ethylene glycol dimethacrylate as the crosslinkers of PVC and PBMA, respectively. These were then characterized with reference to their mechanical, thermal, and morphological properties. The mechanical and thermal characteristics revealed modification over the unmodified polymeric systems in relation to their phase morphologies. The semi‐1 IPNs displayed a decrease in their mechanical parameters of modulus and UTS while semi‐2 IPNs exhibited a marginal increase in these two values. The semi‐1 IPNs, however, also revealed a decrease in the elongation and toughness values away from the normal behavior. The thermomechanical behavior of both the systems is in conformity with their mechanicals in displaying the softening characteristics of the system and stabilization over unmodified PVC. The DSC thermograms are also correlated to these observations along with the heterogeneous phase morphology which is displayed by both the systems especially at higher concentration of PBMA incorporation. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Studies on engineering properties of PVC–PMMA semi‐interpenetrating polymer networks

Semi1 and semi2 interpenetrating polymer networks (IPNs) of PVC and in situ formed PMMA have been synthesized using diallyl phthalate and ethylene glycol dimethacrylate as the crosslinkers of PVC and PMMA, respectively. These two types of IPNs have been compared w.r.t their physical, mechanical, and thermal properties and an endeavor has been made to find a correlation of these properties with the morphology generated in these systems. The semi1 IPNs displayed a decrease in their mechanical parameters and the physical properties as well, while in contrast, the semi2 IPNs exhibited a marginal increase in the corresponding values after an initial drop upto about 15% of crosslinked PMMA incorporation when compared to the crosslinked PVC in the case of semi1 IPN and linear PVC in the case of semi2 IPN. The various samples of semi1 and semi2 IPNs showed a two‐stage degradation typical of PVC, while confirming the increased stability with the samples having higher percentages of PMMA. The influence of crosslinking of the major matrix in semi1 IPN was almost counterbalanced by the influence of crosslinking in the dispersed PMMA phase in the case of semi2 IPN. The softening characteristics as detected by the extent of penetration of the probe, as has been detected by thermomechanical analysis, are in conformity with their mechanicals. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 1725–1735, 2005     

Radiation synthesis and environmental responsiveness of semi‐interpenetrating polymer networks composed of poly(dimethyl–aminoethyl methacrylate) and poly(ethylene oxide)

Semi‐interpenetrating polymer networks (semi‐IPNs) composed of poly(dimethyl–aminoethyl methacrylate) (PDMAEMA) and poly(ethylene oxide) (PEO) were synthesized by γ‐radiation; three semi‐IPNs with 80 : 20, 90 : 10, and 95 : 5 weight ratios of DMAEMA/PEO were obtained by use of this technique. The gel–dose curves showed that the hydrogels were characterized by a structure typical of semi‐IPNs and the results of elemental analysis supported this point. The temperature‐induced phase transition of semi‐IPNs with the composition of 95 : 5 was still retained, with the lower critical solution temperature of PDMAEMA shifting from 40 to 27°C. The temperature sensitivity of the other two semi‐IPNs gradually disappeared. The pH sensitivity of three semi‐IPNs was still retained but the pH shifted slightly to lower values with increasing PEO content in the semi‐IPNs. The effect of PEO content in semi‐IPNs on their environmental responsiveness was discussed. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 2995–3001, 2004     

Curing and mechanical properties of dicyanate/poly(ether sulfone) semi‐interpenetrating polymer networks

Semi‐interpenetrating polymer networks (semi‐IPNs) composed of a dicyanate resin and a poly(ether sulfone) (PES) were prepared, and their curing behavior and mechanical properties were investigated. The curing behavior of the dicyanate/PES semi‐IPN systems catalyzed by an organic metal salt was analyzed. Differential scanning calorimetry was used to study the curing behavior of the semi‐IPN systems. The curing rate of the semi‐IPN systems decreased as the PES content increased. An autocatalytic reaction mechanism was used to analyze the curing reaction of the semi‐IPN systems. The glass‐transition temperature of the semi‐IPNs decreased with increasing PES content. The thermal decomposition behavior of the semi‐IPNs was investigated. The morphology of the semi‐IPNs was investigated with scanning electron microscopy. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 1079–1084, 2003     

Thermal characterizations of semi‐interpenetrating polymer networks composed of poly(ethylene oxide) and poly(N‐isopropylacrylamide)

Poly(N‐isopropylacrylamide) (PNIPAAm)/poly(ethylene oxide) (PEO) semi‐interpenetrating polymer networks (semi‐IPNs) synthesized by radical polymerization of N‐isopropylacrylamide (NIPAAm) in the presence of PEO. The thermal characterizations of the semi‐IPNs were investigated by differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and dielectric analysis (DEA). The melting temperature (T_m) of semi‐IPNs appeared at around 60°C using DSC. DEA was employed to ascertain the glass transition temperature (T_g) and determine the activation energy (E_a) of semi‐IPNs. From the results of DEA, semi‐IPNs exhibited one T_g indicating the presence of phase separation in the semi‐IPN, and T_gs of semi‐IPNs were observed with increasing PNIPAAm content. The thermal decomposition of semi‐IPNa was investigated using TGA and appeared at around 370°C. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 3922–3927, 2003     

Synthesis and characterization of semi‐interpenetrating networks based on poly(dimethylsiloxane) and poly(vinyl alcohol)

Semi‐interpenetrating networks (Semi‐IPNs) with different compositions were prepared from poly(dimethylsiloxane) (PDMS), tetraethylorthosilicate (TEOS), and poly(vinyl alcohol) (PVA) by the sol‐gel process in this study. The characterization of the PDMS/PVA semi‐IPN was carried out using Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), scanning electron microscopy (SEM), and swelling measurements. The presence of PVA domains dispersed in the PDMS network disrupted the network and allowed PDMS to crystallize, as observed by the crystallization and melting peaks in the DSC analyses. Because of the presence of hydrophilic (? OH) and hydrophobic (Si? (CH₃)₂) domains, there was an appropriate hydrophylic/hydrophobic balance in the semi‐IPNs prepared, which led to a maximum equilibrium water content of ～ 14 wt % without a loss in the ability to swell less polar solvents. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Poly[(N‐isopropylacrylamide)‐co‐(itaconic acid)] hydrogels with poly(ethylene glycol)

The aim of the work reported here was to investigate temperature‐ and pH‐sensitive hydrogels of N‐isopropylacrylamide (NIPAM) and itaconic acid (IA) and their semi‐interpenetrating polymer networks (semi‐IPNs) with varying contents of poly(ethylene glycol) (PEG). The stimuli responsiveness, swelling behaviour and mechanical properties of the hydrogels and semi‐IPNs were studied in order to investigate the effect of various amounts of PEG. Pulsed‐gradient spin‐echo NMR experiments were carried out to investigate the diffusion process. The pH sensitivity increased with an increasing amount of PEG in the semi‐IPNs, while the overall rate of water uptake was diffusion‐controlled (n < 0.5). For certain PEG contents (5 and 10 wt%), the semi‐IPNs exhibited better mechanical properties than the poly(NIPAM‐co‐IA) copolymer. The calculated values of the self‐diffusion coefficients of water indicated facilitated diffusion of water through the system with increased amounts of PEG, while the self‐diffusion coefficients of a model compound, metoprolol tartrate, showed no significant dependence on the amount of PEG. According to the results obtained and compared to results reported in the literature, the investigated semi‐IPNs may have potential applications in the controlled release of macromolecular active agents such as proteins and peptides. Copyright © 2009 Society of Chemical Industry     

Semi‐ and full‐interpenetrating polymer networks based on polyurethane produced from canola oil and poly(methyl methacrylate)

Semi‐ and full‐interpenetrating polymer networks (IPNs) were prepared using polyurethane (PUR) produced from a canola oil‐based polyol with primary terminal functional groups and poly(methyl methacrylate) (PMMA). The properties of the material were studied and compared using dynamic mechanical analysis (DMA), differential scanning calorimetry (DSC), and tensile measurements. The morphology of the IPNs was investigated using atomic force microscopy (AFM). Semi‐IPNs demonstrated different thermal mechanical properties, mechanical properties, phase behavior, and morphology from full IPNs. Both types of IPNs studied are two‐phase systems with incomplete phase separation. However, the extent of phase separation is significantly more advanced in the semi‐IPNs compared with the full IPNs. All the semi‐IPNs exhibited higher values of elongation at break for all proportions of acrylate to polyurethane compared with the corresponding full IPNs. These differences are mainly due to the fact that in the case of semi‐IPNs, one of the constituting polymers remains linear, so that it exhibits a loosely packed network and relatively high mobility, whereas in the case of full IPNs, there is a higher degree of crosslinking, which restricts the mobility of the chains. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Modification of novolac resin by interpenetrating network formation with poly(butyl acrylate)

Interpenetrating networks (IPNs) of novolac (phenol formaldehyde) resin and poly(butyl acrylate) (PBA) were prepared by a sequential mode of polymerization. Both full IPNs and semi‐IPNs of different compositions were synthesized and characterized with respect to their mechanical properties, that is, their modulus, ultimate tensile strength (UTS), elongation‐at‐break percentage, and toughness. Their thermal properties were examined with differential scanning calorimetry and thermogravimetric analysis (TGA). A morphological study was performed with an optical microscope. The effects of the variation of the blend ratios on the aforementioned properties were studied. There was a gradual decrease in the modulus and UTS with a simultaneous increase in the elongation‐at‐break percentage and toughness for both types of IPNs as the proportions of PBA were increased. With increasing proportions of PBA, the glass‐transition temperatures of the different IPNs underwent shifts toward a lower temperature region. This showed a plasticizing influence of PBA on the rigid and brittle phenolic matrix. TGA thermograms depicted the classical two‐step degradation for the phenolic resin. Although there was an apparent increase in the thermal stability at the initial stage (up to 350°C), particularly at lower temperatures, a substantial decrease in the thermal stability was observed at higher temperatures under study. In all the micrographs of full IPNs and semi‐IPNs, two‐phase structures were observed, regardless of the PBA content. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 2407–2417, 2005     

Synthesis and characterization of sequential interpenetrating polymer networks of novolac resin and poly(ethyl acrylate)

Interpenetrating polymer networks (IPN) of Novolac/poly(ethyl acrylate) have been prepared via in situ sequential technique of IPN formation. Both full and semi IPNs were characterized with respect to their mechanical properties that is, ultimate tensile strength (UTS), percentage elongation at break, modulus, and toughness. Physical properties of these were evaluated in terms of hardness, specific gravity, and crosslink density. Thermal behavior was studied by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). The morphological features were observed by an optical microscope. There was a gradual decrease in modulus and UTS, with consequent increases in elongation at break and toughness for both types of IPNs with increasing proportions of PEA. An inward shift and lowering (with respect to pure phenolic resin) of the glass transition temperatures of the IPNs with increasing proportions of PEA were observed, thus, indicating a plasticizing influence of PEA on the rigid, brittle, and hard matrix of crosslinked phenolic resin. The TGA thermograms exhibit two‐step degradation patterns. An apparent increase in thermal stability at the initial stages, particularly, at lower temperature regions, was followed by a substantial decrease in thermal stability at the higher temperature region under study. As expected, a gradual decrease in specific gravity and hardness values was observed with increase in PEA incorporation in the IPNs. A steady decrease in crosslink densities with increase in PEA incorporation was quite evident. The surface morphology as revealed by optical microscope clearly indicates two‐phase structures in all the full and semi IPNs, irrespective of acrylic content. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci, 2006     

New interpenetrating polymer networks based on uralkyd–poly(butyl methacrylate)

A study on two‐component semi‐ and full‐interpenetrating polymer networks (IPNs) of soyabean‐oil based uralkyd resin (UA) and poly(butyl methacrylate) (PBMA) synthesized by a sequential technique, has been conducted. The IPNs obtained are characterized with respect to their mechanical properties, such as tensile strength, percentage elongation and hardness (Shore A). Phase morphology has been studied by scanning electron microscopy. Glass transition studies have been carried out using differential scanning calorimetry. The thermal characterization of the IPNs was undertaken with the aid of thermogravimetric analysis. The apparent densities of these samples have been determined and are compared. The effect of the compositional variation on the above‐mentioned properties was examined. The tensile strength exhibits a sudden rise (approximately three‐fold) for the semi‐ and full‐IPNs with composition UA: PBMA 40% : 60% compared with the UA:PBMA composition of 20% : 40%. © 2001 Society of Chemical Industry     

Swelling and diffusion characteristics of novel semi‐interpenetrating network hydrogels composed of poly[(acrylamide)‐ co‐(sodium acrylate)] and poly[(vinylsulfonic acid), sodium salt]

A series of novel semi‐interpenetrating polymer networks (IPNs) composed of poly[(acrylamide)‐co‐(sodium acrylate)] with varying amounts (5, 10, and 15 wt%) of poly[(vinylsulfonic acid), sodium salt] was synthesized. The semi‐IPN hydrogels were characterized by infrared spectroscopy. The swelling behavior of these IPNs was studied in distilled water/physiological solutions/buffer solutions/salt solutions. As the amount of poly[(vinylsulfonic acid), sodium salt] increased in the network, the swelling capacity of the semi‐IPNs increased considerably. The swelling and diffusion characteristics such as water penetration velocity (v), diffusion exponent (n), and diffusion coefficient (D) were calculated in distilled water, as well as in other physiological solutions. The highest swelling capacity was noted in urea and glucose solutions. The semi‐IPN hydrogels followed non‐Fickian diffusion behavior in water and physiological fluids, whereas Fickian behavior was observed in buffer solutions. The stimuli‐responsive characteristics towards physiological fluids, salt concentration, and temperature of these semi‐IPN hydrogels were also investigated. The swelling behavior of the semi‐IPNs decreased markedly with an increase of the concentration of the salt solutions. Copyright © 2006 Society of Chemical Industry     

Thermal and pH dual‐responsive hydrogels based on semi‐interpenetrating network of poly(N‐isopropylacrylamide) and collagen nanofibrils

Hydrogels with environment‐sensitive properties have great potential applications in the controlled drug release field. In this paper, hybrid hydrogels with semi‐interpenetrating polymer networks (semi‐IPNs), composed of poly(N‐isopropylacrylamide) (PNIPAM) as the thermo‐sensitive component by in situ polymerization and self‐assembled collagen nanofibrils as the pH‐sensitive framework, were prepared for controlled release of methyl violet as a model drug. From Fourier transform infrared spectroscopy and scanning electron microscopy, it was indicated that the crosslinking of PNIPAM in the presence of collagen nanofibrils led to the formation of semi‐IPNs with homogeneous porous structure, and the semi‐IPNs showed improved thermal stability and elastic properties compared with the native collagen as determined using differential scanning calorimetry and rheologic measurements. Furthermore, the semi‐IPNs possessed swelling behaviors quite different from those of neat collagen or PNIPAM hydrogel under various pH values and temperatures. Correspondingly, as expected, the drug release behavior in vitro for semi‐IPNs performed variously compared with that for single‐component semi‐IPNs, which revealed the tunable performance of semi‐IPNs for release ability. Finally the thermo‐ and pH‐responsive mechanism of the semi‐IPNs was illuminated to provide guidance for the application of the thermo‐ and pH‐sensitive collagen‐based hybrid hydrogels in controlled drug delivery systems. © 2019 Society of Chemical Industry     

Thermal characteristics of poly(vinyl alcohol) and poly(vinylpyrrolidone) IPNs

Interpenetrating polymer network (IPN) hydrogels based on poly(vinyl alcohol) (PVA) and 1‐vinyl‐2‐pyrrolidone (VP) were prepared by radical polymerization using 2,2‐dimethyl‐2‐phenylacetophenone (DMPAP) and methylene bisacrylicamide (MBAAm) as initiator and crosslinker, respectively. The thermal characterization of the IPNs was investigated by differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and dielectric analysis (DEA). Depressions of the melting temperatures of PVA segments in IPNs were observed with increasing VP content via the DSC. The DEA was employed to ascertain the glass transition temperature (T_g) of IPNs. From the result of DEA, IPNs exhibited two T_gs indicating the presence of phase separation in the IPN. The thermal decomposition of IPNs was investigated using TGA and appeared at near 270°C. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 1844–1847, 2002     

Miscibility and thermal and dynamic mechanical behaviour of semi‐interpenetrating polymer networks based on polyurethane and poly(hydroxyethyl methacrylate)

The thermodynamic miscibility and thermal and dynamic mechanical behaviour of semi‐interpenetrating polymer networks (semi‐IPNs) of crosslinked polyurethane (PU) and linear poly(hydroxyethyl methacrylate) (PHEMA) have been investigated. The free energies of mixing of the semi‐IPN components have been determined by the vapour sorption method and it was established that the parameters are positive and depend on the amount of PHEMA in the semi‐IPN samples. Thermal analyses glass transition temperatures evidenced two in the semi‐IPNs in accordance with the investigation of the thermodynamic miscibility of these systems. Dynamic mechanical analysis revealed a pronounced change in the viscoelastic properties of the PU‐based semi‐IPNs with different amounts of PHEMA in the samples. The semi‐IPNs have two distinct tan δ maxima related to the relaxations of the two polymers in their glass temperature domains. The temperature position of PU relaxation maximum tan δ is invariable but its amplitude decreases in the semi‐IPNs with increasing amount of PHEMA in the systems. The tan δ maximum of PHEMA is shifted to a lower temperature and its amplitude decreases with increasing amount of PU in the semi‐IPNs. The segregation degree of components α was calculated using the viscoelastic properties of semi‐IPNs. It was concluded that the studied semi‐IPNs are two‐phase systems with incomplete phase separation. The different levels of immiscibility lead to the different degree of phase separation in the semi‐IPNs with compositions. Copyright © 2004 Society of Chemical Industry     

Thermal characteristics of interpenetrating polymer networks composed of poly(vinyl alcohol) and poly(N‐isopropylacrylamide)

Interpenetrating polymer networks (IPNs) composed of poly(vinyl alcohol) (PVA) and poly(N‐isopropylacrylamide) (PNIPAAm) were prepared by the sequential‐IPN method. The thermal characterization of the IPNs was investigated using differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and dielectric analysis (DEA). Depression of the melting temperature (T_m) of the PVA segment in IPNs was observed with increasing PNIPAAm content using DSC. DEA was employed to ascertain the glass‐transition temperature (T_g) of IPNs. From the result of DEA, IPNs exhibited two T_g values, indicating the presence of phase separation in the IPNs. The thermal decomposition of IPNs was investigated using TGA and appeared at near 200°C. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 881–885, 2003     

Electrical behavior of chitosan and poly(hydroxyethyl methacrylate) hydrogel in the contact system

Semi‐interpenetrating polymer networks (semi‐IPNs), as polymer hydrogels composed of chitosan and poly(hydroxyethyl methacrylate) (PHEMA), exhibiting electrical‐sensitive behavior, were prepared. The swelling behavior of the chitosan/PHEMA hydrogels was studied by immersing the gels in various concentrations of aqueous NaCl solution. The electrical responses of the semi‐IPN hydrogel, in applied electric fields, were also investigated. When the semi‐IPN hydrogels were swollen, where one electrode was placed in contact with the gel and the other fixed 30 mm apart from one, they exhibited bending behavior on the application of an electric field on a contact system. The electroresponsive behavior of the present semi‐IPN was also affected by the electrolyte concentration of the external solution. The semi‐IPN also showed various degrees of increased bending behavior depending on the electric stimulus. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 915–919, 2004     

Semi‐interpenetrating polymer networks based on polyurethane and poly(vinyl pyrrolidone) obtained by photopolymerization: Structure‐property relationships and bacterial adhesion

A range of semi‐interpenetrating polymer networks (semi‐IPNs) based on polyurethane (PU) and poly(vinyl pyrrolidone) (PVP) have been synthesized and characterized with respect to their thermodynamic characteristics, morphology, mechanical properties, surface properties, water sorption and bacterial adhesion. The free energies of mixing of PU and PVP in semi‐IPNs have been determined by the vapor sorption method and were shown to be positive for all compositions. The surface properties of semi‐IPNs were investigated using the dynamic contact angle analysis. It was shown that the advancing contact angle changes from 83.1° to 65.3° with increasing PVP from 7.05% to 57.38%. Scanning electron microscopy demonstrated that the semi‐IPNs are two‐phase systems with incomplete phase separation. The mechanical properties reflect the changes in structure of semi‐IPNs with increasing of amounts of PVP in the system. Incorporation of PVP into the semi‐IPN with PU restricts the ability of PVP to sorb water. As infection is likely to be caused by bacterial adherence to biomedical implants, the bacterial adhesion data suggests that the semi‐IPNs with PVP content below 22.52% may be useful for biomedical material applications. Polym. Eng. Sci. 44:940–947, 2004. © 2004 Society of Plastics Engineers.     

Phase separation in the polyurethane/poly(2‐hydroxyethyl methacrylate) semi‐interpenetrating polymer networks synthesized by different ways

The thermal, dynamic mechanical analysis, morphology and mechanical properties of semi‐interpenetrating polymer networks based on crosslinked polyurethane (PU) and poly(2‐hydroxyethyl methacrylate) (PHEMA) synthesized by photopolymerization and by thermopolymerization have been investigated. The thermal analysis has evidenced the two glass temperature transitions in the semi‐IPNs and this is confirmed by the thermodynamic miscibility investigation of the systems. The Dynamic Mechanical Analysis spectra have shown that the phase separation is more significant in the thermopolymerized semi‐IPNs: the tan δ peaks of constituent polymers are more distinct and the minimum between the two peaks is deeper. The calculated segregation degree values of semi‐IPN's components are significantly higher for thermopolymerized semi‐IPNs, thereby the process of phase separation in the thermopolymerized semi‐IPNs is more developed. The structures of two series of samples investigated by SEM are completely different. The mechanical properties reflect these changes in structure of semi‐IPNs with increasing amount of PHEMA and with the changing of the method of synthesis. The results suggest that the studied semi‐IPNs are two‐phase systems with incomplete phase separation. The semi‐IPN samples with early stage of phase separation demonstrate higher mechanical characteristics. POLYM. ENG. SCI., 2008. © 2008 Society of Plastics Engineers