Effect of the synthesis route on the structure and properties of polyurethane/nitrokonjac glucomannan semi‐interpenetrating polymer networks

With a synthesis route differing from previous methods, novel semi‐interpenetrating polymer networks (semi‐IPNs), coded UNK‐II, were synthesized by the initial mixing of nitrokonjac glucomannan (NKGM) with castor oil in butanone and the subsequent addition of toluene diisocyanate (TDI) to begin the polymerization reaction in the presence of 1,4‐butanediol (BD) as a chain extender at 60°C. The results from dynamic mechanical analysis, differential scanning calorimetry, and ultraviolet spectroscopy indicated that a certain degree of microphase separation occurred between soft and hard segments of polyurethane (PU) in the UNK‐II sheets. The α‐transition temperature, glass‐transition temperature, heating capacity, and tensile strength increased with an increase in the NKGM content, and this suggested an interaction between PU and NKGM in the UNK‐II sheets. In a previous method, semi‐IPN materials (PUNK) were synthesized by the polymerization reaction between castor oil and TDI, and then this PU prepolymer was mixed with NKGM and cured in the presence of BD as a chain extender. The PUNK sheets had relatively good miscibility and mechanical properties. However, for UNK‐II sheets prepared by the method reported in this work, NKGM mainly played a role in reinforcement. When the NKGM content was less than 10%, the UNK‐II sheets exhibited good miscibility, tensile strength (26–28 MPa), and breaking elongation (130–140%), similar to those of PUNK materials. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 1948–1954, 2003     

Thermal effects in poly(hexamethylene adipamide) and polyoxymethylene at high hydrostatic pressures

The dynamic mechanical properties, transition behavior, and morphology of polycarbonate (PC)-polyurethane (PU) semi-interpenetrating polymer networks (semi-IPNs) and linear blends were studied by means of Rheovibron, differential scanning calorimetry (DSC), and transmission electron microscopy (TEM). Two glass transition temperatures corresponding to polycarbonate and polyurethane were observed and microphase separation was further evident with TEM. In PC/PU semi-IPNs, two glass transition temperatures were shifted inwardly indicating that the interpenetrating network of polyurethane increases the mutual miscibility of PC and PU. The average phase domain was 500Å in semi-IPNs and the phase domains were in the range 1000–6000 Å in linear blends of the corresponding polymers. The compatibilities of PC and PU were greatly influenced by the molecular weight of polyols in PU prepolymer and the ratio of NCO/OH; lower molecular weight polyols and higher NCO/OH ratio resulted in better compatibility, and finer phase domains in PC and PU linear blends and semi-IPNs.     

Properties and interfacial bonding of regenerated cellulose films coated with polyurethane–chitosan IPN coating

Water-resistant films were prepared by coating a castor oil-based polyurethane–chitosan (PU–CH), in which grafted interpenetrating polymer networks (IPNs) were produced, on a regenerated cellulose (RC) film. The tensile strengths of the coated films cured at 90°C for 5 min reached 853 kg cm⁻² (dry state) and 503 kg cm⁻² (wet state) and were obviously higher than those of the films of uncoated and coated with PU coating. Moreover, the coated films have excellent water resistivity, low vapor permeability, and good size stability, and their optical transmittance is even better than that of the RC film in the range of 400–800 nm. The interfacial structure of the coated films was investigated by using spectroscopy infrared, ultraviolet spectroscopy, transmission electron microscopy, and electron probe microanalysis. It was shown that the strong interfacial bonding with chemical and hydrogen bonds between the RC film and the coating exists. The PU prepolymer in the IPN coating penetrated through the interface into the RC film and partly crosslinked with the cellulose, forming a semi-IPNs. The chitosan in the PU–CH coating plays an important role not only in accelerating the cure of the coating but also in improving the mechanical properties and biodegradability of the coated film. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 68: 1313–1319, 1998     

Structure and properties of semiinterpenetrating polymer networks based on polyurethane and nitrochitosan

Two semiinterpenetrating polymer networks (semi‐IPNs) based on trihydroxyl methylpropane–polyurethane (T‐PU) or castor oil–polyurethane (C‐PU) were prepared by curing the mixed solution of the polyurethane prepolymer and nitrochitosan (NCH). During the curing process, crosslinking and grafting reaction between the molecules of the PU prepolymer and NCH occurred, because of the high reactivity of remaining hydroxyl groups in the NCH with ? NCO groups of PU. The structure of the original semi‐IPN sheets and the sheets treated with acetone were studied by infrared, ¹³C‐NMR, scanning electron microscopy, and dynamic mechanical analysis, showing interpenetration of NCH molecules into the PU networks. When nitrochitosan content (C_NCH) was lower than 10 wt %, the semi‐IPN sheets T‐PU and C‐PU had higher density and tensile strength (σ_b) than the systems with C_NCH more than 20%. The trihydroxymethyl propane‐based PU reacted more readily with nitrochitosan to form the semi‐IPNs than castor oil‐based PU. The semi‐IPN coatings T‐PU and C‐PU were used to coat cellophane, resulting in intimate interfacial bonding. The mechanical strength and water resistivity of the cellophane coated with T‐PU coating were improved remarkably. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 3109–3117, 2001     

Effects of nitrolignin on mechanical properties of polyurethane–nitrolignin films

Polyurethane‐nitrolignin (PUNL), a new network polymer, was synthesized from a castor oil based–polyurethane (PU) prepolymer and nitrolignin (NL) with a weight‐average molecular weight of 20.6 × 10⁴ and a content of 1.4–10%. The structure and miscibility of PUNL films prepared by solution casting were investigated by infrared spectroscopy and transmission electron microscopy. The results indicated that PUNL2 film, which had a 2.8% NL content, was the most miscible, and its tensile strength (σ_b) and breaking elongation (?_b) were 2 times higher than that of PU film. The crosslink densities of PUNL films increased with the increase of NL content until about 3%, similar to the variety of the mechanical properties. Thermogravimetric analysis revealed that the thermal stability of PUNL films was slightly higher than that of PU. Covalent bonds occurred between PU prepolymer and the NL in the PUNL films, forming crosslink networks, which resulted in the enhancement of mechanical properties and thermal stability. NL has a far higher reactivity with PU than nitrocellulose. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 1213–1219, 2001     

Properties of crosslinked casein/waterborne polyurethane composites

Waterborne polyurethane (WPU) and casein (1 : 1 by weight) were blended at 90°C for 30 min, and then were crosslinked by adding 1–10 wt % ethanedial to prepare a series of sheets. Their structure and properties were characterized by using infrared spectroscopy, scanning electron microscopy, thermogravimetric analysis, dynamic mechanical analysis, and tensile testing. The results indicated that crosslinked blend sheets exhibited a certain degree of miscibility, and exhibited much higher tensile strength and water resistivity than did the WPU, casein, and the uncrosslinked blend from WPU and casein. When the ethanedial content was 2 wt %, the tensile strength and elongation at break of crosslinked sheets achieved 19.5 MPa and 148% in the dry state, and 5.0 MPa and 175% in the wet state, respectively. A 2 wt % content of ethanedial plays an important role in the enhancement of mechanical properties, thermal stability, and water resistivity of the blends of WPU and casein as a result of intermolecular crosslinking. This work provided a new protein plastic with good water resistivity. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 332–338, 2004     

Miscibility and properties of semi‐interpenetrating polymer networks based on polyurethane and nitroguar gum

Films from castor oil‐based polyurethane (PU) prepolymer and nitroguar gum (NGG) with different contents (10–70 wt %) were prepared through solution casting method. The networks of PU crosslinked with 1,4‐butanediol were interpenetrated by linear NGG to form semi‐interpenetrating polymer networks (semi‐IPNs) in the blend films. The miscibility, morphology, and properties of the semi‐IPNs coded as PUNG films were investigated with Fourier transform infrared spectroscopy, scanning electron microscopy, differential scanning calorimetry, dynamic mechanical thermal analysis, wide‐angle X‐ray diffraction, density measurement, ultraviolet spectroscopy, thermogravimetric analysis, tensile, and solvent‐resistance testing. The results revealed that the semi‐IPNs films have good miscibility over the entire composition ratio of PU to NGG under study. The occurrence of hydrogen‐bonding interaction between PU and NGG played a key role in improvement of the material performance. Compared with the pure PU film, the PUNG films exhibited higher values of tensile strength (11.7–28.4 MPa). Meanwhile, incorporating NGG into the PU networks led to an improvement of thermal stability and better solvent‐resistance of the resulting materials. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104, 4068–4079, 2007     

Semi-IPNs formed from poly(ethylene glycol monomethyl ether acrylate) and an epoxy thermoset

Poly(ethylene glycol monomethyl ether acrylate) (PEGMEA) was synthesized from the reaction of poly(ethylene glycol monomethyl ether) (PEGME) with acryloyl chloride. Semi-IPNs based on various weight ratios of diglycidyl ether of bisphenol A (DGEBA)/PEGMEA were prepared, using isophronediamine (IPDA) and 2,2′-azo-bis(isobutyronitrile) (AIBN) as curing agents. The glass transition temperature and exothermic peak shifts were studied with differential scanning calorimetry (DSC). Viscosity changes during semi-IPN formation were measured with a Brookfield viscometer. Dynamic mechanical properties were investigated by rheometric dynamic spectroscopy (RDS). Stress–strain curves were obtained with an Instron tensile tester, while impact resistance was measured with a computer aided falling dart impact tester. Experimental results revealed retarded curing rates for all semi-IPNs, as evidenced from the shifts of curing exothermic peaks to higher temperatures, together with retarded viscosity increases during semi-IPN formation. These phenomena were interpreted in terms of chain entanglement between epoxy and PEGMEA. Nevertheless, the semi-IPNs indicated good compatibility as inferred from a single T_g in DSC and a single damping peak in RDS for each semi-IPN. Improved tensile stress and strain along with toughness improvements were noticed for this semi-IPN system. Shear band yielding was proposed to interpret this result. © 1999 Society of Chemical Industry     

Dynamic mechanical study of filled semi-interpenetrating polymer networks: Influence of γ-Fe2O3 on microphase structure

The preparation of filled two-component semi-interpenetrating polymer networks (semi-IPNs) is described and the results of an investigation of their morphology by means of dynamic mechanical spectroscopy are considered. The influence of an active dispersed filler (γ-Fe₂O₃) on the semi-IPNs phase structure is studied. A comparison is made between filled and unfilled semi-IPNs consisting of compatible or incompatible polymers. In the case of a semi-IPN of compatible polymers, the introduction of γ-Fe₂O₃ was observed to cause phase separation. With a two-phase semi-IPN the introduction of the filler enhanced the phase separation. The presence of two distinct peaks (the dynamic glass transition temperatures) corresponding to those of the two initial homopolymers shows the semi-IPN to have a two-phase structure.     

Morphology and mechanical properties of semi-interpenetrating polymer networks from polyurethane and benzyl konjac glucomannan

A series of semi-interpenetrating polymer network (semi-IPN) films coded as UB from castor oil-based polyurethane (PU) and benzyl konjac glucomannan (B-KGM) were prepared, and they have good or certain miscibility over entire composition range. Morphology, miscibility and properties of the UB films were investigated by using scanning electron microscopy (SEM), differential scanning calorimetry, dynamic mechanical analysis, ultraviolet spectrometer, wide-angle X-ray diffraction and tensile test. The results indicated that the UB films exhibited good miscibility when B-KGM content was lower than 15 wt%, resulting in relatively high light transmittance, breaking elongation and density. With an increase of the B-KGM content from 20 to 80 wt%, a certain degree of phase separation between PU and B-KGM occurred in the UB films. The tensile strength of the films UB increased from 7 to 45 MPa with an increase of B-KGM content from 0 to 80 wt%. By extracting the B-KGM with N, N-dimethylformamide from the semi-IPN, the morphology and phase domain size of the UB films were clearly observed by SEM. A continuous phase and dual-continuous phase model describing the semi-IPN were proposed to illustrate the morphology and its transition.     

Graft copolymerization of PU membranes with acrylic acid and crotonic acid using benzoyl peroxide initiator

To improve water wettability of polyurethane (PU), graft copolymerization with acrylic acid (AA) and crotonic acid (CA) was performed using a benzoyl peroxide (BO) initiator. The grafting reaction was carried out by placing the membranes in aqueous solutions of AA and CA at constant temperatures. Variations of graft yield with time, temperature, initiator, and monomer concentrations were investigated. The optimum temperature, polymerization time, monomer, and initiator concentrations for AA were found to be 70°C; 3 h; 1.5 M; 5.0 × 10^?2 M, and for CA 70°C; 1 h; 1.5 M; 4.0 × 10^?2 M, respectively. The grafting membranes were characterized by FTIR spectroscopy and scanning electron microscopy (SEM) analysis, and the effect of grafting on equilibrium water content (EWC) of PU membranes was obtained by swelling measurements. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 2690–2695, 2001     

Cellulose/casein blend membranes from NaOH/urea solution

Cellulose membranes and cellulose/casein blend membranes were successfully prepared from a new solvent system (6 wt % NaOH/4 wt % urea aqueous solution) by coagulation with a sulfuric acid aqueous solution. The structures and properties of the membranes were characterized by Fourier transform infrared spectroscopy, scanning electron microscopy (SEM), wide-angle X-ray diffraction, differential scanning calorimetry, and a tensile test. The experimental results showed that the suitable coagulation condition was 5 wt % H₂SO₄ for 5 min. When the casein content of the mixture was less than 15 wt %, the blend membranes were miscible because of the interactions between the hydroxyl groups of cellulose and the peptide bonds of casein. The blend membranes with 10 wt % casein had good miscibility, higher crystallinity, and the highest mechanical properties and thermal stability. In this case, the tensile strength and breaking elongation of the blend membranes were 109 MPa and 16%, respectively, and its pore size, obtained by SEM, was 290 nm, which suggests that the blend membranes provide a potential application for the field of separation technology. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 3260–3267, 2001     

Study of a compatibilized ultra-high-molecular-weight polyethylene and polyurethane blend

Ultra-high-molecular-weight polyethylene (UHMWPE) and thermoplastic polyester-type polyurethane (PU) were blended with polyethylene-grafted maleic anhydride (PE-g-MAH) added as a compatibilizer. A dual roller was used as a mixer, and all specimens were produced by the compression molding method. It was found that without compatibilizer, UHMWPE and PU were immiscible polymers and mixing PE-g-MAH reduced the size of the dispersed PU domains by a factor of 10 to reach 0.5–5 μm and caused a more uniform distribution of the PU phase in the UHMWPE matrix. Also, PE-g-MAH influenced the crystallinity of UHMWPE, increased the amorphous region in the UHMWPE phase, and improved interfacial adhesion. The threshold concentration of compatibilizer was 10 wt %, and the compatibilized UHMWPE/PU composites had improved mechanical properties and lower wear rate than the uncompatibilized composite. At some ratio points, compatibilizer composites even had better wear-resistance properties than pure UHMWPE. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 3290–3295, 2001     

Investigation of the preparation and physical properties of a novel semi-interpenetrating polymer network based on epoxised NR and PVA using maleic acid as the crosslinking agent

Natural rubber (NR) and its derivatives as renewable and biodegradable materials have attracted considerable attention because of the serious pollution problems caused by synthetic materials and a shortage of resources. A new semi-interpenetrating polymer network (semi-IPN) based on epoxidised natural rubber and polyvinyl alcohol containing maleic acid as a crosslinking reagent was synthesized and characterized by FTIR, XRD, SEM, swelling ratio in both distilled water and toluene, and mechanical properties. The curing time and dose of maleic acid were varied from 10 to 60 min, and from 10 to 60% (w/w), respectively. An IR spectroscopic study indicated the presence of an ester linkage at 1730 cm⁻¹ in maleic acid crosslinked with PVA in semi-IPN films. In addition, the crystalline content of PVA dramatically decreased after adding maleic acid in the semi-IPN, as observed from its XRD. The semi-IPNs exhibit good mechanical properties, thermal stability, characteristics of a polyvinyl alcohol–maleic acid polymer network. An SEM of the semi-IPNs containing maleic acid showed no phase separation, when compared with the sample prepared in the absence of maleic acid.     

Graft polymerization of methyl methacrylate onto guar gum with ceric ammonium sulfate/dextrose redox pair

The effect of different reaction conditions on the grafting of methyl methacrylate (MMA) onto guar gum (GG) has been studied in detail. The grafting efficiency was optimal under the following conditions: MMA at 1.13 mol/L; ceric ammonium sulfate at 6.32 × 10^?3 mol/L; dextrose monohydrate at 2.428 × 10^?3 mol/L; GG at 4 g/L; temperature at 50°C; and time at 210 min. Fourier transform infrared spectroscopy was used for the confirmation of copolymer formation. Thermogravimetric analysis of GG and a representative graft copolymer were studied. A probable mechanism of grafting has been suggested. The biodegradability of the resulted copolymer was evaluated. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 3520–3525, 2001     

Synthesis and physicochemical study of bisphenol‐C‐formaldehyde‐toluene diisocyanate polyurethane–jute and jute–rice husk/wheat husk composites

Bisphenol‐C‐formaldehyde‐toluene‐2,4‐di isocyanate polyurethane (PU) has been synthesized at room temperature and used for the fabrication of jute and jute–rice husk/wheat husk hybrid composites. PU–jute and PU–jute–RH/WH composites were prepared under pressure of 30.4 MPa at room temperature for 8 h, while PU–jute–RH/WH composites were prepared under same pressure at 110°C for 5 h. PU–jute composite has good tensile strength and flexural strength (50–53 MPa), while PU–jute–RH/WH hybrid composites have moderate tensile strength (9–11 MPa) and a fairly good flexural strength (15–31 MPa). Composites possess 1.1–2.2 kV electric strength and 0.94–1.26 × 10¹² ohm cm volume resistivity. Water absorption in PU–jute composite is different in water (9.75%), 10% HCl (12.14%), and 10% NaCl (6.05%). Equilibrium water uptake time in salt environment is observed 96 h, while in pure water and acidic environments it is 192 h. In boiling water equilibrium water content and equilibrium time are found to be 21.7% and 3 h, respectively. Water absorption increased 2.2 times in boiling water, whereas equilibrium time reduced 64 times. Thus, PU–jute composite has excellent hydrolytic stability against boiling water, 10% HCl, and 10% NaCl solutions. Fairly good mechanical and electrical properties and excellent hydrolytic stability of composites signify their usefulness for low cost housing units and in electrical and marine industries. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 2363–2370, 2006     

Miscibility and specific interactions in blends of poly(vinyl phenyl ketone hydrogenated) with poly(2,6‐dimethyl‐1,4‐phenylene oxide)

The miscibility behavior of poly(vinyl phenyl ketone hydrogenated) (PVPhKH) and poly(2,6‐dimethyl‐1,4‐phenylene oxide) (PPO) are studied by differential scanning calorimetry, thermomechanical analysis, and FTIR spectroscopy. Two miscibility windows between 10 to 40 and 60 to 90 wt % PPO are detected. Only the blend with 50 wt % PPO is immiscible. The best fit of the Gordon–Taylor equation of the experimental glass‐transition temperatures for miscible PVPhKH/PPO blends is shown. A study by FTIR spectroscopy suggests that hydrogen bonding interactions are formed between the hydroxyl groups of PVPhKH and the ether groups of PPO. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 1887–1892, 2004     

Synthesis and processing of PMR-15/LaRC-TPI semi-IPN systems

To improve the fracture toughness of PMR-15 polyimide and to alleviate its high susceptibility to microcracking induced by thermal cycling, a thermoplastic polyimide, LARC-TPI, was incorporated to form a sequential semi-interpenetrating polymer network (semi-2 IPN). The imidization kinetics of LARC-TPI in the semi-IPNs were studied using a thermal gravimetric analyzer. Both the solvent and the glass transition temperature of the semi-IPN were found to have significant effects on the imidization kinetics. The kinetics could be modeled by a two-step reaction: the first step being a second-order reaction followed by a second step, which is a first-order diffusion-controlled reaction. Differential scanning calorimetry was chosen to investigate the curing of PMR-15 and PMR-15/LARC-TPI semi-IPNs. The curing process was well correlated by a first-order reaction kinetics, which suggested that the reverse Diels-Alder reaction of the Norbornene end group was the rate controlling step. The glass transition temperatures of these semi-IPNs were again found to play important an important role in dictating the curing kinetics. A higher proportion of LARC-TPI or a higher glass transition temperature of the semi-IPN prepolymer tended to result in a slower curing reaction. The optimum molding cycle of PMR-15 and PMR-15/LARC-TPI semi-IPNs were then determined from the obtained kinetics. © 1995 John Wiley & Sons, Inc.     

Preparation and properties of polyurethane/benzyl amylose semi‐interpenetrating networks

A series of semi‐interpenetrating polymer networks (semi‐IPNs) films were prepared from 20 wt % of benzyl amylose (BA) of different M_w and castor oil‐based polyurethane (PU) in N,N‐dimethylformamide (DMF). The weight‐average molecular weight (M_w), and radii of gyration (<S²>_z^1/2) of benzyl amylose were determined by laser scattering measurement, and the results suggested BA was in a compact coil conformation in DMF. Furthermore, the properties and miscibility of the polyurethane/benzyl amylose (PUBA) films were studied by scanning electronic microscopy, differential scanning calorimetry, dynamic mechanical thermal analysis, ultraviolet–visible spectrophotometer, and tensile testing. The PUBA films possessed much higher optical transmittance and tensile strength than the pure PU film regardless of the molecular weight of BA, but lower values of elongation at break were observed. With decreasing of the BA M_w from 9.24 × 10⁵ to 2.69 × 10⁵, interestingly, the elongation at break of the films increased from 135 to 326%. This might be ascribed to the decrease of crosslinking density of PU networks and the enhancement in freedom of the molecular motion. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Shape memory polymer system of semi-interpenetrating network structure composed of crosslinked poly (methyl methacrylate) and poly (ethylene oxide)

Shape memory semi-interpenetrating polymer networks (semi-IPNs) composed of crystalline poly (ethylene oxide) (PEO) and crosslinked poly (methyl methacrylate) (x-PMMA) have been investigated. The selected compositions show shape memory property with a reasonable fast recovery (recovery time ∼1 min) and shape recovery ratio of 99%. Effects of composition (x-PMMA/PEO = 80/20…60/40) and crosslinker (triethyleneglycol dimethacrylate) concentration (up to 6 wt.%) on the creep property were also studied. The recovery time of the semi-IPNs increased and the creep compliance decreased with increasing crosslinker concentration. The network structure containing PEO crystal was characterized by scanning electron microscopy (SEM). Differential scanning calorimetry (DSC) indicated that the PEO, present confined in the semi-IPN, melts at a lower temperature compared to the pure PEO. Dynamic mechanical analysis (DMA) showed a decrease in the glass transition (T_g) of the semi-IPN due to the phase mixing of amorphous PEO and PMMA. Both the glassy and rubbery moduli (E_g and E_r, respectively) were lower for the semi-IPNs than for the x-PMMA network. On the other hand, the E_g/E_r ratio was markedly increased for the semi-IPNs supporting an easy shaping along with a good shape fixing.