Mechanical properties of polyurethane-unsaturated polyester interpenetrating polymer networks

Interpenetrating polymer networks (IPNs) based on a polyurethane (PU) and two unsaturated polyester (UPE) resins (a commercially available UPE and a partially endcapped UPE) were prepared. The mechanical properties, such as tensile strength, elongation at break, impact strength, and dynamic mechnical properties of IPNs, were studied by changing reaction temperature, PU reaction rate, and UPE reaction rate. Owing to the unique microgel formaton of UPE, the first formed network tends t be the dispersed phase in the PU-UPE IPN system. The reaction sequence was found to be an important factor in determining the phase mixing and phase morphology of the IPNs. When the PU reaction was faster, extensive phase mixing due to strong grafting or chain interpenetration was obtained. When the UPE reacted first, grafting was retarded by the microgel formation of the UPE network. It was found that simultaneous reaction of the two reacting system resulted in a co-continuous structure that provided enhanced tensile properties and impact strength.     

Synthesis of biodegradable PU/PEGDA IPNs having micro-separated morphology for enhanced blood compatibility

Summary New biodegradable hydrophobic polyurethane (PU)/hydrophilic poly (ethylene glycol) diacrylate (PEGDA) IPN was simultaneously synthesized with changing the molecular weight of PEGDA to investigate the effect of crosslinking density on the degree of phase separation. PU was modified using biodegradable poly(-caprolactone)diol and the hydroxy group of PEG was substituted to crosslinkable acrylate group having double bond, which induce photo-polymerization. The sturucture of PEGDA was confirmed by NMR. Because the reaction rate of PEGDA was faster than that of PU, the continuous matrix of the micro-separated PU/PEGDA IPNs having amphiphilic character was made of hydrophilic PEGDA-rich phase. All IPNs have sea-island morphology resulting from the suppressed phase separation. The effect of the degree of phase separation on blood compatibility was investigated.     

Phase separation of unsaturated polyester resin blended with poly(vinyl acetate)

The behavior of phase separation during the curing reaction of unsaturated polyester (UPE) resin in the presence of low profile additive, that is, poly(vinyl acetate) (PVAc), was studied by low-angle laser light scattering (LALS) and scanning electron microscopy (SEM). The experimental results revealed that the PVAc-rich phase was regularly dispersed in the cured styrene–UPE matrix for styrene–UPE resin blended with 5 wt % of PVAc. As the PVAc content was increased higher than 10 wt %, a cocontinuous PVAc and cured styrene–UPE phase was observed for the cured systems. The LALS observations were carried out in situ at a curing temperature of 100°C; thus, the effect of the rate of exothermic heat released from curing reaction on the morphology of curing system was investigated and reported in this work. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 2413–2428, 1999     

Simultaneous interpenetrating networks of a polyurethane and poly(methyl methacrylate). I. Metastable phase diagrams

Any simultaneous interpenetrating network (SIN) synthesis contains three key events. These are gelation of polymer I, gelation of polymer II, and phase separation of polymer I from polymer II. Metastable phase diagrams of SINs are developed, in which the time occurrence of these three events is represented. A polyurethane/poly(methyl methacrylate) (PU/PMMA) system was chosen as a model. Polymerization kinetics were followed in situ for both PU and PMMA using Fourier Transform Infrared Spectroscopy (FTIR) with the aid of a heated demountable cell. Glass transitions of fully cured samples were determined by dynamic mechanical spectroscopy (DMS) and differential scanning calorimetry (DSC). Phase separation was determined by the onset of turbidity, and gelation of the first gelling polymer was determined by the sudden resistance of the system to flow. As a result, a metastable phase diagram was constructed for the four-component SIN system (the two monomers and their respective polymers) as a tetrahedron in three dimensions with the two monomers and two polymers at the four apexes. Phase separation and gelations of the two polymers are indicated by various surfaces. These surfaces intersect at lines and curves, representing unique conditions of an SIN synthesis, e.g., simultaneous gelation of both polymers, or simultaneous phase separation and gelation of polymer I, etc. These conditions are critical in terms of the development of the SIN morphology, dividing the reaction space into specific regions. Finally, it is shown how the tetrahedron diagram helps visualize the course of the three key events during SIN synthesis, and provides direction for controlling them. © 1995 John Wiley & Sons, Inc.     

聚氨酯／呋喃树脂互穿聚合物网络性能的研究

用糠醇型呋喃树脂或ＨＦ９２００Ａ环氧型呋喃树脂与聚环氧丙烷醚型聚氨酯制备了互穿聚合物网络（ＩＰＮ）。通过红外光谱和扫描电子显微镜分析了聚氨酯（ＰＵ）／呋喃树脂（ＦＡ）ＩＰＮ网络形成的动力学和微相分离行为，并考察了不同配比下ＩＰＮ的力学性能。实验结果表明，ＰＵ／ＦＡ达到某一比值时，产生互穿聚合物网络的协同效应，可改善聚氨酯的刚性，提高呋喃树脂的抗冲击等性能     

互穿聚合物网络技术对丁羟推进剂粘合剂体系性能的改善

通过互穿聚合物网络(IPN)技术,在原有丁羟推进剂粘合剂体系中添加甲基丙烯酸B酯作为塑料相,合成了3个系列的胶片。测定了预聚物的动态黏度,发现改性的预聚物黏度在反应初期明显低于原有预聚物黏度,丙烯酸酯的加入明显改善了其加工工艺性能;对胶片力学性能的测试则表明,拉伸强度可达到1.432 MPa,断裂伸长率达到576.614%。可见,丙烯酸酯对胶片力学性能的改善起到了显著的作用。玻璃化转变温度的测定表征了IPN体系的相分离程度。     

Analysis of unsaturated polyester-polyurethane interpenetrating polymer networks II: Phase separation behavior

The phase separation behavior of unsaturated polyester (UPE)-polyurethane (PU) interpenetrating polymer networks (IPNs) was investigated by light scattering measurements during simultaneous polymerization. The scattered light intensity change with time showed the formation of the dispersed domains, and the average domain correlation length could be calculated from the angle of maximum scattering intensify. It was noted that the dominant phase separation process was spinodal decomposition due to fast reaction. The morphology observed by the transmission electron micrographs for various process conditions showed similar results as obtained from the light scattering experiment.     

Simulation of mass transfer and kinetics during double-network formation using a heterogeneous model

A detailed heterogeneous model considering the thermodynamic incompatibility was developed to simulate polyurethane/poly(methyl methacrylate) (PU/PMMA) interpenetrating polymer network (IPN) formation. The Gibbs free energy was calculated to predict the phase separation point and a two-film theory was used to quantify the mass transfer between the PU-rich phase and the PMMA-rich phase. Compared with the homogeneous model, the cross-linking density of PMMA increases rapidly during the network formation, because the monomer dispersion in two phases improves the possibility of free radical cross-linking reaction, whereas the cross-linking density of PU is unaffected. Simulations show that the partitioning of monomer significantly affects the PMMA network structure. The phase separation is strongly dependent on the onset of MMA polymerization. The proposed model allows visualizing of the IPN formation process and provides direction for reducing the extent of phase separation. Moreover, the structural information derived from the simulations can be further related to the properties.     

IPN中聚氨酯固化反应动力学的FTIR研究

用傅立叶变换红外光谱(FTIR)研究纯聚氨酯弹性体和聚氨酯/聚二甲基硅氧烷IPN中聚氨酯的固化反应动力学。结果表明,在PU/PDMS IPN体系中聚氩酯的交联反应仍为二级反应,聚二甲基硅氧烷的存在大大降低了PU/PDMS IPN的交联速率,并提高了反应活化能。     

双丙酮丙烯酰胺在固体推进剂粘合体系中的应用

用互穿聚合物网络技术(IPN),将双丙酮丙烯酰胺(DAAM)用于PU粘合剂的改性,考察了固化参数、组分比、引发剂用量对PDAAM/PU互穿网络体系力学性能及微观形态的影响。结果表明,PDAAM质量分数为40%,固化参数为1.4,引发剂过氧化苯甲酰(BPO)的质量分数在0.8%~1%时,拉伸强度最高可达1.028 MPa,比相同条件下制备的纯PU的拉伸强度(0.238 MPa)提高了332%;断裂伸长率达到327.35%,比相同条件下制备的纯PU的断裂伸长率(49.02%)提高了568%。组成比、固化催化剂、引发剂用量对PDAAM/PU IPN的微观形态也有影响。PDAAM质量分数较大时,两相界面模糊,互穿较好。三苯基铋(TPB)作为固化催化剂或塑料相的引发剂浓度较低,两相反应速度相近时,相畴较小。     

Hydrophilic/hydrophobic IPN membranes for the pervaporation of ethanol-water mixture

Summary Pervaporation of ethanol-water mixture was examined on IPN membranes composed of hydrophilic polyurethane(PU) and hydrophobia polystyrene(PS). The IPN membranes showed preferential pervaporation of water over ethanol and revealed high permeation rate. As the content of hydrophobic PS was increased, the permeation rate decreased while the separation factor increased, indicating that the PS domains suppressed the swelling of the PU phase and reduced the plasticizing effect. The average diffusion coefficient, computed from the permeation rate and solubility, was highly dependent on the viscosity and concentration of the permeant in the membrane.     

The resin-fiber interface in polyurethane and polyurethane-unsaturated polyester hybrid

A polyurethane (PU) is compared with the polyurethane-unsaturated polyester (PU-UPE) hybrid to examine the changes of the resin-fiber interphase in the presence of a sizing compatible component, UPE, in the matrix resin. The formation of resin-fiber interphase is critical in structural reaction injection molding (SRIM) and resin transfer molding (RTM) because resin solidification (i.e., gelation and vitrification) occurs in seconds (SRIM) or minutes (RTM). Kinetic (DSC, FTIR spectroscopy), mechanical (single fiber test, fracture surface analysis), and microscopic (birefringence, SEM) studies were used to analyze the interface. Kinetic results indicate poor chemical compatibility of the sizing with PU and increased chemical interactions of the sizing with the PU-UPE resin. Mechanical and microscopic analyses also point in favor of improved interphasial behavior with the PU-UPE resin.     

Effect of crosslinking density on the physical properties of interpenetrating polymer networks of polyurethane and 2-hydroxyethyl methacrylate-teminated polyurethane

Interpenetrating polymer networks (IPNs) of 2-hydroxyethyl methacrylate-terminated polyurethane (HPU) and polyurethane (PU) with different crosslinking densities of the PU network were prepared by simultaneous solution polymerization. Dynamic mechanical analysis (DMA) and differential scanning calorimetry (DSC) show that compatibility of component polymers in IPN formation depends on the crosslinking density of the PU network. Physical properties such as density and water absorption rely on the subtle balance between the degree of phase separation and the crosslinking density of the PU network. In spite of the occurrence of phase separation, the tensile moduli and tensile strength of the IPNs increase with the crosslinking density of the PU network. Morphological observation by scanning electron microscopy revealed different fracture surfaces between the compatible and incompatible IPNs. Surface characteristics of the IPNs, indicated as hydrogen bonding index and hard-to-soft segment ratio, are altered considerably by varying surface morphologies. Improved blood compatibility of IPN membranes is due to the variation of the hydrophilic and hydrophobic domain distribution.     

Epoxy/castor oil graft interpenetrating polymer networks

Full-interpenetrating polymer networks (IPNs) were prepared from epoxy and castor oil-based polyurethane (PU), by the sequential mode of synthesis and were characterized by different techniques: swelling test, scanning electron microscopy (SEM), thermomechanical analysis (TMA), thermogravimetric analysis (TGA), tensile test, and instrumented impact test. 2,4-Toluene diisocyanate (TDI) was used as a curing agent for castor oil, at a NO/OH ratio = 1.50. Diglycidyl ether of bisphenol A (DGEBA) was cured and crosslinked using 2,4,6-tris(dimethylaminomethyl)phenol (TDMP) at 1.5%, by weight, of epoxy resin. The homogeneous morphology of IPN samples of PU compositions up to 40%, by weight, revealed by SEM may be attributed to some extent to grafting of the PU phase onto the epoxy matrix, which results from the reaction between NCO groups in the PU phase with OH groups in the epoxy matrix. This has some synergistic effect on the thermal resistance and tensile properties of IPNs compared to those of the pure components, such as illustrated by the data from TGA and tensile tests. However, the grafting structure appears not to enhance their impact resistance, which probably requires the formation of rubbery particles of suitable size. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 70: 1649–1659, 1998     

Method for improving the mechanical performance and thermal stability of unsaturated polyester resin/waste‐printed circuit board nonmetals composites via isocyanate chemistry

To strengthen the interfacial interactions between waste‐printed circuit board (WPCB) nonmetals and unsaturated polyester resin (UPE) and achieve a high performance in UPE composites, a novel type of polyurethane prepolymer (pre‐PU) with dual functions was prepared by the reaction of isophorone diisocyanate with poly(ethylene glycol). We found that pre‐PU was chemically bonded to the surface of the WPCB nonmetals, and a stronger interaction between the WPCB nonmetals and UPE matrix was formed. The mechanical properties and thermal stability of the UPE/pre‐PU–WPCB nonmetal composites showed remarkable improvements compared with those of the UPE/WPCB nonmetals composites, in particular, the impact toughness, which increased threefold. We envision that this promising modification method will not only open up new opportunities for the preparation of high‐performance plastic composites but also provide a guarantee for the practical industrial application of WPCB nonmetals. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45129.     

网络间的化学键效应对聚氨酯／乙烯基酯树脂IPN形态与力学性能的影响

本文通过环氧树脂（Ｅ—５１）与甲基丙烯酸合成了大分子链中含有羟基或羟基被封闭的乙烯基酯树脂（分别称为ＶＥＲＨ与ＶＥＲＡ），并用它们与聚氨酯（ＰＵ）合成了不同组成的ＰＵ／ＶＥＲ互穿网络（ＩＰＮ），用扫描电子显微镜考察了这些ＩＰＮ材料的形态，发现网络间的化学键对ＩＰＮ的形态有很大影响，它们抑制了两个网络间的分相以及ＰＵ硬段局部有序结构的形成。对这些材料的力学性能进行了测定，结果表明网络间的化学键能较大幅度地提高材料的力学性能。     

Controlling the morphology of polyurethane/polystyrene interpenetrating polymer networks for enhanced blood compatibility

Polyurethane (PU)/polystyrene (PS) IPNs were simultaneously synthesized at 80°C, controlling the reaction kinetics to change the morphology. Polymerization kinetics of styrene was controlled by the content of initiator, and that of polyurethane by the catalyst concentration. The effect of the initiator and the catalyst on the polymerization rate was analyzed by NMR spectroscopy and FTIR. Gelation time was also measured by using the advanced rheometric expansion system (ARES). Samples with sea‐and‐island morphology were obtained, when the polymerization rate of PS was relatively slow, and the phase separation time was long. When the polymerization rate of PS was relatively fast, and the phase separation time was short, cocontinuous morphology was obtained. The degree of phase separation and surface roughness decreased, as the rate of PU network formation was increased, and the phase‐continuity was increased. The in vitro blood‐compatibility tests showed that the surface roughness was an important factor on the adsorption of fibrinogens and platelets. A large amount of fibrinogens and platelets were adsorbed on the relatively rough surface of samples showing sea‐island morphology. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 379–387, 2002; DOI 10.1002/app.10358     

Synthesis and characterization of high performance,transparent interpenetrating polymer networks with polyurethane and poly(methyl methacrylate)

Transparent, interpenetrating polymer network (IPN) materials were synthesized using polyurethane (PU) and poly(methyl methacrylate) (PMMA). PMMA contributed to the transparency and rigidity necessary for use in impact‐resistant applications, whereas PU contributed to toughness. Several factors affecting the physical properties, such as the ratio of PU to PMMA, curing profile, inclusion of different isocyanates for the PU phase, and use of an inhibitor in the PMMA phase, were investigated. Full‐IPNs were synthesized so that the two polymer networks would remain entangled with one another, and domain sizes of each system were reduced, mitigating phase separation. Both simultaneous IPNs, polymerization of monomers occurring at the same time, and sequential IPNs, polymerization of monomers occurring at different temperatures, were synthesized for studying the reaction kinetics and final morphologies. The phase morphology and the final thermal and mechanical properties of the IPNs prepared were evaluated. Findings suggest that samples containing ～80 wt% PMMA, 1,6‐diisocyanatohexane 99+% (DCH), and an inhibitor with the MMA monomer created favorable results in the thermo‐mechanical and optical properties. POLYM. ENG. SCI. 2013. © 2012 Society of Plastics Engineers     

Blends of epoxy resins and polyphenylene oxide as processing aids and toughening agents 2: Curing kinetics,rheology, structure and properties

The curing behaviour, chemorheology, morphology and dynamic mechanical properties of epoxy ? polyphenylene oxide (PPO) blends were investigated over a wide range of compositions. Two bisphenol A based di‐epoxides ? pure and oligomeric DGEBA ? were used and their cure with primary, tertiary and quaternary amines was studied. 4,4′‐methylenebis(3‐chloro‐2,6‐diethylaniline) (MCDEA) showed high levels of cure and gave the highest exotherm peak temperature, and so was chosen for blending studies. Similarly pure DGEBA was selected for blending due to its slower reaction rate because of the absence of accelerating hydroxyl groups. For the PPO:DGEBA340/MCDEA system, the reaction rate was reduced with increasing PPO content due to a dilution effect but the heat of reaction were not significantly affected. The rheological behaviour during cure indicated that phase separation occurred prior to gelation, followed by vitrification. The times for phase separation, gelation and vitrification increased with higher PPO levels due to a reduction in the rate of polymerization. Dynamic mechanical thermal analysis of PPO:DGEBA340/MCDEA clearly showed two glass transitions due to the presence of phase separated regions where the lower T_g corresponded to an epoxy‐rich phase and the higher T_g represented the PPO‐rich phase. SEM observations of the cured PPO:DGEBA340/MCDEA blends revealed PPO particles in an epoxy matrix for blends with 10 wt% PPO, co‐continuous morphology for the blend with 30 wt% PPO and epoxy‐rich particles dispersed in a PPO‐rich matrix for 40wt% and more PPO. © 2014 Society of Chemical Industry     

Effect of OMMT on the phase morphology controlling of PU/EP IPN

Organic montmorillonite (OMMT) modified polyurethane (PU) /epoxy resin (EP) (OMMT-PU/EP) graft interpenetrating polymer network nanocomposites with different content of OMMT were prepared. The effect of the OMMT content on the phase behavior of the PU/EP IPN system has been studied by Dynamic mechanical analysis (DMA). With the content of OMMT increased, the tan δ turned from single peak to two peaks and the damping temperature range became wider when the isocyanate index is low. Transmission electron microscope (TEM) and atomic force microscope (AFM) results showed that high content of OMMT favored phase separation to form a larger-size domain in nanocomposites, resulting in the broadening of damping temperature range. This work demonstrates that we can control phase behaviour of OMMT-PU/EP IPNs by changing the OMMT content. This result provides potential opportunity for this type of materials to be used as sound and vibration damping polymers over wide temperature ranges.