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。     

纳米PANI-DBSA/EA/PU互穿网络导电膜的制备及其性能

用原位乳液聚合法在环氧丙烯酸树脂(EA)中合成了十二烷基苯磺酸掺杂的纳米聚苯胺(PNAI-DBSA),纳米PNAI-DBSA/EA混合物与蓖麻油聚氨酯(PU)预聚体、交联剂(苯乙烯、丙烯腈)等混合后,在引发剂过氧化苯甲酰(BPO)的作用下形成了纳米PANI-DBSA/EA/PU互穿网络导电复合膜。通过测定电导率和拉伸强度,研究了PANI-DBSA含量、交联剂及偶联剂的种类和用量以及BPO用量对复合膜导电和力学性能的影响。结果表明:在PANI-DBSA含量为12.5%、苯乙烯含量为60%、KH-550用量为3%、BPO用量为0.4%时,复合膜的电导率达2×10 ^-5 S/m,拉伸强度为15.8 MPa。     

Kinetics of formation of polyurethane/polymethylmethacrylate grafted semi-interpenetrating polymer networks based on the functional prepolymers

Summary. The kinetics of formation of the polyurethane network by crosslinking the polyurethane prepolymer in polyurethane/polymethacrylate grafted semi-interpenetrating networks (semi-IPN) was monitored by Fourier transform infrared spectroscopy, and the kinetic parameters were thus determined. It was found that carboxylic groups in the hard segments of the Pu component substantially decrease the reaction rate and increase the activation energy. Tertiary amine groups in the PM component catalyse the crosslinking reaction. The PM component acts as a diluent in the mixture of PU and PM reducing the reaction rate and increasing the activation energy of the corsslinking reaction. At temperatures below the T_g of the PM component, the reaction of formation of IPN becomes diffusion controlled. Received: 2 May 1997/Revised: 11 July 1997/Accepted: 16 July 1997     

Permeation of oxygen through polyurethane–polyepoxide interpenetrating polymer networks

Oxygen permeation studies on polyurethane (PU)/polyepoxide (EP) interpenetrating polymer networks show that the increased crosslinking density owing to additional permanent chain entanglement (resulting from interpenetration) can decrease the coefficients of permeation, diffusion, and oxygen solubility. At 20% PU, at which the crosslinking density is maximum, these coefficients retain minimum values, while the tensile strength retains a maximum value.     

A new tri‐functional azetidine compound for self‐curing aqueous‐based PU system

A mono‐azetidine compound had been demonstrating a ring opening reaction with carboxylic acid (e.g., trimethylacetic acid, TMAA) and that resulted in an amino ester bond formation at ambient temperature. A triazetidine compound (trimethylolpropane tris(1‐azetidinyl)propionate, TMPTA‐AZT) was obtained via Michael addition of azetidine (AZT) to trimethylolpropane triacrylate (TMPTA). The carboxylic groups of anionic aqueous‐based polyurethanes (PU) served as internal emulsifier, which stabilized PU dispersion and also served as PU curing sites. The triazetidine compound (TMPTA‐AZT) was introduced into anionic aqueous‐based PU dispersion as a new latent curing agent and that mixture became a single‐component self‐curable aqueous PU system. A crosslinked PU film was obtained from this PU system on drying at ambient temperature. The final polymer performance properties demonstrated the crosslinking behaviors of this new curing agent, TMPTA‐AZT, with carboxylic ion‐containing aqueous‐based PU resins. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

The effects of functional azo initiator on PMMA and polyurethane IPN systems. I. Synthesis,characterization, and thermal effects

The use of functional azo initiators and the thermal history of the materials have been shown to exert significant effects on the properties of interpenetrating polymer networks (IPNs). The IPNs prepared with a reactive azo initiator from MDI and 1,2-PBD (1,2-polybutadiene diol) with PMMA have been found to exhibit greater ductility, lower rigidity, and lower moduli than IPNs prepared with AIBN. This probably resulted from the attached PMMA blocks modifying the properties of the PU matrix phases. Increasing thermal treatment of IPNs prepared from either the reactive or the normal azo initiators exhibited increased T_g values in both DSC and DMTA scans. These results have been explained by increased association from chemical reactions between the hard segments of the polyurethane and poly(methyl methacrylate) ester groups.     

HTPB/液化MDI型PU与PMMA的共混研究

用同步聚合法制备了一系列HTPB／液化MDI型PU与PMMA的共混材料，分别用FTIR、DSC、SEM和拉力实验机对共混材料的反应进度、玻璃化转变温度、力学性能和微观形态进行了考查和研究；结果表明，体系中PMMA优先于PU聚合，共混材料的玻璃化转变温度Tg2随PMMA质量分数的增加略呈上升趋势；材料的拉伸强度和硬度均随体系中PMMA质量分数的增加而增大，断裂伸长率则逐渐减小；体系微观呈两相分离，当PMMA占50％时，相畴最小。     

Rheological study of the gelation of cross-linking polyhedral oligomeric silsesquioxanes (POSS)/PU composites

The gelation process of N-Phenylaminomethyl-POSS/PU (polyurethane) nanocomposites during curing and at the stable state after curing was investigated by rheology. An increase in dynamic shear moduli, G′ and G″, was observed during the dynamic temperature ramps of the sample. In time-resolved mechanical spectroscopy (TRMS), G′ and G″ increased with curing time at constant curing temperatures over a wide of frequencies. The gelation time of the composites decreased with the rise of curing temperature or with the increase of POSS concentration. The relaxation exponent n at the critical gel was around 0.73. The gel stiffness S decreased as curing temperature increased or as POSS concentration increased. After the completion of the curing reaction, the critical concentration of POSS beyond which the gelation of POSS/PU composites would happen was found around 2.5 wt%. The viscoelastic properties of crosslinking POSS/PU fitted time–temperature-superposition well which implied the incorporation of multifunctional POSS into PU increased the homogeneity of crosslinking POSS/PU composites. Surprisingly, the modulus of the fully cured materials between 2.7 wt% and 6 wt% could also be supposed onto a master curve at high temperature, which implied self-similarity of network near the critical gel. The similar microstructure of POSS/PU at stable state was also confirmed by TEM. The network formation mechanism and the fine structure of the crosslinking POSS/PU were firstly investigated which would provide technical and theoretical basis for other hybrid crosslinking systems.     

Polyurethane-crosslinked epoxy resins. II. Compatibility and morphology

The polyurethane(PU)-crosslinked diglycidyl ether of bisphenol A (DGEBA) was prepared from the reaction of the pendent secondary hydroxy group in DGEBA with the isocyanate-terminated group present in the PU prepolymer. Though the PU acted as a crosslinking agent for the DGEBA, the morphology and dynamic mechanical behaviour of these PU-crosslinked DGEBA could be different among themselves depending on the type and molecular weight of polyols employed in the PU. There was no significant shift in the loss modulus (E″) peaks of the DGEBA crosslinked with the polyester-type and polyether-type polyurethanes, but the intensity of the E″ peaks increased as the polyester-type PU employed. The morphology of this polyester-type PU-crosslinked DGEBA exhibited a homogeneous one-phase system, while the DGEBA crosslinked with the polyether-type PU showed a two-phase morphology with the PU particles dispersed in DGEBA matrix.     

Effect of CePO<Subscript>4</Subscript> nanostructures in transparent PMMA/castor-oil based PU IPNs on thermal stability,optical and mechanical properties

Interpenetrating polymer networks (IPNs) based on PMMA/castor-oil based PU/cerium phosphate nanoparticles (CePO₄) constitute an important type of materials to modulate the stiffness and confers ductile behavior to PMMA. A comparison of CePO₄ dispersion into different ratios of PMMA/PU IPNs between sonication method and the classic magnetic stirring during the sequential polymerization synthesis was done through structural, optical, thermal, morphological and mechanical analysis. The results demonstrated that sonication is the adequate method to disperse CePO₄ in low viscous systems such as PMMA/PU 70/30 and 60/40 wt.%, while magnetic stirring favors the dispersion in high viscous systems (PMMA/PU 50/50 wt.%). Thanks to the physical interaction, the good compatibility/miscibility between PMMA/PU and CePO₄ is reached. The obtained experimental results indicated that the luminescent CePO₄ nanoparticles, in addition to improve the structural properties and the Young’s modulus, can reduce voids in the networks.     

Water vapor‐permeable polyurethane ionomer

The reaction of toluene diisocyanate with 2,2,3,3‐tetrafluoro‐1‐propanol (fluoro compound) or 3‐glycidoxypropyl trimethoxysilane(siloxane compound) and other additives to form the structure of the fluoro‐based or siloxane‐based polyurethane (PU) ionomer has been proven by infrared spectra. Experimental results indicated that the amount of water vapor permeability of the film made by fluoro‐based or siloxane‐based PU ionomer appeared to gradually increase with increasing concentration of the siloxane compound or fluoro compound, as a result of the formation of more porosities. Our experimental results also showed that the water vapor absorption was seen to be larger for the film made by siloxane‐based PU ionomer film than for the film made by fluoro‐based PU ionomer film, as a result of increased hydrophilic groups attached to the backbone of the PU ionomer molecule. For the film prepared by siloxane‐based PU ionomer, both tensile strength and elongation appeared to increase with an increase in the concentration of siloxane compound. This may be the result of the intermolecular interaction between siloxane‐based PU ionomer molecules themselves, thus enhancing the crosslinking capability of the ionomer molecules. On the other hand, both tensile strength and elongation for the film prepared by fluoro‐based PU ionomer decreased with increasing concentration of the fluoro compound, as a result of intramolecular interaction greatly reducing the crosslinking capability of the ionomer molecules. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 3767–3773, 2006     

Polyurethane–poly(methyl methacrylate) interpenetrating polymer networks. I. Synthesis,characterization, and preliminary blood compatibility studies

Simultaneous polyurethane–poly(methyl methacrylate) (PU–PMMA) interpenetrating polymer networks (IPNs) were synthesized with the PMMA polymerization initiated at room temperature. Transparent IPNs with better miscibility and synergism of mechanical properties were obtained. Dynamic mechanical analysis data indicated that up to 30% PMMA can be incorporated into PU networks without substantial phase separation. The PU–PMMA 90/10 IPNs elicit less than 2% hemolysis, suggesting that these materials could be used as blood contacting materials. © 1996 John Wiley & Sons, Inc.     

Interfacial studies of crosslinked polyurethanes; Part I. Quantitative and structural aspects of crosslinking near film-air and film-substrate interfaces in solvent-borne polyurethanes

One of the reactions leading to the formation of polyurethane (PU) crosslinked networks is the reaction of NCO and OH functionalities. In this study, we examined how crosslinking reactions of hexamethylene diisocyanate isocyanurate and polyacrylate near the film-air (F-A) and film-substrate (F-S) interfaces in urethane coatings may affect crosslink density as well as other network properties. While at the initial stages of the crosslinking reactions, solvent evaporation competes with the urethane network formation and isocyanate consumption changes at various depths from the F-A and F-S interfaces. Quantitative analysis of the NCO consumption as a function of depth showed that the NCO concentrations change from 2.35×10⁻⁵ to 2.09×10⁻⁵ M, while going from 0.27 to 1.14 μm. During reaction times not exceeding two to three hours, the NCO consumption at the F-A and F-S interfaces is consumed more rapidly. At low relative humidity conditions, excessive amounts of unreacted NCO exists at both the F-A and F-S interfaces. However, at the extended reaction times, NCO concentration levels at the F-S are greater than at the F-A interface, and the NCO concentration differences can be as high as 3×10⁻⁵ M. In this study we also examined how crosslinking reactions of hexamethylene diisocyanate (HDI) isocyanurate and polyacrylate near the F-S interfaces in urethane films may affect orientation and distribution of urethane functionalities. Department of Polymers and Coatings, Fargo, ND 58105.     

Reaction kinetics of polyurethane-polyester interpenetrating polymer network in the bulk polymerization

Kinetics of simultaneous interpenetrating networks (SIN) composed of a polyurethane resin (PU) and an unsaturated polyester resin was studied. A differential scanning calorimeter (DSC) was used to monitor the polymerization course. It was found that increasing the polyester content in a PU-polyester SIN enhanced the polymerization of PU due to the “solvent effect” of polyester. On the other hand, increasing the PU content in the SIN retarded the polymerization of polyester due to the “cage effect” of PU. Polymerization sequence of the SIN could be controlled by employing different initiators for polyester reaction. The degree of crosslinking in each SIN component had a significant effect on the dynamics of the SIN formation and on the limiting conversion of the polyester reartion.     

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.     

Relaxations and chain dynamics of sequential full interpenetrating polymer networks based on natural rubber and poly(methyl methacrylate)

The relaxations of natural rubber (NR)/poly(methyl methacrylate) (PMMA) interpenetrating polymer networks (IPNs) were studied using dynamic mechanical analysis, electron spin resonance (ESR) and solid state NMR spectroscopy. Samples with a lower concentration of PMMA in IPNs (25 wt%) showed only one relaxation, which corresponds to NR with a slight shift to higher temperature. IPNs with 35 wt% of PMMA showed very broad transitions arising from β‐ and α‐relaxations in PMMA, with the β‐relaxation slightly shifted to lower temperature. These compositions also showed a higher modulus at all temperatures. Highly phase separated IPNs showed a complete drop of modulus at 423 K. Higher crosslinking in the NR phase increases the miscibility and decreases the temperature difference between transitions, while in PMMA it increases the phase separation and does not affect the β‐relaxation of the PMMA chains. The ESR results showed that PMMA chains located in the PMMA‐rich and NR‐rich domains have different motional characteristics. The strong interaction between PMMA and NR chains was also observed by carbonyl relaxation in solid state NMR spectra. It was found that medium level crosslinking is needed for better interpenetration between phases. © 2013 Society of Chemical Industry     

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     

Characterization,separation performance,and model analysis of STPP‐chitosan/PAN polyelectrolyte complex membranes

Polyelectrolyte complex membranes (PCMs) were prepared using sodium tripolyphosphate (STPP) solution surface‐crosslinking chitosan/polyacrylonitrile (PAN) composite membranes. Fourier transform infrared (FTIR) was used to characterize the surface‐crosslinking. The effects of different surface‐crosslinking time on morphologies, element distribution, and crystal structures were investigated by scanning electron microscopy (SEM), energy dispersion of X‐ray (EDX), and X‐ray diffraction (XRD). The effect of crosslinking ratio on swelling ratio was analyzed. The separation performances of PCMs in terms of permeation flux and separation factor were measured by dehydrating ethyl acetate aqueous solutions. A kinetic model of crosslinking reaction was proposed to investigate the effect of crosslinking agent concentration and surface‐crosslinking time on the crosslinking ratio of PCMs. It was found that the membrane possessed the excellent performance when surface crosslinked for 15 min. The permeation flux and separation factor were 336 g/(m² h) and 6270 in 97 wt % ethyl acetate aqueous solution at 313 K. The crosslinking ratio of PCM exponentially increased as time increased, while linearly increased as concentration and diffusion coefficient of crosslinking agent STPP solution increased. And the effect of crosslinking agent concentration on crosslinking ratio was inversely proportional to surface‐crosslinking time. The experimental results matched well with the kinetic model when STPP concentration was lower than 5 wt %. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

接枝型PUA乳液合成及聚合动力学研究

甲基丙烯酸羟丙酯与水性聚氨酯预聚体反应,得到双烯封端的水性聚氨酯乳液。在乳化剂、引发剂存在下,将丙烯酸酯单体与水性聚氨酯乳液充分混合,并引发聚合,制备了接枝型PUA乳液。TEM观察了PUA乳液的形貌,PUA乳液的粒径在60～120 nm之间;FTIR和NMR表征了合成的PUA结构,显示丙烯酸酯的加入改变了PU本身的氢键相互作用;转化率测试表明,甲基丙烯酸羟丙酯与PU预聚体的反应具有二级动力学特征,而乳化剂的用量影响丙烯酸酯单体与双烯封端聚氨酯乳液的反应速率,反应速率与乳化剂用量符合Rp∝[SDS]0.28。     

Crosslinking of polystyrene by mono- and difunctional agents

Slightly crosslinked polystyrene networks are preferable to linear polystyrene in commercial uses where increased thermal properties are favoured. A novel method of production of macrocrosslinked networks has been developed by reaction of polystyrene with mono- and difunctional derivatives of p-xylene, durene and oligomeric chains (n<10) thereof. The reaction system consists of a common organic solvent such as acetic acid or butyl acetate and a catalyst such as H₂SO₄ or HClO₄; the reaction temperature varies between 60°C and 100°C. The degrees of crosslinking and thermal properties of the produced networks depend on the reaction system, the molar ratio of polymer to crosslinking agent and the reactivity of the functional groups; the gelation time varies between 3–12 hours for a fully crosslinked network. Promotion of the formation of regular structure networks without branches in the chains between crosslinks is achieved by the use of difunctional monomers, which favour the formation of linear polybenzylene chains between the polystyrene chains. Use of monofunctional monomers leads usually to branched and slightly crosslinked or grafted polystyrene. In both cases the regions of T_g and T_m increase up to 115°C and 350°C respectively as judged by DSC analysis. This novel crosslinking method has been also applied to crosslinking of copolymers of polystyrene and polymeric chains with aromatic structure in their backbone chain.