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。     

Chitin- polyurethane networks: correlations between physical properties and composition

Aiming to combine the bioproperties of chitin with the mechanical characteristics of polyurethane these two polymers were interconnected through a tridimensional network. The networks were formed from the addition reaction of the terminal isocyanate groups of a urethane prepolymer and the acetamide and hydroxyl groups of chitin. The crosslinking density was set from the ratio between the reacting groups, since the polyurethane length was kept constant (M_w = 66 kD, M_n = 48 kD). The biodegradability of polyurethane was afforded by the polycaprolactone segment of this component. The physical properties of the networks were analyzed in correlation with the composition, and compared with previous results obtained from blends with the same composition.     

Evaluation of the shrinking‐core model for examining the kinetics of film formation in a reactive latex blend

We prepared reactive latex blends from two copolymer latices comprised of n‐butyl methacrylate (n‐BMA) with acetoacetoxyethyl methacrylate and n‐BMA/dimethylaminoethyl methacrylate to study the kinetics of film formation. We generated thin films by blending equal weights of the two latices. The films were then cured at temperatures ranging from 50 to 90°C. The extent of the crosslinking reaction was calculated from the crosslink density, which was determined from swelling measurements of the films in toluene. The shrinking‐core model, a diffusion/reaction model, which was originally derived for combustion reactions of coal particles, was adopted to calculate the diffusion coefficient (D_e) and reaction rate constants from the extent of the reaction with time data. This model system exhibited a diffusion‐controlled regime above 70°C and a reaction‐controlled regime at temperatures below 70°C. In the reaction‐controlled regime, the shrinking‐core model predicted D_e for the system, which was in agreement with literature values for n‐BMA. In the diffusion‐controlled regime, the model predicted a lower apparent value for D_e but with an activation energy that was close to that obtained for n‐BMA. The model was also used to examine the kinetics of the crosslinking reaction. The kinetic rate constants for the crosslinking reaction were also determined. The activation energy for the crosslinking reaction was 18.8 kcal/mol, which compared reasonably with the activation energy of 22.8 kcal/mol determined for the reaction between the functional monomers as small molecules. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 3659–3665, 2006     

Catalyst effect on the crosslinking kinetics of a fluorine containing polyurethane network

A bicomponent fluorinated polyurethane coating was obtained by crosslinking a bifunctional, OH terminated perfluoropolyether oligomer with a fluorinated polyisocyanate based on the isophorone diisocyanate (IPDI) cyclic trimer. Three different tin containing catalysts (dibutyltin dilaurate (DBTDL), dibutyltin dimercaptide (DBTDM), tin octoate (TO)) were evaluated during the crosslinking reaction through gel time measurements and IR spectroscopy at various temperatures from +15 to +45°C. Both the methods showed a substantial higher activity of the first two catalysts, tin octoate being almost ineffective (latent) at ambient temperature. The spectroscopic measurements allowed the determination of apparent second‐order kinetic constants (k) of the crosslinking reaction. The activation energies E_a in the temperature range considered were obtained from the corresponding Arrhenius plot, showing a temperature dependence higher for DBTDM than DBTDL (8.5 vs. 7.0 kcal/mol). Finally, the conversion of the crosslinking reaction on the dry polymer film was estimated to be around 60–80% after 8 h at ambient temperature for DBTDM and DBTDL, but only 20–25% for TO catalyzed reactions. The formation of a hard urethane phase having a glass transition temperature T_g higher than the crosslinking temperature was considered as the main limiting factor of the overall reaction rate.     

Microwave assisted polymerisation of phenylacetylenes

Summary. Methathesis Polymerisation of phenylacetylenes using in situ generated (arene)M(CO)₃ complexes under unconventional microwave energy condition was achieved successfully. The reaction time was reduced to 1 hour in contrast to refluxing conditions of 24 hours. Received: 2 May 1997/Revised: 7 July 1997/Accepted: 9 July 1997     

Influence of microwave heating on the kinetic of acrylic acid polymerization and crosslinking

Kinetics of isothermal formation of poly (acrylic acid) (PAA) hydrogels through polymerization of acrylic acid and crosslinking of the PAA formed in a conventionally heated reaction system and in a microwave heated reaction system were investigated. It was found that in the microwave heated system the reaction rate constant of PAA hydrogel formation significantly increased (from 32 to 43 times) when compared with the conventionally heated system. The isothermal kinetics of the PAA hydrogel formation during the microwave process could be described by the so‐called first‐order chemical reaction kinetics model. In contrast, the so‐called second‐order chemical reaction rate model could best describe the isothermal kinetics of the PAA hydrogel formation during the conventionally heated process. Also, in the microwave heated system, the reaction kinetics of the PAA hydrogel formation and its kinetic parameters changed, that is, the activation energy (E_a) decreased by about 19% and the pre‐exponential factor (lnA) decreased by 2.2 times. The decrease in activation energy, change in entropy of activation energy, and decrease in the pre‐exponential value of PAA hydrogel formation under microwave heating are caused with increased energy of the reactive species when compared with their energy in thermal activation. Increased energy of the reactive species is a consequence of rapid transfer and absorption of the energy of microwave field to the existing reactive species. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Preparation and properties of reactive polyurethane polyacrylate blends based on carbonyl‐hydrazide reaction

A new reactive polyurethane/polyacrylate (PU/PA) blend was developed by mixing a core–shell polyacrylate latex containing keto groups in shell layer and a polyurethane dispersion incorporating multiple hydrazide groups which was synthesized by introducing the poly‐hydrazide groups into the end of the vinyl‐terminated polyurethane chains. Fourier transform infrared (FTIR) spectroscopy and gel permeation chromatography (GPC) results indicated that poly‐hydrazide groups had been incorporated in the polyurethane chains. Transmission electron microscopy (TEM) micrograph revealed that polyacrylate particles had a clear core–shell structure. The results of FTIR, scanning electron microscopy (SEM), and differential scanning calorimetry (DSC) indicated that the crosslinking reaction between two polymer systems had happened and crosslinking structure could effectively improve the compatibility between PA and PU. Thermogravimetric analysis (TGA) and mechanical tests results suggested that crosslinking structure could enhance the thermal stability and mechanical properties of blends. The influence of the PA content and the n(? CO? )/n(? NHNH₂) ratio on the hardness, water resistance, solvent resistance, and gel fraction of the blend films were comprehensively studied. The optimal PA content and n(? CO? )/n(? NHNH₂) ratio was 30% and 1.5:1 in this experiment, respectively. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134 , 44443.     

Temperature programmed desorption technique to predict the carbon oxygen reaction

The kinetics of the reaction o₂ oxygen with a sucrose char particle size: (88 μ<d_p<105 μrn) has been studied using a thermogravimetric analyzer (TGA) and a mass spectrometer (MS) to measure weight change and CO and CO₂ formation rates during reaction. Experiments were performed to determine the surface oxide formation rate and to determine the mechanism of CO desorption in the temperature range of 762 K to 851 K and for oxygen pressures of 0.04 to 0.3 atm, respectively. When the reaction rate at 30% conversion was used in the Arrhenius plot, an activation energy of 34±3 kcal/mol was obtained and the CO/CO₂ ratio was found to increase with increasing reaction temperature. Analysis of the rate of formation of CO and CO₂ shows the activation energy for CO formation is greater than for CO₂ formation. Temperature programmed desorption (TPD) studies of the surface oxides were made to provide a better understanding of the carbon oxidation process. The activation energy distribution function for desorption was approximately Gaussian and the average activation energy is 55 Kcal/mol for a preexponential factor of 10¹³ 1/sec. The peak of the energy distribution function shifts to higher activation energies for surface complexes formed at higher reaction temperature.     

Kinetic study of the reaction between hydroxyl-terminated polybutadiene and isophorone diisocyanate in bulk by quantitative FTIR spectroscopy

A kinetic study of the reaction between a hydroxyl-terminated polybutadiene (HTPB) and isophorone diisocyanate (IPDI) was carried out in the bulk state by using quantitative Fourier transform infrared (FTIR) spectroscopy. The reaction is shown to obey a second-order rate law, being first order in both the HTPB and IPDI concentrations. The activation parameters obtained from the evaluation of kinetic data are ΔH‡ = 41.1 ± 0.4 kJ mol, ΔS‡ = −198 ± 2 J K⁻¹ mol⁻¹ and E_a = 43.8 ± 0.4 kJ mol⁻¹, which are quite different from the solution values. However, they are in agreement with the results obtained on propellants by torsional braid measurements. The large negative value of the activation entropy is indicative of an associative mechanism, which is in accord with the second-order rate law for the polyurethane formation. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 66: 1979–1983, 1997     

Kinetics of epoxy resin formation from bisphenol-S,tetrabromobisphenol-A,and epichlorohydrin

The kinetics of formation of epoxy resins derived from bisphenol-S, tetrabromobisphenol-A, and epichlorohydrin under stoichiometric conditions was considered. The kinetics of reaction was studied by taking into account the consumption of the added alkali and the epoxide group of the epoxide oligomers. The obtained results satisfactorily explained that the reactivity of bisphenol-S with epichlorohydrin is higher than that of tetrabromobisphenol-A. The rate of dehydrochlorination of chlorohydrin ether in the presence of alkali and water was much higher than that of the rate of condensation of the phenolic hydroxyl group with epichlorohydrin. The apparent reaction order of the phenolic groups with epichlorohydrin and the terminal epoxide groups in the oligomer were second order. The rate constants and reaction activation energy were determined and results discussed. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 63: 1137–1142, 1997     

Rheological study of self‐crosslinking and co‐crosslinking of ammonium zirconium carbonate and starch in aqueous solutions

Different from common hydrogel systems formed by a polymer and a crosslinker, a hydrogel consisting of both self‐crosslinkable ammonium zirconium carbonate (AZC) and co‐crosslinkable starch was investigated in this study using rheological measurements. The evolution of viscoelastic properties of AZC solutions and AZC‐starch mixtures was characterized, and the crosslinking kinetics was determined. It was found that for both AZC self‐crosslinking and AZC‐starch co‐crosslinking, the initial bond formation rate and the gel strength exhibited a power law scaling with polymer concentrations. The competition reaction between self‐crosslinking and co‐crosslinking indicates that the gelation kinetics strongly depends on the AZC concentration but less depends on starch concentration. The temperature dependence of crosslinking was described by the Arrhenius plots which demonstrate a good linearity. It was determined that the activation energy of AZC self‐crosslinking was approximately 145–151 kJ/mol, and the activation energy of AZC‐starch co‐crosslinking was 139 kJ/mol. The effect of solution pH on the crosslinking process was also studied. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Motional heterogeneity and phase separation of semi-interpenetrating networks and mixtures based on functionalised polyurethane and polymethacrylate prepolymers

Semi-interpenetrating polymer networks (SIPNs) and polymer mixtures (1:1 mass ratio) based on segmented polyester polyurethane (PU) with carboxylic groups and methacrylic copolymer (PM) with tertiary amine groups were studied by the electron spin resonance (ESR) spin label method. The concentration of functional groups varied from 0 to 0.45 mmol g⁻¹ in both prepolymers. The ESR spectra of spin labelled PM component were used to characterise the heterogeneity of segmental motion and transitions due to the additional polymer interactions imposed by complementary functional groups. The results were deduced from the temperature dependent ESR spectra. Two component spectra reflect the effect of PU chains on segmental motion of the PM component below the macroscopic glass transition temperature, T_g. The ratio of the fast and slow component was related to the complex polymer-polymer interaction or extent of miscibility. Restrictions of segmental motion of PM chains increase with functional groups concentration and above certain concentration (0.25 mmol g⁻¹) PM segments in the network assess faster motion suggesting a change in the local packing density and domain structure. An increased miscibility and disorganisation of the ordered domains are confirmed by the loss of spherulitic morphology and crystallinity at higher functional groups concentration. PU/PM mixtures reveal similar motional behaviour as SIPNs of the same composition. However, the differences in the fractional amount of fast and slow motions confirm better interpenetration and interaction of the two polymers in the SIPNs. The results of motional heterogeneity and polymer interactions were complemented with the T_gs.     

Development and characterization of magnetorheological polymer gels

Magnetorheological materials have been used in many applications in recent years. To develop new materials, polyurethane and silicone polymer gels were investigated. Rheology is qualitatively controlled for each system by controlling the concentration of reactants and diluents. The resulting polymers have solid, gel, or liquid states, depending on the crosslinking and dilution. The gels were characterized through kinetic analysis. Differential scanning calorimetry (DSC) was used with analysis methods to find the kinetic properties for diluted and undiluted polyurethane systems. Heat of reaction, order of reaction, preexponential constant, and activation energy were obtained from the experimental DSC data. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 2733–2742, 2002     

Rheological investigation of cure kinetics and adhesive strength of polyurethane acrylate adhesive

In this work, we used rheological techniques to study both the cure characteristics and the degree of cure of polyurethane acrylate adhesive, a type of reactive adhesive used in hard disk component assembly. These results were then correlated with the tensile shear strengths of adhesives. Here, the cure characteristics of polyurethane adhesive were investigated at isothermal conditions ranging from 25 to 120°C. From the rheological results, the gelation time, the vitrification time, as well as the time required to reach the maximum degree of cure, decreased when increasing the curing temperature. The cure rates of adhesive increased with temperature in three temperature ranges, which were retardation zone, vitrification zone, and reaction‐controlled zone. The cure rates in these zones were controlled by slow diffusion, fast diffusion, and the rate of reaction, respectively. From the temperature sweep of fully‐cured adhesives, we found that the crosslinking level of adhesives increased with curing temperatures at different rates depending on the temperature zones as well. Moreover, the adhesive strength measured by tensile shear test was found to also increase correspondingly with the adhesives' T_g, indicating that the crosslinking level directly affected the adhesive strength. The strong dependence of adhesive strength with crosslinking level indicates that the crosslinking level was essential for high adhesive strength. The correlation of cure characteristics and adhesive strengths at various curing temperatures performed in this study can further provide useful information for planning appropriate curing schemes of polyurethane acrylate adhesives used in electronic and other industries. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

水性聚氨酯室温交联技术研究进展

介绍了近年来国内外水性聚氨酯室温交联技术的研究进展,并对这些交联体系及其交联机理作了较为详细的阐述。其包括9种室温交联方式,即:1羰基与酰肼基团的交联;2基于Michael加成反应的交联;3异氰酸酯基团的交联;4氮丙啶与羧基的交联;5环状碳酸酯与胺基的交联;6不饱和脂肪酸中双键的自氧化交联;7脂环族环氧基团与羧基的交联;8金属离子与羧基、磺酸基等螯合作用交联;9硅氧烷基团的水解缩聚交联。     

Tetraphenylethane iniferters: Polyurethane-polystyrene multiblock copolymers through “living” radical polymerization

Toluene diisocyanate-based polyurethane iniferters containing tetraphenyl-ethane groups in between polyurethane blocks were prepared by the reaction of isocyanate-terminated prepolymers and 1,1,2,2-tetraphenyl-1,2-ethanediol. When these iniferters were decomposed in the presence of styrene, polyurethane-polystyrene multiblock copolymers were obtained through a “living” radical mechanism. The effect of changing polyol on the T_g, thermal stability, and molecular weight of polyurethane iniferters as well as block copolymers was studied. The molecular weight of the block copolymers increased with increasing both polymerization time and conversion. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 66: 1551–1560, 1997     

Modeling solubility parameters and permeation data of organic solvents versus butyl gloves from four manufacturers

Polyurethanes by a nonisocyanate route were prepared by reacting carbonated soybean oil with different diamines. The effect of amine structure and carbonate to amine ratio on polyurethane structure and mechanical, physical, and swelling properties was studied. The reactants 1,2-ethylenediamine, 1,4-butylenediamine, and 1,6-hexamethylenediamine were used with the carbonate to amine ratio of 1 : 0.5, 1 : 1, and 1 : 2. It was found that along with urethane formation, the amine group reacted with ester groups to form amides. All amines produced elastomeric polyurethanes with glass transitions between 0 and 40°C and hardness between 40 and 90 Shore A. The reaction of epoxidized soybean oil with carbon dioxide was optimized resulting in complete conversion of epoxy to cyclic carbonate groups ending in polyurethanes with higher crosslinking density and much higher tensile strength than previously reported for similar polyurethanes. Swelling in toluene and water depended on crosslinking density and the polarity of polyurethane networks controlled by the cyclic carbonate-to-amine-ratio. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Novel flexible network polymers consisting of oligomeric primary polymer chains originated in the mechanistic discussion of multiallyl crosslinking polymerization

Summary It is well known that allyl monomers polymerize only with difficulty and yield polymers having low molecular weights, i.e., oligomers. Inevitably, free-radical multiallyl crosslinking polymerization provides network polymers consisting of oligomeric primary polymer chains, i.e., having abundant dangling chains. This led to the development of novel flexible network polymers such as amphiphilic network polymers (I) consisting of short primary polymer chains and long crosslink units with opposite polarities, simultaneous interpenetrating networks (II) consisting of both polyurethane (PU) and polymethacrylate (PM) networks with oligomeric primary polymer chains, and network polymers (III) consisting of centipede-type primary polymer chains. Thus, the solution copolymerizations of benzyl methacrylate with tricosaethylene glycol dimethacrylate in the presence of lauryl mercaptan yielded I consisting of nonpolar, short primary polymer chains and polar, long crosslink units. The opposite type of I was prepared by the copolymerization of 2-hydroxyethyl methacrylate, a polar monomer having a hydroxyl group, with heneicosapropylene glycol dimethacrylate, a nonpolar monomer having a poly(oxypropylene) unit. The equimolar polyaddition crosslinking reaction of poly(methyl methacrylate-co-2-methacryloyloxyethyl isocyanate) with tri(oxytetramethylene) glycol, leading to PU networks, and the free-radical crosslinking copolymerization of methyl methacrylate with tri(oxytetramethylene) dimethacrylate in the presence of CBr₄, leading to PM networks, were progressed simultaneously, providing II formed via the topological crosslink between PU and PM network structures. The post-copolymerizations of oligomeric allyl methacrylate/alkyl methacrylate precopolymers, having different amounts of pendant allyl groups and different molecular weights, with allyl benzoate/vinyl benzoate monomer mixtures were conducted to give III.     

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。     

Effect of temperature on the course of thiuram-accelerated sulfur vulcanization

Tetramethylthiuram disulfide-accelerated sulfur vulcanization of styrene-butadiene rubber has been investigated at temperatures from 100°C to 170°C over 0.5 to 600 min. Continuous measurements in a Vuremo curemeter were used to estimate the extent of crosslinking, which was plotted against cure time. Apart from the induction period (t_i), the kinetic graphs are satisfactory represented by a rate equation assuming three independent first-order reactions: fast crosslinking, degradation, and slow crosslinking. The rate equation contains seven kinetic parameters. Over the temperature range studied, there is no difference between the values of activation energy for t_i^?1, for fast crosslinking, and for degradation. The activation energy of slow crosslinking only is significantly greater. Due to the presence of Aerosil, the reciprocal values of the induction periods and the values of the ultimate extents of fast crosslinking are increased, and the values of the rate constants of degradation and slow crosslinking are decreased. Simultaneously, the activation energy of slow crosslinking is also significantly decreased. On the basis of these results, the proposed theory of tetramethylthiuram disulfideaccelerated sulfur vulcanization supposing that zinc dimethyldithiocarbamate is the actual accelerator in this type of curing system is discussed.