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1.
Synthesis,rheological, and thermal properties of waterborne hyperbranched polyurethane acrylate dispersions for UV curable coatings 总被引:1,自引:0,他引:1
A series of waterborne hyperbranched polyurethane acrylate (WHUAs) ionomers used for ultraviolet curable waterborne coatings
were synthesized. The average particle size of aqueous dispersion ranged between 48.2 and 75.3 nm at 0.05% concentration determined
by laser light scattering. The effects of end group of WHUAs on rheological properties were investigated. WHUAs have much
lower viscosity than EB2002, commercial linear waterborne polyurethane acrylate. Moreover, the glass transition temperature
(Tg) evaluated by differential scanning calorimetry of samples showed that the influence of end capping by hard segment consisting
of toluene diisocyanate–hydroxyethyl acrylate is significant due to the increase of crosslink density. All cured WHUA have
higher glass transition temperatures than those of cured EB2002. The results of thermogravimetric analysis for cured WHUA
films indicated good thermal stability with no appreciable weight loss until 200°C, and that an increase in the hard segment
content provoked the increases in thermal degradation temperature. The activation energies were calculated by Flynn–Wall method
to be 91.3, 114.3, and 139.7 kJ mol−1 for cured WHUA62, WHUA44, and WHUA26, with the individual ratios of 6:2, 4:4, and 2:6 for salt-like group to double bond
at the terminals, compared with 81.1 kJ mol−1 of EB2002 in N2 atmosphere, respectively. 相似文献
2.
L. Katsikas K. Jeremic S. Jovanovic J. S. Velickovic I. G. Popovic 《Journal of Thermal Analysis and Calorimetry》1993,40(2):511-517
The effect of molar mass and, in the case of dextran, of the degree of branching on the thermal degradation kinetics of dextran and pullulan was studied in the presence and absence of oxygen. Although the initial mass loss of the dextran samples occurred at higher temperatures than that of the pullulan samples, the overall thermal degradation activation energies were lower for dextran than for pullulan. In the case of dextran the thermal stability was found to decrease with molar mass and degree of branching. The molar mass of pullulan, in the range of 104 to 105 g/mol, appeared to have no significant influence on the thermal characteristics of the samples. 相似文献
3.
A novel waterborne hyperbranched polyurethane acrylate for aqueous dispersions (WHPUDs) based on hydroxy‐functionalized hyperbranched aliphatic polyester Boltorn? H20 was investigated. The effects of structural composition and crosslinking density have been studied in terms of swellability by water, thermal degradation, viscosity changes as well as transmission electron microscopy (TEM) morphology. The swell ratio showed an increasing trend with the higher concentration of ionic group, which is due to the increased total surface area of particles. The results of thermogravimetric analysis (TGA) for cured WHPUD films indicated good thermal stability with no appreciable weight loss until 200°C. The activation energies were evaluated and were found in the range 154–186 kJ mol?1. It was observed that an increase in hard segment content provoked the increases in thermal degradation temperature and activation energy of waterborne dispersions. The transmission electron photographs revealed that the average particle sizes of aqueous dispersions were in the range 30–125 nm. Owing to the enlargement of the stabilization site, the particle size decreased as the content of carboxyl group and degree of neutralization increased. The viscosity of WHPUDs increased rapidly with increasing the degree of neutralization. Moreover, water showed a favorable viscosity reduction effect. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
4.
丙烯酸化环状磷腈/环氧丙烯酸酯光固化体系热降解动力学研究 总被引:2,自引:0,他引:2
以TGA为手段, 进行了丙烯酸化环状磷腈/环氧丙烯酸酯光固化体系热降解动力学的研究, 同时与加入粉末状环状磷腈混合体系进行了对照. 采用Kissinger, Flynn-Wall-Ozawa和Friedman三种方法计算了固化膜降解反应活化能, 证明了磷腈结构的引入, 使得体系在高温阶段的活化能有所提高, 表明降解变得困难, 热稳定性得到提高. 而反应型丙烯酸化环状磷腈相对粉末状环状磷腈混合体系具有更高的降解活化能. 相似文献
5.
Michael R. Salazar Joel D. Kress Bobby G. Russell Lorelei Woods 《Polymer Degradation and Stability》2009,94(12):2231-2240
The results of following the oxidative degradation of a plastic-bonded explosive (PBX 9501) are reported. Into over 1100 sealed containers were placed samples of PBX 9501 and combinations of its components and aged at relatively low temperatures to induce oxidative degradation of the samples. One of the components of the explosive is a poly(ester urethane) polymer and the oxidative degradation of the samples were following by measuring the molecular weight change of the polymer by gel permeation chromatography (coupled with both differential refractive index and multiangle laser light scattering detectors). Multiple temperatures between 40 and 64 °C were used to accelerate the aging of the samples. Interesting induction period behavior, along with both molecular weight increasing (crosslinking) and decreasing (chain scissioning) processes, were found at these relatively mild conditions. The molecular weight growth rates were fit to a random crosslinking model for all the combinations of components. The fit rate coefficients show Arrhenius behavior and activation energies and frequency factors were obtained. The kinetics of molecular weight growth shows a compensatory effect between the Arrhenius prefactors and activation energies, suggesting a common degradation process between PBX 9501 and the various combinations of its constituents. An oxidative chemical mechanism of the polymer is postulated, consistent with previous experimental results, that involves a competition between urethane radical crosslinking and carbonyl formation. 相似文献
6.
Thermal degradation and stability of poly(4-vinylpyridine) homopolymer and copolymers of 4-vinylpyridine with methyl acrylate 总被引:3,自引:0,他引:3
The thermal stability and degradation behaviour of poly(4-vinylpyridine) (PVP) homopolymer and copolymers of 4-vinylpyridine and methyl acrylate (VP-MA) have been investigated. The reactivity ratios in the copolymerization were determined using an NMR method. The apparent activation energies of the degradation of the homopolymers and copolymers were calculated using the Arrhenius equation. 相似文献
7.
Harini Kilambi Sirish K. Reddy Lauren Schneidewind Jeffrey W. Stansbury Christopher N. Bowman 《Journal of polymer science. Part A, Polymer chemistry》2009,47(19):4859-4870
The impact of secondary functionalities on the radical‐vinyl chemistry of monoacrylates characterized by secondary functionalities that dramatically enhance their polymerization rate was elucidated utilizing experimental and computational techniques. Firstly, bulk interactions affecting the acrylate reactivity towards photopolymerization were removed by polymerizing at 5 wt % monomer in 1,4‐dioxane. Following deconvolution of bulk interactions impacting reactivity towards photopolymerization, a linear correlation between average polymerization rates and Michael addition reaction rate constants was observed on a logarithmic scale. This result indicates that the presence of the secondary functionality intramolecularly alters the monomer chemistry in a manner which impacts both of these distinct reaction types in a similar manner. These monomers exhibited reduced activation energies in both Michael addition and photopolymerization reactions as compared to hexyl acrylate. Reduction up to 20 ± 8 kJ mole?1was observed for Michael addition reactions and 12 ± 1 kJ mole?1 for photopolymerization reactions, thereby explaining the higher reactivity of the acrylates characterized by the secondary functionalities. Cyclic voltammetry experiments conducted to investigate the nature of the acrylic double bonds indicated that the rapidly polymerizing acrylates are more readily reduced as compared to traditional acrylates. Further, a distinct monotonic correlation of the irreversible cathodic peak potentials of the (meth)acrylates to photopolymerization and Michael addition reactivity was observed. The computationally estimated acrylic LUMO energies characterized by the secondary functionalities (?2.3 eV to ?2.7 eV) were also found to be lower relative to hexyl acrylate (?2.2 eV). © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 4859–4870, 2009 相似文献
8.
Amphiphilic urethane acrylate hydrogels having heterophasic gel structure: swelling behaviors and mechanical properties 总被引:1,自引:0,他引:1
Amphiphilic urethane acrylate hydrogels containing ionic group (dimethylopropionic acid, DMPA) were prepared by varying the
molecular weight of the soft segment (polyether type, PTMG) and type of diisocyanate, and their swelling behaviors and mechanical
properties were examined. They showed amphiphilic property due to the hydrophilic ionic groups and hydrophobic polyethers
comprising the urethane acrylate network. Heterophasic gel structure could be found for the hydrogels prepared in water, but
not for the hydrogels in organic solvent (1,4-dioxane), through scanning electron microscopy. Because of this heterophasic
gel structure, they were able to take in a large amount of water as well. The hydrophobic interaction generated by the polyether
soft segments between urethane acrylate network chains decreased the degree of swelling, however, increased reversibly the
tensile strengths at equilibrium swelling state. MDI-based hydrogel showed low swelling ratio and high tensile strength because
of its ordered hard domain structure. These amphiphilic urethane acrylate hydrogels showed salt- and pH-dependent swelling
behaviors.
Received: 26 September 1997 Accepted: 24 December 1997 相似文献
9.
Zhanguang Huang 《Polymer Degradation and Stability》2006,91(8):1674-1684
Poly(bisphenyl acryloxyethyl phosphate) (BPAEP) was blended in different ratios with urethane acrylate EB220 to obtain a series of UV curable flame-retardant resins. The thermal degradation mechanisms of their cured films in air were studied by thermogravimetric analysis, in situ FTIR and direct pyrolysis/mass spectrometry measurements. The results showed that BPAEP/EB220 blends have lower initial decomposition temperatures (Tdi) and higher char residues than pure EB220, while BPAEP has the lowest Tdi and the highest char residue. The degradation process of BPAEP was divided into three characteristic temperature regions, attributed to the decomposition of phosphate, ester group and alkyl chain, and aromatic structure in the film. 相似文献
10.
采用TGA-MS,FTIR和TGA-DTA等分析手段,研究了多元巯基化合物-乙烯基硅氮烷预聚物组成的紫外光固化体系制备的聚合物陶瓷前驱体共聚物在氮气中的热解机理和动力学.结果表明,裂解主要发生在280~430℃,430~560℃和560℃以上3个阶段,明确了各阶段主要发生的化学反应,发现硫元素主要是以H2S和SO2逸出.采用Vachuska-Voboril和Friedman法对不同巯基官能度和不同巯基化合物用量的共聚物热解动力学参数计算表明,增加巯基化合物官能度,第一阶段的热解反应活化能和反应级数相应增大;改变巯基化合物用量使得初始的热解活化能降低,并导致最终陶瓷收率降低.巯基与乙烯基摩尔比分别为2∶1和1∶3的共聚物的热解表观活化能(0.05≤α≤0.65时)分别为175~195 kJ/mol和95~118 kJ/mol. 相似文献
11.
Miloš Milovanovi? 《Polymer Degradation and Stability》2006,91(12):3221-3229
The kinetics and mechanism of the thermal degradation of poly(diethyl fumarate) (PDEF) were studied by thermogravimetry, as well as by analysis of the thermolysis volatiles and polymer residue. The characteristic mass loss temperatures were determined, as were the overall thermal degradation activation energies of three PDEF samples of varying molar mass. Ethylene and ethanol were present in the thermolysis volatiles at degradation temperatures below 300 °C, while diethyl fumarate was also evidenced at higher degradation temperatures. The amount of monomer increased with increasing degradation temperature. The dependence of the molar mass of the residual polymer on the degradation time and temperature was established and the number of main-chain scissions per monomer unit, s/P0, calculated. A thermal degradation mechanism including de-esterification and random main-chain scission is proposed. The thermal degradation of PDEF was compared to the thermolysis of poly(ethyl methacrylate) (PEMA), poly(diethyl itaconate) (PDEI) and poly(ethyl acrylate) (PEA). 相似文献
12.
Preparation of PEG-modified urethane acrylate emulsion and its emulsion polymerization 总被引:5,自引:0,他引:5
In order to improve stability and reduce droplet size, the PEG-modified urethane acrylates were synthesized by the reaction of polyethylene glycol (PEG) with residual isocyanate groups of urethane acrylate to incorporate hydrophilic groups into the molecular ends. The droplet sizes of the PEG-modified urethane acrylate emulsions were much smaller than those of unmodified urethane acrylate emulsions at the same surfactant composition, and the droplet sizes of these emulsions were significantly effected not by surfactant compositions and types, but by the reaction molar ratio of PEG, because the urethane acrylate containing polyoxyethylene groups as terminal groups aided the interfacial activity of surfactant molecules and acted as a polymeric surfactant. The actions of PEG-modified urethane acrylate were confirmed by the investigation of adsorption of urethane acrylate in a water/benzene interface.For polymerization of emulsions, the stability of emulsion in the process of emulsion polymerization was changed by the type of surfactant or initiator. In the case of emulsion polymerization with a water soluble initiator (K2S2O8), the emulsions prepared using TWEEN 60 were broken in the process of polymerization. However, polymerization of these emulsions could be carried out using an oil soluble initiator (AIBN). The conversion of emulsion polymerization changed with the type of urethane acrylates, that is, the reaction molar ratio of PEG to 2-HEMA. 相似文献
13.
Monodisperse micron-sized polystyrene particles crosslinked using urethane acrylate were produced by dispersion polymerization
in ethanol solution and the effect of the crosslinked network structure on the polymerization procedure was studied. The influences
of the concentrations of the initiator and urethane acrylate on the particle diameter (D
n), the particle number density (N
p), and the polymerization rate (R
p) were found to obey the approximate relationships D
n ∝ [initiator]0.43 [urethane acrylate]0.05, N
p ∝ [initiator]−1.30 [urethane acrylate]0.19, and R
p ∝ [initiator]0.24 ± 0.02. The power-law dependence of D
n and N
p on the initiator concentration showed a similar trend to that of linear polystyrene reported in the literature. Especially,
it was found that urethane acrylate does not have a serious effect on D
n and N
p of the particles produced. The dependence of R
p on the initiator concentration was observed to be higher than that of linear polystyrene, suggesting that there is still
competition between heterogeneous polymerization and solution polymerization because of the crosslinked network structure
of the primary particle.
Received: 1 April 1999 Accepted in revised form: 29 June 1999 相似文献
14.
Kinetics
of polyurethane formation between several polyols and isocyanates with dibutyltin
dilaurate (DBTDL) as the curing catalyst, were studied in the bulk state by
differential scanning calorimetry (DSC) using an improved method of interpretation.
The molar enthalpy of urethane formation from secondary hydroxyl groups and
aliphatic isocyanates is 72±3 kJ mol-1
and for aromatic isocyanates it is 55±2 kJ mol-1
. In the case of a single second order reaction for aliphatic isocyanates
reaction, activation energy is 70±5 kJ mol-1
with oxypropylated polyols and 50±3 kJ mol-1
with Castor oil. For aromatic isocyanates and oxypropylated polyols the activation
energy is higher around 77 kJ mol-1 .
In the case of two
parallel reactions (situation for IPDI and TDI 2-4) best fits are observed
considering two different activation energies. 相似文献
15.
Kenzi Hori Nobuhisa Saitoh Shinjiro Kobayashi Tsugio Kitamura 《Theoretical chemistry accounts》1999,102(1-6):244-251
β, γ-Substituted γ-halo allylalkoxide ions decompose to form a halogen ion, formaldehyde, and an alkyne under mild conditions,
for example at room temperature. The E isomer does not differ from the Z isomer in terms of activation energy. We attempted
to shed light on the mechanism of the reaction by using ab initio molecular orbital calculations. The observed propensity
was confirmed by the present calculation on model molecules, γ-chloro allylalkoxide ions. We conducted further calculations
and compared the alkoxide results with a similar reaction of β-haloacrylate ions that release carbon dioxide instead of formaldehyde.
This similar reaction needs heating as high as 150°C. The activation energy of the acrylate ions (36–39 kcal mol−1) was calculated to be about 10 kcal mol−1 higher than that of the alkoxide ions. The activation energy of the E acrylate ion is smaller by 0.8 kcal mol−1 than that of the Z isomer at the MP2/6-31+G**//RHF/6-31+G* level of theory. This is consistent with experimental results.
While the ready deprotonation from the carboxylic group does not activate the acrylate ion very much, the alkoxide ion is
destabilized to a great degree in the process of anion formation. The difficulty in deprotonation that proceeds from the neutral
molecule is seen in the difference in the activation energies for the decomposition of the corresponding anions. Therefore,
the pK
a of a hydroxy or a carboxylic group plays the leading role in determining the magnitude of activation energies of allyl halides
with a negatively charged fragment.
Received: 2 July 1998 / Accepted: 9 September 1998 / Published online: 8 February 1999 相似文献
16.
The morphology of micron-sized polystyrene particles crosslinked with a urethane acrylate crosslinker was studied with different
concentrations of urethane acrylate and medium solvency by means of simple dispersion polymerization. The urethane acrylate
employed as a crosslinker showed an excellent effect on maintaining the monodispersity of the polystyrene particles at a moderate
crosslinker concentration (to about 5 wt%) in terms of the monomer-swellable surface of primary particles. By enhancing the
medium solvency, the amount of urethane acrylate incorporated was increased, while the monodispersity of the final particles
was maintained. It was believed that the increase in solvency on adding xylene to ethanol solution helped the diffusion of
the styrene monomers into the primary particles. At high concentration of urethane acrylate, however, nonspherical particles,
ellipsoidal or egg-like singlets and asymmetric doublets, were observed. The increased crosslinking density seemed to repel
the styrene monomers during particle growth.
Received: 30 June 1998 Accepted in revised form: 9 September 1998 相似文献
17.
Several
dynamic methods for estimating activation energies have been developed. This
development has arisen largely as a matter of convenience and the desire to
minimize analysis time. While these methods generally afford values which
are somewhat similar, the agreement among values from various methods is never
outstanding. Further, the values obtained are often, at best, only approximations
of the values obtained by the traditional isothermal approach. To better ascertain
the utility of dynamic methods for the determination of activation energies,
the activation energy for the thermal degradation of a standard vinylidene
chloride/methyl acrylate (five-mole percent) copolymer has been generated
by a variety of methods. The degradation of this polymer is an ideal reaction
for evaluation of the various methods. At modest temperatures (<200°C),
the only reaction that contributes to mass loss is the first order evolution
of hydrogen chloride, i.e., there is only one significant reaction occurring
and it is not impacted by competing processes. The best values (most reproducible;
best correspondence to values obtained by titrimetry and other methods) are
those obtained by plotting the natural logarithm of rate constants obtained
at various temperatures vs. the reciprocal of the Kelvin temperature. Various
dynamic methods yield values which are less reproducible and which approximate
these values to a greater or lesser degree. In no case is the agreement good. 相似文献
18.
Poly(methyl methacrylate) hollow particles by water-in-oil-in-water emulsion polymerization 总被引:4,自引:0,他引:4
Poly(methyl methacrylate) particles having hollow structures were produced by water-in-oil-in-water (W/O/W) emulsion polymerization
where sorbitan monooleate (Span80) was used as a primary surfactant and sodium laurylsulfate and Glucopen (APG, polypeptide
derivative) were used as secondary surfactants. Urethane acrylate having a molecular structure with a hard segment in the
molecular backbone, a long soft segment in the middle, and vinyl groups at both ends was employed as a reactive viscosity
enhancer. At low concentration of urethane acrylate, only a few particles contained a void in the polymer phase. However,
as the concentration of urethane acrylate increased, the number of the particles containing the void increased. This was because
urethane acrylate increased the viscosity of the monomer mixture and helped to form the stable W/O/W emulsion droplets, which
possibly restricted droplet coalescence during emulsion polymerization. Moreover, at high concentration of urethane acrylate
(above 7 wt%), multi-hollow-structured particles were obtained. It is believed that the increase in the lyophilicity of the
monomer mixture caused by urethane acrylate led to stronger interfacial activity of the primary surfactant (Span80) and finally
resulted in many internal aqueous droplets.
Received: 31 July 1998 Accepted: 13 October 1998 相似文献
19.
Ting Hu Su Chen Yuan Tian John A. Pojman Li Chen 《Journal of polymer science. Part A, Polymer chemistry》2006,44(9):3018-3024
We report the first synthesis of urethane–acrylate copolymers via free‐radical frontal polymerization. In a typical run, the appropriate amounts of the reactants (urethane–acrylate macromonomer and 2‐hydroxyethyl acrylate) and initiator (ammonium persulfate) were dissolved in dimethyl sulfoxide. Frontal polymerization was initiated by the heating of the wall of the tube with a soldering iron, and the resultant hot fronts were allowed to self‐propagate throughout the reaction vessel. Once it was initiated, no further energy was required for the polymerization to occur. The dependence of the front velocity and front temperature on the initiator concentration was investigated. The front temperatures were between 55 and 65 °C, depending on the persulfate concentration. Thermogravimetric analysis indicated that the urethane–acrylate copolymers had higher thermal stability than pure frontally prepared polyurethane. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 3018–3024, 2006 相似文献
20.
Epoxy acrylate dispersions stabilized using urethane acrylate anionomers were prepared for an application of ultraviolet
(UV) curing. By observing the optical microscopy and colloidal stability for the epoxy acrylate dispersions, it was confirmed
that the urethane acrylate anionomers incorporated have an interfacial activity in the interface between the epoxy acrylate
oil and the water/ ethanol mixture (80/20, w/w). This was possible by the structurally designed urethane acrylate anionomers,
containing a hydrophobic soft segment and two hydrophilic ionic sites in their molecules. In addition, when ultraviolet (UV)-cured,
the urethane acrylate anionomers agglomerated to form the rubber domains in the epoxy acrylate film, which were induced by
the ionic interaction. Consequently, this agglomerated rubber domains improved the final film properties.
Received: 4 April 1998 Accepted: 1 July 1998 相似文献