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81.
用富里哀变换红外光谱法原位跟踪不饱和聚酯树脂固化反应的动态过程。该方法能直接反映分子结构的变化,迅速准确地采集数据,尤其适用于快速反应体系。 相似文献
82.
对平衡硫化(EC)体系硫化天然橡胶(NR)的性能进行了研究,并与半有效硫化(SEV)体系和传统硫化(CV)体系硫化NR进行了对比。结果表明,EC体系返原作用略高于SEV体系,明显低于CV体系,硫化6h时的返原率依次为7.7%,0.4%和34.0%;与SEV和CV体系相比,EC体系NR硫化胶拉伸强度、撕裂强度和300%定伸应力高,生热低,耐磨性和耐屈挠性好。EC体系NR硫化胶的耐热氧老化性能优于SEV体系,更优于CV体系。 相似文献
83.
To improve the physicomechanical properties of jute yarn, grafting with 1,6‐hexanediol diacrylate (HDDA) monomer was performed by a UV radiation technique. A series of HDDA solutions of various concentrations in methanol were prepared. A small quantity of photoinitiator (Darocur‐1664) was also added to HDDA solutions. To optimize the conditions for grafting, the effects of monomer concentration, soaking time, and radiation doses were studied by varying the number of soaking times along with variation of monomer concentrations and UV radiation intensities. The extent of polymer loading and the mechanical properties like tensile strength (TS), elongation at break (Eb), and tensile modulus of both treated and untreated jute were investigated. The highest tensile strength, polymer loading, and modulus were achieved with 5% HDDA concentration, 5 min soaking time, and the 4th pass of UV radiation. This set of conditions was selected as optimum and produced enhanced tensile strength (67%), modulus (108%), and polymer loading (11%) over those of virgin fiber. To further improve the mechanical properties the jute yarns were pretreated with alkali (5% NaOH) solution and after that the alkali‐treated yarn were treated under UV radiation of various intensities. The pretreated samples were grafted with optimized monomer concentration (5% HDDA). Increased properties of alkali + UV‐pretreated and grafted samples such as polymer loading (12%), tensile strength (103%), elongation at break (46%), and modulus (114%) were achieved over those of virgin jute yarn. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 18–24, 2004 相似文献
84.
Fernando J. Beltrán 《臭氧:科学与工程》1997,19(1):13-38
Kinetics of competition between the ozone direct reaction with compounds in water, ozone-hydroperoxide ion reaction leading to free radicals in the O3/H2O2 process, and the photolysis of ozone in the O3/UV process are discussed in terms of diffusion and reaction times to establish conditions for these reactions to be competitive. Film theory and chemical kinetic concepts then are applied to estimate initial rates of ozone absorption and consumption, removal rates of compounds present in water, and the importance of the radical oxidation path versus direct ozone and/or photolysis reactions. 相似文献
85.
Uniform polyaniline (PANI) nanoparticles with typical sizes of about 50 nm were electropolymerized on indium tin oxide surfaces in the presence of Co2+, Ni2+, Cu2+, or Zn2+. According to shaping theory, we first suggest the reason forming PANI spherical particles. Their conductivity, UV‐vis spectra, FTIR spectra, X‐ray diffraction, and thermogravimetric analysis were investigated. The conductivities and crystallinity of PANI doped with these ions are higher than those of PANI doped with HCl (PANI/HCl). Both UV‐vis absorption spectra and FTIR spectra indicate the interactions between Co2+, Ni2+, Cu2+, or Zn2+ and PANI chains. TG analysis also shows that the thermal stability of PANI doped by Co2+, Ni2+, Cu2+, or Zn2+ is lower than that of PANI/HCl. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007 相似文献
86.
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88.
The Tg‐conversion relationship, during the thermal curing of different stoichiometric formulations of 1,1′‐(methylene‐di‐4,1‐phenylene) bismaleimide (BMI), modified with o,o′‐diallyl bisphenol A (DABA), was investigated. The DiBenedetto equation was used to model this relationship for the formulation of DABA‐1 (BMI : DABA, 1 : 1). Based on this model, the Tg‐conversion relationship of formulation DABA‐0.5 (BMI : DABA, 1 : 0.5) was modeled. The high consistency between the model curve and experimental data showed that the change of Tg, attributed to copolymerization between BMI and DABA in DABA‐0.5, in the low‐conversion regime, was the same as that in DABA‐1. This also verifies that, for the formulation DABA‐0.5, copolymerization and homopolymerization do not overlap with each other. The reactions progressed sequentially and homopolymerization occurred after completion of copolymerization. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 91: 3244–3247, 2004 相似文献
89.
选择了国内外几种环氧固化剂,配制成环氧树脂涂料,比较了环氧涂料的物理性能和防腐性能,考察了环氧涂料在不同温度下的固化情况,探讨了固化剂对低温施工性能的影响。 相似文献
90.
Lignin‐based wood adhesives are obtained that satisfy the requirements of relevant international standards for the manufacture of exterior‐grade wood particleboard. Formulations based on low molecular mass lignin and presenting an increase in the relative proportion of reactive points yield better results than the higher molecular mass lignin used in the past. These lignins allow a higher proportion of hydroxymethylation during preparation of methylolated lignins. These lignin‐based adhesives also yield acceptable results at particleboard pressing times that are sufficiently low to be of industrial significance. Lignin‐based wood adhesives, in which a nonvolatile nontoxic aldehyde (glyoxal) is substituted for formaldehyde in their preparation, are prepared and tested for application to wood panels such as particleboard. The adhesives yield good internal bond strength results for the panels, which are good enough to comfortably pass relevant international standard specifications for exterior‐grade panels. The adhesives also show sufficient reactivity to yield panels in press times comparable to that of formaldehyde‐based commercial adhesives. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 1690–1699, 2007 相似文献