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1.
K. Siimer T. Kaljuvee P. Christjanson T. Pehk I. Saks 《Journal of Thermal Analysis and Calorimetry》2008,91(2):365-373
Thermal behaviour of cure-accelerated phenol-formaldehyde (PF) resins was studied using the addition of commercial mixture
of water soluble oil shale alkylresorcinols (AR) to PF resin, 5-MR being as model compound. The acceleration effect of AR
is based on the promotion of condensation of resin methylol groups and subsequent reaction of released formaldehyde with AR.
Commercial PF resins SFŽ-3013VL and SFŽ-3014 from the Estonian factory VKG Resins have been used. The chemical structure of
resins was characterised by 13C NMR spectroscopy. TG-DTA analysis was carried out using labsysTM instrument Setaram. By TG-DTA measurements, the shift of exothermic and endothermic peaks and the changes of mass loss rate
in the ranges of 1.5–10 g AR/100 g PF resin were studied. The effect of AR on the curing behaviour of PF resins was also followed
by gel time.
Testing of the plywood when using PF resin with 5 mass% of AR shows that the press time could be reduced by about 15%. 相似文献
2.
M. V. Alonso M. Oliet J. C. Domínguez E. Rojo F. Rodríguez 《Journal of Thermal Analysis and Calorimetry》2011,105(1):349-356
Resol resins are used in many industrial applications as adhesives and coatings, but few studies have examined their thermal
degradation. In this work, the thermal stability and thermal degradation kinetics of phenol–formaldehyde (PF) and lignin–phenol–formaldehyde
(LPF) resol resins were studied using thermogravimetric analysis (TG) in air and nitrogen atmospheres in order to understand
the steps of degradation and to improve their stabilities in industrial applications. The thermal stability of samples was
estimated by measuring the degradation temperature (T
d), which was calculated according to the maximum reaction rate criterion. In addition, the ash content was determined at 800 °C
in order to compare the thermal stability of the resol resin samples. The results indicate that 30 wt% ammonium lignin sulfonate
(lignin derivative) as filler in the formulation of LPF resin improves the thermal stability in comparison with PF commercial
resin. The activation energies of degradation of two resol resins show a difference in dependence on mass loss, which allows
these resins to be distinguished. In addition, the structural changes of both resins during thermal degradation were studied
by Fourier transform infrared spectroscopy (FTIR), with the results indicating that PF resin collapses at 300 °C whereas the
LPF resin collapses at 500 °C. 相似文献
3.
《Magnetic resonance in chemistry : MRC》2002,40(11):747-751
A total of 13 of the 16 possible methylol derivatives of 2,4′‐ and 4,4′‐dihydroxydiphenylmethane have been synthesized, isolated, and identified. These compounds are found as intermediates in the cure process of resol phenol–formaldehyde (PF) resins. Analysis of the 13C NMR spectra (in acetone‐d6) of these compounds provided a way to evaluate the seven methylolphenol ring types (methylol derivatives of 2‐hydroxyphenyl and 4‐hydroxyphenyl rings) found in typical resol PF resins using the ipso carbon region from 150 to 160 ppm. A simple diagnostic test was developed using the chemical shift values of the methylol methylene carbon atoms to identify the presence of intermediates containing either a 2‐hydroxyphenyl or a 4‐hydroxyphenyl ring. Using these data it is now possible to analyze the major components in extracted prepreg PF resins. Copyright © 2002 John Wiley & Sons, Ltd. 相似文献
4.
Changes in curing behaviour of aminoresins during storage 总被引:2,自引:0,他引:2
K. Siimer T. Kaljuvee P. Christjanson T. Pehk 《Journal of Thermal Analysis and Calorimetry》2005,80(1):123-130
Summary The curing behaviour of commercial UF and MUF resins, stored at room temperature nearly up to gelation, is studied by simultaneous TG-DTA technique and structural changes of resins are also followed during aging. On the basis of 13C NMR spectra, the main chemical reaction during UF resin storage is the formation of methylenes and dimethylene ethers linked to secondary amino groups. Aging of resins results in a decrease of cure rate which is related to lower concentration of active functional groups and decrease in molecular mobility. On DTA curve, the resin with higher content of methylol groups reveals the curing exotherm earlier. With decreasing methylol content during storage, the peak maximum of exotherm is shifted to higher temperature value. Advanced polycondensation and sedimentation processes during storage produce partly locked in macromolecule structure water, and the water evaporation endotherm on DTA curve shifts to considerably higher temperature. The aged MUF resins are chemically less changed than UF resins and the aging process mainly involves noncovalent network formation due to complex molecular structure. 相似文献
5.
Suzana Samaržija-Jovanović Vojislav Jovanović Sandra Konstantinović Gordana Marković Milena Marinović-Cincović 《Journal of Thermal Analysis and Calorimetry》2011,104(3):1159-1166
The thermal stability of pure urea–formaldehyde resin (PR) and modified urea–formaldehyde (UF) resins with hexamethylenetetramine-HMTA
(Resin 1), melamine-M (Resin 2), and ethylene urea (EU, Resin 3) including nano-SiO2 was investigated by non-isothermal thermo-gravimetric analysis (TG), differential thermal gravimetry (DTG), and differential
thermal analysis (DTA) supported by data from IR spectroscopy. Possibility of combining inorganic filler in a form of silicon
dioxide with UF resins was found investigated and percentage of free formaldehyde was determined. The shift of DTG peaks to
a high temperature indicates the increase of thermal stability of modified UF resin with EU (Resin 3) which is confirmed by
data obtained from the FTIR study. The minimum percentage (6%) of free formaldehyde was obtained in Resin 3. 相似文献
6.
Dariusz Szychowski Barbara Pacewska Grzegorz Makomaski Janusz Zieliński Wiesława Ciesińska Tatiana Brzozowska 《Journal of Thermal Analysis and Calorimetry》2012,107(3):893-900
The purpose of this study was to determine the possibility of producing hydrophobic mesoporous mineral–carbon sorbents from
aluminum hydroxide and compositions of coal tar pitch–polymers on carbonization at 600 °C in a nitrogen atmosphere. Blends
of the products of co-precipitation of aluminum hydroxide in the carbonaceous substances medium were subjected to carbonization
process. The extent of porous structure development was evaluated using low temperature nitrogen adsorption, adsorption of
benzene vapors, and adsorption of iodine from aqueous solution. The highest value of BET surface area of about 370 m2/g was achieved for the carbonization product obtained from co-precipitated raw components with 10 wt% compositions coal tar
pitch–polymer. These materials demonstrated high capacity to reduce organic pollutions from sewage. Pitch–polymer composition
containing poly(ethylene terephthalate) or phenol–formaldehyde resin was studied by the means of DSC method in order to determine
the high-temperature transformations taking place under the conditions of carbonization. DSC method enables to determine i.a.
the decomposition temperatures of carbonizates produced from pitch–polymer compositions and the evaluation of their sorption
abilities. The additive of poly(ethylene terephthalate) and phenol–formaldehyde resin caused the increase of thermal resistance
of the pitch expressed by higher decomposition temperatures. 相似文献
7.
Bunichiro Tomita Shiro Hatono 《Journal of polymer science. Part A, Polymer chemistry》1978,16(10):2509-2525
13C Fourier transform NMR has been used to characterize a random chemical structure of ureaformaldehyde resins. By comparison of 13C chemical shifts with synthesized standard derivatives from urea and formaldehyde the analysis of reacted formaldehyde was completed. In a 13C spectrum of resin each signal due to reacted formaldehyde (e.g., methylol group, methylene group, and dimethylene ether group) was isolated. Measurement of a 13C spectrum of resin by the gated decoupling of proton without nuclear Overhauser effect made a quantitative analysis of reacted formaldehyde possible. In this quantitative analysis a 13C quantity of carbonyl groups in urea residue can be directly compared with that of each combined formaldehyde. 相似文献
8.
Kadri Siimer Tiit Kaljuvee Tõnis Pehk Ilmar Lasn 《Journal of Thermal Analysis and Calorimetry》2010,99(3):755-762
Thermal behaviour of industrial UF resins modified by low level of melamine was followed by TG-DTA technique on the labsys TM instrument Setaram together with the 13C NMR analysis of resin structure and testing boards in current production at Estonian particleboard factory Pärnu Plaaditehas AS. DTA curve of UF resin which has been cocondensed during synthesis with even low level of melamine shows the shift of condensation exotherm and water evaporation endotherm to considerable higher temperatures. The effect of melamine monomer introduced to UF resin just before curing was compared. The effect of addition of urea as formaldehyde scavenger was studied. 相似文献
9.
Transformation
of dynamic DSC results into isothermal data for the curing kinetics study
of the resol resins 总被引:1,自引:0,他引:1
M. V. Alonso M. Oliet J. García F. Rodríguez J. Echeverría 《Journal of Thermal Analysis and Calorimetry》2006,86(3):797-802
Kinetics of thermosetting polymers curing is difficult to study by isothermal
methods based on the differential scanning calorimetry (DSC) technique. The
difficulty is due to the low sensitivity of the equipment for total reaction
heat measurements during high temperature process. The aim of this paper is
to display the equivalence between a dynamic model, the Ozawa method, and
an isothermal isoconversional fit, which allows predicting the isothermal
behavior of the resol resins cure through dynamic runs by DSC. In this work,
lignin–phenol–formaldehyde and commercial phenol–formaldehyde
resol resins were employed. In addition, the isothermal kinetic parameters
for both resins were performed by means of transformation of the data obtained
from the dynamic Ozawa method. 相似文献
10.
Gbolahan O. Shitta-Bey Mojtaba Mirzaeian Peter J. Hall 《Journal of Sol-Gel Science and Technology》2011,57(2):178-184
Organic gels have been synthesized by sol–gel polycondensation of phenol (P) and formaldehyde (F) catalyzed by sodium carbonate
(C). The effect of synthesis parameters such as phenol/catalyst ratio (P/C), solvent exchange liquid and drying method, on
the porous structure of the gels have been investigated. The total and mesopore volumes of the PF gels increased with increasing
P/C ratio in the range of P/C ≤ 8, after this both properties started to decrease with P/C ratio for P/C > 8 and the gel with
P/C = 8 showed the highest total and mesopore volumes of 1.281 and 1.279 cm3 g−1 respectively. The gels prepared by freeze drying possessed significantly higher porosities than the vacuum dried gels. The
pore volume and average pore diameter of the freeze dried gels were significantly higher than those of the vacuum dried gels.
T-butanol emerged as the preferred solvent for the removal of water from the PF hydrogel prior to drying, as significantly
higher pore volumes and specific surface areas were obtained in the corresponding dried gels. The results showed that freeze
drying with t-butanol and lower P/C ratios were favourable conditions for the synthesis of highly mesoporous phenol–formaldehyde
gels. 相似文献
11.
K. Siimer T. Kaljuvee P. Christjanson I. Lasn 《Journal of Thermal Analysis and Calorimetry》2006,84(1):71-77
TG-DTA
analysis method was used to study the curing behaviour of urea-formaldehyde
(UF) adhesive resins in the presence of a wood substrate. The cure process
was followed using a Setaram labsysTM instrument
in flowing nitrogen atmosphere by varying the ratio of resin and wood. Resin
cure was catalysed with 2% of NH4Cl. Curing tests were
performed in the open standard platinum crucibles and in the sealed glass
capsules. To characterise the reactivity of curing system, the peak temperatures
in DTA curve and the mass loss values in TG curve were taken as the apparent
indices. The main attention was paid to phenomena which actually take place
in curing of UF resins during manufacturing of particleboards. Reactivity
of the curing system depends mostly on methylol content of resin and can be
adequetly evaluated by the maximum temperature of exothermic peak. The wood
substrate has a substantial influence on the resin and water diffusion in
system causing the changes in water/resin separation and water evaporation
conditions. The water movement in curing adhesive joint was a confusing parameter
in determining the peak positions. The rate of mass loss on a wood substrate
is higher as compared to curing UF resin alone. 相似文献
12.
Jiang Jinxue Yang Yonglin Li Cheng Li Jianzhang 《Journal of Thermal Analysis and Calorimetry》2011,105(1):223-228
The purpose of the study was to investigate the effects of three kinds of flame retardant (FR), boric acid, zinc borate, and
borax on the thermal curing behavior of urea–formaldehyde (UF) resin. Both pH value and gel time were measured to study the
curing characters of the UF resin with different loading levels of FR. In addition, differential thermal analysis was also
used to obtain kinetic analyses parameter. The results showed that boric acid decreased pH value of UF resin, and reduced
gel time of the UF resin. There are no significant changes of the UF resin curing characters with different loading levels
of FR. The activation energies for curing reaction of UF resins in the presence of boric acid, zinc borate, and borax, were
84.37, 84.41, and 118.4 kJ/mol, respectively, higher than that of the control one (75.38 kJ/mol). All FRs showed adverse effect
on the curing behavior of the UF resin. 相似文献
13.
Bunichiro Tomita Hirokuni Ono 《Journal of polymer science. Part A, Polymer chemistry》1979,17(10):3205-3215
The random chemical structures of melamine–formaldehyde resins, including methylated melamine–formaldehyde resins and urea–melamine formaldehyde resins, were investigated by 13C-NMR spectroscopy (Fourier transform). All the combined formaldehydes, methylol and methyl ether groups, methylene structures, and dimethylene ether structures were assigned. A 13C chemical shift of methylene carbon occurred by substitution of other constituents of the methylene group for a proton of the adjacent monosubstituted nitrogen atom, as shown in a 13C-NMR spectrum of urea–formaldehyde resins. It was found that the chemical shift of each corresponding carbon of both melamine resins and urea–melamine resins was almost superimposed with that of urea resins. 相似文献
14.
Moon G. Kim 《Journal of polymer science. Part A, Polymer chemistry》1999,37(7):995-1007
Selected synthesis parameters of typical wood adhesive‐type urea–formaldehyde (UF) resins were examined using the 13C NMR spectroscopy. The monomeric hydroxymethylureas and methylene–ether derivatives formed in the initial alkaline reaction polymerize in the subsequent acidic reaction by forming methylene bonds and cleaving some hydroxymethyl groups as formaldehyde. For typical resin syntheses at F/U ratio of 2.10, the resulting UF polymer is found to be a number‐averaged pentamer having 3.25 polymer chain branches with about 80% of chain ends bonded to hydroxymethyl groups and the rest being free amide groups. When the second urea is added during the cooling period, about 67% of hydroxymethyl groups cleave from the UF polymeric components and the freed formaldehyde reacts with second urea to form monomeric hydroxymethylureas. This hydroxymethyl group move is suppressed when the second urea is added at low temperatures, suggesting that wood adhesive‐type UF resins are composed of monomeric and polymeric UF components having hydroxymethyl functional groups in varying proportions. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 995–1007, 1999 相似文献
15.
R. L. Bindu C. P. Reghunadhan Nair K. N. Ninan 《Journal of polymer science. Part A, Polymer chemistry》2000,38(3):641-652
Novel phenolic novolac resins, bearing maleimide groups and capable of undergoing curing principally through the addition polymerization of these groups, were synthesized by the polymerization of a mixture of phenol and N‐(4‐hydroxy phenyl)maleimide (HPM) with formaldehyde in the presence of an acid catalyst. The polymerization conditions were optimized to get gel‐free resins. The resins were characterized by chemical, spectral, and thermal analyses. Differential scanning calorimetry and dynamic mechanical analysis revealed an unexpected two‐stage curing for these systems. Although the cure at around 275°C was attributable to the addition polymerization reaction of the maleimide groups, the exotherm at around 150 to 170°C was ascribed to the condensation reaction of the methylol groups formed in minor quantities on the phenyl ring of HPM. Polymerization studies of non‐hydroxy‐functional N‐phenyl maleimides revealed that the phenyl groups of these molecules were activated toward an electrophilic substitution reaction by the protonated methylol intermediates formed by the acid‐catalyzed reaction of phenol and formaldehyde. On a comparative scale, HPM was less reactive than phenol toward formaldehyde. The presence of the phenolic group on N‐phenyl maleimide was not needed for its copolymerization with phenol and formaldehyde. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 641–652, 2000 相似文献
16.
TG-DTA study of melamine-urea-formaldehyde resins 总被引:2,自引:0,他引:2
K. Siimer P. Christjanson T. Kaljuvee T. Pehk I. Lasn I. Saks 《Journal of Thermal Analysis and Calorimetry》2008,92(1):19-27
The thermal behaviour of MUF resins from different suppliers with different content of melamine was studied, along with the 13C NMR spectroscopic analysis of resin structure and the testing of particleboards in current production at Estonian PB factory Pärnu Plaaditehas AS. The chemical structure of resins from DMSO-d6 solutions was analysed by 13C NMR spectroscopy on a Bruker AMX500 NMR spectrometer. The melamine level in different MUF resins is compared by the ratios of carbonyl carbon of urea and triazine carbon of melamine in 13C NMR spectra. Curing behaviour of MUF resins was studied by stimultaneous TG-DTA techniques on the Labsys? instrument Setaram. The shape of DTA curves characterisises the resin synthesis procedure by the extent of polymerisation of UF and MF components and is in accordance with structural data. 相似文献
17.
On the structure and cure acceleration of phenol-urea-formaldehyde resins with different catalysts 总被引:2,自引:0,他引:2
Phenol-urea-formaldehyde (PUF) resins with different catalysts [calcium oxide (CaO), sodium carbonate (Na2CO3), zinc oxide (ZnO), and magnesium oxide (MgO)] were prepared to accelerate the cure of the resin at low temperature. The cure-acceleration effects of catalysts on chemical structure and cure characteristics of PUF resins were investigated by using both liquid 13C nuclear magnetic resonance (NMR) and differential scanning calorimetry (DSC). The liquid 13C NMR analysis indicated that the catalyst such as CaO seemed to present a retarded effect on the polycondensation reaction of phenolic components with urea units, while the Na2CO3 appeared to promote the self-condensation reaction of phenolic methylol groups at para position toward the formation of para-para methylene linkage. Both ZnO and MgO in PUF resins promoted self-condensation reaction of para methylol groups and condensation reaction of ortho methylol groups with para methylol groups. The catalysts such as Na2CO3, ZnO, and MgO can make PUF resins cure at a low temperature. Among these catalysts, the MgO had the most significant accelerating effect on polycondensation and cure reaction of PUF resin. 相似文献
18.
Sung‐Seen Choi 《先进技术聚合物》2002,13(2):94-104
p‐t‐Octylphenol formaldehyde resole resins have two linkage types of methylene‐ and dimethylene ether‐linkages and have three terminal types of hydrogen, methylol, and o‐methylene quinone. Variation of structural characteristics of the resins due to different types of linkages and terminals were studied using molecular dynamics and molecular mechanics. The structural characteristics of the methylene‐bridged resins were intramolecular hydrogen bonds between hydroxyl groups of the adjacent p‐t‐octylphenols. In the dimethylene ether‐bridged resin, the intramolecular hydrogen bonds between oxygen atoms of the dimethylene ether‐linkages and hydroxyl groups of the neighboring phenolic units were found. For the resins with both methylol terminals, one of both terminals of the resins was hidden at the center of the molecule when the resin size is large. The number of hydrogen bonds in the resins with the methylol terminal was larger than for the resins with the o‐methylene quinone terminal. Variation of the structural characteristics of the resins by dehydration of the terminal methylol was discussed. Using the calculated results, dissociation of the dimethylene ether linkage and crosslinking reaction of rubber chains by the resin were explained. Copyright © 2002 John Wiley & Sons, Ltd. 相似文献
19.
酸性条件下脲醛树脂中不稳定结构的研究 总被引:2,自引:0,他引:2
通过较强酸性介质中尿素和甲醛的反应, 在不同条件下合成了透明的脲醛树脂溶液, 利用液体13C NMR研究了甲醛与尿素摩尔比对最终树脂中不稳定结构的影响. 相似文献
20.
D. R. Raut P. K. Mohapatra P. K. Wattal V. K. Manchanda 《Journal of Radioanalytical and Nuclear Chemistry》2012,292(2):661-666
Three different resins containing ammonium molybdophosphate (AMP), viz. PMMA (polymethylmethacrylate) resin, composite AMP
resin and ALIX (a bisphenol based resin), were evaluated for their irradiation stability. The studies included batch as well
as column studies and were carried out for cesium uptake behaviour at 3 M acidity. The resin beads were irradiated to varying
dose viz., 0 MRad, 10 MRad, 20 MRad, 50 MRad and 100 MRad. The time taken to attain equilibrium was rather long and about
2–5 h were found to be required for attaining equilibrium in batch studies. Batch Cs(I) uptake studies revealed no significant
effect on the K
d values in case of the PMMA resin while in case of the composite resin and ALIX resin, a decrease in the K
d was observed as a function of irradiation dose. The resin capacity indicated contrasting behaviour with irradiation dose
for the resins. Column runs have been carried out for the uptake of radio cesium using both unirradiated and irradiated resins
using feed solutions containing 3 MHNO3. The loading capacities of the resins were found to be proportional to their Cs loading capacities observed in batch studies.
Study revealed that the composite AMP had the maximum and PMMA has the least loading capacity. Results of these studies show
that these AMP based resins can be used for cesium separation from acidic nuclear waste. 相似文献