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1.
The structure of oligomers obtained from mono‐hydroxymethylphenols in melt condensation at 120°C was determined using 13C NMR spectra in CD3OD solution. Alongside of methylene region of spectrum, valuable information was obtained from signals of aromatic carbons. Noncatalytic conditions promote the formation of dihydroxydibenzyl ethers in equilibrium with ortho‐ and para‐benzoquinones of oxymethylene derivatives. The final methylene linked oligomers are formed, mainly, by splitting the ether intermediates with free aromatic positions. In alkaline conditions, highly nucleophilic phenoxide ions of ortho‐hydroxymethyl compounds are responsible for substitution in free aromatic positions. The most favored reaction in the mixture of both hydroxymethylphenols is the formation of p,p′‐methylene. In condensation of para‐hydroxymethylphenol, formation of p,p′‐methylene groups occurs with simultaneous release of formaldehyde. High content of alkali stabilized ortho‐hydroxymethyl groups of fully substituted methylene linked oligomers determines the curing behavior of resol phenol–formaldehyde resins. The role of hemiformals in reactions was insignificant. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2008 相似文献
2.
Formaldehyde–urea (F/U) reaction products with molar ratios of 1.8, 2.1, and 2.4 were synthesized at pH 8.3, and the last one also at pH 4.5 using 45% formaldehyde aqueous solution. For obtaining the resin, the synthesis of F/U 2.1 was continued by acid‐catalyzed condensation at pH 4.5 and posttreatment with second part of U (F/U 1.05/1) at 70°C and pH 8.3. The products were analyzed using 13C‐NMR spectrometry. Higher excess of F increases the dihydroxymethyl content on account of smaller dimethylene ether content. Certain 13C chemical shifts in carbonyl and methylene region of spectra were assigned to trishydroxymethylurea, being the main trisubstituted urea compound in hydroxymethylated product. Acid catalyst promotes the formation of methylene groups by polycondensation of hydroxymethyl groups, against the background of similar content of dimethylene ethers in both catalytic conditions. The ratio of linear/branched chains is emphasized in characterizing the resin structure. Higher hydroxymethyl content in acid‐catalyzed polycondensation is an advantage of three‐step synthesis technology. The amount of binding methylene and dimethylene ether groups linked only to secondary amino groups can be increased by transhydroxymethylation with subsequent polycondensation in posttreatment with U in suitable reaction conditions. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 1673–1680, 2006 相似文献
3.
Effects of resin formulation, catalyst, and curing temperature were studied for particleboard binder‐type urea‐formaldehyde (UF) and 6 ～ 12% melamine‐modified urea‐melamine‐formaldehyde (UMF) resins using the dynamic mechanical analysis method at 125 ～ 160°C. In general, the UF and UMF resins gelled and, after a relatively long low modulus period, rapidly vitrified. The gel times shortened as the catalyst level and resin mix time increased. The cure slope of the vitrification stage decreased as the catalyst mix time increased, perhaps because of the deleterious effects of polymer advancements incurred before curing. For UMF resins, the higher extent of polymerization effected for UF base resin in resin synthesis increased the cure slope of vitrification. The cure times taken to reach the vitrification were longer for UMF resins than UF resins and increased with increased melamine levels. The thermal stability and rigidity of cured UMF resins were higher than those of UF resins and also higher for resins with higher melamine levels, to indicate the possibility of bonding particleboard with improved bond strength and lower formaldehyde emission. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 377–389, 2005 相似文献
4.
In this study, in situ modified phenol formaldehyde resins were prepared from hydroxyl terminated polydimethyl siloxane (DH.PDMS), clay (montmorillonite) in the presence of base catalyst. Different clay contents (0.5, 1, 3, 5 wt %) were used to produce DH.PDMS modified resol/clay nanocomposite resins (DH.PDMS‐LC‐PFRs). DH.PDMS‐LC‐PFRs were partially cured by heat, and the effects of the curing process and the clay content in the resol resin were determined on the spectroscopic, thermal, mechanical and microscopic properties of the final products. Furthermore, the effects of the reaction time on the polymerization and on the morphology of the materials were investigated. The structures of the specimens were characterized by means of Fourier Transform Infrared (FTIR‐ATR) spectroscopy. Thermal properties of the samples were determined with Differential Scanning Calorimeter (DSC) and Thermogravimetric Analyzer (TGA). Mechanical properties of the specimens were determined by Dynamic Mechanical Analyzer (DMA). The obtained samples were also characterized morphologically by Scanning Electron Microscope (SEM). © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013 相似文献
5.
Terpolymers (2,4‐DHPBF) were synthesized by the condensation of 2,4‐dihydro‐xypropiophenone, biuret, and formaldehyde in the presence of acid catalyst with varying the molar ratio of reacting monomers. Terpolymer composition has been determined on the basis of their elemental analysis and their number–average molecular weight of these resin were determined by conductometric titration in nonaqueous medium. The viscosity measurements were carried out in N,N‐dimethyl formamide which indicate normal behavior. IR spectra were studied to elucidate the structure. The terpolymer resin has been further characterized by UV–visible and 1H‐NMR spectra. The newly synthesized terpolymers proved to be selective chelating ion‐exchange terpolymers for certain metals. The chelating ion‐exchange properties of this terpolymer was studied for Fe (III), Cu (II), Hg (II), Cd (II), Co (II), Zn (II), Ni (II), and Pb (II) ions. A batch equilibrium method was employed in the study of the selectivity of metal ion uptake involving the measurement of the distribution of a given metal ion between the terpolymer sample and a solution containing the metal ion. The study was carried out over a wide pH range and in media of various ionic strengths. The terpolymer showed a higher selectivity for Fe (III), Hg (II), Cd (II), and Pb (II) ions than for Cu (II), Co (II), Zn (II), and Ni (II) ions. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 相似文献
6.
Terpolymers have been prepared by the condensation of 2,4‐dihydroxyacetophenone (2,4‐HA) and dithiooxamide (D) with formaldehyde (F) in the presence of hydrochloric acid as catalyst with varying the molar proportions of the reactant. Compositions of the terpolymer have been determined by elemental analysis. The number average molecular weight has been determined by conductometric titration in nonaqueous medium. Intrinsic viscosities of the solution of the terpolymer have been determined in N,N‐dimethyl formamide (DMF). The terpolymers have been characterized by UV–visible, IR, and proton NMR spectra. Chelation ion‐exchange properties have also been studied employing the batch equilibrium method. It was employed to study selectivity of metal ion uptake over a wide pH range and in media of various ionic strength. The overall rate of metal uptake follows the order: Fe3+ > Cu2+ > Ni2+ > Co2+ = Zn2+. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 相似文献
7.
To lower the formaldehyde emission of wood‐based composite panels bonded with urea–formaldehyde (UF) resin adhesive, this study investigated the influence of acrylamide copolymerization of UF resin adhesives to their chemical structure and performance such as formaldehyde emission, adhesion strength, and mechanical properties of plywood. The acrylamide‐copolymerized UF resin adhesives dramatically reduced the formaldehyde emission of plywood. The 13C‐NMR spectra indicated that the acrylamide has been copolymerized by reacting with either methylene glycol remained or methylol group of UF resin, which subsequently contributed in lowering the formaldehyde emission. In addition, an optimum level for the acrylamide for the copolymerization of UF resin adhesives was determined as 1%, when the formaldehyde emission and adhesion strength of plywood were taken into consideration. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 相似文献
8.
Terpolymer resins (2‐HAMF) were prepared by the condensation of 2‐hydroxyacetophenone and melamine with formaldehyde in the presence of acid catalyst and using varied molar ratios of reacting monomers. Compositions of terpolymers have been determined by elemental analysis. The number average molecular weights (Mn) have been determined by conductometric titration in nonaqueous medium. Viscometric measurements in dimethyl sulfoxide have been carried out with a view to ascertain the characteristic functions and constants. Electronic spectra, infrared and nuclear magnetic resonance spectra were studied to elucidate the structure. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 相似文献
9.
Phenol‐urea‐formaldehyde (PUF) resins were synthesized by reacting mixture of methylolureas (MMU), phenol, and formaldehyde. The structure of PUF cocondensed resins at different stages of reaction were analyzed by liquid 13C nuclear magnetic resonance (NMR) spectroscopy. The liquid 13C‐NMR analysis indicated that methylolureas had the dominant content in MMU with the reaction between urea and formaldehyde under the alkaline condition. The PUF cocondensed resins had no free formaldehyde. methylolureas were well incorporated into the cocondensed resins by reacting with phenolic units to form cocondensed methylene bridges. The second formaldehyde influenced the further reaction and the structure of the PUF resins. The resins with the prepared method of PUFB possessed relatively high degree of polymerization and low proportion of unreacted methylol groups. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009 相似文献
10.
The hot pressing operation is the final stage in MDF (medium density fiberboard) manufacture; the fiber mat is compressed and heated up to promote the cure of the resin. The aim of the investigations is to study the curing reactions of UF (Urea–Formaldehyde) resins as commonly used in the production of MDF, and to develop a simplified kinetic model. This investigation has combined Raman spectroscopy to study the reaction cure and 13C‐NMR for the quantitative and qualitative characterization of the liquid and still uncured resin. Raman spectroscopy was found very interesting for the study of the resin cure and permitted to obtain kinetic data as the basis for a simple empirical model, considering a homogeneous irreversible reaction of a single kind of methylol group and ureas with rate constants depending on their degree of substitution. Although these results can provide a better understanding of the composition and the cure of an UF resin, several issues remain open, such as the influence of the reversibility of the reactions taking place during the curing process as well as the possible formation of cyclic groups in the resin. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 5977–5987, 2006 相似文献
11.
8‐Hydroxyquinoline‐5‐sulfonic acid–thiourea–formaldehyde copolymer resins were synthesized through the condensation of 8‐hydroxyquinoline‐5‐sulfonic acid and thiourea with formaldehyde in the presence of hydrochloric acid as a catalyst and with various molar ratios of the reacting monomers. The resulting copolymers were characterized with UV‐visible, IR and 1H‐NMR spectral data, employed to determine the reactivity of monomers. The average molecular weights of these resins were determined with vapor pressure osmometry and conductometric titration in a nonaqueous medium. The chelation ion‐exchange properties were also studied with the batch equilibrium method. The resins were proved to be selective chelating ion‐exchange copolymers for certain metals. The chelation ion‐exchange properties of these copolymers were studied for Cu2+, Ni2+, Co2+, Pb2+, and Fe3+ ions. The study was carried out over a wide pH range and in media of various ionic strengths. The copolymers showed a higher selectivity for Fe3+ ions than for Cu2+, Ni2+, Co2+, and Pb2+ ions. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009 相似文献
12.
Terpolymer resins (8‐HQDF) were synthesized by the condensation of 8‐hydroxyquinoline (8‐HQ) and dithiooxamide (D) with formaldehyde (F) in the presence of acid catalyst and using varied molar ratios of reacting monomers. Terpolymer resins compositions have been determined on the basis of their elemental analysis and the number average molecular weights of these resins were determined by conductometric titration in non‐aqueous medium. Viscometric measurements in dimethyl formamide (DMF) have been carried out with a view to ascertain the characteristic functions and constants. The UV‐visible, FTIR, and proton nuclear magnetic resonance (H+ NMR) spectra were studied to elucidate the structure. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009 相似文献
13.
The effects of posttreatments of particleboard adhesive‐type urea–formaldehyde resins were studied. The resins were synthesized with formaldehyde/first urea (F/U1) mol ratios of 1.40, 1.60, 1.80, 2.10, and 2.40 and then the second urea was added to give a final formaldehyde/urea ratio of 1.15 in alkaline pH. The resins were posttreated at 60°C for up to 13.5 h and the 2.5‐h heat‐treated resin samples were stored at room temperature for up to 27 days. Resins sampled during the posttreatments were examined by 13C‐NMR and evaluated by bonding particleboards. In the posttreatments, hydroxymethyl groups on the polymeric resin components dissociated to formaldehyde and reacted with the second urea, and methylene and methylene–ether groups were formed from reactions involving the second urea. Methylene–diurea and urea groups bonded to UF polymers were identified. As a result, the viscosity of the resins initially decreased but later increased along with the cloudiness of the resins. Bond‐strength and formaldehyde‐emission values of particleboard varied with posttreatment variables as well as with the F/U1 mol ratios used in the resin syntheses. The results would be useful in optimizing resin synthesis and handling parameters. Various reaction mechanisms were considered. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 1896–1917, 2003 相似文献
14.
The curing reaction of a bisphenol A based benzoxazine [2,2‐bis(3,4‐dihydro‐3‐phenyl‐1,3‐benzoxazine) propane (Ba)] and bisoxazoline with a latent curing agent and the properties of the cured resins were investigated. With a latent curing agent, the ring‐opening reaction of the benzoxazine ring occurred more rapidly, and then the phenolic hydroxyl group generated by the ring‐opening reaction of the benzoxazine ring also reacted with the oxazoline ring more rapidly. The cure time of molten resins from Ba and bisoxazoline with a latent curing agent was reduced, and the cure temperature was lowered, in comparison with those of resins from Ba and bisoxazoline without a latent curing agent. The melt viscosity of molten resins from Ba and bisoxazoline with a latent curing agent was kept around 50 Pa s at 80°C even after 30 min, and molten resins from Ba and bisoxazoline with a latent curing agent showed good thermal stability below 80°C. However, above 170°C, the curing reaction of Ba with bisoxazoline with a latent curing agent proceeded rapidly. Cured resins from Ba and bisoxazoline with a latent curing agent showed good heat resistance, flame resistance, mechanical properties, and electrical insulation in comparison with cured resins from Ba and bisoxazoline without a latent curing agent. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 相似文献
15.
Guillaume Michaud Frédéric Simon Rémi Auvergne Stéphane Fouquay Sylvain Caillol 《应用聚合物科学杂志》2017,134(5)
This new study is a continuation of our previous work on thermocleavable nonisocyanate polyurethanes (NIPUs), but it is focused on crosslinked networks. Two systems are studied: the first system involves a dicyclocarbonate adduct with a PPO‐bicyclocarbonate and a triamine as crosslinker. The second system involves a tetracyclocarbonate DA adduct as crosslinker with the same PPO‐bicyclocarbonate and a difunctional amine. Firstly, Diels‐Alder adducts are synthesized and characterized. Then they are copolymerized to yield two types of cleavable polymer networks. The thermal behavior of synthesized polymers is fully characterized. Finally, by SEC, it was demonstrated that the obtained NIPU polymer chains are sliced up by rDA reaction. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44408. 相似文献
16.
Terpolymers 8‐hydroxyquinoline 5‐sulphonic acid–melamine–formaldehyde (8‐HQ5‐SAMF) were synthesized through the condensation of 8‐hydroxyquinoline 5‐sulfonic acid and melamine with formaldehyde in the presence of an acid catalyst. Four different terpolymers were synthesized with various molar proportions of the reacting monomers. The terpolymer resin compositions were determined on the basis of elemental analysis. The number‐average molecular weights of these resins were determined by conductometric titration in a nonaqueous medium; viscometric measurements in dimethyl sulfoxide were carried out to ascertain the characteristic functions and constants. Ultraviolet–visible, Fourier transform infrared, 1H‐NMR, and 13C‐NMR spectroscopy and thermogravimetric analysis were used to elucidate the structures. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 相似文献
17.
A new synthesis pattern of adamantoyl esters of cellulose (AdTMSC) is described. The process was approached by two steps. The first one consists in the obtaining of trimethylsilylcellulose (TMSC), by reacting cellulose in N,N‐dimethylacetamide/lithium chloride (DMA/LiCl) solution with chlorotrimethylsilane and hexamethyldisilazane. The AdTMSC was synthesized by reacting trimethylsilylcellulose with 1‐adamantanecarbonyl chloride, at 130°C. The obtained compounds were characterized by elemental analysis, 1H and 13C NMR, FTIR spectroscopy, thermogravimetry method, and X‐ray diffraction. From 1H NMR spectroscopy and elemental analyses, the degree of substitution (DS) of the cellulose derivatives was established. The AdTMSC is soluble in common organic solvent like chloroform, THF, and DMSO. As revealed by 13C NMR spectroscopy, a faster reaction takes place at the O (6)H group from AGU compared with O (2)H or O(3)H groups. Furthermore, other important properties were established by X‐ray diffraction and thermogravimetry method. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 105–112, 2006 相似文献
18.
A trifunctional epoxy containing oxyphenylene unit, triglycidyl of 4‐(4‐aminophenoxy)phenol (TGAPP) was synthesized and characterized. The chemical structure of TGAPP was confirmed with FTIR and 1H‐NMR. DSC analysis revealed that the reactivity of TGAPP with curing agent 4, 4′‐diaminodiphenylsulfone (DDS) was significantly lower than that of triglycidyl para‐aminophenol (TGPAP). Rheological analysis showed that the processing window of TGAPP/DDS was 20°C wider compared with that of TGPAP/DDS. The thermal and mechanical properties of cured TGAPP/DDS were investigated and compared with those of the cured TGPAP/DDS. Experimental results showed that, due to the introduction of oxyphenylene unit, the heat resistance and flexural strength were slightly reduced, while the tensile strength and impact strength were enhanced. SEM also confirmed that the introduction of oxyphenylene unit could enhance the toughness of the TGAPP/DDS as evident from ridge formation. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41878. 相似文献
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20.
Jan David Hübsch Martin Demleitner Simon Bard Philipp Berendes Volker Altstädt Christian Mittelstedt 《应用聚合物科学杂志》2023,140(1):e53263
Currently, the application of composites in aerospace parts exposed to higher temperatures and in aggressive media is still severely limited. To replace metal alloys, alternative resins systems with suitable long-term heat resistance are needed. In this study, the effect of the aviation hydraulic fluid Skydrol on the thermal and mechanical properties of a high-Tg, anhydride-cured epoxy resin in the unmodified and toughened state at elevated temperature is investigated. An aliphatic polyester diol was selected as an intrinsic toughener and its impact on the thermal, mechanical, and aging properties was determined. Experimental characterization of the aging effects is carried out with dynamic-mechanical characterization, infrared spectroscopy, and electron dispersion x-ray spectroscopy. In addition, the fracture toughness and the fatigue crack propagation behavior are determined. Initially, the toughened system shows an improved fracture toughness. Since oxidation is blocked by the Skydrol fluid only thermal degradation takes place as determined by the decrease in glass transition temperature Tg and network density. The thermal degradation leads to a tougher behavior, which is observed in both systems in static and dynamic mode with toughness decreasing with aging time again. 相似文献
