Water-soluble sulfonated amino-formaldehyde resins. I. Melamine resins,synthesis

The procedure for preparing sulfonated melamine formaldehyde resins and the factors affecting it were investigated. A four-step procedure was developed which results in reproducible watersoluble stable resins. The reactions that take place in the four steps are hydroxymethylation, sulfonation of the methylolmelamine intermediate, low pH condensation, and high pH rearrangement reaction. The reaction and the resins produced were found to be very sensitive to pH, temperature, sulfite/melamine, and formaldehyde/melamine molar ratios. The apparent molecular weight distribution of selected samples was also determined.     

Functionalized allyl resins. I. Photosensitivity of partially cinnamoylated allyl resins

The preparation of photosensitive allyl resins is described. The introduction of cinnamoyl groups into allyl resins is attempted for imparting successfully photosensitive functionality. Thus, the photosensitivity of cinnamoylated poly(allyl benzoate) was first examined in detail as a model photoreaction of cinnamoylated allyl resins. Cinnamoylated poly(diallyl phthalate) was then UV-irradiated to yield crosslinked resin, and its photosensitivity was compared with that of other allyl resins. The highest photosensitivity was observed for cinnamoylated poly(diallyl phthalate), although the mobility of the main polymer chain was considered to be lowest; this may be ascribed to the function of phthaloyl groups as photosensitizers.     

Pyrolysis of phenolic resins. IV.

Thermoset resins were made from benzene, naphthalene, phenanthrene, anthracene, or pyrene by condensation with p-xylylene dichloride in presence of stannic chloride. The extent of reaction, consequently the crosslink density, was controlled by measurement of the HCl evolved. The absence of oxidation was confirmed by infrared spectroscopy. On pyrolysis at 500, 1000, and 1200°C. in vacuo (after Madorsky) it was found that the yield of char was directly related to the number fraction of carbon atoms in the aromatic nucleus used. Benzene was anomalous, and all resins gave lower char yields than standard phenol formaldehyde resins.     

Epoxy resins based on aromatic glycidylamines. V. Shelf life of TGDDM-based epoxy resins

The effect of aging on resin composition was investigated as a part of a study concerned with the evaluation of epoxies containing N, N, N′, N′-tetraglycidyl-4,4′-diaminodiphenylmethane (TGDDM). Long-term stability of three different epoxy resins based on TGDDM and their mixtures with 4,4′-diaminodiphenylsulfone (DDS) was followed at 23 ± 2°C at a relative humidity ranging from 45% to 55%, by means of GPC and HPLC; short-term stability of the resins was evaluated at 125°C.     

Core-shell particles designed for toughening the epoxy resins. II. Core-shell-particle-toughened epoxy resins

The diglycidyl ether of bisphenol A–m-phenylene diamine (DGEBA–MPDA) epoxy resin was toughened with various sizes and amounts of reactive core-shell particles (CSP) with butyl acrylate (BA) as a core and methyl methacrylate (MMA) copolymerized with various concentration of glycidyl methacrylate (GMA) as a shell. Ethylene glycol dimethacrylate (EGDMA) was used to crosslink either core or shell. Among the variables of incorporated CSP indicated above, the optimal design was to obtain the maximum plastic flow of epoxy matrix surrounding the cavitated CSP during the fracture test. It could be achieved by maximizing the content of GMA in a shell-crosslinked CSP, the particle size, and the content of CSP in the epoxy resin without causing the large-scale coagulations. The incorporation of reactive CSP could also accelerate the curing reaction of epoxy resins. Besides, it was able to increase the glass transition temperature of epoxy resins if the particle size ≤0.25 μm and the dispersion was globally uniform. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 70: 2313–2322, 1998     

Quantitative 13C n.m.r. characterization of aqueous formaldehyde resins: 1. Phenol-formaldehyde resins

Phenol-formaldehyde (PF) resins which had experienced a variety of reaction conditions and/or ageing conditions were quantitatively characterized by ¹³C n.m.r. Under the specific conditions of this study, the phenol para position was favoured for reaction over the ortho position on a per site basis, particularly for condensation reactions. Increasing the reaction temperature from 23°C (14 days reaction) to 80°C (3 h reaction) did not alter the type of resin structure. Ageing PF resins resulted in extensive condensation and a drastic reduction in para-substituted methylol and hemiformal groups. This apparently contributes to a sharp reduction in the reactivity of these resins for reactions requiring methylol substituents on the ring.     

Cure of polyester resins. II

The copolymerization reaction between unsaturated polyesters and styrene has been studied by a torsional pendulum. The accuracy of the dynamic-mechanical measurements obtained is discussed briefly, and the results are compared with those of previous work on the change of hardness during cure.     

Cure of polyester resins. I

The application of physical test methods to studying the crosslinking of unsaturated polyesters is reviewed. Experimental work on changes of hardness and electrical resistivity is described and it is shown that these are not mutually related, due to continual mobility of ionic conditions after the resin network is immobilized by gelation.     

Rheology of unsaturated polyester resins. II. Thickening behavior of unsaturated polyester and vinyl ester resins

The rheological properties of mixtures of unsaturated polyester resin and viscosity thickener were determined as thickening progressed. Two commercially available resins were used: (1) general purpose unsaturated polyester resin (Ashland Chemical, Aropol 7030), and (2) vinyl ester resin (Dow Chemical, XD-7608.05). As thickening agent, a magnesium oxide (MgO) paste dispersed in styrene monomer was used. No fillers, pigments, or other additives were used. During thickening, the following measurements were also made: (1) acid number by titration and (2) molecular weights by gel permeation chromatography (GPC). For the Ashland Chemical polyester resin, it was found that, over a period of 300 h, the titration method indicated that the number-average molecular weight (M _n) increased by a factor of 2 and the weight-average molecular weight (M _w) increased by a factor of 3. The GPC measurements, however, showed that M _n increased very little whereas M _w increased by a factor of about 2. Over the same period, the viscosity of the Ashland Chemical polyester resin increased from 0.9 N·s/m² (9 P) to 10⁴ N·s/m² (10⁵ P), and the viscosity of the Dow Chemical vinyl ester resin increased from 0.7 N·s/m² (7 P) to 2 × 10³ N·s/m² (2 × 10⁴ P). Such a large increase in viscosity cannot be explained by the existing molecular theory, in view of the fact that the molecular weights increased relatively little. We speculate that the exceedingly large increase in viscosity during thickening is attributable primarily to ionic associations between the carboxylic anions and the magnesium ions, rather than to the formation of chain branching suggested in the literature. It was found further that mixtures of polyester resins and viscosity thickener exhibit normal stress effects, increasing with thickening time and following the behavior of a second-order fluid when the first normal stress difference was plotted against shear rate. Interestingly enough, however, plots of first normal stress difference vs. shear stress yield a correlation which becomes independent of thickening time. An explanation is offered to the correlation obtained.     

Molecular weight distribution in alkyd resins. Part III. Presence of microgel in alkyd resins

Alkyd resins which have the same overall chemical composition and the same degree of polymerization have been prepared from synthetic mixtures of mono-, di-, and triglycerides of linoleic acid, glycerol, and phthalic anhydride. The properties of these resins differend significantly. Microgel particles are present in all resins, but the quantity and size of the gel particules is a function of the glyceride composition. The concept of microgel is used to explain the solution and film forming properties of these resins. Examination of a range of commercially available alkyd resins has shown that microgel particles are present where the functionality is greater than two.     

Synthetic resins,IV. Preparation and characterization of resins prepared from hydroxyacetophenone

New resins have been synthesized from o-hydroxyacetophenone by reaction with substituted aromatic compounds and formaldehyde in the presence of various acids and bases as catalyst following two different techniques. The polymer samples are characterized by IR spectra. The solution, thermal, and chemical properties of the resins are investigated. The solubility parameters of the resins calculated according to the investigations of Small agree well with the experimental values. The resins are found to be fairly thermostable and the energy of activation is evaluated from TG curve by applying (i) Freeman-Anderson method and (ii) Broido method.     

Studies in the molecular weight distribution of epoxide resins. II. Chain branching in epoxide resins

The extent of side chain branching in epoxide resins based on bisphenol A has been determined by nuclear magnetic resonance spectrometry. The results indicate that for the resins studied in this paper, the extent of branching is very small. The number of branch points varies between 0.09 to 0.06 per molecule for epoxide resins whose number-average molecular weight lies between 1500 and 4000.     

Studies in the molecular weight distribution of epoxide resins. I. Gel permeation chromatography of epoxide resins

The molecular weight distributions as measured by gel permeation chromatography of solid epoxide resins made by the direct addition of epichlorohydrin to bisphenol A (the “taffy” process) and by the reaction of low molecular weight liquid epoxide resins whose main constituent is the diglycidyl ether of bisphenol A with bisphenol A (the “advancement” process) have been compared with the theoretical distribution calculated by the application of Flory statistics. The model used for predicting the molecular weight distribution has been shown to be too simple to describe the real size distribution of these resins. For resins prepared by the “taffy” process, incompleteness of reaction, the presence of monofunctional epoxides, and the possibility of branching reactions through the epoxide–hydroxyl reaction lead to a distribution that more nearly resembles one calculated for a resin having a higher epoxide value than that actually measured. In the case of resins prepared by the “advancement” process, the presence of small amounts of the higher oligomeric diepoxides and monofunctional epoxides in the starting material used for the synthesis lead to complex molecular weight distributions that are not easy to deduce theoretically. The experimentally determined molecular weight distributions for the higher molecular weight epoxide resins (epoxide value <2 eq/kg) made by the “advancement” process resemble more nearly those calculated for resins having lower epoxide values than those actually measured.     

Copper-selective chelating resins. I. Batch extractions

Eleven novel metal ion-chelating resins based upon porous poly(glycidyl methacrylate-co-ethylene glycol dimethacrylate) have been prepared by direct reaction of the polymer with ligands containing an amino group. Those species involving a 2-pyridyl-2-imidazole and a 2-aminomethylpyridine proved to be the most interesting and, for comparison, polystyrene resin analogues of these were also produced. As expected from the literature, the above pyridine-containing ligands remained effective for the extraction of Cu²⁺ down to pH 2. Despite having superficially similar overall physical characteristics (particle size, surface area, porosity) the glycidyl methacrylate-based resins showed remarkably enhanced kinetic behaviour in the batch extraction of base metal ions such as Cu²⁺, with an extraction half life as low as ∼ 8 minutes, four times faster than a polystyrene-based analogue.In addition the glycidyl methacrylate-based resins displayed superior selectivity in the extraction of particular metal ions from feed liquors containing a mixture of metal ions. The most remarkable separation discovered was that of Cu²⁺ from Zn²⁺ where the glycidyl methacrylate-based species with the above ligands achieved essentially quantitative separation of Cu²⁺, even with Zn²⁺ present in 250 times excess. Extracted metal ions were rapidly and quantitatively eluted from these resins with 2 M H₂SO₄, and in the case of Cu²⁺ an acid strength of only 0.25 M was adequate.     

Structure-property relationships in PMR-type polyimide resins: 1. Novel anthraquinone-based PMR resins

Novel aromatic polyimides prepared via the polymerization of monomeric reactants (PMR) approach and incorporating anthraquinone diamines in the main chain have been characterized. Imidization and crosslinking reaction profiles have been delineated by d.m.t.a. and the high-temperature mechanical and thermal properties of the thermoset resins examined. Elevated glass transition temperatures (> 300°C) are apparent in some resins while impairment of mechanical integrity is not evident below 450°C. All resins show good thermal and thermo-oxidative stability.     

Thermal degradation of phenolic resins. V

The effect of varying the nature of crosslinks in phenolic resins has bee studied with the use of resins made from phenol, p-cresol, and bisphenol A. Thermal analysis showed that the methylene bridge was stronger under nonoxidative conditions than the isopropylidene linkage. The result is somewhat affected by the degree of crosslinking.     

Polyurethane-crosslinked epoxy resins. I. Mechanical behavior

Polyurethane (PU) prepolymers based on poly(butylene adipate) (PBA) and poly(oxytetramethylene) (PTMO) polyols were employed as a crosslinking agent to the diglycidyl ether of bisphenol A (DGEBA). Then the DGEBA was cured with a tertiary amine catalyst to form PU-crosslinked DGEBA. The tensile strength of both the PU(PBA)-crosslinked DGEBA and PU(PTMO)-crosslinked DGEBA systems increased to a maximum value with increasing PU content in the system and then decreased with further increasing PU content. Izod impact property of these PU-crosslinked DGEBA indicated that the PU(PBA)-crosslinked DGEBA had much more significant improvement than the PU(PTMO)-crosslinked DGEBA. On the contrary, the fracture energy (G_{1 C} value) of the resultant PU-crosslinked DGEBA showed that the PU(PTMO)-crosslinked DGEBA had much higher G_{1 C} values than the PU(PBA)-crosslinked DGEBA.     

Copper-selective chelating resins. II. Column extractions

Two chelating resins based on poly(glycidylmethacrylate-co-ethyleneglycol dimethacrylate) and two based on poly(styrene-co-divinylbenzene) have been used in small-scale column extractions of Cu(II) from sulphate solutions containing 1.0 mg l⁻¹ of metal ion at pH 5. Two of the resins bearing 2-aminomethylpyridine residues with saturation capacities up to ∼ 15 g Cu(II) l⁻¹ resin showed sharp breakthrough profiles and rapid exchange kinetics. The other two with higher ligand loading displayed shallow profiles and did not reach saturation capacity, indicating a significant proportion of the ligand groups to be inaccessible under the conditions employed. For a column of 10 ml bed volume, increasing the flow rate of the feed solution from 1 ml min⁻¹ progressively to 30 ml min⁻¹, using one of the more efficient resins, showed that above a rate of ∼ 5 ml min⁻¹ the bulk movement of ions through the column was too fast for all the resin-bound ligands to be accessed. As a result breakthrough moved to lower volumes and the working capacity dropped. No difference was found in the elution of all four resins with 1 M H₂SO₄ at a flow rate of 1 ml min⁻¹. In all cases Cu(II) was rapidly and efficiently eluted from the column.The selectivity properties of the two efficient resins in extracting Cu(II) ions from a solution containing a large excess of Zn(II) ions were also investigated. The effect of a 250-fold excess of Zn(II) proved negligible in both cases, and Cu(II) was rapidly and selectively extracted with a separation factor of ∼ 900: 1 in the case of the polystyrene-based resin, and ∼ 500: 1 in the case of the methacrylate-based species.In terms of kinetic performance and metal ion selectivity (in both loading and elution) the results of the batch extraction experiments were confirmed in these column tests, hence proving the predictive value of careful batch testing. On considering kinetic factors, capacity factors and metal ion selectivity factors, a resin carrying a 2-aminomethylpyridine group attached to a polymethacrylate backbone proved to be the optimum one.     

Water-soluble sulfonated phenolic resins. I. Synthesis

A new water-soluble sulfonated phenolic resin as a water reducer in concrete was prepared in this study. It was synthesized from formaldehyde, phenol, and NaHSO₃ through a four step reaction procedure. The structure of resin was determined through analyses of IR and NMR spectra. The influence of reaction conditions on the properties of synthesized products was also examined and discussed. © 1995 John Wiley & Sons, Inc.