Acidities and catalytic activities of persulfonated poly(styrene-co-divinylbenzene) ion-exchange resins

A series of macroporous sulfonated poly(styrene-co-divinylbenzene) ion-exchange resins with varying levels of sulfonation have been prepared. The acidities of these resins have been measured calorimetrically by ammonia sorption. Catalytic activities have been measured in two liquid-phase reactions: the dehydration of 1-hexanol under flow conditions and the hydration of propene as a batch process. The molar enthalpies of ammonia sorption show that the strength of the acid sites increases as the level of sulfonation is increased; catalytic activities follow the same trend. The most active resins are those that have been sulfonated at levels above one sulfonic acid group per aromatic ring (persulfonated). These persulfonated resins also show higher thermal stabilities than conventional resins (sulfonated at just below one acid group per aromatic ring).     

Formaldehyde Resins Bearing Diaminodiphenylmethane Groups: Synthesis,Characterization and Properties

Summary: Novel formaldehyde resins bearing diaminodiphenylmethane groups were synthesized by the polymerization of a mixture of diaminodiphenylmethane (DDM), cyclohexanone (CHx) and o‐cresol (o‐Cz) with formaldehyde (FA) in the presence of an acid catalyst (HCl). The resins obtained were characterized by spectral, elemental and thermal analysis and used as a hardener for epoxy resins. The curing and temperature behavior of these epoxy resin/formaldehyde systems were investigated using differential scanning calorimetry and thermogravimetry techniques. The resins had good thermal stability and the activation energies of degradation reactions had values between 70–98 kJ · mol^?1.

The curing reaction of epoxy resins with the DDM/CHx/o‐Cz/formaldehyde resins.     

Synthesis and characterization of side-chain liquid crystalline polymers and oriented elastomers containing terminal perfluorocarbon chains

Several novel chiral side-chain liquid crystalline (LC) polysiloxane resins containing epoxy groups and mesogenic components have been graft copolymerized by a one-step hydrosilylation reaction with poly(methylhydrogeno)siloxane, an epoxy monomer 2-(allyloxymethyl)oxirane, and chiral fluorinated liquid-crystalline monomers 4′-(4-(allyloxy)benzoyloxy)biphenyl-4-yl 6-(perfluorooctanoyloxy)hexahydrofuro[3,2-b]furan-3-yl adipate and 4′-(4-(undec-10-enoyloxy)benzoyloxy)biphenyl-4-yl 6-(perfluorooctanoyloxy)hexahydrofuro[3,2-b]furan-3-yl adipate. The synthesized epoxy resins are cured using 4,4′-diaminodiphenyl-methane in mesophase state under a magnetic field to obtain crosslinked oriented elastomers. The chemical structures, LC properties and surface morphology of the monomers, the resins and the liquid crystalline elastomers (LCEs) are characterized by use of various experimental techniques such as FTIR, ¹H NMR, EA, TGA, DSC, POM, and X-ray measurements. The mesomorphic properties of the synthesized resins and corresponding oriented elastomers are influenced by the terminal perfluorocarbon chains components effectively. The resins show chiral nematic and chiral smectic C phases (), and are frozen in their corresponding oriented elastomers. The LC phases are verified by X-ray measurements, and the orientational order parameters of the oriented LCEs are calculated as well.     

Synthesis,Characterization, and Properties of Multifunctional Epoxy Maleimide Resins

Summary: Novel multifunctional formaldehyde resins bearing diaminodiphenylmethane groups are synthesized by the polymerization of a mixture of diaminodiphenylmethane (DDM), o‐cresol (o‐Cz), and cyclohexanone (CH_x) with formaldehyde (FA) (at a molar ratio of monomers/formaldehyde, 1/1), in the presence of acid catalyst (HCl). The obtained resins are epoxidated with a large excess of epichlorohydrin and transformed into multifunctional epoxy resins. The multifunctional epoxy maleimide resins are obtained by reaction of the epoxy resins with carboxy phenyl maleimide in the presence of triethylamine as a catalyst. The resultant resins are characterized by IR and NMR spectroscopy, elemental, and thermal analysis. The curing and thermal behavior of these epoxy maleimide resin/DDM systems are investigated using differential scanning calorimetry (DSC) and thermogravimetry (TG) techniques. The activation energies of the curing reactions are situated in the range of 53–90 kJ · mol^?1. The cured products have good thermal properties, and activation energies of degradation reactions have values between 42–74 kJ · mol^?1.

The curing reaction of multifunctional epoxy maleimide resins with DDM.     

Sorption equilibrium of Cr(VI) ions by strong base anion exchangers with pyridine structures

Chromate sorption on pyridine strong base anion exchangers with different functional groups (methyl, ethyl, and butyl groups), at the quaternary nitrogen atoms, was studied as a function of various initial concentrations (100–1500 mg Cr/L) and counterion type. The studied resins in the Cl^?[ form have higher Cr(VI)‐retention capacities than those in the SO form. The pyridine strong base anion exchangers showed a selectivity reversal for the sulfate and chromate anions compared to that of the commercial resins. The alkyl substituent length of the quaternary nitrogen atoms exerted a substantial influence on the Cr(VI)‐retention capacity values for the resins in the Cl^? form; the chromate anions preferred resins with methyl functional groups, that is, resins with a greater hydrophilic structure. For the resins in the SO form the length of the substituent at the quaternary nitrogen atom had only a negligible influence on their Cr(VI)‐retention values. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 1957–1963, 2004     

13C-NMR studies of commercial and partially self-condensed hexakis(methoxymethyl)melamine (HMMM) resins

¹³C-nuclear magnetic resonance (NMR) spectroscopy was employed to study the linkages in three commercial fully methylocated melamine-formaldehyde (HMMM) resins and their partially self-condensed resins by acid catalysis, in order to probe the structures linking melamine units. Distortionless enhancement by polarization transfer (DEPT) experiments show that the partially self-condensed resins contain both methylene ether and methylene linkages between melamine units. The extent of these linkages were estimated by quantitative ¹³C-NMR spectroscopy using inverse gated decoupling techniques. The results show that the ratios of methylene ether and methylene linkages to the triazine moiety vary from resin to resin. © 1996 John Wiley & Sons, Inc.     

An ion-exchange process with thermal regeneration XV treatment of sulphite-deoxygenated feedwaters

Under typical plant operating conditions, thermal desalination capacities (TDC) of up to 0.26 meq/ml have been observed for a new range of thermally regenerably resins. The resins are chemically stable when used to desalinate waters containing small amounts of sulphite. With the new “Sirother”¹ resins, deoxygenation by the sulphite technique is a permissible pretreatment option, albeit with some restrictions on the range of feasible desalination flow-schemes.     

Synthesis and properties of silicon‐containing arylacetylene resins with polyhedral oligomeric silsesquioxane

A series of silicon‐containing arylacetylene resins containing polyhedral oligomeric silsesquioxane (PS resins) were synthesized by the hydrosilylation reaction between poly(dimethylsilyleneethynylenephenyleneethynylene) (PMSEPE) and octakis(dimethylsiloxy)octasilsesquoixane ( ) in the presence of a platinum catalyst (Pt‐dvs). The chemical structures and properties of PS resins were characterized by Fourier transform infrared spectroscopy, nuclear magnetic resonance spectroscopy, rheological analysis, differential scanning calorimetry, dielectric measurement, thermogravimetric analysis, and scanning electron microscopy. The results show that PS resins can be crosslinked to form thermosets at temperatures less than 260°C. With the increment of , the dielectric constants of the thermosets gradually decrease from 2.91 to 2.73. The thermooxidative stabilities of PMSEPE thermosets are obviously improved with the incorporation of . POLYM. ENG. SCI., 55:316–321, 2015. © 2014 Society of Plastics Engineers     

Cure kinetics of cyanate ester resin using microencapsulated dibutyltin dilaurate as catalyst

Dibutyltin dilaurate (DBTDL) catalyst-filled microcapsules (MCs) were used to catalyze the reaction of thermosetting cyanate ester (CE) resins. Dynamic differential scanning calorimetry (DSC) experiments were performed at multiple heating rates (β) to investigate the effects of the MC content (0.125, 0.25, and 0.5 %) on the cure kinetics of CE resins. The kinetic parameters of CE/MC systems, including activation energy (E _a), preexponential factor (A), and reaction order (n), were analyzed using the Flynn–Wall–Ozawa method, Kissinger method, Crane method, Ozawa isoconversional method, and Coats–Redfern method. The results indicate that, as the MC content increases, the reaction temperature of CE/MC system gradually shifts to low temperature owing to the increase of the DBTDL catalyst released from MCs under heating conditions. Compared to the unencapsulated DBTDL, the encapsulated DBTDL can decrease the E _a, A, and the reaction rate constant of CE resins due to the gradual release of DBTDL from MCs and the homogeneous dispersion of the released DBTDL in CE resins. The E _a, A, and the reaction rate constant of CE/MC systems are effectively adjusted by the MC content and heating process. The reaction orders for all CE/MC systems are close to 1. The reaction model of CE/MCs is considered as a two-dimensional nucleation (A ₂).     

Synthesis,characterization, and metal‐ion uptake studies of chelating resins derived from formaldehyde‐condensed azodyes of aniline and 4,4′‐diaminodiphenylmethane coupled with phenol/resorcinol

The diazonium salts of aniline and 4,4′‐diaminodiphenylmethane coupled with phenol and resorcinol were condensed with formaldehyde in alkaline media to yield polymeric resins. These polymers were found to readily react with metal ions like Cu²⁺ and UO, forming polychelates. The azodyes, resins, and polychelates were characterized by several instrumental techniques such as elemental analysis, FTIR, ¹H‐NMR, GPC, XRD, TG–DTG, and DSC studies. The chelating capacity of the resins toward Cu²⁺ and UO ions was studied by spectrophotometry. The extent of metal loading of the resins was studied by varying the time of contact, metal‐ion concentration, and pH of the reaction medium. The alkali and alkaline earth metal ions had little effect on the metal‐ion uptake behavior of the resins. The resin derived from the azodye of 4,4′‐diaminodiphenylmethane was found to be more efficient in removing the metal ions from solution than were the resins from aniline. The optimum conditions for effective separation of Cu²⁺ from UO were determined. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 3128–3141, 2000     

Rheology Study of Sugar Cane Bagasse Lignin-Added Phenol–Formaldehyde Adhesives

The rheological properties of sugar cane bagasse lignin–phenol formaldehyde (PF) (30% lignin – PF) resins were studied using oscillation tests. The bagasse lignin was introduced in the classic adhesive formulation in order to supply a part of PF. Rheological qualities of optimal lignin–PF (30% lignin – PF) resins and commercial PF resin were assessed by using a rotary rheometer (ARES). Dynamic rheological measurements, performed at low strain in the linear range, are useful to characterize the network properties of resins.

The results obtained showed that the time sweep indicates excellent structural stability of optimal lignin–PF (30% lignin–PF) resins and commercial PF resin. The elastic modulus is greater than the viscous one showing a remarkable elastic character of the resins, and the performed frequency sweeps show a typical spectrum of a “weak gels” structure. The time dependence at 125°C shows that the optimum cure time is 7.5 min.     

Two-Stage Moisture Absorption Behavior and Hydrolysis of Cured Dicyanate Ester Resins

A two-stage moisture absorption behavior for the cured 4,4-dicyanato 1,1-diphenolethane (DCDPE) resins was found when they were exposed to 60C/100%RH environment. The first stage followed the Fickian diffusion, whereas the secondary stage was a swelling-controlled diffusion in that the diffusion coefficient was decreased with time. With increasing the sample thickness, the two-stage absorption behavior became less discernible. After long term exposure to moisture, DCDPE resins were prone to hydrolysis to form voids in the networks. When chromium acetylacetonate (Cr(acac)₃) was incorporated in the resin formulations as a curing accelerator, it also accelerated the hydrolysis, facilitating the formation of voids.     

Enhancement of Epoxy Resin/Copper Heterojunction by Introduction of Sulfur‐Containing Polymers

Summary: Epoxy resins are widely used in electronics and electric industries because of their superior properties. In recent years, excellent bonding properties for metals (e.g., copper, gold, aluminium, silver, etc.), to which it is hard to adhere, have become desirable for epoxy resins in the electric and electronics industrial fields. However, epoxy resins have only poor bonding strength to the metals. In order to increase the heterojunction strength between epoxy resins and copper, the introduction of sulfur, providing strong interactions with metals, was investigated. TDP polyester and MPS polythioesters containing sulfur moieties were employed as the sulfur‐containing modifiers for the epoxy resin. Epoxy resins containing a modifier (5–20 phr) and a curing agent were cured between copper plates at 120 °C for 2 h and at 170 °C for 2 h. The effect of the added modifiers was evaluated by the lap‐shear testing method. It could be demonstrated that MPS polythioesters have a beneficial effect on the enhancement of the epoxy resin/copper heterojunction. The most effective example was the addition of 20 phr of the MPS_7 polythioester, which increased the lap shear strength from 5.7 to 17 MPa.

Improvement of lap shear strengths of adhesive copper joints by sulfur‐containing modifiers.     

Magic Angle Spinning-Cross Polarization 13C NMR of crosslinked unsaturated polyester resins

Summary Magic Angle Spinning-Cross Polarization (MAS-CP) ¹³C NMR spectra of four different unsatured resins reticulated with styrene have been measured.Styrene crosslinks may be constituted essentially by dyads or may consist in (styrene) microdomains (n2), depending mainly upon the molar ratio of maleic acid residues in the original unsaturated polyester to styrene.Also in the case of solid unsaturated resins the MAS-CP ¹³CNMR technique promises to allow structural insights only very difficultly obtainable by more classical indirect means.     

Novel Phenol‐Formaldehyde Resins, 2. Resols Prepared Using Reactive Solvents

New results on the method of preparation of phenol‐formaldehyde resins from phenol and multihydroxymethyl derivatives of some ketones are presented. The latter, known as the reactive solvents of melamine, were prepared by reacting acetone and methyl ethyl ketone with excess of formaldehyde. A novel group of resins of resol type has been obtained. The structure of products is discussed and compared to that of classical resols. The fragments of ketones have been found incorporated into the structure of resins.

Temperature dependence of viscosity of a classical resol and of the resols modified with reactive solvents.     

Gamma Ray Irradiation‐Initiated Copolymerization of a Binary Casting System Involving DPBMIn and Vinylpyrrolidone

Summary: When initiated by gamma ray irradiation, a series of homogenous binary casting systems composed of bismaleimide oligomer DPBMI_n with different chain length and reactive solvent vinylpyrrolidone were capable of copolymerization via radical mechanism to form copolymer resins with crosslinked network. Postcuring was performed by thermal treatment subsequent to gamma ray irradiation. The influences of irradiation dose, postcure, DPBMI_n content, and chain length of DPBMI_n on mechanical properties, water uptake, and thermal property of copolymer resins were investigated in details. Fracture morphologies of copolymer resins based on different DPBMI_n were studied by SEM.

SEM images of the copolymer resins.     

Bio‐Based Nanocomposites from Corn Oil and Functionalized Organoclay Prepared by Cationic Polymerization

A reactive organic montmorillonite clay (VMMT), modified with (4‐vinylbenzyl) triethylammonium cations, has been prepared and used as a nanofiller to reinforce a corn‐oil‐based polymer resin. The polymer resin was prepared by the cationic polymerization of conjugated corn oil, styrene and divinylbenzene, using boron trifluoride diethyl etherate modified with Norway fish oil as the initiator. The results indicate that the VMMT is intercalated in the corn‐oil‐based polymer resins. When compared with the pure polymers, these novel nanocomposites reinforced with 2 to 3 wt.‐% VMMT exhibit significant improvements in modulus, strength, strain and toughness. Furthermore, incorporating VMMT into the corn‐oil‐based polymer matrix also leads to improved thermal stability of the nanocomposites over the pure resins of up to 400 °C.