Thermosetting reactions: Thermochemical reactions of triallyl cyanurate and triallyl isocyanurate

Triallyl cyanurate (TAC) and triallyl isocyanurate (TAIC) are thermosetting monomers with interesting interrelations: Calorimetry and infrared spectrophotometry were used to investigate the influence of atmosphere and initiator on the thermal events. The large extents of reaction observed during polymerization of TAC and TAIC are attributed to the formation of intramolecular rings. The higher conversions obtained with TAC are attributed to the extra length and flexibility of its allyl groups. Isomerization of poly(TAC) to poly(TAIC) is described as a three-step process: depolymerization of poly(TAC) to form monomeric TAC, isomerization of TAC to TAIC by a Claisen rearrangement, and repolymerization of the TAIC to poly(TAIC).     

Copolymerization of alkyl acrylates with triallyl cyanurate: Kelen-Tüdös method applied for determining copolymerization reactivity ratios

The copolymerization of methyl acrylate (MA), ethyl acrylate (EA), straight-chain butyl acrylate (n-BA) and styrene (S) with triallyl cyanurate (TAC) has been studied in bulk at 343±1 K using benzoyl peroxide as initiator. The reactivity ratios of the monomers are determined by the Fineman-Ross (F-R) method and compared to those determined by the Kelen-Tüdös (K-T) method.     

Effect of triallyl cyanurate on the properties of bis-maleimide resins

This paper describes the improved processibility of 4,4'-bis-maleimidophenyl methane (BM) chain extended by 4,4'-diaminodiphenyl methane (DADPM) by coreaction with triallyl cyanurate (TAC). Curing of BM, chain-extended BM, and mixture of BM and DADPM (1 : 0.3 molar ratio) in the presence of 5, 10, 15, and 20% (w/w) of TAC was followed by differential scanning calorimetry (DSC) and thermal stability of cured resins was evaluated by thermogravimetric analysis. TAC had insignificant effect on char yield (at 800°C) of BM resin. Glass- and graphite fabric-reinforced composites were fabricated using chain-extended BM containing 10% TAC and methyl ethyl ketone (MEK) as solvent. Interlaminar shear strength was found to be 7620 psi for graphite fabric laminate containing 40% resin. Good retention of mechanical properties of laminates at 220°C up to 320 h was observed.     

Polymerization of alkyl acrylates and alkyl methacrylates with starch

A series of C₄-C₁₂ alkyl acrylates and methacrylates was polymerized with starch by irradiating starch–monomer mixtures with ⁶⁰Co. Homopolymers were extracted with cyclohexane. The amounts of insoluble versus soluble synthetic polymer in polymerization run with alkyl acrylates varied less with the chain length of the alkyl substuent than in the polymerizations run with alkyl acrylates varied less with the chain length of the alkyl substituent than in the polymerizations run with alkyl methacrylates; and the poly(alkyl acrylate) contents of cyclohexane-insoluble fractions were all in the 38–45% range. Synthetic polymer contents of the products from butyl, hexyl, and decyl methacrylates were also close to this range. Octyl and lauryl methacrylate, however, gave high conversions to cyclohexane-soluble poly(alkyl methacrylate) along with little or no unextractable synthetic polymer in the starch-containing fractions. Poly(lauryl methacrylate) could be rendered insoluble by incorporating a small amount of tetramethylene glycol dimethacrylate in the polymerization mixture. In a series of polymerizations run with hexyl acrylate and hexyl methacrylate, lower irradiation doses led to more cyclohexane-soluble polymer and less synthetic polymer in the starch-containing fractions. Enzymatic digestion of starch-soluble polymer and less synthetic polymer in the starch-containing fractions. Enzymatic digestion of starch-containing polymers gave synthetic polymer fractions that were largely insoluble in cyclohexane. Crosslinking is, therefore, probably taking place during these polymerizations; however, we could not eliminate the possibility that reduced solubility was caused by small amounts of residual carbohydrate in these polymer fractions. Ceric ammonium nitrate-initiated polymerizations of butyl acrylate, hexyl acrylate, and butyl methacrylate with starch gave cyclohexane-insoluble polymers that contained 33–39% synthetic polymer. The higher alkyl acrylates and methacrylates produced little or no polymer under these conditions. Starch-containing fractions were tested as absorbents for hydrocarbons. Products prepared from decyl acrylate and lauryl acryle acrylate absorbed about 9 g of isooctane per 1 g of polymer, whereas the lowrer alkyl monomers gave polymers with lower absorbency.     

Electron-beam-initiated grafting of triallyl cyanurate onto polyethylene: Structure and properties

Electron-beam (EB)-initiated grafting of triallyl cyanurate (TAC) onto polyethylene (PE) has been carried out over a range of radiation dose (2–20 Mrad) and concentrations of TAC (0.5–3 parts by weight). The grafting level, as determined from IR spectroscopy, is maximum at a 10 Mrad radiation does using 1 part TAC. With increasing TAC level at a 15 Mrad dose, the grafting level is higher only after 1.5 parts TAC. The gel content increases with radiation dose in the initial stages. X-ray studies indicate two peaks at 10.6–10.8° and 11.7–11.9° and the corresponding interplaner distances of 4.15 and 3.80 Å. With increase in radiation dose or TAC level, the crystallinity decreases in the initial stage and then increases. It shows a decreasing trend again at higher radiation dose. The interplanar distance or the interchain distance of the modified polymer does not change. However, the crystallite size increases initially and then decreases. The tensile properties are relatively insensitive to the variation of radiation dose because of the interplay of various factors. The dielectric loss, tan δ, shows a maximum at a 10 Mrad dose and minimum at 5 and 15 Mrad due to changes of polarity and the carrier mobility. © 1994 John Wiley & Sons, Inc.     

Surface properties of polyethylene grafted with triallyl cyanurate in the presence of an electron beam

The surface energy and thermodynamic work of adhesion of polyethylene grafted with triallyl cyanurate in the presence of an electron beam have been determined. The surface energy increased with the grafting level and with the irradiation dose up to 10 Mrad. A similar trend was observed with the work of adhesion. The changes in these surface properties were correlated with the concentration of the polar groups as measured by IR (infrared) spectroscopy and ESCA (electron spectroscopy for chemical analysis) studies.     

Copolymers of chosen alkyl methacrylates with N-phenylmaleimide and N-(4-halogenphenyl)maleimides: A UV-aging study

Homopolymers and copolymers of ethyl and butyl methacrylates with N-phenylmaleimide, N-(4-chlorophenyl)maleimide, and N-(4-bromophenyl)maleimide were synthesized by free-radical bulk polymerization with benzoyl peroxide as the initiator. The content of imide in the copolymers was about 5–10 or 7.5 wt %. The homopolymers and copolymers were irradiated with ultraviolet (UV) light in a climatic test chamber for various periods to study their aging behavior. After 100, 250, and 500 h, the structure, thermal stability, chemical resistance, and some physicomechanical properties were examined. The influence of UV radiation time on structure and the investigated properties of the homopolymers and copolymers were studied. The experimental results indicate that all investigated copolymers were resistant to UV radiation after 500 h. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 3244–3250, 2001     

Radiation crosslinking of bisphenol-a polycarbonate in the presence of bisphenol-a dimethacrylate and triallyl cyanurate

Summary Radiation crosslinking of bisphenol-A polycarbonate (PC) was carried out by the γ-irradiation of the polymeric films containing 5 and 2 wt % of bisphenol-A dimethacrylate (BPDMA) or triallyl cyanurate, respectively, as well as by the BPDMA grafting from acetone solution onto PC preirradiated in air. The modified samples were analyzed for the sol/gel content, and the dependences of gel fraction yield of crosslinked polymer on monomers concentration and absorbed dose were found. The radiation-chemical yields of crosslinking and degradation as well as gelation doses were determined for the modified PC. Molecular weights of the starting and irradiated pure PC were detemined by the GPC method, and radiation-chemical yield of PC degradation was calculated. It has been found essential difference in efficiency of PC crosslinking depending on monomers and doses used as well as on methods of modification. Effects of crosslinking agents distribution in the PC matrix and simultaneous processes of crosslinking and degradation in the polymer-monomer compositions on efficiency of PC crosslinking have been discussed. Received: 22 March 2000/Revised version: 26 June 2000/Accepted: 26 June 2000     

Structure and properties of poly(vinyl chloride)‐triallyl cyanurate plastisols

Triallyl cyanurate (TAC) has been used as a reactive plasticizer to promote the high‐temperature creep resistance of poly(vinyl chloride) (PVC) plastisols. The resultant crosslinked structure is characterized using gel content and swell ratio measurements as well as Fourier transform infrared spectroscopy. The crosslinking reaction was initiated using peroxide. The effect on the network structure of using a free radical scavenger in the formulation has also been studied. The gel yield and crosslink density in the gel increase with increasing TAC concentration in the plastisol, while the grafted PVC fraction and the residual unsaturation of TAC behave in the opposite way. Introduction of TAC into the plastisol promotes creep resistance at high temperatures, and the logarithmic creep rate was found to decrease linearly with increasing crosslink density.     

The glass transition of irradiated poly(methyl methacrylate) compositions incorporating triallyl cyanurate

A mechanical torsion pendulum has been used to observe changes in viscoelastic behavior resulting from modification of polymer structure. Crosslinking, with consequent increase in glass temperature, has been observed in irradiated poly(methyl methacrylate) compositions incorporating triallyl cyanurate, which confers partial protection against chain scission.     

Acid-dyeable acrylic fibres copolymerised with amino alkyl methacrylates for differential cross-dyeing

The equilibrium adsorption of acid dyes on acrylic fibres copolymerised with dimethyl amino ethyl methacrylate has been investigated. A typical characteristic of this type of fibre is its excellent stable dyeability over a wide pH range. This is due to the strong basicity of alkylamino groups in the copolymerised component, which makes it possible to dye the fibre thoroughly even in a weakly acidic dyebath using a normal dyeing processes of acrylic fibre with cationic dye. Consequently it is useful for differential cross-dyeing in a single dyebath.     

N-(p-Bromophenyl)maleimide and its copolymers with alkyl methacrylates

Copolymers of methyl, ethyl, butyl, pentyl, or octyl methacrylate with N-(p-bromophenyl)maleimide were synthesized by free-radical bulk polymerization using benzoyl peroxide as initiator. N-(p-bromophenyl)maleimide was prepared from maleic anhydride and p-bromoaniline in a two-step reaction. Thermal stability, chemical resistance, hardness, and Vicat softening point of the copolymers have been measured. The influence of N-(p-bromophenyl)maleimide content in the copolymers and the length of alkyl groups in methacrylates on their properties is discussed.     

Radical copolymerization of higher alkyl methacrylates with acrylic esters and amides in toluene: influence of monomer association on copolymer composition

A strong concentration effect was found in a course of copolymerization of higher N-alkylacrylamides with higher alkyl acrylates in toluene, where the fraction of amide functions in copolymers obtained at low degrees of conversion decreases significantly with an increase in total concentration of monomers in solution. It was established that the observed effect is independent of the structure of alkyl substitutes for both types of monomers. The data gathered with the aid of IR spectroscopy and computer modeling show that this concentration effect relates to the formation of amide associates in solution. The concentration effect was absent for the copolymerization of higher alkyl methacrylates and higher alkyl acrylates.     

Ultrasonic studies of solid poly(alkyl methacrylates)

The attenuation and velocity of ultrasonic longitudinal waves of frequencies 5–35 MHz in poly (methyl methacrylate), poly(ethyl methacrylate), poly (n-butyl methacylate) and poly(isobutyl methacrylate) between 233 and 363K are reported. The methyl and ethyl polymers showed evidence of a single relaxation process (associated with cooperative main chain and ester group motions), but the butyl polymers showed also a second relaxation at about 200–230K. This is associated with conformational rearrangement of the alkyl group, and the acoustic energetics are in line with theoretical predications for this process.The velocity data show the expected decreases due to the main glass transition (and cooperative processes) and to reduction of the intermolecular interaction force constant with increasing size of the alkyl group. Attempts to calculate an acoustic low temperature specific heat yielded values lower than expected from calorimetric observations, showing that the acoustic modes are capable of greater energy storage than is involved in the longitudinal perturbation, and/or that calculation based on a Debye T³ law are invalid for these glassy polymers.     

Ultraviolet irradiation of poly(alkyl acrylates) and poly(alkyl methacrylates)

Acrylic and methacrylic homopolymers containing different side groups were irradiated with ultraviolet light in the presence of air. The changes of molecular weight distributions of the irradiated polymers were analyzed by means of gel permeation chromatography (GPC), and the rates of chain scission and crosslinking were estimated. As the result of this study, it was found that chain scission takes place more easily in polyalkyl methacrylates than in polyalkyl acrylates.     

Synthesis and spectral investigation of alkyl methacrylates with halogenated carbazolyl pendant groups for photonics applications

The alkyl methacrylates with halogenated carbazolyl pendant groups were prepared, and the analysis of their absorption and emission spectra showed that the polymers containing monohalogenatged carbazole rings were capable of exhibiting a high singlet‐triplet (S‐T) conversion. The reasons that mainly triplet excitons could be observed in such polymers and additional bands appearance in the spectra of the polymers with dihalogenated carbazole rings are discussed. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 1650–1656, 2002; DOI 10.1002/app.10469     

A study of the thermal and mechanical properties of electron beam irradiated HDPE/EPDM blends in the presence of triallyl cyanurate

The enhancing effects of cross-linking by the addition of 1, 3, and 5 wt% of triallyl cyanurate (TAC) to blends containing 80 wt% of high-density polyethylene (HDPE) and 20 wt% of ethylene–propylene diene monomer (EPDM) during electron beam irradiation were investigated. More specifically, the thermal and mechanical properties were studied as a function of the electron beam irradiation dose and an amount of the cross-linking agent, such as triallyl cyanurate (TAC). The results showed that the values of the gel content, thermal stability, tensile properties, impact strength, and rheology increased with increasing irradiation dose up to 150 kGy. For higher doses, the values decreased. Addition of the cross-linking agent to the HDPE/EPDM blends showed an enhanced cross-linking effect of various properties during electron beam irradiation. The addition of 3 wt% of TAC led to the highest thermal and mechanical properties. An irradiation dose of 150 kGy with the addition of 3 wt% TAC was the optimal condition to obtain blends with the best properties.     

Copolymers from oligosiloxane methacrylates as a plasticizer-free membrane matrix for ion-selective sensors

Cross-linked copolymers have been prepared by free-radical photoinitiated polymerization of dimethacryloxypropyl oligodimethylsiloxane with monomethacryloxypropyl oligodimethylsiloxane and the polar comonomers cyanomethyl methacrylate, cyanoethyl methacrylate, trifluoroethyl methacrylate and hexafluoroisopropyl acrylate, respectively, for use as a plasticizer-free membrane matrix for ion-selective sensors. The polymerization course in dependence on the composition of the monomer mixture and on the presence of ionophore and ion conducting salt as well as chloroform as solvating agent was studied by means of differential scanning calorimetry. The resulting copolymer membranes were characterized concerning the content of residual CC double bonds and sol as well as their thermo-mechanical and electroanalytical properties. The thermal and mechanical properties of these copolymer membranes exhibiting a heterogeneous network structure are adjustable in a wide range by variation of the ratio of the monomers used. In comparison with the most widely used poly(vinyl chloride) based membranes containing a plasticizer, the K⁺ and Ca²⁺ selective sensor membranes based on the new copolymers exhibit analogous or even better electro-analytical properties and above all, a distinctly longer lifetime.