Characterization of unsaturated polyester resin cured with styrene

In this work, the curing kinetic of an unsaturated polyester resin, mixed with styrene as curing agent, was studied by means of diffential scanning calorimetry (DSC) and infrared (IR) spectroscopy. Investigations were made in situ during curing and post-curing periods. The enthalpy (ΔH_cop) characterizing the styrene homopolymerization and its copolymerization with the polyester chains was determined from isothermal DSC investigations. The residual enthalpy (ΔH_res) was determined from nonisothermal DSC measurements. We find that the quantity (ΔH_res + ΔH_cop) depends on the curing temperature (T_iso). Styrene homopolymerization and/or copolymerization lead to characteristic bonds modifications. The variations of the most characteristic bonds versus curing duration were studied from Fourier transform IR investigations. The data allow the determination of a relationship between transformation rate and curing duration using a time constant (τ) characteristic of each reaction involved during the liquid to solid-state transformation. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 67: 695–703, 1998     

Polyacrylamide-reactive styrene/unsaturated polyester microgel composites

Reactive microgels (RM) were prepared by the copolymerization of styrene and an unsaturated polyester in an emulsion of oil (styrene + unsaturated polyester) in water. The adsorption of the unsaturated polyester on the water–oil interface ensured the stability of the emulsion. Furthermore, polyacrylamide (PAAM) crosslinked with RM was obtained by suspending RM particles in an aqueous AAM solution and polymerizing the system at 70°C to obtain a PAAM–RM composite. The extraction experiments of the RM with dioxane and of the PAAM with water indicated the presence of small amounts of soluble PAAM homopolymers and negligible amounts of free RM, the materials being PAAM crosslinked by RM. The extent of swelling of these materials in water decreased with increasing weight ratio of RM/AAM and was independent of the composition of RM. When the final polymerization temperature was increased to 130°C, RM reacted not only with AAM to form a crosslinked polymer, but also with itself to form semi-interpenetrating reactive polymer networks (SIRPN). The extent of swelling of PAAM–RM SIRPN in water was much lower than that of the PAAM–RM material. Membranes were also prepared by hot pressing at 200°C the PAAM–RM and PAAM–RM SIRPN composites. The swelling behavior of these membranes in water, acetone, tetrahydrofuran, acrylic acid, ethyl alcohol, and dioxane, as well as in the mixtures of ethyl alcohol–water, acetone–water, tetrahydrofuran–water, and acrylic acid–water, was investigated. © 1995 John Wiley & Sons, Inc.     

苯乙烯对不饱和聚酯树脂性能的影响

本文主要探讨了不饱和聚酯中应用得最广泛的活性稀释剂——苯乙烯，对不饱和聚酯树脂机械性能、电性能、吸水性、耐化学性等的影响，从而为实际生产中采用最佳的苯乙烯含量提供参考。     

Copolymerization of polyvinylpyridine macromonomers with styrene

Summary Free radical Copolymerization of ( -methylstyryl) poly (2-vinylpyridine) macromonomers with styrene was performed. After separation of residual macromonomer the graft copolymers were submitted to a careful characterization.The copolymers were generally of rather low molecular weight and the average number of grafts per backbone chain was found close to unity. Nevertheless, these polymeric species tend to give aggregates and/or emulsions in selective solvents of the grafts, a typical behaviour of graft copolymers.     

Primary processes of the thermal degradation of HET acid containing unsaturated polyester cured with styrene

The primary processes of thermal degradation of 1,4,5,6,7,7-hexachloro-5-norbornene-2,3-dicarboxylic (HET) group containing unsturated polyesters cured with styrene were investigated. DTA traces in nitrogen atmosphere showed a much more pronounced endothermic reaction as the chlorine content in the unsaturated polyester resin decreased. This could be associated to the unzipping of the polystyrene units which is interfered by hexachlorocyclopentadiene ejected during degradation. Actually the styrene formation is prevented in a certain range of temperature due to the interaction with hexachlorocyclopentadiene. This was proved by on-line mass spectroscopic analysis of the degrading polymer.     

Copolymerization of elemental sulfur with styrene

Copolymerization of elemental sulfur with styrene in the presence and absence of metallic sodium was studied at 120°C and 138°C. Propagation of the reaction was followed by gel permeation chromatography (GPC). Glass transition temperatures of all samples were obtained by differential scanning calorimetry (DSC). Reaction products were fractionated with a preparative-type GPC, and each fraction was characterized by DSC, vapor pressure osmometry, infrared spectrophotometry, and both proton and carbon-13 nuclear magnetic resonance spectrometry. Results indicate that the product is a true copolymer of styrene and sulfur. Kinetics of the copolymerization were studied using GPC to monitor styrene and sulfur concentrations. The initial rate of copolymerization (as followed by the consumption of styrene and sulfur) decreases with increasing initial styrene to sulfur ratio. From kinetic analyses, ratios of the rate constants of homo- and copolymerization were determined. Copolymerization of the reactants is more spontaneous than homopolymerization. The reactivity ratios obtained are 0.2 for styrene and 0.6 for sulfur.     

Microscopy of the morphology in low styrene emission glass fiber/unsaturated polyester laminates

Low styrene emission (LSE) unsaturated polyester resins are of interest in the context of increasing environmental concerns in the society. LSE resins have been developed to decrease styrene emission during the processing of composites based on unsaturated polyesters. In this article we applied a microscopy methodology to study morphology effects in laminates based on LSE polyesters. The study connects to the longer term objective to improve the understanding of how additives reduce styrene emission without imparting delamination resistance in composite laminates based on LSE polyesters. The major morphology differences between laminates made from different polyesters are discussed, including birefringent layers present as an interphase between different layers. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 71: 1555–1562, 1999     

利用废聚酯制备对苯型不饱和聚酯树脂的研究

介绍了利用废聚酯制备对苯型不饱和聚酯树酯的方法。研究表明,该工艺简单合理,产品的耐腐蚀性、耐热性、机械性能和电性能优良     

Theoretical and experimental conversion in the curing of unsaturated polyester resins with styrene as a crosslinking agent

The reaction of unsaturated polyester resin is a free radical copolymerization between the styrene monomer and the unsaturated polyester. Depending on the temperature and other processing conditions, some of the reacting molecular species remain, after curing, in the form of residual monomer and soluble polymer that do not contribute to the network structure. By means of DSC and gel permeation chromatography (G.P.C.) techniques, we have investigated the differences between theoretical and experimental reaction heats of unsaturated polyester samples with different styrene/polyester ratios, the residual species formed, and the conversion of reactive groups.     

不饱和聚酯树脂微乳液的研究(Ⅲ) 磺酸盐不饱和聚酯树脂微乳化的表征

研究了4种正构醇(正丙醇、正丁醇、正戊醇和正己醇)对磺酸盐不饱和聚酯树脂的粘度和电导率的影响,聚酯树脂中醇含量增加,溶液的电导率增大,粘度下降;聚酯树脂中的醇含量相同时,醇的碳链越短,溶液的粘度越低,电导率越大。在一定的温度和搅拌速度下,将含有一定量醇的磺酸盐不饱和聚酯树脂加水微乳化,用微乳化过程中体系粘度和阻抗的变化表征了微乳化相反转过程,发现粘度比电导表征相转变更好。用差示扫描量热法的吸收热焓和吸收峰的温度判断了不同含水量时体系的相态。     

Copolymerization of styrene. IV. Copolymerization with esters of benzylidenecyanoacetic acid

Styrene was copolymerized in bulk with a number of esters of benzylidenecyanoacetic acid. The kinetic scheme of all pairs fitted the improved scheme of copolymerization, taking into account the effect of the penultimate unit. The Alfrey-Price Q and e values were calculated. Using the modified Taft equation, log (1/r₁) = ρ^*σ^* + δE_s, it was found that the relative reactivities of the ester monomers toward the polystyryl radical were correlated by the polar substituent constants σ^* of the ester alkyl groups (ρ^* = 0.14) and not by their steric substituent constants E_s (δ = 0.008).     

Copolymerization of alpha-methyl styrene with butyl acrylate in bulk

The kinetics of the copolymerization of alpha-methyl styrene (AMS) and butyl acrylate (BA) have been studied for the first time. Reactivity ratios for the system have been assessed over a range of temperatures (60-140 °C). Copolymerization models that account for monomer depropagation have been considered in order to determine the importance of depropagation effects for the chosen set of reaction conditions. Full conversion range experiments have been carried out to assess the effects of feed composition, temperature and initiator concentration on polymerization kinetics.     

Dynamic mechanical analysis of segmental relaxation in unsaturated polyester resin networks: Effect of styrene content

The effect of styrene content on non-exponential and non-Arrhenius behavior of the α-relaxation of cured unsaturated polyester resins (UPR) was investigated by dynamic mechanical analysis (DMA). To compare the temperature dependence of the relaxation times, the Angell fragility concept was applied to samples with different crosslink densities. Furthermore, the number of structural units per cooperatively rearranging region (CRR) was estimated using random walk model and the modified Adam-Gibbs theory. The results showed that rising styrene content enhanced the crosslink density of the networks, which altered the intensity and broadness of the α-relaxation. The fragility index, a measure of temperature dependence of relaxation time, and the average size of CRR at glass transition region was also increased by styrene content. Therefore, the segmental relaxation in networks with higher crosslink density could be associated with stronger intermolecular coupling. In addition, it was observed that the mean required energy for internal rearrangement of structural units within the CRR decreased as the fragility index increased, while the mean barrier height for repositioning of a CRR in cooperation to its local environment was nearly constant.     

Preparation of a water soluble polyester surfactant and its use in the emulsion polymerization of styrene

Summary The synthesis procedure of Chen and Liu (1) was used to prepare a polyester surfactant from dimethyl 5-sulfoisophthalate, sodium salt, polyoxyethylene (MW 200) and phthalic anhydride by a two step esterification process. The surfactant has the unique structural features of multiple ionic groups and polyoxyethylene chains for hydrophilicity and aromatic ester linkages for hydrophobicity. The polyester surfactant exhibited a CMC of 0.25% (w/v) and a surface tension lowering of 23 dynes/cm. The use of the surfactant as stabilizer for the emulsion polymerization of styrene produced some unusual results. While the rate of polymerization was independent of surfactant concentration, the number of particles increased as N [S]^0.91. The molecular weight of polystyrene produced was low and found not to be a function of surfactant concentration. The structural features of the surfactant suggest that a depletion stabilization mechanism might be operative in this system.     

Modification of unsaturated polyester resin with bismaleimide

The modification of a commercially available unsaturated polyester resin with 4,4′‐bismaleimidodiphenylmethane is presented. The properties of the modified resins were compared with those of the nonmodified resin, and the resins were characterized in the noncured state and after curing. The results indicate that the addition of bismaleimide to unsaturated polyester resin not only improves its properties but also accelerates the curing reactions. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 2003–2007, 2001     

Copolymerization propagation kinetics of styrene with alkyl acrylates

Propagation rate constants have been determined at two temperatures (298 K and 323 K) for the copolymerizations of styrene (STY) with methyl acrylate (MA) and STY with n-butyl acrylate (BA) over a range of monomer feed compositions. A pulsed UV laser was used as an initiation source and gel permeation chromatography (GPC) was utilized to analyse the products. None of the copolymerizations conformed to the Mayo-Lewis model, with respect to their propagation rate constants. The results were interpreted on the basis of a penultimate effect on the propagation reaction. In addition, Mark-Houwink constants were determined for poly(MA) and poly(BA) in tetrahydrofuran (THF) at 298 K. These constants are given as [K(dm³ kg^?1),α]: 7·88 × 10^?3, 0·885 and 8·57 × 10³, 0·865 for poly(MA) and poly(BA) respectively.     

气干型不饱和聚酯树脂

论述了以烯丙基 (缩水 )甘油醚改善不饱和聚酯树脂的气干性 ,确定了气干性单体的最佳用量及树脂的稳定性酸值。     

Waterborne unsaturated polyester resins

The transformation of solvent soluble unsaturated polyester resins into resins able to form stable water dispersion is presented in this paper. The methods of modification are discussed, consisting of the introduction of polar hydrophilic groups such as carboxylic and sulfonic ones (sodium 5‐sulfonatoisophthalic acid) into the resin molecule, which ensure good tolerance with water. Instead of styrene, glycerol monoethers of allyl alcohol and unsaturated fatty alcohols were used as reactive built‐in crosslinking monomers for resin modification. The influence of the resin composition and method of synthesis on the dispersion stability and properties of photocurable lacquer coatings obtained from the waterborne resins were investigated.     

Copolymerization of styrene with acrylamide in an emulsifier-free aqueous medium

Copolymerization of styrene with acrylamide was carried out in an emulsifier-free aqueous medium. The resulting latex contained an appreciable amount of acrylamide-rich copolymer in the serum. The copolymerization course was divided into three stages on the basis of the main reaction locus. At first, acrylamide polymerized in preference to styrene in the aqueous phase. Water-soluble growing radicals lost hydrophilicity rapidly and nucleated the particles. After particle formation, styrene polymerized exclusively in the particles until styrene droplets disappeared. The decrease in the concentration of residual styrene monomer caused growing radicals to keep the hydrophilicity for a long time, and polymerization of acrylamide was accelerated in the aqueous phase. Polymerizations at higher temperature and lower pH resulted in prolongation of the first stage of the polymerization, that is, preferential polymerization of acrylamide in the aqueous phase. An increase in the acrylamide fraction in monomer feed caused some decreases in the particle size and its uniformity.