Curing studies on modified epoxy and unsaturated polyester resins

Experimental studies were carried out on the curing behavior of unsaturated polyester and epoxy resins. The latter were modified with three different fillers (CaCO₃, CaSiO₃, and glass powder) and their curing behaviors studied. Polyesters exhibited faster cure rates than the epoxy resins. The gel time of the epoxy resins decreased with the addition of fillers. Data indicated that the peak exotherm of these thermosetting resins increased when filled with glass powder. The hardness of the curing mass increased with curing time. The use of gel-hardness number as a quality control parameter has been suggested.     

Curing reaction of saturated aliphatic polyester modified unsaturated polyester resins

Two series of unsaturated polyesters (UPE from isophthalic acid, fumaric acid, and propylene glycol) were prepared. In series-A resins, UPEs wee thickened with isocyanate-terminated saturated aliphatic polyestes, i.e., an isocyanate-terminated polycaprolactone diol (PE-di-OL), through reaction of the isocyanate group with the hydroxyl group of the UPE. In series-B resins, the UPEs were mixed with saturated aliphatic polyesters i.e., PE-di-OL. The curing reaction of these two series of UPEs with styrene was studied by using differential scanning calorimetry (DSC) and gel permeation chromatography (GPC). The DSC data show that for a fixed PE-di-OL molecular weight, the curing reaction rate of series-A UPE is faster than that of series-B UPE. The variation of microgel size during curing ws studied by GPC. These results revealed that microgel formation has a great effect on the kinetics of cure for the unsaturated polyester-styrene system. The curing of these two series of UPEs is found to strongly depend on the compatibility of the components in the curing system.     

MAP-POSS改性不饱和聚酯树脂的固化反应

为改进不饱和聚酯（UP）树脂的性能,用非等温差示扫描量热法（DSC）研究了甲基丙烯酰氧丙基笼形倍半硅氧烷（MAP-POSS）与通用UP树脂的共同化反应。UP、苯乙烯和MAP—POSS有较好的相容性,可共同固化,MAP-POSS可均匀分散在UP基体中形成原位纳米分子复合材料。测定了固化动力学参数,建立了固化反应动力学数学模型。     

Curing of unsaturated polyester resins with low exotherm peak

The curing behavior of an unsaturated polyester resin with low exotherm peak was studied by a standard procedure and by differential scanning calorimetry (DSC). A copper salt and α-methylstyrene were used as the polymerization retarders. The influence of the retarders on the exotherm peak temperature, gelation time, exothermic heat and the polymerization kinetics was investigated.     

Curing of unsaturated polyester resins: Effect of surface treatment of particulates

The effect of surface treatment of particulates on the curing kinetics of unsaturated polyester resin has been investigated using a differential scanning calorimeter. Two coupling agents, γ-methacryloxy propyltrimethoxy silane (γ-MPS) and phenyltriethoxy silane (PTS), were employed. The former reacted with the resin; the latter did not. A kinetic model of free radical addition polymerization was used. A correction factor was used to represent the effective free radical concentration in order to account for the formation of charge transfer complex between the glass beads and the free radicals in the resin. The results indicate that (1) the resin with treated particulates showed generally faster reaction rate and conversion than the resin with untreated particulates; (2) no obvious difference on the curing kinetics was observed between these two coupling agents; the primary role of coupling agent is to inhibit the influence of particulates on the curing kinetics of the resin by effective surface coverage; and (3) a minimum aqueous concentration of 0.05 wt% was suggested for surface treatment of particulates; the reaction rate of the resin was slightly improved when the concentration of the coupling agent was 0.01 wt%; this might possibly be due to insufficient coverage of the particulate surface.     

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.     

Curing of unsaturated polyester resins: Effects of comonomer composition. II. High-temperature reactions

The effects of comonomer composition of the curing kinetics of unsaturated polyester (UP) resins at 100–120°C were investigated by differential scanning calorimetry (DSC) and infrared spectroscopy (IR) over the entire conversion range. One commercial UP resin, UP2821, with 6.82 unsaturated C?C bonds per polyester molecule, was used. For styrene/UP2821 reactions, experimental results of the initial and maximum reaction rates by DSC at 100–120°C revealed that the styrene content, as well as the reaction temperature, would affect the formation of microgel structures. As the initial molar ratio of styrene to polyester C?C bonds increased, the styrene swelling effect could enhance the intramicrogel crosslinking reactions, while the styrene dilution effect could diminish the intermicrogel crosslinking reactions. The competition between the two reactions would depend on the reaction temperatures. Finally, a microgel-based reaction mechanism was proposed for the high temperature reactions. © 1993 John Wiley & Sons, Inc.     

Improving glass transition temperature of unsaturated polyester thermosets: Conventional unsaturated polyester resins

Highly crosslinkable unsaturated polyester resins (UPR) have attracted many interests in the application as reinforced matrix materials. Here, we present a systematical study of the influence of different curing conditions and styrene concentrations on resin viscosity and dynamic-mechanical properties of the thermoset. The pure maleic Palapreg® P18-03 was selected as model UPR because of its broad industrial use. By applying newly developed thermal curing profiles (without thermal initiators) and by raising the styrene content, the T_g of the network could be increased up to 206/215°C (1/10 Hz). For the first time, a fast curable UPR based on propylene glycol and neopentyl glycol with a T_g of up to 215°C is described. A partial substitution of problematic styrene with methylmethacrylate, tert-butylacrylate, and maleic anhydride (MA) was studied as well. MA leads to significantly improved resin reactivity. A resin containing 42 wt% styrene and 8 wt% MA yields thermosets with remarkably improved mechanical properties and with a narrower glass transition range compared to the original P18-03.     

不饱和聚酯树脂微乳液的研究(Ⅰ)不饱和聚酯树脂的微乳化

合成了不同磺酸盐含量的三种不饱和聚酯，通过拟三元相图分析磺酸盐含量、苯乙烯、不同正构醇和水组成的体系对微乳区域的影响。研究结果表明，磺酸盐不饱和聚酯同苯乙烯互溶的前提下，磺酸盐含量越大，其微乳液增溶的水量越大；磺酸盐含量一定时，苯乙烯含量越小，其微乳液增溶的水量越大；正构醇质量分数为在2％～10％范围内，其微乳液增溶的水量最多；三种醇相比较，正丁醇体系的微乳区是W／O型向O／W型过渡的连续区域，正丙醇体系的O／W型微乳液区明显不同于正丁醇体系，正戊醇体系不能形成水包油型的微乳区。     

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.     

不饱和聚酯树脂的粗化工艺

介绍了不饱和聚酯树脂的粗化工艺流程及各工艺规范通过正交试验确定了最佳粗化工艺条件：粗化液的体积分数为400ml／L温度为80～85℃,粗化时间为20min。讨论了粗化液用量、粗化温度和时间对粗化效果和镀层质量的影响经检测表明,该金属镀层与基体结合力良好目前该工艺已应用于生产中。     

Curing polyester resins with visible light

Radiation curing of unsaturated polyester resin-based compositions offers a number of significant advantages over the use of peroxides and similar free-radical polymerisation initiators; the cure process can be closely controlled, is usually much faster, and the fabricator is not required to measure out, add, and blend-in small quantities of catalyst. However most forms of radiation including ultra violet (UV) involve heavy initial expense and the need to provide shielding to protect personnel. Furthermore UV radiation will not usually penetrate deeply into thick glassfibre-containing compositions owing to the absorption of UV light by both resin and glass. Photoinitiator systems which need only visible light have now been developed however. Using these systems almost any available light source including fluorescent tubes, tungsten filament bulbs and of course natural sunlight and daylight will cause the resin to cure rapidly and completely. By controlling the intensity of the incident light continuous close control of the cure process is easily achieved. The advantages of reduced energy requirements, fast cure,‘one pot’ chemistry and built-in indicators of degree of cure have already led to a number of special applications for visible light curable polyester resins.     

Dielectric relaxation and crosslinking in unsaturated polyester resins

The properties of crosslinked thermosetting resins depend markedly on the completeness of the crosslinking process. Determination of the degree of cure of an unsaturated polyester resin has been studied previously by mechanical, spectroscopic and volume resistivity methods. In this respect the effect of cure time and temperature on the ac dielectric constant and dissipation factor at 1 kc/s and 10 kc/s is considered. The dissipation factor appears to be a most useful parameter for detecting changes in the degree of cure in the later stages of reaction. The electrical properties of the cured resin are discussed, and values for the energy of activation for electrical conduction are compared with literature reports on similar materials.     

GPC and HPLC characterization of unsaturated polyester resins

This article is concerned with the characterization of unsaturated polyester (UP) resins by conventional gel permeation chromatography (GPC), GPC connected with multiangle laser light scattering detector (GPC-MALLS), and reversed-phase high performance liquid chromatography (HPLC). The ability of particular methods to analyze UP resins is demonstrated in several examples. © 1994 John Wiley & Sons, Inc.     

Thermokinetics of unsaturated polyester and vinyl ester resins

An experimental study was carried out to investigate the isothermal and non-isothermal curing kinetics of unsaturated polyester and vinyl ester resins, using differential scanning calorimetry (DSC). Emphasis was put on investigating the effect of low-profile additives on the curing kinetics of the thermo-setting resins. For the study, a general-purpose polyester resin and a vinyl ester resin were used, together with polyvinyl acetate (PVAc) as low-profile additive, benzoyl peroxide as initiator, and N,N-dimethyl aniline as promoter. It has been found that (1) the addition of the low-profile thermoplastic-additive decreases the rate of cure and, also, the final degree of cure of the resins, (2) the total heat of cure generated by isothermal cure is lower than that generated by non-isothermal cure, and (3) the resin/initiator mixture with promoter exhibits two major exotherm peaks during non-isothermal cure, but only a single exotherm peak during isothermal cure.     

Thermally stimulated current in glass-laminated unsaturated polyester resins

Experimental results are reported on the electrical properties of glass-laminated unsaturated polyester (UP) resins. Measurements of the poling current as a function of temperature reveal two different activated processes. Above 50°C the activation energy is 160 kJ/mol and has been associated with ionic condition, possibly by protons, while at lower temperatures (below −70°C) the activation energy is very low (less than 40 kJ/mol) and is associated with dipole relaxation. It is concluded that the laminated UP resin undergoes a phase transformation between low and high temperatures, which gives rise to a completely different electrical response. This phase transformation can be associated with the glass transition of UP resin phase. In view of the low activation energy, giving rise to a polarization peak, it is concluded that the low temperature range (glassy state) favors strictly localized motions of charges—most likely electrons. At higher temperatures, the behavior corresponds to d.c. conductivity and is associated with extended motions of charge carriers with limitations at contacts and at internal barriers. According to the air gap measurements, the pronounced dip found in the temperature dependence of the poling current (in the range from 20 to −30°C) may be due to separation of conduction and dipole relaxation current. Thermally stimulated depolarization (TSD) current measurements reveal the presence of high internal fields due to space charges accumulated at the phase boundaries of glass fibers.     

Dilatometric study of low profile unsaturated polyester resins

An in-house-built and designed dilatometer was applied to the study of low profile unsaturated polyester resins. This article first describes the dilatometer used including its calibration then its application to low profile unsaturated polyester resins. Several series of dilatometry experiments were performed, to study the effect of low profile additive concentration and cure temperature on shrinkage control. Scanning electron micro-graphs of the samples were also prepared to show the correlation between shrinkage control and polymer morphology.     

不饱和树脂在氯碱工业中的应用

介绍了双酚A型不饱和树脂在哈尔滨华尔化工有限公司盐酸储罐、精盐水储罐、盐水沉降器中的应用情况及施工注意事项。     

Microgelation in the curing reaction of unsaturated polyester resins

A series of unsaturated polyesters were synthesized with various chemical structures and molecular weights. These unsaturated polyesters were used to study the curing reaction with styrene by using gel permeation chromatography and differential scanning calorimetry. The variation of the size of microgel particles during the curing reaction in unsaturated polyester–styrene resins was studied by using gel permeation chromatography. The size and structure of the microgels depend strongly on the polymer chain length and the number of vinyl groups on each unsaturated polyester chain. Using the differential scanning calorimetric method, the conversion of styrene and polyester vinyl groups during the reaction was measured. The experimental results of this study revealed that microgel formation has a great effect on the curing reaction of unsaturated polyester resins. © 1994 John Wiley & Sons, Inc.