Improvement of Mechanical Properties of Unsaturated Polyesters by Acrylonitrile

Propylene glycol- and diethylene glycol-based unsaturated polyesters were prepared and hardened by using styrene and acrylonitrile monomer mixtures. The addition of 12% acrylonitrile to a propylene glycol-based polyester containing 40% styrene increased the hardness from 12 BHN to 26 BHN. The addition of 20% acrylonitrile increased the impact strength of the same polyester from 14 J/m width to 39 J/m width. The diethylene glycol-based polyester containing 40% styrene and 40% acrylonitrile achieved a hardness of 23 BHN and an impact strength of 59 J/m width.     

基于电子束辅助固化的木塑复合材料的研究

在辐射剂量为56kGy的双面电子束辐照工艺条件下，制备了苯乙烯(St)、苯乙烯与不饱和聚酯树脂(St／UPE)混合物以及苯乙烯与环氧丙烯酸酯树脂(St／EA)混合物浸渍的冬瓜木和松木系列木塑复合材料，研究了木材和浸渍液体种类以及电子束辐射对浸渍液体的聚合和固化程度以及所得木塑复合材料性能的影响。结果表明在电子束辅助固化工艺条件下，浸入木材的St、St/UPE和St／EA的聚合率以及St／UPE和St／EA的固化率均可大于90％。木塑复合材料的硬度和压缩强度较原木材可提高2～6倍，其1昼夜吸水率则从原木材的64．6％和52．8％分别降低到8．9％～12．9％和7．0％～7．9％。     

Cure behavior of unsaturated polyester/modified montmorillonite nanocomposites

Dynamic rheology, differential scanning calorimetry and in situ Fourier transform infrared spectroscopy were used to study the cure behavior of unsaturated polyester/modified montmorillonite nanocomposites. The results showed that their gel times increased markedly at the same cure temperature, and that the activation energy of the nanocomposites was higher than that of the pure unsaturated polyester. Their peak temperatures of enthalpy increased as well. The total exotherm of the cure reaction declined and the cure rate decreased. In the curing process of pure unsaturated polyesters, the conversion of styrene was higher than that of the double bonds on unsaturated polyester macromolecular chains. The cure mechanism of the unsaturated polyester/modified montmorillonite changed because of the presence of double bonds in the layers of modified montmorillonite. However, the conversion of styrene in the nanocomposites was lower than that of double bonds on unsaturated polyester chains during cure at room temperature, and the conversion of styrene was increased after post‐curing and was higher than that of the double bonds on unsaturated polyester chains at the end of the cure reaction. Moreover, the degree of reaction of double bonds on unsaturated polyester chains of the nanocomposites was higher than that of unsaturated polyesters. Copyright © 2006 Society of Chemical Industry     

Effects of resin chemistry on redox polymerization of unsaturated polyester resins

Unsaturated polyester resins are the most widely used thermoset resins in the composite industry. In this study, three well‐defined unsaturated polyester resins were used. These resins have similar number‐average molecular weights, and they have different numbers of C?C bonds per molecule. The reaction kinetics of unsaturated polyester resins was studied using a differential scanning calorimeter (DSC) and a Fourier transform infrared (FTIR) spectrometer. The glass transition temperature of the isothermally cured resin was also measured. Trapped radicals were observed in the cured polyester resin from electron spin resonance (ESR) spectroscopy. Considering the diffusion‐limitation effect, a simple kinetic model was developed to simulate the reaction rate and conversion profiles of polyester vinylene and styrene vinyl groups, as well as the total reaction rate and conversion. Experimental results from DSC and FTIR measurements compare favorably with the model prediction. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 211–227, 2002; DOI 10.1002/app.10317     

Studies on sand/clay unsaturated polyester composite materials

The effect of a radiation‐initiated polyester on the physicomechanical properties of a sand/clay‐polyester composite has been investigated. The unsaturated polyester resins containing various styrene contents were used at different sand/clay composites from 10 to 70 wt % with respect to the weight of sand and clay together; polymerization was conducted using γ‐irradiation at 50 kGy. Also, different particle sizes of clay (namely 1.25–0.80, 0.80–0.50, and <0.50) were used. The compressive strength, apparent porosity, and water absorption—in addition to infrared spectroscopy of the composite samples—were studied. Results indicate that the compressive strength decreases with an increase in sand/clay, as well as the styrene content in the unsaturated polyester resin, whereas the apparent porosity and water absorption of the composite samples increase. Infrared spectra showed the appearance of new bands, which indicated a chemical reaction between polyester and clay constituents. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 72: 1031–1038, 1999     

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.     

Infrared study of the cure of unsaturated polyester

The infrared spectra of unsaturated polyesters in process of cure have been taken of samples free from unreacted protion. Styrene and polyester fractions in the curing polyester films were assessed from comparison of the band intensities at 695 and 740 cm.^?1. The styrene fraction in curing films was found to increase as cure proceeded, and the delayed curing was seen to be accompanied by a build-up of films of lower styrene content. The differences between samples observed in the mechanical behavior were considered attributable for the most part to the difference in styrene content.     

Rheological investigations on the flow behavior of polymer‐microsized iron powder composites

With respect to the fabrication of metal parts carrying surface relief microstructures using composite reaction molding as a rapid prototyping variant of micrometal injection molding, the influence of microsized iron powder on the viscosity of different unsaturated polyester resins applied as polymer binder has been investigated systematically. The initial binder viscosity determines the viscosity of the composite and hence the accessible critical filler load. A further dilution of the unsaturated polyester resin with styrene allows a significant increase of the filler load at constant shear rate and temperature from 36 up to 57 vol% iron content. A successful estimation of the critical filler load using different established empirical models initially developed for ceramic‐filled solutions or dispersions is possible. A pronounced flow activation energy increase at high iron loads was also observed. POLYM. COMPOS., 2009. © 2008 Society of Plastics Engineers     

Mechanical and Morphological Studies of Rubber Wood Sawdust-Filled UPR Composite Based on Recycled PET

Rubber wood sawdust fillers were mixed with unsaturated polyester matrix, which was prepared by recycling of PET waste from soft drink bottles, to prepare rubber wood sawdust/UPR composite. PET wastes were subjected to recycle by glycolysis and depolymerized to its monomer and dimmer. The glycolysed product was used to prepare unsaturated polyester resin. The FTIR analysis has been done on the resin and the glycolysed product. The resin then mixed with rubber wood sawdust fillers before and after alkali treatment with 10% NaOH. The effect of surface treatment and filler content on the mechanical properties and water absorption of the composite were studied. The tensile fractured surfaces of the composites were studied by Scanning Electron Microscopic (SEM) technique to investigate the interfacial bonding between the matrix and the filler. The results show that the tensile modulus increased with increasing filler contents. In addition, the results show that alkali treatment causes a better adhesion between rubber wood sawdust and UPR matrix and improves the mechanical properties.     

Radiation grafting of vinyl monomers onto wood pulp cellulose. Part I

The effect of dose, dose rate, monomer type, and monomer concentration on the water transport behavior in grafted cellulose pulp and hand sheets was studied. At low dose rates, grafting rates of styrene onto wood pulp were less with hand sheets than with the pulp itself. Grafting was also found to be decreased by increasing the dose rate. Grafting mixtures of styrene and acrylonitrile gave better yields than styrene alone. Excellent grafting yields were obtained by treating the pulp or hand sheets with water before adding vinyl monomers. In this way, solvents such as dioxane could be eliminated from the grafting mixture. The hand sheets, grafted with mixtures of acrylonitrile and styrene, had good mechanical properties although less than the corresponding ungrafted sheets. Grafting decreased the moisture regain in pulp and hand sheets. Gamma irradiation of wood pulp under ambient conditions without additives reduced the water sorption considerably.     

Some filler effects on cross-linking of unsaturated polyesters

The effect of five fillers on the cross-linking macro-and microcharacteristics of simple unsaturated polyester resins was investigated by differential scanning calorimetry (DSC), reactivity tests, and gel time tests. Glass beads and silica flour appeared to have little influence on the cross-linking reaction of the resin itself, their effect being comparable to mere dilution of the resin. Kaolin presented some interaction with the resin due to its absorption characteristics and acid groups. Reground polyester/glass fiber powder and especially wood flour appeared to present clear chemical interactions with the curing behavior of the resin. Wood flour, in particular, was shown by DSC analysis to strongly co-react with the resin during cross-linking and altered markedly the resin enthalpy change and energy of activation during curing. The wood flour component causing the altered behavior of the resin appears to be lignin. DSC analysis of resins filled with three different types of isolated lignins indicated that this wood flour component reacts in a heterogeneous phase reaction with the resin during cross-linking. It appears that it is the lignin unsaturated carbon–carbon double bonds at the polyester/wood flour and at the polyester/lignin interphases that are likely to co-react by heterogeneous phase radical cross-linking with the polyester resin and styrene unsaturation, markedly changing the resin curing behavior. © 1993 John Wiley & Sons, Inc.     

不饱和聚酯对树脂型人造石质量影响研究

通过显微分析、粘度分析、强度测试等方法研究了不饱和聚酯的用量及粘度等对树脂型人造石质量的影响,并分析了其机理。结果表明,不饱和聚酯用量不足,使粉料出现不均匀润湿,导致树脂型人造石表面出现斑印,弯曲强度下降;加入苯乙烯可降低树脂粘度,在一定程度上改善润湿效果,从而减少了树脂型人造石表面的斑印,并提高弯曲强度,但过高的苯乙烯掺量会使弯曲强度降低。当不饱和聚酯质量分数为7%,苯乙烯质量分数约1%时,树脂型人造石表面的斑印可基本消除。     

木粉填充聚乙烯复合材料的研究

研究了线型低密度聚乙烯（ＬＬＤＰＥ）／木粉复合材料的力学性能及生方法。结果表明，随木粉含量的增加，ＬＬＤＰＥ／木粉复合材料的冲击强度和拉伸强度均下降。用过氧化二异丙苯（ＤＣＰ）引发聚乙烯交联能显著提高复合材料的力学性能。用表面活性剂对木粉进行预处理后，在改善复合材料加工性能的同时，使复合材料的冲击强度略有提高，但拉伸强度下降。不饱和聚酯与ＤＣＰ并用有良好的协同性。     

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.     

Influence of the ratio of styrene and acrylonitrile in crosslinked polymeric binders for use in high-temperature polymer concrete composites

The feasibility of using a monomer composition based on a styrene–acrylonitrile copolymer as a binder in high-strength and chemically resistant polymer concrete was demonstrated earlier. From this work it is clear that properties of the polymer concrete composite are dependent on the styrene/acrylonitrile ratio. This paper deals with the study of the effect of the styrene/acrylonitrile ratio in styrene–acrylonitrile–acrylamide–trimethylolpropane trimethacrylate monomer formulations on the thermomechanical properties of polymer concrete composites.     

Monitoring the cure of unsaturated polyester resins by pressure DSC and FTIR-PLC

A high pressure differential scanning calorimeter (DSC) and a Fourier transform infrared (FTIR) spectrometer with a prism liquid cell (PLC) were used to monitor the reaction kinetics of styrene-unsaturated polyester resins at elevated curing temperatures and pressures. The thermal method is easy to perform but provides only an overall reaction exotherm. The spectroscopic method can detect the detailed reaction mechanism of copolymerizations. It is, however, less quantitative and the calculation is much more time-consuming compared to the thermal analysis. Reactions of two unsaturated polyester resins with different molecular structure were measured by these two methods. Results showed that applying cure pressure on unsaturated polyester resins reduced the reaction rate but increased the final conversion. The styrene reaction was enhanced more than the polyester reaction at high curing temperatures.     

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     

交联剂对废聚酯醇解制不饱和清漆性能的影响

以废聚酯、乙二醇和丙三醇为原料制备了不饱和聚酯,进而制得了不饱和聚酯清漆。当不饱和聚酯和苯乙烯的质量比为100：30,促进刑为不饱和聚酯的0.2％时,清漆的颜色较深,综合性能最佳;当不饱和聚酯、苯乙烯、MMA的质量比为100．0：31．5：3．5,促进剂为不饱和聚酯的0．1％时,清漆的颜色较浅,性能较佳。     

Curable resins based on recycled poly(ethylene terephthalate) for coating applications

Poly(ethylene terephthalate) waste was depolymerised in the presence of diethylene- or tetraethylene glycol and manganese acetate as a catalyst. An epoxy resin was then prepared by the reaction of these oligomers with epichlorohydrin in presence of NaOH as a catalyst. The produced oligomers were condensed with maleic anhydride and ethylene glycol to produce unsaturated polyester. The chemical structures of the resulting epoxy and unsaturated polyester resins were confirmed by ¹HNMR. The vinyl ester resins were used as cross-linking agents for unsaturated polyester resin diluted with styrene, using free radical initiator and accelerator. The 2-amino ethyl piprazine was used as hardener for epoxy resins. The curing behaviour of the unsaturated polyester resin, vinyl ester resins and styrene was evaluated at different temperatures ranged from 25 to 55 °C to calculate the curing activation energy of the system. The cured epoxy and unsaturated polyester resins were evaluated in coating application of steel.     

苯乙烯在不饱和聚酯树脂固化过程中的作用

采用原位红外光谱法研究了在不同制样条件下，苯乙烯的挥发对不饱和聚酯树脂的固化过程及固化产物的影响。结果表明：对于密封体系，固化时苯乙烯与不饱和聚酯反应较完全，形成网状结构，体系的转化率较高，固化反应速度也较快；而对于非密封体系，由于苯乙烯的大量挥发，导致体系的固化反应不完全，转化率低，当苯乙烯挥发到一定程度时，固化反应几乎无法进行。