Cure characterization of unsaturated polyester resin by fluorescence spectroscopy

A strong fluorescence emission was observed during cure of an unsaturated polyester resin containing about 30% styrene by weight. As the cure proceeded, the emission intensity at 306 nm increased. Model compound studies confirmed that the unsaturated polyester component exhibited negligible fluorescence when excited at 250 nm where styrene has strong absorption. Based on the studies of styrene/polystyrene mixtures, the fluorescence emission at 306 nm was attributed to a reduced inner‐filter effect of styrene monomer. Fluorescence intensity changes following cure at 75°C were correlated to the extent of styrene conversion determined by FT‐IR spectroscopy, demonstrating that the fluorescence measurement is more sensitive to styrene conversion in the later stages of cure than conventional IR measurements. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 2446–2450, 2004     

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     

Kinetic modeling of nanoclay‐reinforced unsaturated polyester resin

Curing behavior of an unsaturated polyester (UP) resin containing 1 wt% organically modified clay (OMC) catalyzed with methyl ethyl ketone peroxide (MEKP) initiator and promoted by cobalt naphthenate accelerator was investigated by dynamic differential scanning calorimetry (DSC) at five different heating rates of 5, 10, 15, 20, and 25°C/min. X‐ray diffraction and transmission electron microscopy were used to evaluate the morphology of UP/OMC composites. Results showed a mixture of intercalated and exfoliated morphology. The dynamic DSC curing curves showed a bimodal exothermic peak; therefore, two independent reactions, namely, redox and thermal copolymerizations were assumed. Kinetic parameters were calculated by using autocatalytic model and using Down hill simplex method and Runge–Kutta algorithm for each reaction. The addition of nanoclay resulted in decrease of the activation energy of the redox reaction compared to that of the neat UP resin. Also, the pre‐exponential factor of the first reaction for UP/OMC was less than that of the neat UP. Two factors including decreasing the activation energy and decreasing the number ofcollisions of reactionary components finally resulted in increasing the reaction rate of the first reaction out of the whole reaction in the system containing nanoclay compared to the neat UP resin. It is interesting that nanoclay has no effect on the thermal decomposition reaction. POLYM. COMPOS., © 2011 Society of Plastics Engineers.     

Cooperative rearrangement region in nanoclay‐reinforced unsaturated polyester resin

The effect of nanoclay on structural relaxation of unsaturated polyester (UP) resin containing 3 wt% Cloisite 10A (UP/10A), 3 wt% Cloisite 30B (UP/30B), and the neat resin was investigated by differential scanning calorimetry (DSC) and temperature modulated differential scanning calorimetry (TMDSC). X‐ray diffraction and transmission electron microscopy were used to evaluate the morphology of UP/10A and UP/30B nanocomposites. According to the strong‐fragile concept proposed by Angel, the values of the fragility index m were determined. The average size of a cooperative rearranging region (CRR) at the glass transition temperature (T_g) was then calculated. Considering the significant increase in δT (the mean temperature fluctuation) of UP/10A, it was concluded that UP/10A system was more heterogeneous than the neat UP and UP/30B specimen. Significant drop in T_g accompanied by an increase in δT and a decrease in characteristic length of cooperativity at glass transition temperature (ξ_Tg) might be a sign of existence of smaller average CRR sizes in UP/10A nanocomposites. Results showed that the increase in the concentration of styrene between galleries of Cloisite 10A caused a decrease in styrene content outside the nanoclay layers leading to diminishing of crosslink density and as a consequence the decrease of ξ_Tg. POLYM. ENG. SCI., 54:2859–2865, 2014. © 2014 Society of Plastics Engineers     

N-苯马来酰亚胺改性不饱和聚酯树脂

研究了N-苯基马来酰亚胺(NPMI)在苯乙烯中的溶解规律,即NPMI在苯乙烯中溶解度呈线性关系:5~35℃时,S=0.1t;40~60℃时,S=4.2+2.2t。NPMI的引入可以有效提高不饱和聚酯(UP)树脂的耐热性,NPMI用量在1%~9%,可以将UP树脂的热变形温度提高4.5℃。研究了NPMI用量对UP树脂浇注体拉伸强度和冲击强度的影响,对材料冲击断面进行了SEM表征。NPMI用量为2%时,材料的拉伸强度最大,提高了5.5%,达到67.3 MPa;NPMI用量为6%时,材料的冲击强度最大,提高了23%,达到8.6 kJ/m2。     

Effect of resin composition on curing kinetic of nanoclay-reinforced unsaturated polyester resins

Curing behavior of two resins of different unsaturated polyesters [FARAPOL 101 (UF) and Bushpol 81715 (UB)] containing 3 wt % organically modified clay (OMC), catalyzed with methyl ethyl ketone peroxide as initiator and promoted by cobalt naphtenate accelerator was investigated by dynamic differential scanning calorimetry (DSC) and gel time test methods. Chemical structures of UF and UB resins were characterized by ¹H NMR, XRD and TEM techniques were used for morphology characterization of nanocomposites. DSC results showed that after adding OMC, the redox reaction rate of UF increased less than that of UB resin. Measurements of cloud-point temperature (T _c) indicated that the miscibility of styrene/UB alkyd chains was more than that of styrene/UF alkyd chains. Therefore, the alkyd/styrene ratio inside the platelets in UB would be more than that in the platelets in UF nanocomposite. Among the three factors in redox reaction rate of UB/OMC and UF/OMC systems namely: (1) decreasing alkyd-styrene copolymerization share among platelets of OMC, (2) decreasing the activation energy, (3) decreasing the number of collisions, the first one was more effective in UF/OMC system than in UB/OMC system. Consequently, the difference between redox reaction rates of UF/OMC and neat UF was negligible compared with the corresponding difference for UB/OMC and neat UB system.     

Preparation and cure behavior of organoclay‐modified allyl‐functional benzoxazine resin and the properties of their nanocomposites

A new type of polybenzoxazine‐clay nanocomposites were prepared by the in‐situ polymerization of allyl‐functional benzoxazine monomer, bis(3‐allyl‐3,4‐dihydro‐2H‐1,3‐benzoxazinyl)isopropane (B‐ala), in the presence of two different types of organoclay, allyldimethylstearylammonium‐montmorillonite and propyldimethylstearylammonium‐montmorillonite. The organoclays were mixed with molten B‐ala, followed by pouring into glass mold and then gradual curing up to 250°C. DSC and IR were used to follow the cure behavior of B‐ala in the presence of organoclay, indicating that organoclays catalyzed the ring opening of cyclic benzoxazine structure. The XRD of the nanocomposites showed featureless patterns, suggesting the exfoliation of the organoclay into the matrix. The viscoelastic properties of the hybrids showed that the glass transition temperatures (T_g) of the nanocomposites shifted to lower temperature in the presence of small amount of organoclay, but T_g started to increase with the increase of the organoclay content. This result suggests that, in the presence of organoclay, the curing reaction of ally and benzoxazine occurred in a different way, resulting in a different network structure. However, the presence of dispersed layered silicates into the matrix enhanced the thermal stability over the neat thermoset resin. POLYM. COMPOS., 2008. © 2008 Society of Plastics Engineers     

不饱和聚酯/粘土纳米复合材料的制备与性能

为了改善不饱和聚酯树脂的力学性能,将有机改性的蒙脱土与苯乙烯均匀混合后再掺合到不饱和聚酯(UP)中,制备了不同粘土含量的不饱和聚酯树脂/粘土(UPR/Clay)纳米复合材料。差热分析发现随着粘土含量的增加,玻璃化温度有所增加。X射线衍射数据表明,纳米复合材料中粘土原有的峰基本消失,表明粘土结构层间距增大,结合透射电镜(TEM),确定此纳米复合材料为插层和剥离结构。冲击试验发现随着粘土加入冲击强度有一最大值。     

Gel time and polymerization kinetics of unsaturated polyester resin/clay montmorillonite nanocomposites

This article presents the variation of viscosity, gel point, and curing kinetic process of nanocomposites based on unsaturated polyester resin (UPR) and natural nano‐clay CloisiteNa^+® and organomodified Cloisite15A^® montmorillonites (MMT). Different amounts (1–10 wt%) of nanoclays were added homogeneously before the cross‐linking reaction of the thermoset polymer. The complex viscosity before curing was especially dependent on the CloisiteNa^+® content more than Cloisite15A^®. The G' and G'' slope also as the complex viscosity criterion were used to determine the nanocomposites gel time variation. Isothermal differential scanning calorimetry measurements were performed to calculate the reaction order and the rate constant using different empirical equations. These results demonstrated a catalytic effect of the clays on the UPR cure, with diffusion controlled phenomena predominating at high conversions. The X‐ray diffraction patterns were useful for identifying the nanocomposites formation, and gave information about the clays dispersion, which served to support the rheological and polymerization kinetic results. Finally, natural MMT CloisiteNa^+®decreased gel time and was more compatible with UPR than the organomodified Cloisite15A^®. POLYM. COMPOS., 36:1931–1940, 2015. © 2014 Society of Plastics Engineers     

Modification of unsaturated polyester resin by polyurethane prepolymers

Unsaturated polyester resins (UPRs) are extensively used by the fiber‐reinforced plastic (FRPs) industry. These resins have the disadvantages of brittleness and poor resistance to crack propagation. In this study, UPRs were chemically modified by reactive blending with polyurethane prepolymers having terminal isocyanate groups. Hybrid networks were formed by copolymerisation of unsaturated polyesters with styrene and simultaneous reaction between terminal hydroxyl groups of unsaturated polyester and isocyanate groups of polyurethane prepolymer. The prepolymers were based on toluene diisocyanate (TDI) and each of hydroxy‐terminated natural rubber (HTNR), hydroxy‐terminated polybutadiene (HTPB), polyethylene glycol (PEG), and castor oil. Properties like tensile strength, toughness, impact resistance, and elongation‐at‐break of the modified UPRs show considerable improvement by this modification. The thermal stability of the copolymer is also marginally better. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 449–456, 2006     

Control of microvoids in resol phenolic resin using unsaturated polyester

A major drawback of cured phenol formaldehyde resin is the presence of microvoids, resulting from the liberation of condensation byproducts. In an attempt to rectify this, phenolic resol resin was blended with unsaturated polyester (UP). UPs with various maleic anhydride (MA) to phthalic anhydride (PA) ratios were synthesized and later mixed with resol resin in various proportions. The best MA/PA ratio was found out by determining the specific gravity, acetone‐soluble matter, and volatile content of the cast blend, cured under a satisfactory time–temperature schedule. The influence of acid value of the UP and the most desirable UP content were also investigated on the basis of the quality of the modified phenolic samples. The structural changes in the modified resin were studied using FTIR spectroscopy. Scanning electron micrographs (SEM) of the fractured surfaces were obtained to ascertain the extent of microvoids in the modified resin. Both thermogravimetric analysis results and SEM micrographs confirm the effectiveness of UP in reducing the microvoids in the cast resol resin. The tensile and impact strengths of the samples also reflect the superior quality of the resol phenolic resins that have been modified by UP. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

不饱和聚酯树脂的常温固化

综述了不饱和聚酯树脂的固化特征、固化反应,固化机理和交联固化反应活性。介绍了4种固化反应过程、引发剂和固化反应链增长过程,同时介绍了其交联固化反应活性及影响因素。     

不饱和聚酯树脂的常温固化

(续接上期)5不饱和聚酯树脂固化网络结构分析5·1不饱和聚酯树脂交联网络结构不饱和聚酯中的双键与交联剂中的双键聚合形成不溶不熔的交联网络,网络中含有2种聚合物分子链结构。网络主体由不饱和聚酯分子链的无规线团组成,苯乙烯共聚分子链穿插其中,将不饱和聚酯分子链连接和固     

国外不饱和聚酯树脂工业新进展

综述了国外不饱和聚酯树脂的市场动态及技术进展。     

不饱和聚酯树脂的苯乙烯迁移

不饱和聚酯（UP)树脂是通用塑料．已在多种应用中使用。尽管UP树脂不是主要的食品包装材料．但已应用于自来水管．大桶和制品表面。在这些应用中．UP树脂具有持续或反复接触食品或水的可能性。在本报告中．向UP树脂的加工者和转产者建议．降低UP树脂中苯乙烯迁移量．以便按照食品接触规定和供水网络规定的法律办事。     

Comparative study of the cure kinetics of an unsaturated polyester resin using different procedures

The cure kinetics of an unsaturated polyester resin were studied by differential scanning calorimetry (DSC), and different dynamic and isothermal procedures were compared. It was established that the isothermal kinetic analysis through the isoconversional adjustment lnt = A + E/RT is the method that offers the most accurate results for unsaturated polyester resin cure kinetics. From this comparative study it was noted that the activation energy not only varies according to the degree of conversion but also according to the method used to evaluate the kinetic parameters. Furthermore, it was shown that the activation energy cannot be separated from the other adjustment parameters, so the different kinetic procedures used are not generally comparable. Different methods of evaluating the degrees of conversion α and the reaction rates dα/dt according to the experimental reaction heat were also studied. It was found that the method used has a strong influence on the values of α and dα/dt, but only a slight one on the kinetic parameters.     

SiC颗粒增强不饱和聚酯树脂复合材料的力学性能

采用万能试验机和硬度计测试研究了SiC颗粒含量和粒径对不饱和聚酯树脂基复合材料力学性能的影响,通过扫描电子显微镜观察了拉伸试样的端口形貌。结果表明,填充的SiC质量分数为10%时,其不饱和聚酯树脂复合材料拉伸强度达到最大,8000目、1000目SiC填充体系拉伸强度分别为53.2MPa,44.8MPa,较纯树脂体系提高68.1%,41.5%。当SiC质量分数为30%时,SiC填充体系的弹性模量较纯树脂体系提高25.8%以上,硬度提高2.3%以上,SiC颗粒尺寸对复合材料的弹性模量和硬度影响不大。SiC/不饱和聚酯树脂复合材料的断裂属脆性断裂。     

Curing reaction of unsaturated polyester resin modified by dicyclopentadiene

The objective of this research is to prepare modified unsaturated polyester resin(UPR) with good processibility, dimension stability and mechanical properties. In this study, dicyclopentadiene (DCPD) is selected as a modifier and the effect of DCPD content on the curing behavior of the modified UPR is examined via Differential Scanning Calorimetry (DSC) and Rheometrics Dynamic Analysis (RDA) experiments. The results of ¹H NMR identification for the chemical structure of modified UPR show that the trans-structure of UPR decreases as the DCPD content increases. The curing time necessary to reach peak maximum in DSC during the curing reaction lengthens as the stereo obstacles formed by the binary rings increase.     

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