外文翻译原文：不饱和聚酯的热机械性能增韧环氧树脂粘土

Thermo mechanical behaviour of unsaturated polyester toughened epoxyclay hybrid nanocomposites Chinnakkannu Karikal Chozhan JEOL JSM Model 6360). The fractured surface of the samples was coated with platinum before scanning. X-ray diffraction studies X-ray diffraction patterns were recorded at room tempera- ture by monitoring the diffraction angle 2 from 10 to 70 as standard and 0.5 to 10 as low angle on a Rich Seifert (Model 3000) X-ray powder diffractometer. The diffractometer was equipped with a Copper target (= 1.5405 A) radiation using Guinier type camera employed as a focusing geometry and a solid-state detector. Curved nickel crystal used as a monochromator. The step width (scanning speed) used was 2=0.04/min. Results and discussion FT-IR spectroscopy The characteristic IR absorption peaks observed for UP resin is shown in Fig. 1. The strong IR absorption peak due to the C=C stretching of aromatic ring occurred at 1,600, 1,600.8, 1,605 and 1,608.9 cm1(Fig. 1ad). The peak appeared at 3,510.9 cm1indicates the presence of hydroxyl group in UP resin (Fig. 1a). The peaks at 2,961.9, 2,966.3 cm1represent the aliphatic CH stretching Fig. 1 FTIR spectra of a UP resin, b uncured epoxyUP blend (100:15), c uncured epoxyUP blend with the composition of (100:15) taken after heating at 80 C for 3 h, d UP toughened epoxy matrix cured by DDM with the composition of (100:15) and e unmodified epoxy resin 322C.K. Chozhan, et al. of UP and UPepoxy resin (Figs. 1a,c) respectively. An asymmetric stretching of methylene occurs at 2,925.7 cm1 (Fig. 1d). The peaks appeared at 3,404.5, 3,506.1 cm1 indicate the presence of hydroxyl group of epoxy resin (Fig. 1d,e) and the peaks between 920 and 770 cm1 suggest the presence of asymmetric stretching of epoxy resin. The epoxide ring of epoxy resin appears at 914 cm1 which attributes the stretching absorption of CO in the epoxide ring and this absorption clearly disappeared by curing at 120 C (Fig. 1e,d). The network structure formed between UP and epoxy resin shows the reaction of epoxide ring of epoxy resin with the hydroxyl group of unsaturated polyester and is confirmed by the decrease in the intensity of the epoxy band at 914.5 cm1and the hydroxyl band at 3,510 cm1(Fig. 1b,c). An intermolecular hydrogen bonding is formed between the carbonyl group on the polyester and the epoxide ring. The carbonyl group absorption of the polyester linked with epoxide ring is shifted from 1,726.7 to 1,730.4 cm1(Fig. 1a,c). Thermal properties The glass transition temperature (Tg) of unmodified epoxy and UP toughened epoxy systems are presented in Table 1. The value of the glass transition temperature of the epoxy system is decreased, with increasing concentration of UP. This is explained by the chain lengthening and flexibility behavior of unsaturated polyester resin, which in turn decreases the effective crosslink density and accelerates the reaction rate and reduces the curing temperature. This creates excess free volume and chain entanglement in the matrix system and leads to reduction in the values of Tg, since Tg is associated with mobility of the molecule (Table 1) i.e. makes the molecule to move freely. The incorporation of organophilic nanoclay into UP toughened epoxy systems increased the values of Tg 50, 51 whereas the addition of nanoclay into unmodified epoxy decreased the values of Tg. The increase in the values of Tg is due to the presence of cetyltrimethylammonium ions in the gallery region of organo clay in nano scale level which decreased the reaction rate and enhanced the curing temperature 30, 41, 43. This shows the effective crosslinking of organoclay with the UP toughened epoxy and confirmed the formation of nanocomposites. The values of HDT obtained for epoxy, UP toughened epoxy, organophilic nanoclay incorporated epoxy and organophilic nanoclay incorporated UP toughened epoxy systems are presented in Table 1. From Table 1, it is evident that the values of HDT are decreased with increasing UP concentration, due to the presence of flexible ether (O) group formed during the reaction between hydroxyl group of UP resin and the epoxide group of DGEBA resin. This is due to the deviation of stoichiometric ratio of epoxy ring to active hydrogen, which can be contributed by DDM and UP resin. With increasing UP concentration, a decrease in the crosslinking density of the epoxy system would result, leading to a decrease in HDT. Besides, the IPN structures of crosslinked epoxy and crosslinked UP, the crosslinking density of the epoxy system would also be decreased (due to the interaction of crosslinked UP) during the cure reaction which also causes for a decrease in HDT. However, increasing trend in HDT values is observed for organophilic nanoclay filled epoxy and organoclay filled UP toughened epoxy systems. This is due to the presence of intercalated nano structure of organoclay in the epoxy matrix system. The incorporation of organo clay upto 5% into epoxy resin makes an efficient interaction and consequent enhancement in crosslink density induced by the presence of cetyltrimeth- ylammonium ions and in turn improves the values of Tg and HDT. The enhancement in the values of Tg and HDT confirmed the efficient compatibility between an organoclay and epoxy resin 52. Thermogravimetric analysis The incorporation of UP into epoxy resin improved thermal stability and enhanced the degradation temperature accord- ing to the rise in percentage concentration (Table 2). The Table 1 Thermal and water absorption behavior of hybrid UPepoxy nanocomposites Epoxy/UP/clay composition Heat distortion temperature (C) Glass transition temperature (C) Water absorption (%) 100/00/001551660.1232 100/05/001371490.1197 100/10/001311420.1129 100/15/001291390.1068 100/00/011411530.1127 100/00/031501610.1021 100/00/051541650.0562 100/10/011351480.1103 100/10/031461570.1005 100/10/051501610.0539 Thermo mechanical behaviour of hybrid nanocomposites323 presence of UP molecular segments in the epoxy system delays the degradation process and high thermal energy is required to attain the same percentage weight loss than that required for unmodified epoxy system. The delay in degradation caused by the UP moiety is attributed to its crosslinked network structure of UPepoxy system. The degradation temperature of organophilic clay incorporated epoxy systems and organophilic clay incorporated UP toughened epoxy systems is increased with increasing concentration of clay. From Table 2, it is evident that the degradation temperature increased with increasing organo- clay concentrations, as observed in the case of UP toughened epoxy systems and this is due to the plasticiza- tion effect of crosslinked epoxy networks formed between clay layers by hydrocarbon chains of cetyltrimethylammo- nium ions present in the organophilic nanoclay 54, 55. Further this enhancement on thermal stability is due to the presence of hard clay nanolayers which act as barriers to minimize the permeability of volatile degradation products from the UPepoxy clay nanocomposites. Mechanical properties The observed values for tensile and flexural properties of unmodified epoxy, UP toughened epoxy, organoclay filled epoxy and UP toughened epoxy are presented in Table 3. The introduction of 5, 10 and 15% UP (by wt) into epoxy resin decreased the tensile strength (3.2, 10.1 and 12.5%) and flexural strength (3.7, 10.4 and 12.9%) when compared with those of unmodified epoxy resin. This is due to the formation of chain entanglement in the UPepoxy matrix system. The incorporation of 1, 3 and 5% (by wt) organoclay into the epoxy resin increased the tensile strength (9.3, 18.3 and 24.7%) and flexural strength (7.9, 17.6 and 23.5%), with increasing concentrations due to the formation of nanocomposites 56, 57. Similarly, the introduction of both organoclay and UP into epoxy resin improved the values of tensile strength and flexural strength according to their percentage content (Table 3). The values of tensile strength and flexural strength of UPepoxy are increased with increasing organoclay content. The intro- duction of 1, 3 and 5% (by wt) organoclay into 10% UP toughened epoxy resin increased the tensile strength (15.4, 24.2 and 30.6%) and flexural strength (14.2, 25.3 and 34.3%) with increasing clay content. Like tensile and flexural strength, the values of tensile and flexural modulus also follow a similar trend (Table 3). The incorporation of 5, 10 and 15% UP into epoxy resin enhanced the impact strength 6.5, 15.2 and 21.2% accord- ing to the percentage content of UP. This is due to the formation of entangled network structure developed due to unsaturated active sites of polyester toughened epoxy system. Further, the incorporation of organoclay into both epoxy and UPepoxy systems also increased the impact Table 3 Mechanical properties of hybrid UPepoxy nanocomposites Epoxy/UP/Clay Composition Tensile Strength (MPa) Tensile Modulus (MPa) Flexural Strength (MPa) Flexural Modulus (MPa) Impact Strength (J/m) 100/00/0065.762,752.639114.541,932.431104.73 100/05/0063.632,655.729110.221,860.628111.53 100/10/0059.142,464.130102.631,720.732120.72 100/15/0057.552,398.94099.751,680.627126.91 100/00/0171.872,989.531123.542,124.432113.62 100/00/0377.753,221.640134.652,292.035124.83 100/00/0581.943,447.837141.432,407.533132.52 100/10/0175.823,146.229130.832,217.329124.22 100/10/0381.653,450.431143.532,462.828132.23 100/10/0585.833,671.636153.842,591.825141.41 Table 2 TGA data of hybrid UPepoxy nanocomposites Epoxy/UP/clay composition Initial decomposition temperature (C) Temp. at characteristic weight loss (C)Residue (%) 798 C 20%40%60% 100/00/0035537239342020.4 100/10/0036439141144228.2 100/00/0336739442045629.8 100/10/0337340242747433.2 324C.K. Chozhan, et al. strength due to the flexibility imparted by the plasticization effect of organoclay (Table 3). The introduction of 1, 3 and 5% organoclay into 10% UP toughened epoxy resin increased the impact strength to 18.6, 26.3 and 35.1% respectively. While comparing the overall improvement attained in the mechanical properties, it is found that there was a decrease in the values (around 13%) of tensile strength/modulus and flexural strength/modulus of UP toughened epoxy systems with 21% enhancement in the values of impact strength. However, the loss occurred in the values of tensile and flexural strength/modulus was recov- ered by the addition of organo clay into the UPepoxy matrix system. The UP toughened epoxyclay nanocompo- sites exhibit about 34% improvement in both the values of tensile and flexural strength/modulus and 35% in impact strength due to the formation of nanocomposites. Dynamic mechanical analysis The dynamic mechanical analysis (DMA) curves of unmodified epoxy, unsaturated polyester toughened epoxy, organoclay filled epoxy and unsaturated polyester tough- ened epoxy clay nanocomposites are presented in Figs. 2 and 3. The loss tangent is a sensitive indicator for crosslinking. The observation from Fig. 2 reveals that the tan peak corresponding to the values of Tg shifted towards the lower temperature (from 166 to 157 C) by the addition of 3% clay into 10% UP toughened epoxy nanocomposites compared to unmodified epoxy resin. Since the relaxation peak height is associated with molecular mobility, it was observed that the intercalation Fig. 3 Variation of storage modulus as a function of temperature, a unmodified epoxy, b epoxy with 10% UP, c epoxy with 3% clay, d epoxy/10%UP/3% clay nanocomposites systems Fig. 4 SEM photographs of unsaturated polyester toughened epoxy clay nanocomposites a modified epoxy, b 10% UP toughened epoxy, c 3% organo clay filled epoxy, d 10% UP toughened and 3% organo clay filled epoxy Fig. 2 Variation of tan as a function of temperature a unmodified epoxy, b epoxy with 10% UP, c epoxy with 3% clay, d epoxy/10%UP/ 3% clay nanocomposites systems Thermo mechanical behaviour of hybrid nanocomposites325 of the polymer molecules between the clay layers had greatly reduced their molecular mobility 58, 59 and in turn decreased the intensity of tan . The clay addition has the considerable effect in the stiffness behavior of the nanocomposites which affects the dynamic mechanical behaviour of the nanocomposites. The clay addition increasesthestoragemodulus() (Fig. 3). Below Tg, the stor- age modulus of the nanocomposites is increased by 24.3 % (from 3072 to 3820 MPa) and above Tg, it is increased by 35.1 % (from 104.7 to 141.4 MPa). Hardness The value of hardness of an unmodified epoxy system was found to be 83. The value of hardness for epoxy system decreased with the incorporation of an increased concen- tration of UP. The values of hardness for 5, 10 and 15% UP toughened epoxy systems were decreased to 79, 75 and 72 respectively due to the flexible ether group formed between the reaction of hydroxyl group of unsaturated polyester resin and the epoxide group of DGEBA resin. With increasing UP concentration, the crosslinking density of the epoxy system would decrease. Due to the interaction of crosslinked UP during the cure reaction, the crosslinking density of the epoxy system would be decreased by the IPN structures of crosslinked epoxy and crosslinked UP, whereas a significant improvement was observed in the values of hardness when 10% UP toughened epoxy system was reinforced with 1, 3 and 5% organophilic nanoclay and their corresponding values were 88, 93 and 96. This confirms the effective network formation. Water absorption The incorporation of unsaturated polyester into epoxy resin decreased the percentage water uptake, according to the percentage concentration (Table 1) due to its inherent hydrophobic nature. Further, the incorporation of organo- philic clay into both epoxy and unsaturated polyester toughened epoxy systems also reduced the percentage water uptake due to the fact that the reduction in permeability behavior influenced by the nanocomposites structure. Morphology TheSEMmicrographsoffracturedsurfacesoftheunmodified epoxy system indicated smooth, glassy and homogeneous microstructures (Fig. 4a,b). This supports brittle nature and poor impact strength of unmodified epoxy system. The micrograph of the fractured surface of UP toughened epoxy system shows a homogeneous structure. The homogeneous Fig. 5 XRD patterns of a organo modified MMT clay, b epoxyclay (100:1), c epoxyclay (100:3), d epoxy-clay (100:5), e epoxyUP clay (100:10:1; f) epoxyUPclay (100:10:3) and g epoxyUPclay (100:10:5) Fig. 6 XRD patterns of a organo modified MMT clay, b epoxyclay (100:1), c epoxy clay (100:3), d epoxyclay (100:5), e epoxyUPclay (100:10:1), f epoxyUP clay (100:10:3) and g epoxy UPclay (100:10:5) at low angle 326C.K. Chozhan, et al. morphology observed for UP toughened epoxy system confirms the chemical interaction between unsaturated polyester and epoxy resin. This further supports that there is no phase separation between the two components. Figure 4c and d show the SEM micrographs of the organoclay filled hybrid epoxy and UPepoxy nanocompo- sites. The organoclay filled UP toughened epoxy systems also exhibit homogeneous morphology indicating the inter- calation of polymer molecules into clay structures. The efficient adhesion arises due to the influence of intermolec- ular specific attraction between cetylammonium ions mod- ified clay and UPepoxy matrix systems and hence leads to the formation of nanocomposites. X-ray diffraction studies X-ray diffraction measurements were made to evaluate the spacing between the silicate layers in the organoclay filled hybrid epoxy nanocomposites. Braggs Law (n=2dsin) was used to compute the crystallographic spacing. The XRD patterns of hybrid UPepoxy nanocomposites suggest the formation of intercalated nano hybrids (Fig. 5 and 6). This is due to the compatibility of epoxy resin with the layered silicates, and the epoxy chain penetrates into the gallery and expands the nano size to some extent 52, 53, 59, while the layered structure of the silicate is still in registry. When 2=1070 (the angle between the dif- fracted and incoming X-ray waves), the d001spacing of the UPepoxy nanocomposites is in nano level. The nanosize of organoclay is 0.260.45 nm. For epoxyclay hybrid nanocomposites, the nanosize is 0.750.81 nm. Similarly, the nanosize of epoxyUPclay hybrid nanocomposites is 0.740.78 nm. At low angle 2=0.510, the nanosize of organoclay is 2.543.35 nm. For epoxyclay nanocompo- sites, the nanosize is 2.564.07 nm. The nanosize of epoxyUPclay nanocomposites is 2.584.13 nm. The above data clearly explains that the incorporation of clay influence the formation of UP toughened epoxyclay nanocomposites. The increase in interplanar spacing of the gallery between the nanosheets is caused by the penetration of a large amount of UPepoxy resin into the gallery and expansion of the gallery. The dispersion of these nanosheets in the epoxy resin is attributed for its improved thermo- mechanical characteristics. Conclusions The unsaturated polyester toughened epoxy matrix systems with varied concentration were developed. The thermal properties namely Tg, HDT of unsaturated polyesterepoxy systems have been compared with those of unmodified epoxy systems. The reduction in the values of Tg for unsaturated polyester toughened epoxy system is due to the flexibility imparted by unsaturated polyester to the epoxy matrix. The mechanical studies inferred that the incorporation of unsaturated polyester into epoxy resin enhanced the values of impact strength. The fractured surfaces of the unsaturated polyester toughened epoxy system indicated the presence of homogeneous microstructure. The organophilic MMT clay filled epoxy and unsaturated polyester toughened epoxy nanocomposites were also prepared and the formation hybrid nanocomposites were ascertained from XRD and SEM studies. Homog