Of neat epoxy resin

Figure 14.2. The mechanical properties of 0.5 wt% SWNT/Epoxy composites (a) tensile test of neat epoxy resin (b) tensile test of pristine-SWNT/epoxy ...

FIGURE 9.24 Differential thmnal analysis in air of neat epoxy resin (pure epoxy), a 4-toluenesulfonate/LDH nanocomposite (TS/LDH), and a bis(2-hydroxyethyl)ammonium montmorillonite nanocomposite (30B). The nanoadditive content is 5 wt%. The main exothermic peak observed in the neat epoxy is split in two parts in the LDH nanocomposite. 

Visual examinations of the fracture surfaces (e.g., from bending experiments) of neat epoxy resin (Figure 8) and particulate-filled epoxy resins (Figure 9), especially by SEM methods, can provide detailed information on the... 

Figure 8. Fracture surface of neat epoxy resin from flexural testing. Brittle fracture with smooth areas. ...

Neat Epoxv Resin. Neat epoxy resin (TGDDM/DDS) was found to be a relatively weak emitter of photons, electrons and positive ions. The general shape of all the emission curves consists of a relatively rapid burst, followed by a very low intensity decay which lasts approximately 100 jis. We frequently observed that during... 

Drzal et al. 90) have investigated the effect of interphase modification on interfacial moisture absorption. The fibers used were a surface treated and a surface treated and finished type A carbon fiber in the same epoxy matrix studied previously. Three equilibrium exposure conditions were investigated. 20 °C, 70 °C and 120 °C were selected for moisture equilibration of single fiber samples and for the neat epoxy resin. The interfacial shear strength was measured both in the saturated and the dehydrated cases and compared to the initial dry values. 

The interaction between these films and bulk epoxy resin was assessed by immersing an aluminum mirror coated with an air-dried primer film in a Petri dish filled with the epoxy resin, heating the dish in an oven at 100°C for 1 h, allowing the dish to cool overnight, and then extracting any unreacted material from the surface of the mirror by MEK extraction. Figure 6A is the reflection spectrum of a relatively thick film (ca. 3 / n) of neat DGEBA resin (cast onto polished aluminum from a 3% solution in toluene), and Fig. 6B shows the RAIR spectrum obtained from the mirror that was primed, heated in resin, and extracted. The... 

Figure 6. (A) RAIR spectrum of neat epoxy film (B) RA1R spectrum of primed mirror that was heated in resin, extracted with MEK (C) difference spectrum between (A) and (B).

Figure 14.11. Tensile strength of CNT/Epoxy composites with the 0.5 wt% SWNT loading (a) neat epoxy resin, (b) pristine SWNT/epoxy, (c) cut-SWNT/Epoxy (11).

Fig. 13 is a TTT cure diagram of three systems a neat epoxy resin and the same epoxy modified with two reactive rubbers at the same concentration level. The times to the cloud point, gelation and vitrification are shown for each system. The cloud point is the point of incipient phase separation, as detected by light transmission. The modified system with the longer times to the cloud point and gelation, and the greater depression of Tg, contains the more compatible of the two rubbers. The difference in compatibility could then be used to account for differences in the volume fractions of the phase separated rubber-rich domains and in the mechanical properties of the neat and the two rubber-modified systems. 

Multifunctional POSS, containing four epoxide groups on the periphery, copolymerized with aliphatic diepoxides and an amine-curing agent increased and broadened the Tg, increased the tensile modulus, but lowered the flexural modulus over that of the neat epoxy resin [2] (Fig. 3). 

In one further work on epoxy-POSS, comparative studies were conducted on epoxy/ladderlike polyphenylsilsesquioxane (PPSQ) blends and the associated nanocomposites [2]. The work revealed that, although a decrease in the flexural strength and modulus of epoxy/POSS nanocomposites in comparison to the neat epoxy resin was observed, only flexural strength deteriorated in the epoxy/PPSQ blends compared to the neat epoxy resin. Flexural modulus of epoxy/PPSQ blends was reported to be much higher than that of the epoxy resin and also increased with an increase in POSS content. It was... 

Ea, above and below Tg. Three case studies illustrate the range of applicability of the bending beam setup and factors contributing to the stress state. The first is a comparison of two polymers for interlayer dielectrics PMDA-ODA (pyromellitic acid dianhydride - oxydiamine) and a bis-benzocyclobutene. The second is of a neat epoxy resin commonly used for microelectronics encapsulation (epoxidized ortho-cresol novolac cured with a phenolic novolac). The third is a screen-printable polyimide coating used for protection of the integrated-circuit chip. An outline of our stress model is sketched, and example results are presented. 

Three case studies are examined which illustrate the use of the bending beam stress experiment. The first is a comparison of two polymers for interlayer dielectrics. The second is of a neat epoxy resin commonly used for microelectronics encapsulation. The third is a polyimide coating used for protection of an integrated-circuit chip. 

MMT and EPON-828, the DSC curve (Fig. 17) indicates that the spontaneous clay exfoliation epoxide polymerization occurred at an onset temperature of 229 °C. On the basis of the integrated peak area, the heat of reaction for the composite was 572 J/g. DSC curves for the neat epoxy resin and the pristine [H3N(CH2)n-COOH]+-MMT are shown for comparison in Figs. 18 and 19 respectively. In the absence of a catalyst, self polymerization of the neat resin occurred at a much higher onset temperature of 384 °C but the heat of reaction (611 J/g) was comparable to that observed for the corresponding nanocomposite (572 J/g), when corrected for the presence of clay (572/0.95) or 602 J/g. 

The effects of ceramic particles and filler content on the thermal shock behavior of toughened epoxy resins have been studied. Resins filled with stiff and strong particles, such as silicon nitride and silicon carbide, show high thermal shock resistance, and the effect of filler content is remarkable. At higher volume fractions (Vf > 40%), the thermal shock resistance of these composites reaches 140 K, whereas that of neat resin is about 90 K. The highest thermal shock resistance is obtained with silicon nitride. The thermal shock resistance of silica-filled composites also increases with increasing filler content, but above 30% of volume fraction it comes close to a certain value. On the contrary, in alumina-filled resin, the thermal shock resistance shows a decrease with increasing filler content. 

Pearson and Yee [171] provided further valuable insights. They showed that the GIc of their family of neat epoxies was very low and almost independent of Mc over the wide range that they examined. However, when these epoxies were used as matrix materials and 10% by volume of an elastomer was added as a filler, Gjc increased rapidly and almost linearly with increasing Mc. Consequently, while the unmodified epoxies were all very brittle, the rubber toughenability of these resins increased rapidly with decreasing crosslink density. 

Matrix-dominated physical and mechanical properties of a carbon-fIber-relnforced epoxy composite and a neat epoxy resin have been found to be affected by sub-Tg annealing In an Inert dark atmosphere. Fostcured specimens of Thornel 300 carbon-fiber/Flberlte 934 epoxy as well as Flberlte 934 epoxy resin were quenched from... 

Differential scanning calorimetry was used to measure both the extent of cure as well as the progress of enthalpy recovery in the neat epoxy resin. A Perkin Elmer DSC-2 differential scanning calorimeter equipped with a scannlng-auto-zero unit for baseline optimization was utilized to measure the heat capacity of the... 

Tensile tests were performed on neat epoxy resins In the following conditions as-cast, as-postcured, as-quenched, and aged at decade Increments from 10 to 10 minutes at 140°C In nitrogen while stored In darkness. A summary of the observed resin stress-strain behavior Is shown In Figure 2. As can be seen, the epoxy polymer was found to be extremely sensitive to thermal history. 

Thermal Stability and Conductivity. Thermal degradation temperature of PMMA, PS, and PVA (poly(vinyl alcohol)) nanocomposites shifts up by 10-100°C. During combustion [179], nanoparticles form a network of char layers that retards the transport of decomposition products. The thermal conductivity of epoxy composites is four times higher than that of the neat epoxy resin with 5 wt% loads. 

Rubber is a viscoelastic solid formed by crosslinking a polymer, which is initially a viscoelastic liquid. In spite of this difference there still are some common issues in understanding the physics of the glass temperature and the viscoelastic mechanisms in the softening dispersion (i.e., called the glass-rubber transition zone in Ferry (1980). A case in point can be taken by comparing the viscoelastic behavior of the neat epoxy resin Epon lOOlF (Plazek and... 

When the neat epoxy resin is modified by the incorporation of submicron rubber particles or glass spheres, the fracture energy can be increased by factors of 4-5 at all levels of temperature, as is shown in Fig. 13.41. Moreover, the increase of toughness with temperature is less abrupt. As we demonstrate, these observations represent an almost classical behavior of transformation toughening by crack-tip shielding of a brittle solid (Evans et al. 1986). 

Another example of this type can be given in the case of nitrocellulose solutions (8g RS /2sec. NC/ 100 ml). The viscosity of these solutions in pure chemical solvents increases as in the case of the epoxy resin solutions with increasing resin concentration. Ketones, with lower neat viscosities than comparable esters result in lower solution viscosities (neat viscosity at 25°C in cS of MEK = 0.46, EtAc = 0.51, MiBK = 0.74, -Bu Ac = 0.84). When ketone is used in combination with a non-solvent (e.g. an SPB) or diluent such as toluene, an increase in viscosity can be observed. This increase is rather sharp when coming close to the point where the resin becomes insoluble (Figure 2.23). When a fixed amount of an SBP/toluene blend is used as the diluent, the viscosity of similar solutions decreases with increasing toluene content of the diluent blend (Figure 2.24). 

Figure 9.27 shows the influence of nano-clay incorporation on storage modulus of the epoxy nanocomposites. The increase in percentage of nano-clay in epoxy resin increases the storage modulus up to a certain weight fraction of nano-clay, above which it decreases the modulus, but it is still above the value of neat epoxy matrix. The loss modulus curve shows the variation of glass transition temperature with respect to nanoclay incorporation and the maximum value of glass transition temperature is noted for the clay content of 3 wt% [31]. 

The incorporation of 5 % organically modified sepiolite, which is a microcrystalline-hydrated magnesium silicate, in a bisphenol A-based epoxy resin has no significant effect over the thermal stability of the epoxy resin, due to the poor dispersion of the clay and poor diffusion of the resin between fibres [69]. The effect of attapulgite (magnesium aluminium phyllosilicate) over the thermal properties of hyperbranched polyimides was studied. The presence of this silicate in the nanocomposites significantly improved the thermal stability of the neat polyimide [70]. 

In the case of Ni-La-Fe-O/epoxy nanocomposites, the thermal degradation showed a more complicated behavior than the neat epoxy resin, with two peaks in the 300-475 °C temperature range. Moreover, the thermal stability of the resin decreased in the presence of Ni-La-Fe-0 nanoparticles, due to the fact that these nanoparticles may act as catalysts to degrade the epoxy matrix [76]. 

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