Epoxy-modified, unsaturated polyester hybrid networks

Thermal Stability, Flammability and Mechanical Performances of Unsaturated Polyester-Melamine Resin Blends and of Glass Fibre-Reinforced Composites Based on Them

A novel blend of unsaturated polyester (UP) resin with an inherently flame-retardant and char-forming melamine formaldehyde (MF) resin has been prepared with the aim of reducing the flammability of the former. MF resin, sourced as a spray-dried resin, was dissolved in diethyleneglycol solvent; the dissolved resin and the UP-MF blend were autocured by heating under conditions normally used for curing UP, i.e., room temperature for 24 h and post-curing at 80 °C for 12-24 h. The cured UP-MF blends, although heterogeneous in nature, were rigid materials having fire performances superior to those of the cured UP alone. The blends also burned, but with a much reduced smoke output compared with that from UP. Although the heterogeneity of the blends helped in improving the fire performances of the blends in terms of the MF domains forming a semi-protective char, acting as thermal barriers for the adjoining UP domains, and hence reducing their thermal degradation, the mechanical properties of composites based on them were impaired. Nevertheless, whilst UP/MF blends may not be suitable for use as matrices in glass-reinforced composites in load-bearing applications, they may lend themselves to applications as fire-retardant gel coats, especially in view of their low-smoke, char-forming attributes.

Modification of Phenol Novolac Epoxy Resin and Unsaturated Polyester Using Sasobit and Silica Nanoparticles

Nanocomposites containing phenol novolac epoxy resin (PNER) were modified by unsaturated polyester resin (UPR) and then reinforced using sasobit and silica nanoparticles at different filler loadings via a multi-step manufacturing procedure. Afterward, effect of sasobit and silica loadings either on mechanical and thermal properties or on morphology of nanocomposites were examined. Results showed that increase in silica nanoparticles loading can improve both thermal and mechanical properties, but increase in silica loading more than 3 wt% can lead to decrease in the mechanical properties. In this case, addition of sasobit along with silica not only can improve the mechanical and thermal properties but also it can lead to improve in dispersion quality and morphology of nanocomposites. Eventually, with affordable and environmentally friendly materials such as sasobit, either production procedure or the overall quality and properties of nanocomposites can be improved.

Modification of the Epoxy Resin Mechanical and Thermal Properties with Silicon Acrylate and Montmorillonite Nanoparticles

In this study we have investigated the effect of montmorillonite with alkyl quaternary ammonium salt that had been doped into the silicon acrylate (AC-Si)/ Epoxy Cresol Novolac (ECN)/ montmorillonite nano composites on structural, mechanical and thermal properties of composite samples. Moreover the effect of increase in weight percentages of fillers at 0.01, 0.02, 0.03 and 0.04 wt% on the amount of Impact and flexural strength had been investigated. Also impact and flexural strength were performed on two different systems namely (a) ECN filled nanoclay and (b) AC-Si ECN filled with nano montmorillonite as a function of clay respectively. By increase in the weight percentage of filler in the context of matrix up to the 0.03 wt%, the amount of flexural and impact strength were increased but by adding filler more that 0.03 wt%, the amount of flexural and impact strength will decrease. The resulting nanocomposites have optimal mechanical properties at 0.03 wt% montmorillonite content. Addition of The AC-Si will increase the interlamellar distance due to better dispersion of the clay within the matrix. Cross section of fracture surfaces that had been shown by SEM micrographs, specifies that, increase in viscosity had caused due to aggregation that is the main cause of fluctuation in samples properties. In addition the produced samples were characterized by X-ray diffraction (XRD) differential scanning calorimetry, Thermal gravimetric analysis, scanning electron microscopy and mechanical testing (impact and flexural).

The Effect of Introducing B and N on Pyrolysis Process of High Ortho Novolac Resin

In this contribution, high ortho novolac resins modified with phenylboronic acid were synthesized. The thermal stability of novolac resins cured with hexamethylenetetramine (HMTA) and chemical states of B and N via a pyrolysis process were studied. For the cured o-novolac modified with phenylboronic acid, the temperature with maximum decomposition rate increased by 43.5 °C, and the char yield increased by 5.3% at 800 °C compared with cured o-novolac. Density functional theory (DFT) calculations show the existence of hydrogen bonding between N of HMTA and H of phenol in modified resin. Thus, N could still be found at high temperature and C=N structure could be formed via a pyrolysis process. B₂O₃ was obtained at 400 °C by the cleavage of B–O–C and B–C bonds and it reduces the oxygen loss which may take part in the formation of carbon oxides in the system. The melting B₂O₃ on the surface of the resin will prevent small molecules and carbon oxides from releasing. Moreover, introducing B into the system helps to decrease the interlayer distance and improve graphite structures via a pyrolysis process.

Biodegradation Study of Nanocomposites of Phenol Novolac Epoxy/Unsaturated Polyester Resin/Egg Shell Nanoparticles Using Natural Polymers

Nanocomposite materials refer to those materials whose reinforcing phase has dimensions on a scale from one to one hundred nanometers. In this study, the nanocomposite biodegradation of the phenol Novolac epoxy and the unsaturated polyester resins was investigated using the egg shell nanoparticle as bioceramic as well as starch and glycerin as natural polymers to modify their properties. The phenol Novolac epoxy resin has a good compatibility with the unsaturated polyester resin. The prepared samples with different composition of materials for specified time were buried under soil and their biodegradation was studied using FTIR and SEM. The FTIR results before and after degradation showed that the presence of the hydroxyl group increased the samples degradation. Also adding the egg shell nanoparticle to samples had a positive effect on its degradation. The SEM results with and without the egg shell nanoparticle also showed that use of the egg shell nanoparticle increases the samples degradation. Additionally, increasing the amount of starch, and glycerol and the presence of egg shell nanoparticles can increase water adsorption.

Thermal and Mechanical Behavior of Hybrid Polymer Nanocomposite Reinforced with Graphene Nanoplatelets

In the present investigation, we successfully fabricate a hybrid polymer nanocomposite containing epoxy/polyester blend resin and graphene nanoplatelets (GNPs) by a novel technique. A high intensity ultrasonicator is used to obtain a homogeneous mixture of epoxy/polyester resin and graphene nanoplatelets. This mixture is then mixed with a hardener using a high-speed mechanical stirrer. The trapped air and reaction volatiles are removed from the mixture using high vacuum. The hot press casting method is used to make the nanocomposite specimens. Tensile tests, dynamic mechanical analysis (DMA) and thermogravimetric analysis (TGA) are performed on neat, 0.2 wt %, 0.5 wt %, 1 wt %, 1.5 wt % and 2 wt % GNP-reinforced epoxy/polyester blend resin to investigate the reinforcement effect on the thermal and mechanical properties of the nanocomposites. The results of this research indicate that the tensile strength of the novel nanocomposite material increases to 86.8% with the addition of a ratio of graphene nanoplatelets as low as 0.2 wt %. DMA results indicate that the 1 wt % GNP-reinforced epoxy/polyester nanocomposite possesses the highest storage modulus and glass transition temperature (Tg), as compared to neat epoxy/polyester or the other nanocomposite specimens. In addition, TGA results verify thethermal stability of the experimental specimens, regardless of the weight percentage of GNPs.

Improving the fracture toughness and the strength of epoxy using nanomaterials--a review of the current status

The incorporation of nanomaterials in the polymer matrix is considered to be a highly effective technique to improve the mechanical properties of resins. In this paper the effects of the addition of different nanoparticles such as single-walled CNT (SWCNT), double-walled CNT (DWCNT), multi-walled CNT (MWCNT), graphene, nanoclay and nanosilica on fracture toughness, strength and stiffness of the epoxy matrix have been reviewed. The Young's modulus (E), ultimate tensile strength (UTS), mode I (GIC) and mode II (GIIC) fracture toughness of the various nanocomposites at different nanoparticle loadings are compared. The review shows that, depending on the type of nanoparticles, the integration of the nanoparticles has a substantial effect on mode I and mode II fracture toughness, strength and stiffness. The critical factors such as maintaining a homogeneous dispersion and good adhesion between the matrix and the nanoparticles are highlighted. The effect of surface functionalization, its relevancy and toughening mechanism are also scrutinized and discussed. A large variety of data comprised of the mechanical properties of nanomaterial toughened composites reported to date has thus been compiled to facilitate the evolution of this emerging field, and the results are presented in maps showing the effect of nanoparticle loading on mode I fracture toughness, stiffness and strength.