For the epoxy encapsulant cured by diethanolamine, optimal epoxy/hardener stoichiometry could hardly be predicted due to the complex curing mechanisms. In this paper, the influences of stoichiometry were investigated by FTIR, DMA and tensile testing. The results showed that stoichiometry has a dominating effect on both T g and tensile properties of the cured epoxy. The largest T g , highest crosslink density as well as excellent ductility appeared in epoxy encapsulant cured with 14 wt% diethanolmine. When the content of diethanolamine was lower than 14 wt%, epoxy encapsulants showed smaller glycidyl conversion even with long-duration post-cure. Larger tensile strength and modulus were also observed in the glycidyl-rich epoxies, which could be explained by anti-plasticization effect. The amine-rich epoxy, however, had extremely high glycidyl conversion and presented brittle tensile behavior. A diethanolamine content of 12-14 wt% for the epoxy encapsulant is suggested to obtain optimal thermal and tensile properties.

Hexamethylolmelamine was used as a cross-linking agent to graft 3-(dimethylphosphono)-N-methylolpropionamide (MDPA) onto Lyocell fibers in a posttreatment process to reduce flammability. The effects of processing conditions on the mechanical properties and P content of the fibers were examined. The results show that increasing the MDPA concentration, microwave treatment time, baking temperature, and baking time increases the P concentration in the fibers, although the mechanical properties of the fibers are reduced to varying degrees. The optimal processing conditions comprise a 40% MDPA concentration, a 320 W microwave treatment for 3 minutes, and baking at 160 C for 5 minutes. Under these conditions, flame-retardant Lyocell fibers with a breaking strength of 2.47 cNÁdtex À1 and a limiting oxygen index of 34.6% were obtained, which meet the performance requirements for textile fibers. Thermogravimetric data indicate that the residual fiber mass after heating increased from 4.7% before treatment to 21.5% after treatment. There was only a minimal change in the hygroscopicity of the treated Lyocell fibers. In addition, after 30 washes, the limiting oxygen index was decreased to 26.5% while maintaining a good flame-retardant effect.

Two flame retardants, melamine polyphosphate (MPP) and modified melamine cyanurate (MCA), were examined and added to a cellulose solution to fabricate flame-retardant Lyocell fibers Lyocell-MPP and Lyocell-MCA, respectively, via dry-wet spinning. Compared with the non-modified Lyocell fiber (without flame retardant), the flame-retardant fibers produced a higher amount of carbon residue during combustion, whereas the heat release capacity, peak heat release rate, and total heat release decreased, indicating that the flame-retardant fibers present a lower fire risk. The limit oxygen index values of Lyocell-MPP and Lyocell-MCA were 26.5% and 27.1%, respectively, complying with the flame-retardant standard. The crystallinity and mechanical properties of the flame-retardant fibers decreased relative to those of the nonmodified Lyocell fiber. Furthermore, the wearability of the flame-retardant fibers was studied-both flame-retardant fibers displayed good washing resistance properties and improved hygroscopicity but a lower dyeing performance than the non-modified Lyocell fiber.

The change of dielectric properties of epoxy/anhydride systems during eleven months storing was investigated. Test systems were bisphenol-A epoxy cured by different content of methyl-hexahydrophthalic anhydride with a slow cooling process across Tg range included in their curing procedure to reduce residual stress. The results showed all the systems’ dielectric constant and dielectric loss angle tangent had a trend of down then up. The highest decreasing amplitudes were about 4% and 10% respectively. Possible explanations for these phenomena were proposed, and then some preliminary investigations were carried out like DSC and IR.