Self-extinguishing and transparent epoxy resin modified by a phosphine oxide-containing bio-based derivative

A phosphine oxide-containing bio-based curing agent was synthesized by addition reaction between furan derivatives and diphenylphosphine oxide.The molecular structure of the as-prepared bio-based curing agent was confirmed by Fourier transform infrared spectroscopy and nuclear magnetic resonance spectroscopy.Dynamic mechanical analysis results indicated that with the increase of bio-based curing agent content,the glass transition temperature of epoxy/bio-based curing agent composites decreased,which was related to the steric effect of diphenylphosphine oxide species that possibly hinder the curing reaction as well as the reduction in the cross-linking density by mono-functional N-H.By the addition of 7.5 wt-%bio-based curing agent,the resulting epoxy composite achieved UL-94 V-0 rating,in addition to limiting oxygen index of 32.0 vol-%.With the increase of content for the bio-based curing agent,the peak of heat release rate and total heat release of the composites gradually decreased.The bio-based curing agent promoted the carbonization of the epoxy matrix,leading to higher char yield with good thermal resistance.The high-quality char layer served as an effective barrier to retard the diffusion of decomposition volatiles and oxygen between molten polymers and the flame.This study provides a renewable strategy for fabricating flame retardant and transparent epoxy thermoset.

Synthesis and Properties of Novel Polyimide Fibers Containing Phosphorus Groups in the Side Chain (DATPPO)

A series of polyamic acid copolymers(co-PAAs) containing phosphorous groups in the side chains were synthesized from [2,5-bis(4-aminophenoxy) phenyl] diphenylphosphine oxide(DATPPO) and 4,4′-oxydianiline(ODA) with 3,3′,4,4′-biphenyltetracarboxylic dianhydride(s-BPDA) through the polycondensation in N,N′-dimethyacetamide(DMAc). The co-PAA solutions were spun into fibers by a dry-jet wet spinning process followed by thermal imidization to obtain co-polyimide(co-PI) fibers. FTIR spectra and elemental analysis confirmed the chemical structure of PI fibers. SEM results indicated that the resulting PI fibers had a smooth and dense surface, a uniform and circle-shape diameter. The thermogravimetric measurements showed that with the increase of DATPPO content, the resulting PI fibers possessed high decomposition temperature and residual char yield, indicating that the PI fibers had good thermal stability. The corresponding limiting oxygen index(LOI) values from the experiment results showed that the co-PI fibers possessed good flame-retardant property. Furthermore, the mechanical properties of the co-PI fibers were investigated systematically. When the DATPPO content increased, the tensile strength and initial modulus of the co-PI fibers decreased. However, the mechanical properties were improved by increasing the draw ratio of the fibers. When the draw ratio was up to 2.5, the tensile strength and initial modulus of the co-PI fibers reached up to 0.64 and 10.02 GPa, respectively. The WAXD results showed that the order degree of amorphous matter increased with increased stretching. In addition, the SAXS results displayed that valuably drawing the fibers could eliminate the voids inside and lead to better mechanical property. WAXD revealed that the orientation of the amorphous polymer influenced the mechanical properties of the fibers.

Highly active bifunctional salenTi(Ⅳ) catalysts for asymmetric cyanosilylation of aldehydes and TMSCN

A novel enantiopure salen ligand bearing a diphenylphosphine oxide on the 3-position of one aromatic ring was synthesized and combined with Ti（Oi-Pr）_4 as a monometallic bifunctional catalyst for asymmetric cyanosilylation reaction of aldehydes with tnmethylsilyl cyanide（TMSCN）.The catalyst system exhibited excellent activity and moderate enantioselectivity.The addition of TMSCN to 4-nitrobenzaldehyde in the presence of 1 mol%catalyst loading could complete within 10 min at ambient temperature. An intramolecularly cooperative catalysis was observed in this system wherein the central metal Ti（Ⅳ） is suggested to play a role of Lewis acid to activate aldehydes while the appended diphenylphosphine oxide worked as Lewis base to activate TMSCN.