The polymerization mechanism of methylol-functional benzoxazine monomers is reported using a series of monofunctional benzoxazine monomers synthesized via a condensation reaction of ortho-, meta-, or para-methylol–phenol, aniline, and paraformaldehyde following the traditional route of benzoxazine synthesis. A phenol/aniline-type monofunctional benzoxazine monomer has been synthesized as a control. The structures of the synthesized monomers have been confirmed by ¹H NMR and FT-IR. The polymerization behavior of methylol monomers is studied by DSC and shows an exothermic peak associated with condensation reaction of methylol groups and ring-opening polymerization of benzoxazine at a lower temperature range than the control monomer. The presence of methylol group accelerates the ring-opening polymerization to give the ascending order of para-, meta-, and ortho-positions in …

A new class of high‐performance resins of combined molecular structure of both traditional phenolics and benzoxazines has been developed. The monomers termed as methylol‐functional benzoxazines were synthesized through Mannich condensation reaction of methylol‐functional phenols and aromatic amines, including methylenedianiline (4,4′‐diaminodiphenylmethane) and oxydianiline (4,4′‐diaminodiphenyl ether), in the presence of paraformaldehyde. For comparison, other series of benzoxazine monomers were prepared from phenol, corresponding aromatic amines, and paraformaldehyde. The as‐synthesized monomers are characterized by their high purity as judged from ¹H NMR and Fourier transform infrared spectra. Differential scanning calorimetric thermograms of the novel monomers show two exothermic peaks associated with condensation reaction of methylol groups and ring‐opening …

The effect of austenitizing temperature and Cr, Mo and Mn addition on microstructure and mechanical

properties of V microalloyed medium carbon steel has been studied by means of metallography and mechanical

testing. The addition of Cr, Mn and Mo leads to a decrease in yield strength (YS) by approximate 100 MPa in

comparison to the base steel. It is assumed that Mn and Mo increase hardenability by promoting the formation

of bainitic sheaves (BS), i:e: by suppressing the formation of ferrite-pearlite and acicular ferrite (FP-AF). Cr

at the level used in this work is not that e®ective. Presence and packet size of bainitic sheaves decrease

the Charpy V-notch impact energy at 20 ±C (CVN20) in comparison to ferrite-pearlite and acicular ferrite

microstructures.

Hydrodesulfurization (HDS) and Hydrodearomatization (HDA) of a real Straight Run Gas Oil (SRGO) were investigated over CoMo–S sulfide catalyst in a high–pressure fixed–bed integral reactor. The effect of the key process parameters on the quality of product was studied by varying the temperature (200–370°C), pressure (20 to 50 bar) and space velocity (1 to 4.7h-1). Experimental results revealed that HDS,% activity improved up to 81% when the temperature was increased up to 370°C but reduced to 60% with increase of space velocity up to 4.7 h-1. It has been also found that the rate of HDA, % activity enhanced up to 40.6% by increasing pressure up to 50 bar. The Cetane index underwent an increase of 1–3 degrees and gravity increased by 1–1.7° API. The implication of these results on refining industry is that mild hydrotreating of diesel fuels using the single–stage technology will not enable local refineries to produce diesel fuel meeting the current specifications (<15 ppmwt) except with severe/deep once–through desulfurization or two–stage once–through desulfurization with or without splitting the first reactor effluent. Key words: Diesel fuel; hydrodesulfurization; hydrodearomatization; CO–MO–S/ Al2O3 catalyst

Activation energy for static recrystallization estimated in this work of 281kJ/mol is in excellent agreement with previously reported data (both experimental and mdeled) and indicates that difusion of Nb in austenite is most probably the rate controlling process

The influence of vanadium and nitrogen on microstructure and mechanical properties of medium-carbon

steels has been studied by means of metallography and mechanical testing. Vanadium addition to the low

nitrogen steel suppresses the formation of ferrite–pearlite following the low reheating temperatures and microstructure

consists of bainitic sheaves. Increasing nitrogen at the same vanadium level promotes the acicular

ferrite formation. For high reheating temperatures, dominantly acicular ferrite structure in both the low

nitrogen and the high nitrogen vanadium steels is obtained. The results suggest that vanadium in solid solution

promotes the formation of bainite. The effect of nitrogen is related to the precipitation of VN particles in

austenite with high potency for intragranular nucleation of acicular ferrite and to the precipitation of V(C, N)

particles in ferrite with high potency for precipitation strengthening. Addition of both vanadium and nitrogen

considerably increases the strength level, while CVN20 impact energy increases on changing the microstructure

from bainitic ferrite to the fine ferrite–pearlite and acicular ferrite.

The influence of vanadium and nitrogen on microstructure and mechanical properties of

medium-carbon steels has been studied by means of metallography and mechanical testing.

Vanadium addition to the low nitrogen steel suppresses the formation of ferrite-pearlite following

the low reheating temperatures and microstructure consists of bainitic sheaves. Increasing nitrogen

at the same vanadium level promotes the acicular ferrite formation. For high reheating temperatures,

dominantly acicular ferrite structure in both the low nitrogen and the high nitrogen vanadium steels

is obtained. The results suggest that vanadium in solid solution promotes the formation of bainite,

whereas the effect of nitrogen is related to the precipitation of VN particles in austenite with high

potency for intragranular nucleation of acicular ferrite and to the precipitation of V(C,N) particles in

ferrite with high potency for precipitation strengthening. Addition of both vanadium and nitrogen

considerably increases the strength level, while CVN20 impact energy increases on changing the

microstructure from bainitic ferrite to the fine ferrite-pearlite and acicular ferrite.