Antioxidant synergism between butylated hydroxyanisole and butylated hydroxytoluene

Decay of the 2,6-di-tert-butyl-4-methylphenoxy radical [butylated hydroxytoluene (BHT)-radical] in the presence of butylated hydroxyanisole (BHA) was investigated in 1,2-dimethoxyethane with or without triethylamine. BHT-radical was conveniently generated by dissociation of its unstable dimer in solution. The products were BHT, 3,3′-di-tert-butyl-5,5′-dimethoxy-2,2′-dihydroxybiphenyl (BHA-dimer), 2,6-di-tert-butyl-p-quinone methide (QM), 1,2-bis(3,5-di-tert-butyl-4-hydroxyphenyl)ethane, and 3,3′,5,5′-tetra-tert-butyl-4,4′-stilbenequinone. The reaction without added triethylamine gave larger quantities of the last two products and BHA (recovery), whereas the reaction with it provided larger quantities of the first two products. The marked difference in the product distribution can be accounted for by a series of reactions including reversible dehydrogenation of BHA with BHT-radical, which generates 2-tert-butyl-4-methoxyphenoxy radical (BHA-radical) and BHT, reversible dimerization of BHA-radical, which affords an intermediarybis(cyclohexadienone), and spontaneous and base-catalyzed prototropic rearrangement of the intermediate into BHA-dimer. Products of coupling between BHT-radical and BHA-radical were not obtained. BHA was found to undergo facile acid-catalyzed addition to QM, providing two isomericbis(hydroxyphenyl)methanes. The results help to elucidate the mechanism of antioxidant synergism between BHA and BHT and may suggest that the synergism can be affected by base or acid.     

Toxicology and biochemistry of butylated hydroxyanisole and butylated hydroxytoluene

Butylated hydroxyanisole and butylated hydroxytoluene are used extensively as food antioxidants. It is estimated that man consumes ca. 0.1 mg/kg body wt daily of these antioxidants. At levels 500 times this level (50 mg/kg/day), both butylated hydroxyanisole and butylated hydroxytoluene appear to be free of any obviously injurious effects. However, at larger doses (500 mg/kg/day), both butylated hydroxyanisole and butylated hydroxytoluene result in certain pathological, enzyme, and lipid alterations in both rodents and monkeys, and butylated hydroxytoluene, in some cases, has been reported to have certain teratogenic and carcinogenic effects upon rodents. These alterations appear to differ markedly between rodents and monkeys, apparently as a result of differences which exist in the metabolism and excretion of butylated hydroxyanisole and butylated hydroxytoluene by these two species. However, in both animal species, the alterations appear to be physiological responses which are reversible upon removal of butylated hydroxyanisole and butylated hydroxytoluene from the diet. Long term chronic ingestion of butylated hydroxyanisole and butylated hydroxytoluene may be beneficial in sparing vitamin E and in modifying the acute toxicity of a number of mutagenic and carcinogenic chemicals.     

Equilibrium vapor pressure of butylated hydroxyanisole and butylated hydroxytolune in high temperature oil solution

The equilibrium partial pressure of butylated hydroxyanisole and butylated hydroxytoluene above their dilute oil solution in the frying temperature range (170–220 C) was determined. The system was found to follow Henry’s law and to have an activity coefficient ranging, respectively, from 0.038–0.045 and from 0.036–0.042 (averages 0.042 and 0.039) for butylated hydroxyanisole and butylated hydroxytoluene. The extremely narrow ranges of γ suggest that the dominant effect of temperature upon the Henry coefficient, H, is through the vapor pressure of the pure substance. The equations for H (in mm Hg) as function of the absolute temperature T (in K) when antioxidiant concentration expressed as molar fraction are: H = 1.26 × 10⁸ exp (−8.03 × 10³/T) for butylated hydroxyanisole, and H = 1.55 × 10⁷ exp (−7.02 × 10³/T) for butylated hydroxytoluene.     

Studies on the antioxidants: XI. oxidation products of concomitantly used butylated hydroxyanisole and butylated hydroxytoluene

The effects of antioxidants used concomitantly were studied for their contribution to the autoxidation process and for the function-al mechanism of the antioxidating process. In this study, an equal mixture of butylated hydroxyanisole (BHA) and butylated hydroxy-toluene (BHT) in benzene was irradiated with ultraviolet rays and the chemical structures and antioxidant activities of the resulting oxides were derived. The chemical changes of the substrates and oxides were followed quantitatively by gas chromatography. The resulting oxide was confirmed to be 3,3′,5′-tri-tert-butyl-5-methoxy-2,4′-dihydroxydiphenyl methane, which was a dehydrogenated dimer of BHA and BHT. The stability study on this compound by AOM showed its strong activity as an antioxidant on lard and soybean oil.     

Acrylic nonaqueous dispersion using butylated melamine-formaldehyde resin as dispersant

A series of acrylic nonaqueous dispersions were prepared by using various kinds of butylated melamine–formaldehyde (BMF) resins as dispersant. The functional group composition of BMF to form stable dispersion was butoxy group more than 13 mol/BMF 1 mol, and methylol group ranged from 1 to 2.5 mol/BMF 1 mol. It is concluded that the anchoring of BMF to acrylic copolymer was due to the formation of covalent bond between methylol group in BMF and hydroxy group in acrylic copolymer.     

Synthesis and evaluation of high-temperature properties of butylated graphene oxide composite incorporated SBS (C4H9-GO/SBS)-modified asphalt

Graphene nanoparticles (GNPs) added styrene-butadiene-styrene (SBS)-modified asphalt suffers from serious compatibility and agglomeration problems. To tackle these problems, in this study, graphene oxide (GO) was mixed with bromobutane to synthesize butylated graphene oxide (C₄H₉-GO) composite, which was in turn compounded with SBS for the preparation of C₄H₉-GO/SBS-modified asphalt. C₄H₉-GO/SBS-1.0-modified asphalt exhibited the best performance in terms of 11.4% increased softening point, 19.3% increased ductility, and 10.2% reduction in penetration as compared to 5% SBS-modified asphalt. Dynamic shear rheometer and multistress creep recovery tests showed that at 1.0% C₄H₉-GO contents, C₄H₉-GO/SBS composite-modified asphalt exhibited the best high-temperature performance and low stress sensitivity. Microscopic characterization of C₄H₉-GO via Fourier transform infrared spectroscopy, X-ray diffraction, and Raman spectroscopy revealed successful bonding between  C₄H₉ and GO, increasing interlayer spacing in GO. Atomic force microscopy and scanning electron microscopy analysis showed the superior elasticity of C₄H₉-GO than GNPs. Differential scanning calorimetry analysis indicated that C₄H₉-GO sheets can be stabilized by SBS through π–π stacking with the polystyrene chains. This study awarded to the preparation of novel C₄H₉-GO/SBS-modified asphalt with superior mechanical property can be deemed of potential value and applications in construction and highway industries. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 48231.