生物柴油抗氧剂的研究现状及趋势

作为石化柴油的替代燃料,生物柴油在世界范围内得到广泛应用。生物柴油的不饱和结构决定了生物柴油在存贮过程中的氧化安定性比石化柴油要差。在氧化降解过程中生成氢过氧化物,以及可溶性聚合物等二级氧化产物,并对发动机造成不同程度的损害。添加抗氧剂是一种提高生物柴油的氧化安定性的有效方法。本文对生物柴油抗氧剂的研究现状进行了综述,并对生物柴油抗氧剂的发展趋势作了展望。     

Phenothiazine derivatives as new antioxidants for the autoxidation of methyl linoleate and their reaction mechanisms

The effect of new antioxidants, such as phenothiazine derivatives, on the autoxidation of methyl linoleate was evaluated by estimating the induction period using the weighing method. Peroxide values (iodometry and IR), refractive indices, mol wts, and UV and IR spectra were measured to investigate the extent of the autoxidation. The induction period evaluated from the weighing method gives almost the same value as that from the peroxide values. It was shown that some new phenothiazine derivatives are remarkably effective antioxidants, and, besides, the mechanism for the autoxidation of methyl linoleate containing phenothiazine derivatives as antioxidants is probably of the same type as that for the substrate alone. This study also investigated the reaction mechanism of phenothiazine derivative antioxidants by determining the electron spin resonance spectra for the antioxidants in the autoxidation of methyl linoleate. Then, the following mechanism was proposed. That is, within the induction period, these inhibitors hold stable nitroxide radicals (>NO*) in the reaction between the antioxidant amino radical (>N*), produced by the reaction of the antioxidant with ROO* or O₂, and the peroxy radical (ROO*). Besides, the more superior the phenothiazine derivative antioxidant, the more inactive the antioxidant makes oxygen and the peroxy radical for the methyl linoleate autoxidation and also for the antioxidant oxidation. Presented at the 12th World Congress of ISF, Milan, 1974.     

A review on losses and transformation mechanisms of common antioxidants

Antioxidants are considered to be one of the most effective ways to prevent and delay the rancidity of oils and fats, thus play an important role in the processing, packaging, and storage of oils, fats, and oleaginous foods. However, the losses of antioxidants inevitably occur while preventing the rancidity of oils and fats. In this work, the loss pathways and mechanisms of synthetic and natural antioxidants commonly used in oils, fats, and oleaginous foods systems during storage, use, and detection are critically reviewed. The discussion regarding the transformation of antioxidants or antioxidant models in various organic solvent systems is also covered as well as the fate, toxicities, and antioxidative activities of transformation products of antioxidants. At room temperature, antioxidants in oils and fats are mainly lost due to antioxidation with transformation products accumulated. Under thermal (heating and frying) condition, synthetic antioxidants are mainly lost due to volatilization, while natural antioxidants are mainly lost due to transformation. Under frying condition, adsorption also contributes to the losses of antioxidants. This review discusses some possible research directions regarding antioxidants applied in oils, fats and oleaginous foods, which is expected to benefit the use of antioxidants in food industry.     

Transformation products of antioxidants: The role in stabilization mechanisms

Antioxidants acting in polymers by chain-breaking and hydroperoxide decomposing mechanisms are chemically transformed during the stabilization process as a consequence of trapping radicals R^?, RO^? or RO and/or reactivity with hydroperoxides. New chemical compounds with typical structures characteristic of the starting stabilizer are formed stepwise in the polymer mass. Most of these transformation products participate actively in consecutive steps of polymer degradation. Finally observed phenomena depend on the concentration of individual transformation products. Generally, autocooperative effects with starting stabilizers take place. Important data regarding properties of transformation products have been summarized.     

Kinetics of photoperoxidation of arachidonic acid: Molecular mechanisms and effects of antioxidants

The kinetics of photoperoxidation of [1⁻¹⁴C]arachidonic acid (20∶4n−6) at 1.32 mM was studied either with the unsaturated fatty acid alone or in the presence of 10μM of antioxidants and/or inhibitors of eicosanoid metabolism. The photosensitizer used wasmeso-tetraphenylporphine. The time-course of the reactions was followed by ultraviolet spectral analysis, thiobarbituric acid reactivity and high-performance liquid chromatographic analysis of aliquots sampled every 15 min during the 4 h of irradiation. The kinetics of photoperoxidation of 20∶4n−6 can be divided into three main successive steps: (i) monohydroperoxidation, characterized by the appearance of conjugated diene patterns and monohydroperoxidized 20∶4n−6; (ii) secondary oxidation characterized by polyoxygenated products such as dihydroperoxidized 20∶4n−6 possessing conjugated triene patterns; and (iii) the disappearance of conjugated patterns and the oxidative cleavage of the products of the two first steps into aldehydic molecules reacting with thiobarbituric acid. During the first 90 min of irradiation, the mechanism of monohydroperoxidation (step one) is purely or predominantly type II photoperoxidation involving only singlet oxygen. This step was inhibited by β-carotene and by BW755C (3-amino-1-[3-trifluoromethylphenyl]2-pyrazoline). In contrast, the reactions involved in the second and third steps were predominantly type I photoperoxidation involving radical mechanisms. These latter steps were inhibited by β-carotene, BW755C, vitamin E and probucol. Indomethacin and 5,8,11,14-eicosatetraynoic acid did not alter 20∶4n−6 photoperoxidation. Thisin vitro model of lipid photoperoxidation allows the screening of antioxidants in accordance with their singlet oxygen quenching and/or free radical scavenging properties.     

热流道市场发展的新动向和新特点

热流道技术是应用于塑料注塑模浇注流道系统的一种先进技术,是指从注射机喷嘴送往浇口的物料始终保持熔融状态,在每次开模时不需要固化作为废料取出,滞留在浇注系统中的熔料可在再一次注射时被注入型腔。节约原料、降低制品成本的热流道技术已成为塑胶注塑成型工艺的一个热点方向。     

Mechanisms of antioxidant action: Tellurium dithiocarbamates as antioxidants for polypropylene

The tetrakis (dialkyldithiocarbamato)tellurium(IV) complexes are highly effective thermal antioxidants and melt stabilizers for polypropylene and the evidence suggests that they are converted to the bis(dialkyldithiocarbamato)tellurium(II) complexes and the corresponding dithiocarbamoyl disulfides during processing. The Te(IV) complexes are also effective photoantioxidants and their activity increases with increasing processing time. The bischelates are in general less effective when used alone.     

聚丙烯阻燃剂的作用机理及其研究进展

本文综述了聚丙烯阻燃剂的种类和作用机理,并且介绍了聚丙烯阻燃剂的最新研究进展。聚丙烯阻燃剂的发展方向是高效、低烟、无毒、多功能、低成本。     

Synthesis and application of new macromolecular hindered phenol antioxidants of polyamide 6

The two macromolecular antioxidants, P(3,5-di-tert-butyl-4-hydroxy cinnamic acid-alt-N-phenylmaleimide) (PCN) and P(3-butene-1-yl-3,5-di-tert-butyl −4-hydroxyphenyl propionate-alt-N-phenylmaleimide) (PPN) were designed and synthesized via free radical copolymerization. The structures of the resulting PCN and PPN antioxidants were characterized by Fourier transform infrared spectroscopy, nuclear magnetic resonance spectroscopy (¹H NMR), and gel permeation chromatography. In addition, the effect of the two macromolecular antioxidants on the thermal oxidation aging resistance of polyamide 6 (PA6) was studied. According to the analysis of differential scanning calorimetry, thermogravimetric analysis, dynamic mechanical analysis, dynamic viscosity, and the mechanical property of PA6 and its blends, these two types of macromolecular antioxidants protected the molecular chain of PA6 from breaking, protected the crystallization of PA6 and maintained the stability of PA6 crystal form, improved the activation energy of thermal degradation and thermal stability of PA6, enhanced the strength and elasticity of PA6 and maintained the mechanical properties of PA6 during aging to a certain extent.     

The kinetics of autoxidation of methyl linoleate. The effect of added antioxidants and a new method for the evaluation of antioxidants

A new method is described for the evaluation of antioxidants. Oxygen uptake by autoxidizing methyl linoleate both with and without antioxidants is measured in the Warburg apparatus and reaction orders, reaction rate constants, and length of induction periods determined. Tenox's BHT and BHA and Griffith's G-16 are evaluated and compared.     

Development of new,nonabsorbable polymeric antioxidants for use in foods

The metabolic fate of a new, oil soluble antioxidant, selected from a series representing a unique class of phenolic polymers, is discussed together with its activity in unsaturated vegetable oils as compared to butylated hydroxytoluene, butylated hydroxyanisole, and tertiary butylhydroquinone (TBHQ). Using gel permeation chromatography,¹⁴C-radiolabeled polymer was isolated into discrete mol wt fractions and these administered as single oral doses to rats. Results indicate that while monomeric¹⁴C-TBHQ with a mol wt of 166 shows a total absorption of 88.3% of the administered dose, the absorption of polymeric antioxidant is vastly reduced with increasing mol wt; i.e., mol wt 760: 1.5%, mol wt 7300:0.44%, and mol wt 67,000: 0.34%. Functionality tests using the active oxygen method indicate that by increasing the phenolic constituents in the polymer composition the antioxidant activity can surpass that of certain traditional, monomeric food grade antioxidants. Stability tests using thermogravimetric analysis indicate the polymeric antioxidants are not depolymerized in the presence of air at temperatures up to 300 C. Further, the polymers are nonvolatile and under deep frying conditions result in nearly quantitative carry-through of antioxidant in that portion of oil absorbed by the food; a monomeric food grade antioxidant (TBHQ) shows losses due to volatilization. Presented at the AOCS Meeting, Dallas, April 1975.     

High performance films: Review of new materials and trends

This paper reviews some modern aspects and trends in the development of high performance polymer materials and processing technologies providing fabrication of advanced film and film structures. Changes in understanding of technical requirements and properties, along with novel approaches in creating high performance films of various thermoplastic materials, are discussed. The most important groups of polymer materials being used in high performance applications are described.     

外资企业在华新动向

普利司通在华建立轮胎试验场普利司通(中国)投资公司9月22日正式公布,普利司通(中国)轮胎试验研发公司已获得有关部门批准,取得营业执照。普利司通随后将在江苏宜兴建立轮胎试验场,并在中国市场一举投放5款新轮胎。新建的轮胎试验场占地约84万平方米,拥有全长约900米可进行高速性能测试的直线路面以及进行操控稳定性测试的曲线路面等,其注册资本为2000万美元,总投资额为2500万美元,预计2007年6月投入使用,这是该公司在全球的第11个轮胎试验场。普利司通在中国建立轮胎试验场,一方面能够更迅速高效地针对中国市场的新车配套轮胎以及市场零售…