测氧法研究受阻酚抗氧剂的抗氧化活性及反应动力学

采用测氧法考察了4种市售受阻酚抗氧剂的抗氧化活性,同时对其清除ROO·反应进行了动力学分析。结果表明:4种受阻酚抗氧剂对ROO·均具有良好的清除作用,并且抗氧化活性随着酚羟基浓度增加而增大。在同等的酚羟基浓度下,抗氧剂的抑制速率常数kinh值从大到小的顺序为抗氧剂1098、抗氧剂BHT、抗氧剂1010、抗氧剂1076。抗氧剂的抗氧化活性与功能基团的个数和对位取代基的供电性密切相关,酚胺复合型抗氧剂体现出更高的抗氧化活性。     

聚合型受阻酚抗氧剂的合成及应用

研究了以对甲酚为主要原料合成聚合型受阻酚抗氧剂的工艺。结果表明，树脂缩合反应条件是对甲酚与双环戊二烯为3：1～1．25，ZnCl2催化剂为对甲酚质量分数的2．0％，反应温度为75～80℃，双环戊二烯滴加时间为2h。烷基化反应温度为70～75℃，H2S04催化剂为缩合树脂质量分数的2．0％。制得的聚合型受阻酚抗氧剂产品对聚氨酯泡沫用聚醚2802具有较好的抗氧化性，起燃温度达224℃。     

多乙烯多胺桥联受阻酚类抗氧剂的合成及其清除DPPH·性能

以二乙烯三胺和三乙烯四胺为桥联基,β-(3,5-二叔丁基-4-羟基苯基)丙酰氯为抗氧化功能基团,通过酰胺化缩合反应合成了两类具有不同对位桥联基团的受阻酚类抗氧剂。采用傅里叶红外光谱和核磁共振氢谱证实了合成的多乙烯多胺桥联受阻酚类抗氧剂的化学结构。DPPH法研究了多乙烯多胺桥联受阻酚类抗氧剂清除自由基的性能,并探索了酚羟基个数和对位桥联基结构对受阻酚类抗氧剂清除自由基性能的影响。结果表明,多乙烯多胺桥联受阻酚类抗氧剂具有良好的清除DPPH·能力,且随着抗氧剂分子中酚羟基个数的增加,清除DPPH·的活性增加,分子中含有4个酚羟基的三乙烯四胺受阻酚类抗氧剂的抗氧化效率（AE）达到2.65×10^-2 L/(mol·s)。对位桥联基结构对受阻酚类抗氧剂清除DPPH·能力有较大影响,季戊四醇为桥联基的受阻酚类抗氧剂1010清除DPPH·能力最强,其抗氧化效率（AE）为3.08×10^-2L/(mol·s);乙二胺为核的1.0代树枝状受阻酚类抗氧剂清除DPPH·能力最弱,其抗氧化效率（AE）为2.60×10^-2 L/(mol·s)。     

受阻酚类抗氧剂结构与其抗氧化性能的影响关系

选取了3种酚羟基个数不同的受阻酚类抗氧剂为研究对象,通过性能测试、氧化诱导温度测试以及羰基指数测试等对添加抗氧剂后合成的聚乙烯进行对比分析,考察抗氧剂结构对聚乙烯性能的影响。结果表明,虽然受阻酚类抗氧剂中酚羟基的个数增多可以提高抗氧剂的抗氧化效果,但耐老化性能变弱,因此优选适宜的酚羟基个数对于提升受阻酚类抗氧剂的抗氧化性能十分必要。     

受阻酚抗氧剂对NBR/WCB共混胶耐热老化性能的影响

研究了抗氧剂2-叔丁基-6-(3-特丁基-2-羟基-5-甲基苯基)-4-甲基苯酚丙烯酸酯(简称GM)、抗氧剂264和抗氧剂2246对NBR/WCB共混胶的硫化特性、力学性能和耐热老化性能的影响,并通过TG分析表征NBR/WCB共混胶的耐热稳定性。结果表明,与抗氧剂264和抗氧剂2246相比,抗氧剂GM对NBR/WCB共混胶具有防止焦烧、加快硫化速度和软化胶料的作用。添加抗氧剂GM的共混胶比加入抗氧剂264和2246的共混胶具有更优异的耐热老化性能。TG分析表明,在3种抗氧剂中,加入抗氧剂GM的NBR/WCB共混胶的耐热稳定性最高。     

受阻胺抗氧剂对PA6工业丝热氧老化性能的影响

通过尼龙6(PA6)工业丝和添加质量分数0.5%的受阻胺抗氧剂N,N'-二(2-萘基)对苯二胺(DNP)的尼龙6(PA6-DNP)工业丝的热性能和在热氧化过程中的力学性能的对比,研究了DNP对PA6工业丝的性能影响.结果表明:DNP不改变PA6工业丝的熔融温度,但会引起晶型的变化,对在氮气氛围下的热分解影响不大,对氧气...     

Application of hindered piperidine amine and/or tertiary amine in the modification of polyamide 6

PA 6 resin was produced in a hydrolytic‐polymeric process in which ε‐caprolactam was polymerized in the presence of water as initiator, isophthalic acid and benzoic acid as chain regulators, by polymerizing caprolactam in the presence of 7.5% by weight of water, 0.2% by weight of isophthalic acid, 0.1% by weight of benzoic acid, each percentage being based on caprolactam. By adding hindered piperidine amine and/or tertiary amine to the polymeric system, the effects of additives on the polymer were studied. The results showed that: the addition of 0.1 ～ 0.2% additives can improve the melt stability of polyamide 6; the addition of 0.2% additives can protect mechanical properties of polyamide 6 fibers after exposure to high temperature; and the addition of 0.05 ～ 0.25% additives can increase the amino end group content of polyamide 6 and thereby increase the dyeability of polyamide fibers. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 2489–2493, 2004     

Photooxidation of benzil groups in the presence of hindered amine stabilizers in the polystyrene film

The photoperoxidation at λ > 400 nm of benzil (BZ) groups with the air oxygen to benzoyl peroxide (BP) groups in the polystyrene matrices was investigated in the presence of hindered amine stabilizer (HAS). HAS was used as a free molecule or was bound in combined molecule with BZ. HAS was in the form of parent amine as 2,2,6,6‐tetramethyl‐4‐hydroxypiperidine (TMP) and in the form of stable nitroxyl radical 1‐oxo‐2,2,6,6‐tetramethyl‐4‐hydroxypiperidine (NO). Both HAS forms effected the photooxidation of BZ structures. The main product of the photooxidation in the presence of parent amine TMP as well as in its absence is benzoyl peroxide (BP). The rate of BZ consumption increases in the presence of TMP. Irradiation of BZ in the presence of sufficient concentration of freely added NO results only in the formation of benzoic acid esters and benzoic acid, which are the main decomposition products of BP. The benzoic acid esters/benzoic acid ratio increases with the increasing concentration of NO. Bounding of BZ and TMP into one molecule (BZNH) results in slower dicarbonyl depletion, as compared with the case when mixture of BZ and TMP was used. Very slow depletion of BZ carbonyl absorption was observed in the case of bounded BZ and NO in one molecule (BZNO), in comparison with the mixture of free NO and BZ. In the case of BZNO, an effective intramolecular quenching of BZ excited triplet states with NO structures proceeds. Steady stay and dynamic emission (phosphorescence) measurements also show an effective quenching of BZ excited states by unbounded or bounded NO. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 4420–4428, 2006     

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.     

低碱性树枝状受阻胺光稳定剂的设计与合成

以丙二酸二甲酯、丙烯酸甲酯、2,2,6,6-四甲基哌啶醇、1,2,2,6,6-五甲基哌啶醇等为主要原料,经Michael加成、酯交换反应合成了低碱性树枝状受阻胺光稳定剂,目标产物总收率分别为89.3%和78.0%(以丙二酸二甲酯计)。优化的合成条件为:Michael加成反应中,n(丙二酸二甲酯):n(丙烯酸甲酯)=1:2.2,以NaOMe为催化剂,与丙二酸二甲酯的摩尔比为2.2,反应温度为20℃;酯交换反应中,n(加成产物):n(2,2,6,6-四甲基哌啶醇/1,2,2,6,6-五甲基哌啶醇)=1:4.8,以四异丙基钛酸酯为催化剂,用量为加成产物质量的2%,反应时间24h。所合成的化合物pH值分别为8.7和6.6。     

Extraction resistance and mechanism of a macromolecular hindered phenol antioxidant in natural rubber

Due to low thermal stability, poor migration, and extraction resistances, the antioxidant with low molecular weight is easy to physically lose during processing and long‐term service, and its applications are severely restricted. To increase the molecular weight of antioxidant is one of the promising methods to overcome such drawbacks. In this study, the extraction resistance of a macromolecular antioxidant, namely polyhydroxylated polybutadiene containing thioether binding 2,2′‐thiobis(4‐methyl‐6‐tert‐butylphenol) (PHPBT‐b‐TPH), was investigated by extraction resistance test and equilibrium swelling experiment. The results exhibited that the PHPBT‐b‐TPH offered much better extraction resistance in natural rubber (NR) than the low molecular weight antioxidant TPH. In addition, the extraction resistance of hydroxyl‐terminated polybutadiene (HTPB), polyethylene glycol (PEG), and polypropylene glycol (PPG) in NR were also compared to study the extraction mechanism of the PHPBT‐b‐TPH. It was found that the higher molecular weight of PHPBT‐b‐TPH and the co‐vulcanization between PHPBT‐b‐TPH and NR were the main reasons for the excellent extraction resistance. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44905.     

新型含受阻胺结构苯并三唑光稳定剂的合成及表征

以2-(2',4'-二羟基苯基)-2H-苯并三唑和5-氯-2-(2',4'-二羟基苯基)-2H-苯并三唑为原料,分别与溴乙酸乙酯进行醚化反应得到中间体2-[2'-羟基-4'-(乙氧酰基甲氧基)苯基]-2H-苯并三唑(Ⅰa)和5-氯-2-[2'-羟基-4'-(乙氧酰基甲氧基)苯基]-2H-苯并三唑(Ⅰb),Ⅰa和Ⅰb再分别与2,2,6,6-四甲基哌啶醇或1,2,2,6,6-五甲基哌啶醇进行酯交换反应得到光稳定剂2-{2'-羟基-4'-[4-(2,2,6,6-四甲基)哌啶氧酰基甲氧基]苯基}-2H-苯并三唑(Ⅱa),2-{2'-羟基-4'-[4-(1,2,2,6,6-五甲基)哌啶氧酰基甲氧基]苯基}-2H-苯并三唑(Ⅱb)、5-氯-2-{2'-羟基-4'-[4-(2,2,6,6-四甲基)哌啶氧酰基甲氧基]苯基}-2H-苯并三唑(Ⅱc),5-氯-2-{2'-羟基-4'-[4-(1,2,2,6,6-五甲基)哌啶氧酰基甲氧基]苯基}-2H-苯并三唑(Ⅱd),两步反应总收率分别为57.5%、59.1%、56.0%和54.4%。通过1HNMR、MS验证了目标化合物的结构,并测定了它们的紫外吸收光谱,4个化合物在270⁴00 nm均有较强的吸收峰,其最大紫外吸收波长(λmax)分别为338.5、338.5、347.0和346.5 nm,摩尔消光系数(εmax×104)分别为2.361 0、2.569 7、2.423 8和2.534 2 L/(mol·cm)。     

用于水性车漆的受阻胺光稳定剂的合成及性能

设计、合成了一种受阻胺光稳定剂（HALS）TM-3。首先,三聚氯氰和N-丁基-2,2,6,6-四甲基-4-哌啶胺通过亲核取代反应合成了N-丁基-4,6-二氯-N-(2,2,6,6-四甲基-4-哌啶基)-1,3,5-三嗪-2-胺（中间体Ⅰ）;中间体Ⅰ再与N,N-双(2,2,6,6-四甲基-4-哌啶基)-1,6-己二胺反应生成了N2,N2’-(己烷-1,6-二基)双[N4-丁基-6-氯-N2,N4-双(2,2,6,6-四甲基哌啶-4-基)-1,3,5-三嗪-2,4-二胺]（中间体Ⅱ）;最后,中间体Ⅱ水解生成目标化合物6,6’-{己烷-1,6-二基双[(2,2,6,6-四甲基哌啶-4-基)氮二基]}双{4-[丁基(2,2,6,6-四甲基哌啶-4-基)氨基]-1,3,5-三嗪-2-醇}（TM-3）。采用1HNMR、13CNMR、HRMS表征了TM-3的结构,通过UV-Vis、TGA考察了其性能,比较了TM-3和双(2,2,6,6-四甲基-4-哌啶基)癸二酸酯（HALS770）在汽车清漆涂料中的光稳定性。结果表明,TM-3在210nm处具有强烈的UV-Vis吸收;热稳定性能良好,在400℃以前能...     

Identification of phenolic compounds and antioxidant activity of guava dehydrated by different drying methods

Abstract

The influence of different drying techniques on guava was investigated, including phenolic components and antioxidant activities. Through drying processes, total phenolic content (TPC) increased and formation of small molecular phenolic acids (multi-methoxy benzoic acid and sinapic acid) was promoted. UPLC-ESI-QTOF-MS determination showed flavanol compounds, hydrolyzable tannins, ellagic acid conjugates and cinnamic acid derivatives were four predominant phenolics of guava. Drying treatments caused degradation of catechin and its derivatives. Contrarily, drying treatments contributed to higher contents of procyanidin trimers. Moreover, thermal drying treatments led to degradation of macromolecular tannins and formation of smaller molecular tannins and ellagic acid conjugates, while simultaneously reduced the stabilities of most intrinsic ellagic acid conjugates. Furthermore, drying processes increased the yield of cinnamic acid dihexose, probably generating from lignin or phenolics–carbohydrate complex. Freeze drying and hot air drying showed better performance on retention of TPC and enhancement of antioxidant activity (AA).     

Polyolefin elastomer grafted unsaturated hindered phenol esters: synthesis and antioxidant behavior

Monomeric antioxidants are synthesized from esterification of 3,5-di-tert-butyl-4-hydroxybenzoic acid and 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionic acid with unsaturated fatty alcohols. The antioxidant activity is evaluated both in blending and radical grafting processes. The effect of chain length and phenolic group is investigated on efficiency of antioxidants. It is demonstrated that the esters of 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionic acid exhibit significantly longer induction time. The results of radical grafting reaction shows synthesized antioxidants can be successfully grafted onto polymer chains and the phenolic moiety is functional after extraction process, while pure and commercially stabilized samples are degraded instantaneously. Also, different initiator systems are utilized to enhance the extent of grafting. Among MEK, DCP, and DHBP peroxides, DHBP can be more effective in increasing the antioxidant grafted onto polymer. In addition, possibility of rising in graft content is investigated in presence of redox initiator. Using this approach, polymer-bound antioxidant with prolonged thermal stability can be achieved.     

Melt free‐radical grafting of hindered phenol antioxidant onto polyethylene

A monomeric antioxidant (3) was prepared by reacting 3,5‐di‐tert‐butyl‐4‐hydroxybenzyl alcohol (1) with N‐[4‐(chlorocarbonyl) phenyl] maleimide (2). This reactive antioxidant was grafted onto polyethylene (PE) by melt processing with free‐radical initiators in a mini‐max molder. The IR spectra of the grafted PE showed that the monomeric antioxidant was introduced onto the PE. IR spectroscopic methods and titration were used for the quantitative determination of the extent of grafting of the monomeric antioxidant. Also, the extent of crosslinking was indicated by the gel content. Grafting occurred in the following order: dicumyl peroxide (DCP) > benzoyl peroxide > 2,2′‐azobisisobutyronitrile. The influences of the DCP concentration and monomeric antioxidant on the extent of grafting were studied. The effects of the reaction time and temperature were also determined. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 2968–2973, 2000     

Antioxidant activity of brazilian vegetables and its relation with phenolic composition

Vegetables are widely consumed in Brazil and exported to several countries. This study was performed to evaluate the phenolic content and antioxidant activity of vegetables commonly consumed in Brazil using five different methods, namely DPPH and ABTS free radical, β-carotene bleaching, reduction of Fe³⁺ (FRAP), oxidative stability in Rancimat, and the chemical composition using gas chromatography-mass spectrometry (GC-MS). The content of phenolic compounds ranged from 1.2 mg GA/g (carrot) to 16.9 mg GA/g (lettuce). Vegetables presenting the highest antioxidant activity were lettuce (77.2 μmol Trolox/g DPPH^•; 447.1 μmol F²⁺/g FRAP), turmeric (118.6 μmol Trolox/g ABTS^•+; 92.8% β-carotene), watercress and broccoli (protective factor 1.29—Rancimat method). Artichoke, spinach, broccoli, and asparagus also showed considerable antioxidant activity. The most frequent phenolic compounds identified by GC-MS were ferulic, caffeic, p-coumaric, 2-dihydroxybenzoic, 2,5-dihydroxybenzoic acids, and quercetin. We observed antioxidant activity in several vegetables and our results point out their importance in the diet.     

Betalain, Acid ascorbic, phenolic contents and antioxidant properties of purple, red, yellow and white cactus pears

Commercialization of cactus pears based on their antioxidant properties can generate competitive advantages, and these can turn into business opportunities and the development of new products and a high-value ingredient for the food industry. This work evaluated the antioxidant activities (1,1-diphenyl-2-picrylhydrazyl radical-scavenging, protection against oxidation of a β-carotene-linoleic acid emulsion, and iron (II) chelation), the content of total phenolic compounds, ascorbic acid, betacyanin, betaxanthin and the stability of betacyanin pigments in presence of Cu (II)-dependent hydroxyl radicals (OH•), in 18 cultivars of purple, red, yellow and white cactus pear from six Mexican states. Our results indicated that the antiradical activities from yellow and white cactus pear cultivars were not significantly different (p < 0.05) and were lower than the average antiradical activities in red and purple cultivars. The red cactus pear from the state of Zacatecas showed the highest antioxidant activity. The free radical scavenging activity for red cactus pears was significantly correlated (p < 0.05) to the concentration of total phenolic compounds (R² = 0.90) and ascorbic acid (R² = 0.86). All 18 cultivars of cactus pears studied showed significant chelating activity of ferrous ions. The red and purple cactus pears showed a great stability when exposed to OH•.     

Total phenolic contents and antioxidant capacities of herbal and tea infusions

In order to supply new information on the antioxidant function of selected beverages for nutritionists and the general public, total phenolic contents of 51 kinds of herbal and tea infusions made in China were measured by the Folin-Ciocalteu method, and their antioxidant capacities were evaluated using ferric reducing antioxidant power (FRAP) and Trolox equivalent antioxidant capacity (TEAC) assays. A significant correlation between FRAP and TEAC values suggested that antioxidant components in these beverages were capable of reducing oxidants and scavenging free radicals. The high correlation between antioxidant capacities and total phenolic contents indicated that phenolic compounds could be one of the main components responsible for antioxidant activities of these beverages. Generally, these beverages had high antioxidant capacities and total phenolic contents, and could be important dietary sources of antioxidant phenolics for prevention of diseases caused by oxidative stress.