Contamination in food from packaging material

Packaging has become an indispensible element in the food manufacturing process, and different types of additives, such as antioxidants, stabilizers, lubricants, anti-static and anti-blocking agents, have also been developed to improve the performance of polymeric packaging materials. Recently the packaging has been found to represent a source of contamination itself through the migration of substances from the packaging into food. Various analytical methods have been developed to analyze the migrants in the foodstuff, and migration evaluation procedures based on theoretical prediction of migration from plastic food contact material were also introduced recently. In this paper, the regulatory control, analytical methodology, factors affecting the migration and migration evaluation are reviewed.     

聚乙烯塑料包装材料中4种抗氧化剂向脂肪食品模拟物迁移的研究

本文基于超高效液相色谱建立了一种脂肪食品模拟物异辛烷中抗氧化剂叔丁基对羟基茴香醚(BHA)、2,6-二叔丁基对甲酚(BHT)、四[甲基-β-(3,5-二叔丁基-4-羟基苯基)丙酸酯]季戊四醇酯(Irganox1010)以及β-(4-羟基-3,5-二叔丁基苯基)丙酸正十八酯(Irganox1076)的提取检测方法,加标回收率在78.0%～108.7%之间,相对标准偏差(RSD)在4.0%～13.7%之间。研究了聚乙烯(PE)膜中抗氧化剂向异辛烷的迁移,讨论了温度及时间对迁移的影响,并根据迁移数据进行了初步的数学模型的建立,对实验值与数值模拟结果计算值作了对比分析。     

Influence of Natural and Accelerated Weathering on the Mechanical Properties of Low-Density Polyethylene Films

Natural and accelerated weathering tests were performed to inspect the effect of antioxidants on low-density polyethylene (LDPE) films used as greenhouse covering materials. The LDPE pellets were extruded and blown into a film using a twin-screw extruder and film blowing machine, respectively. The film with 0.2 wt.% Alkanox-240 (AN-0.2) stabilizer showed the highest tensile strength (11 MPa) among all samples during 90 days of natural as well as accelerated weathering. The elastic modulus of the film with 0.5 wt.% of Good-rite (GR-0.5) increased after weathering from approximately 91.8 to 138.9 MPa, and showed the best performance. Morphological images of the neat LDPE film during weathering showed some cracks and grooves, while those of stabilized films showed fewer cracks. Moreover, the estimation of the rapidity of the accelerated method compared to the natural one was approximately nine times faster in Riyadh during the summer season (June–August). The present study suggests that the addition of antioxidants can improve the tensile strength, stability, and, hence, the effectiveness of these films. The best antioxidants were found to be 0.2 wt.% Alkanox and 0.5 wt.% Good-rite antioxidants.     

Investigation of antioxidant and electron beam radiation effects on the thermal oxidation stability of low-density polyethylene

Effect of various antioxidants on the thermal oxidation stability of LDPE and X-LDPE has been investigated. To achieve this purpose, miscellaneous commercial grade antioxidants such as Irganox 1010, Irganox1076, Irgafos168, Irganox B225, and Chimassorb 944 were selected. Then, formulations based on different content of antioxidant were prepared. The samples were crosslinked by exposure to electron beam irradiation. To assess the thermal oxidation stability of samples, oxidation induction time (OIT) test was accomplished on both the irradiated and unirradiated specimens. Ageing tests were carried out in order to evaluate the thermal oxidation stability of irradiated X-LDPE. The results indicate that Irganox 1010 is the most effective antioxidant amongst the selected ones, concerning thermal oxidation stability of LDPE, before and after aging test.     

Determination of antioxidants by solid-phase extraction method in aqueous food simulants

An analytical method for the determination of specific migration levels of phenolic antioxidants and one phosphite antioxidant in the aqueous food simulants established by European legislation has been developed. This method involves solid-phase extraction (SPE) of the antioxidants with silica C₁₈ cartridge and their determination by liquid chromatography (LC) with diode-array detection. The achieved results in the studies of elution volume determination, breakthrough volume and accuracy are showed. Recoveries in the range of 78–104% and a relative standard deviation between 2.0 and 7.7% have been achieved.     

液-固扩散法制备可交联聚乙烯

基于小分子在聚合物中的扩散原理,采用液-固扩散法,将液态小分子交联剂、抗氧剂从固态低密度聚乙烯(LDPE)颗粒表面扩散到内部,实现小分子助剂与聚合物的均匀、温和混合,得到品质优良的可交联聚乙烯.采用DSC、FTIR等手段,分析不同扩散条件时LDPE颗粒表层和芯层的交联热焓、特征吸收峰强度的变化规律,探索小分子助剂向聚合...     

高效液相色谱法同时测定食品接触材料中抗氧化剂和紫外吸收剂的迁移量

采用高效液相色谱技术,建立了食品接触材料中多种抗氧化剂和紫外吸收剂迁移水平的检测方法。该方法测定的23种目标化合物具有较好的线性关系,相关系数（r²）≥ 0.9998,检出限和定量限分别在0.01到0.22 mg/L之间和0.03到0.85 mg/L之间。依据欧盟指令（EU）No. 10/2011,考察了5种食品模拟物30 g/L乙酸、10%（v/v）乙醇、20%（v/v）乙醇、50%（v/v）乙醇和油类模拟物（异辛烷）中抗氧化剂和紫外吸收剂的迁移量。该方法回收率在92.8%~117.7%之间,相对标准偏差在0.95%~9.72%之间。探讨了不同实验条件对抗氧化剂和紫外吸收剂回收率的影响。结果表明,该方法准确、稳定,完全满足欧盟指令（EU）No 10/2011和GB 9685-2008对食品接触材料及制品中抗氧化剂和紫外吸收剂特定迁移量（SML）的限量要求,并利用该方法测定了30批次食品接触材料中抗氧化剂和紫外吸收剂的迁移水平。     

Extraction and Quantitation of Polyolefin Additives

Abstract

The extraction and subsequent separation and quantitation of polymer additives in polyolefins has proven to be a challenge for the analytical chemist. There have been several workers over the years who have investigated the separation of additives in polyolefins (1–7), but the extraction and recovery (at > 90%) in reasonable times has been most difficult. the Soxhlet extraction technique has been used for many years, but suffers in that it takes over twelve hours to extract most of the additives used in polyolefin formulations. Some workers have used the ultrasonic bath (7), but not very much work has been done with the microwave oven. We have investigated some ways to extract the additives from polyolefins, namely, microphye oven and ultrasonic bath techniques for high density polyethylene (HDPE), low density polyethylene (LDPE), and polypropylene. We have concentrated on identifying and quantitating recoveries for typical polyolefin

antioxidants, 20 such as Irganox 1010, Irgafors 68, and Cyasorb UV 531. the extraction times are typically 20 minutes for the microwave oven and 30–60 minutes for the ultrasonic bath with 90+% recoveries being obtained. Both normal phase isocratic (used when phosphites are present) and reverse phase gradient LC techniques are discussed. We have also extracted the slip agent, erucamide, from LDPE, using reverse phase, at 200nm.     

低密度聚乙烯在振动填充注射过程中的自增强

聚烯烃自增强的研究极具应用前景，正逐渐成为人们关注的热点．其目的是利用现有通用级聚烯烃材料，通过特殊的加工方法，挖掘材料内在潜力，开发力学性能可与工程塑料相媲美的聚烯烃制品．我们的研究表明，利用振动填充注射成型技术，在低压下就能实现普通高密度聚乙烯（...     

Supercritical Fluid Extraction (SFE) Optimization by Full-Factorial Design for the Determination of Irganox 1076, Irgafos 168, and Chimassorb 81 in Virgin and Recycled Polyolefins

The performance and feasibility of supercritical fluid extraction (SFE) applied to the extraction of some antioxidants (Irganox 1076, Irgafos 168) and one UV-stabilizer (Chimassorb 81) from both virgin and recycled low density polyethylene (LDPE), and virgin high density polyethylene (HDPE) are studied. Due to the high number of variables a full-factorial design has been applied to minimize the number of experiments required to reach the optimum extraction conditions. Further analysis has been carried out off-line by reversed-phase HPLC. Modification of the physical properties of the polymeric matrix and increased number of recycling cycles as well as the influence of physical properties on the efficiency of SFE are also discussed.     

Extraction and quantification of antioxidants from low-density polyethylene by microwave energy and liquid chromatography

In this paper a experimental design is applied to optimize the quantification of hindered phenol Irganox 1076, phosphite antioxidant Irgafos 168 and their oxidized product tri[2,4-di-tert-butylphenyl]phosphate from low-density polyethylene (LDPE). The developed analytical method consists of two steps: microwave-assisted extraction and reversed-phase liquid chromatography (LC) coupled with ultraviolet diode-array detector. A Plackett-Burman design was carried out in order to find the significant experimental parameters affecting the antioxidants extraction by microwave energy. These parameters were subsequently optimized by a central composite design. The performed method allows extracting the studied antioxidants at low temperature in a short time without degradation of phosphite antioxidant Irgafos 168.     

Application of capillary electrophoresis in migration studies of food contact materials – part 1: Substituted phenolic additives

A method has been developed to determine 11 phenolic antioxidants in the food simulants distilled water, 3% acetie acid, and 15% ethanol, using; micellar capillary electrophoresis (MCE). All the phenols could he analyzed within 35 min. The analytical recovery from spiked simulants was 80 to 119% except for 2,6-di-tert-butyl-4hydroxytoluenc (BHT) and octyl gallate, which could not be recovered from 3% acetic acid simulant. Calibration graph correlation coefficients for the 11 phenols were 0.982 to 0.999. Limits of detection (LoDs) were from 2.8 to 8.6 mg/L. These LoDs are well below European Union migration limits for these substances. It is concluded therefore that MCE offers a rapid and reliable analysis for the control of migration from plastics intended for food contact which employ these phenols as antioxidants.     

交联方法对交联聚乙烯结晶行为的影响

研究了硅烷交联聚乙烯和过氧化物交联聚乙烯由于结晶和交联的顺序不同而造成的结晶行为的差异，交联密度相同时，过氧化物交联聚乙烯的结晶度和熔点明显低于硅烷交联聚乙烯，交联聚烯非等温结晶动力学表明：交联前后聚乙烯的Ａｖｒａｍｉ指数ｎ基本不变，交联后，半结晶期ｔ１／２延长、结晶速率常数ＺＣ下降，其中过氧化物交联聚乙烯的变化幅度大于硅烷交联聚乙烯。     

The effect of gamma irradiation on mechanical, and thermal properties of recycling polyethylene terephthalate and low density polyethylene (R-PET/LDPE) blend compatibilized by ethylene vinyl acetate (EVA)

A study has been made on the compatibility of recycled polyethylene terephthalate (R-PET) and low density polyethylene (LDPE) blend in the presence of ethylene vinyl acetate (EVA) as a compatibilizing agent prepared by extrusion hot stretching process. EVA content in the blend as a compatibilizing agent was an enhancement effect on radiation crosslinking of R-PET/EVA/LDPE blends and the highest radiation crosslinking was obtained when the EVA content was reached at 10 % EVA when irradiated by gamma irradiation. Blends containing different (EVA) ratios were irradiated to different doses of gamma irradiation 25, 50 and 100 kGy. The effect of the compatibilizer and radiation on mechanical, thermal properties of R-PET together with LDPE and morphology has been investigated. It was found that gamma irradiation together with the presence of compatibilizing agent (EVA) has positive effect on the mechanical and thermal properties of R-PET/LDPE blend. The structural properties of R-PET/LDPE modified by gamma irradiation and EVA as compatibilizing agent was examined by SEM. Also, it was found that the optimum concentration of EVA and gamma irradiation dose was found to be 10 % EVA and 100 kGy, respectively.     

Caractérisation des branchements courts dans un polyéthylène basse densité par RMN 13C

Carbon-13 NMR analysis of chain branching in low density polyéthylène (LDPE) at 62,89 MHz has revealed the existence of three kinds of complex chain branching besides more than four kinds of well known isolated branches. Well resolved carbon-13 spectra consisting of 26 peaks have been observed for one LDPE sample. For reasonable assignments of all the carbon atoms which play roles in branching signals, model compounds have been used, and three kinds of additivity rules for carbon-13 chemical shifts have been applied. Taking into account the double back-biting scheme in the formation of LDPE, 2-ethyl hexyl, 1,3-diethyl pair and tetrafunctionnal branches have been found besides isolated branches such as ethyl, butyl, pentyl, hexyl and longer chains.     

Temperature variations of NMR second moments for drawn tapes based on polypropylene and polyethylene

Isotropic and drawn tapes prepared from isotactic polypropylene (PP), low density polyethylene (LDPE) and their blend PP/LDPE (70/30) have been studied by broad‐line nuclear magnetic resonance (NMR) in the temperature range from 120 up to 320 K. The glass‐transition temperatures, T_g, for studied samples have been determined from the temperature dependencies of the NMR second moments. It was found that the NMR spectra and their second moments are additive for isotropic blend in the whole temperature range, while a significant differences from addition rule appear for drawn PP/LDPE blend, when weighted average second moment is calculated by means of second moments of equally drawn homopolymers. It was found out that the LDPE component in the blend is drawn to a greater extent than PP component.     

光降解性聚乙烯薄膜降解过程的表征

用全反射傅里叶红外光谱、Ｘ射线光电子能谱和示差扫描量热仪研究了含光敏剂的低密度聚乙烯薄膜在光降解过程中降解速率的变化规律，结果表明，光降解性聚乙烯薄膜在降解过程初期，降解速率很小，光敏剂显示抗氧化剂性能；降解２４ｈ后，降解速率迅速增加，直至薄膜破坏，光敏剂显示光引发剂性能。作为对比，同时研究了光敏剂和其它两种添加剂对聚乙薄膜光解速率的协同效应和两种添加剂体系显示的性能。     

结晶聚合物的辐射效应：多官能团单体对LDPE的结晶成核作用

根据x射线、电镜、DSC和凝胶分数的测试结果,讨论了多官能团单体结构对低密度聚乙烯聚集态结构的影响以及结晶度与辐射交联(或剂量)的关系。发现由于单体的存在导致低密度聚乙烯结晶度增加而结晶尺寸变小(即结晶成核效应);成核效应越大,增强辐射交联的效果也越大。添加具有高结晶成核作用的单体有利于低密度聚乙烯的辐射交联,同时也加速其结晶结构的破坏。     

结晶聚合物的辐射效应——多官能团单体对LDPE的结晶成核作用

根据x射线、电镜、DSC和凝胶分数的测试结果,讨论了多官能团单体结构对低密度聚乙烯聚集态结构的影响以及结晶度与辐射交联(或剂量)的关系。发现由于单体的存在导致低密度聚乙烯结晶度增加而结晶尺寸变小(即结晶成核效应);成核效应越大,增强辐射交联的效果也越大。添加具有高结晶成核作用的单体有利于低密度聚乙烯的辐射交联,同时也加速其结晶结构的破坏。     

Early detection of degradation in a semi-crystalline polyolefin by a successive self-nucleation and annealing technique

Samples taken from a black pipeline liner that became fragile while in service were analyzed by a Successive Self-Nucleation and Annealing (SSA) technique. Two types of polyethylene, Low-Density Polyethylene (LDPE) and Linear Low-Density Polyethylene (LLDPE) were aged in air, at several temperatures, and changes in the molecular structure were followed simultaneously by infrared and calorimetric techniques. Samples with and without antioxidants were prepared, aged, and evaluated for the same oxidative treatments. The LDPE type was chosen to be identical to the black LDPE originally used for making the pipeline liner. Oxidative reactions of LDPE and LLDPE were quantified via carbonyl group concentrations measured by FTIR. Changes in the crystallization behavior of the original and aged polymers, and of the black pipeline liner, were monitored via the SSA technique. Changes of the fraction of lamellae of specific thickness in the crystallized polymer could be correlated linearly with the formation of carbonyls, and thus this calorimetric method is proposed to be suitable as a tool for early quantitative monitoring of LDPE degradation.