Comparison of the degradability of poly(lactide) packages in composting and ambient exposure conditions

The adoption of biodegradable polymeric materials is increasing in food and consumer goods packaging applications, due to concerns about the disposal of petroleum‐based polymers and the increasing cost of petroleum‐based polymer resins. Currently, poly(lactide) (PLA) polymers are the biggest commercially available bio‐based polymeric packaging materials. As the main motivation for adopting biopolymers is environmental, there is a need to address the degradability and environmental performance of biodegradable packages. The aim of this study was to investigate and compare the degradation of two commercially available biodegradable packages made of PLA under real compost conditions and under ambient exposure, using visual inspection, gel permeation chromatography, differential scanning calorimetry and thermal gravimetric analysis. A novel technique to study and track the degradability of these packages under real compost conditions was used. Both packages were subjected to composting and ambient exposure conditions for 30 days, and the degradation of the physical properties was measured at 1, 2, 4, 6, 9, 15 and 30 days. PLA bottles made of 96% l ‐lactide exhibited lower degradation than PLA delicatessen (‘deli’) containers made of 94% l ‐lactide, mainly due to their highly ordered structure and, therefore, their higher crystallinity. The degradation rate changed as the initial crystallinity and the l ‐lactide content of the packages varied. Temperature, relative humidity and pH of the compost pile played an important role in the rate of degradation of the packages. First‐order degradation kinetics and linear degradation trends were observed for both packages subjected to composting conditions. Copyright © 2006 John Wiley & Sons, Ltd.     

Thermal and catalytic degradation of polyethylene wastes in the presence of silica gel, 5A molecular sieve and activated carbon

A comparative study of thermal and catalytic degradation of polyethylene wastes has been carried out with the aim of obtaining chemical compounds with potential use in the chemical industry and the energy production. Polyethylene wastes were obtained from polyethylene bags used in supermarkets. Catalysts utilized in the study were silica gel, 5A molecular sieve and activated carbon. The pyrolysis was performed in a batch reactor at 450, 500 and 700 °C during 2h for each catalyst. The ratio catalyst/PE was 10% w/w and the solid and gaseous products were analyzed by gas chromatography and mass spectrometry. The optimum operation temperature and the influence of the three catalysts are discussed with regards to the products formed. The best temperature for degradation with silica gel and activated carbon as catalysts was 450 °C and with 5A molecular sieve was 700 °C. Degradation products of PE (solid fraction and gas fraction) are depending on temperature and catalyst used. External surface and structure of catalysts were visualized by Scanning Electron Microscopy (SEM) and the contribution on product distribution is commented. All products from different degradations could be used as feed stocks in chemical industry or in energy production based on the value of heat of combustion for solid fraction (45000 J/g), similar to the heat of combustion of commercial fuels.     

用活性薄膜贮存活鱼

研究了无机物充填的ＰＥ薄膜－－活性薄膜（ＡＦ）贮存活鲤鱼，在封闭的状态下，与普通聚乙烯薄膜袋相比，能明显地提高鲁鱼的平均寿命，共袋中水的溶解氧２浓度及ＰＨ值均高于ＰＥ薄膜袋，说明该活性薄膜具有调节水中氧气及二氧化碳浓度的功能。     

Application of active film packaging to transport live fish

Cylindrical bags made of inorganic-filled PE film (active film) (AF) containing fresh water were applied to storage of living carp. The tops of the bags were usually kept closed, with the exception of the moment for determining the content of dissolved oxygen (DO). For comparison, a cylindrical glass jar and other cylindrical bags made of plain PE film were used for the same test. The results show that the mean life of carp in the AF bag was more than 64h, whereas those in the glass jar and the plain PE film bags were 25 and 26h, respectively. The content of DO in the different types of container with living carp was measured. It indicated that the content of DO in the AF bags was more than that in the others. Thus, it is significant that it can be used to store and transport aquatic plant and animal or other organisms in a closed container.     

氨基酸酯取代聚膦腈的分子结构和性能关系的研究——(Ⅱ)性能及其降解行为

已经报道了五种氨基酸乙酯取代聚膦腈的合成及反应条件和加料顺序对聚合物结构的影响。本文进一步对这五种聚合物的亲水性、力学性能、成膜性能以及降解行为进行了研究,发现该类聚合物具有较好的降解性能,通过比较降解前后聚合物结构的变化,探讨了氨基酸酯取代聚膦腈的水解机理,证实该类聚合物的降解是以侧基中酯键水解开始的。     

Neutral loss fragmentation pattern based screening for arginine-rich natural products in xenorhabdus and photorhabdus

Although sharing a certain degree of structural uniformity, natural product classes exhibit variable functionalities such as different amino acid or acyl residues. During collision induced dissociation, some natural products exhibit a conserved fragmentation pattern close to the precursor ion. The observed fragments result from a shared set of neutral losses, creating a unique fragmentation pattern, which can be used as a fingerprint for members of these natural product classes. The culture supernatants of 69 strains of the entomopathogenic bacteria Photorhabdus and Xenorhabdus were analyzed by MALDI-MS(2), and a database comprising MS(2) data from each strain was established. This database was scanned for concordant fragmentation patterns of different compounds using a customized software, focusing on relative mass differences of the fragment ions to their precursor ion. A novel group of related natural products comprising 25 different arginine-rich peptides from 16 different strains was identified due to its characteristic neutral loss fragmentation pattern, and the structures of eight compounds were elucidated. Two biosynthesis gene clusters encoding nonribosomal peptide synthetases were identified, emphasizing the possibility to identify a group of structurally and biosynthetically related natural products based on their neutral loss fragmentation pattern.     

Estimation of the biodegradability of packaging materials by a screening test and a weight-loss method

Two methods were studied in order to estimate the degradability of packaging materials, using cellulosic materials—such as cellophane or paraffin waxed paper—as models. A preliminary orientation test was carried out, based on the visual observation of microbial development on the materials used. This qualitative test permitted an initial classification of materials according to their potential degradability, and especially allowed the identification of microbial species, particularly fungi, most likely to grow on the materials being studied. The biofragmentation of materials was evaluated from their dry weight loss. For a fixed time of incubation, the classification of these materials was based either on the percentage or on the absolute value of this weight loss. For the method applied to a solid medium, we found that an inoculum deposited on an agar surface was more suitable than direct inoculation of the samples, in fact, pure fungi strains, especially Trichoderma viride or Aspergillus niger, were found to be more suitable for cellulosic materials than the bacterial strains (Pseudomonas fluorescens) or bacterial mixture used.     

纸浆模塑包装制品分体式吸滤成形模具的开孔问题

目的研究纸浆模塑制品分体式成形模具的开孔问题,以保证制品厚度均匀、外观美观。方法通过分析纸模制品成形过程中滤液流动的能量损失,建立滤液在分体式模具内的出流过程的能量方程,以研究模具特定部位间应具有的开孔率关系。结果建立了模具不同部位之间的开孔率关系式,并研究了模具各部位的布孔方法。结论为保证纸模制品壁厚一致,模具不同部位间的开孔率需满足一定关系;模腔底面宜采用60°错排的布孔方式,而直立侧壁可划分成若干连续的单位开孔区,采用非均匀性布孔方式。     

Elemental and spectroscopic characterization of humic-acid-like compounds during composting of olive mill by-products

Humic acids (HAs) were isolated at different stages of composting from two piles of solid olive mill residues (SOR) treated for the first 30 days with tap water (pile C1) or olive mill wastewater (pile C2), for a total composting period of 9 months. The HA fractions were characterized by elemental analysis, UV-visible, Fourier transform infrared and fluorescence spectroscopy in order to monitor humification process and the maturity of the composts. As composting proceeded, the elemental composition of the humic acids showed a decrease in C and H content, and in the C/N ratio, and an increase in N and O contents and in the C/H and O/C ratios. These changes could be attributed to a loss of aliphatic groups and to an increase of aromatic character, polycondensation and degree of oxidation of the HAs. Spectroscopic data agree and support these results, suggesting that the chemical and structural features of the HAs of both composts tend to reach those typical of native soil HAs, that is compounds with a high degree of humification and a high molecular weight and complexity. Therefore, both composting processes seem suitable to produce well-humified organic matter, with important benefits for their use in soil amendment. No differences appeared between the two treatments concerning the humic character of the two final composts.     

Degradation kinetics of di-(2-ethylhexyl) phthalate (DEHP) and organic matter of sewage sludge during composting

The potential degradation of di-(2-ethylhexyl) phthalate (DEHP) and organic matter of sewage sludge by composting was investigated using laboratory reactor at different operating conditions (E-1, E-2 and E-3). In all conditions, single stage thermophilic phase was observed within 2 days and almost, 60% of DEHP was degraded under this phase. At the end of composting, total DEHP degradation of more than 85% was observed in all conditions and total carbon reduction was 11.8% in E-1, 7.6% in E-2 and 10.8% in E-3. Similar trend was observed in the degradation of total nitrogen. The reduction of volatile solids (VS) in the composting reactors was 5.4% in E-1 (18 days), 5.5% in E-2 (12 days) and 4.3% in E-3 (18 days). The degradation kinetics of DEHP in thermophilic phase (including initial mesophilic phase) and the phase there after were determined by first order and fractional power kinetics, respectively. The significance of experimental parameters in DEHP degradation was assessed by Pearson correlation approach. Elevated temperature produced during composting was effective for the rapid degradation of DEHP from sewage sludge compared to mesophilic treatment.     

Monitoring a Flow of “Hot” Tritium Atoms in the Course of Thermal Activation

The possibility of measuring a flow of reactive tritium atoms falling on a target during thermal activation using polyethylene (PE) films was studied. Procedures were developed for pretreatment of PE films before experiment, their subsequent treatment, and radioactivity measurements. The distribution of the flow of tritium atoms in a common reactor as influenced by various modes of atomizer arrangement and different experimental conditions was studied with PE films. The rate of formation of the labeled compound was maximal when the product of the tritium pressure in the system (Pa) by the distance from the atomizer to the target (cm) was 2.     

不饱和硅烷熔融挤出接枝聚乙烯的研究

采用熔融挤出法对低密度聚乙烯进行硅烷接枝,然后在催化剂二月桂酸二丁基锡存在进行水解交联,对接枝产物的熔体流动速率和交联样品的凝胶率的影响因素进行了系统的研究,接枝单体为乙烯基三乙氧基硅烷,主要引发剂为过氧化二异丙苯。     

抑菌功能性可降解保鲜包装对香蕉的保鲜研究

目的 比较生物全降解保鲜袋和普通市售保鲜袋对香蕉保鲜效果的差异,证明生物全降解袋的优越性,以期为果蔬保鲜包装材料的研发及果蔬保鲜提供参考。方法 研发生物全降解保鲜袋,并以香蕉为原料,通过运用生物全降解袋和普通市售保鲜袋作为对照进行低温保鲜实验,每隔3 d进行观察,并记录实验过程中香蕉表观、质量损失率、色度、硬度、糖度和感官等指标的变化。结果 相较于市售保鲜袋,生物降解袋能有效抑制香蕉表面斑点的出现和发展,保持较好的外观,并且能延缓香蕉果肉硬度的下降,维持果肉质地,贮藏期间感官评分也整体更高;但生物降解袋质量损失率高,且贮藏前期香蕉糖度下降较快。结论 生物降解袋能更好维持15 ℃贮藏条件下香蕉的品质,具有更优的抑菌功能性。     

CaO-P2O5-SiO2系统溶胶-凝胶玻璃的生物矿化行为

利用体外实验方法(in vitro)以及XBD、SEM、FTIR、BET、ICP等手段研究了两种溶胶一凝胶生物活性玻璃的显微结构及其在模拟生理溶液(SBF)中的降解过程、表面反应产物和生物矿化机理．结果表明，两种生物活性玻璃都具有较高的生物活性，均具有由纳米尺寸颗粒相互连接而成的微孔结构和较大的比表面积，在模拟生理溶液(SBF)中浸泡后可形成表面类似天然骨中无机矿物的碳酸经基磷灰石层(HCA)，说明两者均具有较高的生物活性和生理环境相应特性．材料表面的硅酸凝胶层及其硅经基团的形成对碳酸经基磷灰石(HCA)微晶的成核有重要作用。     

Improving the performance of retail stores subject to execution errors: coordination versus RFID technology

This paper analyzes a Newsvendor type inventory model in which a manufacturer sells a single product to a retailer store whose inventory is subject to errors stemming from execution problems. Hence, within the store, all of the products are not available on shelf for sales either because the replenishment of the shelf from the backroom is subject to execution errors that mainly result in products lost in the backroom or products misplaced on the other shelves of the store. We compare two situations: in the first situation, the two supply chain actors are aware of errors and optimize their ordering decisions by taking into account this issue. The second situation deals with the case where an advanced automatic identification system such as the Radio Frequency Identification technology is deployed in order to eliminate errors. Each situation is developed for three scenarios: in the centralized scenario, we consider a single decision-maker who is concerned with maximizing the entire supply chain’s profit; in the decentralized uncoordinated scenario, the retailer and the manufacturer act as different parties and do not cooperate. The third scenario is the decentralized coordinated scenario where we give conditions for coordinating the channel by designing a buyback contract. The authors would like to thank the editor, Prof. Dr. Hans-Otto Guenther, and two anonymous referees for their constructive comments to improve this article.     

Oxygen‐ and light‐barrier properties of thermoformed packaging materials used for modified atmosphere packaging. evaluation of performance under realistic storage conditions

The oxygen transmission rate (OTR) of packaging materials used for modified atmosphere packaging (MAP) of chilled products varies extensively with temperature, relative humidity (RH) and material thickness after the thermoforming of packages. Two different polymer combinations were studied: APET/PE (tray) and PA/PE (lid). A temperature reduction of 8°C (in the interval 7–23°C) caused an OTR reduction of 26–48% depending on material type, degree of thermoforming and RH. A 2–3‐fold increase in OTR was observed for PA/PE film when measured at 100/100% RH compared to 0/100% RH, whereas the APET/PE trays were not affected by RH. Increased OTR was observed as a result of material thinning; however, the increase was not always directly proportional to the degree of material thinning. Even very small amounts of oxygen have, in combination with light exposure, significant effects on oxidative quality deterioration of many products. Consequently, the changes in OTR observed in this study emphasize the necessity of evaluating the performance of packaging materials under realistic storage conditions, in order to estimate the real oxygen content of a chosen package solution. The light transmission through the packaging material was found to be reduced to 0–30% (300–800 nm) by dyeing of the lid and/or addition of labels. Thus, it is easy to protect the products from light, at least partly. Copyright © 2005 John Wiley & Sons, Ltd.     

An evaluation of stability by thermogravimetric analysis of digestate obtained from different biowastes

Research was carried out with the aim of monitoring anaerobic digestion processes using thermal analysis with the aid of mass spectrometry so as to define the stability of the digestate obtained. Three different systems were investigated under varying conditions. The digestion of waste sludge from a pharmaceutical industry (PI) and the digestion of cattle manure (CM) were evaluated under mesophilic conditions. The co-digestion of a mixture of primary sludge (PS) and the organic fraction of municipal solid wastes (OFMSW) was studied under thermophilic conditions. Temperature-programmed combustion tests were carried out to investigate the degree of stabilization of samples throughout the digestion processes. The derivative thermogravimetry (DTG) profiles obtained for the mesophilic digestion of PI waste showed a decrease at low temperatures and an increase at high temperatures in the intensity of the peaks recorded as the stabilization process proceeded. These results are in accordance with those obtained by the present authors in their previous work on the mesophilic digestion of primary sludge and OFMSW. In contrast, the DTG profiles obtained from the stabilization process of CM and thermophilic codigestion of PS and OFMSW showed a reduction in peaks at high temperatures. When the stabilization products obtained from CM by anaerobic digestion and by composting processes were compared, it was observed that the composting process was capable of further decomposing materials readily oxidized at low temperatures and increasing the presence of structurally more complex substances. The evolution of the differential thermal analysis (DTA) signal recorded simultaneously showed considerable similarity to the mass/charge (m/z) signal 44 registered by the mass spectrometer. The use of mass spectrometry helped to clarify the inner workings of the digestion process.     

Domestic product failures – Case studies

Every year in the UK more than 4000 people die in accidents in and around the home and nearly three million turn up at accident and emergency departments seeking treatment. Intrinsic in this number are many incidents of injury or death directly attributable to poor product design or manufacture of domestic products. In and around the home, commodities that dominate so much of every-day life are becoming more numerous and complex and could be mooted as an argument for such dire statistics. Moreover, society in general is becoming more litigious. These converging trends are responsible for an increasing significance of product liability. When property is damaged, personal injury sustained or loss of life occurs there is an understandable need to determine where any fault may lie. The forensic (or failure) engineer will glean relevant information through meticulous investigation and a reverse engineering process. Reconstructing the failure will uncover any inherent defect in product design, manufacturing, incorrect installation or maintenance. However, product failure can also be attributable to careless use or abuse by the individual, rather than to any specific defect or design shortcoming being inherent within a product. Ultimately the outcome of any investigation will be a sound finding and a conclusion that clearly describes what happened and why. To illustrate typical failure modes that are currently emerging in the home-based UK market, a range of domestic product failures are presented from the author’s forensic casebook.     

包装材料对肉类食品胀袋问题的影响与分析

目的 比较分析不同种类包装材料的性能差异对所包装肉类食品胀袋问题的影响。方法 以常见的用于包装烧鸡的PA/Al/CPP、BOPA/LDPE,包装猪蹄的PET/PA/CPP、PET/PA/Al/CPP,包装肉肠的PVDC共挤膜、BOPP/PVDC/PE等6种材料为试验样品,分别测试其揉搓前后氧气透过量、拉伸性能、抗穿刺性能、热封强度、密封性能。结果 样品阻隔性由高到低依次为PET/PA/Al/CPP、PA/Al/CPP、PVDC共挤膜、BOPP/PVDC/PE、PET/PA/CPP、BOPA/LDPE;揉搓后PET/PA/Al/CPP阻隔性仍较高,PA/Al/CPP耐揉搓性差,出现贯穿性针孔,揉搓前后BOPA/LDPE、PET/PA/CPP的阻隔性相差不大;BOPP/PVDC/PE拉伸性能较差,横向断裂伸长率仅为28.4%,且热封强度低,其余样品的拉伸性能、抗穿刺性能、热封强度均较好;PA/Al/CPP,BOPP/PVDC/PE成品包装分别在袋体折皱处、袋体与热封口处漏气,其余样品均未漏气。结论 耐揉搓性差、拉伸性能差及热封强度低分别是烧鸡PA/Al/CPP包装、肉肠BOPP/PVDC/PE包装发生胀袋的主要原因;阻氧性偏低易导致由BOPA/LDPE,PET/PA/CPP,PVDC 5层共挤膜包装的烧鸡、猪蹄、肉肠在长时间存储时缓慢胀袋。上述样品存在的问题主要与材质结构、铝箔层质量、材料生产及热封工艺有关。     

缓冲包装设计引起的易损件移动现象的力学原理

目的研究产品在物流运输搬运过程中易损件会发生转移的行为。方法提出轻型小机电产品包装冲击动力学模型,建立基于2个易损件的产品冲击动力学方程,得到易损件的峰值加速度与刚度比的关系图,并且采用Runge-Kutta法进行数值求解,获取2个易损件在半正弦激励脉冲激励下的冲击时域响应、冲击谱和破损边界曲线。结果产品在不同的刚度比下,各个部件出现损坏的先后顺序不同,谁先坏本质上取决于哪个部件的峰值加速度响应首先达到其脆值。结论研究揭示了易损件随着冲击激励和包装材料特性发生移动的现象和本质原因。