我国食品接触塑料包装制品再生利用的法律规制：以PET饮料瓶为例

回收塑料用于食品包装制品是未来的发展趋势,我国目前对此尚无明确的法律规定。推动我国食品接触塑料包装制品再生利用的法律规制,以食品安全为中心,兼顾环境保护、循环经济与绿色消费,在保障食品接触材料对食品安全性的基础上,既能促进食品包装再生利用产业发展,又能推动废弃塑料治理与环境保护,实现食品安全前提下的资源循环利用与消费升级。本文从我国法律规制的发展概况出发,在论述法律规制的必要性与可行性、对域外经验借鉴的基础上,提出确认回收塑料的法律地位、制定再生聚对苯二甲酸乙二醇酯材料的食品安全国家标准、完善食品接触再生塑料包装的市场准入、构建再生利用社会共治格局的完善路径。     

四种聚合物包装材料对亚麻籽油氧化产物的影响研究

为了探究聚合物包装材料对食用油氧化的影响,以亚麻籽油和不同聚合物包装材料(聚酰胺(PA),聚乙烯(PE),聚对苯二甲酸乙二醇酯(PET)和聚丙烯(PP))为研究对象,探讨在室温和60℃条件下四种聚合物包装材料表面和颗粒对亚麻籽油初级氧化产物及挥发性产物的影响。利用接触角测量仪、傅里叶变换红外光谱仪及气相色谱-质谱联用仪对材料表面特性、亚麻籽油初级氧化产物及挥发性产物进行了测定。结果表明:包装材料亲水性顺序为PET PP PE PA;在不同温度的氧化条件下,材料表面和颗粒对亚麻籽油产生氢过氧化物速率顺序均为PP PA PE≈PET和PA PP≈PE PET;不同聚合物表面对亚麻籽油在室温及60℃条件下产生挥发性物质总量影响顺序分别为PP PET≈PE PA和PP PA PET PE。聚合物的亲水性对亚麻籽油氧化变化有较大影响,且不同温度下对氧化产物的影响具有一定差异性。     

回转式给袋包装机自动供袋机构设计

供袋机构是回转式给袋包装机的重要组成,其性能直接影响包装机的包装速度与包装精度。基于包装机及供袋部件工作原理的分析,设计了供袋部件的自动供袋工艺流程,确定了供袋部件的机构构型和工作循环图;以二次上袋机构为例,建立了上袋机构的机构分析模型,采用封闭矢量法,求取了机构输出与凸轮输入转角的数学模型。基于供袋部件的机构分析与设计流程,综合考虑机器总体布局、机构尺寸与结构设计等因素,优化确定供袋机构的连杆尺寸,实现预制包装袋的高效平稳供送。     

Core–Shell Polymer Adhesive for Aluminized Coatings: From Improved Barrier Properties to Commercial Formulation

The development and formulation of core–shell latex‐based adhesives to improve the adhesion of aluminium to poly(ethylene terephthalate) (PET) films and enhance the permeability of the final laminate to oxygen and water is described. All particles have a soft acrylic component (the shell in core–shell particles) to improve adhesion, and occasionally a hydrophobic core to enhance the permeability. The performance of the different latexes is compared to that of a commercially available reference material. The coatings formed by core–shell nanoparticles present a lower permeability to water than the particles synthesized in the absence of the seed, while the permeability to oxygen is found to be mainly related to the correct deposition of the metallic layer. In terms of the industrial formulation, it is found that a limited amount of a wetting agent (WA) is needed to ensure the correct spreading of the latex onto the PET substrate because of the low levels of surfactant used for the latex production. This compound has a positive effect on the adhesive strength of the coating. A curing agent also improves barrier properties, but the optimal level of this compound is dependent on the degree of crosslinker used in the base latex.     

Predicting trends in structural and physical properties of a model polymer with embedded natural fibers: Viability of molecular dynamics studies for a bottom up design

The effects of relatively high- and low-shear processing on the macroscopic and microscopic porosities of a standard packaging polymer—linear low density polyethylene (LLDPE) and its composites with pine flour are studied. The macroscopic porosities, represented by deviations of observed density from the theoretical density, primarily drive the trends in mechanical and solvent uptake properties. The microscopic porosities of the system, however, are independent of the processing method and pine flour concentration. Furthermore, by using molecular dynamics (MD), molecules of LLDPE and pine flour were constructed. The material properties of the molecules, specifically microporosity and elastic moduli, were compared to experiment. A semiempirical modeling approach was used to fit the simulated data to the experimental composite moduli. The model of Halpin and Tsai was found to be the most efficacious for this system, and the benefits of the combined MD-semiempirical modeling for bottom up design are discussed. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 48189.     

Surface texture and barrier performance of poly(lactic acid)–cellulose nanocrystal extruded-cast films

In this study, we assessed the influence of cellulose nanocrystal (CNC) addition level (0.5–2 wt %) on the surface texture, thickness, and barrier properties of poly(lactic acid) (PLA) extruded-cast films. Regardless of the CNC content, the addition of CNC increased the surface average roughness and maximum roughness of the PLA films in both the machine and cross-machine directions because of the presence of CNC agglomerates. The increased roughness resulted in films with uneven thicknesses; this affected their accurate measurements with a conventional micrometer. Rather, accurate thickness measurements were obtained through the density method, a more appropriate thickness measurement method for films with rough surfaces. The permeability values were negatively correlated with the increased crystallinity. Both the water vapor permeability and oxygen permeability (OP) values decreased significantly by approximately 26–45 and 25–50%, respectively, as the CNC content increased from 0.5 to 2 wt % because of the tortuosity effect. The OP values of the neat PLA and composite films remained insensitive to changes in the relative humidity (from 0 to 75%) when they were tested at 23 °C. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47594.     

Evaluation of methoprene-treated packaging against Trogoderma granarium Everts and Trogoderma inclusum LeConte larval development and packaging penetration or invasion

Trogoderma granarium Everts, khapra beetle, and Trogoderma inclusum LeConte, larger cabinet beetle, are highly destructive insect species that can infest a variety of food sources. Methoprene is an insect growth regulator, IGR, and recently has been incorporated into packaging materials as a treatment option for packaged grain, food, birdseed, and feed products, and labeled for this use by the US Environmental Protection Agency. The objective of this research was to investigate the effect of continual exposure to this novel packaging technology on the development of T. inclusum and T. granarium larvae, and its potential use as a packaging treatment to prevent the penetration or invasion of T. inclusum and T. granarium into food packages. The methoprene-treated packaging incorporated into Kraft paper, woven bag material, polyethylene-polyethylene (PE-PE) material, and a polyethylene terephthalate-polyethylene (PET-PE) material, reduced normal adult emergence of exposed larvae. No normal adult emergence was observed on the inside surface of the PET-PE material. The polymer-based materials were the most effective at preventing penetration or invasion by Trogoderma spp. Only 2% of packages were invaded among all packaging treatment combinations compared to 16.7% invasion of untreated packages. The materials were ranked in effectiveness as Kraft < woven < PET-PE < PE-PE, however, all materials demonstrated significant positive results on Trogoderma spp. This novel packaging could easily be adopted as a packaging control strategy against these and other stored product insects in packaged products destined for commercial, international, and smallholder farm storage of cereal grains, feed, and other food products.     

Chemical changes in almonds throughout storage: modeling the effects of common industry practices

Further investigations of almond degradation under typical industrial storage conditions from a quantitative perspective are warranted. This study modeled effects of packaging, temperature (TEMP), relative humidity (RH) and roasting on chemical attributes of almonds stored according to common industry practices throughout 16 months. Roasted samples were stored in high-barrier bags (HBB) or polypropylene bags (PPB) at multiple combinations of TEMP and RH. Raw samples were held in unlined cardboard cartons (UC) or PPB under the same conditions. Almonds were assessed bimonthly for oxidation products, free fatty acids, moisture content and water activity. Results indicated roasting almonds improved quality preservation. Models showed HBB (rather than PPB) to provide benefits to stability comparable to reductions in storage TEMP of ~15 to 30 °C. PPB (rather than UC) showed benefits to peroxide formation of similar magnitude. Our data shows HBB to be a superior packaging choice, and UC to associate with the greatest rates of degradation.     

Potential of a nisin-containing bacterial cellulose film to inhibit Listeria monocytogenes on processed meats

A bacterially produced cellulose film containing nisin was developed and used in a proof-of-concept study to control Listeria monocytogenes and total aerobic bacteria on the surface of vacuum-packaged frankfurters. Bacterial cellulose pellicles were produced by Gluconacetobacter xylinus K3 in Corn Steep Liquor-Mannitol Medium and were subsequently purified before nisin was incorporated into them. Investigations into the effect of nisin concentrations and contact times on incorporation of nisin into cellulose films showed that the lowest nisin concentration and shortest time needed for production of an effective antimicrobial cellulose film were 625IUml(-1) and 6h, respectively. The active cellulose films produced under these conditions did not, however, significantly reduce L. monocytogenes populations on frankfurters (P>0.05) during refrigerated storage for 14 days as compared to the controls. Films produced using a higher concentration of nisin (2500IUml(-1)) with the same exposure time (6h) resulted in a significant (P<0.05) decrease in L. monocytogenes counts on frankfurters of approximately 2logCFUg(-1) after 14 days of storage as compared to the control. Both the above-mentioned films showed a similar effectiveness in reducing total aerobic bacterial populations as measured by total aerobic plate counts on frankfurters. For both films, total aerobic bacterial levels were significantly (P>0.05) reduced by approximately 3.3logCFUg(-1) after 14 days of storage as compared to control samples. Bacterial cellulose films were demonstrated in this study to have potential applicability as antimicrobial packaging films or inserts for processed meat products.     

步进电机细分技术在DXD系列包装机中的应用

DXD系列包装机在工作中容易产生袋长误差,无法随机补偿、调整。文章介绍一种基于AT89C51单片机控制的恒频斩波细分驱动方案及实现技术。试验表明,该方案细分精度高,运行平稳,可提高包装机的走纸精度和平稳性。