Biobased mineral‐oil barrier‐coated food‐packaging films

Toxic mineral oils can migrate into foods from cardboard boxes made of recycled fibers. This is an emerging issue for the whole dry‐food‐packaging industry. Breakfast cereals, for example, are typically packaged in boxes with or without inner bags and consumed without further processing. Currently, fossil‐based high‐density polyethylene (HDPE) films are used as a major raw material for such inner bags. However, HDPE is a very poor barrier against mineral‐oil migration. Biobased coatings from cellulose nanofibrils (CNFs), hydroxypropylated xylan, and hydroxypropylated cellulose were applied onto biobased high‐density polyethylene (bio‐HDPE) films, and the mineral‐oil barrier properties were evaluated. All of the coated films significantly decreased the migration of n‐decane, isobutylbenzene, 1‐cyclohexylbutane, 1‐cyclohexylheptane, and 1‐cyclohexyldecane. Biobased barrier bags prepared from (2,2,6,6‐tetramethylpiperidin‐1‐yl)oxy oxidized CNF coated bio‐HDPE film protected the content to a great extent from mineral‐oil migration compared to noncoated bio‐HDPE and other commercial breakfast cereal‐bag films. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44586.     

Rheology modifier additive for enhanced processability of polyethylene for blown-Film applications

Polyethylene is a versatile polymer suitable for a large variety of flexible and rigid packaging applications. Its mechanical and rheological properties can be tuned across a wide range by controlling its molecular architecture, such as the amount and distribution of olefinic comonomers (short chain branching), long chain branching, and molecular weight distribution. Linear low-density polyethylene (LLDPE) is known for its high toughness which enables downgauged film structures and low-density polyethylene (LDPE) is known for its excellent shear thinning and melt strength which enables enhanced processability and high throughput, such as on blown film lines. In order to obtain a balance of toughness and processability on films produced on blown film lines, blends of LLDPE and LDPE are commonly used. In this paper, we describe additive-based approaches, including a new product, DOWLEX™ (TM = trademark of the Dow Chemical Company (“Dow”) or an affiliated company of Dow) GM AX01, which enhances melt strength and other rheological properties of polyethylene, enabling fabrication of films with lower LDPE content while still maintaining excellent rheological properties and higher toughness versus conventional LLDPE/LDPE blends. The higher toughness enables downgauging without loss of mechanical properties, which in turn reduces consumption of polymer resulting in a more sustainable solution.     

新型防静电软塑包装复合材料研究及应用

通过探索导电炭黑填充量对薄膜导电性能的影响,优选了油炉法炭黑。将油炉法炭黑和聚乙烯(PE)树脂混炼造粒,制得半导电粒子,采用三层共挤吹膜工艺和电晕处理技术,制得高表面能防静电PE薄膜;将该薄膜与其它基材复合成物理力学性能优异的防静电软塑包装复合材料。该复合材料被广泛应用于对静电及电磁辐射敏感的电子、化工及军工产品的包装,起到良好的防静电、抗电磁干扰等防护作用。     

Mechanical properties and morphology of polylactide,linear low‐density polyethylene,and their blends

Melt blending of linear low density polyethylene (LLDPE) and polylactide (PLA) was performed in an extrusion mixer with post extrusion blown film attachment with and without compatibilizer‐grafted low density polyethylene maleic anhydride. The blend compositions were optimized for tensile properties as per ASTM D 882‐91. On the basis of this, LLDPE 80 [80 wt % LLDPE and 20 wt % poly(L ‐lactic acid) (PLLA)] and MA‐g‐low‐density polyethylene 80/4 (80 wt % LLDPE, 20 wt % PLLA, and 4 phr compatibilizer) were found to be an optimum composition. The blends were characterized according to their mechanical, thermal, and morphological behavior. Fourier transform infrared spectroscopy revealed that the presence of compatibilizer enhanced the blend compatibility to some extent. The morphological characteristics of the blends with and without compatibilizer were examined by scanning electron microscopy. The dispersion of PLLA in the LLDPE matrix increased with the addition of compatibilizer. This blend may be used for packaging applications. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Rigid urethane foams from blown castor oils

Solvent-blown rigid urethane foams prepared from a low-cost polyol mixture composed of raw castor oil and triisopropanolamine have been described. Foams with higher compressive strengths can be obtained by substituting oxidized (blown) castor oil for the raw castor oil in formulations of this type. The properties of rigid foams prepared from several commercial blown castor oils are described. The properties of these foams are correlated with the degree of oxidation of the blown oils used, as indicated by their oxygen content, density, viscosity, and refractive index. Removal of acid from blown oils having high acid values has no significant effect on the compressive strength of foams prepared from these oils. When blown castor oil is used instead of raw castor oil, less isocyanate is required to produce a urethane foam of specified density and compressive strength. Presented at the AOCS meeting in Toronto, Canada, 1962. A laboratory of the W. Utiliz. Res. & Dev. Div., ARS, U.S.D.A.     

PE/EVA/分子筛复合保鲜膜对菠菜的保鲜作用研究

以聚乙烯(PE)/乙烯-醋酸乙烯共聚物(EVA)为基体树脂,分别添加2.5 %、5 %、7.5 %、10 %分子筛,自行吹制PE/EVA/分子筛复合气调包装膜,并对新鲜采摘菠菜进行常温保鲜包装研究。测定了保鲜膜的拉伸强度、断裂伸长率和撕裂强度,对菠菜包装的保鲜效果进行感官评价。研究了随着分子筛含量的增加,菠菜失重率、可溶性固形物和呼吸强度的变化。结果表明：室温下添加EVA和分子筛可增大PE保鲜膜的气体透过性,有效抑制菠菜的呼吸作用。当分子筛含量为7.5 %时,薄膜的保鲜性能最好。气调保鲜包装的平衡气体浓度为O2含量8.7 %~9.3 %、CO2含量7.2 %~7.7 %。PE/EVA/分子筛复合保鲜膜比纯PE膜更适于菠菜的保鲜。     

Commercialization of high oleic canola oils

High oleic canola oils were developed through plant breeding in the 1980's as a trans fat solution. More than 25 years after its initial launch, high oleic canola oils include a series of products with fatty acid profiles tailored for both foodservice and food processing. High oleic canola oil has taken most of the market for trait enhanced oils while other specialty oils have either seen significant market share reduction or failure. High oleic canola oils with 23%–27% linoleic acid are ideal for fried foods, while those with less than 20% are most suitable in the manufacture of shelf stable foods. In addition to improved nutrition, the next generation of high oleic canola oils will significantly reduce packaging costs.     

Structure-property relationships in blends of linear low- and conventional low-density polyethylene as blown films

Three-layer coextruded blown (either blend or composite) films, made of low-density polyethylene and linear lowdensity polyethylene (1:1 ratio) of identical density, were compared. The tensile properties of both systems are nearly as high as those of the linear polyethylene while high strain rate properties including impact strength and tear resistance of the composite film are superior. Some structural insight was obtained by thermal analysis and thermoelastic measurements. Structure property relationships are discussed in light of the unique behavior, structure, and morphology of linear low-density polyethylene. The two polyethylenes are only compatible to a rather limited extent mainly affecting their blend behavior. However, a strong mutual reinforcement effect was observed.     

PVDC薄膜的阻隔性与加工技术

PVDC吹塑薄膜、层合膜和共挤出流延薄膜是高阻隔性的包装材料。PVDC树脂加工过程中易分解和它的结晶特性使它需采用特殊的加工设备和工艺。通过对薄膜生产过程的分步模拟,其结果解释了工艺中冷水槽、温水槽、拉伸比、室温存放中的有关结晶现象,有助于认识加工过程,指导PVDC产品的加工工艺及提高产品性能。     

食用菌制全降解包装材料的研究

为了解决不可降解的废弃塑料类包装材料对环境的污染,以秸秆和木屑为主要原料,利用食用菌栽培技术制备了一种新型的、可完全降解的包装材料。采用对比实验的方法,研究了不同原料配比对菌丝生长情况的影响,结果表明,在秸秆57%、木屑30%、麸皮10%、石膏1%、石灰2%的配比下,选用平菇菌种栽培的培养基菌丝体含量最多,紧实度最好。通过材料的防水性能测试和缓冲性能比较,表明该生物质材料完全可以替代EPS(发泡聚苯乙烯)和EPE(发泡聚乙烯)等包装材料。同时,该生物质材料在土壤中可实现完全降解,为土壤提供有机肥料。     

Optical properties of blown and cast polyethylene films: Surface versus bulk structural considerations

In this article we report on some surprising, and we believe new, findings regarding the factors affecting the optical properties (haze) of polyethylene blown and cast films. A comprehensive investigation of blown and cast films made from conventional Ziegler‐Natta catalyzed linear low density polyethylene (LLDPE) as well as metallocene‐catalyzed LLDPE (mLLDPE) resins was conducted. The large majority of the contribution to the total haze in the blown and cast films was observed to come from the surface roughness of the films, with the bulk (internal) contribution being relatively minor. Using a variety of analysis and characterization methods, including atomic force microscopy, small angle light scattering, and wide angle X‐ray scattering, we determined that the surface roughness in these films was a result of the development of distinct spherulitic‐like superstructures formed during the blown or cast film processing. Furthermore, these superstructures were observed only in the mLLDPE blown films, and not in the LLDPE blown films processed at similar conditions. Analysis of the rheological and molecular characteristics of these various mLLDPE and LLDPE resins revealed that the mLLDPE resins exhibited considerably lower molecular weight, narrower molecular weight distribution, lower zero shear viscosity, and lower melt elasticity compared with the LLDPE resins of similar melt index. These observations support our general finding and primary conclusion from this work that in polyethylene blown and cast films made using typical processing conditions, the optical haze properties are adversely affected because of enhanced surface roughness caused by the formation of spherulitic‐like superstructures in polymer melts that possess fast relaxing and low melt elasticity rheological characteristics. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 2845–2864, 2000     

Effect of clay on mechanical and gas barrier properties of blown film LDPE/clay nanocomposites

Low density polyethylene (LDPE)/clay nanocomposites, which can be used in packaging industries, were prepared by melt‐mix organoclay with polymer matrix (LDPE) and compatibilizer, polyethylene grafted maleic anhydride (PEMA). The pristine clay was first modified with alkylammonium salt surfactant, before melt‐mixed in twin screw extruder attached to blown‐film set. D‐spacing of clay and thermal behavior of nanocomposites were characterized by Wide‐Angle X‐ray Diffraction (WAXD) and differential scanning calorimetry (DSC), respectively. WAXD pattern confirmed the increase in PEMA contents exhibited better dispersion of clay in nanocomposites. Moreover, DSC was reported the increased PEMA contents caused the decrease in degree of crystallinity. Mechanical properties of blown film specimens were tested in two directions of tensile tests: in transverse tests (TD tests) and in machine direction tests (MD tests). Tensile modulus and tensile strength at yield were improved when clay contents increased because of the reinforcing behavior of clay on both TD and MD tests. Tensile modulus of 7 wt % of clay in nanocomposite was 100% increasing from neat LDPE in TD tests and 17% increasing in MD tests. However, elongation at yield decreased when increased in clay loading. Oxygen permeability tests of LDPE/clay nanocomposites also decreased by 24% as the clay content increased to 7 wt %. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Optimisation of bubble size in qc rotationally moulded parts

Abstract

Rotational moulding is one of the most important methods of manufacture of hollow plastic products. However, there are several unsolved problems that confound the overall success of this technique, including surface pin holes and internal bubbles of moulded parts, caused by inappropriate mould design and processing conditions. In this report, an L′18 experimental matrix design based on the Taguchi method was conducted to optimise the bubble size of rotationally moulded parts. Experiments were carried out on a laboratory scale biaxial rotation moulding unit. The polymeric material used to mould the parts was linear low density polyethylene. After moulding, the size of the bubbles on the surface of moulded parts was characterised by an image analysis system. For the factors selected in the main experiments, the cooling conditions and the particle size of the material were found to be the principal factors affecting the bubble size of rotationally moulded thermoplastics. In addition, mould pressurisation helped decrease the size of the bubbles. The bubble size of moulded parts was not affected by the water content of the polymeric powder, but increased with the viscosity of the materials.     

熔喷/干法纤网在线复合汽车吸音棉的生产工艺

为了实现熔喷/干法纤网复合汽车吸音棉的在线生产,以开发300 g/m2的复合吸音棉为例,对熔喷工艺、干法纤网工艺以及熔喷/干法纤网在线复合等内容进行了分析介绍。结果表明:采用熔融指数150 g/min的聚丙烯切片,并控制好模头温度、热空气喷射角、热空气压力、接收距离等熔喷工艺参数,采用纤度为3.3 dtex的三维卷曲涤纶中空短纤维和阻燃涤纶短纤维组成的干法纤网,纤网加入熔喷丝的角度在75～83°之间时,能够得到较好的复合吸音棉材料。     

Effect of starch on thermal,mechanical, and barrier properties of low density polyethylene film

Low‐density polyethylene (LDPE) with different quantities of starch was compounded using a twin screw extruder and blown into films by a Konar K, blow‐film machine. Mechanical properties, namely percent elongation, tensile, bursting, and tear strength, as well as barrier properties, such as water vapor and oxygen transmission rate, of the filled LDPE film were studied. Thermal properties of the films were studied using DSC and DMA. Master curves at reference temperature of 30°C were obtained using software linked to DMA. Incorporation of 1% starch in LDPE has marginally affected the thermal, barrier, and mechanical properties; however, that of 5% starch filled LDPE has affected the properties to a great extent. The mechanical properties, such as percent elongation, tensile, tear, bursting, and seal strength, decreased by 19.2, 33.6, 3.60, 10.8, and 22.12%, respectively. Similarly, water vapor and oxygen transmission rate increased to 32.5 and 18.3%, respectively. Other physical properties, namely migration and thermal properties, were also affected in 5% starch filled LDPE; however, the film can still be used as packaging material. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 99: 3355–3364, 2006     

塑料压力管道热熔对接焊机的研制与开发

研制了基于80C196单片机控制的塑料压力管道热熔对接焊机，介绍热熔对接焊机的基本组成部分以及各部分的主要功能，分析高密度聚乙烯管道热熔对接焊接头的拉伸性能，冲击性能和抗开裂性能，并与母材和国外焊机焊接的接头性能进行了比较。     

The effects of e‐beam crosslinking of LDPE on the permeation of hydrocarbons

Polyethylene is a useful material in numerous applications, such as packaging, fuel tanks as well as oil and gas pipes. However, it must be considered that polyethylene is permeable to gases and liquids. Small molecules, such as hydrocarbons, may permeate through the material and cause environmental problems. Consequently, a particular aspect of polymer materials is the requirement of a high permeation resistance against low‐molecular‐weight hydrocarbons. Modifications of the commonly used polyethylene material are necessary to achieve adjusted permeation properties. In this contribution, the effect of electron‐beam crosslinking of polyethylene on the resulting permeation characteristics was investigated. Polyethylene sheets were processed and crosslinked by irradiation with high energy electrons. The formation of a network structure was characterized by gel content determination and by rheological measurements. The permeation properties of the polymer sheets were assessed by a gravimetric method. It is demonstrated that—as a result of the crosslinking process—the permeation of low molecular weight hydrocarbon through polyethylene is reduced with respect to the chain length of the aliphatic substances. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44968.     

Orientation and crystalline morphology of blow molded polyethylene bottles

A study was carried out of the development of orientation during processing of conventional blow molded bottles made from low density polyethylene (LDPE), linear low density polyethylene (LLDPE), and high density polyethylene (HDPE). The level of molecular orientation was found to be relatively low in all of the polyethylene bottles examined; it increased with increasing inflation pressure and decreasing extrusion temperature. Pole figures for the HDPE bottles indicated a slight a-axis orientation toward the circumferential direction of the bottle. The b-axes, which correspond to the lamellar growth direction, tend to be parallel to the bottle thickness direction. A comparison was made of the structure developed in blow molded bottles and blown films. The results for both films and bottles indicate that crystallization during processing involves both an increase in level of molecular orientation and an increased tendency toward biaxiality. Based on pole figures and small angle X-ray scattering patterns, a morphological model for HDPE blow molded bottles is proposed.     

Properties of high‐density polyethylene filled with waste crosslinked foam

Crosslinked polyethylene foam is widely used in packaging and as an insulation material. Finely ground waste of such crosslinked foam mesh size 7 or particle size less than 2815 μm is used as a filler in high‐density polyethylene (HDPE) of two different grades (7.5 and 21 MFI). Mechanical, thermal, and morphological properties of filled composites is studied experimentally. Waste foam powder concentration was varied up to 40% by weight basis. Impact strength of base HDPE increased by a factor of six. The overall changes in mechanical properties are similar to the crosslinking effect. It is believed that waste foam particles act as a point of entanglement with different chains of polyethylene. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 110–114, 2004     

Monitoring food quality - effect of curcumin in the development of polyethylene/thermoplastic starch based smart packaging

Smart packaging relies on the one-to-one interaction of food with its packaging or its environment to monitor food quality and safety. Colorimetric pH indicators (synthetic, natural) working in a smart food packaging system are particularly striking when used with fresh foodstuffs such as fish and meat that perish quickly and require real-time freshness monitoring. In this study, curcumin (Cur) was used as a natural pH indicator to produce sustainable smart packaging material. Towards this objective, low-density polyethylene (LDPE) and thermoplastic starch (TPS) blend-based films containing Cur were prepared using a twin screw extrusion and hot-pressing processes. Besides, two different compositions of LDPE/TPS mixture (50/50 and 70/30) were used as the matrix. Thermal, mechanical, morphological properties, an affinity for water, and color change properties of LDPE/TPS/Cur films were investigated. They showed a significant color change from yellow to brown at pH: 10 at the end of the seventh day, especially in the 50 LDPE/50 TPS mixture. 50 LDPE/50 TPS mixture with 7% curcumin content gave the highest tensile strength of 8.03 Mpa. When the same mixture was used to monitor chicken meat spoilage at 25°C, meat samples have shown color changes from light yellow to light brown due to the increased content of total volatile basic amines. As a result, it has been suggested that 50 LDPE/50 TPS mixture containing 7% Cur can be used as a smart packaging material.