The Effect of Flame Treatment on Surface Properties and Heat Sealability of Low‐Density Polyethylene Coating

The target of this study is to investigate the correlation between surface properties and heat sealability of flame‐treated low‐density polyethylene (LDPE) coating because it is vital to know how to modify the surface properties of LDPE coating without losing the heat sealing properties. Flame treatment showed a significant effect on the heat sealing properties of LDPE‐coated paper. For example, the heat sealing temperature of LDPE coating decreased or alternatively doubled, depending on the equivalence ratio (air–propane ratio) of flame treatment. In addition, the hot tack strength was significantly enhanced by flame treatment, which broadened the hot tack window of LDPE‐coated paper. The reason for the heat sealing performance of flame‐treated LDPE coating was believed to be related to the simultaneous reactions, that is, cross‐linking and chain scission, occurring on the LDPE surface. The molecular weight of LDPE surface increased or decreased, depending on the dominating reaction during flame treatment. This affected the chain mobility and the amount of chain interdiffusion across the seal interface and finally defined the heat sealing performance of LDPE‐coated paper. Copyright © 2012 John Wiley & Sons, Ltd.     

Adhesion behavior of natural rubber‐based adhesives crosslinked by benzoyl peroxide

The loop tack, peel, and shear strength of crosslinked natural rubber adhesive were studied using coumarone‐indene and toluene as the tackifying resin and solvent, respectively. The concentration of benzoyl peroxide‐the crosslinking agent—was varied from 1 to 4 parts per hundred parts of rubber (phr). A SHEEN hand coater was used to coat the adhesive on the polyethylene terephthalate substrate at various coating thickness. Loop tack, peel, and shear strength were measured by a Llyod adhesion tester operating at 30 cm min^?1. Result shows that loop tack and peel strength of the adhesive increases up to 2 phr of benzoyl peroxide concentration after which it decreases with further benzoyl peroxide content. This observation is attributed to the optimum crosslinking of natural rubber where optimum cohesive and adhesive strength occurs at 2 phr peroxide loading. However, for the shear strength, it increases with increasing benzoyl peroxide concentration where higher rate of increase is observed after 2 phr of peroxide content, an observation which is associated to the steady increase in cohesive strength of crosslinked rubber. In all cases, the adhesion properties of adhesives increase with increase in coating thickness. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Terpolymers Composed of Ethyl Acrylate, Methoxypolyethyleneglycol Methacrylate and Methoxypolypropyleneglycol Methacrylate as Pressure Sensitive Adhesives and their Blood Compatibility

Terpolymers composed of ethyl acrylate (EA), methoxypolyethyleneglycol methacrylate (MPEGMA) and methoxypolypropyleneglycol methacrylate (MPPGMA) were synthesized by the photopolymerization technique. The high molecular mobilities for these terpolymers were shown by dynamic contact angle and adhesion tension measurement. The 180-degree peel strength and probe tack for pressure sensitive adhesives (PSA) made of these terpolymers were good but the holding power was not enough to apply them as PSAs. It was found that these terpolymers should be modified to obtain high holding power. The blood compatibility of these terpolymers was also investigated. It was found that they had a significant blood compatibility. Thrombi were not observed on the terpolymer surface after immersion in blood while, on a polystyrene (PSt) surface, many blood clusters were observed. After immersion in platelet-rich plasma (PRP), a few adhered platelets were observed on terpolymer surface but they did not deform and maintained their spherical form, while many platelets were observed on polystyrene.     

Adhesion of a Rigid Punch to a Thin Elastic Layer

Adhesion between a rigid flat cylindrical punch and an elastic layer has been investigated. FE analysis was employed to determine the layer stiffness. Linear elastic fracture mechanics was then used to determine the energy release rate, G_a, per unit of bonded area for a circular debond propagating inwards from the edge of the punch. The calculations showed a strong effect of Poisson's ratio for thin layers, small departures from complete incompressibility causing large reductions in stiffness and hence in detachment force. Experiments were performed with an aluminum punch adhered to a rubber layer using a rubber-based adhesive. The ratio of punch radius to layer thickness was varied over the range 0.07 to 3.3. Detachment forces were measured and compared with calculated values. Reasonable agreement was obtained for thick layers but not for thin ones, possibly because of a change in the mode of failure.     

Vegetable oil-based printing inks

Nearly 75 black and 25 colored inks consisting of 100% vegetable oil-based vehicles were formulated. The physical properties of these inks met or exceeded the industry standards for lithographic and letterpress newsprint applications. In addition, elimination of petroleum-based resin and reduced pigment usage, due to the light vehicle color, provided a competitively priced alternative to petroleumbased inks. The mention of firm names or trade products does not imply that they are endorsed or recommended by the U.S. Department of Agriculture over other firms or similar products not mentioned.     

无线传感器网络中检测女巫攻击的节点定位方法

为了有效抵制女巫攻击,在攻击存在的情况下提高无线传感器网络节点的定位精度,分析、总结了女巫攻击所固有的薄弱环节,提出了基于接收功率验证的检测女巫攻击的节点安全定位方法。检测机制分为两步,首先检测节点通过比较接收功率,从所接收的全部信标节点中选择出距其距离相同的信标节点,列为可疑Sybil节点,然后通过邻居节点间的信息交互和距离验证,最终检测出攻击节点,利用去除了Sybil节点的信标节点集合实现定位。仿真实验显示,当存在攻击时,检测成功概率能达到95%以上,定位精度提高了9～11.64 m,表明该方法能有效检测女巫攻击,实现节点安全定位。     

Rheology and adhesive properties of filled PIB-based pressure-sensitive adhesives. II. Probe tack and 90° peel testing

Two nanosized fillers (fumed silica Rosil-175 and halloysite nanotubes) were used to eliminate the problem of the cold flow and to increase the adhesion strength for polyisobutylene-based formulations. Well-dispersed silica, having high specific area, allowed to obtain up to 2 orders of magnitude increase in PIB’s shear resistance at 20 wt% Rosil content. PIB–20 wt% Rosil formulations mostly demonstrated slightly increased tack characteristics – up to 20–50%. Adhesive peel of the PIB-Rosil systems was observed with the peel strength of the systems staying at the level of the pristine PIB matrices or slightly changing (depending on the film thickness and peeling rate). Transition to the mixed failure mode was observed for thin PIB-20 wt% Rosil films tested under increased peeling rate accompanied by up to 300% peel strength increase. Formation of the three-dimensional filler networks in PIB-halloysite formulations allowed notably lower increase in the shear resistance of the systems – only 4–5 times in the case of much higher filler content (40 wt%), which was connected with the low strength of the network. Incorporation of 40 wt% halloysite into the PIB matrix did not lead to notable changes in tack properties, except for the tack of 150-μm films – in this case, 30–60% decrease in the tack characteristics was obtained. Peel strength of PIB-halloysite systems stays at the level of the pristine PIB matrices or increases up to 300% when the failure mode shifts from adhesive for the thin films to cohesive for the thick films.     

Adhesive properties of liquid crystalline hydroxypropyl cellulose–propylene glycol blends

Adhesion (tack) of the liquid crystalline hydroxypropyl cellulose–propylene glycol (HPC/PG) systems has been studied under various loading modes as well as their rheology and phase state. The system with the optimum tack according to the Dahlquist criterion (HPC/PG?=?85/15 wt.%) was chosen based on its rheological properties (viscosity, storage and loss moduli at 20 and 50?°C). Tack measurements were carried out for this system. Rheological measurements revealed the presence of the critical stress detected by the abrupt drop of viscosity. The adhesive behavior of the system deviates significantly from one of the conventional pressure sensitive adhesives (PSAs): almost no tack is observed when using contact force and contact time typical for a PSA. To achieve good adhesion with this system one needs substantially higher pressure and contact time. At 20?°C, adhesive failure is observed in most cases and high contact forces (over 500–600?g) are required to overcome critical stress and obtain noticeable tack characteristics. At 50?°C, fibrillation and cohesive failure are usually observed with some residue of the system on the probe after debonding. Usage of high contact forces (600–1000?g) and contact times (up to 1000?s) allows us to reach significant values of the maximum debonding stress (up to 1.25?MPa) and energy (up to 420?J/m²). These values are on the same level or even higher than the corresponding values for standard PSAs.     

一种自主研发的高渗透乳化沥青的应用

对高渗透乳化沥青在国内外的应用情况进行了简单分析,介绍了自主研发的新型高渗透乳化沥青的开发及应用。该高渗透乳化沥青应用效果良好,市场前景广阔。