Evaluation and optimization of seal behaviour through solid contamination of heat‐sealed films

A method is presented to apply solid powder/granulate contamination (ground coffee and blood powder) in between the heat conductive seals of flexible packaging materials. A response surface method is tested and validated to optimize seal strength of heat conductive sealing with and without solid contamination. In this study, a maximal seal strength is defined as optimal. Using these methods, three typical packaging films with varying seal layer composition (metallocene linear low‐density polyethylene (LLDPE), plastomer, and sodium ionomer) are maximized towards contaminated seal strength. Contamination caused a decrease in seal strength and narrowed down the process window (seal temperature and time combinations) in which at least 90% of the maximal strength is obtained. The influence of seal layer composition on the clean and solid (ground coffee and blood powder) contaminated seal performance (seal strength, process window, and leak tightness) was evaluated. The film with the plastomer‐based seal layer outperformed the other films with respect to the width of the process window. It also reached a higher seal strength and a higher amount of leak tight seals (evaluated with the dye penetration test) after optimization. The hot tack test was evaluated as predictive test for the contaminated seal strength. The results of this study do not support an indicative relationship.     

Bonding and Debonding Processes in Tack of Pressure-Sensitive Adhesives

Rolling friction coefficient of two acrylic pressure sensitive adhesives (PSAs) are measured as a function of velocity at several temperatures. It is found that the time (or velocity)-temperature superposition procedure is applicable for one PSA, while it is not for the other. The authors came to the conclusion that the rate of increase of the true contact area is different for the two adhesives. The time-temperature superposition is possible only in the case where the activation energy of the bonding process is equal to that of the debonding process.     

Evaluation of the shear characteristics of steel–asphalt interface by a direct shear test method

Shear characteristics of steel–asphalt interface under the influences of temperature, normal stress level and tack coat material were investigated. The direct shear tests were conducted on composite specimens with epoxy asphalt (EA) and polymer modified asphalt (PMA) tack coat materials at temperatures of 25 and 60 °C and normal stress levels of 0, 0.2, 0.4, and 0.7 MPa for each temperature. Results show that the failure modes include adhesive failure at the primer-tack coat interface and material failure of asphalt concrete. Steel–asphalt interface shows strain softening behavior until it reaches the sliding state. The shear strength and the shear reaction modulus increase with decreasing temperature and increasing normal stress levels. The specimens with EA tack coat provides much higher interface shear strengths than those with PMA tack coat at 25 and 60 °C. In addition, the failure envelopes of the shear strength and residual shear strength were obtained for combinations of tack coat materials and temperature conditions based on the Coulomb failure law.     

苯乙烯系热塑性弹性体类压敏粘合剂的失粘──Ⅱ

研究了以热塑性弹性体为基料的压敏粘合剂失粘的原因。试验了基料中苯乙烯含量、固态增粘剂用量、物理形态、贮存期、液态增粘剂用量和芳香系石油树脂用量和形态,增塑剂用量和胶层厚度等对压敏粘合剂的抗失粘性能的影响。     

Novel Dynamic Viscoelastic Measurements of Polyurethane Copolymer Melts and Their Implication to Tack Results

Summary: A series of polyurethane multiblock copolymers with different proportions of hard segments (urethane) to soft segments (polyadipate of hexane‐1,6‐diol), are investigated. Dynamic viscoelastic functions of homogeneous melts in the terminal zone are determined. For the first time, entanglement modulus values of such copolymers are reported, which allows estimation of the packing length. These parameters do not vary with changing the hard‐to‐soft segment ratio, a result that is explained by a compensating effect of the chain architecture. For samples of similar molecular weight, the relaxation time of the terminal zone increases as the hard‐to‐soft segment ratio augments. The adhesives obtained from PUR solutions show a correlation between the elastic modulus and the debonding stress‐strain curves in tack experiments.

The storage modulus of the adhesives as a function of frequency at 70 °C.     

大型气柜底板焊接变形的控制

分析了焊接应力和变形产生的原因,并提出相应的预防措施、治理办法.     

丙烯酸酯乳液压敏胶合成及其常规性能研究

采用半连续种子乳液聚合法制得纯丙乳液压敏胶。研究了胶粘剂厚度、基材厚度、基材类型对压敏胶常规力学性能影响。结果发现,各因素对压敏胶的初粘性和剥离强度影响较大;基材厚度及类型对持粘性影响较小;胶层厚度为15μm左右的压敏胶具有较高性价比。     

丙烯酸酯类低聚物的制备及其在水性聚氨酯改性中的应用

以丙烯酸酯类低聚物(DJW-330)为改性剂、聚醚和异氟尔酮二异氰酸酯为原料,采用自乳化法合成了改性的水性聚氨酯(WPU)乳液。采用GPC、FTIR、DSC和荧光显微镜等方法对产物进行了结构表征及性能分析。实验结果表明,当采用分步法滴加引发剂偶氮二异丁腈(AIBN)和混合溶剂(丙酮和乙酸乙酯的体积比3∶4)时,AIBN用量(基于丙烯酸酯单体总质量)为0.4%~0.6%时可得到黏度和相对分子质量适中的DJW-330;当DJW-330用量(基于固体总质量)为1.4%时改性WPU的综合性能最佳,初黏度可达14号球,持黏度达100min,且乳液稳定性好。表征结果显示,DJW-330是以化学键的形式结合到WPU分子链中的,用DJW-330改性的WPU颗粒的粒径明显变大且改性的WPU胶膜的耐热性能有所提高。     

SmartPro在固相增粘装置上的应用

介绍固相增粘装置中利用SmartPro实现集散式控制系统的实施工作、组态方法以及应用效果。SmartPro主要包含ConMaker和Fac View两个软件包。ConMaker是用于控制方案的开发平台；Fac View是在线监控系统软件，也能运行工程编辑器、图形编辑器和代码编辑器。