The main objective of this study is to investigate the barrier mechanisms and properties of polyethylene, polyethylene (PE)/polyamide (PA) and polyethylene/modified polyamide (MPA) bottles against paint solvent permeation. In addition to the paint mixed solvent, the barrier properties of these bottles against the permeation of pure main solvents contained in the paint mixed solvent were investigated to understand the permeation mechanisms of the paint solvents. The paint solvent permeation resistance improves dramatically after blending PA and MPA barrier resins in PE matrices during blow‐molding. In fact, by using proper compositions, the white spirit permeation rates of PE/MPA and PE/PA bottles at 40°C are about 360 and 50 times slower than that of the PE bottle, respectively. Further investigations showed that, after blending the MPA and PA barrier resins in PE matrices, the hydrocarbon solvents present in the white spirit were nearly blocked without permeation during the permeation tests, i. e., PE/MPA bottles inhibited the permeation of hydrocarbon solvents more successfully than PE/PA bottles. In contrast, the rates of polar solvents with ketone, ether and alcohol functional groups permeating through the PE bottles are much slower than that of the white spirit and only slightly faster than those through the PE/PA and PE/MPA bottles. On the other hand, the paint mixed solvent permeation rates of PE bottles are approximately equal to the summation of permeation rates of the solvents present in mixed solvents calculated using a simple mixing rule. Somewhat surprising, the permeation rates of mixed solvents of PE/MPA bottles are dramatically faster than those calculated using a simple mixing rule, when the polar solvent contents are in a certain range. 相似文献
The genetic algorithm (GA) is a new optimization paradigm that models a natural evolution mechanism. The framework of the GA naturally corresponds to a discrete optimization problem. Although the GA is very robust, it is also very computationally intensive and hence slower than other methods. To speed up the convergence, this article proposes a hybrid GA that combines the concept of survival of the fittest with the concept of adaptation. The fully stressed design optimality criterion is employed to play the role of adaptation. Numerical examples show that even though the displacement constraints are active, (1) both average weight and minimum weight obtained by a hybrid GA are less than those obtained by a pure GA, (2) a hybrid GA is more stable than a pure GA, and (3) the speed of convergence of a hybrid GA is superior to that of a pure GA. 相似文献
New product introduction is vital to a firm's growth and prosperity. A company needs to develop a process to determine how to find and develop new product ideas and finally, how to successfully introduce them into the marketplace. To address this problem, this study proposes a new approach that combines neural network, analytic hierarchy process (AHP) and linear programming (LP). A neural network is used to classify the feasibility of ideas/projects in new product development and the theory of AHP is applied to evaluate the interdependence among projects. A linear programming model is then developed and used to allocate the limited financial resources of the firm to the competing projects. 相似文献