Shape recovery rate/ratio

Li et al. reported that immiscible high-density polyethylene (HDPE)/ poly(ethylene terephthalate) (PET) blends, prepared by means of melt extrusion with ethylene-butyl acrylate-glycidyl methacrylate (EBAGMA) terpoly-mer as a reactive compatibilizer, can exhibit shape memory effects [32]. They observed that the compatibilized blends showed improved shape memory effects along with better mechanical properties as compared to the simple binary blends. In the blend, HDPE acts as a reversible phase, and the response temperature in the shape recovery process is determined by of HDPE. The shape-recovery ratio of the 90/10/5 HDPE/PET/EBAGMA blend reached nearly 100%. Similar behavior was observed for immiscible HDPE/ nylon 6 blends [33]. The addition of maleated polyethylene-octene copolymer (POE-g-MAH) increases compatibility and phase-interfacial adhesion between HDPE and nylon 6, and shape memory property was improved. The shape recovery rate of HDPE/nylon 6/POE-g-MAH (80/20/10) blend is 96.5% when the stretch ratio is 75%. 

It is noted that while the majority of constitutive modeling focuses on thermally induced dual-shape memory behavior, triple-shape and multishape SMPs have been developed recently and they call for constimtive modeling [1]. In addition, the effect of programming temperature and strain rate on the constimtive behavior also needs modeling [2]. Furthermore, some recent smdies have found that while the shape recovery ratio can be 100%, other mechanical properties such as recovery stress or modulus become smaller and smaller as the thermomechanical cycles increase, which has been explained by the shape memory effect in the microscopic scale [24]. Obviously, these new findings also call for constitutive modeling. 

The desorption behavior of the liver cells on the PNIPAAm-grafted dish has been examined in detail. It was found that incubation at 10°C for 30 min followed by treatment at 25°C for 5 min provides a better recovery rate than treatment at only 10°C. Investigation of cell morphology revealed that the cells showed a flat shape when they were incubated at 10°C for 30 min, whereas when they were subjected to 25°C, they became spherical and desorbed. If the cultured cells are treated by a metabolism inhibitor, sodium azide, the desorption ratio decreased. With low-temperature treatment, the grafted PNIPAAm molecule started hydrating. The hydration process initiates desorption of the substrate dependent cells, with the result of this sodium azide treatment suggesting that both cellular metabolism and desorption are altered. It is also suspected that the aforementioned variations in desorption temperatures might vary fi-om cell type to cell type as a result of temperature-sensitive metabolism processes of different cells. 

Tensile tests were performed (ASTM D 882) at room temperature and at 60°C using Instron 4204 machine equipped with a heating chamber. Shape memory properties were evaluated as follows Samples were stretched at 60°C and a strain rate of 50 mm/min to predefined stretching ratios of 30%, 60% and 100%. Upon completion of stretching, samples were cooled down quickly to room temperature with the aid of a fan. Shape fixity was calculated from the values of sample lengths before and after stretching. Shape recovery test was conducted using a smaller sample cut from the middle section of the stretched specimen. The recovery stress was obtained from the peak value of stress vs. time... 

When a recovery well is located within a contaminant plume and the pump is started, the initial concentration of contaminant removed is close to the maximum level during preliminary testing. As the pump continues to operate, cleaner water is drawn from the plume perimeter through the aquifer pores toward the recovery well. Some of the contaminant is released from the soil into the water in proportion to the equilibrium coefficient. For example, if the Kd is 1000, at equilibrium, 1 part is in the water and 1000 parts are retained in the soil. If the water-soil contact time is sufficient, complete equilibrium will be established. After the first pore volume flush (theoretically), the concentration in the water will be 0.9 and that on the soil will be 999. With each succeeding flush, the 1000 1 ratio will remain the same. If the time of water-soil contact is not sufficient to establish equilibrium, the recovered water will contain a lesser concentration. A typical decline curve is shown on Figure 9.2. Note the asymptotic shape of the curve where the decline rate is significantly reduced. 

In the plant used for academic purposes [4], both the solvent and exhausted CO2 are wasted. In an industrial plant both streams should be recycled after purification, for obvious economic reasons. The precipitator size and plant-flow-rates are obtained by increasing 80-fold the relative quantities used in the pilot plant [4]. This scale factor was suggested by the company that supplied the drug. Two vessels, P, in parallel are needed while the former is running, the latter can be cleaned and the solid product can be recovered. Cleaning and product-recovery expenses are not directly evaluated in this example. In the pilot plant, the flow of THF-polymer-drug solution was 0.072 kg/h, and the CO2 flowed in the quantity of 1.08 kg/h (the ratio CO2 to solution equals 15). The precipitator was a 0.4-liter vessel. The actual precipitator scale-up is not considered here. The main factor to consider in scaling-up the precipitator is the nozzle scale-up. The nozzle-size, nozzle-shape, and number of nozzles per reactor volume, determine the precipitate size in a complex and still incompletely understood way [5-8], It is assumed that issues related to the injectors are already solved. 

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