Perforated polyethylene

Specification No covering Nonwoven polypropylene Perforated polyethylene film... 

Table 2. Effect of nonwoven polypropylene and perforated polyethylene film covering on growth of early potato cultivars (Wadas Kosterna, 2007b Wadas et al., 2009)...

The tubular positive plate uses rigid, porous fiber glass tubes covered with a perforated plastic foil as the active material retainer (Fig. 2). Dry lead oxide, PbO, and red lead, Pb O, are typically shaken into the tubes which are threaded over the grid spines. The open end is then sealed by a polyethylene bar. Patents describe a procedure for making a type of tube for the tubular positive plate (90) and a method for filling tubular plates of lead—acid batteries (91). Tubular positive plates are pickled by soaking in a sulfate solution and are then cured. Some proceed directiy to formation and do not requite the curing procedure. 

Warehouse drying is normally aeeompllshed by providing an intermediate paekaging that breaths . In the ease of a rubber bale, the paekaging may eonsist of polyethylene perforated film wrap that enables the surfaee moisture to evaporate through the film wrap and achieve an acceptable moisture spec (typically less than 0.5 weight percent for products like EPDM or butyl rubber). 

Example 4 Design a flat, perforated-plate grid for the polyethylene reactor schematically shown in Fig. 11, and calculate the gas j et penetration depth. Use a triangular pitch. System parameters are ... 

Packed tower studies were made with a borosilicate glass column 4 inches in inside diameter packed with /4-inch ceramic Intalox saddles. The feed was metered through a rotameter from a constant-head tank, and distributed through the tower with a perforated aluminum plate. Aluminum tubing and polyethylene pipe were used to connect the ozone generator to the tower. A continuous sample was withdrawn from the tower bottom for analysis, and exit gas from the top of the tower was conducted to a wet-test meter for volume measurements. Ozone was absorbed in 5% potassium iodide solutions and titrated with thiosulfate to a starch end point. 

Abel et al. (1984) succeeded in expanding the linear range of a glucose electrode up to 40 mmol/1 by covering the enzyme membrane with a perforated hydrophobic polyethylene membrane. As applied subcutaneously and with a p02 of 2-5 kPa the sensor was stable for some hours (Fig. 134). 

For thermally sensitive or undoped polymers with low linear absorption at the laser wavelength, the use of femtosecond laser pulses can improve the ablation precision in contrast to long-pulse treatment. Further, the thermal load to the samples is minimized. For these reasons, femtosecond laser pulses were chosen to perforate a polyethylene membrane serving as a diffusion-discriminating element on a miniaturized biosensor for the measurement of glucose concentration [78]. 

Polyethylene shows a small linear absorption at the laser wavelength of 2=620 nm (a<10 cm"1). Strong fluence-dependent incubation could be observed for the structuring of polyethylene with 300-fs pulses in the visible spectral range. The application of N=100 pulses at F0=0.8 J cm-2 only leads to a surface modification (Fig. 24a). With 2 T=100 at F0=l-0 J cm 2, a perforation of the membrane can be achieved (Fig. 24c). For a fluence of 1.0 J cm"2, more than 20 pulses per spot are needed to produce detectable ablation (Fig. 24b). 

The delicate task was to perforate the polyethylene membrane with minor damage to the underlying enzyme (degradation temperature 80 °C), which is crucial for the operation of the whole sensor. 

Compared to hand-made perforations by means of a specially grinded needle (Fig. 27a,b), the use of a femtosecond pulse laser resulted in well-defined perforations of the polyethylene membrane (Fig. 27c,d). Obviously, the reproducibility of the laser-generated structures is higher (Fig. 27b,d). It was impossible to reach diameters smaller than 50 pm with the mechanical technique (Fig. 27a). The fs-laser structuring yields the opportunity to tune the... 

Fig. 27 Scanning electron micrographs of perforations of 30-pm-thick polyethylene membranes, (a, b) The perforations were produced mechanically by hand using a special grinded needle, (a) single perforation, (b) array of perforations, (c, d) Laser perforations employing t=300 fs, 2=620 nm, F0=bO J cm-2, (c) N=100, (d) N=100 per interleaf [78]...

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