Layflat

The layflat-LDPE tubing used for making SPMDs was 2.6 cm wide and had a wall thickness of about 75 pm. The A of the 0.5 mL triolein SPMDs used in these flow-through tests was about 200 cm with an AV (lipid -I- membrane) ratio of about 80 cm The A of the 1 mL triolein SPMDs used in the static exposures was about 360 cm (i.e., = 72 cm ). The surface area of the 1 mL lipid... 

The design of commercially available SPMDs consists of a specified length (e.g., 91.4 cm between the inner-LDPE welds for 1 mL of triolein) of additive free, 2.5 cm wide layflat LDPE tubing. The LDPE wall thickness ranges between 70-95 pm and the triolein used is >95% purity. Note that in the USA, all commercially available SPMDs are fabricated with >99% purity triolein. The A y ratio is about 90 cm cm (lipid plus membrane), or about 460 cm mL of triolein. The standard SPMD thereby consists of approximately 20% triolein. For the 1 mL triolein configuration, the whole device typically weighs about 4.4 to 4.6 g. 

Portex blue nylon layflat sheeting for bags (BDH-Merck Ltd., Poole, UK)... 

Plasticized PVC can be extruded in various forms—including layflat film for bags and other containers with gusseted walls, flexible pipework, hoses, and continuous seals in many different configurations. 

Trade name of explosives in layflat charges used in seismic prospecting for surface shooting in combination with Dynacord. Both products are manufactured and distributed by DYNAMIT NOBEL, Troisdorf, Germany. 

The blown film process involves extruding a relatively thick tube that is then expanded or blown by the usual internal air pressure or the water quench process to produce a relatively thin film (Figure 5.6). The tube can be collapsed to form double-layer layflat film or can be slit to make one or two single-layer film webs. The water quench process is the generally preferred method of producing blown PP type film. 

In addition to the upward blown film there is also the downward extrusion. It allows the tube to be quenched rapidly in a water bath after which it is collapsed as a layflat for passage over nip and idler rollers. 

A standard SPMD consists of 91.4 cm long, 2.5 cm wide layflat tube of low density polyethylene (LDPE) membrane and 1 ml of > 95% or > 99% purity triolein (Huckins... 

The semipermeable membrane device (SPMD) is a thin-walled, layflat polyethylene tubing that contains approximately 1 g of a lipid, triolein (600 molecular weight), that cannot diffuse through the polyethylene bag. The SPMD was invented by Huckins and co-workers (1993). The principle of the SPMD is that it is a passive sampler for nonionic organic substances in water... 

The size of the nip rolls and all downstream idle rollers, known as the roll face width, determines the maximum layflat width that the system is capable of producing. The layflat width is related to the bubble diameter by the following equation BD = 2 LF/tr (where BD = bubble diameter and LF = layflat). 

The final control variable is frost-line height. The position of the frost line is very sensitive to any changes in the process. Therefore, this is an excellent parameter to track as a measure of stability during a run. Any changes in ambient or process temperatures, line or screw speed, or material feed conditions will affect the frost-line height. This, of course, will lead to variations in film gauge and layflat as well. 

Figure 3.22 A laser gauge is used to measure layflat width...

The BUR is the ratio of bubble diameter (Dj,) to die diameter (U ), i.e., BUR = D ID. This quantity provides an indication of the amount of stretching, hence orientation, in TD. The bubble diameter is established by the control system and can be either measured directly or calculated by measuring the layflat (LF) width directly (D, = 2 LF/tt). The die diameter is fixed. 

State the mathematical relationship between layflat (LF) width and bubble diameter (BD). 

Record the film thickness, bubble diameter, layflat width, and frost-line height. (Note control panels can be dragged from their top center)... 

Return the screw speed to 20 RPM. Set the nip roller speed to 35 feet/minute and the blower speed to 110 cubic feet/minute. String the bubble onto the winder. Establish an 8.0 in layflat. 

Record the film thickness, bubble diameter, layflat width, and frost-line height. 

This equation is used to calculate the layflat width if the bubble diameter is known. More often, however, the layflat width is measured, then the bubble diameter can be... 

In 1978, Moldflow introduced commercial software on a worldwide computer time-sharing system. This software enabled users to determine process conditions (melt temperature, mold temperature, and injection time) and to balance flow in cavities and runner systems. Although accepted at the time, this software was difficult to use as it required the user to produce a layflat. ... 

The layflat was a representation of the part under consideration that reduced the problem of flow in a three-dimensional geometry to flow in a plane. For example, consider an open box with a thickened lip at the open end. If the box is to be injected at the center of its base, a potential problem could arise from polymer flowing aroimd the rim of the box and forming an airtrap (Fig. 7.56). The layflat of the box is shown in Fig. 7.57. As can be seen, the box has been folded out to form the layflat. Analysis could now be done on the various flow paths on the layflat. For example, the results of such analysis could be used to thicken the sections shown to promote flow and so prevent the flow of material around the thickened rim. While this type of analysis was undoubtedly useful, it did require considerable skill on the part of the user to produce the layflat and optimize the various flow paths. 

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