Machine direction , and

Paper made on a paper machine exhibits quite different properties in the x and y directions (the machine and cross machine directions), an example of which is a difference in stiffness which can be demonstrated by plotting the specific elastic stiffness in the x-y plane as a function of the machine direction and cross machine direction co-ordinates in the form of a polar diagram (Figure 4.7). 

Carbon dioxide gas was used as a physical blowing agent to produce medium density polypropylene foam sheets using a single screw extruder. The mechanical properties of the foam were similar in the machine direction and in the transverse direction. Abetter surface finish and a lower density was produced by using a commercial wrapping film as a cap layer. The process conditions and the die design data are presented and an attempt made to relate them to the product characteristics. 4 refs. 

Figure 7.55 Die-formed product nonuniformities (a) in the machine direction and (b) in the cross-machine direction. From Z. Tadmor and C. G. Gogos, Principles of Polymer Processing. Copyright 1979 by John Wiley Sons, Inc. This material is used by permission of John Wiley Sons, Inc.

Fig. 12.2 Die-formed product nonuniformities in (a) the machine direction, and (b) the crossmachine direction.

Reasonably linear relationships were found on these papers when logarithms of the average MD (machine direction) and CD (cross direction) folding endurance values were plotted vs. incubation time. Statistical calculations for these data are listed in Table IV, and the Arrhenius graph is shown in Figure 3. 

The die has substantial influences on the plastic due to the melt flow orientation of the molecules, such as having different properties parallel (machine direction) and perpendicular to the flow direction. These differences have a significant effect on the performance of the product. The die designs with melt condition (pressure, temperature, rate of travel, etc.) and its downstream equipment can provide the required unidirectional, bidirectional, or desired properties. The pressure usually ranges as follows ... 

The cured sheets were conditioned at 23 °C and 50% relative humidity. MIT folding endurance was run on 1.5-cm wide strips at 0.5 kg load. Tensile was taken on the same width strip. Eight strips were run machine direction and eight cross direction. As mentioned by Raff et al. (4,5), standard deviation and coefficient of variation were increased greatly in the treated plasticized paper for example untreated Foldur Kraft gave ... 

The test report is a guarantee for farmers, dealers and manufacturers because the machine directive and other national and international environment regulations provide for specific requirements and responsibilities. 

Note that any external coating (varnishes etc., solid print, bands of print) can have a direct effect on the curl of the paper, which is liable to occur when the paper is wetted or dried. This is because inks and varnishes stiffen the paper in both the machine direction and the cross direction. Coatings may vary from matt to high gloss. 

It has no machine direction, and it can withstand strong acids and bases. 

SVI should be measured in both machine and transverse directions to determine the extent of isotropy in the tube. If the SVI values are very low (< 1 %) in both directions or equal, the sample is isotropic. This means that the sample has been adequately sintered and stresses have been relieved. If the values are both high, sintering has been poor. If the transverse value is high and the machine direction value is low, then orientation is primarily in the machine direction and it is unbalanced. 

A homopol5mier of vinylidene fluoride was ex-trudedt J using a coat hanger die with a width of 590 mm to produce a sheet at a thickness of 150 pm at a die temperature of 270°C. A chill roll at a temperature of 70°C chilled the hot film. This film was biaxially oriented by four times the original length in the extrusion (machine) direction and six times in the transverse direction (perpendicular to the extrusion direction). The film was at a temperature of 100°C while it was oriented at a stretch rate of 10 mm/min in both directions. 

Oriented Films. Oriented multilayer films are prepared by stretching heated unoriented films. The film can be stretched in the direction coincident with the machine direction, or the direction perpendicular to the machine direction to obtain an uniaxially oriented film. A biaxially oriented film is stretched in both the machine direction and perpendicular to the machine direction. 

An advantage of the bubble processes is that the stretching in the machine direction and transverse direction are carried out simultaneously, which makes it rather easy to obtain completely balanced films. In addition, there are no thick edges to be trimmed, which gives the bubble process an economic advantage. 

The Type A performance requirements refer to BS 5438 1976, Test 3 where 3 specimens are tested in the machine direction and three in the transverse direction with a flame application time of 10 s. In each of at least 4 specimens, not more than 1 trip thread should be severed (both of the vertical ones count as one severance). If three trip threads (i.e. 300 mm, 600 mm and either of the vertical ones) are severed on any specimen, the fabric is deemed not to comply with the requirements of Type A, In addition, the material should be subjected to Test 2 of BS 5438 1976 using flame application time of 10 s where no part of any hole nor any part of the lowest boundary of any flame should reach the upper edge or either vertical edge of any specimen. 

Many efforts have been undertaken to overcome the mechanical anisotropy of in sim composites through processing [145-156]. In recent years, pre-extmded thermoplastic LCP sheets, strands, and fibers have been used to produce composites with a good balance in machine direction and transverse direction. Bassett and Yee [145] used a method consisting of spinning composite fibers... 

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