YUPO's physical properties are very similar to wood based paper. However, due to stretching in the manufacturing process, the higher strength properties typically associated with the grain direction of wood-based sheet occur along the cross direction for yupo.
This is due to the preferential alignment of the long-chain polypropylene molecules during the final crosswise stretching operation. The traditional "grain" direction of yupo, therefore, is in the cross-direction.
The following table lists physical properties for yupo text and cover weight sheets. As with all paper, stiffness and tensile strength are higher in the grain direction. Tear resistance, however, is higher in the cross-grain direction since it is more difficult to tear across the polymer chains.
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