PLASTICS MATERIAL MESH STRUCTURES

摘要

In order to produce a non-cracky, integral, biaxially-oriented plastics material mesh structure 15 having a high strength/weight ratio, having high MD (machine direction) strength and substantially greater strength in the MD than in the TD (transverse direction), and having high creep resistance, a starting material 1 is provided having a rectangular grid of holes 8 and the starting material 1 is stretched in the MD (Figure 3) to such an extent that the junctions are not significantly oriented, is stretched in the TD (Figure 4) to such an extent that the junctions are not significantly oriented, and is finally stretched in the MD (Figure 5) to such an extent that the junction centres thin down by at least 30% and there is significant narrowing down of the junction. The resultant MD stretch is substantially greater than the resultant TD stretch. The MD strands 12 min , having thinned down and oriented to a substantial degree, cause the orientation to pass into the ends of the junctions and right through the junctions. The junctions increase in length by a ratio of at least about 2.5:1 and narrow down substantially. The ends of the junctions are not stretched more than 100% more than the centres. At each junction there is a thicker, parallel-sided, long zone 17 which is oriented in the MD and has thinned down less than the mid-points of the MD strands 12 min so that there is continuous MD orientation running from end to end of the mesh structure. There are no dips in the junctions and the centres of the junctions are not substantially thinner than any other part of the junction on the MD centre line. There are biaxially-oriented zones 18 on either side of the thicker zones 17, and oriented crotches 16 connecting respective MD strands 12 min and TD strands 14 min , the biaxially-oriented zone 18 merging gradually with the crotches 16.