Abstract: In order to provide wider biaxially-stretched geogrids having high primary direction (PD) strength, crotch-forming zones of a starting material which is at least 2.0 mm thick have protuberances (6). On strectching, PD orientation passes right through the junction (27) but the protuberance (6) causes the orientation ratio of the crotch edge to decrease significiantly as orientation enters the central part of the crotch edge. After a secondary direction stretch of at least about 1.5:1, the thickness of the central part of the crotch edge is not reduced by more than about 20%. The stretching does not reduce the thickness of any point along notional ridge lines (31) to such an extent that the ratio of finished thickness to starting thickness at that point mid-point. In the biax geogrid (25), the junction mid-point is significantly thicker than the PD is less than about 80% of the ratio of finished thickness to starting thickness of the junction strand mid-point.

Abstract: To apply hot grit particles to a continuous thermoplastic web such as a geonet, the web is brought to the upper part of the surface of a roller which is rotating in a container containing grit particles. A controlled layer of grit particles is carried up over the upper part of the roller, and the particles are heated by halogen emitters and are pressed into the web, causing local melting of the web so that the grit particles are embedded and firmly retained. Grit particles are added to a hopper and the top surface of the mass of grit particles adjacent the ascending part of the roller surface is kept at a controlled level below the uppermost part of the roller. Surplus grit particles not taken up by the web are recirculated by interaction with the roller surface.

Abstract: In order to provide a good traction surface for vehicles and a good non-slip surface for pedestrians, a temporary vehicle-bearing surface is formed by laying directly on a grassed soil surface a heavy duty plastics geonet with a gritted upper face, and securing the geonet to the soil beneath with hooked pegs. Grass can than grow through meshes in the geonet and can be mown and fertilised.

Abstract: To form a paved surface, a laminate is used which has on the bottom a geotextile fabric with the mesh structure on the top. The fabric is adhered to the road base by spraying or spreading a bituminous liquid onto the base and laying on the laminate and applying further adhesive to the top of the laminate; asphalt is then placed and rolled. The laminate is formed of a square or rectangular mesh structure which has oriented stands connected at junctions which are thicker than the strands and have low-orientated or unorientated nodules. On one side the surface of the nodules are melted and the fabric is pressed into the nodules so that the plastics material of the nodules envelopes some of the fibers or filaments of the fabric to form a mechanical bond. In this way, the oriented strands stand proud of the fabric, to enable the asphalt aggregate to penetrate into the meshes and interlock with the strands.

Abstract: A starting material is provided having a rectangular grid of holes and the starting material is stretched in the MD to such an extent that the junctions are not significantly oriented, is stretched in the TD to such an extent that the junctions are not significantly oriented, and is finally stretched in the MD 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, 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.

Abstract: A starting material is stretched longitudinally to produce a geogrid. The starting material has pronounced ribs on each face, merging into sloping sides. Between the ribs, there are holes on a square grid. The mean thickness of the longitudinal elements is substantially greater than the mean thickness of the interconnecting elements, and the cross-sectional area of the longitudinal elements is at least 2.5 times the transverse cross-sectional area of the interconnecting elements. The longitudinal elements are stretched out into continuous oriented strands. The centers of the junctions reduce in thickness by at least 10% but substantially less than the percentage reduction at the thinnest part of the strand.

Abstract: To form a paved surface, a laminate is used which has on the bottom a geotextile fabric with the mesh structure on the top. The fabric is adhered to the road base by spraying or spreading a bituminous liquid onto the base and laying on the laminate and applying further adhesive to the top of the laminate; asphalt is then placed and rolled. The laminate is formed of a square or rectangular mesh structure which has oriented stands connected at junctions which are thicker than the strands and have low-orientated or unorientated nodules. On one side the surface of the nodules are melted and the fabric is pressed into the nodules so that the plastics material of the nodules envelopes some of the fibres or filaments of the fabric to form a mechanical bond. In this way, the oriented strands stand proud of the fabric, to enable the asphalt aggregate to penetrate into the meshes and interlock with the strands.

Abstract: It is highly desirable to reinforce the grassed surface layer of a sports ground in order to reduce damage to the surface, e.g. from horse racing or from playing football. In order to provide a good surface layer, a biaxially-orientated, integrally-extruded plastics material mesh structure layer is laid on a base of sand strengthened with small, flexible, randomly-placed, plastics material mesh pieces. A top dressing is put on top of the mesh structure layer, grass is seeded or planted, and a machine is then used after the grass has grown to slit the mesh structure layer into pieces 1 which may be e.g. 100.times.100 mm or 150.times.150 mm, each having a number of complete mesh openings. If a piece is caught by a horse's hoof or by an footballer's stud, it may be ripped out, but the whole mesh layer is not ripped out.

Abstract: A drainage system having an at least 2.5 mm thick bi-planar mesh structure drainage core and a filter material against one face and a filter material or impervious member against the other face. The drainage core has generally parallel main strands interconnected by generally parallel subsidiary strands. The main strands are at least twice as tall as the subsidiary strands. The outer faces of the subsidiary strands are coplanar with, and form, one face of the drainage core. The ratio of the free cross-sectional area of each main flow channel to the free cross-sectional area of each subsidiary flow channel, if any, is at least 2.5:1. The drainage core can resist pressures of at least 400 kPa, exhibits a flow fall-off of not more than 20% under an external pressure normal to the faces of 400 kPa.

Abstract: A planar, biaxially heat-shrinkable, plastics mesh layer is fixed to a planar, relatively non-heat-shrinkable plastics mesh layer at zones which are spaced apart on a generally square grid, and the structure so formed is heated to cause the shrink layer to shrink biaxially and thereby cause the non-shrink layer to assume a cuspated configuration. The structure can be shipped as a semi-finished product after fixing the layers together and before heating, thereby reducing bulk and hence shipping costs.

Abstract: A unitary tubular product having an inner layer and an outer layer connected together by a bi-planar mesh formed of helical ribs bonded at their cross-over points is produced in a single coaxial tubular extrusion process, the structure being integrally or confluently extruded. The extruder die head has annular flow channels having closely-spaced die grooves.

Abstract: An apparatus is afforded for transversely stretching a continuously advancing flexible web between a pair of opposed banks of tranversely-spaced pressure elements, one of which banks is stationary and whose elements have slide surfaces, the margins of the web being restrained to prevent substantial inward movement of said margins.

Abstract: A tubular net has unorientated annular zones, and orientated annular zones which contract transversely upon heat shrinking; the net can be used for packaging or sleeving, the unorientated zones acting as end closures or neck holders and the ends of the orientated zones being heat shrunk to retain the other end of the article or articles being packaged or sleeved.

Abstract: Process and apparatus for treating tubular, plastics material net comprising transversely opening out a rope-oriented net, transversely corrugating the transversely opened-out net, and heat setting the net in its transversely opened-out and corrugated state. In addition, the product thereof, having a length less than 1/350th of the maximum axially-extended length of the net.

Abstract: An extruded plastics mesh having two sets of oblique strands lying in adjacent planes and joined together at their crossing points by tenacious intersections is suitably stretched to form a structure having mesh openings each of which is a six-sided figure bounded on four sides by portions of four separate strands and on the other two sides by strandlike members comprising stretched intersections of the original mesh. To inhibit splitting of the structure along the length of the stretched intersections there is provided at opposite ends of each such intersection a relaxed web integral with the structure and extending across the crotch defined by the two strands which form the intersection.

Abstract: An extruded plastic mesh of the type indicated having mesh openings each of which is a six-sided figure bounded on four sides by portions of four separate strands and on oppositely disposed two sides by elongate members comprising confluent portions of pairs of said four strands and forming a crotch at each end of each elongate member, wherein all of said strands and elongate members have preferred molecular orientation of the plastic material thereof in the direction of their major dimension and passing through and around the crotches of the elongate members of adjacent mesh openings and wherein the length of each elongate member measured from crotch to crotch is at least twice the diameter of a notional circle having the same area as the cross section of the elongate member at about its mid-point.