Manufacturing Nonwoven Needlepunched Geotextiles with Opening Size Larger Than 0.2 mm

The maximum apparent opening size (AOS) for a nonwoven needlepunched geotextile is limited to approximately 0.2 mm. While adequate for most designs, a larger opening size may be desirable for certain geotextile applications. A series of manufacturing trials were conducted to assess the feasibility of increasing the opening size of nonwoven needlepunched geotextiles. These trials can be broadly grouped into two categories: i) fiber denier trials, and ii) post-finish perforation trials. The first type of trial entailed increasing the geotextile fiber denier to fifteen from the current maximum of eight. The geotextile AOS increased as a result, while mechanical properties decreased. In the second group of trials, a calendared nonwoven needlepunched (NW-NP) geotextile was perforated using two different processes. In the first case, a laboratory scale needle loom was used to needlepunch the geotextile. Both standard (barbed) as well as barbless needles were used in the trials. It was observed that fibers tended to shift with time and block the openings soon after the needling process. As a result, AOS tests showed little or no improvement. In the second method, needles manufactured specially for these trials were mounted over a rotating drum where they were continuously heated using a gas flame. The drum was then manually rotated against the geotextile, thus penetrating the hot needles through the geotextile. Perforations on the order of 0.5 mm were achieved with this method. Product development is ongoing as of the time of writing this paper.