Powder application trial: Use of a powder applicator (consisting of a rotating gravure roll and a doctor blade on the bottom portion of a V-shaped storage bin) to deposit the granulated waste onto the back of polyester carpeting resulted in plugging up of the depressions in the gravure roll in a very short time and made it virtually impossible to apply the granulated waste as a backcoating onto a suitable carpeting substrate.
Size reduction of waste by flock cutting: In yet another attempt to modify the carpeting waste to enable application and fusion to form a carpet backcoating, the waste was passed through a flock cutter to reduce it to the smallest possible particle size.
Since there is increasing use of polypropylene carpeting containing polyethylene fiber as a binder instead of cross-linked polyvinyl acetate, it was decided to granulate and flock cut the former waste in a manner similar to that containing crosslinked polyvinyl acetate and compare the two in a backcoating application.
Melting and fusing trials using flock cut waste: This waste was hand-applied to the back of polyester carpeting and treated similarly to the flock cut waste containing crosslinked latex.
Since waste containing either crosslinked latex or polyethylene fiber did not melt and fuse properly when applied to the back of polyester carpeting, even when using flock cut instead of granulated waste, it was decided to develop a carpeting containing a non-crosslinked latex to overcome these problems.
Size reduction of waste by flock cutting: Since flock cutting appeared to reduce the waste to a much more suitable form and size than granulating, only flock cutting was performed on this type of carpeting.
Hot melt trials were run at an equipment supplier's site using carpeting trim waste containing crosslinked polyvinyl acetate copolymer latex run through a granulator.
Based on the results of these trials, the hot melt process was abandoned as a viable solution to recycling polypropylene carpeting waste containing crosslinked latex and using it as a thermoformable backcoating.
Initial planning for this type of processing, based on discussions with fiber manufacturers, plastic manufacturers and extrusion equipment suppliers, involved using two extruders in series to form and apply the molten polypropylene waste as a backcoating on polyester carpeting.
It also appeared that feeding carpeting waste, as is, instead of in granulated form, might provide a sufficiently constant feed to the extruder so that only one extruder, the film extrusion one, would need to be used to melt, then back-coat, the waste.
Trial a - Slot extrusion trial using polypropylene waste containing polyethylene fiber binder: This trial consisted of melting carpeting waste as is without granulation and extruding it through a slot-extrusion die into a backcoating film using only one extruder.
Based on our initial extrusion trial with the extruder containing a filament extrusion head, the carpeting waste used in this trial was cut into 1 1/2" wide strips and fed by hand directly into the extruder.
The extruded film was effectively laminated to the back of the polyester carpeting without undue penetration into the carpeting surface.
The extruded film in this trial was a bit grainier in texture than the one formed from waste containing polyethylene fiber, but it still extruded with no problem and the film was flexible and laminated well to the polyester carpeting without disturbing the pile surface.
The film extruded in this trial was the grainiest of the three, but the waste still extruded with no difficulty and formed a flexible film that laminated well to the polyester carpeting without distorting or harming the pile surface.