Die design for property enhancement
Provided are extrusion dies having entrance, orientation, merging ( 205 ), and exit ( 211 ) sections, which dies may be used to produce fibers having, e.g., oriented reinforcement materials (e.g., PTFE) dispersed within. The dies provide fibers having enhanced mechanical and processing properties. The orientation section comprises orientation channels ( 203 ) wherein a ratio of a cross-sectional area having of the channel inlet to a cross-sectional area of the channel outlet is between 2 and 45.
1. A die, comprising:
an entrance section comprising at least one inlet;
the inlet being in fluid communication with an orientation section of the die, the orientation section comprising a plurality of orientation channels having a channel inlet and a channel outlet;
a merging region, the merging region defining a receiving volume in fluid communication with the outlets of the plurality of orientation channels of the orientation section, the merging region being configured to merge together at least some fluid flows originating from the outlets of the orientation channels of the orientation section; and
an exit region in fluid communication with the merging region, the exit region comprising at least one outlet,
wherein at least some of the plurality of orientation channels include a hyperbolic-shaped region followed immediately by a linearly tapered region,
wherein the hyperbolic-shaped region has an angle of curvature at its entrance of from 120 to 150 degrees, where the angle of curvature is the angle between a horizontal axis and a line tangent to the hyperbola at the entrance, and
wherein each of the plurality of orientation channels, during operation, impose a Hencky strain of from about 2 to about 8 units over the length of the channel.
2. The die of claim 1 , wherein at least some of the plurality of orientation channels independently have a length in a range of from about 4 millimeters (mm) to about 50 mm.
3. The die of claim 1 , wherein at least two of the orientation channels converge.
4. The die of claim 1 , wherein the outlets of the plurality of orientation channels are regularly spaced about one another at the merging region.
5. The die of claim 1 , wherein at least two of the orientation channels do not converge.
6. The die of claim 1 , wherein at least some of the orientation channels are arranged in a skew symmetric pattern.
7. The die of claim 1 , wherein the merging region defines an at least partially spherical receiving volume or an at least partially polygonal receiving volume.
8. The die of claim 1 , wherein the merging region is shaped so as to orient reinforcement agents in a flow direction originating from the orientation section into the merging region along the flow direction and in a direction transverse to the flow direction.
9. The die of claim 1 , wherein the receiving volume defines a cross-sectional dimension that varies in the direction of the exit region.
10. The die of claim 1 , wherein the outlet of the exit region defines a rectangular cross-section, an at least partially circular cross-section, or a polygonal cross-section.
11. The die of claim 1 , wherein the entrance of the hyperbolic-shaped region has a hyperbolic curvature over about 1 to about 95% of the length of the orientation channel.
12. A method of fiber manufacture, comprising:
communicating a molten feed composition comprising a thermoplastic matrix polymer through a die of claim 1 so as to give rise to a product.
13. The method of claim 12 , wherein the molten feed composition further comprises a reinforcement material.
14. The method of claim 13 , wherein the reinforcement material is present at from about 0.01 wt % to about 15 wt % as measured against the unit weight of the molten feed composition.
15. The method of claim 12 , wherein a plurality of the dies or the plurality of orientation channels are arranged in a die holder.
16. The method of claim 15 , wherein the die holder is arranged at a distal end of an extruder.