ELECTROSTATIC DISSIPATIVE FLUOROPOLYMER COMPOSITES AND ARTICLES FORMED THEREFROM
20200103056 ยท 2020-04-02
Inventors
- John P. Puglia (Townsend, MA, US)
- William J. Shaner (Colorado Springs, CO, US)
- Brett C. Reichow (Chanhassen, MN, US)
Cpc classification
B32B27/322
PERFORMING OPERATIONS; TRANSPORTING
B32B1/00
PERFORMING OPERATIONS; TRANSPORTING
B32B2597/00
PERFORMING OPERATIONS; TRANSPORTING
B32B27/18
PERFORMING OPERATIONS; TRANSPORTING
B32B2264/108
PERFORMING OPERATIONS; TRANSPORTING
F16L9/133
MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
B32B2250/242
PERFORMING OPERATIONS; TRANSPORTING
F16L11/127
MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
C08L27/18
CHEMISTRY; METALLURGY
C08L2205/025
CHEMISTRY; METALLURGY
F16L9/125
MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
B32B2581/00
PERFORMING OPERATIONS; TRANSPORTING
International classification
F16L9/12
MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
Abstract
Articles, such as various operative components of a fluid delivery and storage system, incorporating a composite including a fluoropolymer matrix having regions of perfluorinated distributed within the matrix into their construction. The tubing and various operative components incorporating the composite are electrostatic dissipative in nature having a surface resistivity ranging from between 110.sup.4 ohms/square and 110.sup.12 ohms/square.
Claims
1. A tubing segment comprising: a tubing body defining a fluid flow path from a first end of the tubing body to the second end of the tubing body, wherein the tubing body includes a first portion including a non-conductive fluoropolymer and a second portion, in contact with the first portion, the second portion formed from a composite including a fluoropolymer matrix having regions of perfluorinated ionomer distributed throughout the fluoropolymer matrix, wherein the tubing body has a surface resistivity of between 110.sup.4 ohms/square and 110.sup.12 ohms/square.
2. The tubing segment according to claim 1, wherein an amount of perfluorinated ionomer in the composite ranges from 0.01 wt. % to 5 wt. % of the total weight of the composite.
3. The tubing segment according to claim 1, wherein the fluoropolymer is perfluoroalkoxy alkane polymer and the perfluorinated ionomer comprises a perfluorinated sulfonic acid copolymer.
4. The tubing segment according to claim 3, wherein the perfluorinated sulfonic acid copolymer is in acidic form.
5. The tubing segment according to claim 1, wherein the first portion is an outer layer and defines an outer surface of the tubing body and the second portion is an inner layer and defines an inner surface of the tubing body that comes into contact with a fluid flowing through the fluid flow path.
6. The tubing segment according to claim 1, wherein the first portion is an inner layer defining an inner surface of the tubing body that comes into contact with a fluid flowing through the fluid flow path and the second portion is an outer layer defining an outer surface of the tubing body, wherein the second layer is disposed over and is in contact with the first layer.
7. The tubing segment according to claim 1, wherein the first portion is an outer layer of the tubing body disposed over and in contact with the second portion forming an inner layer of the tubing body defining an inner surface of the tubing body that comes into contact with a fluid flowing through the fluid path, wherein the first layer includes a one or more conductive stripes extending axially within the first layer in a direction from the first end to the second end of the tubular body.
8. The tubing segment according to claim 1, wherein the second portion comprises one or more stripes of the composite extending within in the first portion in an axial direction along the length of the tubing body.
9. The tubing segment according to claim 8, wherein the one or more stripes having a thickness extending from an outer surface to an inner surface of the tubing body.
10. A tubing segment comprising: a tubing body defining a fluid flow path from a first end to a second end of the tubing body, the tubing body constructed entirely from a composite including a fluoropolymer matrix having regions of perfluorinated ionomer distributed throughout the fluoropolymer matrix such that the operative component is electrostatic dissipative and has a surface resistivity of between 110.sup.4 ohms/square and 110.sup.12 ohms/square.
11. An operative component comprising: at least a portion formed from a composite including a fluoropolymer matrix having regions of perfluorinated ionomer distributed throughout the fluoropolymer matrix such that the operative component is electrostatic dissipative and has a surface resistivity of between 110.sup.4 ohms/square and 110.sup.12 ohms/square.
12. The operative component according to claim 11, wherein the operative component is any one of a fitting body, valve body, filter housing, heat exchanger housing, sensor housing, pump body, valve diaphragm, break seal, dispense head, spray nozzle, mixer, container, container liner, or storage drum.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] The disclosure may be more completely understood in consideration of the following description of various illustrative embodiments in connection with the accompanying drawings
[0013]
[0014]
[0015]
[0016]
[0017]
[0018]
[0019] While the disclosure is amenable to various modifications and alternative forms, specifics thereof have been shown by way of example in the drawings and will be described in detail. It should be understood, however, that the intention is not to limit aspects of the disclosure to the particular illustrative embodiments described. On the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the disclosure.
DETAILED DESCRIPTION
[0020] The following detailed description should be read with reference to the drawings in which similar elements in different drawings are numbered the same. The detailed description and the drawings, which are not necessarily to scale, depict illustrative embodiments and are not intended to limit the scope of the invention. The illustrative embodiments depicted are intended only as exemplary. Selected features of any illustrative embodiment may be incorporated into an additional embodiment unless clearly stated to the contrary.
[0021] According to various embodiments, perfluorinated ionomer particles are blended with a non-conductive fluoropolymer to form a composite including a non-conductive fluoropolymer matrix and regions of perfluorinated ionomer distributed within the non-conductive fluoropolymer matrix. The regions of perfluorinated ionomer within the non-conductive fluoropolymer matrix imparts electrostatic dissipative properties to the resultant composite. An electrostatic dissipative material is a material having a surface resistivity equal to or greater than 110.sup.4 ohms/square but less than 110.sup.12 ohms/square or a volume resistivity equal to or granter than 110.sup.4 ohms-cm.sup.2 but less than 110.sup.11 ohms-cm.sup.2. Electrostatic dissipative materials are classified as antistatic which is used to describe materials that prevent the buildup of static electricity, which is undesirable in fluid delivery and storage systems used in the semiconductor manufacturing industry.
[0022] Exemplary non-conductive fluoropolymers used to form the electrostatic dissipative composite according to the various embodiments can include, but are not limited to, fluoropolymers such as: perfluoroalkoxy alkane polymer (PFA); ethylene and tetrafluoroethylene polymer (ETFE); ethylene, tetrafluoroethylene and hexafluoropropylene polymer (EFEP); and fluorinated ethylene propylene polymer (FEP), all of which are melt-processable. In addition to providing a non-corrosive and inert construction, many fluoropolymers, such as PFA, are injection moldable and extrudable. In one embodiment, the non-conductive fluoropolymer is perfluoroalkoxy alkane polymer (PFA). In other embodiments, the non-conductive fluoropolymer can be polytetrafluoroethylene (PTFE) or tetrafluoroethylene polymer (PTFE) or modified tetrafluoroethylene polymer (TFM), which are not melt-processable, but can be compression molded.
[0023] The perfluorinated ionomer particles are blended with the non-conductive fluoropolymer, such as PFA, in an amount effective to impart electrostatic dissipative properties to the composite. Generally, a perfluorinated ionomer is an ionomer that includes a tetrafluoroethylene backbone and a vinyl ether side-chain terminating in an ion-exchange group. The ion-exchange group can be a sulfonic acid group (sulfonate) or a carboxylic acid group (carboxylate). In some cases, the perfluorinated ionomer can include a mixture of sulfonic acid groups and carboxylic acid groups. Due to the presence of the ion-exchange groups, the perfluorinated ionomer is capable of conducting protons and therefore has proton conductivity. However, the perfluorinated ionomer does not conduct anions or electrons.
[0024] According to various embodiments, the perfluorinated ionomer can be a perfluorinated sulfonic acid copolymer. An exemplary perfluorinated sulfonic acid copolymer suitable for use in the electrostatic dissipative composite is a perfluorosulfonic acid (PFSA) polymer having a poly(tetrafluoroethylene) backbone with perfluoroether pendant side chains terminated by sulfonic acid groups. An example of one such perfluorosulfonic acid (PFSA) polymer having a poly(tetrafluoroethylene) backbone with perfluoroether pendant side chains terminated by sulfonic acid groups is NAFION. NAFION is a trademark of The Chemours Company. Additional examples of a perfluorosulfonic acid (PFSA) polymer having a poly(tetrafluoroethylene) backbone with perfluoroether pendant side chains terminated by sulfonic acid groups include FLEMION (Asahi Glass Company), ACIPLEX (Asahi Kasei), and FUMION F. (FuMA-Tech).
[0025] In one embodiment, the perfluorinated ionomer particles are particles of a perfluorinated sulfonic acid copolymer in its acid (H+) form. NAFION particles are one example of particles of a perfluorinated sulfonic acid copolymer in acidic form that can be used to form the electrostatic dissipative composite, as described herein. The perfluorinated sulfonic acid copolymer particles are provided as beads having an average bead size ranging from: 100 nanometers to 1000 nanometers; from 100 nanometers to 500 nanometers; or from 100 nanometers to 200 nanometers. In one embodiment, the perfluorinated sulfonic acid copolymer particles have an average bead size of about 200 nanometers. In some cases, the perfluorinated ionomer particles are available as a suspension in a solvent. In other cases, the perfluorinated ionomer particles are available as dry resin beads.
[0026] The perfluorinated sulfonic acid copolymer particles are dispersed within the non-conductive fluoropolymer in an effective amount such that the surface resistivity of the resultant composite ranges from greater than 110.sup.4 ohms/square and less than 110.sup.12 ohms/square and more particularly, ranges from 110.sup.5 ohms/square to 110.sup.8 ohms/square. The composite is formed into sheets and surface resistivity measured according to ASTM F1711. In some embodiments, to form the composite, the perfluorinated sulfonic acid copolymer particles are first contacted with a strong base such as ammonium hydroxide or sodium hydroxide to convert the particles from an acid (H+) form of the copolymer to a neutralized or non-ionic form of the copolymer to aid in blending the perfluorinated sulfonic acid copolymer particles with the non-conductive fluoropolymer to form a composite including regions of perfluorinated sulfonic acid copolymer distributed within the non-conductive fluoropolymer matrix. The perfluorinated sulfonic acid copolymer can be converted back to its acidic form after blending by contacting the blended material with a strong acid such as, for example, hydrochloric acid. In one embodiment, an amount of the perfluorinated sulfonic acid copolymer in the composite ranges from 0.01 wt. % to 10 wt. % of the total weight of the composite. In another embodiment, an amount of the perfluorinated sulfonic acid copolymer in the composite ranges from 0.01 wt. % to 5 wt. % of the total weight of the composite. In yet another embodiment, an amount of the perfluorinated sulfonic acid copolymer ranges from 1 wt. % to 5 wt. % of the total weight of the composite. In still another embodiment an amount of the perfluorinated sulfonic acid copolymer ranges from 2 wt. % to 5 wt. % of the total weight of the composite. In some embodiments, the perfluorinated sulfonic acid copolymer is in acid form in the final composite.
[0027] In one non-limiting example, an electrostatic dissipative composite includes PFA having regions of NAFION in acidic form in an amount ranging from 0.01 wt. % to 5 wt. %, the composite having a surface resistivity of between 110.sup.4 ohms/square and 110.sup.12 ohms/square. In another non-limiting example, an electrostatic dissipative composite includes PFA having regions NAFION in acidic form in an amount ranging from 2 wt. % to 5 wt. %, the composite having a surface resistivity of between 110.sup.5 ohms/square and 110.sup.8 ohms/square. The composites are formed into sheets and the surface resistivity of the material is measured according to ASTM F1711.
[0028]
[0029] In some embodiments, a tubing segment includes an electrostatic dissipative composite, as described herein, such that the tubing segment is electrostatic dissipative having a surface resistivity of between 110.sup.4 ohms/square and 110.sup.12 ohms/square or more particularly of between 110.sup.5 ohms/square and 110.sup.8 ohms/square. Incorporation of the electrostatic dissipative material into the tubing segment can reduce the build-up of static charges on the outer surface of the tubing segment as a result of a fluid flowing through the tubing segment. In addition, to the extent that static charges have accumulated on the outer surface of the tubing segment, incorporation of the electrostatic dissipative composite into the tubing segment causes the build-up charges on the outer surface of the tubing segment to more slowly flow to ground. Both the reduction in the accumulation of static charge and the slow transfer of charge to ground may prevent an electrostatic discharge event in a fluid delivery and storage system.
[0030]
[0031] The electrostatic dissipative composite used to construct the tubing body 22 includes a PFA matrix having regions of perfluorinated sulfonic acid copolymer distributed throughout the matrix such that the composite has a surface resistivity of between 110.sup.4 ohms/square and 110.sup.12 ohms/square. In one embodiment, the perfluorinated sulfonic acid copolymer is NAFION. The perfluorinated sulfonic acid copolymer can be in acidic form in the final product. The amount of perfluorinated sulfonic acid copolymer in the electrostatic dissipative composite used to form the inner layer 38 can range from: 0.01 wt. % to 10 wt. % of the total weight of the composite; from 0.01 wt. % to 5 wt. % of the total weight of the composite; from 1 wt. % to 5 wt. % of the total weight of the composite; or more particularly, from 2 wt. % to 5 wt. % of the total weight of the composite. The tubing body 22 can have a surface resistivity of between 110.sup.4 ohms/square and 110.sup.12 ohms/square or more particularly, of between 110.sup.5 ohms/square and 110.sup.8 ohms/square. Surface resistivity of the tubing body 36 can be measured according to ASTM F1711.
[0032]
[0033] In some embodiments, the first portion forming the outer layer 34 of the tubing body is formed from a non-conductive fluoropolymer. Suitable non-conductive fluoropolymers used to form the outer layer include, but are not limited to, fluoropolymers such as: perfluoroalkoxy alkane polymer (PFA); ethylene and tetrafluoroethylene polymer (ETFE); ethylene, tetrafluoroethylene and hexafluoropropylene polymer (EFEP); and fluorinated ethylene propylene polymer (FEP). In one embodiment, the first portion forming the outer layer 34 is formed from PFA.
[0034] The second portion forming the inner layer 38 defining an inner surface 42 of the tubing body 36 can be formed form an electrostatic dissipative composite including a non-conductive fluoropolymer matrix having regions of perfluorinated ionomer distributed throughout the matrix. In some embodiments, the electrostatic dissipative composite includes a PFA matrix having regions of perfluorinated sulfonic acid copolymer distributed throughout the matrix such that the composite has a surface resistivity of between 110.sup.4 ohms/square and 110.sup.12 ohms/square. In one embodiment, the perfluorinated sulfonic acid copolymer is NAFION. The perfluorinated sulfonic acid copolymer can be in acidic form in the final product. The amount of perfluorinated sulfonic acid copolymer in the electrostatic dissipative composite used to form the inner layer 38 can range from: 0.01 wt. % to 10 wt. % of the total weight of the composite; from 0.01 wt. % to 5 wt. % of the total weight of the composite; from 1 wt. % to 5 wt. % of the total weight of the composite; or more particularly, from 2 wt. % to 5 wt. % of the total weight of the composite. The tubing body 36 can have a surface resistivity of between 110.sup.4 ohms/square and 110.sup.12 ohms/square or more particularly, of between 110.sup.5 ohms/square and 110.sup.8 ohms/square. Surface resistivity of the tubing body 36 can be measured according to ASTM F1711.
[0035] In one embodiment, the outer layer 34 can be co-extruded with the inner layer 38 to form the tubing body 36. In another embodiment, the inner layer 38 can be formed first by extrusion. The outer layer 34 can then be extruded over the inner layer 38 to form the tubing body 36.
[0036]
[0037] The first portion forming the outer layer 44 of the tubing body 46 can be formed form an electrostatic dissipative composite including a fluoropolymer blended with perfluorinated ionomer particles, as described herein. In some embodiments, the electrostatic dissipative composite includes a PFA matrix having regions of perfluorinated sulfonic acid copolymer distributed throughout the matrix such that the composite has a surface resistivity of between 110.sup.4 ohms/square and 110.sup.12 ohms/square. In one embodiment, the perfluorinated sulfonic acid copolymer is NAFION. The perfluorinated sulfonic acid copolymer can be in acidic form in the final product. The amount of perfluorinated sulfonic acid copolymer in the electrostatic dissipative composite used to form the outer layer 44 can range from: 0.01 wt. % to 10 wt. % of the total weight of the composite; from 0.01 wt. % to 5 wt. % of the total weight of the composite; from 1 wt. % to 5 wt. % of the total weight of the composite; or more particularly, from 2 wt. % to 5 wt. % of the total weight of the composite. The tubing body 46 can have a surface resistivity of between 110.sup.4 ohms/square and 110.sup.12 ohms/square or more particularly, of between 110.sup.5 ohms/square and 110.sup.8 ohms/square. Surface resistivity of the tubing body 46 is measured according to ASTM F1711.
[0038] The second portion forming the inner layer 48 of the tubing body 46 can be formed from a non-conductive fluoropolymer. Suitable non-conductive fluoropolymers used to form the inner layer include, but are not limited to, fluoropolymers such as: perfluoroalkoxy alkane polymer (PFA); ethylene and tetrafluoroethylene polymer (ETFE); ethylene, tetrafluoroethylene and hexafluoropropylene polymer (EFEP); and fluorinated ethylene propylene polymer (FEP). In one embodiment, the second portion forming the inner layer 48 is formed from PFA.
[0039] In one embodiment, the outer layer 44 can be co-extruded with the inner layer 48 to form the tubing body 46. In another embodiment, the inner layer 48 can be formed first by extrusion. The outer layer 44 can then be extruded over the inner layer 48 to form the tubing body 46.
[0040]
[0041] In other embodiments, as depicted in
[0042] The second portion forming the inner layer 106 of the tubing body 104 shown in
[0043] In addition to imparting electrostatic dissipative properties to the tubing body 104, the presence of the inner layer 106 formed from the electrostatic dissipative composite may also provide a more inert inner surface 112 for contact with a fluid flowing through a fluid flow path 114 defined in the tubing body 104, and may also prevent contaminants from the conductive stripes 110 being introduced into the fluid.
[0044]
[0045] The first portion 204 of the tubing body 202 can be formed from a non-conductive fluoropolymer. Suitable non-conductive fluoropolymers used to form the outer layer include, but are not limited to, fluoropolymers such as: perfluoroalkoxy alkane polymer (PFA); ethylene and tetrafluoroethylene polymer (ETFE); and ethylene, tetrafluoroethylene and hexafluoropropylene polymer (EFEP); and fluorinated ethylene propylene polymer (FEP). In one embodiment, the first portion 204 is formed from PFA.
[0046] The second portion 206 of the tubing body 202 can be formed form an electrostatic dissipative composite including a fluoropolymer blended with perfluorinated ionomer particles, as described herein. In some embodiments, the electrostatic dissipative composite includes a PFA matrix having regions of perfluorinated sulfonic acid copolymer distributed throughout the matrix such that the composite has a surface resistivity of between 110.sup.4 ohms/square and 110.sup.12 ohms/square. In one embodiment, the perfluorinated sulfonic acid copolymer is NAFION. The perfluorinated sulfonic acid copolymer can be in acidic form in the final product. The amount of perfluorinated sulfonic acid copolymer in the electrostatic dissipative composite used to form the inner layer 38 can range from: 0.01 wt. % to 10 wt. % of the total weight of the composite; from 0.01 wt. % to 5 wt. % of the total weight of the composite; from 1 wt. % to 5 wt. % of the total weight of the composite; or more particularly, from 2 wt. % to 5 wt. % of the total weight of the composite. The tubing body 202 can have a surface resistivity of between 110.sup.4 ohms/square and 110.sup.12 ohms/square or more particularly, of between 110.sup.5 ohms/square and 110.sup.8 ohms/square. Surface resistivity of the tubing body is measured according to ASTM F1711.
[0047]
[0048] The first portion 304 of the tubing body 302 can be formed from a non-conductive fluoropolymer. Suitable non-conductive fluoropolymers used to form the outer layer include, but are not limited to, fluoropolymers such as: perfluoroalkoxy alkane polymer (PFA); ethylene and tetrafluoroethylene polymer (ETFE); ethylene, tetrafluoroethylene and hexafluoropropylene polymer (EFEP); and fluorinated ethylene propylene polymer (FEP). In one embodiment, the first portion 304 is formed from PFA.
[0049] The stripes 308 forming the second portion 306 of the tubing body 302 can be formed form an electrostatic dissipative composite including a fluoropolymer blended with perfluorinated ionomer particles, as described herein. The fluoropolymer used to form the composite can be the same fluoropolymer used to form the first portion 304 of the tubing body 302, but this is not required. In some embodiments, the electrostatic dissipative composite includes a PFA matrix having regions of perfluorinated sulfonic acid copolymer distributed throughout the matrix such that the composite has a surface resistivity of between 110.sup.4 ohms/square and 110.sup.12 ohms/square. In one embodiment, the perfluorinated sulfonic acid copolymer is NAFION. The perfluorinated sulfonic acid copolymer can be in acidic form in the final product. The amount of perfluorinated sulfonic acid copolymer in the electrostatic dissipative composite used to form the inner layer 38 can range from: 0.01 wt. % to 10 wt. % of the total weight of the composite; from 0.01 wt. % to 5 wt. % of the total weight of the composite; from 1 wt. % to 5 wt. % of the total weight of the composite; or more particularly, from 2 wt. % to 5 wt. % of the total weight of the composite. The tubing body 302 can have a surface resistivity of between 110.sup.4 ohms/square and 110.sup.12 ohms/square or more particularly, of between 110.sup.5 ohms/square and 110.sup.8 ohms/square. Surface resistivity of the tubing body is measured according to ASTM F1711.
[0050] In addition to tubing segments, at least a portion of various other operative components of a fluid delivery and storage system can be formed from an electrostatic dissipative composite, as disclosed herein according to the various embodiments. The term operative component as used herein in this disclosure refers to any component or device having a fluid input and a fluid output and that connect with tubing segments for directing or providing for the flow of fluid. The term operative component also includes operative parts of a component that are exposed to or in contact with a fluid such as, for example, a valve, pump diaphragm or a break seal. Examples of operative components include, but are not limited to, fitting bodies, valve bodies, valve diaphragms, filter housings, heat exchanger housing, sensor housings, pump bodies, diaphragms, break seals, dispense heads, spray nozzles, mixers, containers, container liners, storage drums, and/or the like. In one embodiment, the operative component is a valve body or a pump body. In another embodiment, the operative component is a valve diaphragm or a pump diaphragm. In some cases, at least a portion, if not all, of the operative component can be compression molded from the composite.
[0051]
[0052] In various embodiments, connector fittings 326 and 327 have substantially the same design. As described above, in various embodiments the body portion 322, 330 is constructed using an electrostatic dissipative composite as described herein. For example, at least a portion of the body portion 322 or 330 can be constructed from an electrostatic dissipative composite including a PFA matrix having regions of blended perfluorinated sulfonic acid copolymer distributed throughout the matrix. In one embodiment, the perfluorinated sulfonic acid copolymer is NAFION. The perfluorinated sulfonic acid copolymer can be in acidic form in the final product. The amount of perfluorinated sulfonic acid copolymer in the electrostatic dissipative composite used to form at least a portion of the body portion 322 or 330 can range from: 0.01 wt. % to 10 wt. % of the total weight of the composite; from 0.01 wt. % to 5 wt. % of the total weight of the composite; from 1 wt. % to 5 wt. % of the total weight of the composite; or more particularly, from 2 wt. % to 5 wt. % of the total weight of the composite. The operative component formed from the composite can have a surface resistivity of between 110.sup.4 ohms/square and 110.sup.12 ohms/square or more particularly, of between 110.sup.5 ohms/square and 110.sup.8 ohms/square. Surface resistivity is measured according to ASTM F1711.
[0053]
[0054] Having thus described several illustrative embodiments of the present disclosure, those of skill in the art will readily appreciate that yet other embodiments may be made and used within the scope of the claims hereto attached. Numerous advantages of the disclosure covered by this document have been set forth in the foregoing description. It will be understood, however, that this disclosure is, in many respects, only illustrative. Changes may be made in the details, particularly in matters of shape, size, and arrangement of parts without exceeding the scope of the disclosure. The disclosure's scope is, of course, defined in the language in which the appended claims are expressed.