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HQ 966642

July 9, 2004

CLA-2 RR:CR:TE 966642 GGD


TARIFF NO.: 3921.19.0000

Mary Wright, Esquire
Grunfeld, Desiderio, et al.
45 School Street
Boston, Massachusetts 02108

RE: Reconsideration of NY I84349; Filter Membrane Elements; Ruling Correct as to Merchandise Described; New Ruling Issued Concerning RO Filtration Membrane Material Imported in Rolls; Filmtec Corporation v. United States, Slip Op. 03-153, 293 F. Supp 2d 1364 (Ct. Intl. Trade 2003)

Dear Ms. Wright:

This letter is in response to your firm’s request dated July 9, 2003, on behalf of your client, Toray Membrane America, Inc., for “a binding ruling/clarification.” We consider the request to be one for reconsideration of New York Ruling Letter (NY) I84349, issued August 19, 2002, on behalf of your client, concerning the classification under the Harmonized Tariff Schedule of the United States Annotated (HTSUSA) of membrane elements used in water filtering machines made in Japan. No samples were submitted at the time of the original ruling, only product-related literature, a data sheet, and a cut away diagram displaying the make up and function of spiral wound reverse osmosis elements used in water filtration. Samples and additional information not previously available to the Bureau of Customs and Border Protection (CBP) were submitted with the current request.


Prior to the issuance of NY I84349, product information concerning membrane elements used in water filtering machines was submitted by a freight forwarding company on behalf of your client. The merchandise depicted was telephonically
discussed with that company and was believed to be spiral wound reverse osmosis elements used in water filtration. The filter material was concentrically wound around a flow tube layered with mesh spacers and fitted into a pressure housing. The elements were said to be ready-to-use cylinders of 40 inches in length, and either 4 or 8 inches in diameter (depending on the machine to which dedicated). One product, identified as the SU-Series, was said to be composed of a cross-linked “polyamide composite” on a nonwoven base, the thickness of the two layers measuring 0.2 (two tenths) of a micron and 60 microns, respectively. The other product, identified as the SC-Series, was said to be composed of an asymmetrical cellulose acetate membrane element on a nonwoven porous layer, the thickness of these layers being less than 1 micron and between 50 and 150 microns, respectively. No information had been furnished concerning interaction of the layers and, in the absence of information to the contrary, both components were considered to comprise each filter element. It was determined that the textile material provided important functions and that the filter elements were textile articles for technical use. The products were classified in subheading 5911.90.0080, HTSUSA, the provision for “Textile products and articles, for technical uses, specified in note 7 to this chapter: Other, Other,” with a general column one duty rate (in 2002) of 4.5 percent ad valorem.

In this request for reconsideration, you inform CBP that the actual merchandise imported consists only of a reverse osmosis filtration membrane, which is a three-layered material (known in the industry as a “fully aromatic polyamide thin film composite”) that is imported from Japan in roll form. Upon review of the record, and the information and sample currently available, we find that NY I84349 is correct based upon the product description and information previously provided to CBP. This letter, however, additionally provides a binding ruling as to the tariff classification of the filtration membrane in light of the newly submitted information and sample.

The three-layered material at issue is a filter membrane used in reverse osmosis (“RO”) water desalination. The top layer is composed of a semi-permeable polyamide (nylon) plastic film of approximately 0.2 (two tenths) of a micron in thickness (claimed to be a noncellular plastic); a second (or middle) layer composed of a cellular polysulfone plastic material which measures approximately 40 microns in thickness; and a third (or bottom) layer composed of a polyester nonwoven textile material which measures approximately 100 microns in thickness and provides support to the two layers of plastics. A micron is a unit of length equal to one millionth of a meter. For purposes of comparison, a human hair is said to measure approximately 50 microns in thickness.


Whether the three-layered, RO filtration membrane material is classified in subheading 3921.90, HTSUSA, the provision for “Other plates, sheets, film, foil and strip, of plastics: Other [than cellular];” or in subheading 3921.19, HTSUSA, the provision for “Other plates, sheets, film, foil and strip, of plastics: Cellular.”


Classification under the HTSUSA is made in accordance with the General Rules of Interpretation (GRI). GRI 1 provides that the classification of goods shall be determined according to the terms of the headings of the tariff schedule and any relative Section or Chapter Notes. In the event that the goods cannot be classified solely on the basis of GRI 1, and if the headings and legal notes do not otherwise require, the remaining GRI may then be applied. The Explanatory Notes (EN) to the Harmonized Commodity Description and Coding System, which represent the official interpretation of the tariff at the international level, facilitate classification under the HTSUSA by offering guidance in understanding the scope of the headings and GRI.

Chapter 39, HTSUSA, covers plastics and articles thereof. The EN to chapter 39 state that (except for certain wall or ceiling coverings) “the classification of plastics and textile combinations is essentially governed by Note 1(h) to Section XI, Note 3 to Chapter 56 and Note 2 to Chapter 59.” Among other goods, chapter 59, HTSUSA, covers impregnated, coated, covered or laminated textile fabrics. In pertinent part, Note 2(a) to chapter 59, states that heading 5903 applies to:

Textile fabrics, impregnated, coated, covered or laminated with plastics, whatever the weight per square meter and whatever the nature of the plastic material (compact or cellular), other than:

(5) Plates, sheets or strip of cellular plastics, combined with textile fabric, where the textile fabric is present merely for reinforcing purposes (chapter 39).

In describing cellular plastics, the general EN to chapter 39 (page 718) state, in part:

Cellular plastics are plastics having many cells...dispersed throughout their mass. They include foam plastics, expanded plastics and microporous or microcellular plastics. [Emphasis added.]

Since the top two layers of the filter material consist of a polyamide plastic and a polysulfone plastic (the latter of which is approximately 200 times thicker than the former, and most likely much heavier, by weight), the terms of note 4 to chapter 39 may apply to the material’s classification. Note 4 states, in pertinent part:

For purposes of this chapter, except where the context otherwise requires, copolymers...and polymer blends are to be classified in the heading covering polymers of that comonomer unit which predominates by weight over every other single comonomer unit....

In Headquarters Ruling Letter (HQ) 955991, dated February 17, 1995, this office examined a filter membrane material imported as roll goods which, after post-importation processing, would be used to filter products such as pharmaceuticals, beer, water, intravenous solutions, etc. The product was prepared by a “phase inversion” process from a nylon 66 polymer and a nonwoven polyester textile. A description of the phase inversion process from Ullmann’s Encyclopedia of Industrial Chemistry, (Fifth Edition) was noted, and stated, in part, that the “precipitated polymer forms a porous structure containing a network of fairly uniform pores....[and that] Symmetric microporous membranes have been prepared from nylon 66....” Although the sample at issue in HQ 955991 appeared to have no openings or voids, photographs at 500X (cross section) and 2000X (top surface) magnification, revealed a microporous membrane. The product was classified as a cellular plastic in subheading 3921.19.0000, HTSUSA. See also NY A88742, dated July 1, 1997.

The filter membrane material of HQ 955991 was made up of two component materials, the nonwoven textile and the microporous cellular plastic. In this case, the RO membrane includes a third component material, i.e., the top layer, which is composed of a semipermeable polyamide plastic film. Although the film is semipermeable, you assert that it is not porous, and that its properties preclude classification of the complete material in a cellular plastic provision because the film is a nonporous, noncellular plastic. You note that the three-layered composite material is primarily used in the desalination of water by “reverse osmosis,” the process which occurs when a pressure greater than the osmotic pressure is applied to the concentrated side of a solution, causing the solvent to move from the more concentrated side into the dilute solution. You contend that the polyamide layer is key to performing this essential function, due to its thin nature, as well as its (electronically) charged and hydrophilic (“water loving”) properties, which allow water to pass through the film while holding back the dissolved salts. You maintain that the microporous polysulfone layer performs a secondary filtration function by trapping bacteria, viruses and larger solid particles, but that the presence of micropores render this layer unable to perform the primary function of the polyamide layer, i.e., desalination. You conclude
that the polyamide film therefore imparts the three-layered material’s essential character which, because the film is asserted to be nonporous and noncellular, requires classification in subheading 3921.90.1950, HTSUSA.

The layers comprising certain RO membranes were discussed in Filmtec Corporation v. United States, Slip Op. 03-153, 293 F. Supp 2d 1364 (Ct. Intl. Trade 2003), in which nonwoven fabric sheets described as “AWA No. 10” were at issue. The fabric, composed of 100 percent polyester fibers, was imported in rolls and was intended to eventually function as a support web for an RO membrane to be used in desalination. In the opinion’s background facts it was stated that, after importation, the AWA No. 10 fabric [similar to the nonwoven layer of this case] would first be coated with a microporous polysulfone interlayer [similar to the middle layer of this case] of approximately two thousandths of an inch in thickness, which would serve as a substrate support for the salt barrier layer. The salt barrier layer [similar to the top layer of this case] would be applied in the form of a second polymer coating. The court noted that “...this final layer furnishes the necessary filter characteristics of RO Membrane.” The court did not, however, indicate whether the top, semipermeable layer of a three-layered RO membrane is normally composed of a noncellular plastic, or a microporous cellular plastic.

CBP’s Office of Laboratory and Scientific Services (the lab) was asked to analyze a sample of the RO membrane at issue in this case. Lab Report Number SV20040032, dated February 18, 2004, states:

The sample, described as a “membrane film”, consists of a polyester nonwoven fabric that has been laminated to a layer of cellular polysulfone plastic. Information provided by the importer states that there is a very thin layer of noncellular polyamide on the outer surface of the polysulfone plastic. The presence of polyamide was detected. Based on SEM [scanning electron microscope] analysis and internet research, it is our opinion that the polyamide layer is noncellular.

The lab report was shared with CBP’s National Commodity Specialist Division (NCSD), particularly the National Import Specialists (NISs) for products of plastics, and products of coated fabric. Scientific research conducted by these NISs formed the basis of their opinions that the polyamide layers of RO membranes are normally considered to be porous (or microporous), and thus composed of cellular plastic. Since the basis of the lab’s opinion was internet research that was not specifically identified, and SEM analysis without stated magnifications, the lab was asked for clarification and/or supplemental information. Lab Report Number SV20040032S [Emphasis added to indicate a “supplemental” report], dated April 28, 2004, restates the text of the previous report (in indented text above) and adds the following:

This information supplements laboratory report SV20040032. SEM analysis was conducted at 1310X (cross section) and at 2060X & 4700X (top surface). Cellular structure was not observed in the polyamide layer.

These levels of magnification exceed those at which photographs revealed the porosity of the two-layered membrane in HQ 955991, and the term “not observed” (above) indicates this sample’s cellular structure could not be resolved to produce a photographic image. However, the inability to resolve or produce an image of the polyamide layer and observe cellular structure at high magnification does not establish that the polyamide layer is noncellular, particularly in the absence of specified sources of research, internet or other, upon which the lab’s opinion was based.

Several scientific sources support the likelihood that the semipermeable polyamide layer at issue contains pores. Hawley’s Condensed Chemical Dictionary, Fourteenth Edition (2001), defines “semipermeable membrane” as follows:

A microporous structure, either natural or synthetic, that acts as a highly efficient filter in the range of molecular dimensions, allowing passage of ions, water, and other solvents and very small molecules, but is almost impermeable to macromolecules (proteins) and colloidal particles. The thickness is about 100 [“” being the symbol for “angstrom,” a unit of length equal to one ten-billionth of a meter], the pore diameter is from 8 for the walls of tissue cells to 100 or more for manufactured membranes....Membranes of cellophane, collodion, asbestos fiber, etc., are used in such industrial operations as waste-liquor recovery, desalination, and electrolysis....

Scientific sources on the internet, including one affiliated with General Electric Company’s water technologies, can be found at: www.gewater.com. Click on “Technical Papers,” then on “Reverse Osmosis,” which leads to a large collection of scientific articles. For example, clicking on “Membranes the Finest Filtration” accesses an article which includes numerous references to the pores of RO membranes. The following paragraphs are excerpts from this article, several portions of which have had emphasis added.

Membrane filtration is the separation of the components of a pressurized fluid, effected by polymeric or inorganic membranes (generally man-made). The openings in the membrane material (pores) are so small that a significant fluid pressure is required to drive the liquid through them; the pressure required varies inversely with the size of the pores.... There are now four commonly accepted categories or "classes" of membrane, defined based on the
size of the material they will remove from the carrier liquid. Moving from the smallest to largest pore size, these are Reverse Osmosis (RO), Nanofiltration (NF), Ultrafiltration (UF), and Microfiltration (MF).

The exact mechanism [of RO salt rejection by sieving and electrochemical means] is both theoretical and disputed. There are at least two different schools of thought...Dr. Sourirajan's "surface-force-pore flow" approach. Simply put, the preferential sorption of water molecules and subsequent desorption of ions (repulsion by dielectric forces) causes exclusion of charged solutes even smaller than the membrane pores from movement through the membrane. The alternate "solution-diffusion" theory, stated simply, holds that RO membranes are like porous films in which both solvent and solute "dissolve" into the membrane. The solute moves through the membrane mainly under concentration gradient forces, while the solvent transport is dependent on the hydraulic pressure gradient.

Pores in reverse osmosis membranes are so small they have not yet been resolved, even by the most advanced microscopic techniques. They are generally regarded to be in the 4 to 8 [angstrom] range, four orders of magnitude smaller than the finest of the normal-flow particle filters.

Returning to the collection of articles found under the heading “Reverse Osmosis,” and clicking on “Crossflow Membrane Filtration High-Purity Water Systems,” accesses an article describing a polymeric pore size range which varies only slightly from the 4 to 8 range stated above. An excerpt from the article states:

Membrane filtration involves separation of dissolved, colloidal and particulate constituents from a pressurized fluid using a microporous material (usually polymeric media). The size of the polymer's pores categorizes the membrane into one of the following groups: reverse osmosis, nanofiltration, ultrafiltration and microfiltration. Reverse osmosis (RO) membranes have the smallest pore size ranging from 5-15 angstroms, nanofiltration (NF) covers separations in the 15-30 angstrom size, ultrafiltration (UF) removes organics in the 0.002-0.2-micron range and microfiltration (MF) effects separation in the 0.02-2.0-micron range. [Emphasis added.]

Since it appears that the most advanced microscopic techniques have yet to resolve, or make independently visible, a polymer’s pores on the outer layer of an RO membrane, the CBP lab’s inability to view the polyamide it detected and observe
cellular structure is certainly understandable. Although we cannot verify that the polyamide is a cellular plastic, the scientific literature presented above strongly indicates that such types of filtration materials are microporous, and the EN to chapter 39 state that cellular plastics include microporous plastics. The fact that the middle, polysulfone layer of the material is a cellular plastic is not in dispute, nor is the fact that the layer is approximately 200 times thicker (and likely heavier) than the polyamide layer. Although we do not rely on its legal effect in this case, it appears that note 4 to chapter 39, cited above, would provide additional support for classifying the RO filtration membrane in the cellular plastic provision (according to the polymer that predominates by weight). In light of the analysis above, we find that the reverse osmosis filtration membrane material is classified in subheading 3921.19.0000, HTSUSA.


The reverse osmosis filtration membrane (a three-layered material known in the industry as a “fully aromatic polyamide thin film composite”) is classified in subheading 3921.19.0000, HTSUSA, the provision for “Other plates, sheets, film, foil and strip, of plastics: Cellular: Of other plastics.” The general column one duty rate is 6.5 percent ad valorem.

A copy of both this ruling letter and NY I84349 should be provided with the entry documents filed at the time this merchandise is imported.


Myles B. Harmon, Director

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