§175.270 聚氟乙烯树脂(Poly（vinyl fluoride� resins)

��175.270 Poly(vinyl fluoride) resins
　　

Poly（vinyl fluoride� resins identified in this section may be safely used as components of food-contact coatings for containers having a capacity of not less than 5 gallons, subject to the provisions of this section.

　　（a� For the purpose of this section, poly（vinyl fluoride� resins consist of basic resins produced by the polymerization of vinyl fluoride.

　　（b� The poly（vinyl fluoride� basic resins have an intrinsic viscosity of not less than 0.75 deciliter per gram as determined by ASTM method D1243-79, ��Standard Test Method for Dilute Solution Viscosity of Vinyl Chloride Polymers,�� which is incorporated by reference. Copies may be obtained from the American Society for Testing Materials, 100 Barr Harbor Dr., West Conshohocken, Philadelphia, PA 19428-2959, or may be examined at the National Archives and Records Administration （NARA�? For information on the availability of this material at NARA, call 202-741-6030, or go to:http://www.archives.gov/federal_register/code_of_federal_regulations/ibr_locations.html.

　　�?� Solvent. N,N- Dimethylacetamide, technical grade.

　　�?� Solution. Powdered resin and solvent are heated at 120 ��C until the resin is dissolved.

　　�?� Temperature. Flow times of the solvent and solution are determined at 110 ��C.

　　�?� Viscometer. Cannon-Ubbelohde size 50 semimicro dilution viscometer （or equivalent�?

　　�?� Calculation. The calculation method used is that described in appendix X 1.3 （ASTM method D1243-79, ��Standard Test Method for Dilute Solution Viscosity of Vinyl Chloride Polymers,�� which is incorporated by reference; see paragraph （b� of this section for availability of the incorporation by reference� with the reduced viscosity determined for three concentration levels not greater than 0.5 gram per deciliter and extrapolated to zero concentration for intrinsic viscosity. The following formula is used for determining reduced viscosity:

　　Code of Federal Regulations

　　[Please see PDF for image: ER01JA93.387 ]

　　　where:

　　t=Solution efflux time.

　　to=Solvent efflux time.

　　c=Concentration of solution in terms of grams per deciliter.

　　Code of Federal Regulations

　　[42 FR 14534, Mar. 15, 1977, as amended at 47 FR 11839, Mar. 19, 1982; 49 FR 10107, Mar. 19, 1984]