[Code of Federal Regulations]
[Title 21, Volume 3]
[Revised as of January 1, 2007]
From the U.S. Government Printing Office via GPO Access
[CITE: 21CFR177.1640]
[Page 314-315]
TITLE 21--FOOD AND DRUGS
CHAPTER I--FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN
SERVICES (CONTINUED)
PART 177 INDIRECT FOOD ADDITIVES: POLYMERS--Table of Contents
Subpart B Substances for Use as Basic Components of Single and Repeated
Use Food Contact Surfaces
Sec. 177.1640 Polystyrene and rubber-modified polystyrene.
Polystyrene and rubber-modified polystyrene identified in this
section may be safely used as components of articles intended for use in
contact with food, subject to the provisions of this section.
(a) Identity. For the purposes of this section, polystyrene and
rubber-modified polystyrene are basic polymers manufactured as described
in this paragraph so as to meet the specifications prescribed in
paragraph (c) of this section when tested by the method described in
paragraph (d) of this section.
(1) Polystyrene consists of basic polymers produced by the
polymerization of styrene.
(2) Rubber-modified polystyrene consists of basic polymers produced
by combining styrene-butadiene copolymers and/or polybutadiene with
polystyrene, either during or after polymerization of the polystyrene,
such that the finished basic polymers contain not less than 75 weight
percent of total polymer units derived from styrene monomer.
(b) Optional adjuvants. The basic polymers identified in paragraph
(a) of this section may contain optional adjuvant substances required in
the production of such basic polymers. Such optional adjuvant substances
may include substances permitted for such use by regulations in parts
170 through 189 of this chapter, substances generally recognized as safe
in food, and substances used in accordance with a prior sanction or
approval.
(c) Specifications. (1) Polystyrene basic polymers identified in
paragraph (a)(1) of this section shall contain not more than 1 weight
percent of total residual styrene monomer, as determined by the method
described in paragraph (d) of this section, except that when used in
contact with fatty foods of Types III, IV-A, V, VII-A, and IX described
in table 1 of Sec. 176.170(c) of this chapter, such polystyrene basic
polymers shall contain not more than 0.5 weight percent of total
residual styrene monomer.
(2) Rubber-modified polystyrene basic polymers identified in
paragraph (a)(2) of this section shall contain not more than 0.5 weight
percent of total residual styrene monomer, as determined by the method
described in paragraph (d) of this section.
(d) Analytical method for determination of total residual styrene
monomer content--(1) Scope. This method is suitable for the
determination of residual styrene monomer in all types of styrene
polymers.
(2) Principle. The sample is dissolved in methylene chloride. An
aliquot of the solution is injected into a gas chromatograph. The amount
of styrene monomer present is determined from the area of the resulting
peak.
(3) Apparatus--(i) Gas chromatograph. Beckman GC-2A gas
chromatograph with hydrogen flame detector or apparatus of equivalent
sensitivity.
(ii) Chromatograph column. One-quarter inch outside diameter
stainless steel tubing (0.028 inch wall thickness), 4 feet in length,
packed with 20 percent polyethylene glycol (20,000 molecular weight) on
alkaline treated 60-80 mesh firebrick.
[[Page 315]]
(iii) Recorder. Millivolt range of 0.1, chart speed of 30 inches per
hour.
(4) Reagents. Compressed air, purified; helium gas; hydrogen gas;
methylene chloride, redistilled; and styrene monomer, redistilled.
(5) Operating conditions for the gas chromatograph. (i) The column
is operated at a temperature of 100 [deg]C with a helium flow rate of 82
milliliters per minute.
(ii) The hydrogen burner is operated with 15 pounds per square inch
of air pressure and 7 pounds per square inch of hydrogen pressure.
(iii) The attenuation of the hydrogen flame detector is set at
2x10\2\.
(6) Standardization. (i) Prepare a standard solution by weighing
accurately 15 to 20 milligrams of styrene monomer into a 2-ounce bottle
containing 25.0 milliliters of methylene chloride. Cap the bottle
tightly and shake to thoroughly mix the solution.
(ii) By means of a microliter syringe, inject 1 microliter of the
standard solution into the gas chromatograph. Measure the area of the
styrene monomer peak which emerges after approximately 12 minutes.
(7) Procedure. (i) Transfer 1 gram of sample (accurately weighed to
the nearest 0.001 gram to a 2-ounce bottle and add several glass beads.
Pipette 25.0 milliliters of methylene chloride into the bottle. Cap the
bottle tightly and place on a mechanical shaker. Shake until the polymer
is completely dissolved. If any insoluble residue remains, allow the
bottle to stand (or centrifuge at a low speed) until a clear supernatant
layer appears.
(ii) By means of a microliter syringe, inject 3 microliters of the
clear supernatant liquid into the gas chromatograph.
(iii) Measure the area of the resulting styrene monomer peak.
Compare the sample peak area with the area produced by the standard
styrene monomer solution. Calculation:
Percent residual styrene monomer=Milligrams monomer in standardxpeak
area of sample/Peak area of monomer standardxsample weight in gramsx30
(e) Other specifications and limitations. The polystyrene and
rubber-modified polystyrene identified in and complying with this
section, when used as components of the food-contact surface of any
article that is the subject of a regulation in parts 174, 175, 176, 177,
178 and Sec. 179.45 of this chapter, shall comply with any
specifications and limitations prescribed by such regulation for the
article in the finished form in which it is to contact food.
(f) Nonapplicability. The provisions of this section are not
applicable to polystyrene and rubber-modified polystyrene used in food-
packaging adhesives complying with Sec. 175.105 of this chapter.
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