80
Ind. Eng. Chem. Prod. Res. Dev., Vol. 17, No. 1 , 1978
Permeability of Organic Vapor through Packaging Films. 1 Barney W. Hllton and Scott Y. NeeC1 Frito-Lay lnc., Dallas, Texas 75245
Industry uses data on oxygen and water vapor permeability through films to justify the quality and the applicability of polymeric films. Recent attention has been called upon the penetration of kerosene vapor through packaging films of snack food products. The present study indicates partially the complexity of the penetration of organic vapor through the films and substantiates the fact that the presence of polyester as one of the laminated layers does improve the barrier quality of the film. Data have been expressed as permeation coefficients for each of the organic vapor-packaging film combinations.
Introduction The permeability of plastic films and other packaging materials to gases and vapors is of great practical interest as well as commercial importance. In particular, the knowledge of the permeability constants for water vapor, carbon dioxide, nitrogen, and oxygen has been expanded in the design of packaging to prevent deterioration due to excessive loss or gain of such gases during storage. The transmission of a gas or vapor through a plastic film is normally, i.e., in the absence of cracks, pinholes, or other flaws, of the activated diffusion type. This process can be described as the gas or vapor adsorbed at the surface of the film, diffusion through the film under a concentration gradient, and desorption from the other surface a t the low concentration, Le., low-pressure side. Under steady-state conditions, Fick’s law (Fick, 1855) holds and states that the transmission follows the relationship: q = -D dclldx, where D is the diffusion coefficient. Experimentally, in this case, the most common way of measuring the diffusion coefficient is based on measuring the increase of pressure with time on the low-pressure side of the film under high vacuum systems (Rogers et al., 1956). This is generally true for permanent, inorganic gases, like oxygen, nitrogen, and carbon dioxide. Deviations occur with water (Taylor et al., 1936; Hauser and McLaren, 1948; Cutler and McLaren, 1953), and become inapplicable to organic vapors (Bent and Pinsky, 1965). The function of the packaging film is twofold: to keep bad odors out, and to keep the aroma of snack products in the package. The industry is generally using oxygen permeability values as a measure of organic vapor transmission with the reasoning that the aroma odors should be large molecules, would have less penetration, and as a result would have exactly analogous transmission rates to that of oxygen. As a matter of fact, this is not true (Cutler et al., 1951). Variables such as the composition of the polymer resin, its electronic structure, the solubility of the organic molecules in the polymer, and the potential interaction between the polymers and the vapor component necessitate further study on the penetration of organic vapor through packaging films (Rouse, 1947). The authors have been concerned about the hazards of food products becoming off-flavored by exposure to kerosene (a quiet mixture of hydrocarbons), since kerosene is used as fuel in their trucks and also as a base for the insecticides used to spray the inside of the trucks. Hydrocarbons in kerosene consist of paraffins, cycloparafflis, and cyclic aromatics in the range of C ~ O - C ~InO products . produced by incomplete combustion, olefins or compounds with carbon-carbon double bonds not in aromatic rings are also found. To whom all correspondence should be addressed a t 5939 Burchard Ave., Los Angeles, Calif. 90034.
0019-789017811217-0080$01.00/0
Basically a number of different test methods can be divided into two main groups-subjective (or organoleptical) tests, and objective (or instrumental) tests. Organoleptical techniques are commonly used to obtain olfactory threshold data in evaluating the flavor significance of any given compound (Brockington, 1958; Guadagni et al., 1963; Stone, 1963; Sullivan 1973). Widespread use of gas chromatography has demonstrated that food products usually contain a considerable number of volatile compounds that can contribute to flavor (Simril and Hershberger, 1950; Muldoon et al., 1951; Koehler and Odell, 1970). It is a known concept that polymers least permeable to organic vapors are those whose molecular structure is such as to permit close packing, strong intermolecular bonding, and whose adsorption, or solution, of vapor is low. Highly polar, strongly bound polymers are less permeable to nonpolar gases than are the less polar weakly bound polymers (Simril and Hershberger, 1950).The presence of bulky side chains and the introduction of plasticizers increase permeability in general. Chemical and electrical similarity of polymer and vapor increases solubility and, therefore, permeability. The purpose of this study is to obtain, by means of simple apparatus, quantitative and reliable values for the rate of permeation of several vapors representative of four classes of organic compounds through a number of polymeric films. Meanwhile, the effect of structural constituents on permeation is discussed in terms of the rate of organic vapor transfer through plastic films. The apparatus is designed so that the amount of organic vapor which permeates through the film is measured directly by gas chromatography.
Materials and Method In order to study the effect of kerosene exposure on the flavor or products through the packages, we proceeded on how readily the material will or will not permit organic vapors to pass through it. When choosing the organic vapor to be used in the test, four factors had to be considered. First, the material had to be volatile. Second, it should be representative of a large number of commonly encountered odors. Third, it had to have characteristics that would render it suitable for measurement on the gas chromatograph. Fourth, it had to be fairly stable. From the layout of relative retention times for the particular chromatographic column, four solvents were selected to be representative of four groups of organic compounds. They are n-decane, 1-heptene, toluene, and ethanol. They were purchased from Eastman Kodak Company and are chromatographic grade organic chemicals. The determinations of permeability were made on the basis of 100%relative vapor-pressure differential across the films 0 1978 American Chemical Society
Ind. Eng. Chem. Prod. Pes. Dev., Vol. 17, No. 1, 1978
81
Table I. Compositions of Packaging Films No.
Film
ComDosition
01 5122-7
48 Gauge polyester/Adh/l.5 mil CO-X TS/75 B513/15# PE/50 XMO-1 TS/75GA BOPP/lO# PE/Adh/220 polymer-coated cellophane 04 CC1175-550 48 Gauge polyester/7# opaque PE/1.25 mil HDPE 05 3506 250 Polymer-coated cellophane/Adh/65 GA BOPP (CIS) 06 3311 0.48 mil polyester/Adh/l.75 mil HDPE/ EVA 07 CC1175-147 0.48 mil polyester/7# PEh.25 mil HDPE 08 AM-C-100 TS/0.00048 polyester/Adh/l mil Bartuff TS/0.00048 polyester/Adh/l.5 mil Bartuff 09 AM-C-150 75 Gauge PVDC-coated polyester 10 75XMO-2 11 5115-7 250 Cellophane/Adh/l.5 mil CO-X 12 AM-C-75 TS/0.00048 polyester/Adh/0.75 mil Bartuff 13 5122-4 TS/250 K/Adh/l.5 mil HDPE 14 5115-4 TSl250 coated cellophane/Adh/0.15 mil HDPE 15 Opaque Cellophane Cellophane 16 3588 TW0.73 mil OPP/12# PE/25# glassine 5 # Saran 17 25OXCP-686 Cellophane 18 CHC376-688 Cllophane/polypropylene 250 Saran-coated cellophane 19 5011 TS/Adh/250 cellophanePP 20 5003 21 Metallized Foil 0.5 mil HDPE/0.35 mil A1 foi1/25# pouch paper/lO# Surlyn 22 Potato chip Material 0.75 mil PP/Adh/25# glassine, 5# Saran 23 5122-6 250 cellophane/Adh/l.75 mil CO-X LDPE 24 LDPE 25 CC374-982 1mil OPP/8# PE/2 mil white HDPE 26 Twin pack CO-X (80% HDPE + 20% EVA) and 30# sulfites/l2# WAX 27 CC876-818 1 mil PP/8# PE/2.15 mil HDPEEVA 28 76-9 TS/75 B513/7# PEl0.7 mil SC-30 29 3509-6 250 Polymer-coated cellophane/lO# opaque PE/1 mil BOPP (CIS) 02 32Y 03 3324
Table 11. Glossarv of Packaging Films TS B513 GA CIS Bartuff K Surlyn
cz XMO xc
EVA LDPE HDPE BOPP 1 mil
#
Thermostrip A type of polypropylene Gauge Coated one side A type of polypropylene Saran-coated cellophane A type of polyethylene Crown Zellerbach (name of supplier) Saran-coated polyester Acrylic-coated polypropylene Ethylene vinyl acetate copolymer Low density polyethylene High density polyethylene Biaxially oriented polypropylene 0.001 in. pounds
and were calculated a t 23 "C and 760 mmHg for all film-vapor combinations. Method of Testing the Permeability of Organic Vapor t h r o u g h Packaging Films A. Scope. This method covers the determination of penetration of organic vapor through plslstic films sheeting, laminates, and polymer-coated papers. A standard test vessel is
r: view
Front view
Top
of a chamber
of a chamber
Side view of the test vessel
Figure 1. Test vessel.
-9 -6
-6 *
Simple
digit
number
code
assigned
30 20
Figure 2. Table 111. Vapor Pressures of Four Organic Solvents at 23 "C Organic solvent
Vapor pressure, nmHe
n-Decane 1-Heptene Toluene Ethanol
1.5 51.7 27.4 53.3
used for room-temperature determinations. This method does not cover determination of the rate of water vapor or oxygen. In comparison with other methods, it is more convenient and less expensive in apparatus, a t the same time retaining a high degree of accuracy. B. Apparatus. (1)Test vessel. The vessel shown in Figure 1consists of two identical chambers, both of which are made of stainless steel. Each chamber is sealed by a column-shaped wall (radius = 2.2 in., height = 5 in.), and flat bottom plate on three sides. One side which is left open has a circular rim (width = 0.7 in.). Each of the four nozzles is covered by a rubber septum, and then a stainless steel nut. The area of films exposed to organic vapor is 47.78 cm2. (2) Gas chromatograph.
82
Ind. Eng. Chem. Prod. Res. Dev., Vol. 17, No. 1, 1978
Table IV. Percentage Penetration Values of Organic Vapors through Packaging Films Sum of Av % penetrationlstd dev 4-digit number No. Film code n-Decane 1-Heptene Toluene 01 02 03 04 05 06 07 08 09 10
5122-7 32Y 3324 CC1175-550 3506 3311 CC1175-547
AM-C-100 AM-C-150 75XMO-2 11 5115-7 12 AM-(2-75 13 5122-4 14 5115-4 15 Opaque Cellophane 16 3588 17 25OXCP 686 18 CHC 376-688 19 5011 20 5003 21 Metallized foil 22 Potato chip material 23 5122-6 24 LDPE 25 CC374 982 26 Twin pack 27 CC876-818 28 76-9 29 3509-6
0 0
0.07
0.01 0.05 0.1 0.006
1.0
0.1
9.5
0.2 0.02 0.01 0.005 0.0002 0.3 0.3 0.2 0.3
0.1
1.4
0 0 1 1 1 1 1 1 2 2 2 2 3
0.08 0.08 0.001 15.1 13.4 2.7 4.3 2.0
3 4 5 5 6 7 8
16.2 1.4 7.7 17.9 11.0 38.4 40.8
2.1 0.3 1.2 2.0 1.0 1.9 2.3
3.2 4.8 4.4 11.8 5.3
8 29 34 34 35 36 36
15.2 70.4
2.0 2.4 0.4 0.4 6.5 0.9 0.7
89.1 92.3 94.5 96.4 94.6 91.0
1.1
0.1
71.3
98.3 93.0 89.6 93.5
Table V. Statistical Computation of Regression Line and Correlation Coefficient Correlation between Coefficient (Thickness % Penetration Regression of in mils) X Y line correlation
Polyester
Decane Heptene Toluene Ethanol
Polyethylene
Decane Heptene Toluene Ethanol Decane
Y = -2.426 + 19.71X Y = -22.19 36.61X Y = -19.75 41.65X Y = -74.06 114.98X Y = 0.24 - 0.30X Y = 0.039 - 0.016X Y = 0.084 - 0.033X Y = +40.27 73.75x Y = 20.84 16.09X Y = 14.22 + 20.20X Y = 18.58 + 19.13X Y = 21.49 + 13.39X Y = 37.66 - 5.609X
Heptene Toluene Ethanol
Y = 31.26 - 4.434X Y = 28.71 1.264X Y = 7.875 23.29X
Cellophane
Decane Heptene Toluene Ethanol
Polypropylene
0.04 0.02 0.35 0.007 0.35 3.0 0.04 0.007 0.007 0.01 0.3
+ + +
I
+
+ +
0.0758 0.1398 0.1658 0.4108 0.7743 0.8079 0.9244 0.6055 0.2955 0.3425 0.3394 0.2484 -0.0606 -0.0415 0.0124 0.2459
The model is a Perkin-Elmer 900-B. The recorder is Form 56, also from Perkin-Elmer. The glass column, 6 ft long, is packed with 2% OV-17 + 1%OV-210 on 100/120 Supelcoport. (3) Gas-tight syringe. C. Materials. (1)Chromatographic grade organic chemicals (e.g., n-decane, 1-heptene, toluene, and ethanol).
1.1
0.7
2.0 0.8 1.2 4.1 0.5
0.1
Ethanol
0.002
0.003
0.001
0.1
0.03 0.0002 0.03 0.6 0.003 0.0002 0.0005 0.002 0.02 0.01 0.2 0.3
2.7 0.02 2.7 3.4 0.06 0.01 0.01 0.01 0.4 1.3 13.2 6.5 6.7
0.2 0.2 0.2 0.9 0.4 0.6 0.5
7.8 5.7 21.5 13.7 26.5 27.7 16.9
0.00002 4.6 0.001 3.5 4.2 0.08 0.9 0.001 5.3 0.3 3.5 0.4 5.4 0.01 9.7 0.002 0.002 12.9 0.005 11.4 0.02 15.4 0.1 5.9 1.5 11.7 1.3 5.3 0.4 21.5 3. 3.6 0.6 27.5 1.1 21.3 2.1 1.3 1.3 2.1 21.5 2.9 1.1 0.6 0.5
0.02 0.4 1.9 0.9 3.2 0.8 0.9
0.2 84.3 90.9 96.6 96.2 95.0 90.1
0.03 1.3 1.4 0.8 3.3 1.2 0.2
0.1
57.1 61.4 87.1 76.9 76.2 97.5 97.8
0.8 0.08 0.02 0.01 0.3 0.05 0.5 0.2 2.1 0.2 0.3 1.1 1.8 0.7 2.8
0.1 2.2 0.4 0.02 2.6 0.2 0.02 5.5
3.6 0.5 4.0 4.5 0.6 0.5
D.Procedure. (1)Transfer equal weight mixture of organic compounds to the lower chamber. Total volume of liquid is about 50 mL to make a saturated organic vapor of constant temperature. (2) Place the film being tested between the two chambers. (3) Tighten the eight nuts around the test vessel. (4) The vessel is placed a t the top of the bench, with clean surroundings, a t room temperature (23 "C). (5) After 24 h of standing a t room temperature, same amounts of gaseous samples are taken from both the upper and lower chambers. The gaseous sample is injected into the gas chromatograph, and the recorder is used to record the output on the graph paper. Temperature programming rate is 4 "C/min from 60 to 180 "C. (6) Usually three samplings are required from each chamber. (7) After 48 h of standing a t room temperature, repeat step 6. (8) With a different film, repeat steps 1through 7. E. Calculations. (1) For each of the organic compounds: A1 = the average area in the chromatogram for the sample from the upper chamber after 24 h standing; A2 = the average area in the chromatogram for the sample from the lower chamber after 24 h standing; A3 = the average area in the chromatogram for the sample from the upper chamber after 48 h standing; A4 = the average area in the chromatogram for the sample from the lower chamber after 48 h standing. Percentage penetration value = [ ( A I / A 2 ) ( A 3 / A 4 ) ] / 2 = PAB/100. PAB has numerical values in the range from 0 to 100, corresponding to which is the set of one digit numbers from 0 to 9. (See Figure 2.) If the value of PAB falls within the range from 35.0 to 44.9, the simple digit number code "4" is assigned to this compound for this particular film. Therefore, the lower the PAB or the simple digit number code, the less permeable is the film for this compound. Example. Take film no. 24 LDPE for instance. (1)After 24
+
Ind. Eng. Chem. Prod. Res. Dev., Vol. 17, No. 1, 1978
83
Table VI. Component Frequency for Composition of Films Polyethylene No.
Film
CelloDhane Polvester PE
Polypropylene
LDPE HDPE Surlvn P P B513 BOPP Bartuff XC
02 03 04 05 06 07 08 09 10 11 12
13 14 15 16 17 18
19 20 21
22
23 24 25 26 27
28 29
32Y 3324 CC1175-550 3506 3311 CC1175-547 Am-(2-100 Am-C-150 75XMO-2 5115-7 Am-(2-75 5122-4 5115-4 Opaque cellopane 3588 25OXCP686 CHC376688 5011 5003 Metallized foil Potato chip material 5122-6 LDPE CC374-982 Twinpack CC876-818 76-9 3509-6
OPP Adhesive TS
X
X
01 5122-7
X
X X
X
X
X
X
X X
X X X X
X X
X
X X X X
X X X X
X X
X
X
X X
X
X X X
X
X
X
X
X
X
X
X X X
X
X X
X X X
h standing with C10H22, we obtain the following ratio from chromatograms of the upper and the lower chambers: AlIA2 = 60.6%. After 48 h standing, we obtain the second ratio: A3/A4 = 80.2%. The percentage penetration value (for decane) = 70.4%; PAB (for decane) = 70.4. Simple digit number code (for decane) assigned is 7. (2) Simple digit number code (for 1-heptene) assigned is 8. Simple digit number code (for toluene) assigned is 8. Simple digit number code (for ethanol) assigned is 6. Hence, the sum of 4-digit number code is 29. The testing over periods of 1week shows that generally the penetration of organic vapors (all four solvents) exhibits the highest slope between 0 and 48 h of exposure. The product of percentage penetration value and the vapor pressure of the organic compound gives the permeation coefficient PA, (PB,Pc, and PD)in mmHg/(100 cm2 24 h atm), which is the rate of transfer of a vapor across a film, per unit area, per unit time interval, and characterizes the effectiveness of the film as a barrier. D a t a a n d Results The results obtained and presented in this study apply only to the actual films measured. There is such wide variation in the permeability of commercial films of the same trade name that it would be incorrect to attach to any class of films the specific values recorded below, which are based on the measurement of only a few film samples. Actual differences in the films can cause fluctuations in systematic measurements to such an extent that incorrect conclusions can often be drawn inadvertently (Doty et al., 1944). We therefore have to limit the validity of our conclusions and observations to the actual
X X
X X
films tested in this study. Measurements were made a t room temperature (about 23 "C) for all film-vapor combinations. Discussion The mechanism of transport of small molecules through polymers has been the concern of numerous investigators in recent years. Factors involved include size of the vapor molecules, relative structures of the vapor molecule and monomer of the film, thickness (or density) of the packaging film, aside from concentration gradient of the vapor molecule, and the temperature of the environment. It was reasonable to assume that a combination of films whose total individual barrier characteristics were good should itself be a good barrier for most types of vapors. With simple terms (Hunt and Lansing 1935; Russell et al., 1937; Shipley et al., 1939),the mechanism of transport may be stated in terms of the following two processes. A. The smaller the molecule the easier it goes through the film at the start. Small molecules flow through: (1)preformed holes or capillaries-a process said to be unactivated; (2) holes which are opened temporarily by the thermal motion of the polymer chains-an activated process temperature dependent. B. The closer the relative structures, the rate of penetration of these molecules is more likely to have a steady value over a longer period of time-a solubility phenomenon. The diffusion molecule can be adsorbed on one of the active spots on the internal surface of the polymer and vibrate in this position until it acquires sufficient energy to evaporate from this position. I t can move on to other active spots in the direction of decreasing pressure. If the active spot had been
Ind. Eng. Chem. Prod. Res. Dev., Vol. 17, No. 1, 1978
84
Table VII. Permeation Coefficients Permeation coefficients x lo2 [mmHg/(100cm2 24 h atm)] PA
Film
No. 01 02 03 04 05 06 07 08 09 10 11
12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29
(n-Decane)
5122-7 32Y 3324 CC1175-550 3506 3311 CC1175-547 Am-'2-100 Am-C- 150 75XMO-2 5115-7 Am-C-75 5122-4 5115-4 Opaque Cellophane 3588 24OXCP 686 CHC 376-688 5011 5033 Metallized foil Potato chip material 5122-6 LDPE CC374-982 Twin pack CC876-818 76-9 3509-6
0.31 4.4 3.5 0.22 3.1 29.8 0.31 0.25 0.25 0.0031 47.4 42.1 8.5 13.5 6.3 50.9 4.4 24.2 56.2 34.5 120.6 128.1 47.7 221.0 223.8 308.6 291.9 281.3 293.5
Table VIII. Thickness and Rough Estimate of Oxygen Permeability of Films
No.
Film
01 02 03 04 05 06 07 08 09
5122-7 32Y 3324 CC1175-550 3506 3311 CC1175-547 Am-C-100 Am-C-150 75XMO-2 5115-7 Am-C-75 5122-4 5115-4 Opaque Cellophane 3588 25OXCP 686 CHC 376-688 5011 5003 Metallized foil Potato chip material 5122-6 LDPE CC374-982 Twin pack CC876-818 76-9 3509-6
10 11
12 13 14 15 16 17 18 19 20 21
22 23 24 25 26 27 28 29
Soap 0 2 aroma perme- Thickness, transmission ability mils 1 1 1 1 1 1 1 1 1 1 1 1
3
1 1
3 3
1 1 1
0.5
250
1
150 1
3.0 2.2 2.5 2.4 2.4 2.4 2.5 2.5 2.7 1.0 3.0 2.5 2.7 2.6 1.0 3.2 1.0 2.5 1.0 2.8 4.1 2.5 3.0 1.25 4.0 5.2 4.0 2.0 2.8
PB
(1-Heptene) 4.3 2.2 37.9 0.76 37.9 324.6 4.3 0.76 0.76 1.1
32.5 75.7 216.4 86.6 129.8 443.6 54.1 346.3 519.4 476.1 1276.8 573.5 10.8 9641.0 9987.3 10225.3 10430.9 10236.1 9846.6
Pc (Toluene) 0.017 5.7 154.8 1.1
154.8 194.9 3.4 0.57 0.57 0.57 22.9 74.6 756.9 372.7 384.2 447.3 326.9 1232.9 785.6 1519.7 1588.5 969.2 11.5 4834.3 5212.8 5539.6 5516.7 5447.9 5166.9
PD
(Ethanol) 513.1 390.4 468.5 100.4 591.2 390.4 602.4 1082.1 1439.0 1271.7 1717.9 658.2 1305.2 591.2 2398.4 401.6 3067.7 2376.1 145.0 2398.4 122.7 55.8 6369.7 6849.4 9716.3 8578.4 8500.3 10876.4 10909.9
involved in interaction with another portion of its chain or with an adjacent chain, thus forming an intra- or intermolecular bond, adsorption of a foreign particle might weaken the bond or even disrupt it entirely. Such weakening of intermolecular forces increases the diffusion through either of the two above processes. On the other hand, packaging films manufactured nowadays have coextruded structures (Eidman, 1975) produced by extrusion coating, multilayer laminating, cast and blown film. Processing of the films involves many different phases (Talwar, 1974), for example, release treatment, heat seal, moisture content, types of plasticizer, surface treatment, and barrier materials on a carrier resin. Any structural modifications such as density changes, degrees of crystallinity, orientation, and cross-linking, as well as additives such as plasticizers and fillers, greatly affect the barrier properties of a polymer. Almost all of the films in this study possess coextruded composite structures, which makes the correlation of oxygen permeability values for many simple polymers difficult. Twenty nine polymeric films were investigated during this study. They are listed together with their compositions in Table I. Table I1 is a glossary related to the composition of packaging films. Table I11 lists the vapor pressures of four organic solvents at room temperature (23 "C).Table IV is a compilation of percentage penetration values of organic vapors through packaging films, where the order of listing of films runs roughly in parallel with the quality of the film in preventing the penetration of different organic vapors. Table V shows the statistical computation of regression lines and coefficients of correlation. Table VI splits the composition of each film into components, so that component frequency can be used in evaluating the barrier ability of films. Figure 3 is just such a plot in the evaluation. The statistical correlation
Ind. Eng. Chem. Prod. Res. Dev., Vol. 17, No. 1, 1978
Conclusions
Adjusted Component Frequency
12
85
i
.i
\
\
The conclusions which can be drawn from this study relating the penetration of four types of organic solvents and the structural constituents concerning the structure of packaging films are listed below. (1)Polyesters add value for the film, making the film less permeable to four types of organic vapors. (2) Polyethylene or polypropylene alone is not enough to stop the penetration of organic vapor. (3) Thermostrip and adhesive both impart a positive (better barrier) effect on the quality of films toward penetration. (4) No definite effect can be stated for cellophane (uncoated or polymer-coated). (5) Films with low penetration of organic vapor also have low values of oxygen permeability, i.e., less than 3 cm3/(100 in.2 24 h atm) (which is the lowest limit measurable accurately for oxygen permeability). The latter is a rough estimate because of the presence of constituents of low oxygen permeability in the lamination. (6) Conceivably, films close to the top of the compilation are better odor barriers as far as the four types of organic vapors are concerned. L i t e r a t u r e Cited
Films o f Decreasing Quality
Figure 3. Adjusted component frequency vs. q u a l i t y of 29 films.
coefficients in Table V and the graph of adjusted component frequency in Figure 3 give a good indication that polyester is a good ingredient in increasing the barrier ability of films, which is our first conclusion for the study. Table VI1 is the tabulation of permeation coefficients in units of mmHg/( 100 cm2 24 h atm) for each of the vapor-film combinations. The thickness of the film is not included in the definition of permeation coefficient because it cannot be used as a valid criterion to characterize the barrier property of the composite, laminated film (Doty et al., 1944). Table VI11 lists the thickness and rough estimate of the oxygen permeability of various films.
Bent, H. A,, Pinsky, J., WADC Tech. Rep. 53, 133 (1965). Brockington, S.F.,Package Eng., 27 (Jan 1958). Cutler, J. A., Kaplan, E., McLaren, A. D., Mark, H., TAPPI, 34, 404 (1951). Cutler, J. A.. McLaren, A. D., TAPPI, 36, 423 (1953). Doty, P. M., Aiken, W. H., Mark, H., Ind. Eng. Chem., Anal. Ed., 16, 666 (1944). Eidman, R. A. L., International TAPPi Coextrusion Seminar, Copenhagen, Denmark, 1975. Fick, A.. Ann. Phys., 94, 59 (1855). Guadagni, D. G., Butlery, R. G., Okano, S., J. Sci. Food Agric., 14, 761 ( 1963). Hauser, P. M., McLaren, A. D., lnd. Eng. Chem., 40, 112 (1948). Hunt, J., Lansing, D., Ind. Eng. Chem., 27, 26 (1935). Koehler, P. E., Odeil, G. V.. J. Agric. FoodChem., 18, 895 (1970). Muldoon, T. J.. Couch, R. de S.,Barnes, H. M.. Mod. Packag., 123 (Jan 1951). Rogers. C.. Meyer, J. A., Stannett, V., Szwarc. M.. TAPPI, 39, 737. 741 (1956). Rouse, P. E., J. Am. Chem. SOC., 69, 1066 (1947). Russell, J. K., Maass, O., Campbell, W. B., Can. J. Res., B15, 13 (1937). Shipley, W., Campbell, W. B., Maass, O., Can. J. Res., 817, 40 (1939). Simril. V. L., Hershberger. A., Mod. Plast., 27, 95, 97 (1950). Stone, H.. J. Sci. FoodAgric., 14, 719 (1963). Sullivan, F., Package Eng., 66 (March 1973). Talwar, R.. Package Dev., 101 (Sept/Oct 1974). Taylor, R. L., Herrmann, D. B., Kemp, A. R., Ind. Eng. Chem., 28, 1255 (1936).
Receiued for reuiew April 18,1977 Accepted November 7,1977
