Odor Barrier Characterization of Polymer Materials MOCON 2008 Internet Seminar Series June 11, 2008
Background Information A company needs to contain the odor generated from a waste process.
Background Information The company has oxygen transmission rate equipment “in house”. They want to know if this equipment can be used to screen potential barrier materials for their odor barrier properties. The company requested a comparative study between different polymer film types.
Background Information The Goal: Compare odor barrier with oxygen barrier to determine if oxygen barrier property can be used for odor barrier prediction.
What’s Smelly? Chemical and chemical reactions are responsible for odors. Which chemicals does one choose to represent a particular odor? Sensory testing – can help choose a consensus of the odor (i.e. good vs. bad) and descriptors. GC testing can quantify the chemicals comprising the odor.
What’s Smelly? Microanalytics performed an odor characterization study of the “Smelly” material. They utilized a Multi- dimensional Gas Chromatograph with FID / PID / Olfactory / MS Detectors
AromaTrax Approach: An Integrated Analytical Approach to Studying Flavor/Aroma Interactions Instrumentation / Techniques: Simultaneous Olfactory and Mass Spec Detection Multidimensional Gas Chromatography - Dean Switch.Heart Cutting (Fractions), Cryogenic Trapping, Back Flushing Inlet sampling techniques to maximize concentrations of aroma significant compounds. Methods: Aroma Standard Profile SPME Aroma Extract Dilution Analysis (AEDA) Headspace Aroma Dilution Analysis (HADA) Combining human sense with instruments and methods.
FID PID Sniff Port Mass Spectrometer Open Split Interface AromaTrax Software Chemstation (Agilent) MultiTrax Software Injection system column 1column 2 Agilent 6890 based dual column MDGC Windows NT AromaTrax Model 2100 Multidimensional GC/O-MS
col 1 col 2 FID PID Inj VentHCV MS cryompr sniff port GC oven pre-column analytical Optimized for trace aroma/odor analysis Permits: Heartcutting, cryofocusing, and backflushing to ferret out aroma components hidden in non-aroma components. Columns of different polarity Open Split Interface AromaTrax Model 2100 Multidimensional GC/O-MS
MDGC Methodology Some portions of separations may not resolve well due to complexity or some portions may mask important odor components. Dairy Grade Polyethylene Headspace Heart-cut Separations Intense off-odor Heart Cutting: -Permits better resolution of trace or masked components.. - To resolve all components in a complex mixture by passing a portion of column effluent to a second column using flow switching -Backflushing the uninteresting volatiles to vent, permitting the heart cut portion to resolve by itself in second column. Back Flushing Getting rid of uninteresting volatiles No bake out And Cryotrapping Reduce diffusional broadening. Focus sample
Heartcut Region ANALYTICAL Column - PID of Heartcut PRECOLUMN-FID 2-AP -Popcorn aroma in rice MDGC Separation of 2-AP Rice Volatiles Continued - “Needle in the Haystack” MDGC Heartcut permits increase resolution for the MSD and other Detectors
What’s Smelly? Over 100 different aroma chemicals were identified from the samples. d- limonene (terpene / essential oil family) was a prominent chemical in all of the tested samples. Toluene (aromatic hydrocarbon) was also found in the aroma profile.
Material Selection Barrier NamePolymer Family OPPPoly(olefins) PVDC CopolymerPoly(vinyls) OPP with barrier coatingMulti-layered Structure Nylon-6Poly(amides) PETPoly(esters)
Odor Barrier Study Analysis Temp: 23C Using the saturated vapor pressure of limonene and toluene at 23C Toluene: (25.59mmHg); Limonene: (1.84 mmHg)
Material Name Transmission Rate (Normalized) d – Limonene (gm*mil)/(m 2 -day) Toluene (gm*mil)/(m 2 -day) Oxygen (cc*mil)/(m 2 -day) OPP5.847501200 PVDC Copolymer0.03816228 OPP with barrier coating 1.67212.0 Nylon-68.2 x 10 -5 3.8 x 10 -4 4242 PET1.4 x 10 -4 3.6 x 10 -4 5656
Odor Barrier / Oxygen Barrier Comparison Material Name Transmission Rate (Normalized) d – Limonene (gm*mil)/(m 2 -day) Toluene (gm*mil)/(m 2 -day) Oxygen (cc*mil)/(m 2 -day) OPP5.847501200 PVDC Copolymer0.03816228 OPP with barrier coating 1.67212.0 Nylon-68.2 x 10 -5 3.8 x 10 -4 4242 PET1.4 x 10 -4 3.6 x 10 -4 5656
Odor Barrier / Oxygen Barrier Comparison Material Name Material Ranking (1 = best, 5 = worst) d - LimoneneTolueneOxygen OPP555 PVDC Copolymer342 OPP with barrier coating 431 Nylon-6123 PET214
Conclusions Oxygen transmission rate testing of different polymer families could not accurately predict or rank the organic barrier properties of the same films. Material Name Transmission Rate (Normalized) d – Limonene (gm*mil)/(m 2 -day) Toluene (gm*mil)/(m 2 -day) Oxygen (cc*mil)/(m 2 -day) PVDC Copolymer0.03816228 OPP with barrier coating 1.67212.0 Nylon-68.2 x 10 -5 3.8 x 10 -4 4242 PET1.4 x 10 -4 3.6 x 10 -4 5656
Conclusions There is no “universal” conversion factor from oxygen results to organic results Material Name Organic to Oxygen Ratio d – Limonene TR Oxygen TR Toluene TR Oxygen TR OPP0.00480.63 PVDC Copolymer0.00145.79 OPP w/ coating0.8410.5 Nylon-61.95 x 10 -6 9.05 x 10 -6 PET2.50 x 10 -6 6.4 x 10 -6 Average Ratio0.173.4 Standard Deviation0.374.7
Conclusions For the same polymer material, different organics can yield different and unpredictable results. This is largely due to polymer / permeant interactions. Material Name d – Limonene (gm*mil)/(m 2 -day) Toluene (gm*mil)/(m 2 -day) PVDC Copolymer0.038162 OPP with barrier coating 1.6721
Conclusions In most cases, the best way to determine whether a material is a good organic (aroma or odor) barrier, is to: First : Determine which organics are the key players. Second: Test the material with the proper permeant.
Even though oxygen transmission testing was a poor tool for ranking the overall organic barrier for differing materials, it may prove meaningful to use an oxygen / aroma correlation when comparing barrier properties of like polymers of different thickness, grades or added coatings. Recommendation for a Future Study