A Communication from the PLACE div. of TAPPI

Providing practical information to the converting and packaging industries

Executive Summary
Multidimensional Gas Chromatography-Olfactometry Based Investigations Of Odor Quality Issues In Packaging And Consumer Products

by Donald W. Wright, Microanalytics (a MOCON Company), et al.

Application: Many important factors such as packaging appearance, product presentation, and sensory impact influence the commercial success of packaged consumer products. Consumer perception of aroma quality is very much context driven.

A "flora"’ aroma character perceived as wonderful in a garden or fragrance environment is an unacceptable taint in bottled drinking water. Alternately, the unpleasant odor of butyric acid perceived as a major malodor contributor in high-density livestock environments is a primary aroma and flavor contributor to Parmesan cheese. Unfortunately, malodor characterization is a very demanding analytical challenge. This is due to the fact that aroma or odor critical components are typically present at very trace levels in a complex matrix of odor insignificant volatiles.

The typical response to crisis-driven malodor issues is to extract or concentrate from headspace the volatile compounds, separate them by GC, identify them by MS, and speculate which of many compounds might cause the odor. Experience has shown that a much more effective approach to these investigations is GC-olfactometry based. With GC-O technologies, odor profile ranking studies are carried out relative to the in-situ headspace volatiles collections taken directly from the product under investigation. This GC-olfactometry approach begins with the development of a detailed odorant ranking profile for a sensory graded "worst" case sample. Equivalent comparative odorant ranking profile analyses for equivalent sensory graded "best" case samples will indicate which "potential" odorants account for the odor quality defect .

The applications presented in this paper illustrate that an integrated MDGC-MS-Olfactometry system can be a powerful tool for maximizing the efficiency of odor and aroma investigations. Illustrated odor quality degradation processes can include odorant cross-contamination between packaging and product, critical aroma volatile loss through scalping by packaging wall surfaces, and oxidation based odor quality degradation. As the application series shows, oxidation based odor quality degradation can occur through more indirect and complex processes compared with the more commonly expected through-wall oxygen transmission. When considering aroma/odor/ flavor quality of any packaged product, package selection is essential in relation to the aroma character defining components associated with the particular product being packaged. This is also true for bottled drinking water where the defining character is no odor. Any odor deviation from this absence of odor character—whether good or bad—is an odor quality taint.


Executive Summary
Rheological Indicators To Predict The Extrusion Coating Performance Of LDPE

by Per-Ake Clevenhag and Claes Oveby, Tetra Pak Carton Ambient AB

Application: A new rheological test method allows prediction of processing performance of LDPE for extrusion coating.

LDPE from high-pressure autoclave reactors for extrusion coating with a melt flow rate (MFR) range from 7 to 9 g/10 min with a density of 917 to 920 kg/m3 has for many years been a uniform commodity. As evolution goes toward faster coating lines, differences in processing performance between various LDPE grades have occurred. Various LDPE grades behave differently in the coating process due to different rheological properties.

Thirteen grades of autoclave LDPE from different suppliers were tested in two pilot extrusion coating lines on three different occasions. All grades had MFR between 7 and 9 g/10 min and densities of 918 to 920 kg/m3. The melt temperature was monitored to 295–305°C by means of an infrared camera. In principle, the methodology was as follows. Extruder screw rpm was set to give 10 g/m2 at 150 m/min to obtain stable processing conditions. The line speed was then increased in steps of 50 m/min until the web broke. The line speed at which the web broke (draw-down speed) and the neck-in were reported. This was made in duplicate for each grade of LDPE.

The parameters MFR and density give very limited information on the processing performance of a product. A resource demanding test run of LDPE material in a pilot or production coating line is often necessary to determine processability. Extrusion coating performance can be conveniently and considerably less resource demanding when determined and predicted by the rheological method described in this paper.


Executive Summary
Shedding A New Light On Corona-Treated Aluminum Foil

by Gunter Schubert, Hydro Aluminium Deutschland GmbH, and Otto Plassmann, BP Koln Gmbh

In flexible packaging, extrusion coating and extrusion lamination for converting aluminium foil is almost omnipresent. The benefit of corona treatment of foil is not obvious because of the high surface tension of foil compared with other substrates. This presentation brings a better understanding of the adhesion of extrusion coatings on aluminium foil by comparing extrusion coating untreated and corona treated foil.

As indicated by surface tension measurements, corona treatment works more efficiently at a higher line speed. A threshold intensity occurs where surface tension of a hard temper foil starts increasing also. For a 9% EAA tie resin on hard and soft foil, reasonable adhesion occurs with or without treatment. On soft foil at 100m/min., initial adhesion increases with rising corona doses. Since adhesion climbs during wet storage, smaller differences occurred with longer wet storage. Altogether, corona treatment ensures appropriate and robust adhesion on soft or hard aluminium foil even for a low methacrylic acid copolymer.

For a closer look at the differences in de-bonding failure mechanism between hard and soft foil, high and low methacrylic acid, and changes during wet storage, peel surfaces underwent examination by IR-ATR. Interfaces were only partly accessible and results were fragmentary. Comparisons were not systematic, but some results are interesting. When using 1.2% EMAA tie resin, higher treatment levels lead to a higher amount of polymer residue on the aluminium face. Adhesion levels correspond with the amount of tie layer residue on the aluminium. Corona-treated hard foil and non-treated soft foil lead to almost the same adhesion with 9% EAA and carry the same amount of residual hydrocarbon on the metal foil.

Beyond a threshold intensity, corona-treatment can increase the surface tension of hard foil up to the level of highly wettable, annealed foil. At higher line-speed, corona-treatment is more efficient than at lower speed. Nine percent EAA-tie resins adhere adequately on corona-treated and on non-treated hard foil. Corona activation allows 1.2% EMAA resins to adhere on hard foil as well. The initial adhesion of annealed foil improves with corona treatment especially for low acid copolymers. Under low and high acid content tie layers, the oxide layer on aluminium foil grows slightly and does not influence adhesion.


Executive Summary
New EVOH Resins For Flexible Packaging

by Robert B. Armstrong, EVAL Americas (USA)

The high barrier packaging market in the United States continues to experience strong sustained growth. Ethylene vinyl alcohol copolymer (EVOH) barrier resin finds frequent use in new applications for high barrier flexible packaging because of its outstanding gas barrier properties, excellent organoleptic properties, and easy processability on a wide range of conventional coextrusion processing equipment.

Coextrusion coating and laminating has evolved into a technologically sophisticated process. Today, coextrusion coating and laminating offers high productivity, low cost, and diverse function. Progress has come from response to consumer demands for greater convenience, variety, and improved product quality. Developments to improve the original coextrusion coating die technology include automatic profile control dies, multi-manifold feed blocks, gravimetric feed systems, and computerized process control systems.

A study of three different EVOH resins with varying mol percentages and melt indexes illustrated the effect that selected ethylene levels and melt index have on processability. Items studied included extrusion output, neck-in characteristics, thickness distribution, thickness limitations, and process stability of the resins.

Barrier material choices for flexible packaging continue to expand. EVOH offers flexibility, transparency, easy processability, and pinhole resistance in addition to extremely high barrier to gases, flavors, and aromas. Use of EVOH in multilayer packaging can preserve food quality and flavor in convenient and attractive transparent packaging. A wider range than ever before of EVOH resins designed for coextrusion coating and laminating process is now available. These materials that incorporate improvements in thermal stability and processability allow package designers and processors to use EVOH effectively and efficiently in flexible packaging and add value to their products and applications.



For information about the PLACE Division of TAPPI, access the TAPPI web page at tappi.org. To obtain the complete papers whose expanded summaries appear in this section, go to the TAPPI web site at tappi.org., then click on "the PLACE" in the section designated Journals.


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