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A Communication from the PLACE Div. of TAPPI

Providing practical information to the converting and packaging industries…

Lidding Applications For Peelable Seal Roll Applied Coatings

by Thomas R. Mueller, Rohm and Haas Company

Application: Although extrudable resins and coextruded films have had a large impact on flexible packaging structures, roll applied coatings still offer a good fit in a wide variety of applications. This paper explores the different chemistries available, applications, and properties currently used to provide peelable seals in lidding and easy-open applications.

A heat seal coating is an adhesive applied to a flexible substrate as a non-blocking layer for activation later with heat and pressure to provide a peelable adhesive bond to another rigid or flexible substrate. Important considerations in this application are package substrates, the substrate for coating, product type and its packaging conditions, product resistance requirements, peel strength, hot tack requirements, peel style, blocking resistance, and storage conditions. Depending on these, several different types of roll applied heat seal coatings are available in solvent and water borne chemistries. All the chemistries discussed in most cases have a wide range of conformance to FDA requirements for various regulations covering direct food contact.

The choice of heat seal coatings depends not only on the factors previously listed but also on the converting equipment and the technical expertise of the converter. This paper provides a discussion of the alternatives available to the converting industry. All the heat seal coatings discussed will contain many of the following components: resins; tackifiers and additives; lubricants, waxes, and slip modifiers; anti-oxidants and fillers; antiblocking and heat stabilizing agents; solvents and dilients; and water dispersants, pH control materials, defoamers, and surfactants.

Aqueous coatings are dispersions based on ethylene vinyl acetate, ethylene methyl acrylate, and ethylene acrylic acid chemistries. They are formulated resin dispersions with a broad range of application use. Because they use water, they will freeze and can exhibit drying and foaming issues. Their appearance is usually translucent to opaque, and they will generally have lower water and humidity resistance. Their advantages nevertheless far outweigh these concerns.

As the paper shows, the chemistries available have use for a wide range of substrates, filling conditions, and cup stocks. Their wide range of FDA compliance gives the converter a wide range of choices depending on application and drying capabilities. While coextrusions have made significant inroads in the peelable lidding markets, significant end uses still exist for the various peelable lidding solutions.

Effect Of Chlorine Dioxide Sachets And Modified Atmosphere Packaging On Quality Of Fresh Chicken Breasts

by Kay Cooksey, Clemson University

Surface growth of microorganisms is a leading cause of food spoilage. Natural microflora can eventually spoil a food or surfaces can be contaminated by handling during processing and packaging. For many years, foods have undergone treatment with antimicrobial agents. Packaging materials may also provide the same benefits using similar or different additives. A package system that incorporates an antimicrobial agent could significantly increase the shelf life and improve the quality of many foods. The use of such packaging systems is not a "cover-up" for poor quality control. It can serve as an additional protective measure to help ensure safe and high quality foods.

A variety of methods are useful to incorporate antimicrobial agents into food packaging systems. They are direct or indirect. Indirect incorporation of an antimicrobial agent can include insertion of sachets/pads that are attached to the package’s interior or loosely enclosed within it. Examples include oxygen absorbers, moisture absorbers, and ethanol vapor emitters. Direct incorporation involves blending the agent into the polymer melt or coating the surface of a film using a polymer that acts as a carrier for the antimicrobial agent.

The objectives of this study were to observe the effects of fast and slow releasing chlorine dioxide sachets combined with 100% nitrogen or 75% nitrogen and 25% carbon dioxide modified atmosphere package on Salmonella typhimurium during refrigerated storage. The effects of these treatments on color, appearance, odor, and total plate count were also measured.

Evaluation Of Low Voltage Electron Beam Processors Using Thin Film Dosimetry Techniques

by Im Rangwalla, Energy Sciences, Inc.

Radiation induced in-situ polymerization reactions offer significant advantages over conventional thermal processes. The biggest advantage is use of 100% reactive and compliant chemistry with no thermal drying. Since the introduction of electron beam equipment in the early 1960s, polymer chemists were intrigued by the ability of the electrons to initiate free-radical polymerization reaction without the addition of any photo-initiators or photosensitizers. Immediate applications were sought in packaging using the free radical initiated chemistries since electron processing offered high speed curing. Food packaging was particularly interesting because electron beam processing offered the following advantages:

  • High degree of conversion with low migration.
  • Absence of photo-initiator or other additives such as peroxides.
  • Good quality control through NIST traceable dosimetry techniques and closed loop control electronics.
Suppose an adhesive chemist develops an EB laminating adhesive to laminate two dissimilar plastic films and uses a dose of 3 Mrads for an application that needs FDA compliance. To obtain this, a migration study is done on pilot EB equipment using the same dose of 3 Mrads. These laminates then undergo extraction work using appropriate food stimulants. After obtaining FDA compliance, the product is commercial and is manufactured using commercial EB equipment with the same 3 Mrads dose to cure the adhesive. The question is how to relate the 3 Mrads dose to cure the adhesive using 3 different electron beam sources: laboratory EB equipment, pilot EB equipment, and finally commercial EB equipment. An additional question remains regarding how to ensure that the EB equipment is delivering the required 3 Mrad dose on a regular basis.

The answer to these questions is thin film dosimetry techniques. Using thin film dosimetry, one can measure the entire output of the electron beam processors with good accuracy providing required quality control both during development and ongoing processing.

The use of a commercial radiochromic, thin film nylon dosimeter is a relatively accurate method of measuring the performance characteristics of low voltage EB processors. Challenges do remain in maintaining the accuracy and the handling of 8-micron nylon films. Development work is continuing with the manufacturers of thin film dosimeter to reduce these challenges and improve accuracy.

Analysis Of New Flame Treatment Technology For Surface Modification And Adhesion Promotion

by David A. Markgraf, Enercon Industries Corp.

Surface treatment technologies commonly find use to enhance the adhesion potential of basic flexible packaging substrates for the application of performance adhesives, coatings and inks. This paper shows the relationship between ribbon burner flame treatment technology and enhanced velocity (EV) port burner technology to the degree of surface modification for adhesion promotion. Results showed that packages subjected to flame treatment before coating and printing performed significantly better and gave substantial benefits. The subsequent measurement of dyne levels, peel adhesion values, and longevity tests following separate ribbon burner and drilled port flame surface treatments of various flexible packaging materials indicated definable differences between flame burner technologies and their effectiveness.

Flame treatment was initially developed in the 1950s to improve the surface adhesion properties of polyolefin films. Flame treatment typically creates fixed levels of oxidized species on the surface of films with the formation of hydroxyl, carboxyl, and carbonyl functionalities. Treatment or oxidation depths vary by substrate as does the generation of low molecular weight organic material at the surface. Flame plasmas have an electron density of approximately 108/cm and electron energies of 0.5 eV. Surface exposure to flame treatment directly modifies electron distributions and densities of polyolefin molecules resulting in polarization at the polymer surface up to several nanometers.

This study provides an examination focused on flame burner technologies. The paper begins with an overview of existing burner technologies followed by an examination of enhanced velocity (EV) port burner technology. Next is an experimental review of ribbon and EV port burner performance relative to surface tension, wettability, and overall treatment effectiveness. Comparing these performance characteristics allows identification of the most effective burner technology.

The surface energy of the test substrates of OPP film and LDPE-coated paperboard increased by an average of 4.6% and 4.3%, respectively, at a fixed speed using the EV burner compared with the ribbon burner. When power levels remained constant, surface energy of these same substrates increased by an average of 9.7% and 7.2%, respectively, over ribbon burner results with the EV burner. No discernable difference in treatment longevity on either substrate was evident between the burner types. Peel adhesion tests on OPP film employing each burner at the same trial speed and power level conditions indicated the potential for significantly improved peel adhesion using the EV burner design.

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.

Telephone inquiries are welcome at the TAPPI Service Line by calling 800/332-8686 in the United States, 800/446-9431 in Canada, or +1-770-446-1400 in other countries. Send FAX to 1-770-446-6947. Address mail to TAPPI, Box 105113, Atlanta, GA, 30348-5113.

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