The Concept of Cost/Performance
The preferred criteria for selecting appropriate interior packaging materials for any specific application is a combination of the cost of the final package and the level of performance it provides. This combination can be thought of as the overall value of the package.In general, a package will perform one or more of the following functions:
- Containment
- Convenience
- Communication
- Protection
Protection may be from spoilage, heat, cold, moisture, infestation, light, tampering, pilferage, Electrostatic Discharge (ESD), corrosion and physical damage resulting from the bumps, jolts, impacts, compression and vibrations encountered in typical distribution, shipping and handling environments. So, interior packaging materials are most often first considered on their ability to perform some required protective function. This should not be the entire basis for selection however, since all performance will come at some cost.
Over the years it has become obvious that overall value for a pack design is based on several cost factors, including (but not always limited to) the costs of:
Packaging operations of the scale described earlier (1,000 - 5,000 packs per month) probably will use a limited range of internal packaging materials, depending on the types of products being shipped and the types and levels of protective performance required. The types of performance most often considered for these materials are:
Areas of Packaging Performance
A brief description of each type of performance may help to explain why certain materials may be preferred over others.Surface Protection: These materials serve to protect finished surfaces on products which might be susceptible to scratching, denting, marring and highlighting during warehousing and distribution. Products with finished, polished or painted metal or wood surfaces most often will require a surface protection material to ensure that these surfaces arrive undamaged at the ultimate user. Materials used for such purposes must be clean, non-abrasive, and non-reactive. Often, they must also "breathe" in order for surfaces to finish curing in the final package.
Wrapping/Interleaving: When several items are shipped in the same shipping container, they must often be individually wrapped or interleaved to prevent internal collisions and impacts during shipment. Often these types of contents can more easily be protected if they are consolidated into a single unit through wrapping and interleaving with the appropriate materials. The preferred materials for these applications must be thin enough not to add inordinate bulk to the contents while sufficiently resilient to ensure the items being wrapped are protected from each other during shipping and distribution.
Void Fill: In many packaging areas only a limited number of corrugated box sizes can be stocked. Therefore, it is not unusual that the contents will not fill the internal volume of the box being used. The excess space in the container in these instances can create problems in shipment. We often use void fill materials to compensate for any potentially damaging effects of these voids while also insuring the maintenance of the original packaging array throughout shipment. Void fill materials should be economical, "bulky," easy to use and resilient enough to maintain their bulk throughout the shipping cycle. If void fill materials compress and do not recover during impacts, vibrations or compression, then the void originally occupied will be created again in the pack.
Blocking & Bracing: There are times when the objective of a package assembly will be simply to keep the product inside in a specific position within the package. Cushioning may not be an issue (the product being rugged and not easily damaged from shock). Most often, this packaging function deals with large, heavy, rugged items which may be packaged in crates or on pallets.
Cushioning: Many items will be damaged if they are subjected to rough handling or transit vibrations without additional protection. Such fragile (and semi- fragile) products will require "cushioning." Materials which cushion will support the product within the pack and then deflect or deform under dynamic impact in a controlled manner, reducing the level of shock felt by the product to safe levels. Most effective cushioning forms will then recover after such an impact in order to maintain this ability for subsequent impact events. Cushioning is often designed and fabricated (or molded) for specific products but for the operations described here, more often the cushioning materials preferred are those which have broad ranges of potential usage including wraps and foam- in-place.
Specialty: Many types of products will require special types of protection. Products which might rust or corrode, which are sensitive to light, dust or electrical discharge, which must be kept frozen or be kept from freezing, will require materials providing these types of protection within the package. The features of concern for the interior packaging materials are relating to surface protection, wrapping/interleaving, void fill and cushioning.
Materials
The chart included breaks down the common interior packaging materials most often encountered in a typical packaging area. A brief description of the categories might help in understanding the materials and their uses. The list is by no means complete – there are materials which are not included. However, those listed are by far the most commonly in use in today’s packaging operations.Paper: As an interior packaging material, paper has been in use for longer than any other of the materials listed here. As printed or unprinted news, kraft, bogus, tissue and wadding (multiple layers of kraft and/or tissue bonded together into a sheet or roll of material), paper has been wrapped, stuffed, wadded, crammed and jammed into packages to protect products, block them in place, fill voids and to even absorb any liquids which might be present should the packaged product be a bottle of one fluid or another. More recently, paper products which are processed through machines which crumple, crunch or slit and expand the sheets to convert the flat sheet into more bulky forms for void fill and cushioning have been introduced.
Air Cellular: The first and perhaps most recognizable of the air cellular materials are Sealed Air’s AirCap® and Bubble Wrap® air cellular cushioning materials. Available in rolls (both plain and perforated for ease of use), sheets and bags, these high efficiency materials have been used in packaging operations for over 40 years. Available in different bubble heights, air cellular materials can be used for all the protective functions listed on the chart quite effectively. They can also be laminated to various substrates to achieve other performance attributes such as insulation, cohesion and adhesion. Most recently, a form of these materials has been introduced which can be inflated on site, on demand, eliminating the issues associated with storing and handling these lightweight, bulk y products prior to their use. The Sealed Air® Inflatable Bubble Wrap® system is a unique, efficient new approach to interior packaging problems.
Inflatable Void Fill: This class of materials consists of pouches of air created on site, on demand for void fill applications. Using typically low density polyethylene (LDPE) or high density polyethylene (HDPE) films, various size pouches can be created on different types of equipment available from a number of manufacturers. These materials provide high efficiency, low density, low cost void fill for products which are considered light to moderately heavy (less than 25 pounds). Because of the broad range of providers, the equipment and the types of films used, there can be significant differences in products from different suppliers.
Loose Fill: Peanuts, discs, donuts, tubes, sausages all have been used to describe the various forms in which these materials may be provided. Although there may be some differences in how these various forms flow, compress or stabilize in the package, the major types of loose fills found today are based on the materials from which they are made. The first and most common types are those made from expanded polystyrene foam (EPS). These are extremely low density (nominally 0.3 pounds per cubic foot) and have been in common use as void fill for some time.
Several years ago, a new class of these materials was commercialized, made from starch (typically corn, wheat or oats). Being "bio-based" materials, these products are often promoted as being soluble in water and biodegradable. Heavier than their EPS counterparts (nominally 1 pound per cubic foot density), starch based loose fills have become more common in many void fill operations.
Foam-in-Place: These are polyurethane foams created by combining two chemical components on site, on demand. Dispensed in a liquid form, the combined components react, creating a foam in the package, around the item being protected. Highly efficient cushioning, void fill and blocking and bracing formulations are provided for many high performance applications. New approaches feature operations in which the components are dispensed into a bag in a foam-in-bag process and the bag is then placed into the pack where the foaming reaction then takes place. Foam-in-bag packaging also provides more accurate control over the amount of foam used in each application. A new offshoot of this approach is Instapak Quick® foam-in-bag from Sealed Air Corporation. Here, the two components are provided already in the bag. The operator simply activates the reaction in the bag without the need of any equipment other than a warming device used to keep the Quick™ bags at the optimal reaction temperature.
Polyethylene and Polypropylene Foams: These are two different closed-cell foam materials, commonly used in roll or sheet form. Note that they are both also available in plank and molded forms, but for the operations described for this article, these are most often found on rolls, as perforated rolls or as sheets for wrapping, interleaving and cushioning. Made from different kinds of polymers (polyethylene and polypropylene), these materials are somewhat similar in appearance, but will have different performance characteristics as is demonstrated in the accompanying chart of materials.
With the number of different materials available for surface protection, wrapping and interleaving, void fill, blocking and bracing and cushioning, most small- to-medium packaging operations will include perhaps two or three different options, particularly when the products being packaged are not all identical and all the packages going out the back door are not the same. Selection of the most effective interior packaging materials to use (alone or in combination with others) will typically require the consideration of both the performance requirements of the application along with the total costs involved with the use of the various candidate materials. Optimizing the value of the total package based on these criteria will most often result in successful shipments along with controlled packaging costs for both the interior packaging materials and the outer shipping container.
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