Cushioning

 Material Selection

This section will provide basic information about some of the more common cushioning materials in use today. This section is not intended as a guide to approved cushioning materials, but as a basis for beginning designs for the new Packaging Engineer. The materials listed here represent a small portion of those available.

New cushioning materials are being developed every year. In many cases these materials offer improved cushioning properties over existing materials. For this reason Packaging Engineers should always evaluate new materials carefully and use them whenever they offer better properties.

Cushioning materials in general can be broken into non-resilient and resilient types.

Resiliency is the ability to absorb and dissipate energy without significant permanent deformation. A "resilient" foam absorbs the impact energy without breaking or deforming so can be reused multiple times and still effectively cushion against impact forces.

A non-resilient cushion will "break" or otherwise deform during the cushioning process, limiting the number of impacts that can be effectively cushioned. This damage may occur internally and therefore be difficult to detect. Used non-resilient foams should not be used with fragile products for this reason.

Some foams can behave as a resilient foam at low static loadings and a non-resilient foam at higher static loadings (and all foams are "resilient" if the force of impact is very small).

1.1 Expanded Polystyrene

EPS is a semi-rigid closed cell plastic foam that is manufactured by expanding a polystyrene bead using steam and a blowing agent. Generally white in color, EPS is characterized by its very small bead structure and smooth surface. Anti-Static treated EPS is generally pink in color. EPS is a thermoplastic.

Advantages of EPS include low material cost and light weight. Being a molded foam, complex 3-dimensional shapes can be produced. Many vendors worldwide can produce EPS cushions.

Disadvantages to EPS include non-resiliency (absorbs impact by breaking), high tooling cost, long design and tooling lead times, and it cannot effectively cushion below 40 G’s.

EPS is best used with a rugged product (fragility > 40 G’s) and high product volumes (to offset the higher mold costs). Densities are available in 1.0 pcf to 9 pcf (EPS above 2.5 pcf is not generally used for cushioning purposes, but useful for blocking and bracing heavy, rugged products).

Environment:
EPS is readily recyclable in most areas. It generally is not reusable when used as a cushion, but lower static loadings may allow reuse.

2.1 Expanded Polyethylene

EPE is a semi-rigid closed cell plastic foam manufactured in a similar fashion to EPS (see above section). Generally white in color, EPE is characterized by a medium sized (3-8 mm) smooth bead structure and a "spongy" resilient texture. Anti-Static EPE is also generally pink in appearance. EPE is a thermoplastic.

Advantages to EPE include excellent resiliency (able to absorb impact without damage), ability to design complex shapes into molded cushion, and excellent cushioning and vibration damping properties.

Disadvantages to EPE are high cost, long (2-3 months) tool lead-time, static generator (anti-static available), not all vendors can mold in EPE.

EPE is best used for fragile (fragility < 40 G’s) products and high product volumes (to offset the higher mold costs). EPE is capable of effectively cushioning products with fragility’s as low as 20-25 G’s. Densities are available in 1.0 pcf to 2.5 pcf.

Environment:
EPE is an excellent choice when reusability is desired. EPE is generally recyclable along with the normal PE (Ethafoam TM) recycling stream.

EPP is a semi-rigid closed cell plastic foam manufactured in a similar fashion to EPS (see EPS section). Generally white in color, EPP is characterized by a medium-to-large sized (5-10 mm) semi-smooth bead structure and a "spongy" resilient texture. Anti-Static EPP is also generally pink in appearance. EPP is a thermoplastic.

Advantages to EPP include excellent resiliency (able to absorb impact without damage), ability to design complex shapes into the molded cushion, and excellent cushioning and vibration damping properties.

Disadvantages of EPP are high material cost, long (2-3 months) tool lead-time, static generator (anti-static available), and not all vendors can mold in EPP.

EPP is best used for fragile (fragility < 40 G’s) products and high product volumes (to offset the higher mold costs). EPP is capable of effectively cushioning products with fragility’s as low as 20-25 G’s. Densities are available in 1.0 pcf to 2.5 pcf.

Environment:
EPP is an excellent choice when reusability is desired. EPP is not recyclable in all areas yet, but the capability is rapidly spreading.

Many of the expanded foams start with tiny resin pellets. If different types of resin pellets are mixed before expansion and steaming in the mold, a co-polymer foam is the result. Co-polymer foams are a composite of both foams, with some of the benefits of each type of foam used. Generally a cheap, mediocre foam will be mixed with an expensive, excellent foam. The result is somewhere in between in both cost and performance. Cushions are manufactured in molds similar to other expanded foams.

Arcel ® , a mixture of EPS and EPE, is one of the most common types of co-polymers used for packaging cushioning.

Advantages depend on the foams and percentage contents used.

Disadvantages include difficulty in properly identifying the material.

Environment:
Co-polymers are generally not recyclable, although some types can be recycled along with the major content foam (EPE in the case of Arcel ® ).

3.1 Polyethylene Foam (commonly known as Ethafoam ® )

PE is coarse, open celled foam that is extruded by resin manufacturers. PE buns (8’ x 16’ x 6-8’) are shipped to vendors, who slice, die-cut, and glue or thermalset the foam. PE is also widely available in sheet rolls (1/8", 1/4", 1", and 2" thicknesses). Parts designed using theses thicknesses will be less expensive than other thicknesses since a labor step is saved. PE is generally white colored (anti static variety is pink) with tiny (1-2 mm) open cells. PE can be rough (if cut) or smooth (if the surface was originally on the outside of the bun). PE is a thermoplastic.

Advantages to PE include good resiliency, high static load capabilities, unaffected by most chemicals, and good cushioning and vibration damping characteristics.

Disadvantages to PE include relatively high cost, may be abrasive to delicate surfaces, and may use CFC’s or ODS’s during manufacture (many brands currently do not).

PE is best used for fragile (20-50 G’s) products when volumes are low or high (due to low die costs), simple shapes are involved, and medium to high static loadings are needed in the cushion design. Densities are available in 1.7 pcf, 2.0-2.2 pcf, 4 pcf and above. PE densities above 2.2 are not generally used for cushioning, although PE of such densities could be used for blocking and bracing large, rugged products.

Environment:
PE cushions can be reused many times if designed correctly. PE is readily recyclable in most areas.

Known commonly as "Strandfoam ®" , extruded polyethylene foam is made by extruding the polyethylene through a sieve-like pattern. The result looks like many tiny foam tubes stacked on top of one another. A grain direction (direction of extrusion) and cross-grain direction exist with extruded polyethylene.

Polylam foam is layers of polyethylene foam bonded together using hear or glue. Characteristics are very similar to polyethylene (PE) foam (see PE section).

Rubberized hair is commonly locked into older packaging specifications (especially government) as it was very common cushioning material. It comes in 6 grades, distinguished by density and stiffness. Rubberized hair appears as thin rubber coated strands (generally black) compressed into a dense mat. Rubberized hair mats can be cut with scissors. Performance is no better than materials available today, and the cost is generally higher when compared to today’s materials.

Advantages to rubberized hair include good cushioning and vibration damping.

Disadvantages include high cost, high weight, may become infested with vermin, limited fabrication possibilities, and difficult sourcing and storage.

Rubberized hair should not be used unless absolutely required to meet a packaging specification. Even then it would be far better to work with the customer to find an acceptable alternative.

Environment:
Rubberized hair is not recyclable. The higher grades (densities) can be reused. It can be considered resilient at low static loadings.

4.1 Polyurethane Ether Foam

PU is an open cell foam manufactured by mixing isocyanates and polyols and allowing the mixture to expand into a slab or bun. Both flexible and semi-rigid PU foams are available, but the flexible, "spongy" types are most commonly used for package cushioning. PU is available in a wide range of densities (.3 pcf to 4 pcf most commonly used for cushioning) and colors. PU foam is shipped in buns from resin manufacturers to fabricators. Fabricators (your vendor most likely) will die-cut, hot wire, and saw the foam bun into shapes which are then glued together to form cushions. PU foam is often "convoluted", or cut in a special way to produce a wavy, bumpy surface.

Advantages of PU include quick tooling lead-times (2-4 weeks), low tooling costs, excellent cushioning and vibration damping, and it can be used to cushion very delicate products.

Disadvantages to PU include high material cost, PU foam is best used when short lead times are available, product volumes are low, and/or product fragility is low. PU foam is capable of protecting products with fragilities as low as 15 G’s. Convoluted PU foam in low densities can cushion very light, very fragile products.

Environment:
The glue most often used to bond PU foam to PU foam contains a solvent 1,1,1 TriChloroEthane (also known as Methyl Chloroform) which is listed in the Clear Air Act as an ozone depleting substance. Substitute solvents are available but are difficult to locate or involve longer set times. For this reason, glued PU foam cushions should be considered environmentally poor unless replacement solvents are used. PU foam is not recyclable currently, but can often be reused when ground up as carpet underlayment. PU foam can be reused if the static loads are low, but generally should not be reused with heavy products as permanent deformation can occur. PU foam is a thermoset plastic.

Polyurethane ester foam is rapidly fading from use as a package cushioning material. Polyurethane ester foam shares most of the characteristics of polyurethane ether foam while being higher in material cost.

Refer to polyurethane ether foam.

5.1 Foam-In-Place

NOTE: HP does not recommend use of this product.

Foam-in-place is a polyurethane expanding foam made on site by mixing two liquid chemicals. The expansion ratio of finished volume to component liquids can be as much as 100 to 1, therefore FIP can result in drastic part storage space reductions compared to conventional cushioning materials. The chemicals used in FIP can be hazardous to some people’s health, therefore the use of this material must be carefully evaluated.

When expanded, FIP generally appears as a light brown colored smooth skinned foam. The foam may be irregular in places where expansion was either greater or less than average. The foam cell structure is rigid, easily crushed at lower densities, and surfaces in contact with products will usually be bonded to a plastic film to avoid adhesion of the expanding foam to the product.

Advantages include savings in cushion material storage space, extremely versatile (1 FIP system can be used to cushion many different shapes), and provides a total encapsulation of cushioning.

Disadvantages include adverse health and safety factors, poor resiliency, cushion quality is dependent on operator skill, and environmental issues listed below.

FIP is best used for lightweight, fragile products of many shapes. Since FIP is stored in a barrel and dispensed as needed, it is particularly suitable for very low volume operations with a high product mix.

Environment:
FIP is a thermoset plastic, meaning that it cannot be recycled. Generally a plastic sheet is also bonded to the FIP cushion complicating the recycling issue. Due to FIP’s poor resiliency it also cannot be reused except in the lowest of static load situations. The cushions produced by a FIP system will be larger in volume than compared cushions made from any other cushioning material.

"Peanuts" are small pieces of materials used as dunnage material or cushioning. The most common material used is EPS. EPS peanuts are dispensed from a bag, usually overhead. Anti-static varieties are available.

Advantages to peanuts include flexibility as peanuts are dispensed according to need, low cost, and good cushioning and vibration damping qualities.

Disadvantages include lack of structure (products will settle to the bottom when vibrated), messy, a potent static electricity generator (anti-static variety available), and quality depends on operator.

EPS peanuts are best used as a dunnaging material (filling in void spaces). The lack of structure generally means EPS peanuts are not suitable for cushioning fragile products as they will inevitably settle to the bottom or side of the carton. EPS peanuts can be used to quickly package a variety of products into stock cartons.

Environment:
EPS peanuts can be readily reused if collected. A vacuum system can quickly clear an incoming carton of EPS peanuts while storing them for later use. See EPS section for other environmental qualities.

Peanuts made from starch and paste are also available. Such biodegradable peanuts will readily dissolve in water. Biodegradable peanuts fulfill the same basic functions as EPS peanuts, as well as the limitations due to no structure (settling).

Advantages include biodegradability (H2O), naturally low static generation, flexibility as peanuts are dispensed according to need, low cost, and good cushioning and vibration damping qualities.

Disadvantages include lack of structure (products will settle to the bottom when vibrated), messy, quality depends on operator, and susceptibility to very high relative humidity levels.

Environment:
Biodegradable peanuts are no more effective than EPS peanuts and can actually interfere with the EPS peanut recycling or reuse stream. Their high level of degradability in the presence of water is useful when recycling or when reuse is not possible.

Pela-span mold-a-pac ® is a product of Dow Chemical that uses EPS peanuts with a special water based glue dispensing system. As the EPS peanuts are dispensed, glue is sprayed on the peanuts. A plastic sheet is placed around the product and more peanuts layered on top. Once the glue sets the cushion will look like a plastic film coated rigid block of EPS peanuts. A product packaged in Pela-span mold-a-pac ® will not settle or shift like regular EPS peanuts.

Advantages include flexibility as peanuts are dispensed according to need, low cost, and very good cushioning and vibration damping qualities.

Disadvantages include manually intensive with the quality depending on the operator, slow, and requires special equipment to dispense.

Pela-span mold-a-pac ® is best used when a wide variety of products are being packaged. Several stock cartons will allow most products to be effectively cushioned without custom packaging. High volume low product mix lines should not consider Pela-span mold-a-pac ® as the low speed of packaging would bottleneck the line.

Environment:
While Pela-span mold-a-pac ® is reusable, most usage’s are one-time as the product is likely to be custom. Pela-span mold-a-pac ® is not easily recyclable as the plastic film must first be separated from the EPS peanuts.

Paper wadding is a common improvised dunnage and cushioning material. Wadded paper is generally readily available. Wadded paper is a fair cushion for products that are heavy, but adequate for most light products.

Advantages include very low material cost (sometimes even free), flexibility in packaging different products, and no set-up costs.

Disadvantages include very manually intensive, low quality appearance, and tendency to compress under load allowing products to shift excessively.

Environment:
Just as reusing newspapers or other scrap paper, wadded paper is inherently good for the environment as the paper is being diverted from the waste stream for another usage. Wadded paper can be considered reusable although few will save the material between uses, preferring to store the sheets of paper flat until needed. Most types of wadded paper are easily recycled along with newspapers.

Pad-Pack ® is a patented system that dispenses crinkled paper at a high rate of speed. The folds absorb the forces of impact in the same way tat wadded paper does. Pad-Pack ® involves far less manual labor than wadded paper since it is dispensed automatically, although it still must be carefully placed by the operator.

Advantages include very low material cost, flexibility in packaging different products, and low set-up costs.

Disadvantages include manually intensive and tendency to compress under load allowing products to shift excessively.

Environment:
Pad-Pack ® can be considered reusable although few will save the material between uses, preferring to store the sheets of paper flat until needed. Pad-Pack ® is easily recycled along with newspapers.

Excelsior is another name for wood shavings. In the past, Excelsior was a common dunnage and cushioning material. Today it is used almost exclusively for luxury products needing a traditional look (e.g. holiday wine and cheese packs). While a fair cushioning material, better materials exist today and should be used instead.

Advantages: None.

Disadvantages include manually intensive, messy, high cost, may become infested with vermin, and heavy compared to other materials.

Environment:
Excelsior is often a by product from other materials, so it is often a reused material to begin with. While reusable, Excelsior is rarely saved to be reused. Excelsior is biodegradable.

6.1 Bubble Wrap

Bubble wrap is generally made of two sheets of polyethylene film and heat sealed together. The process leaves pockets of air trapped in small bubbles. Bubble wrap is flat on one side and covered with large (appx. 25 mm) bubbles on the other side. Anti static varieties are available.

Advantages include flexibility as bubble wrap sheets are dispensed and placed as needed, light weight, and low cost.

Disadvantages include manually intensive, cushioning quality depends operator, and high loads can result in air leaking out of the bubbles reducing effectiveness.

Bubble wrap is best used in low volume, high product mix situations. Bubble wrap is also commonly used to line storage shelves to provide cushioning.

Environment:
Bubble wrap is reusable, however few will save the material to be reused. Bubble wrap is generally recyclable along with other PE films.

Similar to Pad-Pack ®, convoluted paper is manufactured by corrugators as a protective cushioning wrap. Most commonly seen lining light bulb packages, convoluted paper provides a limited amount of cushioning for very light products. Convoluted paper appears as rippled or wavy paper generally dispensed from a roll.

Advantages include low cost.

Disadvantage include limited cushioning ability.

Environment:
Convoluted paper is not generally reusable as it cushions and protects by crushing of the paper convolutions. It is, however, easily recycled along with other paper products.

PE can be extruded as a thin sheet or a bun of PE foam can be cut into thin sheets. PE sheets are widely available in 1/8", 1/4", and 1/2" thicknesses. The thinner PE wraps are typically used to protect delicate surfaces while the thicker sheets and die-cut pads can acts as a cushion. Appearance is same as PE foam, except for being in a sheet form.

Advantages include good resiliency, fair cushioning and vibration damping properties, and low material cost compared to other thicknesses of PE foam.

Disadvantages include medium cost, and may damage delicate surfaces.

Environment:
Same as PE foam.

7.1 Blow-Molded Pads

Cushion-mate/toro-pads are blow molded plastic cushions that rely on compression of the air inside a molded doughnut shaped cushion. Usually 3 cushions are attached to another piece which forms a corner block shape. When cushioning in a drop the blow molded doughnut is compressed, increasing idle air pressure inside the cushion which in turn provides greater resistance to further compression. Such a cushion is known as a "stiffening" type and typically exhibits a shock pulse as shown below.

There are two types of suspension cushions available today. The first relies on film tension, and the second relies on internal air pressure.

Tension suspension cushions consists of a urethane film stretched over a plastic, wire, or corrugated frame. When a product is placed between two of these frames and the frames brought tightly together, the two plastic films will be stretched to encapsulate the entire product. The tension in the films will provide a restoring force to prevent the product from moving away from the center position.

Internal air pressure suspension systems consists of a bag-within-a-bag. A tunnel connects the two bags on one or more ends and provides an opening to the interior of the system. A product is first placed into the system while the air pressure inside the bags are ambient. Then the space between the two bags is pressurized with air. The air pressure between the two bags compresses the inner plastic bag tightly against the product and suspending it in the center of the system. The air pressure also closes off the opening(s), securing the product in place. The air pressure in this case provides the restoring force to keep the product centered during shock loads.

Advantages for suspension cushions in general include low cushion material weight, volume until used is very small, and flexibility in packaging different sizes and shapes of products with the same system.

Disadvantages include larger overall volume when packaged compared to foams, may not be available in all regions due to patented designs, may require pressurized air, and small amounts of damage to the system generally are catastrophic leading to a complete failure of the system.

Suspension cushions are still fairly new, so should be carefully evaluated against conventional materials before use. The potential for a cheap, flexible cushioning system makes suspension cushions an attractive choice for high product mix operations.

Environment:
Tension suspension systems are generally not recyclable due to dissimilar materials being permanently connected, and may or may not be reusable depending on the materials used. Air pressure suspension cushions are generally reusable, but may not be recyclable as co-polymers are commonly used to reduce air leakage. Both types can represent a large decrease in the amount (weight and volume) of materials used to cushion a product to the same level as conventional materials.

Air cushions are similar to the internal air suspension cushions above except they are lacking the internal bag. This means that instead of placing the product inside the system, the air cushions must be placed around the product (like EPS peanuts only fewer are required).

Advantages include small volume until inflated when they become very large in volume, low cost, and flexibility in cushioning a variety of products using the same material.

Disadvantages include manually intensive, cushion quality depends on operator, pressurized air required, slow, and may allow the product to shift during transit.

Air cushions are best used for dunnage material to fill void spaces. It is not recommended that air cushions alone be used as a cushioning material for products.

Environment:
Same as for air pressure suspension cushions.

8.1 Source Reduction

The best way to help protect the environment is to use less packaging material to begin with. This reduces the pressure on our limited resources and has the added benefit of reducing overall cost.

Innovative design techniques, high-tech materials, and state of the art design and test systems can reduce the volume of materials in a package by 50% or more while maintaining cushioning performance. Bulk packaging of products (also known as postponement packaging) can result in even greater reductions in material required per product, and further cost savings.

Using source reduction will almost always result in a material cost savings, as well as help protect the environment the best.

The next best way to help protect the environment is to design packaging cushions to be reusable and to set up a program so that they are reused.

Resilient foams, whether fabricated or molded, are the best candidates for reusable materials.

The packaging in a reusable package system ideally collapses down or can be taken apart to reduce the overall volume. Molded cushions and thermoformed trays can be designed to stack, reducing overall volume as well.

Cushions as part of a reuse program should be inspected before reuse for damage, contamination, etc. Each time they are inspected they should be marked or branded. This allows a cushion to be retired after a pre-decided number of uses.

Resource America © is a company that specializes in returning packaging from the customer to an Authorized Package Producer ®. Other return systems are possible, especially when closed-loop distribution systems exist.

All package cushioning materials used today should be recyclable whenever possible. Even if a reuse program is in place, some cushions will make it into the solid waste stream. Materials that are commonly recycled are best.

Permanently attaching any two dissimilar materials will almost always result in a nonrecyclable combination. Innovative designs can usually achieve the same goal while allowing easy separation of the two materials (this usually helps in return shipments as well).

Many cushioning materials in years past have relied on CFC's and other ozone depleting substances (ODS) for various manufacturing processes. Today almost all cushioning materials are available that do not use CFC's or ODS's in their manufacture.

Whenever possible, materials that are manufactured without CFC's or ODS's should be specified. All drawings or cushioning specifications should include a statement similar to the following: