Plastic processors weary of losing business to low cost suppliers should be attentive to the opportunities of being competitive by developing unique niches in growing markets. Plastic pallet manufacturing is a perfect example.
As of January 2004, all wood products exported from the U.S. are required to comply with IPPC international standard ISPM 15, which regulates wood and wood packaging in international trade. The ISPM 15 standard includes wood pallets. Therefore, all wood pallets going into countries involved with the IPPC, including the European Union, China, Australia and other significant demographics, must be treated and marked.
Why is that an opportunity? The cost to treat and mark pallets increases product cost. This additional expense includes the use of kiln-dried wood, insecticides, labor, and disposal of treated wood. Plus, there is the risk that items shipped might be delayed at port of entry, thereby increasing the likelihood of theft, spoilage, or additional damage.
Plastic pallets can eliminate many headaches now associated with using wooden pallets for shipping internationally because they do not need to pass the double inspection now necessary in IPCC-compliant countries.
The obstacle to plastic pallets taking a larger share of the market, up until this point, has been production costs. However, with recent base increases in the cost of wooden pallets, combined with cost-saving methods of producing plastic pallets with structural foam molding, plastic pallets have become much more competitively priced.
What is a plastic pallet?
Plastic pallets come in many shapes and sizes. It can be a 48 x 48 in. double deck, 4-way entry, heavy duty, stackable, reusable pallet that performs much like a hardwood pallet. Pallets are also clean, can be colored, are environmentally friendly (recyclable) and have infinite choices in shape, texture, controlled strength and cost. They can be double deck, single deck, any size up to, say, 60 x 60 in., shaped to conform to a product, shaped to stack, provided with nonslip surfaces, etc. They can be made in one piece, two pieces, or multiple piece designs that are welded, snapped, or mechanically fastened together.
How is it made?
There are many methods of shaping plastics. Extrusion, thermoforming, blow molding and injection molding may be considered for plastic pallet production. The most common method is a variation of injection molding called Low-Pressure Structural Foam Molding.
In this process, the plastic is melted by an extruder, a gas is introduced to the plastic melt and the mixture is forced into a mold cavity. Density reduction, ranging from approximately 10-20% or more, is achieved in the molded part. The plastic flows easily into the mold because of the presence of gas bubbles. The result is a low-pressure injection molding process using low-pressure molding machinery and low-pressure aluminum molds. The pallet has a high stiffness-to-weight ratio and has a rugged, durable appearance.
The structural foam injection process allows flexibility in shape and rib design. This provides for strength at low weight that is not achieved by other plastic processes. It is a clean, automated process, requiring a minimum level of relatively low skilled labor. One worker can monitor the machine and perform secondary operations when required.
What are plastic pallets made from?
Usually high density polyethylene (HDPE) of a low melt index is used for strength and stiffness. Recycled materials are used extensively and effectively. The Structural Foam Molding process is very forgiving when it comes to plastic materials. Fillers including recycled plastic, mineral and wood composite may be added to further reduce costs. Even commingled recycled materials are usable as a blend. Occasionally, demanding applications may require a glass-filled HDPE or an engineering resin such as a polycarbonate. Metal stiffeners or other materials may also be inserted into the structure.
Density reduction of the plastic enables a thicker wall at the same weight. As wall thickness increases, rigidity increases exponentially. Density reduction is accomplished via an inert gas or a chemical blowing agent or a combination of both. The most common and cost-effective method is nitrogen gas.
Pallets may be molded individually or in multiple cavities. In addition, multiple molds with different shapes and weights -- as well as family molds for complete assemblies -- can be molded in a single cycle. Because structural foam is a low-pressure molding process, molds can typically be made from aluminum. These weigh less than steel, cost less, are easier to install and transport, and conduct heat more efficiently, resulting in shorter cooling times. Machining aluminum requires considerably less time, resulting in lower manufacturing costs.
Unlike conventional injection machines, structural foam machines are equipped with an external manifold system and multiple nozzles. Multiple nozzles reduce flow length and keep cavity pressures low plus molds do not require internal manifolds.
In addition to the structural foam process, a separate process known as gas-assist may also be employed to mold heavy or uneven cross sections. Gas assist is a method of injecting gas directly into specific areas of the part to "core out" a section. This further reduces weight with the benefit of reduced clamp force requirements.
A distinct advantage of the structural foam process includes the ability to sequentially mold parts. Sequential molding means turning on and off individual nozzles to fill specific molds or specific areas of a mold over a given time.
Parts exceeding rated clamp force can be molded using sequential injection. Sequential injection offers many advantages, including the ability to double the machine''s molding capacity. It is possible to mold parts requiring double the rated clamp force of the machine by shooting the parts in sequence and allowing a short dwell time between injection shots.
What markets are the best candidates?
Food and textiles are proving to be good markets for plastic material handling as treated lumber may contaminate finished goods. The automotive and electrical markets seem to be moving to plastic pallets because returnable logistics are quite attractive to those industries.
Finding ways to compete in a highly dynamic global economy can be challenging. Companies that are thriving are using better, low cost processing methods. Plus, many are focused on involving themselves in niche, growing marketplaces. Structural foam molding is one such lower cost processing solution for molders to consider. Given the recent international shipping regulations, plastic pallets also present new niche molding and marketing opportunities.
Sources: www.palletenterprise.com/articledatabase/view.asp?articleID=1241; www.apsnet.org/online/exoticpest/Papers/clarke.htm.