Low-cost wood is still dominantly used for pallets, but reusability of plastics is a growing attraction among manufacturers looking for sustainable material-handling options. Wood pallet remains a strong force globally for transportation, distribution and storage of manufactured products. Its pre-eminence has been dictated largely by cost, but plastic pallets continue to make inroads because of their durability, reusability and light weight. Plastic pallets made by injection molding, structural foam, thermoforming, rotational molding and compression molding are gaining acceptance in a range of markets including foods, beverages, pharmaceuticals, groceries, automotive and the US Postal Service. The difficulty and cost of wood pallet disposal has always been a concern, but recent focus on the environment is fueling a renewed interest in plastics as an alternative. Reusability is a major attraction making them more economically feasible on a cost-per-trip basis, but the one major hurdle is rising resin prices.

Though introduced in 1960s, it was only in the 1980s, that the automotive market pioneered the use of reusable plastic pallets to minimize handling costs and eliminate disposable packaging issues. Because they cost more than wood, plastic pallets have always had their niche in managed pools or captive closed-loop systems for work-in-process or distribution. Several plastic pallet makers have capitalized by introducing low-cost versions that compete favorably with wood. One method of containing costs is to use recycled resin and scrap regrind. Another factor favoring plastics are international regulations that require treatment of wood to reduce pest migration in export pallets. In future, plastic pallets are expected to play an even larger role as companies adopt greater levels of automation in their warehouses. Greater automation requires repeatability and reliability, and plastics' tailored designs and consistent dimensions and weights offer a distinct advantage over wood pallets, which are vulnerable to splintering off shards and pulling apart as nails loosen.
Currently, wood has more than 90% share of the US pallet market, while plastics account for 2-5%. There are about 2 billion pallets in use every day and approximately 650 million are made and repaired each year. Pallet & Container Research Lab at Virginia Polytechnic Institute and State University estimates that although wood pallets dominate, the plastic pallet market has doubled over the last 10 years. A recent study by the Freedonia Group shows that plastic pallets will have highest growth rate, advancing 2.4% annually to over 130 million pallets by 2012, though their market share will still be under 10%. Meanwhile, demand for wood pallets is projected to increase at a rate just below that of the market average, partly due to growth of pallet refurbishing services. Overall, US pallet demand is forecast to grow 1% pa through 2012 to 1.5 billion pallets valued at $16.8 billion.
Currently, wood has more than 90% share of the US pallet market, while plastics account for 2-5%. There are about 2 billion pallets in use every day and approximately 700 million are made and repaired each year. Pallet & Container Research Lab at Virginia Polytechnic Institute and State University estimates that although wood pallets dominate, the plastic pallet market has doubled over the last 10 years. A recent study by the Freedonia Group shows that plastic pallets will have highest growth rate, advancing 2.4% annually to over 130 million pallets by 2012, though their market share will still be under 10%. Meanwhile, demand for wood pallets is projected to increase at a rate just below that of the market average, partly due to growth of pallet refurbishing services. Overall, US pallet demand is forecast to grow 1% pa through 2012 to 1.5 billion pallets valued at $16.8 billion.
There are no firm statistics on plastic pallet manufacturing, but it is generally believed that injection molding and thermoforming are the dominant processing methods. Each of the five main processes used to make pallets has its own advantages in terms of productivity, performance and end-use application. Injection molding uses high pressure to produce more engineered parts with complex geometries, ribs and tight tolerances. It is a high-output process but tooling can be very costly. Structural foam uses low pressure and less costly aluminum tools. The pallet has an integral skin and a cellular core with a high strength-to-weight ratio.
Single- or twin-sheet thermoformed pallets provide light weight and modest tooling cost for low to medium-volume production. Thermoformed pallets are nestable and are used by the US Postal Service and grocery distributors, providing attractive space savings for truckers and retailers. Rotomolding is typically used for large, custom, heavy-duty pallets for conveyor systems, food processing, and warehouse storage. It offers low-cost tooling but cycle times are longer. Compression molding has emerged as an attractive method that can handle the variable processing characteristics of recycled resins. To combat stable wood prices and increased resin costs, processors of injection and compression molded pallets have turned to using more regrind and recycled plastics. Even in structural foam, the key to better economics is the use of recycled materials. Compression molding is also well positioned in the pallet market because it handles the process variations of recycled materials.

The International Standard for Phytosanitary Measures 15 (ISPM 15) requires all solid wood packaging like pallets to be heat treated or fumigated with methyl bromide, both of which add cost. Shippers of time-sensitive products are reportedly opting for competitively-priced plastic pallets to avoid potential delays in certification of wood pallets. As a result, the export market has grown significantly in the last 5 years. One of the greatest threats to wood pallets is the start of the first pooling system using RFID-enabled plastic pallets. Pallet pools allow users to rent pallets and return them for inspection and reuse. The IGPS system enables plastic pallets to go beyond typical closed-loop systems and maximizes their reusability. And the innovative RFID technology ensures that the expensive pallets are tracked.
New structural designs to lower cost and weight are being developed. Injection molded and structural-foam pallets are appearing in more complex one and two-piece designs joined with snap-fits and metal fasteners and incorporating steel or nylon reinforcements to provide edge-racking capability. While most injection molded pallets are made of HDPE, at least one company is using PP for greater stiffness. Rehrig Pacific, a leading pallet supplier to beverage companies like Pepsi and Anheuser-Busch, uses PP impact copolymer to achieve higher flex modulus than HDPE. In structural foam, there is growing use of bigger machines with multi-nozzle technology for greater output.
Rotomolded pallets have their niche in heavy-duty, odd-size, custom applications. They are characterized by low-cost tooling, long cycle times, and one of the highest finished part costs among plastic pallet-making processes. Rotomolding produces durable, high-strength, one-piece parts with an average life of 15 yr. Rotomolding has found a home in large industrial transport pallets that carry heavy loads.
An innovative development in single-sheet thermoforming is the new 6.6-lb Air Ride pallet from Novo Foam Products LLC, Westlake , Ohio . It's one of the industry's lightest plastic pallets. Most single-sheet thermoformed pallets weigh in at 6-7 Kg. The Air Ride consists of HIPS bonded to a shape-molded EPS foam core. A patented bonding method is incorporated in the thermoforming process. Dynamic load capacity of 650 Kg is higher than for standard single-sheet pallets. It is for limited air-freight shipments (one or two trips), primarily those originating from Asia.
An innovative development in single-sheet thermoforming is the new 6.6-lb Air Ride pallet from Novo Foam Products LLC, Westlake , Ohio . It's one of the industry's lightest plastic pallets. Most single-sheet thermoformed pallets weigh in at 6-7 Kg. The Air Ride consists of HIPS bonded to a shape-molded EPS foam core. A patented bonding method is incorporated in the thermoforming process. Dynamic load capacity of 700 Kg is higher than for standard single-sheet pallets. It is for limited air-freight shipments (one or two trips), primarily those originating from Asia.
A non-traditional method of making pallets is a unique vibrational molding process for low production volumes (typically 500 parts or fewer). The Unifuse VIM process developed by Unifuse LLC sinters thermoplastic powders using vibration plus low heat (below the resin melting point) and no pressure. VIM can produce large parts like pallets upto 16 ft long with thick and thin wall sections, deep draws with zero draft, undercuts, and embedded reinforcements. The process generates no waste or molded-in stress. A pallet from two LLDPE pieces that are first molded separately and then fused together has been produced. Low-cost machinery and tooling (aluminum and wood) reportedly make VIM more economical than traditional processes like injection molding, thermoforming, and rotomolding.
Blow molding has found limited commercial success due to technical obstacles. Blow molded pallets require a lot of moving mold sections and a complex layflat involving a large parison. The pallet's square or rectangular shape requires rather tight radius corners and there is a tendency to form thin wall sections and excessive top flash. In Europe , an Italian manufacturer is using extrusion blow molding to make 1000-L IBC containers and 17 Kg pallets for the same containers.
( Source: www.ptonline.com )