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Pulp molding is the process used to create recyclable packaging material. This material is created using only recycled newspaper and corrugated fiberboard. Great everyday examples of containers made using pulp molding are trays used to carry multiple drinks at fast-food restaurants, clamshell containers, and food trays. This type of container has greatly increased in popularity in the past 10 to 15 years, as consumers began requesting recyclable packaging.
There are four types of pulp molding products available to consumers: thick wall, transfer, thermoformed fiber, and processed. All four methods require significant amounts of energy and pressure to shape the recycled fibers into the required shapes. It is important to note that although the finished product is made from recycled materials, there is a significant amount of water and energy required to create the final product. The heavy resource requirement has led some experts to question if these products are truly better for the environment.
Thick wall pulp molding is used for heavy item packaging, molded pulp pallet trays, and auto replacement parts. The product itself is quite rough on one side and slightly smoother on the other side. The intended use of this type of pulp molding is for heavy materials. The roughness is not a primary concern, but the relative strength is. Many firms design thick wall products to withstand significant pressure and often rate the different products to help people decide which one to use.
Transfer products have thinner walls and are created using a process very similar to paper mache sculptures. The process is the most commonly used production method for pulp molding materials. A mold is created using very fine wire mesh in the converse shape of the end product. Fibrous materials are sprayed on the mold, covering it completely; as the material dries, the wire frame is separate from the product and used again. For an example of a product made with this process, look at drink trays, cup carriers, egg trays, or fruit trays used in stores.
The most recent development in pulp molding is thermoformed fiber. This method produces strong, smooth-surfaced products. Heat is added to the process at specific stages, allowing the material to have the look and feel of plastic, while being made from recycled fibers.
Some products require two stages to become complete: forming and then finishing. These types of products are considered processed. The unit first completes any of the first three processes and is then passed onto the processing section. Adding color, die-cutting, trimming or the use of additives are all parts of secondary processing.