Moulded pulp

Moulded pulp uses the same wood-based raw materials as paper production, plus a range of plants fibres such as bagasse (sugarcane pulp), bamboo, reed, wheat straw and palm. Many types of agricultural by-products are suitable, as well as waste from other types of raw material production. Also recycled material, such as old corrugated container (OCC). The type of fibre often depends on geography, with seasonal and locally available fibres being preferable due to the relatively lower price. These additional fibres help to improve the mechanical properties and have cost advantages over traditional wood pulp.

Moulded pulp is produced using various techniques, which will affect the end result. The simplest plain moulding technique, known as one-cast, uses a wire mesh for the mould. The pulp is drawn onto the mesh and the water sucked out to produce relatively thick walled parts (6-8 mm). This technique makes use of recycled paper and card. It is used for industrial and lower grade, relatively heavy packaging.

Transfer moulding adds an additional step in the process, also called after-pressed, whereby the moulded pulp is compressed on the inside to produce a smooth surface and thinner wall section (3-5 mm). The superior surface properties and strength are utilised for a range of electronic, household and product packaging. Things like egg cartons and medical products (urinals) are produced in large volumes and at high speed with this process. After transfer moulding, it is possible to further enhance the smoothness of the surface, add debossed logos and other features, by hot pressing.

Thermoforming produces thin walled parts between 0.5-1.5 mm. It is a highly automated process unlike traditional wet pulp forming. Once the water has been removed the pulp is hot pressed to produce complex parts with smooth faces in as little as 60 seconds. It is typically used to make take out food clamshells, drinks cups, salad bowls, pasta bowls, and high end inserts for cosmetics, healthcare and electronic packaging. There are many variations on this technology and it is rapidly becoming more efficient, with cycle times well below 30 seconds, in an effort to make it cheaper.