hotpressing

Hot pressing, also written hot-pressing or hot-press, is a manufacturing process in which heat and pressure are applied to a material to bond, cure, or densify it. The process is typically carried out with a hydraulic or mechanical platen press or in a mold, using heated platens to transmit thermal energy and compressive force. Temperature, pressure, time, and cooling rate are selected according to material and adhesive or resin systems.

In wood-based products, hot pressing is used to cure reactive adhesive systems and bond veneers or particles to form plywood, particleboard, and medium-density fiberboard. Typical cycles involve temperatures from 100–200°C and pressures ranging from a few megapascals, with cure times from seconds to minutes.

In composites and thermoplastics, hot pressing consolidates resin-impregnated fibers, prepregs, or thermoplastic sheets into laminates or molded parts. Materials are heated toward or beyond their glass transition or melting temperature, then pressed to achieve densification and surface finish. Hot pressing is also used in powder metallurgy and ceramic processing to densify powder compacts; heat and pressure promote sintering and reduce porosity.

Equipment and process variables: platen-to-plate contact is uniform to prevent differential shrinkage; vacuum may be used to remove entrapped air; tooling material and cooling control dimensional changes and residual stresses.

Advantages include strong, uniform bonds, good surface finish, and shorter cycle times compared with some alternative processes. Disadvantages can be high energy consumption, risk of thermal degradation, moisture-related defects, and equipment costs.

Related processes include hot isostatic pressing, autoclave curing for composites, and cold pressing as a low-temperature alternative.