Maufacturers of advanced composite materials, and organisations that use these materials in end products, share the challenge of how to determine when the degree of material cure meets pre-set requirements.
Today, most organisations view optimisation of cure as a research and development function. Companies often approach this process by curing samples at pre-defined temperatures and comparing the outcomes as part of the R&D process. Armed with the data they glean from these efforts, R&D teams can collaborate with quality assurance and quality control experts to determine how to achieve specific results in material cure. This ensures that finished parts will meet specifications.
But for many companies, meeting particular specifications for material cure remains an inexact and error-prone process. In the absence of methods that examine cure in real time, labor-intensive laboratory testing, such as differential scanning calorimetry (DSC) or dynamic mechanical analysis (DMA), must be performed. This work involves repeatedly halting and restarting the cure process to determine how long it takes for the material to cure at a given temperature. This can delay the development process.
For example, a company may want to develop a process to complete the cure of a sheet molding compound (SMC) part in three minutes or less. Its R&D group would define the ideal characteristics of the end product in terms of strength, toughness, rigidity, surface finish, or other properties. Then the team might cure the material for a set amount of time, stop the cure, and then perform laboratory tests such as DSC or DMA to determine the degree of cure after a given amount of time at a given temperature. Once this is done, curing can resume.
This process must be repeated several times to glean enough data to determine whether finished parts made with the material will perform as expected. Materials left to cure too long may become brittle; those taken out too soon may not be strong enough to meet specifications. Either way, manufacturing throughput and efficiency are reduced. There is also the potential for significant wasted energy, time and expenditures if thermosets are cured longer than necessary.
Dielectric cure monitoring is widely used in the manufacture of SMC, bulk molding compound (BMC) and epoxy molding compound (EMC) to characterise curing behaviour. By measuring the cure of the sample under actual processing conditions, the quality of the material can be determined before it is used in production.
Dielectric cure monitoring is the only mature testing method that allows users to obtain critical data on curing thermosets in real time, over the course of the entire cure. Dielectric cure monitoring, also known as dielectric analysis (DEA), can accelerate R&D processes by eliminating the need for more time-consuming and less accurate forms of testing. It can also speed the transition from R&D to quality control and quality assurance by providing QA/QC teams with solid data upon which they can base their work—helping to ensure the quality and reliability of finished products. With dielectric cure monitoring, there’s no guessing.