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Datapaq Value - Theoretically equivalent cure schedules. |
The Datapaq Value is a unit of measure (Index of Cure) used to quantify the degree of cure experienced by a product for a specific coating and thermal process. The Datapaq Value is derived from the fact that each and every powder coating has a specified cure schedule, achieving optimum cure at defined temperature/time profiles as illustrated. Use of the Datapaq Value allows immediate identification of the quality of cure of any product irrespective of its shape, thermal mass or even orientation within the oven.
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From defined cure schedules (time/temperature) of equal cure it is possible to define a curvelinear function as illustrated below. Any point along this curve is equivalent and would give a 100% cure. An appropriate "Kick-off" temperature is set (360°F) which defines a minimum point at which cross-linking could take place. As well, a maximum temperature should be assigned (410°F), at or above which would cause over cure and possible coating damage.
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Curvelinear
function of identical cure schedules providing |
Utilizing
the power of the Insight software, a curve linear function (perfect
cure curve), is created from theoretically identical cure schedule
values (time and temperature) provided by the powder supplier. Temperature
profile data is then analyzed by the software and the fit between
it and the theoretically perfect cure curve is evaluated and quantified
using the Datapaq Value in the following fashion.
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Generally a Pass/Fail range of acceptable Datapaq values are derived from testing of cure quality by independent physical QA testing. In most situations the acceptable Datapaq Value tolerance band will be found to be 90-115 but in other situations the tolerance band maybe much lower.
A good example of
such case is in the use of IR heating. Employing IR heating the powder
coating undergoes curing well before the substrate temperature rises to
the theoretical cure temperature. Under such circumstances Datapaq Values
in the range of 60-80 have been proven by Differential Scanning Calorimetry
to provide fully cured components. Having defined the acceptable Datapaq
value tolerance band the values obtained on a routine basis can be monitored
as part of QA statistical process control activities.