Lambient

Application Notes

Cure Monitoring of Polyurethane

Lambient Technologies studied room temperature cures of a polyurethane resin with three different catalysts. An LT-451 Dielectric Cure Monitor made measurements during each test at excitation frequencies from 0.1 Hz to 100 kHz for 24 to 36 hours.
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Interfacing with the Instrument Terminal Blocks

How to use the start triggers and digital outputs.
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LT-451 and LCR Meter Comparison

The Lambient Technologies LT-451 Dielectric Cure Monitor is designed for dielectric measurements of polymeric materials during the curing process, and a typical LCR (Inductance-Capacitance-Resistance) meter, such as the QuadTech 1920, is designed for high speed measurements of the electrical parameters of electronic components.
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Dielectric Cure Monitoring of an Acrylic Adhesive

Lambient Technologies tested samples of a commercially available two-part acrylic structural adhesive with the LT-451 Dielectric Cure Monitor.
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Cure Monitoring of Near-UV Cured Gel Nail Polish

Lambient Technologies tested the base gel for a nail polish system that requires near-ultraviolet light to cure.
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Reducing Noise in Dielectric Sensors

Lambient Technologies conducted several tests to measure noise with a Mini-Varicon sensor when used with the LT-451 Dielectric Cure Monitor, and demonstrated that electrical interference may be reduced effectively with grounded shields around the sensor.
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Errors in Parallel Plate Measurements (The Effect of Surface Texture)

This application note will examine the effect of a textured sample surface similar to that of a fabric. The resulting measurement of permittivity is less than the true permittivity of the material and results from the contribution of air pockets created by the textured surface. This application note will model the effect of these air pockets to develop an understanding of the measurement error.
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Using the CureView LT-4203 Option

CureView has an option to facilitate ASTM D150 standard measurements with the LT-4203 Parallel Plate Test Fixture. This option allows the user to calibrate the LT-4203 for accurate measurements, make multiple measurements with calculation of average and standard deviation, and automatically calculate dielectric constant and dissipation for the contacting electrode method of measurement.
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CureView Material Properties Parameters

Raw gain-phase data measured by CureView and the LT-451 or LTF-631 Dielectric Cure Monitors is converted to the dielectric properties of permittivity (ε') and loss factor (ε"). Loss factor, however, has two components...
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Connecting Dielectric Sensors and Cables

Dielectric sensors connect directly to the instrument with a three-terminal Dielectric Sensor Connector or with an extension cable. To reduce noise in the response signal, the signal leads from the sensor should be shielded.
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Sample Preparation For Dielectric Measurements

Clean sensors with acetone, alcohol or other solvent to remove oils and contaminants. Solvent or water adsorbed onto the surface of the sensor normally will not interfere with cure monitoring because it is released at elevated temperatures and would not be present at typical process temperatures.
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Diagnosing Instrument Operation

Occasionally it may be necessary for a user to test either the LT-451 Dielectric Cure Monitor or the LTF-631 High Speed Dielectric Cure Monitor for proper operation. It is important to investigate the various parts of the system to establish that a component is working as expected, or to determine that a component is faulty.
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Dielectric Measurements During Post-Cure

Large composite structures such as an airplane wing are processed in autoclaves or molds that apply pressure to form the part until it has cured. The need to maximize use of this equipment may require cycling material through it as quickly as possible, and often a part is removed as soon as it has hardened enough to retain its shape. Afterwards, it may undergo post-cure in an oven for several hours to several days. During this time cure continues at elevated temperature until the composite material has hardened further or achieved other desired properties.
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Cure Monitoring of Carbon Fiber Prepreg

Samples from a single batch of carbon fiber reinforced prepreg (CFRP) were tested for repeatability and effect of temperature on cure rate. The data from dielectric cure monitoring clearly show that:
(1) Critical Points identify characteristic features of the cure such as minimum ion viscosity, maximum slope of log(ion viscosity) and the time to a chosen end of cure and,
(2) Cure time decreases as cure temperature increases, as expected for a reaction that is thermally driven.
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SMC and BMC Cure Monitoring

The curing behavior of Sheet Molding Compound (SMC) was observed using the LT-451 Dielectric Cure Monitor. Bulk Molding Compound (BMC) is the generally the same material as SMC but in bulk form, so the analysis of results apply to BMC as well.
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