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Frequently Asked Questions
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1. Are TechFilm products thermoset or thermoplastic?
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Most TechFilm products are thermoset adhesives. This means that once cured, they are irreversible and will not reflow. Curing is initiated by heat. This is unlike thermoplastics which have the capability of reflowing multiple times.
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2. What are TechFilm's available formats?
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TechFilm products are available in sheets, preforms, or roll format. They can be supplied with or without the reinforcement of non-woven mesh.
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3. How do films and preforms differ from liquids?
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Film and preform products are B-Staged adhesives. They are partially cured to a uniform thickness to fit your product's geometry. They are applied to one surface and then heated to tack to the substrate. There is no mixing or dispensing.
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4. How do I apply the film or preform?
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- Films and preforms can be applied by hand or by transfer. To apply by Hand Placement Method:
The hand placement method is self-explanatory. It is usually used in hand assembly processes with supported performs or films. It can be described briefly as:
- Supported, die cut, preforms are usually supplied with a release liner on each side. The first step is to thaw the preform from cold storage. However, it may be advantageous to peel a corner of the release liner away before completely thawed.
- Remove one or both release liner(s) and place on the part. Remove the other release liner if not already removed.
Proceed to bond the mating substrate surface
The transfer method is usually utilized for unsupported films or preforms. The following describes the transfer procedure.
- Remove the film from cold storage and allow it to warm to room temperature. If humidity levels are high it is advisable to allow it to warm to room temperature in a desiccator or other area of low humidity. After it has warmed to room temperature, if present, remove the release liner from one side of the preform.
- Preheat the substrate to 70°C to 90°C.
- Locate the preform onto the substrate; align by eye or use locating holes if provided on the release liner. Smooth out any trapped air by hand, use of a weight, or with roller or smoothing device. A heated laminator can be used for both the transfer and smoothing processes. Cool the substrate to room temperature or less (the colder the better). A cold plate at 5 to 10°C is very efficient and works well. The release liner may then be removed by hand or by a burst of air.
Proceed to bond the mating substrate surface.
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5. What are the shelf life and storage temperatures of TechFilm products?
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Storage conditions and shelf life for each product are listed on their respective Technical Data Sheets. They can also be found in the selector guides section. Most products should be stored @ -40° C for a year of shelf life.
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6. What is thermal conductivity?
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Thermal conductivity is the measure of how well a material can transfer heat at a thickness per unit area time and thermal gradient and frequently uses units such as W/M-°K, or BTU-in/hr-ft 2-°F. It is represented by the equation:
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Where:
Q = Heat flow
t = Time
T 2 =The hotter of the two contacting surfaces.
T 1=The cooler of the two contacting surfaces.
d = Thickness
A = Area of contacting surfaces
k = Thermal conductivity
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7. How much pressure should I apply to the film?
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Because applications and thickness vary, there is no one specific pressure. However, films and performs generally fall between the ranges of ¼ psi to 5 psi. Factors to consider when selecting the pressure are:
- How much pressure will allow my substrate to lay flat?
Some substrates do not lie flat, but have a low enough modulus and are thin enough that they will lay flat under pressure.
- How fast will the part heat up?
Adhesive flow and cure rate are dependent on temperature. Therefore, a consistent part heating rate is extremely important in process development.
- Initial preform thickness.
The rate of squeeze out is roughly proportional to thickness squared. Therefore the lower the initial thickness the less will be the squeeze out.
- Does preform contain spacer beads or support mesh?
Support mesh or spacer beads will prevent excessive flow by providing a mechanical stop.
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8. What is the cure schedule for TechFilm products?
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Cure schedules for each product can are listed on their respective Technical Data Sheets and can also be found in the 'Selector Guides' section. Typically 150°C for 1 hour.
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When a material has too much pressure on it during cure, it has the possibility of actually forcing the adhesive outside of the desired area of bonding.
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