Vacuum Bag Sealant Tape in Wind Turbine Blade Manufacturing
Vacuum bag sealant tape is a relatively small component of the composite manufacturing system, but it plays an important role in producing wind turbine blades. Its primary function is to create a temporary vacuum-tight boundary between the vacuum bag film and the mould. Depending on the bagging design, sealant tape may also be used around film overlaps, pleats, hoses, ports, connectors and other local details where vacuum integrity must be maintained.
Selecting a suitable vacuum bag sealant tape should not be based solely on a chemistry description, maximum temperature rating or marketing claim. Its suitability depends on the complete manufacturing process, including the vacuum bag film, mould surface, release system, laminate geometry, vacuum level, temperature profile, process duration, resin exposure and removal requirements.
For this reason, the correct approach is to qualify the exact product grade, dimensions and configuration under representative process conditions, using current technical documentation and controlled process trials.
What Does VARTM Mean?
VARTM stands for Vacuum-Assisted Resin Transfer Moulding. It is a composite manufacturing process in which vacuum pressure is used to assist the flow of liquid resin through a dry fibre reinforcement package.
In simple terms, the process can be described as:
dry laminate → vacuum bagging → vacuum generation → resin introduction → resin flow through the fibres → laminate impregnation → curing.
In wind turbine blade manufacturing, layers of reinforcement material are positioned in the mould according to the laminate design. The dry lay-up is then covered with the required consumable materials and vacuum bag film. Vacuum bag sealant tape is used around the perimeter of the bag to create a sealed environment.
Once the required vacuum conditions have been achieved, liquid resin is introduced through strategically positioned ports and feed lines. The pressure differential drives the resin through the dry reinforcement. After the laminate has been fully infused, the resin is cured according to the specified process cycle.
Why Is Vacuum Integrity Important in VARTM?
Vacuum plays several important roles in the VARTM process. It helps to:
- consolidate the fibre package,
- drive resin through the dry laminate,
- reduce trapped air,
- maintain the required pressure conditions during infusion,
- support consistent laminate geometry and fibre content.
Consequently, vacuum bag integrity is an important part of the overall VARTM process. A leak can allow air to enter the system and potentially affect resin flow, impregnation and laminate quality.
However, not every laminate defect should automatically be attributed to a vacuum leak. Infusion performance is also affected by resin viscosity, temperature, fibre architecture, flow media, port positioning, laminate permeability, part geometry and venting strategy.
VARTM vs. Vacuum Bagging
The terms VARTM and vacuum bagging are related but should not automatically be treated as interchangeable.
Vacuum bagging is a broader term for processes that use a vacuum bag to apply pressure and consolidate a composite laminate.
VARTM, by contrast, specifically refers to a process in which vacuum pressure assists the transfer of liquid resin into a dry reinforcement structure.
Depending on the manufacturer and process documentation, similar technologies may also be described as:
- vacuum infusion,
- resin infusion,
- vacuum-assisted resin infusion,
- vacuum-assisted resin transfer moulding.
Terminology can vary between organisations, so the exact process definition should always be confirmed in the applicable manufacturing documentation.
What Does Vacuum Bag Sealant Tape Do?
Vacuum bag sealant tape is a deformable, pressure-sensitive process material positioned between the vacuum bag film and the tooling surface. When properly applied, it conforms to the interface and helps prevent air from entering the vacuum system.
Its functions can include:
- sealing the perimeter of the vacuum bag,
- maintaining the required vacuum level,
- supporting laminate consolidation,
- enabling controlled resin infusion,
- maintaining the vacuum environment during heating and curing.
However, vacuum bag sealant tape is a process consumable, not a structural component of the finished blade.
It should not be confused with:
- structural adhesive used to bond blade shells,
- permanent sealing material incorporated into the finished blade,
- field-repair material,
- a guarantee of laminate quality.
Vacuum Sealant Tape as Part of the Complete Process
One of the most important principles when selecting vacuum bag sealant tape is that it should not be evaluated as an isolated product.
In an actual manufacturing process, it forms part of a larger system:
mould → mould coating → release system → laminate → consumables → vacuum bag film → sealant tape → ports and hoses → vacuum equipment.
A loss of vacuum can therefore have many potential causes.
These may include:
- incorrectly prepared mould surfaces,
- contamination,
- insufficient bag slack,
- bridging,
- incorrectly sealed ports,
- leaking hoses,
- poor tape joints,
- insufficient application pressure,
- excessive sealant flow or creep,
- unsuitable process temperature.
This is why higher tack does not necessarily mean better process performance.
A high-tack tape cannot compensate for insufficient bagging material, poor port design, film bridging or a leaking hose connection.
How Product Form Affects Sealant Tape Selection
Vacuum sealant tapes are available in different constructions and profiles. Examples include:
- thick sealant beads,
- low-profile sealant tapes,
- wide sealant tapes,
- film-backed products,
- products intended for local repairs,
- materials designed for ports or penetrations.
A thicker sealant bead may provide better conformity around uneven flange surfaces, joints, pleats and local geometry. A low-profile sealant may be more appropriate for a smooth, controlled flange.
A wide patch may be designed for a local film repair or penetration rather than for the primary perimeter seal.
Therefore, products should not be substituted simply because they belong to the same general material family.
Qualification should consider the exact:
- product,
- product code,
- dimensions,
- cross-section,
- application method,
- intended use,
- film material,
- mould surface,
- release system.
Is Every Vacuum Bag Sealant Tape a Butyl Tape?
No.
Publicly available product documentation includes materials described as:
- butyl,
- polyisobutylene,
- synthetic rubber,
- synthetic rubber-based sealant.
These descriptions should not be treated as universal performance classifications.
Even products described as butyl-based can differ significantly in:
- formulation,
- fillers,
- plasticiser package,
- cross-section,
- hardness,
- tack,
- flow,
- creep,
- thermal resistance,
- film compatibility,
- tooling compatibility,
- residue,
- removal behaviour.
The chemistry description therefore provides useful information, but it does not replace product-specific technical data and process qualification.
What Do Published Temperature and Size Data Tell Us?
Public manufacturer data illustrate why apparently simple parameters need to be interpreted carefully.
| Example product | Published base | Temperature wording | Example format |
| Airtech Airseal 2 | Synthetic rubber | 150°C bag-to-tool; 180°C bag-to-bag | 3 mm × 12 mm × 15 m |
| Easy Composites ST150 | Polyisobutylene, marketed as butyl | 150°C maximum use | 3 mm × 12 mm × 15 m |
| Airtech AT-200Y | Synthetic rubber | 204°C maximum use | 3 mm × 12 mm × 7.62 m |
These are examples of published manufacturer declarations, not independent qualification data, head-to-head test results or product recommendations for wind turbine blade production.
A common published temperature rating does not mean that two products will perform identically under the same process conditions.
Performance may depend on:
- exposure time,
- actual seal-line temperature,
- interface,
- application pressure,
- geometry,
- vacuum bag film,
- mould surface,
- sealant flow,
- creep,
- cooling conditions,
- removal temperature.
Even bag-to-tool and bag-to-bag temperature ratings may refer to different interface conditions.
Likewise, product dimensions are primarily procurement and geometry information. They are not proof of vacuum integrity.
Temperature Ramp: Why Does It Matter?
When evaluating vacuum bag sealant tape, the maximum process temperature is only one part of the thermal profile.
The process should also define the temperature ramp, meaning the rate at which temperature increases or decreases over time.
For example, a ramp of 2°C/min means that the temperature is increased at approximately two degrees Celsius per minute.
A process specification may therefore include:
- starting temperature,
- heating rate,
- peak temperature,
- dwell time,
- cooling rate,
- final temperature.
This matters because sealant behaviour can change progressively during heating. Depending on the formulation and process conditions, the material may soften, flow, creep, change thickness or alter its adhesion to the interface.
Two products with the same stated maximum temperature can therefore behave differently if their exposure time, heating rate or interface conditions differ.
How Should Vacuum Bag Sealant Tape Be Specified?
The starting point should be the actual process envelope.
Define:
- minimum application temperature,
- relevant humidity conditions,
- target vacuum level,
- vacuum generation method,
- heating ramp,
- peak temperature,
- dwell time,
- resin exposure,
- cooling conditions,
- removal temperature and method.
The actual production configuration should then be fixed as far as practical, including:
- vacuum bag film,
- mould,
- mould coating,
- release agent,
- hoses,
- ports,
- connectors,
- joints,
- corners,
- pleats,
- repair areas.
Only after these conditions are understood can a specific sealant tape be properly evaluated.
Laboratory Testing vs. Process Qualification
Controlled adhesive testing can be useful when characterising vacuum sealant tape.
Methods such as:
- ASTM D3330/D3330M-04(2025),
- ASTM D3654/D3654M-06(2024),
- ASTM D6195-22
can support the evaluation of properties such as peel, shear and loop tack.
However, these tests do not automatically qualify a tape for wind turbine blade manufacturing.
An adhesive test does not reproduce the complete:
- vacuum environment,
- thermal cycle,
- film movement,
- resin exposure,
- mould interface,
- VARTM process,
- removal operation.
Laboratory testing should therefore be treated as one element of qualification, not a replacement for representative process testing.
If a standard method is materially modified, it should be described as “modified from” the relevant standard rather than as being performed “in accordance with” it.
What Should a Representative Sealant Tape Test Include?
A representative test fixture should reproduce the important features of the production process.
Depending on the application, this may include:
- production vacuum bag film,
- representative flange length,
- sealant joints,
- corners,
- pleats,
- penetrations,
- hoses,
- ports,
- local repair details.
During the test, it is useful to record:
- initial absolute pressure,
- final absolute pressure,
- vacuum hold time,
- pump isolation,
- temperature,
- instrument accuracy,
- system volume or bag area,
- pressure behaviour throughout the complete cycle.
A simple statement such as “pressure dropped by X” is not a universal measure of leak performance. The result depends on system geometry, volume, temperature, bag compliance and the test configuration.
Acceptance criteria should therefore come from the validated process, customer requirements or plant specification, rather than from a universal limit presented in a general article.
Five Steps to Qualify Vacuum Bag Sealant Tape
- Define the Complete Process Envelope
Document the temperature range, vacuum level, heating rate, peak temperature, dwell time, resin exposure, cooling conditions and removal requirements.
- Map Every Seal Detail
Include:
- straight flanges,
- joints,
- corners,
- pleats,
- ports,
- hoses,
- penetrations,
- repair areas.
- Define Acceptance Criteria Before Testing
Depending on the process, criteria may include:
- vacuum stability,
- allowable pressure change,
- film integrity,
- thermal-cycle performance,
- residue,
- removal behaviour,
- lot-to-lot consistency.
- Run Replicated Process Trials
The test should reproduce the actual vacuum, thermal, chemical and removal cycle as closely as practical.
- Control Procurement Changes
Approval should apply to the exact product code, dimensions and variant. Control should also cover:
- current TDS/SDS,
- storage conditions,
- shelf life,
- lot traceability,
- supplier source,
- formulation changes,
- product changes,
- dimensional changes.
Common Vacuum Bag Sealant Tape Failure Modes
Unstable Vacuum Before Infusion
If vacuum cannot be maintained before infusion, the sealant tape should not automatically be considered the cause.
First check:
- vacuum pump,
- hoses,
- ports,
- valves,
- gauges,
- connectors.
Then investigate:
- contamination,
- insufficient sealant compression,
- poor tape joints,
- wrinkles,
- incorrect application temperature,
- seal geometry.
Leakage Appearing During Heating
A leak that occurs only during heating may indicate:
- sealant flow,
- creep,
- vacuum film movement,
- thermal expansion,
- exceeding the product’s time-temperature envelope,
- interaction with the mould surface.
A room-temperature leak test alone may therefore fail to identify a problem that occurs during the actual manufacturing cycle.
Excessive Residue After Removal
Potential causes include:
- excessive temperature,
- excessive dwell time,
- interaction with the release system,
- specific vacuum film characteristics,
- incorrect removal temperature.
Claims such as “clean removal” should be treated as supplier claims until verified under the intended process conditions.
Dry Areas in the Laminate
A dry laminate area is not necessarily caused by a vacuum bag leak.
Other factors should also be investigated, including:
- resin viscosity,
- temperature,
- flow-media configuration,
- race tracking,
- venting,
- degassing,
- pressure distribution,
- port positioning,
- local flow resistance.
Vacuum sealant tape is only one process variable within VARTM.
What Information Should You Request from the Supplier?
Before approving a vacuum bag sealant tape, it is advisable to obtain the current technical documentation, including, where applicable:
- TDS,
- SDS,
- exact product code,
- available dimensions and tolerances,
- storage conditions,
- shelf-life basis,
- lot traceability,
- definition of the temperature rating,
- compatible vacuum films,
- compatible tooling surfaces,
- test methods,
- change-notification procedures.
Statements such as “high tack,” “clean removal” or “developed for wind turbine blades” should remain supplier claims until they have been verified under the intended process conditions.
IEC 61400-5 and DNV-ST-0376: What Should Not Be Assumed?
Wind turbine blade manufacturing operates within a broader framework covering design, materials, testing, manufacturing and quality management. Relevant standards and certification frameworks may include:
- IEC 61400-5:2020+AMD1:2025
- DNV-ST-0376, edition 2024-04
However, this does not mean that there is a universal “IEC-compliant sealant tape” category or that every tape used in blade manufacturing is automatically DNV-approved.
Claims such as:
“IEC-compliant vacuum bag sealant tape”
or
“DNV-approved vacuum bag tape”
should therefore not be made without a specific, current and verifiable document confirming the applicable product, scope and approval.
How to Read a Vacuum Sealant Tape TDS
A Technical Data Sheet is an important starting point, but it does not automatically qualify a product for a specific manufacturing process.
When reviewing a TDS, ask:
What exact product is being described?
Does the product code, size and variant match the material being purchased?
What does the temperature rating actually mean?
Is it a continuous-use temperature, maximum-use temperature, process temperature or a value measured under a specific interface condition?
How long can the product withstand that temperature?
What substrate was used in the test?
What vacuum film was used?
How was the surface prepared?
What application pressure was used?
How was success or failure defined?
Is the stated value typical or a specification limit?
The distinction between a typical value and a guaranteed specification is particularly important. A typical value should not automatically be treated as a contractual performance limit.
Key Principles for Selecting Vacuum Bag Sealant Tape
The selection process can be summarised in several key principles:
- Qualify the specific product, not just the chemistry.
- Evaluate the complete vacuum bagging system, not the tape alone.
- Consider time and temperature together, not maximum temperature alone.
- Test the actual interfaces: film, mould, coating and release system.
- Reproduce relevant geometry, including corners, pleats, joints and ports.
- Do not replace process trials with a single tack or peel test.
- Define acceptance criteria before qualification testing.
- Control product and supplier changes.
- Request current TDS/SDS documentation.
- Do not claim IEC or DNV approval without verified documentation covering the specific product and application.
Frequently Asked Questions About Vacuum Bag Sealant Tape
What does VARTM mean?
VARTM stands for Vacuum-Assisted Resin Transfer Moulding. It is a composite manufacturing process in which vacuum pressure assists the flow of liquid resin through a dry fibre reinforcement structure.
What does vacuum bag sealant tape do in wind turbine blade manufacturing?
It creates a temporary vacuum-tight boundary between the vacuum bag film and the mould and, where required, at local details such as joints, pleats, ports and penetrations.
Is every vacuum bag sealant tape a butyl tape?
No. Public product documentation includes both polyisobutylene/butyl-based materials and synthetic-rubber products. The exact chemistry should always be confirmed in the current product documentation.
Are two tapes with the same 150°C temperature rating equivalent?
No. Their performance may differ in terms of exposure time, interface, flow, creep, film and tooling compatibility, residue and removal behaviour.
What pressure-decay limit should be used?
There is no universal limit. The process owner should define the acceptance criterion based on test duration, system geometry or volume, temperature, pressure basis and instrument accuracy.
Can peel or tack testing replace a process trial?
No. Peel, shear and tack testing can support material characterisation and quality control, but they do not demonstrate vacuum integrity, thermal stability, resin compatibility or removal performance in a complete blade manufacturing process.
Conclusion
Vacuum bag sealant tape is a relatively small consumable, but it plays an important role in the manufacture of composite wind turbine blades. In VARTM — Vacuum-Assisted Resin Transfer Moulding, vacuum integrity is one of the conditions required to establish and maintain the pressure differential needed for controlled resin infusion.
At the same time, sealant tape performance cannot be determined by chemistry or maximum temperature alone. Its behaviour depends on the complete system:
sealant tape + vacuum film + mould + mould coating + release system + geometry + vacuum + temperature + time + resin + removal conditions.
For this reason, selecting a product based on a single specification such as “150°C,” “butyl,” “high tack” or “clean removal” is not sufficient for engineering approval.
A robust qualification process should begin by defining the complete process envelope, followed by an evaluation of all relevant interfaces and seal details, a review of current supplier documentation and representative, repeatable process trials.
The key question should therefore not be:
“Which vacuum bag sealant tape has the highest temperature rating?”
but rather:
“Which specific vacuum bag sealant tape, in the required size and configuration, provides the required vacuum integrity, thermal stability, material compatibility and controlled removal throughout our validated VARTM process?”
That is the basis for making a technically defensible decision when selecting vacuum bag sealant tape for wind turbine blade manufacturing.