This section identifies some of the most common manufacturing product defects in the industry, and provides recommendations to assist you in defining and answering troubling questions as you work with PSA products.
Description: PSA tape or converted part exhibits noncontinuous coverage or is missing adhesive.
Possible Causes:
1. Adhesive coating equipment applied a streaked coating.
2. Insufficient adhesive supply to adhesive coating equipment – pump malfunction.
3. Wet adhesive coating abraded by auxiliary coating line equipment.
4. Adhesive confusion during slitting of free film (transfer tape) product.
Possible Solutions:
1. Ensure that adhesive coating equipment applies streak-free coating.
2. Ensure that sufficient supply of wet adhesive is pumped to adhesive coating equipment.
3. Ensure that no auxiliary equipment touches wet adhesive coating.
4. Address adhesive confusion issues as outlined below.
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Description: In roll form, PSA doesn’t unwind cleanly and the adhesive “splits” between two sides of release liner. In converted part, adhesive may “split” between release liner and substrate.
Possible Causes:
1. Selection of unsuitable adhesive/release liner combination.
2. Rough-cut and/or tacky edges created during slitting/rewinding process.
3. Noncontinuous release coating on one or both sides of release liner.
4. Scratched/abraded release coating on one or both sides of release liner.
5. Disruption of cured release coating by static electricity.
6. In converted part, marginal adhesion to “gasket” substrate at time of lamination.
Possible Solutions:
1. Select product with different adhesive and/or greater release differential properties.
2. Modify roll slitting/rewinding process to minimize edge defects.
3. Use scratch-free release liners with 100 percent continuous coating.
4. Check and/or install appropriate static electricity elimination devices.
5. In converted part, implement and document consistent lamination processes.
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Description: PSA tape cross-web roll profile and hardness inconsistent, suggesting release liner, carrier and adhesive gauge variation. At the converter, a “baggy” PSA tape doesn’t track properly through the laminator. Affected areas often become hard wrinkles after passing over machine rolls. “Baggy” material may also result in poor lamination and finished die-cut part.
Possible Causes:
1. Cross-web or down-web thickness variation of release liner, carrier and/or adhesive coatings.
2. Subtle finished product thickness changes after combining individual material components.
3. Factors of PSA coating, lamination and roll-winding processes that may result in “baggy” material.
Possible Solutions:
1. Evaluate thickness consistency of finished product and individual components of subject material. Review findings in-house and with component material vendors.
2. Carefully monitor complete manufacturing process of PSA from component material selection through slitting and shipment of finished product to customer.
3. For converting difficult material combinations, a thicker, stiffer liner may process through lamination and die-cutting with fewer problems (i.e.: 12-Pt. Board or 80# SCK versus 60# SCK-linered products).
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Description: Appearance or adhesive properties of PSA product exhibit significant change since initial purchase or use. A colorless adhesive product (top sample) may turn dark in color or “deaden” under severe conditions (bottom sample).
Possible Causes:
1. PSA exceeded manufacturer’s recommended shelf life (typically one to two years).
2. PSA exposed to extreme temperature, UV light or other environmental conditions.
3. In a converted part, PSA became incompatible with substrate over time.
4. PSA manufactured without adequate preservative.
Possible Solutions:
1. Plan to use PSA product prior to expiration of manufacturer’s recommended shelf life.
2. Store PSA product per manufacturer’s recommendations.Avoid direct UV exposure.
3. Prepare prototype parts and predict compatibility using accelerated aging studies.
4. Contact PSA manufacturer to confirm that PSA product was manufactured properly.
Description: Converted or unconverted foam tape exhibits pinholes through foam substrate. Often, such pinholes appear at the center of a darker-colored burn mark.
Possible Causes:
1. Pinholes may occur infrequently as part of a foam-based manufacturing process.
2. Pinholes and other physical defects (dimples or dents) may be created as foam-based substrates pass over contaminated equipment drive and idler rolls.
3. Excessive corona treatment, used to improve anchorage of PSAs to the low-energy surfaces of polyethylene, polypropylene and other plastic substrates, may cause pinholes.
Possible Solutions:
1. Inspect suspect raw material closely and review situation with raw material vendor
2. Inspect suspect coated material, equipment drive or idler rolls for sources of contamination and surface defects.
3. Pinholes created by corona treatment may be the result of equipment set-up, process conditions or maintenance. Confirm proper corona treatment set-up and conditions per process specifications. Inspect corona treatment equipment for proper operation.
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Description: Description: Release liner of PSA tape or converted part removes too easily or too soon. In such cases, high waste encountered due to "pre-dispensed" parts and/or dirt contamination.
Possible Causes:
1. Selection of unsuitable PSA/release formulation combination.
2. Selection of unsuitable release liner base stock (type, thickness or flexibility).
3. Selection of unsuitable PSA tape and converted part finishing.
Possible Solutions:
1. Select product with different adhesive/release coating combination to provide proper release performance.
2. For narrow rolls of converted parts, consider using a "tighter" release formulation and a more flexible paper or film-based material.
3. “Too low” release may be affected by the direction of wind, core size and other finishing/packaging factors. Consider such factors along with adhesive and release liner selection early in the product design/selection process.
Poor Release Liner due to Static
Description: Description: PSA roll doesn’t unwind cleanly and the adhesive “splits” between two sides of release liner. Adhesive “splitting” or foam carrier failure may occur in tree-shaped pattern or when adhesive removes from liner with great difficulty. Defect may be confirmed by marking suspect area with large permanent marking pen.
Possible Causes
1. Selection of materials that are susceptible to static, such as polymer films/foams.
2. Selection of high-friction release materials that are prone to static.
3. Low moisture and humidity in the processing area.
4. Material slides over equipment drive/idler rolls, creating static electricity.
Possible Solutions:
1. Be aware of static electricity potential and maintain adequate static control equipment.
2. Be aware of static electricity potential with high-friction liners.
3. Add humidity to facility and/or specific equipment environment.
4. Minimize material slippage through equipment.
Moisture related Tunnels / Wrinkles
Description: Release liner of PSA tape or converted part exhibits small "puckers" or wrinkles. Large, moisture-related air pockets may also form between adhesive and release liner of the PSA tape or converted part.
Possible Causes:
1. Selection of unsuitable adhesive/release liner combination.
2. Selection of unsuitable release liner base material; moisture stability is critical.
3. Inadequate liner remoisturization during PSA tape manufacture.
4. Significant relative humidity fluctuations between PSA manufacture, customer storage and use.
Possible Solutions:
1. Super calendered kraft (SCK) paper liners are less moisture-stable than clay coated kraft (CCK) or polycoated kraft (PCK) paper liners, and polyethylene (PE), polypropylene (PP) and polyester (PET) film liners.
2. Optimize PSA manufacturing processes to produce moisture-stable release liner.
3. Control environmental relative humidity in storage and manufacturing facilities. Protect PSA products from extreme moisture and humidity variations by storing PSA tape and converted parts in “poly” packaging.
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Description: PSA tapes and converted parts may exhibit wrinkles, tunnels or air pockets not directly related to moisture stability issues.Two common defects are hard lamination wrinkles and roll-winding tunnels
Possible Causes:
1. Hard lamination wrinkles may be the result of combined material and process issues – “baggy” raw materials, inconsistent adhesive thickness, tension and lamination operations, adhesive streaks/voids, etc.
2. Roll-winding tunnels may also be the result of combined material and process issues – improper selection of product components including release liners, carrier membranes and adhesives, consistent adhesive coating, lamination and roll-finishing processes.
Possible Solutions:
1. Select PSA tape products manufactured with top-quality, cost-effective raw materials. 2. Ensure that all adhesive coating, lamination and roll-finishing processes are capable of producing defect-free products.
3. Carefully evaluate multiple material components, processing conditions and roll storage combinations to minimize the occurrence of such roll defects.
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Poor Roll Formation: Too Tight
Description: Tension-curled material exhibits down-web curl and tends to “wind itself up” into a small, coreless tape roll. Moisture-curled material (Figure 3B) exhibits cross-web curl and tends to “roll up” into a tube of material. Similarly, heat-sensitive raw materials may shrink and exhibit “cross-web” curl as described above for moisture-related issues.
Possible Causes:
1. Selection of soft, easily-stretched materials such as thin, lightweight foams, LDPE films, polyurethane films and non-woven fabrics.
2. Inconsistent liner remoisturization and tension control of extensible materials during adhesive coating/lamination process.
3. Selection of unsuitable PSA, face stock/carrier and release liner combination. Super calendered kraft (SCK) liners are less moisture-stable than plastic film and polycoated liners. Material Curl—Tension, Shrinkage and Moisture-Related Issues
Possible Solutions:
1. Select product with different combination of release liner, adhesive and face stock/carrier.
2. Optimize tension control and liner remoisturization during adhesive coating, curing and lamination processes to facilitate manufacture of “curl-free” product.
3. Select more moisture-stable liner – polycoated kraft (PCK) or plastic film in place of SCK release liners.
Description: PSA tape or converted part (especially a transparent nameplate or graphic) exhibits excessive bubbles/blisters in cured adhesive coating.
Possible Causes:
1. Selection of unsuitable adhesive/release liner combination.
2. Self-wound tapes may exhibit “mottled” appearance due to entrapped air between tape layers.
3. Adhesive coating process that results in “bubbled” wet and cured coatings.
4. Adhesive curing process that results in “adhesive skinning” and blistering.
Possible Solutions:
1. Heavy adhesive weights on super calendared kraft (SCK) liners often yield “blistered” adhesive coatings. Evaluate polycoated kraft (PCK) or plastic film release liners.
2. “Mottled” appearance may be eliminated by using a product with two liners.
3. Optimize coating processes to apply bubble-free, wet adhesive coatings.
4. Optimize curing processes to ensure bubble-free curing of wet adhesive coatings.
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Material Curl - Tension, Shrinkage, Moisture Related
Description: Tension-curled material exhibits down-web curl and tends to “wind itself up” into a small, coreless tape roll. Moisture-curled material exhibits cross-web curl and tends to “roll up” into a tube of material. Similarly, heat-sensitive raw materials may shrink and exhibit “cross-web” curl as described above for moisture-related issues.
Possible Causes:
1. Selection of soft, easily-stretched materials such as thin, lightweight foams, LDPE films, polyurethane films and non-woven fabrics.
2. Inconsistent liner remoisturization and tension control of extensible materials during adhesive coating/lamination process.
3. Selection of unsuitable PSA, face stock/carrier and release liner combination. Super calendered kraft (SCK) liners are less moisture-stable than plastic film and polycoated liners.
Possible Solutions:
1. Select product with different combination of release liner, adhesive and face stock/carrier.
2. Optimize tension control and liner remoisturization during adhesive coating, curing and lamination processes to facilitate manufacture of “curl-free” product.
3. Select more moisture-stable liner – polycoated kraft (PCK) or plastic film in place of SCK release liners.
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