Most Common Laminating Defects & Origin
Visual Appearance
Name: BUBBLE(s)
English: Bubble(s)
French: Bulle(s)
German: Blase(n)
Spanish: Burbuja(s)
Italian: Bolle
Appearance Description
Spherical pockets of air/volatiles at the glass PVB interface or inside the PVB
May coalesce to from “worms” or “sunbursts” (especially under warm ambient conditions)
Distinction Methods
These spherical pockets can NOT be moved by pressure of fingers
Possible Cause(s)
Possible cause(s) in the process
Inadequate de-airing
PVB: PVB surface pattern too smooth
Sheet deformation: last wraps of
the refrigerated roll
PVB caliper variation
Nip rollers: Roller speed too high (no edge seal)
Lack of low speeds at the trailing edge
(no edge seal)
PVB temperature too low (no edge seal)
Trailing edge temperature too high
(premature edge seal)
Vacuum: Vacuum too low
Bending imperfection (lack of
Parallelism of glasses)
Cold vacuum time too short
PVB folded over glass edge in vacuum
ring (preventing air flow)
Premature edge seal due to too smooth
PVB surface roughness or bending
Imperfection
Vacuum bag or ring too hot at vacuum
start.
Glass to hot at vacuum start (< 25 °C)
Visual Appearance
Name: AIR POCKET(s)
English: Air Pocket(s)
French: Poche(s) d’air
German: Lufttasche
Spanish: Bolsa(s) de aire
Italian: sacche d’aria
Appearance Description
Large amount of air/volatiles at the glass/PVB interface.
The shape might be “worm”-like or “sunburst” like.
Distinction Methods
These air pockets can NOT be moved by pressure of fingers
Possible Cause(s)
Possible cause(s) in the process
Inadequate de-airing
See “Bubbles”
Bending imperfection (lack of
Parallelism of glasses)
PVB ripples (pie crust — table cloth)
Glass caliper variation
Bubble/delamination formation
Some air will be dissolved in the PVB layer.
When large in amount or when laminated glass (PVB) is under warm conditions (softening of PVB) these “micro bubbles” will grow and coalesce into “worm” or “finger”-like delamination and ultimately into “sunburst” delamination.
A spherical shape bubble can “support’ a high internal pressure (needed to form and come out of solution), but wants to relief that pressure. Due to the sunburst shape (very large contact area between volatile and PVB) this pressure is released significantly. Ambient temperature (softness of PVB) will influence the speed of this phenomenon. Often small glass chips are found to be a nucleus for the air bubble to grow around.
Visual Appearance
Name: (EDGE)-FOAM
English: Foam
French: mousse
German: Schaum
Spanish: Espuma
Italian: Schumma
Appearance Description
Large number of very small bubbles along all or some of the autoclave edges.
Distinction Methods
This foam is only visible at the autoclave edges, approximately till 2 cm inwards.
Possible Cause(s)
Possible cause(s) in the process
PVB too soft (warm) at autoclave pressure release
Autoclave pressure release at too high temperature (> 50 degrees C)
Visual Appearance
Name: EDGE-BUBBLE(s)
English: Edge bubble(s)
French: Bullage périphérique
German: Kanten Blasen
Spanish: Burbujas al borde
Italian: Bolle di bordo
Appearance Description
Spherical pockets of air at the glass/PVB interface or inside de PVB. At th glass/PVB edges:
Automotive regulation:
Europe (ECE R43): 2 cm
USA (ANSI Z26): ½ inch = 1.25 cm
Japan & Korea (JIS & KS): 1 cm
Distinction Methods
These bubbles can NOT be moved by pressure of fingers
Possible Cause(s)
Possible cause(s) in the process
Inadequate (or Immature) edge seal.
Distinction between premature and immature edge seal:
(Transparent) edge seal reaching the glass edge and showing a well defined and linear contact line at the inside of the edge seal. PREMATURE
(Transparent) edge seal not reaching the glass edge and showing a very irregular contact line at the inside of the glass seal. IMMATURE
Nip Rolls: Roll speed too high
PVB temperature too low (2nd nip)
causing the edge seal not reaching
the glass edge.
Bending imperfection(s)
(gap > 0.1 mm/50 mm)
Vacuum: PVB surface too rough
PVB not hot enough for enough time
Bending imperfection(s)
(gap > 0.1 mm/50 mm)
Visual Appearance
Name: BLOW-IN(s)
English: Blow-in(s)
French: Intrusion d’air
German: Einbuchtung(en)
Spanish: Burbujas abiertas
Italian: Sigillatura non completa
Appearance Description
Defect at the edge where no bond between glass and PVB is apparent.
The defect is interfacial (Glass/PVB) and has lack of contact only to one glass interface.
Distinction Methods
The defect is visible when the laminate exits the autoclave.
Possible Cause(s)
Possible cause(s) in the process
Lack of adequate edge seal prior to autoclaving.
(compressed air from the autoclave penetrates the non complete edge seal) and “nests” in between glass and soft PVB.
Nip Rolls: Roll speed too high
PVB temperature too low (2nd nip)
causing the edge seal not reaching
the glass edge.
Bending imperfection(s)
(gap > 0.1 mm/50 mm)
Vacuum: PVB surface too rough
PVB not hot enough for enough time
Bending imperfection(s)
(gap > 0.1 mm/50 mm)
Visual Appearance
Name: LACK OF LAMINATION
English: Lack of lamination
French: Absence de lamination
German: Unzureichende Laminierung
Spanish: Falta de laminacion
Italian: Mancanza di laminazione
Appearance Description
Incomplete bonding between PVB and glass. Residual surface pattern of PVB remains visible.
The defect is visible upon exiting the autoclave.
Distinction Methods
The residual surface pattern is visible (not to be confused with (liquid) surface contamination).
Possible Cause(s)
Possible cause(s) in the process
PVB did not contact the glass during the prepress operation.
Trapped too much air.
Pocket is the bent glass pair (bending imperfection).
Fold or crease in the PVB sheeting.
Uneven thinning of the PVB (pulling PVB with excess force prior to assembly).
Roll speed too high (trailing edge)
NOTE: the autoclave cycle influences the
visibility/appearance but is NOT the
cause of the problem.
In-complete Edge seal
Lack of lamination
Visual Appearance
Name: SHORT VINYL
English: Short Vinyl
French: Retrait
German: Umgeschrumpfte
Folien
Spanish: Encogimiento
Italian: Ritiro/Mancanza plastica
Appearance Description
Area’s along the laminate edge with no PVB between the glass pair. Highest risk in PVB extrusion direction, visible at or after prepress operation. Some short vinyl is only visible after autoclaving (see autoclave short vinyl).
Distinction Methods
Short vinyl is visible prior to autoclaving.
Possible Cause(s)
Possible cause(s) in the process
Poor “tacking” of PVB to glass at assembly.
Excessive PVB shrinkage.
NOTE: The PVB trim procedure can help to reduce the shrinkage incidents.
Too large temperature difference between glass and PVB.
Glass temperature: too high: induces PVB shrinkage (results in short vinyl) but increases PVB tackiness (adhesion at room temperature).
Too low: no tack, but shrinkage possible during heat up of the glass.
Glass temperature too warm at lay up (> 35 degrees C), but below the PVB tack temperature.
Bending gaps between glass pairs at the edges.
Too much parting agent left on the glass (prior to assembly).
Long and shaky conveyor to the vacuum bag line or nIp roller.
PVB stretched too cold ( < 90 degrees C)
Sudden temperature increase of the glass without PVB tack.
Due to induced shrinkage at unwinding:
Partial blocked PVB roll
Large distance between the PVB roll and the pulling force.
Visual Appearance
Name: AUTOCLAVE SHORT VINYL
English: Autoclave Short Vinyl
French: Retrait en autoclave
German: Eingeschrumpfte
Folien nach dem Autoklave
Spanish: Encogimiento en el autoclave
Italian: Ritiro en autoclave
Appearance Description
· Tear drop like vacuoles emanating from the laminate edge.
· If less than 3 or 4 mm, the appearance might be very similar to regular short vinyl.
· Visible only AFTER autoclave.
Distinction Methods
Autoclave short vinyl is only visible AFTER autoclaving, at the edge one can notice PVB is in contact to BOTH glasses.
Possible Cause(s)
Possible cause(s) in the process
PVB flows to fill the gap between bent glasses during autoclaving.
CONTRIBUTORS:
· Autoclave temperature
· Single lite bending (automotive)
· NOTE: If the autoclave short vinyl is less then 3–4 mm, it appears linear (no vacuoles) and the PVB sticks to one glass lite only.
Gaps due to bending imperfections or glass mismatch.
Distinction mehod between autoclave short vinyl and blow-ins:
· The vacuoles are situated INSIDE the PVB (not at the PVB/glass interface).
· The tear drop like vacuoles are connected by smaller vacuoles and usually a gap between the glass lites is noticed.
Visual Appearance
Name: DELAMINATION
English: Delamination
French: Délamination
German: Delamination/Ablösung
Spanish: Delaminación
Italian: Delaminazione
Appearance Description
Failure of the PVB/Glass bond AFTER it was formed.
IMPORTANT: The adhesive bond between PVB and glass must be formed before delamination can occur (if not see: Lack of Lamination)
Distinction Methods
Delamination (regardless the shape) can be changed in shape under pressure. (but no surface structure is visible; large sunburst delaminations show a defect growth pattern (nucleus).
Possible Cause(s)
Possible cause(s) in the process
In view of the complexity delaminations will be split into:
· Edge delamination
· Worm or Finger delamination
· Sunburst delamination
· Snow flake delamination
A weak PVB/Glass bond and/or stress in the laminate.
Visual Appearance
Name: EDGE DELAMINATION
English: Edge Delamination
French: Délamination Périphérique
German: Kantendelamination
Spanish: Delaminación a los bordes
Italian: Delaminazione/Zampe di Gallina
Appearance Description
Failure of the PVB/Glass bond is at the edge of the laminate.
The failure extends (over a short time) along the edge of the laminate.
Distinction Methods
Delamination (regardless the shape) can be changed in shape under pressure. (but no surface structure is visible; large sunburst delaminations show a defect growth pattern (nucleus).
Possible Cause(s)
Possible cause(s) in the process
PVB expands and contracts upon sequential exposure to moisture (or swelling agents) and drying
CONTIBUTING FACTORS:
· Seasonal and diurnal changes in temperature and relative humidity.
· Storage environment of laminates (the warmer the PVB the softer – the softer, the more prone to delaminations – especially the first days after autoclaving).
Visual Appearance
Name: “WORM” or “FINGER” DELAMINATION
English: “Worm” or “Finger” Delamination
French: Délamination vermiforme
German: Wurmartige Delamination
Spanish: Delaminación Gusano
Italian: Zampe di Gallina
Appearance Description
· The growth of the PVB/Glass bond failure in “dendritic” formation.
· Some appear immediately after autoclaving, others days after autoclaving.
· Some disappear or vary with time.
Distinction Methods
Delamination can be changed in shape under pressure.
Possible Cause(s)
Possible cause(s) in the process
Weak PVB/Glass bond
AND
Stress in the laminate.
Air and glass gap defects can increase the risk for worm delamination
· The glass periphery is often under stress
· The adhesive bond near the defect might be weak.
· It is critical to determine the root cause.
A spherical bubble is the physical shape that can contain the highest internal pressure. But it wants to release this pressure. A worm/finger/sunburst shape can release this pressure by ensuring a large contact area between volatile and medium (PVB).
WEAK PVB/GLASS BOND:
– High PVB moisture
- Already in the PVB sheeting through
conditioning problem.
- Through water injection in the
autoclave (malfunctioning air dryer).
– Residual ions on the glass.
– Low autoclave temperature ( < 125° C).
– Inadequate holding time at maximum autoclave temperature.
– Low as made PVB adhesion.
– Removal of glass with extruded PVB attached to the autoclave support.
– Large amount of volatiles vaporizing at once: Moisture , swelling agents,...).
– NOTE: PVB flows to reduce stresses:
* PVB flows when the laminate is
in a hot environment.
* High PVB moisture enhances
the flow.
Large glass gap (0.2 mm over 5 cm) -Thick automotive glass (3 mm)
Visual Appearance
Name: “SUNBURST” DELAMINATION
English: “Sunburts” Delamination
French: Délamination “tournesol”
German: “Sonnenblume” Delamination
Spanish: Delaminación “Girasol’
Italian: Delaminazione ritardata
Appearance Description
· Circular area where the PVB/Glass bond has failed.
· Occurs usually away from the glass edges
Distinction Methods
The delamination area can be reduced by pressing with fingers, unless there is a large amount of air inside ((Sunburst delamination still incomplete).
Possible Cause(s)
Possible cause(s) in the process
Weak PVB/Glass bond
AND
Stress in the laminate.
Large amount of trapped air and/or volatiles.
A spherical bubble is the physical shape that can contain the highest internal pressure. But it wants to release this pressure. A “sunburst” shape can release this pressure by ensuring a large contact area between volatile and medium (PVB).
NOTE: The difference between bubbles, air pockets and delamination is the pressure inside the defect.
· Bending gap
· Premature Edge seal
· Locally wet PVB
· Locally trapped air
· Fish eyes or bulls eyes
The difference in shape is due to the location of the delamination.
The first picture delamination is in between PVB and glass;
the second picture delamination is in between regular and acoustic (softer) PVB layer (tri-layer acoustic PVB has a soft PVB core layer and 2 regular PVB layers at each side).
Visual Appearance
Name: DELAMINATION by water entrapment
English: Water Delamination
French: Délamination “penetration d’eau”
German: “wasser penetration” Delamination
Spanish: Delaminación “agua’
Italian: Delaminazione
Appearance Description
· Circular area where the PVB/Glass bond has failed and area is white .
· Typical sunburst appearance around the white area.
Distinction Methods
The delamination area looks white.
Possible Cause(s)
Possible cause(s) in the process
Weak PVB/Glass bond due to moisture/water penetration in the PVB, reducing the initial adhesion.
Water replaces the plasticizer (“Phase separation”) and turns PVB into milky white color.
PVB turns white (but can be dried to become transparent again) around 1 % water content.
As of 1.5 % moisture content the white color (phase separation) is premanent and irreversible.
Continuous exposure of laminated glass edge to water or high ambient humidity.
NOTE:
Compatibility problems between silicones/sealants and PVB are not reviewed in this document.
Nor are the excessive use of primers/cleaning products when gluing glass on an aluminium frame (Structural Sealant glazing) or bad installation (none or inadequate draining).
This information corresponds to our current knowledge on this subject. It is offered solely to provide possible suggestions for your own experiments. It is not intended, however, to substitute for any testing you may need to conduct to determine for yourself the suitability of our advice for your particular purposes.
