Glass Washing

The temperature and cleanliness are very important factors to produce high quality laminated glasses. If have impurities on glass sheet or PVB film that will not only affect appearance of the laminated glass but also broken their adhesion properties, impurities on glass surface causes delamination, unglued and low bond strength. Probably Spot-liked delamination and low bond strength be caused by uncleanly glass sheets or PVB interlayer.

Before laminating, washing and cleaning glass purpose is to remove residual contaminants. The quality of washing water has a great influence on the adhesion between glass and PVB interlayer, because water conductivity has influence bond force on laminated glass. If there has drop of water or residual water on glass sheet after washing and cleaning, water itself can be considered as contaminants.

Water quality will affect bonding properties of glass sheets and PVB interlayer, such as water hardness, metallic ions, PH value, as shown in Figure below.

Water hardness, metallic ions, PH value which all elements was changed by water resource, different area have their quality of water, better to use deionized water or pure water to washing glass. Washing machine consisted of washing and drying sections. First wash is best to use 40-60 ℃ common water plus overflowed water from back, in order to remove some spots, like oil stains, perspiration or fingerprints etc; Second wash is same as first wash in order to strengthen and ensure cleaning effect; Ca +, Mg + will remain on glass after drying, this will caused lower bond strength and safety performance, so generally use ion systems or reverse osmosis system to remove salinity. Water conductivity value or hardness value increase means salinity is higher, so water for washing laminated glass should use pure water which must have lower saly, and resistivity > 100MΩ or conductivity < 10μs. Drying sections used air-knife or nozzle to blow off. Temperature and transfer speed of glass affects water evaporation. When water is blown away while salinity along with, so that improve adhesion.

In production of laminating processing, bent glass or tempered glass can not use washing machine to wash glass, it need to clean by hand to clear impurities away from glass surface, in order to ensure quality and performances of laminated glass. When laminating must consider suitable temperature, not too low nor too high; to ensure that there has stickiness between glass and PVB interlayer, which stickiness makes PVB interlayer to move freely in order to maintain its correct position. Refer to experience value of glass surface temperature between 21 ~ 35 ℃, too low temperature will move PVB interlayer and appear folds; too high temperature will cause shrinkage, folding, but also cause earlier edge sealing, that is one reason to result in air bubbles, if temperature is too high will result in hard to change position of PVB film.

Conditions of laminating operation room

laminating operation room is a place where can store upcoming PVB interlayer and can lay PVB interlayer on the glass. The laminating operation room needs strict requirements; it should reach one million grade pure requirements, in order to ensure humidity and temperature in operation room, should be equipped with air condition and dehumidifier to keep constant temperature and humidity requirements, in laminating should pay special attention to PVB interlayer storage and clean environment, hair, clothing fabric, together, if the control is lax, there will be hair from the operator, clothing fabric, dust and contamination from operators, those details directly influence on performance and quality of laminated glass, so for producing high quality laminated glass the laminating operation room

should do the followings:

• Air-shower room with double doors, ensure cleanliness at laminating working place.
• Provides filtered fresh air to make laminating operation room has positive pressure, to prevent moist air come into room.
• Temperature should be controlled between 20 ~ 25 ℃, relative humidity is controlled at 23% ~ 28%.
• Operators should wear special non-cotton clothes, hair can’t be exposed, wear cotton-free gloves.

PVB film putting and trimming

The washed and dried laminated glass entered operation room have to be stored in suitable environment of clean, constant temperature and humidity room, in order to improve production efficiency and reduce costs, can be made required size of PVB interlayer for further using, this way can short time to laminating, as soon as glass sheet is out then can put PVB film on glass to laminating immediately. Glass is transmitted through transfer station to the right place, suction cup will suck up one lite until PVB interlayer is already putted on below another lite correctly; transfer bench has liftable caster even if glass isn’t in appropriate position that can also be adjusted by caster. How to put and trim PVB film as well as important in laminating working room.

Improper putting operation will cause defects of laminated glass. The main defects shows wrinkle, pattern dislocation and shrinkable. If happens above defects that have serious quality problems in subsequent delamination, low bonding and during processing in autoclave and resulting in final product quality of laminated glass, it must be very careful to put film on glass flat without any impurity in it.

The other important processing is trimming PVB film before enter to roll-heating section or vacuum processing, When trimming, PVB interlayer can not be extended overly stretch otherwise it will lead to reduction of its thickness, resulting in PVB film returns back rapidly and air be blow into laminated glass as air bubbles when is rolling processing, try to trim PVB film edge and close to glass, according to experience value is about 5mm.

Rolling deair and laminating

After PVB interlayer was laminated by two glass sheets which are ready for deairing and laminating, the processing of deairing and laminating stages are most important in quality and performance of laminated glass, it’s also important part of finished laminated glass quality and yields.

According to process requirements, laminator combines heating furnaces and pressing rollers, heating furnaces may be electric heating, infrared heating or hot air heating, according to glass and PVB interlayer absorbing performance, infrared heating is ideal, either chinese equipment or imported equipment are generally chosen infrared heating. Pressing roller is generally cylindrical, it can be reached purposes through heating and rolling as followings:

• To remove residual air between glass and PVB interlayer;
• To avoid separate from glass and PVB interlayer enter into autoclave when is preheating treatment;
• Edge should be sealed, avoid stain or air into laminated glass trough heating and pressuring in autoclave. Although PVB film itself can be dissolved in a certain amount of air, the amount of air is less compare with of total air between glass and PVB interlayer. At ambient conditions of 25 ℃, 1 atm, solubility of air in PVB interlayer film is 6% by volume, this solubility can only absorb and dissolve inner surface texture air between glass and PVB interlayer. It can not be absorbed and dissolved total air in laminated glass, must expel all air in order to make PVB interlayer bonded with glass strongly. Uneven thickness of all PVB interlayer can cause air exist in laminated glass and must expel through roller pressing in laminator. For architectural flat laminated glass, roller is usually made with rubber-metal shaft.

Only expel air is not enough, if didn’t have a certain cohesion, probably happen delamination, there must be a certain temperature to make the glass bonded together with a PVB interlayer, and make sure gets good sealed, so like this the air will not be returned. If has worse edge sealing the air will invade laminated glass to makes air bubbles in edge and delamination. The temperature can not be too high, can not seal edge too earlier before deairing, once edge was sealed, the air can not be expelled from laminated glass anymore. If residual air is more than solubility of air in PVB interlayer, it will happen air bubbles after produced in final product. For above reasons, in procedure of roller pressing and laminating, temperature, speed, pressure and other parameters must be strictly controlled. Picture shows a schematic diagram of roller pressing.

Because it involves the pressure, temperature, speed and other parameters, to accurately determine roller pressing, expelling , bonding and edge sealing conditions that have certain degree of difficulty. The key technical processing is roller pressing and deair in laminating that achieved without bubbles and without edge defects, the most key technics related with roller pressing force, temperature and line speed of glass and PVB interlayer film, also other factors effect of deair performance, these factors are not easily controlled including flow-ability of PVB interlayer, moisture, roughness and alignment of glass sheet, colors, varieties, specifications and so on. Two glass dislocation will increase air content and in difficult processing of roller pressing. Different color, varieties,specifications of glass will change heating absorption in furnaces, thereby changing temperature of glass surface, so have to sum up experiences of different types of glass in order to provide accurate reference data for future production.

A furnaces with two set of rollers.

This processing is only for common flat laminated glass production, shown as picture, in environmental temperature, first should be roll-pressed for laminated glass, then heating and following rolling pass, this kind machine for deairing and edge sealing are done through second sets of rolling. In order to achieve success in deairing and sealing under first rolling-pass, glass surface temperature should be controlled as well, recommend glass surface temperature within 64 ~ 71 ℃ generally when before enter to second roller pressing.

This process is used for quantity production line in laminated glass, most manufacturers are using this production line, Picture shows two furnaces with two sets of roller pressings section, both laminators purpose are deairing and edge sealing independently, first laminator is mainly deairing, second laminator is different with first laminator in temperature only. First lamintor will heat glass surface up to 35 ℃, then trough first set of rolling to deair, pressure 0.25 ~ 0.5Mpa, roller gap is 10% less than total glasses thickness; To maximize deairing, first furnace temperature is very important, if temperature is too high, glass surface temperature is higher after pressing, the air didn’t exhaust before edge sealing, air stay inside and hard to die; if temperature is too low, the air in laminated glass which can not be exhausted will exist bubbles in further process, so it is necessary to strictly control the temperature of first laminator. When enter to second laminator to process edge sealing, its temperature better to keep 70 ± 5℃ and pressure 0.55 ~ 0.75Mpa, roller gap is 15-20% less than total glasses thickness, roll degassing process reference parameters are shown in table

Appearance judgment of pre-pressing processing

Three criteria to judge deair and edge sealing in good are appearance after pre-pressing, boiling and finish laminated glass appearance; last two is important but found after laminator, so that caused batch of product quality problems. Try to avoid loss should be checked in processing of deair and pressing and adjust parameters in time if find any defects. Therefore, laminated glass processing required people who has more experiences to perform, visual inspection should include following aspects:

(1) Deairing

From out from first furnace (before rolling), laminated glass should be uniform color and fuzzy, any clear areas possibly is hot spots (tape) or in contact with heat transfer station, These may have been completely sealed, so dressing materials on insulating heat transport table, it can improve temperature is even of laminated glass.

When laminated glass through first roller, may see the air waves discharged from edge slowly, then glass trailing edge must be separated, it help bubbles escape. When laminated glass is out from first laminator, glass is almost clear but at edge is clear, If saw dark or fuzzy bubbles in, it indicates that no air was out yet, especially at afterbody. So need to pressing continuously in order to make even transparent laminated glass.

(2) Edge Sealing

Laminated glass passed two lamintors will become more transparent and have clear edge, around 5 ~ 25mm completely transparent and extends to inside of laminated glass. If wasn’t sealed which means air into laminated glass during processing of autoclave.In general, higher temperature, stronger pressing force or slow speed can get a better edge sealing effects.

In processing of laminating, possible will happen fuzzy region, if so, it can not be disappeared neither, because air once into laminated glass and hard to escape even through high temperature and pressure processing, it usually uses method of vacuum deairing to remedy it.

Vacuum deairing

(1) The use of vacuum degassing and requirements

Vacuum degassing process is to solve bending laminated glass, curved tempered laminated glass, multiple laminated glass, this processing is a effective method to solve imperfected edge sealing after rolling. For automobile windshield that is kind of bending laminated glass, mainly use to air circulation.

The production condition of vacuum deairing is almost same as rolling. Deair effects is considering as air bubbles in laminated glass after high temperature and pressure, judge to good laminated glass should following tests of boiling and heating processing, after laminated glass was out, then make a decision; Because of pre-pressing effects is correlated with quality of finish product, so check or control daily production, pre-pressing appearance is known after deairing, if find appearance defects immediately to correct action in processing and can be take to correspond.

Since a amount of residual air can change transparency, it is usually based on degree of glass and edge transparency to and edge judge quality of deairing processing. Between glass and PVB interlayer has more air, while laminated glass appearance is more foggy after initial pressing. Visually speaking, use of vacuum deairing method is more transparent than rolling.

Vacuum deairing production process is mainly used in special laminated glass which is a combination of size and form can not be used the way of roller to deairing sometimes. Normally vacuum deairing bag will be installed in close of production line, and connecting with vacuum source to degassing at room temperature. The most important is to ensure that vacuum pipe is not deformed when vacuum degassing. After vacuuming, vacuum port should be closed and vacuum bag separated from vacuum pump. Cumulative laminated glass should be put on autoclave cart is ready into autoclave under high temperature and strong pressure.

(2) (2) Key processing factors of vacuum degassing

Key processing factors of vacuum degassing are glass sheet and PVB film temperature, degree of vacuum, vacuum time, and maximum temperature of glass sheets.

(a) Starting temperatureStarting temperature

When start to laminating, PVB film is take from Laminating glass room where has lower temperature while PVB film surface has less changes of roughness, it can be deair as much as possible; to prevent dislocation between glass sheets and PVB interlayer in laminating, so it need to adhesive between glass sheet and PVB film, that’s why temperature must be appropriate to balance these needs. Laminated glass surface temperature is room temperature, when meet thicker lites or mutilayer lites, these laminated glass are relatively heavy and have strong press to PVB interlayer film, it is recommended use lower temperature films and operation room temperature should keep 20 ~ 25 ℃. Vacuum degassing usually operates at room temperature.

(b) Degree of vacuum

Vacuum degree guaranteed all the air be exhaust, minimum requirements of vacuum is -0.08MPa, it be able to have an ideal result, piston and rotary vane vacuum pump can be achieved.

(c) Vacuum time

The most important is to ensure that have enough time to deair completely, vacuum pressure should be stable. Install vacuum device at vacuum connector and another end of laminated glass that can show degassing effect. 10 ~ 30min vacuum pumping is enough, but vacuum time is relative with glass design, shape, equipment, and stability of vacuum, the effect of vacuum is adjusted according to actual production. If still deairing in autoclave, the vacuum time is according to autoclave working time, the time is usually longer than heat vacuum time. If vacuum processing before into autoclave, the maximum heating temperature is maintained at 95 ~ 110 ℃. If cooling rate is slow, should use lower temperatures,;on the contrary， high cooling rate can be used a higher temperature. As total thickness of laminated glass exceeds 18mm, should be maintained at the highest temperature of 15min or more. If still been heat vacuum processing in autoclave, the maximum temperature of heat vacuum should meet autoclave parameters, the maximum temperature of autoclave can reach upto 140 ℃.

laminated glass processing in autoclave

(1) The purpose of autoclave processing

Autoclave processing is last step of Laminated glass also is a very important stage,it given a suitable temperature, pressure and time, through this processing have following effects:

• Solve residual air in deair processing;
• Make PVB interlayer has fluidity, finally can be boned with PVB interlayer and glass bonded together firmly;
• Prevent heat conduction to penetrate into edge and inside of laminated glass.

Through heating, pressurization, suitable time, laminated glass have good transparency and excellent safety performances. After deairing, roller pressing, or after vacuum, it should be sent directly to autoclave as soon as possible, if delay too long time then into autoclave to process, PVB film didn’t have fluidity to course PVB film can not bond with glass sheet as well, because of roller pressing required temperature not too high. The laminated glass not promptly into autoclave after roller-pressing, it may cause delamiation.

Laminated glass should load in autoclave cart, and spaced apart from each laminated glass sheet. It ensures that both sides of each laminated glass sheet be able to get uniform force in autoclave processing. Sometimes In order to increase adhesion between glass sheets and PVB interlayer to bonded together firmly, it used clip to fix at edge of laminated glass This way willl make PVB film get thinner and avoid delamination.

(2) Theory of autoclave processing

As amorphous polymer of PVB interlayer, it is the viscoelastic materials at low temperature, while at high temperatures it has a flow-ability properties. This material has a certain temperature range, also with elastic memory properties, there is a kind strength to stop its elastic deformation; and viscous resistance is desirable to move past each other chain polymer molecules permanently to maintain this deformation. One object of laminated glass to give heat pressing treatment and temperature, so that permanently maintain PVB interlayer film has flow-ability, and with good adhesion between glass surface and PVB film.

In autoclave, the heat spread to laminated glass by flowed air and heat radiation, transmitted through glass to PVB interlayer; conduction time depends on PVB film which required time of viscous flow. Reached equilibration temperature of PVB film required time that depends on total thickness of laminated glass as shown in picture, the thicker laminated glass need longer time to reach temperature equilibrium.

(3) Heat-pressing processing in autoclave

Laminated glass autoclaving determined viscous flow control and resolution of residual air in laminated glass, before autoclaving, should be properly controlled residual gas and deair between PVB interlayer and glass sheet, if temperature, pressure and time is appropriate, it can dissolve remaining air into PVB interlayer film and keep it in stage of heat-pressing processing in autoclave. In addition, must prevent heat conduction from like air or oil stain to infiltrate laminated glass when process in autoclave. Picture shows temperature, pressure and time ranges of common laminated glass in processing autoclave, for thicker laminated glass unit need longer dwell time and pressure.

Autoclave processing including three phases are heating, insulation and cooling, each step has its temperature and pressure.

1. Heating

Heating phases within its limitative time, temperature and pressure reached 135 ~ 140 ℃ and 11 ~ 14MPa. In order to produce high quality laminated glass, heat and pressure treatment must be synchronized in autoclave, if make pressure too fast, air or oil stain penetration may cause poor sealing of laminated glass. Contrary pressure is too slow (temperature increase exceeds pressure time), residual air will expand cause delamination or infiltration. Pressure rate is generally 0.06MPa / min, then heating rate is 5 ℃ / min.

2. Insulation

Once temperature and pressure of autoclave reached requirements conditions, it must be maintained for a while, wait PVB interlayer changed as viscous material, Single laminated glass holding time is 10 ~ 25min, Insulation time depends on composition of laminated glass. Such as glass lites and thickness. For example like bulletproof glass structure 5G + 1.52PVB + 12G + 1.52PVB + 5G, the total thickness is 25.04mm, in order to reach temperature equilibrium and viscous flow that need long time; if short, PVB film has low temperature that can not bond with glass as well, it will lead to delamination, poor light transmission and other defects, Picture shows Influence of equilibrium temperature for adhesion in laminated glass.

3. Cooling

Before cooling, firstly should reduce temperature and pressure to predetermined value, main factor of cooling time controlling is cooling capacity and laminated glass quantities in autoclave, Normally cooling time is 25 ~ 35min, decompression until temperature must be reduced below 54 ℃ in autoclave , will certainly be appeared air bubbles in laminated glass.

The above complete cycle for each step, time around 55 ~ 80min. Time depends on equipment and thickness of laminated glass, If autoclave pressure time more than recommended time (Correct Autoclave operation), Please check thermal conductivity of the autoclave is impeded, or equipment heating and cooling system is defected, it need to repair autoclave, read instruction to maintaining autoclave and laminating glass production line.

Delamination

(1) Delamination means glass and PVB interlayer is disengaged that appeared after installation of laminated glass, Delamination type have many shapes as sun-like, photokinesis, finger-like, or edge delamination.

(2) Reasons of Delamination

• PVB film becomes thin: Due to improper loading method, use extra power clips.
• The degree of matching glass is unsuitable.
• Laminated glass with oil stain, detergent, moisture in it, it was causing PVB film does not bond firmly.
• Due to moisture in autoclave, causing PVB interlayer exist moisture.
• Storage environment has high humidity to cause a little bit higher moisture in PVB interlayer film for production, there is extra moisture hard to out from PVB film in production.

(3) Solutions of Delamination

• Improve loading method, keep laminated glasses in vertical direction with certain gap between glasses and have suitable anchor before autoclave, laminating and sealing should be better, do not use too strong clip to improve yield which will cause PVB interlayer get thinner, laminated glass are easy to happen delamination.
• )Tempered glass has deformated that not flat perfectly , for flatness, caved, wave parameter of laminated tempered glass need strict requirements. For deformitied glass which can not be improved glass, pay more attention in production to process in pair, ensure same deformation glass to make up, if necessary could increased thickness of PVB to protect delamination.
• The glass should be washed before laminating, must dry off then lay PVB film on clean glass, required standard of cleanness, temperature and humidity in glass lamination room in order to ensure the co-process for laminated glass sheet without any contamination.
• If find delamination appears to edge of laminated glass and test moisture is higher, it may be determined autoclave has moisture, should check resource of water, be sure to ensur autoclave was dried.
• PVB film storage environment is controlled, must be tested moisture before production, make sure moisture is qualified of laminating.

Air Bubbles

(1) Air or other volatile gases be existed in middle or edge or other places in laminated glass.

(2) Reasons of Air Bubbles

• Poor function of exhaust, incorrect speed of rolling, temperature is too high or low of rolling.
• Pattern is smooth of PVB interlayer.

(3) Solutions of air bubbles

• Adjusting parameters of rolling machine, improve effects in deaering and sealing.
• Choose suitable pattern to de-air.

bubble bag

(1) phenomenon of bubble bags

Air bags were appeared on surface of laminated glass, big or small irregularly existed anywhere like center or edge of laminated glass, most time occurs just out of autoclave, sometimes can seen lines of PVB film.

(2) Reason of bubble bags

• There is fold difference or gap between paired glass sheets.
• There are impurities or glass scraps on surface of glass sheets or on PVB film.
• There are dents or bulges in glass sheets or PVB film.

(3) Solution of bubble bags

• There is fold difference or gap between paired glass sheets.
• There are impurities or glass scraps on surface of glass sheets or on PVB film.
• There are dents or bulges in glass sheets or PVB film.

Air break

(1) Phenomenon

It appears edge region of laminated glass, there is unbonded place between glass sheet and PVB interlayer. This phenomenon is almost similar with delamination, but it appeared when out autoclave, however delamination phenomenon is not exist just out of autoclave. Typical defects of airbroken see pictures.

(2) Reasons

• Seal processing is not well done before into autoclave, it rolls fast at time of roller pressing. Lower temperature, shorter time of vacuum deairing, or vacuum degassing is not enough, air can not be draw out.
• When it comes into autoclave that treat with high temperature and pressure, temperature rises too slow or pressure rises too fast can cause air into laminated glass.

(3) Solutions

• Improve parameters during stages of heating and vacuum processes, and improve seal effects before into autoclave.
• Check graphs direction of autoclave temperature and pressure, ensure that temperature rise to around 65℃ then start to increase pressure; when temperature dropped below 54℃ release pressure.

Empty film in edge of laminated glass

(1) Phenomenon

It happens no PVB film in border region between two pieces of glass and PVB film when deairing in prepressing or after, and happens after high temperature and pressure treatment.

(2) Reasons

• If it happens after pre-pressure and deairing, probably PVB film was placed unsuitable position on glass sheet as dislocation. PVB film trimming is too short to close edge of glass sheet, so that PVB film shrink over.
• ) If it happened after high temperature and pressure, caused by edge of PVB film is fluid under high temperature in autoclave.

(3) Solutions

• Make accurate lamination place of PVB film and glass sheet, repair and correct temperature and pressure monitor, note no any dislocation and PVB film edge keep at 5mm when is trimming, consider as PVB film will shrink so that trimming margin isn’t too short.
• Check temperature controlled procedures of autoclave, calibrate temperature its probe, the autoclave temperature not exceed than 150 ℃.

Bond strength

(1) Phenomenon: bond strength decline

(2) Reasons

• The moisture of laminated glass is higher than standard moisture content.
• The glass surface remains salinity, detergent or not clean enough.
• Float glass direction is wrong, PVB interlayer film surface comes into contact with “Tin surface” of float glass“” , SGP interlayer film is opposite.
• In autoclave processing, thermocompression is incorrect, the laminating result is not good between glass and PVB film.
• The PVB film or glass was contaminated, perhaps PVB size is not suitable.
• Adhesive strength test are changed.

(3) Solutions

• Low bond strength of laminated glass will cause delamination, bond strength is preferably maintained at 4 to 6 units of the bond range, changeable in bond strength that usually due to moisture of PVB interlayer film, therefore, the first step should check moisture content of PVB sample, if moisture out of standard range, if moisture not in range after test, then remove necessary reasons of moisture drift.
• Check the washing machine and pure water, check the performance of cleaning machine and production records, the speed of washing machines and air-dried system changes will affect bond strength of the laminated glass, whether judge washing machine should be repaired or maintained, and finally step should check hardness of water which wash glass, water quality, whether containing acid or alkali detergent, low temperature of washing water can be caused cleanness of glass, and bond strength accordingly
• Check direction of float glass surface, find out flat surface and tin surface of float glass, the bonding strength between flat glass surface and PVB film is stronger, however, contrary tin surface of float glass has stronger bonding with SGP film.
• Checking pressure and temperature are accurate or not in autoclave, lower temperature or short pressure time inside of autoclave, it will cause PVB interlayer fluidity get worse, can not bond together with glass tightly, check the pressure record of autoclave and regularly correct number of pressure meter.
• The glass or PVB interlayer film was contaminants will reduce adhesive strength of the laminated glass, in laminating room should be kept slightly positive pressure, clean, constant temperature and humidity, supplies and tools are managed. Before production should check again the PVB film size and color, make sure is correct because different PVB interlayer adhesion strength are also different.
• If production processes is fine, inspect condition and sampleof bonding strength test, check it is uniform, monitor negative temperature oven temperature is consistent with the requirements of -18 ℃, because test temperature influences on test results greatly.

Impact resistance

(1) Phenomenon: Impact resistance decline

(2) Reasons

• If bond strength was too high level between glass and PVB interlayer film, bond strength and impact resistance is inversely proportion
• The changes of PVB interlayer thickness, thinner part has low impact resistance, consider thinner PVB film were pulled or changed.
• The changes of PVB interlayer thickness, thicker part of glass has low impact resistance.
• Different PVB film lots cause different impact resistance of laminated glass.
• Changes of impact test condition, such as inaccurated test frame, temperature or procedures, sample size.

(3) Solutions

• The lower impact resistance of laminated glass is concerned with bonding strength. Lower moisture content of PVB interlayer film can increase bond strength, but will result in reduced impact resistance of the laminated glass, so have to control moisture within a range of standard.
• Measuring thickness of the laminated glass including PVB film Thickness and lite thickness, testing sample should be choosen as same as products which is producing.
• Check kinds of laminated glass, brand of PVB interlayer, Thickness and other specifications, model is correct, different kinds PVB film has different properties and applications, there are differences in impact resistance; so did glass. Measure PVB interlayer sample is same important as glass sample.
• Check condition and record in impact testing, such as temperature of sample, impact value would be significantly reduced at low or high temperatures environment ; observe test framework which condition will affect testing result, check framework edge whether be weared, cracks or wrong size of framework.

Boiling test

(1) Phenomenon: Boiling test fails

(2) Causes

• PVB interlayer moisture over limits.
• Moisture or air bubbles be existed in laminated glass
• Higher temperature during boiling test

(3) solutions

• Pay attention for moisture of PVB film, if moisture shows higher, it appears bubbles in boiling test.There are many possible reasons to cause higher moisture, such as PVB itself has higher moisture, PVB film in high humidity environment, storage time had exceed its life, appears packing leakage etc., as well as checking moisture measuring device whether is accurate, standard sampling moisture and so on. Then need to check the warehouse environment , laminating room, moisture measurement device and standard sampling.
• Due to air-out is not enough through in roll-in pressing, earlier sealing caused moisture and air left in laminated glass, need to adjust roll-in pressing parameters, such as temperature, pressure, moving speed etc., to get a good effects of air-out and sealing.
• Checking boiling test conditions and equipment to ensure that the test conditions at the required range of temperature.