Windshield bonding

Structural glazing Surface preparations Teak decks Test of a bead Thickness of the joint Transport equipment Uneven stress distribution UV radiation Waterswelling sealants Wettability Windshield bonding Woehler diagram. 

In 1964, another key development started when the US automotive industry had to fulfill safety standards which required the retention of the windshield in a crash and thus, to ensure that the occupants remained inside the car (FMVSS 212). The windshield bonding technology involved has been called direct glazing ever since. At that time, direct glazing was achieved by the use of a material which... 

Robots are used to dispense adhesives and sealants throughout the automotive industry today. Automation requirements will be examined for windshield bonding to the vehicle, door manufacturing, passenger compartment interior seam sealing, and the application of sealants during the buildup of the vehicle body. These account for the vast majority of robotic sealant and adhesive dispensing applications in the automotive industry. 

Windshield Bonding and Body Shop Robotic Sealing... 

Figures 13 and 14 depict possible robot system configurations for windshield bonding and body shop sealing. All of the applications mentioned have similar considerations for evaluation of robotic applications. The common considerations for robotizing these and other adhesive and sealant applications include required bead profile (round, flat, or triangular) instantaneous flow or delivery rate robot speed, accuracy and repeatability and workspace of the robot.

Windshield bonding often requires the dispensing of a triangular bead at 10-18 in./sec. 

The material traditionally used in windshield bonding has been a single-component moisture-cure urethane. These urethanes are often high in viscosity resulting in high application pressures to meet the robotic dispense rate. 

When windshield adhesives are directly exposed to sunlight the thin adhesion layer directly on the glass will be destroyed by UV-radiation. Therefore, a UV protection is a must. In the beginning of windshield bonding, this was achieved by a black primer, but under severe UV-radiation, even this rather stable UV-blocking primer was destroyed over time. With the... 

The use of a primer to prepare the paint surface for the windshield bonding. This is a commonly used process. It is mostly a manual operation with the risk of contamination... 

For windshield bonding an additional durability issue is the resistance to UV-radiation. The directly exposed bonding zone of the adhesive is destroyed by UV-radiation if not protected by a screen print on the glass with sufficient UV absorption or with other methods of masking. 

Subsequent to processing, an inspection is made for incomplete bonding, inside dirt, and glass quaUty. In the case of windshields, rigid optical standards must be met, and these must be evaluated for the completed windshield. Extensive test requirements are described in the appropriate codes (11,12,15,18—24), and they include light stabiUty, resistance to optical distortion, humidity, boil test, abrasion resistance, and assorted impact tests. 

Many grades of interlayer are produced to meet specific length, width, adhesion, stiffness, surface roughness, color (93,94), and other requirements of the laminator and end use. Sheet can be suppHed with vinyl alcohol content from 15 to about 23 wt %, depending on the suppHer and appHcation. A common interlayer thickness for automobile windshields is 0.76 mm, but interlayer used for architectural or aircraft glaring appHcations, for example, may be much thinner or thicker. There are also special grades to bond rear-view mirrors to windshields (95,96) and to adhere the components of solar cells (97,98). Multilayer coextmded sheet, each component of which provides a separate property not possible in monolithic sheet, can also be made (99—101). 

Laminates. Two or more layers of material bonded together form a laminated composite. Common examples of laminates are in automobile windshields (laminated glass) and bimetal thermostats (9). In both cases homogeneous, isotropic layers of materials are bonded together to form nonhomogeneous composite laminates (see Laminates). 

Several large applications for one-component moisture-cure urethane adhesives are available. Polymeric MDI is an exceptional binder for wood products, such as oriented strand board and particleboard. One-component urethane windshield adhesives are used almost exclusively in both the OEM and automotive aftermarket. One-part urethane adhesives are used to assemble the sidewalls for recreational vehicles (RV s), manufactured housing, and mobile homes. In construction applications, one-part urethanes are used to bond metal doors, hardwood flooring, panels, and partitions. 

A variety of applications exist for liquid, 100% solid adhesives, (An adhesive is considered 100% solid if there is no solvent in the adhesive.) Some of the largest uses include structural wood adhesives and adhesives used for the transportation industry, such as windshield adhesives and those used for bonding composite sidewalls of a recreational vehicle (RV). Structural wood adhesives are often made of a polymeric MDI with functionality of approximately 2.7 or higher. Rigid assemblies often utilize polymeric MDI, whereas flexible adhesive assemblies will more often utilize pure MDI, a solid waxy material that melts at around 37°C, or a modified MDI , i.e., MDI that has been modified to make it a liquid at room temperature. Prepolymers are made with ratios of anywhere from NCO/OH = 1.6 to 3.0 or higher. 

A recent reference [1] lists twenty suppliers of structural acrylic adhesives. Many other companies have been involved in this area, and it is often felt that acrylic adhesives have unrealized technical potential [2]. Acrylic adhesives are not commonly found in the consumer market, but fill an important niche there in the bonding of rear view mirrors to windshields in automobiles. 

The manufacturers of windshield coatings take advantage of the fact that the hydrophilic substances possess chemical structures that permit favorable intermolecular interactions with water. Chemical species capable of exhibiting hydrogen bonding, dipole-dipole interactions, or ion-dipole interactions with water are typically hydrophilic substances. Alternatively, hydrophobic substances typically are nonpolar molecules that exhibit only weak van der Waals interactions with water. 

Another well-established use of UV/visible lighf curing adhesives is glass, a plastics bonding in the automotive industry. Typical applications are lamination of safety glass, fastening of rear-view mirrors to windshields, and assembly of headlights. ... 

The complexes of type 153 show temperature-dependent carbonyl signals in their 13C-NMR spectra due to hindered movements of the /i-f/2 1-dienyl ligands. This movement can be described as a windshield wiper type oscillation, by which the a and n bonds are interchanged between the two rhenium atoms. For octacarbonyl-fi-ri2 1 -1,3,5-cycloheptatrien-2-yl-/i-hydridodirhe-nium (162) and for octacarbonyl-/ - /2 1 -1,3,5-cycloheptatrien-1 -yl- -hydri-dodirhenium (162 ) activation barriers of AG255 = 48.0 2 kJ/mol and AG207 = 39.9 2 kJ/mol (218) have been determined. 

Many covalent compounds do not have negative and positive charges to attract water molecules. Thus they are not soluble in water. There are some exceptions, however. Methanol (a component of windshield washer fluid), ethanol (the alcohol in alcoholic beverages), and sugars (such as sucrose) are examples of covalent compounds that are extremely soluble in water. These compounds dissolve because their molecules contain polar bonds, which are able to form hydrogen bonds with water. 

Cyanoacrylates are not appropriate for the bonding of the steel parts of an automobile, because of the environments that the car will be exposed to. Those environments include such things as rain, variations in temperatnre, exposure to solvents (such as gasoline, oil, and windshield washer solntion), ozone, acid rain, salt spray, and ultraviolet light from the Sun. (A more appropriate adhesive for car parts would be an epoxy-based adhesive.) Another example of a special adhesive would be the one used to attach a new rearview mirror in an antomobile. Because the cured adhesive in this case will be exposed to wide variations in temperature and to an extremely large amonnt of nltraviolet fight from the Snn for prolonged periods of time, an adhesive formnlated specifically for these conditions should be used. 

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