Interlayers

Resins formed from the reaction of poly(vinyl alcohol) with aldehydes. The formal derivative (from methanal) is used in wire coatings and adhesives and the bulyral (from butanal) is used in metal paints, wood-sealers, adhesives and in safety glass interlayers. 

In the context of the structural perturbations at fluid-solid interfaces, it is interesting to investigate the viscosity of thin liquid films. Eaily work on thin-film viscosity by Deijaguin and co-workers used a blow off technique to cause a liquid film to thin. This work showed elevated viscosities for some materials [98] and thin film viscosities lower than the bulk for others [99, 100]. Some controversial issues were raised particularly regarding surface roughness and contact angles in the experiments [101-103]. Entirely different types of data on clays caused Low [104] to conclude that the viscosity of interlayer water in clays is greater than that of bulk water. 

The structurally similar molybdenum disulfide also has a low coefficient of friction, but now not increased in vacuum [2,30]. The interlayer forces are, however, much weaker than for graphite, and the mechanism of friction may be different. With molecularly smooth mica surfaces, the coefficient of friction is very dependent on load and may rise to extremely high values at small loads [4] at normal loads and in the presence of air, n drops to a near normal level. 

Most metal surfaces have the same atomic structure as in the bulk, except that the interlayer spaciugs of the outenuost few atomic layers differ from the bulk values. In other words, entire atomic layers are shifted as a whole in a direction perpendicular to the surface. This is called relaxation, and it can be either inward or outward. Relaxation is usually reported as a percentage of the value of the bulk interlayer spacing. Relaxation does not affect the two-dimensional surface unit cell synuuetry, so surfaces that are purely relaxed have (1 x 1) synuuetry. 

Figure Bl.23.16. Plots of the two-dimensional fJ-faetors as a fiinotion of the deviation d) of the first-seeond interlayer spaeing from the bulk value. The experimental and simulated images along the (ill) and (I I2) azimuths of figure Bl.23,15 were used in the eomparison.

Leadbetter A J, Frost J C and Mazid M A 1979 Interlayer oorrelations in smeotio B phases J. Physique Lett 40 325-9... 

Nassehi, V., Dhillon,. 1. and Mascia, L., 1993a. Finite element simulation of the micro-mechanics of interlayered polymer/fibre conrposites a study of the interactions between the reinforcing phases. Compos. Sci. Tech. 47, 349-358. 

Nassehi, V., Kinsella, M. and Mascia, 1.., 1993b. Finite element modelling of the stress distribution in polymer composites with coated fibre interlayers. J. Compos. Mater. 27, 195-214. 

Its key characteristics are its excellent optical and adhesive properties. It is used as the interlayer film for safety glass. 

PVB interlayer piNYL POLYTffiRS - VINYL ACETAL POLYTffiRS] pol 24)... 

Vinylidene polymers Vinylidine chloride Vinyl interlayer Vinylite flooring Vinyl ketal polymers Vinyllithium [917-57-7]... 

Solid-State Welding. Sohd-state welding comprises a group of welding processes wherein a bond is made between two base materials upon the apphcation of pressure at a temperature below the soHdus of the base materials (Table 1). Interlayers are sometimes used. By joining materials in the sohd state, many of the difficulties of the fusion processes are avoided. 

New Adsorbent Materials. SihcaUte and other hydrophobic molecular sieves, the new family of AlPO molecular sieves, and steadily increasing families of other new molecular sieves (including stmctures with much larger pores than those now commercially available), as well as new carbon molecular sieves and pillared interlayer clays (PILCS), will become more available for commercial appHcations, including adsorption. Adsorbents with enhanced performance, both highly selective physical adsorbents and easily regenerated, weak chemisorbents will be developed, as will new rate-selective adsorbents. 

Transparent ionomer coatings are appHed to glass surfaces to improve safety characteristics (39). Special types of ionomers are used as interlayers between glass sheets for appHcations requiring penetration resistance (40). 

The above-mentioned codes contain requirements for accelerated durabiUty tests. In addition, interlayer manufacturers and laminators expose test samples for several years under extreme weather conditions, eg, the Florida coast and Arizona desert. The laminated products weather extremely well, with no change in the plastic interlayer. Occasionally, clouding is noted around the edges when exposed to high humidity for long periods, but this is reversible. Colored areas of PVB laminates may fade while subjected to extensive uv/solar irradiation, which could cause an appearance issue. This has not, however, been shown to alter the laminate s other performance properties. 

Interlayer moisture is one of the important controls for PVB-to-glass adhesion of current formulations (although moisture-insensitive formulations are being developed). The moisture content equiUbrates with the relative humidity to which the interlayer is exposed and thus is variable. Prior to lamination, interlayer moisture content is measured by one of three methods. The most rapid is by air absorption using a spectrophotometric technique to determine a... 

The ASA (now ANSI) performance code for Safety Glazing Materials was revised in 1966 to incorporate these improvements in windshield constmction. The addition of test no. 26 requiring support of a 2.3-kg ball dropped from 3.7 m defined this level of improvement. It was based on a correlation estabUshed between 10-kg, instmmented, head-form impacts on windshields, on 0.6 x 0.9-m flat laminates, and the standard 0.3 x 0.3-m laminate with the 2.3-kg ball (28). Crash cases involving the two windshield interlayer types were matched for car impact speeds and were compared (29). The improved design produced fewer, less extensive, and less severe facial lacerations than those produced in the pre-1966 models. 

Additional improvements have been incorporated since 1966 with the availabihty of thinner float glass. Glass thickness and interlayer thickness have been studied to optimize the product for occupant retention, occupant injury, and damage to the windshield from external sources (30,31). The thinner float glass windshields are more resistant to stone impacts than the early plate glass windshields. The majority of laminated windshields are made of two pieces of 2—2.5 mm aimealed glass and 0.76 mm of controlled adhesion interlayer. 

Fig. 8. Sierracin lightweight, birdproof F-111 windshield cross section (43). A, 3.0-mm as-cast acryflc face ply B, S-100 silicone interlayer C, fiberglass retainer D, 6.4-mm polycarbonate stmctural ply E, S-120 polyurethane interlayer E, stainless steel bearing strip and G, stainless steel bushing.

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