Adhesives for casing

One may also be able to determine the work of adhesion for cases in which the contact angle is zero by using probe liquids, as described later in this chapter. There are also other ways of determining the work of adhesion, such as inverse gas chromatography, which do not depend solely on capillary measurements (surface tension and contact angle). This too will be discussed later. 

Figure I. Inert diluent process flow diagram Adhesives for Case Bonding...

Adhesives for Case and Carton Sealing. Once the corrugated board or the solid fiberboard boxes are constructed, they must be glued, filled with product, and the top flaps folded down and glued closed before shipment. The adhesive... 

Dextrins have many applications, with adhesives being their primary market (11,96). Dextrins are used as adhesives for case and carton sealing. For this application, borax is often added to the dextrin to add stability and increase viscosity. Dextrins are added to adhesives used in the laminating of products such as paperboard and shipping containers. The paper industry adds dextrins in adhesives for tube winding and bag adhesives. Library pastes, bottle label adhesives, envelop adhesives, gummed tape, and wall covering adhesives all benefit fiom dextrin addition. 

A representative hot melt adhesive formulation based on a low molecular weight polyethylene resin would be composed of the materials shown in Table 8. A low density polyethylene based hot melt adhesive for case sealing might contain the formulation shown in Table 9. 

As of this time, no one has solved the problem of the effect of asperities on a curved surface nor has anyone addressed the issue of crystalline facets. Needless to say, the problem of asperities on an irregular surface has not been addressed. However, Fuller and Tabor [118] have proposed a model that addresses the effects of variations of asperity size on adhesion for the case of planar surfaces. Assuming elastic response to the adhesion-induced stresses, they treated surface roughness as a random series of asperities having a Gaussian height distribution (f> z) and standard deviation o. Accordingly,... 

Another factor that can contribute to the low release force provided by a release material is the presence of a mechanically weak boundary layer at the surface of the release coating [40,41]. Upon peeling the PSA from the release coating, the locus of failure is within this mechanically weak layer, resulting in transfer of material to the adhesive and a subsequent loss in adhesion of the PSA. Although the use of a weak boundary layer may not be the preferred method of achieving low adhesion for PSA release coatings, it can be useful if the amount of transfer is consistent and kept to a minimum [42]. However, in many cases the unintentional or uncontrolled transfer of a weak boundary layer to a PSA results in an undesirable loss in readhesion. 

S.2.2.2. Composite adherends. Composite adherends are bonded in both the cured and uncured states. Wherever possible the adhesive and all adherends are cured simultaneously to avoid the added cost of additional autoclave cure cycles. In many cases this is not practical due to part size and complexity. Cured parts can be bonded to uncured parts, which is known as cobonding, and fully cured parts can be bonded together, which is known as secondary bonding. Adhesives for composites are formulated to be compatible with matrix resins in either cured or uncured states. 

S. Fan, S. Yuan, and Y. Ye. A laboratory study of adhesion agent of er type for casing cementing. J Jianghan Petrol Inst, 18(2) 77-80, June 1996. 

Approximately one million metric tons of urea-formaldehyde resin are produced annually all over the world. More than 70% of this urea-formaldehyde resin is consumed by the forest products industry. The resin is used in the production of an adhesive for bonding particleboard (61% of the urea-formaldehyde used in the industry), medium-density fiberboard (27%), hardwood plywood (5%), and as a laminating adhesive (7%) for bonding furniture case goods, overlays to panels, and interior flush doors, for example. 

FTIR has shown the close similarity of most resins based on Bis-Phenol A and has helped narrow the focus of development on the curative as the principal contributor to successful formulation. For present applications oligomeric polyamide amines appear successful in meeting present criteria. However, the only objective analysis of cured resin to date exhibiting a correlation of measured value with success in creep resistance as well as adhesion is heat distortion temperature. The following presents a correlation of heat distortion temperatures and adhesion for several formulations tested. In most cases, pass/fail criteria was based on the majority of six samples tested. 

If the rate of deposition decreases with time, it means that Pt < 1, i.e. high rate of sedimentation compared with the rate of adhesion. For this case (9) is adequately described by ... 

Bond line temperatures are best measured by thermocouples placed very close to the adhesive. In some cases it may be desirable to place the thermocouple directly in the adhesive for the first few assemblies being cured. 

Ion beams are often utilized to prepare clean surfaces for PES studies or for depth profiling through a sample. This causes problems in polymer studies as the surface can be chemically degraded as has been demonstrated in the case of polyimide (19,20). This effect, however, has been used to increase metal/polymer adhesion, while the exact mechanism (chemical, mechanical) for the improved adhesion for the metals to polyimide is not yet completely understood (21,22). 

Ae/untreated PE. Based on the C Is level and valence level spectra, no evidence of Ag interaction with untreated PE was found. Several depositions were done, and in all cases no changes in the shape or peak positions were found. This is consistent with the poor adhesion for Ag on untreated PE. The results for Ag depositions on argon-plasma-treated PE were similar, except for slight changes in the valence level spectra which will be discussed below. 

The amino-resins are also suited for use on wood-composite products. In some cases the fire retardant can act as the binder for particle board (99, 100), the adhesive for plywood (99, 100), or a... 

Thermosetting Foam Substrates Most thermosetting plastics are not particularly difficult to bond. Obviously, solvent cementing is not suitable for bonding thermosets to themselves, since they are not soluble. In some cases solvent solutions can be used to join thermoplastics to thermosets. In general, adhesive bonding is the only practical method of joining a thermoset to itself or to a non-plastic material. Epoxies or modified epoxies are the most widely used adhesives for thermosets (1). 

---