Particulate structural adhesive

PARTICULATE STRUCTURAL ADHESIVES USING CARBOXYLATED RUBBERS... 

Particulate structural adhesives have also been prepared by the combination of epoxy resins and elastomeric carboxylated rubber, Hycar 1072. The epoxy resins are milled into the rubber and then the curatives are added. The stock is sheeted from the mill and ground into a powder. The adhesives can be applied by electrostatic spraying, fluidized bed, or powder bed."" "... 

Table 4. Typical Formulation for Particulate Structural Adhesive. ...

In rotational molding, two bulk movements dominate the melt deposition and densification 1) the adhesion of particles on the mold surface and 2) the melting and collapse of the particulate structure. The latter... 

Young RJ (1986) Rigid-particulate reinforced thermosetting polymers in Structural Adhesives - Developments in Resins and Primers. Kinloch AJ (ed) Elsevier Applied Science Publishers London... 

Sticky tapes and labels are obvious uses of adhesives that cover a wide range of everyday applications. A relatively new type of adhesive has apparently been used in the manufacture of Post-it (trademark, 3M) products, small slips of paper with a reusable adhesive strip at one edge. SEM images show the adhesive partly coating the paper fibers (Fig. 5.83) [396]. Rounded domains of about 5-50 /xm form a contact on the applied surface (Fig. 5.83A). Regions between these rounded domains have a fine particulate structure which does not adhere, permitting the label to be removed easily. In order to image the adhesive nature of these materials, two adhesive strips were attached and then peeled back and exanuned in the SEM. (The adhesive strip and a piece of paper peel away from each other too... 

The macroscopic composites are those in which one or both phases tend to have structures large enough to be easily seen with the naked eye. These include paint hlms (paint itself is usually a particulate composite), adhesive joints, and foams (e.g., the familiar polystyrene foams used for coffee cups because of their low heat transfer coefficient). The fabric laminates alternate layers of inorganic cloth and plastic. An important subclass usually has multiple layers of glass cloth or chopped fiber interspersed with layers of unsaturated polyester-styrene AB-cross-linked materials see Section 2.7.3. These sheet molding compounds are widely used for the hulls of pleasure boats, because they are light weight and very puncture resistant, as well as for automotive bodies see Section 13.9.1. 

It is well estabhshed that microparticles can increase the fracture toughness of thermoset polymers in mode I loading (e.g., Moloney et al. 1983 Kinloch and Taylor 2002). Indeed, this is the basis of most structural adhesives, which have a rubber or thermoplastic particulate... 

The characteristics of particulate filled polymers are determined by the properties of their components, composition, structure and interactions [2]. These four factors are equally important and their effects are interconnected. The specific surface area of the filler, for example, determines the size of the contact surface between the filler and the polymer, thus the amount of the interphase formed. Surface energetics influence structure, and also the effect of composition on properties, as well as the mode of deformation. A relevant discussion of adhesion and interaction in particulate filled polymers cannot be carried out without defining the role of all factors which influence the properties of the composite and the interrelation among them. 

Over the last decade advances have occurred very rapidly in the area identified as composite materials. In general, a composite material is the combination of any two or more materials, one of which has superior mechanical properties but is in a difficult to use form (e.g. fiber, powder, etc.). The superior component is usually the reinforcement while the other component serves as the matrix in which the reinforcement is dispersed. The resultant composite is a material whose properties are near those of the reinforcement element but in a form which can be easily handled and can easily function as a structural element. Included in this definition are all of the reinforced materials including particulate, fiber, flake and sheet reinforcements. Adhesive joints for, example, would be a planar or two dimensional composite 1). 

The catalyzed washcoat possesses internal structure similar to those of catalyzed powders and particulates, and hence the properties applicable to them are also important to the washcoat. In addition, washcoat adhesion plays a critical role since gas throughputs are extremely high and exfoliation can be a common problem. 

At the domain level, controlled heterogeneity on the micrometer scale is, in fact, responsible for the unique properties of many, if not most, of our advanced structural materials. Fiber reinforcement, rubber toughening, crystallite reinforcement, and particulate reinforcement are familiar techniques. In each case, with proper adhesion at the interface, the resulting material provides the combination of strength, modulus, and toughness for the intended application. 

Structural Aspects of Adhesion in Particulate-Filled Polymer Composites... 

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