Electroplating on crystalline polypropylene. I. Compression molding and adhesion

Abstract

synopsisA direct relationship between polymer processing and metal adhesion is evident from studies of compression-molded isotactic polypropylene (PP). Cooling rate, nature of the mold surface, and after-plated annealing are shown to affect the peel adhesion of the plated components. This report described (1) the relation of compression molding variables to polymer surface morphology, (2) the oxidative cracking behavior of the surface due to pretreatment with chromic-sulfuric acid in terms of crystallite orientation and crystallinity, and (3) the effect of surface crack patterns on adhesion.The nature of the mold surface is the single most important variable for controlling the surface morphology of PP. Compression molding PP against oxidized aluminum or copper produces a spherulitic surface, whereas molding the polymer against Mylar or Teflon produces a transcrystalline surface. Surface etching of PP homopolymer produces sponge-like crack patterns characteristic of the morphology. Radial patterns are observed on spherulitic surfaces and random patterns, on transcrystalline ones. The various surface patterns are developed in the oxidative process by swelling of amorphous material followed by oxidative stress cracking and dissolution. Metal-to-polymer adhesion, as measured by the peel test, may involve failure a t the interface or within the polymer.(a) the geometry of the interface, (b) the diminished strength of the polymer surface arising from attack by the oxidizing acid, and (c) the crystallinity of the fissured polymer surface. The highest peel values are associated with conditions that lead to deep and frequent fissuring of the polymer surface and minimum oxidative damage.

Effect of Chain Extender on Phase Mixing and Coating Properties of Polyurethane Ureas

“…Since the substrate-induced crystallites constitute the interfacial area between the two materials, their characteristics affect the adhesion of the coating to the substrate. [10][11][12][13][14][15] Of equal importance is the preparation of surfaces and its nature, the coating application process, and, very often, the environmental conditions during application and drying of the coating. 16,17 Chatterjee et al 18 suggested that a substrate may have active sites such as cracks or fissures that increase the bonding of the polymer to the substrate at these sites.…”

“…When such material cures on a solid surface, heterogeneous nucleation at a plethora of nucleation sites, such as defects, craters, fewer, crevice, hills, and contaminants on the substrate surface, may take place. Since the substrate-induced crystallites constitute the interfacial area between the two materials, their characteristics affect the adhesion of the coating to the substrate. − Of equal importance is the preparation of surfaces and its nature, the coating application process, and, very often, the environmental conditions during application and drying of the coating. , Chatterjee et al suggested that a substrate may have active sites such as cracks or fissures that increase the bonding of the polymer to the substrate at these sites. Cui et al reported that the difference in adhesion development and moisture diffusion rate in isocyanate reactive hot melt adhesives is owed to a difference in crystalline structure.…”

Durability and structure of electroplated plastics

“…In some cases, the etch may cause solvent cracking. 69 Because the crystallinity of polypropylene is strongly affected by the moulding process, the porosity developed during etching can be strongly influenced by the moulding conditions. 21 For example, the etch on polypropylene plaques has been shown to decrease at low mould temperatures as the amount of atactic material decreases in the surface layer.…”

Improved adhesion of silicone rubber to polyurethane by induced surface reconstruction

“…18 The polymeric surface can form ordered, oriented layers at the surface during subsequent curing. 19 The part of such copolymers with a low critical surface tension is readily miscible with the silicone base matrix, whereas the other part interacts favorably with the more polar matrix. Both blocks can anchor the copolymer into the respective substrate, which ensures permanency of the surface modification and increases adhesion between two immiscible polymers.…”