Polyolefin substrates

This difference in reactivity between the different classes of amines explains the difference in the primer performance on polyolefin substrates with ethyl cyanoacrylate-based adhesives [37J. Since primary and secondary amines form low molecular weight species, a weak boundary layer would form first, instead of high molecular weight polymer. Also, the polymer, which does ultimately form, has a lower molecular weight, which would lower adhesives strength [8,9]. 

Radical induced grafting may be carried out in solution, in the melt phase,292 29 or as a solid state process.296 This section will focus on melt phase grafting to polyolefin substrates but many of the considerations are generic. The direct grafting of monomers onto polymers, in particular polyolefins, in the melt phase by reactive extrusion has been widely studied. Most recently, the subject has been reviewed by Moad1 9 and by Russell.292 More details on reactive extrusion as a technique can be found in volumes edited by Xanthos," A1 Malaika and Baker et a 21 7 The process most often involves combining a frcc-radical initiator (most commonly a peroxide) and a monomer or macromonomer with the polyolefin as they are conveyed through the extruder. Monomers commonly used in this context include MAII (Section 7.6.4.1), maleimidc derivatives and malcate esters (Section 7.6.4.2), (meth)acrylic acid and (meth)acrylate esters (Section 7.6.43), S, AMS and derivatives (Section 7.6.4.4), vinylsilancs (Section 7.6.4.5) and vinyl oxazolines (Section 7.6.4.6). 

With a history of more than 25 years, the free radical-induced grafting of MAH onto polyolefin substrates is one of the most studied polyolefin modification processes.29 "29, 302 The process has been carried out in the melt phase, in various forms of extruders and batch mixers, and there are numerous patents covering various aspects of the process. It has also been carried out successfully in solution and in the solid state. The materials have a range of applications including their use as precursors to graft copolymers, either directly, or during the preparation of blends.297... 

As with MAH, the extent of grafting varies dramatically vi ith the polyolefin substrate. Some differences have been attributed to variations in the type and amount of stabilizers present in the polyolefins substrate.326 In the case of isotactic PP, the maximum graft levels attained with 27 were found to correspond to only one unit of DEM per PP molecule 5 0 This would support a mechanism whereby grafts appear only at the chain ends. Higher graft levels were obtained with atactic PP. The higher reactivity of the atactic PP (and atactic sequences in... 

Stereoselectivity in the synthesis of trisubstituted olefins is necessary for the study of biosynthetic routes to polyisoprenoids, the nonenzymatic cyclization of polyolefinic substrates, and the study of insect hormones. 

Flexibilized epoxy adhesives have moderate strength on flame and corona treated polyolefin substrates. Elevated cure temperature results in better adhesion because of more efficient wetting of the substrate surface. Table 16.13 shows a starting formulation for an epoxy adhesive that develops high peel strength to many difficult-to-bond substrates such as polyethylene, thermoplastic rubber, and polyester film. 

TABLE 16.12 Tensile Shear Strength of Plasma Treated Polyolefin Substrates Bonded with Epoxy-Polyamide Adhesive69... 

It is apparent that of the compounds studied herein the hindered substituted bis- and tris-phosphites having dibenzofd,f][1,3,2] dioxaphosphepin rings, are the most effective compounds in the specific polyolefin substrates tested. Of particular interest in this regard is the triethanolamine tris-phosphite compound 8. 

Uses UV absorber for polyolefin substrates It. stabilizer for PVC, unsat. 

Lensorb C214 Lensorb C230 2,4,4 -Tribydroxybenzopbenone UV absorber, polyolefin substrates... 

Uses Light stabilizer for PVC, polyolefin substrates stabilizer for food-grade polymers Regulatory FDA 21CFR 178.2010 Trade Name Synonyms Tinuvin 622 [Ciba Spec. Chems./Plastic Addit. http //www.cibasc.com], Tinuvin 622LD [Ciba Spec. Chems./Plastic Addit. http //www. cibasc. com]... 

This study allowed the comparative evaluation of different polyolefin substrate in respect to their thermal oxidation. As it was expected, ultrahigh molecular weight polyethylene shows the most significant thermal resistance to oxidative degradation [04G2]. The order of increase in the delay of oxidation is ... 

Piernot, 0. Dewez, L. Detournay L. Wautier, H. Article comprising a polyolefin substrate and a coating layer covering at least part of... 

The development of SPM and particularly AFM has not been ignored by the adhesion world. The analysis of failure surfaces by AFM is still in its infancy but it is already clear that AFM may sometimes be more useful than SEM. Thus AFM has been used successfully in the analysis of the failure surfaces of adhesively bonded galvanized steel [149] and in the study of the adsorption of polymers on conducting polymer substrates [150,151]. Some of the author s unpublished studies have shown that the corona treatment of polyolefines gives rise to a characteristic morphology and that failure interfaces from peel joints of polyolefine substrates can yield more useful information from AFM than from SEM investigations [152]. 

Figure 4.5 Peel energies for etched polyolefin substrates bonded with a poly(acrylic acid) adhesive as a function of etch time in chromic acid solution [40].

Scratch/mar resistance Needed for polyolefin substrates Elimination is major research and development objective... 

Eversorb 73 is a benzotriazole type absorber. It offers superior light protection of polyolefin substrates against the deterioration of UV radiation. Eversorb 73 is also efficient for the light stabilization of polyvinyl chloride, unsaturated polyester, polyurethane, styrenic polymers, coatings and lacquers. 

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