Polyolefins surface

Mixtures of a titanium complex of saturated diols, such as TYZOR OGT, and a titanium acylate, such as bis- -butyl-bis-caproic acid titanate, do not have a yellowing or discoloring effect on white inks used to print polyolefin surfaces (506). The complexes formed by the reaction of one or two moles of diethyl citrate with TYZOR TPT have an insignificant color on their own and do not generate color with phenol-based antioxidants (507). The complexes formed by the addition of a mixture of mono- and dialkyl phosphate esters to TYZOR TBT are also low color-generating, adhesion-promoting additives for use in printing polyolefin films (508). 

Low surface energy substrates, such as polyethylene or polypropylene, are generally difficult to bond with adhesives. However, cyanoacrylate-based adhesives can be effectively utilized to bond polyolefins with the use of the proper primer/activa-tor on the surface. Primer materials include tertiary aliphatic and aromatic amines, trialkyl ammonium carboxylate salts, tetraalkyl ammonium salts, phosphines, and organometallic compounds, which are initiators for alkyl cyanoacrylate polymerization [33-36]. The primer is applied as a dilute solution to the polyolefin surface, solvent is allowed to evaporate, and the specimens are assembled with a small amount of the adhesive. With the use of primers, adhesive strength can be so strong that substrate failure occurs during the course of the shear tests, as shown in Fig. 11. 

The mechanism by which the primers are thought to work is relatively straightforward. The primer first diffuses into the polyolefin surface, and subsequently becomes entangled in the polyolefin. The primer molecule can then act as an anchor in the substrate surface for the adhesive polymer, which forms after the primer initiates polymerization of the alkyl cyanoacrylate monomer [37]. 

Photografting of Acrylic Monomers onto Polyolefin Surfaces... 

Adhesive Performance of Surface-Activated Polyolefin Surfaces with Respect to Reinforcement Resins... 

A typical oxyfluorination treatment that is sufficient to activate polyolefin surfaces with respect to polyester adhesion includes the following ... 

In a similar attempt, Vernekar et al. [134] carried out photochemical bromination of polyolefin surfaces. It was observed that the gas phase photochemical bromination occurred with high degree of regioselectivity. The bromination of LDPE surface yielded four different species (a) secondary Br, (b) allyl Br, (c) vinyl Br and (d) dibromide, in varying proportions depending upon the underlying mechanism. However, the formation of allyl Br moieties was predominant. The proposed mechanism of photochemical bromination is presented in Scheme 10. 

The main purpose of this chapter is to describe methods of modifying polyolefin surfaces in such a way as to render them printable, and also to describe the tests that are available for determining the effects of treatment and... 

There are many different methods for modifying polymer surfaces to improve their adhesion and wetting properties. They include chemical etching and oxidation, ion bombardment, plasma treatments, flame treatment, mechanical abrasion and corona-discharge treatments (1.2). Especially flame and corona treatments are widely used for the modification of polyolefin surfaces to enhance, for instance, their printabilify. Despite the widespread use of such processes in industry, the understanding of the fundamental processes which occur at the polymer surface is very limited. This is undoubtedly due to the shallow depth to which the polymer is modified, typically 5 nm or less. 

A surface analysis technique that has the potential to detect structural chemical changes in polymer surfaces, including low-molecular weight material formation, is static SIMS. Its capabilities for characterizing polymers by virtue of their fingerprint spectrum nave been amply demonstrated in recent years (5 6). The technique is more surface sensitive than XPS and can detect structural differences, even in hydrocarbons (7). It is, therefore, highly complementary to XPS. Nevertheless, only very few applications to the study of modified polymer surfaces have been published. Among these are reports on SIMS analysis of flame-treated polypropylene and plasma-fluorinated polyolefin surfaces (8 9). 

Polyethylene and Polypropylene Acceptable bonds have been obtained between treated polyolefin surfaces with polar adhesives, such as epoxies, or solvent cements containing synthetic rubber or phenolic resin. The solvent adhesives are applied to both surfaces and the solvents allowed to evaporate before the parts are joined. Recommended epoxies are the anhydride-cured and amine-cured types. Also suitable is a two-component, polyamide-modified epoxy compound. Other adhesives that provide adequate bond strength to treated polyolefins include styrene-unsatmated polyester and solvent-type nitrile-phenolic (15). 

Fig. 4.8 (a) Histograms of pull-off force values obtained with an unmodified Si3N4 tip on untreated and oxyfluorinated iPP films in ethanol. The total surface free energy y of the polymer film is shown, (b) Mean values of pull-off force measured with COOH-terminated tips on modified polyolefin surfaces (iPP, isotactic polypropylene LDPE, low-density polyethylene) in ethanol (top) and with OH-terminated tips on oxyfluorinated iPP in water (pH 3.8, bottom) as a function of cos 0 (contact angle measured with water). (Reprinted in part/adapted with permission from [26, 27]. Copyright 1998, 2000, American Chemical Society.)... 

The used flame treaters for treatment of polyolefin surfaces in packaging applications depend on whether the sample to be treated has a three- or two-dimensional geometry. Three prime components can be recognized in both cases. The three-dimensional treatment plant is typically consisted of following parts (Fig. 8.7a). A conveyor belt is used for a continually treatment of material, such as polyolefin objects mounted on special heat resistant holders. A cleaning equipment, such as brush-like system or a compressed air stream, commonly placed a few centimeters in front of the burners allows removing of all small particles, such... 

This low-pressure process is the only known way for the introduction of monosort functional groups onto polyolefin surfaces and was observed 20 years ago... 

P. Blais, D.J. Carlsson, G.W. CsuUog, D.M. Wiles, Chromic acid etching of polyolefin surfaces and adhesive bonding. J. Colloid Interface Sci. 47, 36-649 (1974)... 

L.G. Beholz, C.L. Aronson, A. Zand, Adhesion modification of polyolefin surfaces with sodium h)qK)chlorite in acidic media. Polymer 46, 4604-4613 (2005)... 

R.L. Ayres, D.L. Shofner, Preparing polyolefin surfaces fm inks and adhesives. SPE J. 28,... 

J. Friedrich, S. Wettmarshausen, M. Hennecke, Halofoim plasma modification of polyolefin surfaces. Surf. Coat Technol. 203, 3647-3655 (2009)... 

Uses Antistat for polyolefins surface coating for EPS fabric softener coemulsifier... 

On the other hand, treatment of these surfaces first with ethyl chloroformate followed by pentadecylfluorooctylamine produced a hydrophobic fluorinated surface. Modifying a pristine polyolefin surface allows for further processing of the polymer, an increase in the appHcation range, and impact of the material in the market. 

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