Adhesion of polyethylene

Papirer et al. used ATR, XPS, and SIMS to determine the effect of flame treatment on adhesion of polyethylene and polypropylene to styrene/butadiene (SBR) rubber [8]. Each flame treatment consisted of a 75-ms pass over a circular burner. The distance between the upper flame front and the polymer was kept fixed al 8 mm. A band was observed near 1720 cm" in the ATR spectra and assigned to carbonyl groups this band increased in intensity as the number of flame... 

Butyl latex can be used in packaging and as a tackifying and flexibilizing additive in higher strength adhesives for adhesion of polyethylene and polypropylene. 

Specialty waxes include polar waxes for more polar adhesive systems. Examples would be castor wax (triglyceride of 12-hydroxy stearic acid) or Paracin wax N- 2 hydroxy ethyl)-12-hydroxy stearamide) which are used in polyester, polyamide, or with high VA EVA copolymer-based systems. Other common polar waxes are maleated polyethylenes, which are used to improve the specific adhesion of polyethylene-based adhesives, and low molecular weight ethylene copolymers with vinyl acetate or acrylic acid, which are used to improve low temperature adhesion. High melting point isotactic polypropylene wax (7 155°C) and highly refined paraffin wax (7,n 83°C) are used where maximum heat resistance is critical. Needless to say, these specialty waxes also command a premium price, ranging from 2 to 5 times that of conventional paraffin wax. 

Many types of chemical treatment are used in industry. Chromic, permanganic, sulphuric, and chlorosul-phonic acids are often used as the oxidants. It has been shown that the adhesion of polyethylene to substrates, such as cellophane, steel, aluminium, and epoxy adhesives, improves upon pretreatment with any of the etchants mentioned previously. 

Nardin M. and Ward, I.M. (1987). Influence of surface treatment on adhesion of polyethylene fibers. Mater. Sci. Technol. 3, 814-826. 

Surface oxidation reactions have been carried out on a number of polymers, particularly polyethylene. Surface oxidation techniques include the use of corona discharge, ozone, hydrogen peroxide, nitrous acid, alkaline hypochloride, UV irradiation, oxidizing flame, and chromic acid The reactions lead initially to the formation of hydroperoxides, which catalyze the formation of aldehydes and ketones and finally, acids and esters. Surface oxidation treatment has been used to increase the printabdity of polyethylene and poly(ethylene terephthalate) and to improve the adhesion of polyethylene and polypropylene to polar polymers and that of polytetrafluoroethylene to pressure-sensitive tapes. Surface-oxidized polyethylene, when coated with a thin film of vinylidene chloride, acrylonitrile, and acryhc acid terpolymers becomes impermeable to oxygen and more resistant to grease, oil, abrasion, and high temperatures. The greasy feel of polyethylene has also been removed by surface oxidation. 

Table 1. Effect of antioxidant concentration on the adhesion of polyethylene to flat and...

In particular, graphite is introduced in order to increase the adhesion of polyethylene powders to the surface under treatment, while, in order to reduce the adhesion of dust and fluff to the coating, compounds of the... 

B. W. Malpass, D. E. Packham and K. Bright, A Study of the Adhesion of Polyethylene to Porous Aluminum Films Using the Scanning Electron Microscope", J. Appl. Poly. Sci., 1, 3249 (1974). 

A well knoiw method, grafting, has been used to improve adhesion of polypropylene, and polyethylene to metals. Schultz et al. show that the addition of acrylic acid can enhance the adhesion of polyethylene to aluminum. 

A series of papers by Packham and co-workers [20-26] also emphasizes the improvements in joint strength that may be observed when a microfibrous surface topography is created. In their studies on the adhesion of polyethylene (used as a hot-melt adhesive) to metallic substrates they found that high peel strengths were obtained when a very rough, microfibrous, oxide surface was produced on the substrate. Fig. 3.3a is a scanning electronic micrograph of the... 

Adhesion of polyethylene to copper. Substrate surface after peeling from (a) polished copper and (b) copper with a microfibrous oxide surface... 

Effect of corona treatment on adhesion of polyethylene to itself (autohesion) has been studied as a function of lamination temperature and density, as shown in Figs 5.6 and 5.7. Corona treatment has a dramatic effect on the increase of adhesion bond strength over that achieved with untreated polyethylene. Increase in lamination temperature enhances the bond strength of treated film. 

Ozonation can be used to improve the adhesion of polyethylene to aluminum foil during extrusion coating [66]. As the molten polymer leaves the extrusion die it is subjected to a continuous stream of ozone immediately prior to making contact with the aluminum foil. The adhesive strength of the polymer to the metal increases as the level of oxygen incorporated into its surface increased. 

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