P. Lutgen

Ageing and degradation of poly(ethylene terephthalate) in an oxygen plasma

Abstract The ageing of thin PET films in an oxygen plasma was investigated. After several hours exposure a large decrease in mechanical strength was observed. Plasma particle bombardment, chemical reactions and the plasma vacuum UV radiation cause extensive chemical and structural changes. The chemical reactions leading to the ageing process were identified.

Modification of polymer (PET) surface reactivity by low energy ion bombardment

The surface of polyethylene terephthalate (PET) was studied by low energy He/sup +/ ion scattering (ISS). Modifications of the surface composition induced by the He/sup +/ and Ar/sup +/ bombardments are observed. The ion bombardment causes surface damages with bond breaking and it results a highly activated surface for the chemisorption of nitrogen from the residual gas phase. Similar effects were observed on highly oriented pyrolytic graphite when analyzed in the same beam conditions.

HREELS analysis of the interface formation between vacuum evaporated aluminium and three polymer substrates poly(vinyl alcohol), poly(acrylic acid) and poly(ethylene terephthalate)

In order to compare the reactivity of different chemical functionalities against metal (aluminium) deposition on polymer surfaces, spectroscopic vibrational data recorded from different polymers were gathered and compared. Three polymers, poly(vinyl alcohol) (PVOH), poly(acrylic acid) (PAA), and poly(ethylene terephthalate) (PET) were aluminized under ultra-high vacuum with submonolayer incremental steps. High resolution electron energy loss spectroscopy (HREELS) was used to characterize the interface formation at each incremental step. Many vibrational bands were observed for each polymer; their study (intensity and frequency) during metallization gave a rather rich picture of the interfacial reaction mechanisms in terms of first reaction sites and compounds formed. On the PET sample, for example, we could distinguish aromatic and aliphatic C-H vibrations, observe the C=O and C-O-CH2 parts of the molecule, and study their changes during the metallization process.

Multitechnique approach of the surface analysis of fluorinated polyethylene terephthalate

Polyethylene Terephthalate 12-mu-m thick films (Mylar(R)) have been subjected to an industrial gaseous fluorination treatment. The chemical surface modifications of the treated films have been studied with the aid of various surface sensitive techniques (ISS, SSIMS and XPS); thanks to the complementarity of these techniques, the chemical reaction scheme at the surface is emphasized. The ISS technique provides the elemental chemical composition of the first topmost monolayer. In the case of polymers, it is thought that the low carbon sensitivity of ISS is due to the shielding of the carbon atoms by the hydrogen atoms. ISS spectra obtained on fluorinated PET samples show that the fluorination treatment results in the incorporation of fluorine with a slight change of the O/C ratio: this has been interpreted by the substitution of hydrogen atoms from the PET by fluorine which has already been observed on other polymers subjected to the same treatment. Both XPS and SSIMS analyses confirm these results. First, the SSIMS spectra obtained on the fluorinated samples are totally different from those obtained on the untreated PET samples: these spectra exhibit new peaks characteristic of fluorine containing molecular ions similar to those observed from fluorinated polymers such as PVDF or PTFE. Since the secondary ions formation involves ruptures of the polymer chains and some recombination reactions, it is difficult to decide from SSIMS on the exact sites on the PET chains where the hydrogen substitution by fluorine takes place. This was made possible with the help of XPS: the shape of the C1s peak after fluorination of the PET shows that the formation of new CF(x) species (x less-than-or-equal-to 2) occurs on the electron rich benzenic rings of PET rather than on the aliphatic parts of the PET chains. Finally, RBS has been used in order to estimate the depth at which the fluorination treatment has proceeded: this has been estimated to a few tenths of micrometer.

XPS and HREELS Study of the Aluminum/Poly(ethylene terephthalate) Interface and the Influence of the Polymer Surface Pretreatment on Adhesion

Interfacial properties between evaporated metals and polyester films, specially adhesion, are important technological issues in several industrial fields, such as food packaging, audio and video tape and magnetic data storage. The presence of polar functionalities as well as the polymer surface structure are known to be important parameters which affect the metal adhesion on polymers. In this work, poly (ethylene terephthalate) (PET) has been surface modified by various techniques (UV lamp, corona) in order to change its surface structure and chemical composition. Creation and modification of surface chemical functional groups have been analysed by X-ray Photoelectron Spectroscopy (XPS) and a correlation is made with loss or gain of macroscopic adhesion, as measured by peel test. From our results, we also discuss what are the dominating factors that promote the adhesion of a polymer surface with an evaporated metal. Also, some preliminary results of a promising technique, High Resolution Electron Energy Loss Spectroscopy (HREELS), are presented. This vibrational spectroscopy has been used to monitor the in situ creation of an interface between evaporated aluminum and an unmodified PET substrate.

Surface Characterization of Corona Discharge Treated Poly(Ethylene Terephthalate)

The Corona Discharge Treatment (CDT) of polymers is currently performed in industry to improve their adhesive properties in a variety of situations (1–4), for example, the case of thin metal layers deposited on PET films. These compounds are intensively used for food packaging, microcondensers, information supports (audio and video bands, floppy disks)....