Sodium Naphthalenide Diglyme Solution for Etching PTFE, Characterizations and Molecular Modelization

Abstract

Wet etching of polytetrafluoroethylene by sodium naphthalenide dissolved in diglyme solution was investigated experimentally and theoretically. First, the irreversible modification of the polymer surface was analyzed by Raman and XPS spectroscopies, water wetting angle measurements and AFM observations. The drastic changes brought to the surface of PTFE could be clearly demonstrated by these analytical methods. Then, first principle calculations coupled to molecular dynamics (FPMD) were performed to simulate the first steps of the reaction involved in the process of surface modification. It has been shown that fluorine directly attacks vicinal sodium with formation of a pair of sodium fluoride ions without grafting of the naphthalene moiety onto the modified surface. While the formation of the alkene and alkyne bond can be modelized, no spectroscopic signature is observed after rinsing etched PTFE.

Multi‐featured epoxy composites filled with surface‐modified PTFE powders treated by Na‐naphthalenide system

“…As a result of these steps, it was thought that the aforementioned functional groups were obtained on the surface of the PTFE powders 42 . The occurrence of these functional groups such as unsaturation points of CC, CC, CF, and carbonyl and OH groups on the surfaces of PTFE was reported by Roina 34 and Dake and Bhoraskar, 46 and while it was also in the textbook of Polymer Interface and Adhesion book 49 and the study conducted by Ayurova et al 42 The XPS results identified these functional groups on the surfaces of the powders as mentioned. Additionally, the occurrence of carboxyl groups was also reported in Ayurova's 42 study and the textbook of Polymer Interface and Adhesion 49 as shown in Figure 4.…”

“…Moreover, Dake and Bhoraskar 46 reported that when PTFE surfaces were etched by a Na‐naphthalenide complex, bands at 1550–1800 cm −1 in IR spectroscopy were distinctively changed. Roina et al 34 etched PTFE with a Na‐naphthalenide diglyme solution and revealed that the bands that occurred at 1700 cm −1 were due to carbonyls. The IR peaks in our study were observed at similar bands to those in the literature as shown in Figure 1.…”

“…On the contrary, the surface‐modified PTFE powders exhibited two major C1s peaks at 284.66 eV and 285.25 eV successively corresponding to sp2 (CC) and sp3 (CC) carbons. It was thought that the lower C1s peaks at 287.55 eV and 289.59 eV could be related to CCF x  bonds and carbonyl groups 34,35 . The F1s peak of the untreated PTFE powders was single and had a much higher intensity compared to that of the surface‐modified PTFE powders.…”

“…The large decreases in the contact angle values of the surface-modified PTFE in the range between 50 and 60 confirmed this situation. [41][42][43] Apart from Ayurova et al, 42 other researchers such as Miller et al, 44 Borisova et al, 45 Dake and Bhoraska, 46 Jansta et al, 47 and Roina 34 reported functional groups such as conjugated C C unsaturation points, carbonyl groups, and hydroxyl groups available on the surfaces of PTFE treated with Na-naphthalenide systems.…”

“…Moreover, various surface treatment and functionalizing processes of these filling and reinforcement materials such as chemically treated UHMWPE and aramid fibers, 28,29 silane‐treated graphite nanoplatalets, 32 cation–π interaction‐assisted facile preparation of graphene, 21 and the grafting of any polymer with functional groups onto graphene oxide 33 have been more efficient in terms of enhancing the desired properties. However, these systems are not practical to implement, and they require complex processes despite to fact that significant improvements have been achieved with these filling and reinforcement materials in epoxy composites 17,34,35 . Considering the positive and negative aspects of some prominent efficiency studies in detail, Xian et al 26 used short CF and mineral particles such as wollastonite (CaSiO3) to fill an epoxy resin.…”