Functionalization of irradiated PTFE micropowder with methacryl‐ or hydroxy groups for chemical coupling of PTFE with different matrix polymers

Abstract

This article describes the modification of electron beam irradiated polytetrafluoroethylene (PTFE) material (500 kGy) into a functionalised micropowder, bearing methacrylate or hydroxy groups. The aim of this work is to achieve compatibilization of modified PTFE in a variety of matrix polymers, such as elastomers and duromers. It is well known that irradiation of high molecular PTFE in the presence of air, followed by annealing with water vapor, leads to a functionalization of the PTFE micropowder, containing carboxylic acid groups. For sufficient stability of the coupling of the functional groups that are to be introduced via these acid groups, a transformation into amide groups is necessary, and can be performed by the reaction of the electron beam irradiated PTFE with -caprolactam in the first step. The corresponding acid-terminated PTFE-oligoamide is then reacted with functional epoxy monomers, like glycidol or glycidyl methacrylate, to obtain the functionalised PTFE micropowders (PTFE-OH and PTFE-MA). As the number of COOH groups in the electron beam irradiated PTFE is not very high, IR-spectroscopic identification of the functional groups is not very distinct. To find evidence for the existence/reactivity of the additionally introduced functional groups, model reactions have been performed, where PTFE-MA is reacted with methyl methacrylate/AIBN. IR spectroscopic analysis of the reaction products shows characteristic absorption bands of PMMA, indicating successful graft polymerization of PMMA to PTFE-MA. For PTFE-OH, reaction with cyclohexylisocyanate leads to a bisurethane adduct, which shows a strong urethane absorption in the IR spectrum.

Influence of plasma pre-treatment of polytetrafluoroethylene (PTFE) micropowders on the mechanical and tribological performance of Polyethersulfone (PESU)–PTFE composites

“…The incorporation of surface functional groups changes the surface energy and polarity of the PTFE; thereby enabling the formation of inter-molecular forces and leading to an improved dispersion in the composite. Lehmann et al [14,18,19] altered PTFE micro-powders by means of electron beam irradiation to incorporate functional groups for subsequent use in different polymer matrices. However, Shojaei et al [16] have pointed out that not only the radiation beam equipment is expensive; the process in itself is quite difficult to control.…”

Low-Pressure H2, NH3 Microwave Plasma Treatment of Polytetrafluoroethylene (PTFE) Powders: Chemical, Thermal and Wettability Analysis

“…Polytetrafluoroethylene (PTFE) offers outstanding properties such as high chemical inertness, heat resistance and excellent dielectric properties. Owing to its low coefficient of friction, PTFE is widely used as a sintered pure polymer, a reinforcement polymer and as an additive in polymer compounds to improve the friction and wear properties [ 1 , 2 , 3 , 4 , 5 , 6 , 7 , 8 ]. However, in some cases, its applications are hampered due to PTFE’s inherent poor chemical reactivity, low wettability and poor adhesion with other materials [ 3 ].…”

Newly developed chloroprene rubber composites based on electron-modified polytetrafluoroethylene powder

“…It is also well-known that the double bonds in the chloroprene microstructure are sufficiently deactivated by electronegative chlorine atom so that the direct chemical coupling with PTFE powder by the radical coupling mechanism is implausible. However, very recently it has been shown that further functionalization of the electron-irradiated PTFE powder with functional groups such as methacryl or hydroxyl groups for chemical coupling with different matrix polymers is possible [16]. In the present study, PTFE powder produced by electron irradiation bearing -COOH groups have been functionalized in the presence of zinc oxide for chemical coupling with chloroprene rubber.…”