Chemistry of fluorocarbon elastomers

TFE Terpolymers: Once Promising - Are There Still Perspectives in the 21st Century: Synthesis, Characterization, and Properties-Part I

Polytetrafluoroethylene (PTFE) exhibits outstanding properties such as high-temperature stability, low surface tension, and chemical resistance against most solvents, strong acids, and bases. However, these traits make it challenging to subject PTFE to standard polymer processing procedures, such as thermoforming and hot incremental forming. While polymer processing at temperatures above the melting point of PTFE is already demanding, the typically large molar mass of PTFE results in extremely high melt viscosities, complicating the processing of PTFE. Also, PTFE tends to decompose at temperatures close to its melting point. Therefore, fluoropolymers obtained by copolymerizing tetrafluoroethylene (TFE) with various co-monomers are studied as alternatives to PTFE (e.g., fluorinated ethylene-propylene (FEP)), combining its advantages with better processability. TFE terpolymers have emerged as desirable PTFE alternatives. This review provides an overview of the synthesis with various comonomers and microstructural analysis of PTFE terpolymers and the relationships between the microstructures of TFE terpolymers and their properties.

From Formulation to Application: Effects of Plasticizer on the Printability of Fluoro Elastomer Compounds and Additive Manufacturing of Specialized Seals

This work investigated material extrusion additive manufacturing (MatEx AM) of specialized fluoroelastomer (FKM) compounds for applications in rubber seals and gaskets. The influence of a commercially available perfluoropolyether (PFPE) plasticizer on the printability of a control FKM rubber compound was studied using a custom-designed ram material extruder, Additive Ram Material Extruder (ARME), for printing fully compounded thermoset elastomers. The plasticizer's effectiveness was assessed based on its ability to address challenges such as high compound viscosity and post-print shrinkage, as well as its impact on interlayer adhesion. The addition of the PFPE plasticizer significantly reduced the FKM compound's viscosity (by 70%) and post-print shrinkage (by 65%). While the addition of the plasticizer decreased the tensile strength of the control compound, specimens printed with the plasticized FKM retained 34% of the tensile strength of compression-molded samples, compared to only 23% for the unplasticized compound. Finally, the feasibility of seals and gaskets manufacturing using both conventional and unconventional additive manufacturing (AM) approaches was explored. A hybrid method combining AM and soft tooling for compression molding emerged as the optimal method for seal and gasket fabrication.

A Novel Low-Temperature Extrusion Method for the Fused Filament Fabrication of Fluoroelastomer Compounds

In this work, an additive manufacturing process for extruding fully compounded thermosetting elastomers based on fluorine-containing polymer compositions is reported. Additive manufacturing printers are designed with a dry ice container to precool filaments made from curable fluoroelastomer (FKM) and perfluoroelastomer (FFKM) compounds. A support tube guides the stiffened filament towards the printer nozzle. This support tube extends near the inlet to a printer nozzle. This approach allows low-modulus, uncured rubber filaments to be printed without buckling, a phenomenon common when 3D printing low-modulus elastomers via the fused deposition modeling (FDM) process. Modeling studies using thermal analyses data from a Dynamic Mechanical Analyzer (DMA) and a Differential Scanning Calorimeter (DSC) are used to calculate the Young's modulus and buckling force, which helps us to select the appropriate applied pressure and the nozzle size for printing. Using this additive manufacturing (AM) method, the successful printing of FKM and FFKM compounds is demonstrated. This process can be used for the future manufacturing of seals or other parts from fluorine-containing polymers.

A highly transparent ionogel with strength enhancement ability for robust bonding in an aquatic environment

An underwater adhesive with strong, fast and stable adhesion ability has become an urgent requirement for various industrial applications. Herein, a highly transparent ionogel based on a fluorine-rich poly(ionic liquid) and the corresponding ionic liquid monomer has been developed and used as an underwater adhesive. Strong and stable underwater adhesion can be realized by taking advantage of the excellent interface adaptability and high mechanical strength of this ionogel. The underwater adhesion strength could reach as high as 5.18 ± 0.27 MPa. In addition, it can also realize robust bonding over a wide pH range (0-14). A waterproof transparent tape based on the ionogel has also been developed and it can carry out repair work in wet and aquatic environments.

Crosslinked terpolymers of vinylidene fluoride, perfluoro-3,6-dioxa-4-methyl-7-octene sulfonyl fluoride, and cure site monomers for membranes in PEMFC applications

Radical terpolymerisations of perfluorintaed ω-cyano monomers, vinylidene fluoride and perfluoro(4-methyl-3,6-dioxaoct7-ene) sulfonyl fluoride are presented.

Regulating Dielectric and Ferroelectric Properties of Poly(vinylidene fluoride-trifluoroethylene) with Inner CH=CH Bonds

Poly(vinylidene fluoride) (PVDF) based ferroelectric polymers have attracted considerable attention both academically and industrially due to their tunable ferroelectric properties. By pinning the conformation of the polymer chain and the ferroelectric phase physically or chemically, the ferroelectric behaviors of PVDF based polymers could be finely turned from normal ferroelectric into relaxor ferroelectric, anti-ferroelectric like, and even linear dielectric. Besides high energy electron irradiation and chemical copolymerization with the bulky monomers, in this work, an alternative strategy is presented to regulate the dielectric and ferroelectric performances of PVDF based ferroelectric polymer for the first time. CH=CH bonds with the desired content are inserted by a controlled dehydrofluorination reaction into a poly(vinylidene fluoride-trifluoroethylene) (P(VDF-TrFE)) copolymer (TrFE refers to trifluoroethylene) synthesized from the hydrogenation of P(VDF-CTFE) (CTFE refers to chlorothrifluoroethylene). The influence of the CH=CH bonds along with the fabrication conditions on the crystallization and ferroelectric relaxation of the resultant copolymers (referred to P(VDF-TrFE-DB)) was carefully characterized and discussed. The nonrotatable CH=CH bonds result in depressed dielectric and ferroelectric performances in the as-cast films by confining the orientation of ferroelectric grains in P(VDF-TrFE). The normal ferroelectric performance of P(VDF-TrFE) is turned into anti-ferroelectric like behavior in the resultant P(VDF-TrFE-DB). The cleavage of CH=CH bonds is responsible for the recovery of the ferroelectric behavior in the annealed samples. Uniaxial stretching favors the alignment of the polymer chain and ferroelectric domains, which may address the further regulated ferroelectric characters in the stretched samples.

Inserting –CHCH– into P(VDF-TrFE) by C–F activation mediated with Cu(0) in a controlled atom transfer radical elimination process

A controlled single electron transfer radical elimination (SET-RE) reaction has been successfully developed to introduce CHCH bonds into poly(vinylidene fluoride-trifluoroethylene) (P(VDF-TrFE)).

The functionalization of fluoroelastomers: approaches, properties, and applications

This review seeks to give an overview of different approaches to prepare functional fluoroelastomers for modern industries.

Crosslinking of low density polyethylene with octavinyl polyhedral oligomeric silsesquioxane as the crosslinker

We report a new strategy for the crosslinking of LDPE using octavinyl polyhedral oligomeric silsesquioxane as the crosslinker, which dramatically decreases the amount of dicumyl peroxide and thus avoids the chain scission, scorch, and production of small pores in the conventional peroxide crosslinking strategy.