Fluoropolymers illustration

Figure 11.7 Schematic fatigue data for fluoropolymers illustrating the relation between applied stress (S) and the number of cycles to failure (N).

Fluorinated Cyclic Compound, Polymerizable Fluommonomer, Fluoropolymer Polymeric florinated norbomane - and terpolymers are illustrated below. 

When the relation between D and M is established, we can easily convert G(D) obtained by dynamic LLS into a differential molecular weight distribution, such as fw(M). We have successfully applied the above methods to various kinds of polymeric and colloidal systems, such as for Kevlar [15, 23], fluoropolymers (Tefzel Teflon) [12,30-35,52], epoxy [53-55],polyethylene [56,57], water-soluble polymers [18,50-51,58,59], copolymers [60-62], thermoplastics [63-65] and colloids [66-72]. Three of those applications are illustrated below. 

PVDF. This polymer can contain head-to-head and tail-to-tail sequences, as illustrated in Figure 7-25. Because the 19F nucleus has a spin number of 1/2 and its natural abundance is 100%. 19F NMR spectroscopy is a powerful tool for studying fluoropolymers like PVDF. The fluorine atoms are the little yellow balls and you ll notice that one of the units in Figure 7-25 has been put in backwards, giving a head-to-head and tail-to-tail sequence. The peaks marked A, B, C and D in the spectrum of PVDF (Figure 7-26) correspond to the fluorine atoms labeled in the same way in the figure. Of course, what you would really like to know is the number fraction of VDF monomers that are incorporated backwards into the chain. This information can be obtained from the relative intensities of the bands, but to extract it we have to revisit probability theory. (Oh no the nightmare continues )... 

Selected testing and analytic techniques (Table 10.5) are briefly described in the following sections. An understanding of each method is necessary for the proper application and interpretation of results. Some of these techniques are specific to non-fluori-nated thermoplastics and may require modification when applied to fluoropolymers. Examples of the results of applying some of these techniques to fluoroplastic are presented to illustrate their use. The reader is referred to ASTM methods for additional details regarding the measurement of properties and characterization of the plastics. 

Fluoropolymers, as well as other thermoplastics, exhibit a complicated nonlinear response when subjected to loads. The behavior is characterized by initial linear viscoelasticity at small deformations, followed by distributed yielding, viscoplastic flow, and material stiffening at large deformations until ultimate failure occurs. The response is further complicated by a strong dependence on strain rate and temperature, as illustrated in Fig. 11.1. It is clear that higher deformation rates and lower temperatures increase the stiffness of the material. 

The impressive development in molecular simulation stems from important improvement in both codes and computers. It made available accurate atomistic simulation of fluorine derivatives. Depiction of the SPF is most commonly achieved by quantum calculations. The major difficulty in describing interactions involving fluorine atoms actually lies in a correct description of the electrostatic effects [38]. Crystal unit cell dimensions [39,40] and the thermal behavior of fluoropolymers [41 3] were thus originally difficult to reproduce. Dihedral potential energy (Equation 6.3) that plays a central role in the backbone dynamics was also incorrectly depicted. In this section, illustrative examples of force fields specifically dedicated to fluoropolymers and more transferable force fields are reviewed. 

Fluoropolymers, such as PVDF, PC l FE, and their copolymers, comprise monomer units with pendent secondary fluorine/chlorine atoms, which are potential ATRP initiators. In principle, graft copolymerization initiated from these secondary halides should be possible to allow the preparation of functional graft chains, even though the reaction suffers from low initiation efficiency and requires high reaction temperature. Russell et al. reported the graft copolymerization of St and fm-butyl acrylate (tBA) directly from the secondary chlorine atoms in P(VDF-co-CTFE) via ATRP and illustrated the ability of fluorine atoms to activate the chlorine atoms toward... 

Other researchers have attempted to coat aluminum particles directly with an acid, creating fluoropolymer chains that attach to the alumina shell surrounding the aluminum core particle, as illustrated in Figure 15.1 [15]. The acid shell accounts for a small percentage of the total mixture such that the mixture also requires another oxidizer to balance the reaction. This approach is referred to as surface functionalization of aluminum particles and has shown great success in controlling the reactivity of a mixture [15]. 

In this chapter, we describe a variety of methodologies for applying multidimensional NMR (mostly 2D- and some 3D-NMR) for the characterization of fluoropolymers. Space limitations preclude a comprehensive survey of the literature. Instead, a few of the primary methodologies are described involving combined use of multidimensional NMR methods for structure elucidation. Then, a selected group of papers were reviewed to illustrate the applications of these methodologies to the characterization of some of the most common classes of fluoropolymers, including homo- and copolymers with poly(vinylidene fluoride), fluorinated polyethers, fluori-nated ionomers, poly(vinyl fluoride) and its copolymers, and polytetrafluoroethylene (PTFE) and its copolymers. 

SANS has been used widely to study the way in which these molecules self-assemble into aggregates (micelles, microemulsions etc.) in aqueous media [4, 26, 27]. The possibility of forming analogous micelles in SCFs has been debated for a decade [28,29] and has subsequently been demonstrated via SANS [30, 31], SAXS [32], and other techniques [33]. These micelles consist of a CO2-phobic core surrounded by a C02-philic (fluoropolymer) shell and Fig. 7.4 shows a schematic representation of such micellar aggregates both in aqueous and in C02-based systems. SANS has illustrated the way in which polystyrene may be solubilized by means of polystyrene-poly(fluorooctyl acrylate) (PS-PFOA) stabilizers, which form... 

A typical fluoropolymer coating line has several pieces of equipment as summarized in Table 8.3 and illustrated in Fig. 8.18. 

Table 8.11 contains die and tip size information for various resins and wire sizes for a number of fluo-ropolymers with different properties. Melt flow rate data for the polymers of Table 8.11 is shown in Table 8.12. The combination of MFR data and the size information illustrates the effect of molecular weight (lower for higher MFR) on tooling selection for different fluoropolymers for various wire gauges.

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