PMMA/PVDF

The homopolymers poly(methyl methacrylate) and poly-(ethyl methacrylate) are compatible with poly(vinylidene fluoride) when blended in the melt. True molecular com-patibility is indicated by their transparency and a single, intermediate glass transition temperature for the blends. The Tg results indicate plasticization of the glassy methacrylate polymers by amorphous poly(vinylidene fluoride). The Tg of PVdF is consistent with the variation of Tg with composition in both the PMMA-PVdF and PEMA-PVdF blends when Tg is plotted vs. volume fraction of each component. PEMA/PVdF blends are stable, amorphous systems up to at least 1 PVdF/I PEMA on a weight basis. PMMA/ blends are subject to crystallization of the PVdF component with more than 0.5 PVdF/1 PMMA by weight. This is an unexpected result. 

Physical Properties of PMMA—PVdF and PEMA—PVdF Poly blends. 

Tg data for the blends are shown in Figure 1. Results obtained by DTA on PMMA-PVdF blends which had been melt extruded and "annealed at room temperature appeared to be anomalous in terms of the theory for glass transition of copolymers or compatible polymer blends (6). These data indicated a limiting value for Tg of ca. 40°-45°C. However, x-ray examination showed that samples with more than ca, 35% PVdF exhibited a crystalline phase, indicating that some of the PVdF had precipitated. When these systems were re-examined by dilatometry... 

Figure 1. Glass transition temperature of PMMA-PVdF blends...

Figure 2. Comparison of experimental Tg values of PMMA-PVdF blends with theoretical curve based on Fox equation...

Thus, Tg should be a linear function of the volume fraction of each component rather than the weight fraction as implied by the Fox equation. When the Tg data are plotted vs. volume fraction, a reasonable fit is obtained for the PMMA-PVdF polyblends (Figure 3) and excellent agreement for PEMA-PVdF blends (Figure 4). [For these calculations,... 

Thus, the PVdF behaves as a homogeneous plasticizer for the methacrylate polymers. For the PMMA-PVdF system, the compositions with more than 40 wt % PVdF, whose Tgs are below 50 °C, permit crystallization of PVdF as a separate phase. Consequently, the Tg is elevated since the concentration of the diluent is effectively reduced in the amorphous phase. At ambient temperature, this produces the phenomenon of limiting Tg as observed in the original room temperature annealed samples (Figure 1). 

Othfer properties of the PMMA-PVdF system are consistent with the amorphous-crystalline blend model. Thus, the light transmission of films of these blends at room temperature (Figure 5) decreases fairly abruptly as the the PVdF content increases, coincident with the appearance of a crystalline phase. 

Ultraviolet Stability of PMMA—PVdF Poly blends. The potential ultraviolet resistance of this polyblend was of considerable interest. Let us first consider what is known of the photochemical stability of the components. 

For the system PMMA/PVDF one can estimate the volume of mixing according to Eq. (22). As the key-point, the system exhibits both LCST and UCST. The critical points are reported to be about at 325 and 140 °C for 50/50 blends [11], These data can be used to calculate, from Eqs. (18) and (19), the quantities XAB and p. 

PTFEHMWPE PP LDPE HOPE PC PET PMMA PVDF NYLON... 

PMMA sufficiently close to the mixed phase that spin diffusion from it is important. Radial spin diffusion was assumed, with a sphere of intimately mixed phase of radius A and a shell of close PMMA of thickness L-A (up to a point of abutment with a neighbouring sphere). Figure 18.16 shows experimental data for the 60 40 PMMA/PVDF blend, which is fitted to A = 6 A, L = 12 A and 30% isolated PMMA. The same experiment was then employed [81], together with F- C H, F CP, to study the influence of PMMA tacticity on PMMA/PVDF miscibility, yielding evidence for a specific interaction between segments of the two polymers. The mixed PMMA/PVDF phase was determined to have a mean radius of 6-8 A, with some dependence on PMMA tacticity. Large differences were found in the... 

Fig. 18.15. CPMAS spectra of a PMMA/PVDF 60 40 blend (a) C direct CP (contact...

Fig. 18.16. Experimental data for a PMMA/PVDF 60 40 blend, obtained for the carboxyl resonance of PMMA. The solid line is a calculated depolarisation curve. The dashed line represents the offset from 30% of isolated PMMA. [Figure reproduced with permission from Ref. 80.]...

Fig. 18.17. Fraction of isolated PVDF in a 60 40 PMMA/PVDF blend as a function of annealing time at 120 and 140°C. [Figure reproduced with permission from Ref. 92.]...

The reader s attention is also drawn to two reviews [146,147] summarising the work of Veeman and Maas, discussed in Section 18.5, on PMMA/PVDF copolymers and blends. 

PMMA/PVDF miscible 30 wt% of PVDE reduced SH of PMMA at 160X [Kotaka, 1998]... 

PAr/ PVDF PAr-b- PMMA PVDF/PMMA is a miscible blend. Addition of PAr to the PAr/PVDF/PAr-b-PMMA resulted in reduction of PVDF T and an increase of PAr T. These effects were m g enhanced by addition of PAr-b-PMMA. Finer dispersion was obtained for higher block copolymer content. Contact angle measurements, showed that was greatly influenced by the presence of block copolymer. Ahn et al., 1994... 

Mishra et al. [1994] and Bajpai et al. [1994] determined the microhardness of PMMA/PVDF and PMMA/PCTFE blends (Table 11.9) made by solution casting from dimethyl formamide solutions. The solutions containing the two polymers were heated at 110°C for 3 h and were poured into an optically plain glass mold to prepare pellets of the blends. The poured material was annealed at 75°C for 3 h. The samples were cut from the slowly cooled (24 h) pellets for this work. 

Table 11.63. Microhardness of PMMA/PVDF blends [Mishra et al., 1994 Bajpai et at., 1994]...

The best commercial advantages of a polymer blend can be summarized by the word versatility [Olabisi et ah, 1979]. Unfortunately, miscible polymer-polymer blends usually show additivity of the component polymers properties, thus their versatility is limited. Furthermore, tike any other single-phase resin, for most apphcations miscible blends need to be toughened and/or reinforced. Thus, with the exception of PMMA/PVDF blends (primarily used for coatings) there are no miscible blends on the market The interest in miscible polymer blends is for the purpose of compatibUization and judicious selection of the processing conditions that may lead to the spinodal decomposition-type morphology (see Chapter 8 Morphology in this Handbook). 

Scanning electron micrographs (SEMs) of (a,b) polyaniline (PANI) network in 25/25/25/25 polystyrene/polymethyl methacrylate/poly(vinylidene fluoride)/polyaniline (PS/PMMA/ PVDF/PANI) blend after extraction of all phases by dimethylformamide (DMF) followed by freeze drying, and (c,d,e) PANI network in 15/20/15/25/25 PS/PS-co-PMMA/PMMA/PVDF/ PANI blend after extraction of all phases by DMF followed by freeze drying. (Reproduced from Ravati, S., and Favis, B. D. 2010. Low percolation threshold conductive device derived from a five-component polymer blend. Polymer 51 3669-3684 with permission from Elsevier.)... 

Conductive polyaniline (PANI) formed the core of the five-component continuous system that also included high-density polyethylene (HOPE), polystyrene (PS), poly(methyl methacrylate) (PMMA), and poly(vinylidene fluoride) (PVDF) along with PS-co-PMMA copolymer. Figure 1.10 shows the SEM micrographs of PANI network in PS/PMMA/PVDF/PANI and PS/PS-co-PMMA/PMMA/PVDF/PANI blends after extraction of all phases by DMF followed by freeze drying. 

On the other hand as mentioned above, presence of polymer-polymer interactions can also affect the polymer conformations. PVDF exhibits short bond sequences tt and tg the probability of a gg bond is negligible because of steric hindrance. Energy calculations emphasize that PMMA conformation remains close to all trans conformation of PVDF. In our study, presence of graphene p>articles along with PMMA chains makes it complex due to PVDF-PMMA, PVDF-graphene and PMMA-graphene interactions. 

PVDF/PMMA PVDF blends with PMMA and review of procedures used to determine X12 3... 

---