Polymer partial miscibility

Oxirane Process. In Arco s Oxirane process, tert-huty alcohol is a by-product in the production of propylene oxide from a propjiene—isobutane mixture. Polymer-grade isobutylene can be obtained by dehydration of the alcohol. / fZ-Butyl alcohol [75-65-0] competes directly with methyl-/ fZ-butyl ether as a gasoline additive, but its potential is limited by its partial miscibility with gasoline. Current surplus dehydration capacity can be utilized to produce isobutylene as more methyl-/ fZ-butyl ether is diverted as high octane blending component. 

Partially Miscible Polymer Blends A subclass of polymer blends including those blends that exhibit a window of miscibility, i.e, they are miscible only at certain concentrations and temperatures. 

When two polymers interact or react with each other, they are likely to provide a compatible, even a miscible, blend. Epoxidized natural rubber (ENR) interacts with chloro-sulfonated polyethylene (Hypalon) and polyvinyl chloride (PVC) forming partially miscible and miscible blends, respectively, due to the reaction between chlorosulfonic acid group and chlorine with epoxy group of ENR. Chiu et al. have studied the blends of chlorinated polyethylene (CR) with ENR at blend ratios of 75 25, 50 50, and 25 75, as well as pure rubbers using sulfur (Sg), 2-mercapto-benzothiazole, and 2-benzothiazole disulfide as vulcanizing agents [32]. They have studied Mooney viscosity, scorch... 

Lubricants can be classified as internal or external lubricants. Internal lubricants should be partially miscible with the polymer at processing temperatures (i.e., behave similar to a plasticiser), but phase separate at ordinary temperatures. Whereas plasticisers are completely miscible with the bulk polymer, lubricants have a limited solubility. 

Several attempts have been made to superimpose creep and stress-relaxation data obtained at different temperatures on styrcne-butadiene-styrene block polymers. Shen and Kaelble (258) found that Williams-Landel-Ferry (WLF) (27) shift factors held around each of the glass transition temperatures of the polystyrene and the poly butadiene, but at intermediate temperatures a different type of shift factor had to be used to make a master curve. However, on very similar block polymers, Lim et ai. (25 )) found that a WLF shift factor held only below 15°C in the region between the glass transitions, and at higher temperatures an Arrhenius type of shift factor held. The reason for this difference in the shift factors is not known. Master curves have been made from creep and stress-relaxation data on partially miscible graft polymers of poly(ethyl acrylate) and poly(mcthyl methacrylate) (260). WLF shift factors held approximately, but the master curves covered 20 to 25 decades of time rather than the 10 to 15 decades for normal one-phase polymers. 

The lower critical solution temperature is another crucial polymer property, which, together with the Upper Critical Solution Temperature (UCST), defines fhe fwo solubility boundaries of polymers in solution. Typically, systems are completely miscible below the LCST but only partially miscible above the LCST and completely immiscible above the UCST. 

To understand the mechanism of polyblending, experiments have been carried out with polymeric solution. W. Borchard and G. Rehage mixed two partially miscible polymer solutions, measured the temperature dependence of the viscosity, and determined the critical point of precipitation. When two incompatible polymers, dissolved in a common solvent, are intimately mixed, a polymeric oil-in-oil emulsion is formed. Droplet size of the dispersed phase and its surface chemistry, along with viscosity of the continuous phase, determine the stability of the emulsion. Droplet deformation arising from agitation has been measured on a dispersion of a polyurethane solution with a polyacrylonitrile solution by H. L. Doppert and W. S. Overdiep, who calculated the relationship between viscosity and composition. 

Marin N, Favis BD (2002) Co-continuous morphology development in partially miscible PMMA/PC blends. Polymer 43 4723 1731... 

Blending is yet another way of manipulating the polymer properties. PTMC degrades too slowly to be useful for most drug delivery applications. Blends were prepared in an attempt to enhance and control the drug delivery rate [121]. Films were prepared from PTMC and poly(adipic anhydride) (PAA), which were partially miscible and formed macroscopically homogeneous blends. The PAA was found to act as a plasticizer and facilitated the erosion of PTMC by increasing the porosity and hydration. PTMC-PAA blends offered sustained and controllable release of an incorporated therapeutic substance as shown in Fig. 11 [121]. 

Figure 9.4c and 9.4d represent intermediate cases, 9.4c indicates partial miscibility we see a two-phase system of AB blends with different A/B ratios. This might be the result of segregation into the binodals. Figure 9.4d is called an interphase or a multiphase blend. The system is quasi-homogeneous, but it contains all A/B ratios between cpi = 0 and concentration gradients as a result of non-completed diffusion in a combination of well-compatible polymers. 

Because the components must initially form miscible solutions or swollen networks a degree of affinity between the reacting components is needed. Therefore, most of the investigations into epoxy IPNs have involved the use of partially miscible components such as thermoplastic urethanes (TPU) with polystyrenes [57], acrylates [58-61] or esters which form loose hydrogen-bound mixtures during fabrication [62-71 ]. Epoxy has also been modified with polyetherketones [72],polyether sulfones [5] and even polyetherimides [66] to help improve fracture behavior. These systems, due to immiscibility, tend to be polymer blends with distinct macromolecular phase morphologies and not molecularly mixed compounds. 

A partial miscibility between a linear polyimide and a crosslinked BMI was evidenced when the polyimides and the BMIs were prepared with the same diamine (Fig. 36) [116]. As a consequence the adhesive properties of the blend were better at high temperature than the ones of the linear polymer alone. 

In this work, polyurethane (PU) and epoxy (EP) mixtures were selected for investigation because they are known to form partially miscible IPNs with broad glass transition temperatures. These were first prepared by Frisch et al(6) using a simultaneous polymerization technique in bulk. These materials showed the effects of cross-linking only one polymer component (pseudo-IPN) and intentional grafting between the component polymers. Klempner et al (2) also studied PU/EP IPNs for vibration attenuation. The polyurethanes in this work were chain extended and crosslinked with a 4 1 equivalent ratio of butanediol (BD) and trimethylol propane (TMP). 

What is necessary with a polymer blend in order to achieve the desired breadth of transition is partial miscibility. Complete immiscibility leads to two Tgs unshifted with respect to the Tgs of the components, and complete miscibility leads to the same relatively narrow transitions observed for homopolymers. Of course, with immiscible blends, it is possible to mix two or more polymers with relatively close Tgs and achieve broad damping transitions in that way. Hourston and Hughes (33) have reported broad transitions for polyether ester-polyvinyl chloride (PVC) blends where specific interactions occur between the ether oxygens and the chlorines in the PVC leading to partial miscibility. 

Many patents 81 95 and papers 45 96 104) deal with thermal polymerization. In the case of diene monomer polymerizations (partially miscible solutions yielding oligomers of Mn 500 and polymers of Mn = 1500-11000), or vinyl acetate polymerization (fully miscible solutions yield polymers of Mn = 500-4000) the dependence of yield, polydispersity and functionality has been studied in dependence on various reaction parameters (temperature, time, solvent, etc.). 

A different behavior is observed [76] for bilayers composed of partially miscible polymers below their critical temperature Tc. In this case two pure blend components interdiffuse until the equilibrium of two coexisting phases is established. The above equilibrium state is characterized by the coexistence compositions ( q and (]>2 and the interfacial width w. The relaxation of the initial interface between pure constituents involves two processes (see Fig. 3) ... 

The problems and challenges Inherent to developing useful materials with optimal morphologies and properties from an Immiscible or partially miscible polymer blend are not trivial and have spawned considerable Industrial and academic research. Work on polymer miscibility, compatibilizing agents, reactive systems, and the Influence of flow on the structure and properties of blends Is described in later chapters. 

The most basic question when considering a polymer blend concerns the thermodynamic miscibility. Many polymer pairs are now known to be miscible or partially miscible, and many have become commercially Important. Considerable attention has been focussed on the origins of miscibility and binary polymer/polymer phase diagrams. In the latter case, it has usually been observed that high molar mass polymer pairs showing partial miscibility usually exhibit phase diagrams with lower critical solution temperatures (LCST). 

Transition metal coordination of Cu(II) carboxylate groups and pyridine groups was employed as a means of coupling a telechelic butadiene-base polymer with a randomly functionalized styrenic polymer. Dynamic mechanical analysis (DMA) and differential scanning calorimetry (DSC) indicated partial miscibility of the two polymers and Fourier transform infrared (FTIR) spectroscopy demonstrated that interactions occurred on a molecular level. When compared with blends of PSVP and the free acid derivative of CTB, the compositions based on the transition metal complex had improved dimensional stability at elevated temperatures, though there remains some question as to the stability of the copper salt to hydrolysis. Electron spin resonance (ESR) spectroscopy showed that only the... 

The use of a partly water-miscible solvent in which the drug and polymer is dissolved is shown in Scheme 5. An emulsion is formed on addition of the polymer-drug solution to an aqueous phase containing a stabilizer. Because of the partial miscibility of the first solvent, solvent diffuses from the dispersed droplets into the bulk to provide after some time polymer nanoparticles containing drug. 

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