Hydrocarbon polymers, stability

Introducing long aliphatic chains into a stabilizer molecule decreases volatility and increases solubility in hydrocarbon polymers. This improves performance. However, it also increases the equivalent weight of the active moiety. Di- and polyphenoHc antioxidants combine relatively low equivalent... 

Macromolecules have also been specifically designed and synthesized for use as emulsifiers for lipophilic materials and as stabilizers in the colloidal dispersion of lipophilic, hydrocarbon polymers in C02. We have demonstrated the amphiphilicity of fluorinated acrylate homopolymers, such as PFOA, which contain a lipophilic, acrylate like backbone and C02-philic, fluorinated side chains (see Fig. 3) [103]. It has been demonstrated that a homopolymer which physically adsorbs to the surface of a polymer colloid prevents agglomeration by the presence of loops and tails (see Fig. 4) [113]. The synthesis of this type of... 

Before fluorination, the dielectric constant ofpoly(bisbenzocyclobutene) was 2.8, and this value was reduced to 2.1 after plasma treatment. No data were reported in the paper on characterization of structure or properties, except for the dielectric constant of the modified poly(bisbenzocyclobutene). The authors did report that the thermal stability offluorinatedpoly(vinylidenefluoride) was inferior to the original poly(vinylidenefluoride) when treated in a similar way. One of the probable reasons for the low thermal stability is that the NF3 plasma degraded the polymer. According to their results, the thickness of fluorinated poly(bisbenzo-cyclobutene) was reduced by 30%. The same phenomenon was observed for other hydrocarbon polymers subjected to the NF3 plasma process. A remaining question is whether plasma treatment can modify more than a thin surface layer of the cured polymer Additionally, one of the side products generated was hydrogen fluoride, which is a serious drawback to this approach. 

In particular, crude polymerizates prepared in the presence of AIBN as initiator, which yield resonance stabilized radicals (17) that are unable to extract hydrogen from hydrocarbon supports (I, 18) show the same content of non-extractable rubber as that of the polymerizates prepared in the presence of active radicals in the hydrogen extraction from hydrocarbon polymers, such as those derived from the decomposition of benzoyl peroxide. 

Degradation of a hydrocarbon polymer starts at or before the processing stage and in many aspects this history of the sample is the least studied parameter of the degradation. The combination of high temperature, low oxygen concentration, and shear stress as it occurs, e.g., in extruders is very difficult to simulate in the laboratory. For this reason, the development of melt stabilizers is still very empirical, the problem being considerably less studied than that in the case of other stabilizers. 

For the stabilization of various insoluble hydrocarbon polymers in carbon dioxide, it has been found that no one surfactant works well for all systems. Therefore it has become necessary to tailor the surfactants to the specific polymerization reaction. Through variation of not only the composition of the surfactants, but also their architectures, surfactants have been molecularly-engineered to be surface active—partitioning at the interface between the growing polymer particle and the CO2 continuous phase. The surfactants utilized to date include poly(FOA) homopolymer, poly(dimethylsiloxane) homopolymer with a polymerizable endgroup, poly(styrene-b-FOA), and poly(styrene-b-dimethylsiloxane). Through the utilization of these surfactants, the successful dispersion polymerization of methyl methacrylate (MMA), styrene, and 2,6-dimethylphenol in CO2 has been demonstrated. 

ADMET polymerization has been used to integrate silicon into linear and network hydrocarbon polymers in an attempt to produce novel materials with enhanced thermal and mechanical stability. While ADMET has been used to produce copolymeric architectures unattainable through conventional methods, application of this polymerization to synthesis is feasible only if the silicon-based functionality does not inhibit metathesis. This research, initiated in the early 1990s by Wagener and colleagues, has shown that the silane and siloxane... 

N. Miskolczi, L. Bartha, G. Deak and B. lover. Thermal degradation of municipal plastic waste for production of fuel-like hydrocarbons. Polymer Degradation and Stability, 86, 357-366 (2004). 

High solubility of stabilizers is an essential requirement for a good physical retention of a stabilizer in a polymer [27]. Molecules of most stabilizers have relatively high polarity and their solubility in unpolar hydrocarbon polymers is, therefore, only low. Microscopic domains consisting of aggregated polar stabilizers and surface exudates can be formed and are one of reasons for the uneven distribution of a stabilizer in the host polymer as well as for the physical loss of a stabili r. 

DSC analysis of the polymer revealed a higher Tg (178 °C) than those of many other known hydrocarbon polymers, such as thermally resistant syn-diotactic polystyrene. The polymer does not decompose up to 300 °C in the TG analysis and shows good thermal stability. These results as well as the 13C NMR data indicate a rigid polymer structure. 

The polyethylene latexes obtained in the different emulsion polymerization procedures using the various aforementioned nickel(II) complexes display average particle diameters of 100 to 600 nm. A number of anionic surfactants or neutral stabilizers are suitable, i.e. compatible with the catalysts and capable of stabilizing the latex. Solids contents of up to 30% have been reported to date. A typical TEM image is shown in Fig. 7.2. By comparison to smooth, spherical latex particles of amorphous polystyrene as a well studied hydrocarbon polymer prepared by free-radical emulsion polymerization, the ruggedness of the particles shown can be rationalized by their high degree of crystallinity. 

Mn 2 to 4). In olefin polymerization as well as CO copolymerization, a Umited conversion of liquid 1-olefin (co)monomers is yet to be overcome in many cases. As an example of properties that could find potential appUcation, polyolefins contain a negligible proportion of double bonds by comparison to styrene-butadiene copolymers, a hydrocarbon polymer currently prepared by free-radical emulsion polymerization on a large scale. This can result in a considerably higher stability towards UV-Ught and air of polymer films formed from polyolefin latexes. 

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