Polybutadienes thermal properties

This work investigates the behaviour of elastomeric chains (polybutadienes of identical molecular weight but different microstructures) in the close vicinity of carbon black surfaces in order to attain a better understanding of the structure and properties of interphases. Elastomer-filler interactions are assessed through the study of the thermal properties and NMR relaxation characteristics of the corresponding materials. MAS solid-state NMR provides information on the effect exerted by polymer-filler interactions on the mobility of the various constitutive species of the macromolecular backbone. 

In addition to improving the miscibility of polymers in blends, hydrogenbonding interactions between the side-groups of covalent polymers may also lead to network polymers with interesting properties. For example, polybutadienes modified with 4-(3,5-dioxo-l,4,4-triazlidine-4-yl) benzoic acid (33) form such structures. The mechanical and thermal properties of these polymers differ from unmodified polybutadienes as the result of hydrogen-bonded crosslinks (Fig. 22)... 

Figure 5.22 presents examples of the thermal properties of PEO and PBd-h-PEO polybutadiene-h-poly(ethylene oxide) before and after infiltration in AAO templates. 

The other possibility is to coat the silica with a polymer of defined properties (molecular weight and distribntion) and olefin groups, e.g., polybutadiene, and cross-linked either by radiation or with a radical starter dissolved in the polymer [32]. This method is preferentially used when other carriers like titania and zirconia have to be surface modified. Polyethylenimine has been cross-linked at the snrface with pentaerythrolglycidether [41] to yield phases for protein and peptide chromatography. Polysiloxanes can be thermally bonded to the silica surface. Other technologies developed in coating fnsed silica capillaries in GC (polysiloxanes with SiH bonds) can also be applied to prepare RP for HPLC. 

The reaction was carried out using up to 10% by weight of polybutadiene based on PVC. However, to avoid changing the properties of PVC other than the thermal stability, the preferred extent of reaction was 3-6%. 

The above thermal analysis studies demonstrated the enhanced thermal stability of POSS materials, and suggested that there is potential to improve the flammability properties of polymers when compounded with these macromers. In a typical example of their application as flame retardants, a U.S. patent39 described the use of preceramic materials, namely, polycarbosilanes (PCS), polysilanes (PS), polysilsesquioxane (PSS) resins, and POSS (structures are shown in Figure 8.6) to improve the flammability properties of thermoplastic polymers such as, polypropylene and thermoplastic elastomers such as Kraton (polystyrene-polybutadiene-polystyrene, SBS) and Pebax (polyether block-polyamide copolymer). 

The specific volume and expansion coefficient of the solution-blended material are shown in Figure 6, along with data for pure polybutadiene and pure polystyrene. None of the three polymers has any distinguishing features below the polystyrene Tg> illustrating that the observed transition and minimum are the results of the unique structural morphology of the block copolymers. It should be noted that the substantial difference in the thermal expansion coefficients of polybutadiene and polystyrene can be expected to be an important factor affecting the structure and properties of block copolymer samples prepared under various conditions. 

The compression-molded part, by definition, does not have flow-induced orientation. Comparison of compression-molded part properties with those of an injection-molded part can show the effect of melt temperature on properties. In the compression-molded article without flow-induced orientation, the impact strength remains constant until a certain melt temperature is surpassed and then decreases. This thermal degradation effect can be attributed to the polybutadiene component, which acts as an initiation site for oxidative degradation of the matrices. 

Improved ABS-similar resins can be obtained by grafting SAN onto ethylene-propylene-diene terpolymers (EPDMs) which contain, usually, a much lower degree of unsaturation than polybutadiene, thus achieving hi er thermal-oxidative resis-tance However, only EPDMs containing a sufficient amount (7—10 double bonds per 1,000 C atons) of reactive unsaturations, e.g. ethylidene or isopropylidene groups, display a grafting efficiency sufiident to bring about compatibility of the ssy i se with the rubbery one and hence satisfactory final properties. 

Polybutadiene, CAS 9003-17-2, is a common synthetic polymer with the formula (-CH2CH=CHCH2-)n- The cis form (CAS 40022-03-5) of the polymer can be obtained by coordination or anionic polymerization. It is used mainly in tires blended with natural rubber and synthetic copolymers. The trans form is less common. 1,4-Polyisoprene in cis form, CAS 9003-31-0, is commonly found in large quantities as natural rubber, but also can be obtained synthetically, for example, using the coordination or anionic polymerization of 2-methyl-1,3-butadiene. Stereoregular synthetic cis-polyisoprene has properties practically identical to natural rubber, but this material is not highly competitive in price with natural rubber, and its industrial production is lower than that of other unsaturated polyhydrocarbons. Synthetic frans-polyisoprene, CAS 104389-31-3, also is known. Pyrolysis and the thermal decomposition of these polymers has been studied frequently [1-18]. Some reports on thermal decomposition products of polybutadiene and polyisoprene reported in literature are summarized in Table 7.1.1 [19]. 

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