Polybutadiene melting temperature

The /n j -I,4-polybutadiene made by transition-metal catalysis (112,113) is a resin-like material that has two melting temperatures, 50 and I50°C. 

TDI isomers, 210 Tear strength tests, 242-243 TEDA. See Triethylene diamine (TEDA) Telechelic oligomers, 456, 457 copolymerization of, 453-454 Telechelics, from polybutadiene, 456-459 TEM technique, 163-164 Temperature, polyamide shear modulus and, 138. See also /3-transition temperature (7)>) Brill temperature Deblocking temperatures //-transition temperature (Ty) Glass transition temperature (7) ) Heat deflection temperature (HDT) Heat distortion temperature (HDT) High-temperature entries Low-temperature entries Melting temperature (Fm) Modulu s - temperature relationship Thermal entries Tensile strength, 3, 242 TEOS. See Tetraethoxysilane (TEOS)... 

Natta, Porri, Carbonaro and Lugli (25) have prepared copolymers of 1,3-butadiene with 1,3-pentadiene in the whole range of compositions. The properties of the copolymers, in which all butadiene and pentadiene comonomer units are in the trans-1,4 configuration, clearly show the isomorphous replacement between the two types of units. The melting point/composition data show that the copolymer melting temperatures are a regular function of composition and are always comprised between those of trans-1,4-polybutadiene modification II and trans-1,4-polypentadiene. Also the X-ray diffraction spectra of the copolymers show that the trans-1,4-pentadiene units are isomorphous with the trans-1,4-butadiene units crystallized in the crystalline modification of the latter stable at high temperatures (form II). 

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. 

Figure 3.29 Linear moduli G and G" versus frequency shifted via time-temperature superposition to 27°C for a polybutadiene melt of molecular weight 360,000 and of low polydispersity. The dashed line is the prediction of reptation theory given by Eq. (3-67) the solid line includes effects of fluctuations in the length of the primitive path. (From Pearson 1987.)...

The relaxation time of a polybutadiene melt at room temperature (298 K) is 1 s. Estimate the relaxation time of this melt at the glass transition temperature using Table 8.3 and ignoring any modulus scale shift. 

The transition temperatures were essentially the same for a similar type of polymers regardless of molecular weight range In this study. The lower transition (-86 C) In the B-CL of 70-30 wtX dlblock Is associated with Tg of the polybutadiene block and the upper transition (56 C) with the crystalline melting temperature of polycaprolactone segment No polycaprolactone Tg (about -60 C for Its amorphous part) was observed In the B-CL dlblock, evidently because of Its lowr content and proximity to the polybutadiene Tg. It can be detected at -59 C, however. In the S/B-Cl of 33/44-23 wt% dlblock terpolymer. In the latter, the Tg of the S/B block (-20 ) was essentially the same as the random S/B copolymer control which Is coded as S/B-CL 33/44-0 iftZ In Table IV. 

The stmctural dependence of the crystalline melting temperature is essentially the same as that for the glass transition temperature. The only dilTerence is the effect of structural regularity, which has a profound influence on crystallizability of a polymer. T is virtually unaffected by structural regularity. From a close examination of data for semicrystalline polymers it has been established that the ratio Tg/T , (K) ranged from 0.5 to 0.75. The ratio is formd to be closer to 0.5 in symmetrical polymers (e.g., polyethylene and polybutadiene) and closer to 0.75 in unsymmetrical polymers (e.g., polystyrene and polychloro-prene). This behavior is shown in Figure 4.9. 

In Sect. 2.5 a similar two-step melting was discussed for the condis state of trans-1,4-polybutadiene. The c/ -isomer shows in Fig. 2.113 complete gain of the entropy of fusion at a single melting temperature, while the trans isomer loses about 2/3 of its entropy of transition at the disordering transition. The structure of the trans isomer is close to linear, so that conformational motion about its backbone bonds can support a condis crystal sttucture with little increase in volume of the unit cell. 

F. 107. Dissolution or melting temperature of 9% solution of gels and of dilute solution crystals vs mole percent branches hydrogenated polybutadiene gds ( ) ethy ene-vin acetate gds hydrogenateid polybutadiene solution crystals (O chlorinated polyethylene gds [340] ). Reproduced from Macromolecules [Ref. 338] by the courtesy of the authors and of The American Chemical Society... 

Table 6. Glass-Transition Temperature and Melting Temperatures of Selected Polybutadienes...

Polybutadiene. Unlike cis- and trans-1,4-polybutadiene, high vinyl 1,2-polybutadiene has a chiral center which can exist in one of three different stere-ochemically related forms. The material can either be atactic, leading to an amorphous elastomer, or it can be isotactic or syndiotactic, both of which are crystalline. The elastomeric amorphous form has found utility in tire tread applications (271) and although certain molybdenum (272) coordination catalysts can produce this material, commercialization has focused on anionic alkali metal initiators modified with Lewis bases. Of the two crystalline forms, isotactic 1,2-polybutadiene with a melting temperature of 126° C is the most elusive isomer. A few chromium systems based on soluble salts and aluminum alkyls have been reported to give 45% of the isotactic polymer in a mixture of the atactic isomer (273,274). 

Most Ziegler-Natta catalysts for high vinyl 1,2-polybutadiene delds syndiotactic polymer with a melting temperature that ranges between 90 and 220°C depending on the degree of crystallinity. The microstructure of this material was first recognized by Natta (272) in 1955 and can be prepared with cobalt (275-280), vanadium (281), molybdenum (282,283), chromium (274,284), and titanium (285) salts treated with aluminum alkyl co-catalysts. 

There are several groupings of polymers that are of particular interest. Polymers commonly considered to be elastomers at ambient temperature must have low glass temperatures and be either noncrystalline or, if crystallizable, have low melting temperatures. Some typical polymers in this category are poly(l,4-cis-iso-prene), natural rubber, poly(isobutylene), poly(dimethyl siloxane), and poly(l,4-cis-butadiene). Their melting temperatures are 35 °C, 5 °C,(61) —38 °C and 0 °C respectively. Poly(l,4-cis-isoprene), poly(l,4-cis-polybutadiene) and poly(dimethyl siloxane) are all characterized by low values of A Hu. We can assume that... 

Values of glass transition temperature (Tg) and crystalline melting temperature (T ) for the various polybutadiene structures are given in Table 3. CrystaUinity arising from chain stucture regularity can occur... 

GLASS TRANSITION TEMPERATURE AND MELTING TEMPERATURE OF POLYBUTADIENES... 

Fig. 9 (a) Zero pressure isobar in the 1,4-polybutadiene melt. The line shows MD results from the chemically realistic model. The symbols show average densities in the MpT MC simulation for the optimal choices of parameters for different versions of the LJ-type interaction. From Strauch et al. [117]. (b) Comparison between experimental data for polybutadiene melts in the temperature range from 299 to 461 K symbols) and calculations using PC-SAFT dashed curves) or TPTl-MSA solid curves) models. Parameters of the fits are quoted in the figure, where m is the effective degree of polymerization, which is also treated as a fit parameter and a and refer to a nonbonded LJ (12,6) potential). The bond length potential is the FENE -h LJ potential of Sect. 2.2, and no bond angle potential is used. Adapted from Binder et al. [120]... 

Figure 3.8 (a) Melting temperature TJ of rapidly crystallised fractions of PE-based copolymers as determined by DSC. A hydrogenated polybutadiene with ethyl groups ethylene-vinyl acetate copolymer diazoalkane copolymer with propyl side groups X ethylene-1-butene copolymer ethylene-1-octene copolymer, (b) Melting temperature (TJ of branched LDPE. 1 ethylene-propylene copolymer 2 ethylene-1-bntene copolymer 3 branched PE [23]... 

Reproduced with permission from Handbook of Polyolefins Synthesis and Properties, 1st Edition, Eds., C. Vasile and R.B. Seymour, Marcel Dekker, New York, NY, USA, 1993. Copyright Marcel Dekker, 1993. (c) Dilatometric-determined melting temperature of ethylene copolymers versus mole percent of branches. The dashed line represents equilibrium temperature for random copolymers. Experimental results diazoalkane copolymers with methyl branch (O) ethyl branch ( ) propyl branch (A) hydrogenated polybutadiene (A) EVA ( ) [30]... 

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