Polybutadiene tensile strength

The physical properties of low melting point (60—105°C) syndiotactic polybutadienes commercially available from JSR are shown in Table 1. The modulus, tensile strength, hardness, and impact strength all increase with melting point. These properties are typical of the polymer made with a cobalt catalyst modified with triphenylphosphine ligand. 

This lower has a number of ramifications on the properties of polybutadiene. For example, at room temperature polybutadiene compounds generally have a higher resilience than similar natural rubber compounds. In turn this means that the polybutadiene rubbers have a lower heat build-up and this is important in tyre applications. On the other hand, these rubbers have poor tear resistance, poor tack and poor tensile strength. For this reason, the polybutadiene rubbers are seldom used on their own but more commonly in conjunction with other materials. For example, they are blended with natural rubber in the manufacture of truck tyres and, widely, with SBR in the manufacture of passenger car tyres. The rubbers are also widely used in the manufacture of high-impact polystyrene. 

Notable among the alternative materials are the MBS polymers, in which methyl methacrylate and styrene are grafted on to the polybutadiene backbone. This has resulted in two clear-cut advantages over ABS. The polymers could be made with high clarity and they had better resistance to discolouration in the presence of ultraviolet light. Disadvantages of MBS systems are that they have lower tensile strength and heat deflection temperature under load. 

A new process to develop interface vulcanization is grafting of selective accelerators onto a polymer chain, which in the subsequent process of vulcanization acts as an effective cure accelerator for the second polymer component in the blend. Beniska et al. [6] prepared SERFS blends where the polystyrene phase was grafted with the accelerator for curing SBR. Improved hardness, tensile strength, and abrasion resistance were obtained. Blends containing modified polystyrene and rw-1,4-polybutadiene showed similar characteristics as SBS triblock copolymers. 

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)... 

S-B, Polystyrene 1,2-Polybutadiene Polystyrene Polybutylene Improved tensile strength and elongation... 

Tensile Strength Data from Electron Beam Cross-Linked Polybutadiene and Its Copolymers... 

The comparative effect of the polystyrene and poly-2,6-dichlorosty-rene fillers on the tensile strength of a polybutadiene vulcanizate is shown in Figure 6. Despite the large difference in Tg values for these fillers, there is no difference in their effect on the vulcanizate. This is illustrated further by the failure envelope plot shown in Figure 7, where the data points for the two fillers, at equal volume fraction, appear to coincide quite well. The fact that all the points fall on the same envelope is a good indication of the constant crosslink density for these vulcanizates. Thus, the similarity in effect of these two fillers appears to be more related to their similar modulus values. 

Figure 6 is also useful in demonstrating the difference in viscoelastic response of polybutadiene and SBR vulcanizates. The higher values of tensile strength of the latter, at any given temperature, can obviously be ascribed to the substantially higher Tg of the SBR since the crosslink densities of the two vulcanizates are similar. 

Figure 6. Tensile strength of polybutadiene with poly-2,6-dichlorostyrene (DC) filler. Strain rate, 2 inches/min.

The Teflon-filled vulcanizates have not been included until now since this filler must be considered as a special case, involving poor adhesion at the filler-rubber interface. The marked difference between Teflon and the other fillers is seen in Figure 9, which shows that the Teflon filler exerts only a slight effect on the tensile strength of the polybutadiene vulcanizate. As a matter of fact, although this filler does increase the strength slightly at temperatures above 0°C, it actually appears to de-... 

The constancy of tensile strength of the SIS polymers, above a certain minimum end-block size, can be explained best on the basis of efficiency of phase separation. Since the latter depends on the three parameters—Le.y incompatibility of the two blocks, composition ratios, and block size—the SIS polymers must undergo a much better phase separation at equivalent composition and block size than the SBS polymers, and the latter require a higher styrene content and a longer polystyrene end block to accomplish good phase separation. This is in accord with the generally accepted fact that polyisoprene is more incompatible with polystyrene than is the case for polybutadiene. 

Finally, it is instructive to compare the temperature effect on the tensile strength of the SBS and SIS block polymers. As noted previously (Figure 6) the tensile strength of an elastomer vulcanizate can be related to the difference between the test temperature and the Tg of the elastomer, in accordance with the viscoelastic theory of tensile strength. Since the Tg values for polyisoprene ( — 65°C) and polybutadiene ( —95°C) differ... 

For example, these workers (103) found that polybutadiene can be successfully metalated by n-BuLi-TMEDA, and the product subsequently used to graft styrene monomer to form poly(butadiene-g-styrene). This result showed that the grafting efficiency was 100%. Catalyst efficiency was found to be 75-95%. Thus, the n-BuLi-TMEDA metalating and grafting system is particularly effective for polydiene backbones. In fact, Falk and Schlatt (104) showed that poly(butadiene-g-styrene) has excellent tensile strength. 

Crystallization of oriented chains is, in various respects, important for the polymer properties. The fact has been mentioned before, that stereospecific rubbers such as cis-1,4 polybutadiene can crystallize when under strain. The spontaneously formed crystals contribute strongly to the strength of the vulcanizate. A vulcanized natural rubber has, without carbon black reinforcement, a tensile strength of about 40 MPa, whereas an unreinforced SBR breaks at about 3 MPa. (With SBR a high tensile strength can only be reached with carbon black.)... 

Functionalized, liquid polybutadiene derivatives have also been developed as hybrid flexiblizers for epoxy resins. Carboxyl-terminated butadiene/acrylonitrile polymers, butadiene homopolymers, and maleic anhydride-amino acid grafted butadiene homopolymers have been used as flexibilizers to impart good low-temperature strength and water resistance to DGEBA-based epoxy adhesives. An epoxy system toughened by polybutadiene with maleic anhydride is claimed to provide a hydrophobic backbone, low viscosity, softness, and high tensile strength and adhesion (Table 7.10). 

The physical data (dynamic modulus, tensile strength, hardness, elongation at break) were investigated by many groups 202,205 210) (cf., Table 4.5 as an example). These results show that the elastomer physical properties become better by increasing the molar ratio of low-molecular-weight diol to hydroxyl-terminated polybutadiene. 

SBR etc., yet it has been covulcanized with those rubbers to provide useful materials (4). In this work, we have found that poly(isobutylene-co-P >inene) with 10 mole% unsaturation can also be cocured with a high cis- l,4-p<%lHit ene rubber. Covulcanization has been demonstrated by an experiment in which poly(isobutylene-co- -pinene) phis cis-l,4.polybutadiene were mixed cm a laboratory mill for 40 minutes, cured (30 minutes at 160°) and the vulcanizate extracted with n-hexane (24 hours at 65°). The fact that the amount of extractables was 2% indicates a measure of co-vulcanization. The covulcanizate exhibited a tensile strength of 175 kg/cm and elongation at break of 300%. 

With barium-containing anionic initiators [88] polybutadiene with a high trans content [89] and less then 5 % of vinyl double bonds can be synthesized. This rubber does not crystallize at room temperature but can undergo crystallization upon stretching. The properties of rubber, e. g., green strength, tackiness of the compound, as well as tensile strength of the vulcanizate, are much improved by strain-induced crystallization. 

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