Stress-strain polybutadiene

B 1,481.2 1,4-Polybutadiene (low vinyl) 1,2-Polybutadiene (high vinyl) Polyethylene Polybutylene Improved material stress-strain properties... 

Some typical stress-strain curves for a carboxy-terminated polybutadiene proplnt (CTPB) containing 86% solids are given in Figure 8, and for a PBAA propellant (see Table 13) containing 83% solids in Figure 9 (Ref 52). The authors concluded that the CTPB proplnts studied were highly susceptible to humidity degradation... 

The influence of ambient aging at 70°F and accelerated aging at 160°F on the stress-strain behavior of carboxy-terminated polybutadiene, polybutadiene-acrylic acid, polybutadiene-acrylic acid-acrylonitrile, and hydroxy-terminated polybutadiene composite propints is shown in Figures 10 and 11. The elastomers and curative agents for these formulations are listed below... 

The information on physical properties of radiation cross-linking of polybutadiene rubber and butadiene copolymers was obtained in a fashion similar to that for NR, namely, by stress-strain measurements. From Table 5.6, it is evident that the dose required for a full cure of these elastomers is lower than that for natural rubber. The addition of prorads allows further reduction of the cure dose with the actual value depending on the microstructure and macrostructure of the polymer and also on the type and concentration of the compounding ingredients, such as oils, processing aids, and antioxidants in the compound. For example, solution-polymerized polybutadiene rubber usually requires lower doses than emulsion-polymerized rubber because it contains smaller amount of impurities than the latter. Since the yield of scission G(S) is relatively small, particularly when oxygen is excluded, tensile... 

Tristar polybutadienes prepared by the intermediacy of lithium acetal initiators were also converted to three dimensional networks in a liquid rubber formulation using a diisocyanate curing agent. Table IV shows normal stress-strain properties for liquid rubber networks at various star branch Hn s. It can be seen that as the branch Mn increases to 2920, there is a general increase in the quality of the network. Interestingly, the star polymer network with a star branch Mn of 2920 (Mc=5840) exhibits mechanical properties in the range of a conventional sulfur vulcani-zate with a Me of about 6000-8000. 

Fisher124,125 has studied the stress-strain and optical properties of three SBS block copolymers containing, respectively, 31,40 and 49% polystyrene as a function of temperature. He has shown that these materials are two phase systems in which the polybutadiene chains form an elastomeric phase and the polystyrene chains a glassy phase acting as physical crosslinks. Fisher126 has also obtained electron micro-... 

The mechanical properties of a macrolattice of SBS has been investigated (65). The sample consists of a hexagonal array of polystyrene cylinders embedded in the polybutadiene matrix. The stress-strain curves... 

A detailed study of SB diblock copolymers and diblock/homopolymer blends was conducted in the range of composition in which the polybutadiene cylindrical morphology prevails Stress-strain experiments on a series of samples revealed dramatically varying behavior from essentially brittle response to substantial and attractive levels of toughness. Figures 2a to 2d provide representative stress-strain curves for the initial morphologies shown in Figs. 3a-3d. Table 1 provides the relevant molecular level information for these blends. 

Polystyrene and polybutadiene homopolymers as well as random and block copolymers of these mers have been studied via dielectric relaxation spectroscopy and tensile stress-strain measurements. The results suggest that some block copolymer systems studied have styrene rich surfaces which appear to partially crosslink upon initial exposure to ozone even though surface oxygen concentrations are not significantly affected. After continued exposure these samples appear to then undergo chain scission. Complex plane analysis implies that after degradation... 

To gain a better understanding of the influence of fiber reinforcement on creep of RubCon, we investigated the relationship between values of compressive stresses and creep deformations that are damped out with time. The analysis of the result diagrams (Figures 2.54 and 2.55) shows linear stress-strain dependence of fiber-reinforced and plain RubCon samples at short-term compressive loading. However, creep deformations of these samples do not linearly depend on compressive stress value due to highly elastic deformation of the polybutadiene binder. 

There is experimental evidence, for many rubber-toughened polymers, that the rubber particles cavitate early in the deformation. The degree of cross-linking is kept relatively low in the polybutadiene phase of ABS to aid cavitation, and sometimes silicone oil is added for the same reason. Figure 4.12 shows both the conventional stress-strain curve and the volumetric strain versus tensile strain for rubber-modified polystyrene. When the polystyrene yields, the volume strain increases at a higher rate. Majority of the dilatational strain is due to cavitation in the rubber phase. 

The ultimate utility of any material lies in its performance. Let us examine now the types of reinforcement obtained with IPN s. Stress-strain curves for random (R) PB/PS IPN s are shown in Figure 8.22. As is well known, random cis-trans mixture) polybutadiene homopolymer is very weak, breaking at a rather low elongation. Both ultimate elongation and stress to break are increased by addition of the polystyrene network the work required to break, as measured by the area under the curves, is vastly increased. Further, the shapes of the curves are affected by the presence... 

Indeed, in the case of a biblock containing a high percentage of polybutadiene, the nodules of polystyrene are completely independent. The stress/ strain response of the material made of such a copolymer is similar to the response of polybutadiene, i.e. a non-vulcanised elastomer, which does not recover its initial length after elongation. In the case of a triblock SBS of... 

ENTMGmyENT NEIWORKS OF 1,2-POLYBUTADIENE CROSS-LINKED IN STATES OP STRAIN. W. SIMPLE EXTENSION CASE APPLICATION OF THE CKF THEORY TO STRESS STRAIN AND STRESS RELAXATION DATA... 

With a Raman instrument, measurement of these low lying bands is fairly straightforward. If the elastic Rayleigh scattering can be removed (for example the use of iodine gas filters (56) to selectively absorb the Rayleigh line), very low frequency vibrations in the range of a few cm can be observed. Based on the imit cell parameters of polyethylene, a set of Raman active lattice vibrations has been observed for polyethylene and paraffins (57). Rotatory modes are seen in traras-l,4-polybutadiene (49). With analysis of these low lying vibrations in a quantitative fashion, a correlation between molecular and macroscopic properties such as heat capacity, thermal pressure, thermal expansion, P-V-T relations, and stress-strain behavior can all be established (58). 

Most elastomers are amorphous in use. Indeed, significant crystallinity deprives the polymer of its rubbery behavior. However, some elastomers crystallize during strains such as extension. The most important of these are cis-polybutadiene, m-polyisoprene, and cK-polychloroprene. Crystallization on extension can be responsible for a rapid upturn in the stress-strain curves at high elongation see Figure 9.5. 

The strain measures for dry (unswollen) vulcanizates of a large number of natural rubbers, butadiene-styrene and butadiene-acrylonitrile copolymers, polydimethylsiloxanes, polymethylmethacrylates, polyethylacrylates and polybutadienes with different degrees of crosslinking and measured at various temperatures re confined within the shaded area in Fig. 1. These measures were determined from the stress as a function of extension at (or near) equilibrium, i.e. by applying Eq. (7). Therefore they only reproduce the equilibrium stress-strain relation for the crossllnked rubbers. In all cases the strain dependence of the tensile force (and hence of the tensile stress) was expressed in terms of the well-known Mooney-Rivlin equation, equating the equilibrium tensile stress to ... 

Stress-strain measurements on such bimodal PDMS networks exhibited upturns in modulus which were much less pronounced than those for crystallizable polymer networks such as natural rubber and cis-1,4-polybutadiene, and they are independent of temperature, as would be expected in the case of limited chain extensibility [86, 109]. For a crystallizable network, the upturns diminish and eventually disappear upon an increase in temperature [112, 114]. Similarly, swelling has relatively little... 

---