Polybutadiene-based polyurethane

Figure 18 Polyimide 9 and the pyreny 1-end-capped, polybutadiene-based polyurethane 11. ...

The CL analysis applied on the degradation of hydroxyl-terminated polybutadiene based polyurethane elastomers illustrates the effect of previous energetic treatment to which samples were subjected. The increase in the initial CL intensity and the shift of maximum CL intensity upon the shorter time are the effects of the initiation of oxidation by molecular scissions and, respectively, the reactions of free radicals with oxygen that leads to decrease in the material durability (Fig. 61) [06C1]. Another proof for the beginning of degradation by prior processing is the increased CL-emission at the start of the CL measurements. (Fig. 62). 

Fig. 61 CL dependencies on testing time recorded on aged hydroxyl-terminated polybutadiene based polyurethane elastomer. Testing temperature 120 °C. The data were taken from [06C1]. (1) pristine sample, (2) weathered sample for 105 days, (3) weathered sample for 140 days.

Hydrolytic stability of polyurethanes depends on the composition and concentration of the weakest groups. Polyesterurethanes have considerably lower resistance to hydrolysis than polyether or polybutadiene based polyurethanes. Hydrolysis of ester groups is catalyzed by acid groups formed as the product of hydrolysis. Therefore, an efficient way of slowing down the process is to block the acid formed, which is usually carried out by adding carbodiimides. Such solutions are temporary since after the consumption of all carbodiimide the process accelerates again. 

Jia D, Chen L, Wu B, Wang M (1989) Interpenetrating polymer networks based on polybutadiene-based polyurethane. In Klempner D, Frisch K (eds) Advances in interpenetrating polymer networks, vol 1. Technomic, Lancaster, PA, p 303 Lee BK, Kim SC (1995) Polym Adv Technol 14 402... 

Military propellants are based on relatively powerful oxidisers and fuels of high calorihc value in order to develop an improved thrust or impulse. Thus the most commonly-used oxidisers are potassium perchlorate, ammonium perchlorate or more esoteric compounds such as hydrazinium nitroformate. Metallic fuels include aluminium, magnesium and beryllium, while binders are mainly hydrocarbons such as polybutadiene, polyisobutylene, polyurethane or poly(vinyl chloride) (PVC) as presented in Table 3.2. 

These are typically represented by the chemical structure shown in Fig. 12.1. This structure has superior water-resistant properties to that of the conventional polyols used in polyurethane synthesis and it successfully competes with both them and room temperature vulcanizing (RTV) silicones on this basis, especially as the principal application market is the encapsulation of electronic components. Epoxy resins, widely used for encapsulation, change their mechanical properties widely with temperature and hydroxy-terminated polybutadiene-based urethanes are superior in this respect. 

The minimum service temperature is determined primarily by the Tg of the soft phase component. Thus the SBS materials ctm be used down towards the Tg of the polybutadiene phase, approaching -100°C. Where polyethers have been used as the soft phase in polyurethane, polyamide or polyester, the soft phase Tg is about -60°C, whilst the polyester polyurethanes will typically be limited to a minimum temperature of about 0°C. The thermoplastic polyolefin rubbers, using ethylene-propylene materials for the soft phase, have similar minimum temperatures to the polyether-based polymers. Such minimum temperatures can also be affected by the presence of plasticisers, including mineral oils, and by resins if these become incorporated into the soft phase. It should, perhaps, be added that if the polymer component of the soft phase was crystallisable, then the higher would also affect the minimum service temperature, this depending on the level of crystallinity. 

Elastomers from Myrcene-Based Polyols. A series of polyurethanes was formed using a PM polyol in admixture with various amounts of 1,4-butanediol (BD) and reacted with MDI (>/). For comparison, a corresponding series of elastomers based on a commercially available polybutadiene (PB) polyol (Arco R45-HT, Cornelius Chemical Company) was also prepared. Characterization data of the PB and PM polyols are given in Table III. 

Figure 1. Dynamic relaxation spectra (torsion pendulum, 1 Hz) of polyurethanes based on polymyrcene and polybutadiene polyols. Typical relaxation peaks are shown at the temperatures designated T/j, T and. ...

Polyurethane (PU) PV membranes were reported by Schauer et al. (1999). PU membranes were prepared by the reaction of toluene-2,4-diisocyanate with hydroxyl-terminated oligomers. Oligomers were either liquid polybutadiene (PB) (MW 3000) or propylene oxide-based PEs (MW 420 and 4800). The prepared membranes were used in PV of binary mixtures of water-EtOH, water-dioxane, and EtOH-toluene, respectively. Membranes obtained from the polymer quatemized poly[3-(N, N -dimethyl)aminopropylamide-co-acrylonitriles] showed selective separation of water from aqueous EtOH solution by PV (Yoshikawa et al. 1991). The separation factor toward water reached over 15,000. Membrane performance showed a good correlation to membrane polarity. DSC melting endotherms of the water-swoUen membranes were studied to clarify the state of water in the membrane. The resnlts suggested that there were two states of water in the membrane bound and free. The higher the fraction of bound water in the membrane, clearly, the more preferentially was water permeated. 

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