C for Polymers and Rubbers

TABLE 10.5 Gas Permeability Constants (10 P) at 25°C for Polymers and Rubbers The gas permeability constant P is defined as... 

Palmas, P., Le Campion, L., Bourgeoisat, C. Martel, L. (2001) Polymer, 42, 7675-7683. Paterson, A. (1984) Proceedings of Radiation Processing for Plastics and Rubbers, London London Plastics and Rubber Institute. 

Figure 15.5 Effect of level of merci tan modifier upon (a) the gel content and (b) the plasticity of polymer obtained after 12 h reaction at SO°C, for styrene-butadiene rubber produced by emulsion pcdymraizafion (Bebb et al. [17]). Reaction foimulatitHi (parts mass) sonene 25, buta ne 75, water 180, soq> 5, potassium posulphaie OJ, dodecyl mercaptan variable (see abscissae of plots)...

Lykke et al. [177,262] have used L MS (ToF-MS, FTMS) in resonant and non-resonant mode for the molecular analysis of complex materials, including polymer/additive systems. Different wavelengths for the post-ionisation step (near-UV, far-UV, VUV) permit selectivity that provides important additional information on the chemical constitution of these complex materials. LDI techniques render more accessible analysis of complex materials such as polymers and rubbers containing a wide variety of additives and pigments. Lykke et al [218] also compared laser desorption, laser desorption/post-ionisation and laser ionisation in both direct and extract analysis of three vulcanised rubbers (natural rubber, SBR and poly(c/5 -butadiene)). Desorption (532, 308, 266 nm)/post-ionisation (355, 308, 266, 248, 213, 118 nm) was carried out with various lasers. Desorption (308 nm)/post-ionisation (355 nm) with REMPI detection allows preferential detection of various additives (antiozonant HPPD, m/z 268, 211, 183, 169 antioxidant poly-TMDQ, m/z 346, 311) over the ubiquitous hydrocarbons in a rubber (Fig. 3.13). 

The dispersed-phase stability of the organomontmorillonite [62] was not compromised. The weight percent of quat on the montmorillonite was evaluated at 0.1, 0.15, 0.2, and 0.3%. This quat will participate with the cure chemistry during vulcanization. The aqueous SBR latex (22.4% solids supplied by Jilin Petrochemical Co. Ltd.) was blended with the organomontmorillonite aqueous dispersion. The polymer-functional montmorillonite dispersion was flocculated with 2% sulfuric acid, washed with water, and dried in an oven at 50 °C for 20h. The rubber crumb was formulated at 10 phr montmorillonite content. The rubber was compounded with a two-roll mill and cured at 150°C. The compound ingredients appear to be standard with standard concentrations. 

Polymers are seriously subject to oxygen attack. This limits their upper operating performance temperature. For elastomers these temperatures are quite low, being around 100 °C for natural rubber, 120 to 130 °C for polybutadiene and its copolymers as well as polychloroprene. EPDM at 200 °C is somewhat more stable. 

Figure 6. Constant stress creep/creep recovery curves at 35 C for neat, polymer and rubber modified paving grade AC10-3 binders. Reference material Novaphalt AGIO.

An unusual method for the preparation of syndiotactic polybutadiene was reported by The Goodyear Tire Rubber Co. (43) a preformed cobalt-type catalyst prepared under anhydrous conditions was found to polymerize 1,3-butadiene in an emulsion-type recipe to give syndiotactic polybutadienes of various melting points (120—190°C). These polymers were characterized by infrared spectroscopy and nuclear magnetic resonance (44—46). Both the Ube Industries catalyst mentioned previously and the Goodyear catalyst were further modified to control the molecular weight and melting point of syndio-polybutadiene by the addition of various modifiers such as alcohols, nitriles, aldehydes, ketones, ethers, and cyano compounds. 

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. 

Jha and Bhowmick [51] have reported the development and properties of thermoplastic elastomeric blends from poly(ethylene terephthalate) and ACM by solution-blending technique. For the preparation of the blend the two components, i.e., poly(ethylene terephthalate) and ACM, were dried first in vacuum oven. The ACM was dissolved in nitrobenzene solvent at room temperature with occasional stirring for about three days to obtain homogeneous solution. PET was dissolved in nitrobenzene at 160°C for 30 min and the rubber solution was then added to it with constant stirring. The mixture was stirred continuously at 160°C for about 30 min. The blend was then drip precipitated from cold petroleum ether with stirring. The ratio of the petroleum ether/nitrobenzene was kept at 7 1. The precipitated polymer was then filtered, washed with petroleum ether to remove nitrobenzene, and then dried at 100°C in vacuum. 

FIGURE 11.23 Advancement of the cure reactions for different base epoxy and rubber-epoxy systems. (From Dispenza, C., Carter, J.T., McGrail, P.T., and Spadaro, G., Polym. Eng. Sci., 41, 1483, 2001.)... 

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