Rubber fully cured

The applications of rubber as an engineering material almost invariably involve bonding to a rigid substrate or reinforcement. In some instances these bonds need to be established to a fully cured thermoset rubber or a molded thermoplastic rubber, and a wide variety of adhesives suitable for this purpose are available. In... 

On the other hand, silicones are used in organic composites. The application of alloys composed of the fully cured silicone rubber particles in a continuous thermoplastic phase, called thermoplastic silicone vulcanizate, which offers high-performance materials, has been reported.506,507 Functionalized POSS was not only co-polymerized, but also blended with poly(methylmethacrylate) to study the effect of silsesquioxanes on the thermal stability of thermoplastics.508... 

Figure 8.7 SEM photograph of a fully cured rubber-modified epoxy network. The rubber CTBN (26 wt% AN) is first pre-reacted with a large excess of diglycidyl ether of bisphenol A (DGEBA) to obtain an epoxy-terminated rubber. Then an equivalent of 15 wt% initial CTBN is introduced in DGEBA-4,4 -diamino diphenyl sulfone, DDS, system precured at 135°C (time > tgei) and then postcured at 230°C. Rubber-rich particles are spherical, D 2.8 0.5 gm, and well dispersed. (From LMM Library.)...

Another disadvantage of RIPS is that, usually, part of the modifier remains dissolved in the thermoset matrix, even at full conversion. If the modifier is a low-Tg rubber, this leads to a decrease of the Tg of the fully cured material and losses in thermal and load-bearing properties. 

FIGURE 3.11 Rheometer ta-que normalized by the fully cured plateau value versus the gel content during sulfur vulcanization of three rubbers (Zhang et al., 2010). 

The Epons 828,1001,1002,1004, and 1007 fully cured with stoichiometeric amounts of DDS are examples of well-characterized networks. Therefore, mechanical measurements on them offer insight into the viscoelastic properties of rubber networks. The shear creep compliance J t) of these Epons were measured above their glass temperatures [11, 12, 14]. From the statistical theory of rubber elasticity [1-5, 29-33] the equilibrium modulus Ge is proportional to the product Tp, where p is the density at temperature T, and hence the equilibrium compliance is proportional to (Tpy Thus J t) is expected to be proportional to and J(t)Tp is the quantity which should be compared at different temperatures. Actually the reduced creep compliance... 

Rubber-based products permeate our lives, forming part of the many materials used for personal, domestic and industrial purposes. Rubber may be natural, synthetic or a mixture of the two. Since the vast majority of rubberized materials are unlabeled, it is difficult to determine whether a product contains natural or synthetic rubber. The overlap between rubber and plastic further complicates the matter, especially since plastics contain many of the same catalysts, stabilizers, antioxidants and pig-ments/dyes that are present in rubber products. Fregert (1981) listed a number of naphthylamines, substituted para-phenylenediamines, alkylphenols and hydroquinone derivatives, which are utilized in the manufacturing of both rubber and plastic. Although completely cured plastics are rare sensitizers, fully cured rubber products produce allergic reactions as the sensitizers in rubber can leach out or bloom over time. 

Comparing the properties of TPO-0 and TPO-V of the same constituents at the same hardness, the benefits given by the fully cured rubber in TPO-V become clear (improved set properties, fluid and chemical resistance, service temperature and tensile strength). These are achieved, however, at the cost of some other properties (e.g. reduced melt flow, tear... 

The mechanism of adhesion of fully cured rubbers may be different from that of imcured rubbers. The contribution from interdiffusion will be less significant. However, the application of the compound solution and the compound strip may provide some interdiffusion. The contribution to adhesion may arise principally from factors of interfacial surface energy and rubber hysteresis (the percentage energy loss for cycle of deformation). Bonding arises from several kinds of interactions that may be physical/or chemical in nature. 

For fixing an EPDM rubber seal to a polyvinyl chloride (PVC) beer pump mechanism the cyanoacrylate must not only produce a reliable bond but also be approved for use with potable water. The cyanoacrylate, once fully cured, is essentially an inert plastic and many grades are approved for potable water as well as for medical applications (see Section 10.11.4). 

Examples in industry include attaching a silicone rubber seal to an aluminium parachute container. A primer is brushed on to the silicone rubber and the cyanoacrylate is applied to the aluminium. Once fully cured the bonded seal assembly prevents dust or moisture entering the safety critical box. 

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