Rubber state

Deformation of a polymer in the rubber state—of importance in vacuum forming, pressure forming and warm forging techniques. 

Viscoelastic and transport properties of polymers in the liquid (solution, melt) or liquid-like (rubber) state determine their processing and application to a large extent and are of basic physical interest [1-3]. An understanding of these dynamic properties at a molecular level, therefore, is of great importance. However, this understanding is complicated by the facts that different motional processes may occur on different length scales and that the dynamics are governed by universal chain properties as well as by the special chemical structure of the monomer units [4, 5],... 

While in the temperature range called the rubbery plateau, the soft polymer responds instantaneously and reversibly to applied stress and tends to be Hookean. In the rubber state, the polymer approaches Hooke s law for... 

Fig. 18 TEM-micrograph of carbon black aggregates (N339) prepared from ready mixed S-SBR-composites with 60 phr filler (in-rubber state)...

Fig. 19 a Fractal analysis according to Eq. (11) of primary carbon black aggregates (N339) prepared from S-SBR-composites with 60 phr filler (in-rubber state). Vp is evaluated from Eq. (12). b Fractal analysis according to Eq. (11) of the same set of primary carbon black aggregates (N339) as shown in Fig. 19a. Np is evaluated by using Eq. (13)...

Fig. 21 Aggregate size distribution obtained from TEM-analysis (in-rubber state) of E-SBR-samples filled with 50 phr N330 at various mixing times, as indicated [115]...

Because of its elastic texture and tendency to harden, marshmallow was assumed to exist in a rubber state. Molecules in the rubbery state of marshmallow can be mobile and lead to sugar crystallization, loss of moisture from the matrix, cross-linking of proteins in gelatin, and collapse of foam. In order to stabilize the product, it is necessary to identify the factors limiting the shelf life of the marshmallow under a specific storage condition. 

As already mentioned earher (see Section 7.1.1), because of its high glass-transition temperature, that is, T = 208°C, PPO has to be melt-processed at elevated temperatures. As a result, degradation of the polymer may occur at such temperatures (particularly through oxidation reactions at the methyl substituents), furthermore, upon cooling from the liquid to the rubber state, two unwanted events can take place (i) the polymer crystallizes and (ii) the molecular motions are frozen and the rubbery polymer turns to a glass. As a consequence, the material becomes brittle and cannot be used for practical applications. Fortunately, PPO exhibits unusual and remarkable blending properties [36]. 

Resolved Spectrum S2 Polymer Phase 2, Rubber State (Amorphous)... 

Ebonite stocks may be prepared for vulcanization by calendering or extrusion. Vulcanization, as with soft rubber, is affected by heat and pressure. In some cases the rubber may be given a soft cure, formed into a desired shape, and then cured to the final hard rubber state. 

POLYMER SCIENCE ASPECTS POLYMERS IN THE RUBBER STATE... 

Polymeric sheet is heated to its rubber state by either mechanical or pneumatic means. The sheet is formed into a three-dimensional part. The complete thermoforming process (Figure 10.1) may be described in terms of the following sequences of phases ... 

The respective kinetics correlates with and can be predicted from the glass transition temperature of the carrier materials. Plasticization by water absorption under conditions of high humidity may cause reduction of the glass transition temperature below room temperature. Then, the structural change in the wall material leads to collapse of the food powder, resulting in flavor release from the rubber state of the carrier matrices (Ubbink and Schoonman, 2003). 

The viscoelastic state is also known as the rubber state. A piece of rubber under external force can be stretched. When the external force stops, the rubber recovers to its original position. Usually long-chain polymers can be induced to exhibit typical rubberlike behavior, for example, chains such as polyesters, polyamides, elastic sulfur (sulfur cooled from the liquid), and cellulose derivatives. 

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