Vulcanized properties

Processing Aids. Petroleum oils are processing aids as well as softeners/extenders/plasticizers. This section concentrates on those materials which serve mainly as processing aids without a large contribution to vulcanized properties. They are most often used at much lower levels. 

These polymers are very sensitive to mastication. Mastication decreases the solution viscosity and increases the ease of solution. Because the reactive sulphur linkages, rapid vulcanizing properties are obtained. On the other hand, the presence of thiuram disulphide improves the resistance of CR to dehydrochlorination. 

The introduction of halogenated monomers into the backbone results in highly increased vulcanization properties. 

Chloro-4,6-bis(methylsulfanyl)-l,3,5-triazine (15) on reaction with disodium tetrasulfide forms a bidentate bistriazine molecule 16 which is linked by a sulfane chain.103 This type of compound exhibits excellent rubber-vulcanization properties. 

Properties. Typical raw polymer and vulcanized properties of synthetic IR are similar to those of NR. Both exhibit good inherent tack, high compounded gum tensile strength (green strength), and good vulcanizate hysteresis (low values) and tensile properties. In synthetic IR, there is minimal variance in physical properties lot to lot, and there is a low concentration of nonrubber constituents compared to natural rubber. 

Styrenic TPEs have strength properties equal to vulcanized rubber, but they do not require vulcanization. Properties are determined by polymer type and formulation. There is a wide latitude in compounding to meet a wide variety of application properties. According to application-driven formulations, Kratons are compounded with a hardness range from Shore A 28 to 95 (Shore A 95 is approximately equal to Shore D 40), sp gr from 0.90 to 1.18, tensile strengths from 150 to 5000 Ib/in (1.03 to 34.4 MPa), and flexibility down to 112°F (-80 C) (see Table 3.1).2... 

The sulfur vulcanization properties of guasuile rubber reflect the low level of reactive substituents. Because of natural vulcanization activators not present in guayule rubber, Hevea rubber has a higher cure rate and attains a higher level of cross-linking (111,112). However, adjusting the cure system can reduce these performance differences (112). 

The vulcanized properties of a number of tread rubber candidates including the block copolymers, compounded in a HAF tread compound are shown in Table 1. 

For the purpose of studying of influence of structural parameters of NR samples processed in various temperature time intervals on properties of rubber compounds and rubbers on their basis, within the standard filled compounding for NR [5] rubber mixes were made and their vulcanizing properties and physicomechanical properties of vul-canizers were defined. Results of the conducted researches are given in Table 10.2. 

TABLE 10.2 Influence of Duration of Treatment SVR 3L on Rubber Compounds Vulcanizing Properties and Physicomechanical Properties of Vulcanizers... 

Additional alkyl-substituted poly butadienes are listed in Table 13. Parallel to an increase in the alkyl substituents volume and electron donor properties, there is a decrease in selectivity and activity for cis-, A insertions, although the vulcanizing properties of the products are improved [338-345]. 

The gum vulcanization properties of the TMO-AGE copolymer (Table VI) are low. These data are further evidence that the excellent tensile properties observed for the black-filled TM)-AGE vulcanizates is not due to crystallinity or crystallizability. The 91% gel result does support our conclusion that the TMO-AGE copolymer is reasonably uniform. 

Polymerization of ethylene and propylene results in a saturated copolymer. In order to vulcanize this rubber, some unsaturation has to be introduced. This is commonly done by adding a few percent of non-conjugated diene (termonomer) such as dicyclopentadiene, 1,4-hexadiene, or ethylidene norborene during the polymerization. Since only one of the double bonds of the diene reacts during polymerization, the other is free for vulcanization. The amount of unsaturation left in the ethylene propylene diene terpolymer is of great interest because the vulcanization properties will be affected. 

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