Rubbers chemical constitution

At present a disperse material wide list is known, which is able to strengthen elastomeric polymer materials [5]. These materials are very diverse on their surface chemical constitution, but the small size of particles is a common feature for them. Based on the observation the hypothesis was offered that any solid material would strengthen the rubber at the condition, which it was in a very-dispersed state and could be dispersed in polymer matrix. Edwards [5] points out that filler particles small size is necessary and, probably, the main requirement for reinforcement effect realization in rubbers. Using modem terminology, the nanofiller particles, for which their aggregation process is suppressed as far as possible, would be the most effective ones for mbbers reinforcement [3, 12]. Therefore,... 

By this time there was considerable understanding of the chemical constitution of polymers following the work of Hermann Staudinger, who as a consultant to BASF around 1910 studied isoprene, the building block of rubber. His interest in the constitution of the natural product led him on a path that in May 1922 culminated in the... 

At present a disperse material wide list is known, which is able to strengthen elastomeric polymer materials [5], These materials are very diverse on their surface chemical constitution, but particles small size is a common feature for them. On the basis of this observation the hypothesis was offered, that any solid material would strengthen the rubber at the... 

Albert, A., Rubber, S., Goldacre, R. Balfour, B. (1947). The influence of chemical constitution on antibacterial activity. Part III. A study of 8-hydroxy-quinoline (oxine) and related conipounds. Brit. J. Exp. Pathol., 28, 69-87. 

Text of the Sixth Institution of the Rubber Industry Foundation Lecture entitled The Chemical Constitution of the Rubber Molecule .)... 

Many references to detailed work which led to the elucidation of the chemical constitution of the natural rubber molecule are to be found in the three works cited in the bibliography to the previous chapter. The references given below are confined to more recent contributions. 

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). 

Today, more and more know how is available to design a cure system capable of meeting these demanding requirements. New developments in materials allow compounders to reformulate a cure system capable of providing improved performance. Antireversion chemicals constitute a class of such materials, and can improve service performance. Health and safety issues, for example the concerns about the possible carcinogenicity of N-nitrosamines, have also lead to the introduction of new rubber additives. 

The changes, however, are both numerous and significant. First of all, there is a change in the organization of the subject matter. For example, material formerly contained in the section entitled Analytical Chemistry is now grouped by operational categories spectroscopy electrolytes, electromotive force, and chemical equilibrium and practical laboratory information. Polymers, rubbers, fats, oils, and waxes constitute a large independent section. 

Plasticizers can be classified according to their chemical nature. The most important classes of plasticizers used in rubber adhesives are phthalates, polymeric plasticizers, and esters. The group phthalate plasticizers constitutes the biggest and most widely used plasticizers. The linear alkyl phthalates impart improved low-temperature performance and have reduced volatility. Most of the polymeric plasticizers are saturated polyesters obtained by reaction of a diol with a dicarboxylic acid. The most common diols are propanediol, 1,3- and 1,4-butanediol, and 1,6-hexanediol. Adipic, phthalic and sebacic acids are common carboxylic acids used in the manufacture of polymeric plasticizers. Some poly-hydroxybutyrates are used in rubber adhesive formulations. Both the molecular weight and the chemical nature determine the performance of the polymeric plasticizers. Increasing the molecular weight reduces the volatility of the plasticizer but reduces the plasticizing efficiency and low-temperature properties. Typical esters used as plasticizers are n-butyl acetate and cellulose acetobutyrate. 

Polymer science dates from the recognition that polymers - such as rubber, cellulose, polystyrene, to name a few - consist of the very large molecules that we call macromolecules. More specifically, they consist of long chains of atoms linked by chemical bonds. The number of atoms in these chains usually runs into the thousands. This rudimentary, but fundamental, conception of the molecular constitution of polymeric substances is the cornerstone of modern polymer science. Without it, a science of polymers could not have been founded and elaborated. [3]... 

Note Olefinic (isoprenoid) hydrocarbons are produced by a number of plants, notably Hevea brazi-lietisis (rubber), guayule, and various members of the Euphorbiaceae family. Current research on the latter group indicates that they could be used as a source of liquid fuels and chemical feedstocks by genetic modification of the plants and control of then molecular constitution. It is estimated that oil obtained by large-scale cultivation of such plants, which grow well in semi-arid environments, could become economically competitive with petroleum within a few years. 

The polyallomers constitute the class of block copolymers where both components are capable of crystallizing independently (Coover et al, 1966 Hagenmeyer and Edwards, 1966, 1970 Eastman Chemical Products, n.d.). The most important member of this family contains crystalline, stereoregular polypropylene as the major component and polyethylene as the minor component. As expected for a block copolymer, these products differ greatly in behavior from mechanical blends of polyethylene and polypropylene, and also from their random copolymers, poly(propylene-co-ethylene). When crosslinked with a diene monomer, the latter copolymers are known as EPDM rubbers (Lee et a/., 1966 Rodriguez, 1970, Chapter 13), while the former blends are of apparently little interest. In Figure 6.28 and 6.29 the... 

Both the modulus-temperature relationships presented in the preceding sections and the tensile data presented above are strikingly similar to those demonstrated for other rubber-plastic combinations, such as the thermoplastic elastomers (see Chapter 4 and the model system presented in Section 10.13) and the impact-resistant plastics (Chapter 3). The IPN s constitute another example of the simple requirement of needing only a hard or plastic phase sufficiently finely dispersed in an elastomer to yield significant reinforcement. Direct covalent chemical bonds between the phases are few in number in both the model system (Section 10.13) and present IPN materials. Also, as indicated in Chapter 10, finely divided carbon black and silicas greatly toughen elastomers, sometimes without the development of many covalent bonds between the polymer and the filler. 

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