Compounding dynamical mechanical properties

Mooney Viscometer studies at 100°C and 120°C show lower viscosity of the Al-hlled gums. Lower viscosity compounds require less energy input for extrusion. Comparative results on the dynamic mechanical properties, measured using a rubber process analyzer (RPA), show that at the... 

The B-series of silica samples were also blended with rubber and the compound formulation is shown in Table 17.6. The uncured gums were then tested according to ISO 5794-2 1998. The uncured samples were tested using a Mooney viscometer and an RPA, which measures the dynamic mechanical properties as the samples cure. Figure 17.7 shows the results of these two tests for the Mooney viscosity at 100°C, storage modulus, loss modulus, and tan 8. 

A considerable amount of work has already been successfully carried out in HASETRI with naturally occurring oils as eco-friendly process oils in conventional tire recipes [31,32]. These naturally occurring oils were found to be suitable on the basis of low PCA content. Some of the naturally occurring oils showed better processing properties, polymer-filler interaction, and dispersion properties in NR-based truck tire tread cap compound and hence better mechanical and dynamic mechanical properties. As the presently available low PCA oil in the market in the form of MES TDAE and naphthenic oil are comparatively costly, these natural oils can act as the best alternative processing aids for the elastomer industry, especially in developing and underdeveloped countries. 

Pelletier, J. M. (2005) Dynamic mechanical properties in a Zr46,8Tii3.8Cui2.5NiioBe27.5 bulk metallic glass, J. Alloys Compounds, 393, 222-230. 

A summary is presented of the results of studies of the properties of silica filled compounds based on emulsion SBR prepared by blending high and low molecular weight polymers with different styrene-butadiene compositions. The mechanical and dynamic mechanical properties and extrusion characteristics were investigated and compared with those of solution SBR and conventional emulsion SBR. 

The effects of the presence of carbon black on the dynamic mechanical properties of various types of filled rubber have been reviewed by Medalia [58]. In an early work (1939), Roelig [59] found that hysteresis increases with carbon black loading. Naunton and Waring [60] and later Gehman et al. [61] found that the elastic moduli of tread compounds decrease greatly with increases in strain. Stambaugh [62] attributed the reduction in modulus, with increases in strain, to the strain per se rather than to the increase in... 

Some details of the equipment are illustrated by Fig. 16. The upper die can be raised to separate it from the lower die. A sample of uncured rubber compound can be then introduced and the upper die lowered into place as in the illustration. In this work, the dies were first heated and controlled at an elevated temperature (e.g., 90°C), then the temperature of the dies and sample can then be quite rapidly changed to a desired temperature for testing or for vulcanizing the sample. The sample can be introduced at one temperature, measurements of dynamic mechanical properties (e.g., storage shear modulus G and loss shear modulus G ) can then be made at the same temperature or at another temperature. Then, if desired the sample can be heated to a vulcanization temperature and vulcanized (with the recording of a cure curve, i.e., modulus versus time) and then the temperature can be changed and dynamic mechanical properties can then be measured again. 

Boonmahitthisud et al., prepared natural rubber/carboxylated styrene butadiene rubber (NR/XSBR) (80/20) nanocomposites containing different loadings of carbon nanotube (CNT) (0.1-0.4 phr) by a latex stage compounding method. The dynamic mechanical properties, in terms of tan 8 and E, of the neat 80/20 NR/XSBR blend and its nanocomposites were evaluated from —80 to 100 °C. Figure 21 shows the influence CNT loadings, on the tan 8 and E as a function of temperature for the nanocomposites [100]. 

Osanaiye GJ (1996) Effects of temperature and strain amplitude on dynamic mechanical properties of EPDM gum and its carbon black compounds. J Appl Polym Sci 59 567-575... 

Yu Z-Z, Yan C, Yang M S and Mai Y-W (2004) Mechanical and dynamic mechanical properties of nylon 66/montmorillonite nanocomposites fabricated by melt compounding, Polym Int 53 1093-1098. 

R. C.R., and Furtado, C.R.G. (2002) Mechanical and dynamic mechanical properties of rice husk ash—filled natural mbber compounds. J. Appl. Polym. Sci., 83, 2331-2346. 

The dynamic-mechanical properties of elastomers have been studied extensively by rubber physicists and technologists for about 50 years. The principal objective in much of this work has been to relate the experimental observations to the known composition and structure of the materials. At first sight it appears that elastomers exhibit extremely complex behaviour, having time-, temperature- and strain-history-dependent hyperelastic properties. This is because elastomers are compounded for practical use and are mixtures of a hyperelastic material (the polymer) with materials exhibiting only short-range elasticity (the filler). 

As we have seen, the nature of the filler as well as the polymer has a large influence on the dynamic-mechanical properties of elastomeric materials. The effects of other ingredients in the compound can usually be ignored, except in the final stage of property tuning. Two components, however, cannot be treated in this way plasticizers (oils) and crosslinking agents. 

The use of TESPT as a coupling agent in silica-rubber tyre tread compounds to enhance filler-matrix compatibility is studied under certain mixing conditions. This paper aims to show the effects of variations in the mixing time and temperature on the dynamic mechanical properties of silica-filled tyre tread compounds. The leaetions described lead to different results at different temperatures and the influence of the presence of zinc oxide during mixing is also taken into consideration. 33 refs. 

Purified natural rubber (PNR) is of interest because of its potentially lower toxicological effects than whole natural rubber (WNR) due particularly to the reduction in protein content. Improved dynamic mechanical properties have also been reported. Comparison of both gum and filled compounds, vulcanised using conventional cure systems (CV) and efficient vulcanisation systems (EV) prepared from PNR and WNR indicate that generally properties of the PNR are poorer than WNR. The exception is in the flex cracking resistance and the heat build up in the filled samples where PNR shows an improvement. Using the EV cure system on filled PNR gives properties almost comparable to WNR. A study of the distribution of the types of sulphur crosslink in both pNR and WNR vulcanisates indicates a more uniform distribution of monosulphidic (S), disulphidic (S2) and polysulphidic (Sx) crosslinks in the PNR samples (38.7/25/36.4 in PNR compared to 64.1/29.7/6.6 in WNR respectively). This is believed to be the reason for the better dynamic properties of PNR vulcanisates. 7 refs THAILAND... 

The use of Perkalink 900 biscitraconimidomethylbenzene (Flexsys) for increasing the reversion resistance of rubber compounds through crosslink compensation is discussed. The effects of this additive on the cure characteristics of an NR compound and on the mechanical and dynamic mechanical properties of the vulcanisates are examined. 

Optimised NR bushing compounds were developed using semi-efficient cure systems in which N-tert-butyl-2-benzothiazole was used as the primary accelerator, zinc dibutyldithiophosphate as the secondary accelerator, N-cyclohexyl thiophthalimide as retarder, andhexamethylene bisthiosulphate disodium dihydrate as a stabilising hybrid crosslinker. These cure systems gave compounds with improved stability of mechanical and dynamic mechanical properties and shortened mould cycle times. 

Most properties of linear polymers are controlled by two different factors. The chemical constitution of tire monomers detennines tire interaction strengtli between tire chains, tire interactions of tire polymer witli host molecules or witli interfaces. The monomer stmcture also detennines tire possible local confonnations of tire polymer chain. This relationship between the molecular stmcture and any interaction witli surrounding molecules is similar to tliat found for low-molecular-weight compounds. The second important parameter tliat controls polymer properties is tire molecular weight. Contrary to tire situation for low-molecular-weight compounds, it plays a fimdamental role in polymer behaviour. It detennines tire slow-mode dynamics and tire viscosity of polymers in solutions and in tire melt. These properties are of utmost importance in polymer rheology and condition tlieir processability. The mechanical properties, solubility and miscibility of different polymers also depend on tlieir molecular weights. 

Table 11.14 gives critical stress, critical strain, and critical stored energy of NR-EPDM blends for initiation of ozone cracking. All the properties show an increase on addition of TOR, especially the critical stored energy. Stored energy is a strong indicator of ozone resistance and shows an increase by about 80% on addition of 20 parts of TOR to the compound. This was confirmed by SEM pictures of surface ozone cracks and the results of dynamic mechanical moduli and tan d measurement. 

The dump temperature of the compound was varied by changing the mixer s rotor speed and fill factor while keeping the other mixing conditions and the mixing time constant. Under the assumption that the final dump temperature is the main parameter influencing the degree of the sUanization reaction, the effect of the presence of ZnO on the dynamic and mechanical properties of the compound was investigated. ZnO was either added on the two-roll mill or in the mixer. 

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