Mechanical Properties of Elastomers

We first examined the dynamic mechanical properties of various elastomers which are commonly used for PSA applications. The dynamic mechanical properties of these elastomers were characterized using the parallel-plate mode of the Rheometrics dynamic spectrometer (RDS). The measurement of dynamic mechanical properties was carried out on bulk or dried latex samples. Caution should be taken during the drying step to avoid crosslinking or degradation. All the temperature scan data of rubber-resin blends in this paper were measured at 10 rad/sec with less than 2% strain. 

---

The dynamic mechanical properties of elastomers have been extensively studied since the mid-1940s by rubber physicists [1], Elastomers appear to exhibit extremely complex behavior, having time-temperature- and strain-history-dependent hyperelastic properties [1]. As in polymer cures, DMA can estimate the point of critical entanglement or the gel point. 

Improvement of the mechanical properties of elastomers is usually reached by their reinforcement with fillers. Traditionally, carbon black, silica, metal oxides, some salts and rigid polymers are used. The elastic modulus, tensile strength, and swelling resistence are well increased by such reinforcement. A new approach is based on block copolymerization yielding thermoelastoplastics, i.e. block copolymers with soft (rubbery) and hard (plastic) blocks. The mutual feature of filled rubbers and the thermoelastoplastics is their heterogeneous structure u0). 

Chartoff, R. P. Drake, M. L. Salyer, I. 0. Proceedings of the Symposium on Dynamic Mechanical Properties of Elastomers. Naval Underwater Systems Center, July 1984, New London, CT. 

Tensile strength is an important mechanical property of elastomer. Five kinds of EPDM in the experiment kept the higher tensile strength at lOMGy than initial values showing the durability of the samples for irradiation. 

A peroxide-induced reactive compounding of PP/GRT blends in a corotating twin-screw extruder was carried out to prepare thermoplastic elastomer alloys (Wiessner et al., 2012). The extrusion experiments showed that the width of the residence time distribution was the key parameter determining the mechanical properties of elastomer alloys, whereas the mean residence time had little effect. This was confirmed by performing both quasi-static and cyclic tensile tests. 

Dong, J., Liu, Z., and Zheng, C. 2006. Preparation, morphology, and mechanical properties of elastomers based on co-dihydroxy-polydimethylsiloxane/ poly(methyl methacrylate) blends. Journal of Applied Polymer Science 100(2) 1547-1553. 

Rei Reincke, K., Friedel, J., Grellmann, W. Influence of process oils on the mechanical properties of elastomers. Kautschuk Gummi Kunstst. 62 (2009) 506-514. 

Stevenson, A. (1995) Effect of crystallization on the mechanical properties of elastomers under large deformation, in Current Research in the Thermo-Mechanics of Polymers in the Rubbery-Glassy Range, ASME. 

Polymers, unlike metals, find wide application as completely amorphous solids. The two amorphous forms of greatest interest are the glasses and the elastomers or rubbers. Polymers found their earliest technical application as elastomers over 100 years ago, and it is in this form that they make a unique contribution to society. In examining the structure of the amorphous state we shall confine attention to the really significant point, which is the conformation of the molecule. It will be shown that the conformation resembles that of the molecule in dilute solution sketched at the end of the previous chapter. By means of a simple model a mathematical description of the conformation will be obtained which has fundamental and practical consequences for the mechanical properties of elastomers, the stress-strain curve in particular. 

Addition of fillers can dramatically change mechanical properties of elastomer materials. For example, a pure gum vulcanizate of general purpose styrene-butadiene rubber (SBR) has a tensile strength of no more then 2.2 MPa but, by mixing in 50 parts per hundred weight parts of rubber (p.p.h.r) of a active CB, this value rises more than 10 times to 25 MPa. How CB, being fine powder of practically no mechanical strength, can make reinforcement in rubbers, similar to... 

Plavsic, M., Pajic-Lijakovic, I., Cubric, B., Popovic, R.S., Bugarski, B., Cvetkovic, M., and Lazic, N., Chain conformational statistics and mechanical properties of elastomer composites. Mater. Sci. Forum, 453-454, 485-490, 2004. 

Plavsic, M.B., Pajic-Lijakovic, I., Putanov, P., Chain Conformational Statistics and Mechanical Properties of Elastomer Blends, in New Polymeric Materials, MacKnight, W.J., Martuscelli E., Korugic-Karasz Lj., Eds., American Chemical Society Washington, in press. 

Elastomers such as natural rubber (NR) are of great importance in manufacturing industries. However, they possess properties which are less than that required for practical applications. This has led to the use of fillers for reinforcement of their properties. For practical applications, the physical and mechanical properties of elastomers are reinforced with mineral fillers such as silica, CB, clay fibre, short fibre and layered silicate. ... 

Dong, J. Zhang, N. Liu, Z., Preparation, Morphology, and Mechanical Properties of Elastomers Based on Polydimethylsiloxane/Polystyrene Blends. J. Appl. Polym. Sci. 2009,112,985-990. 

The majority of studies of mechanical properties of elastomers have heen carried out in elongation because of the simplicity of this type of deformation. 121-123 Results are typically expressed in terms of the nominal or engineering stress f = f/A, which, in the simplest molecular theories, is given by... 

Termonia, Y., Mechanical Model for the Mechanical Properties of Elastomers. 2. Synergistic Effects in Bimodal Cross-Linked Networks. Macromolecules 1990, 23,1481-1483. 

MRE composites were prepared according to the commonly used methods. It was found that micro- and nano- sized iron oxides and carbonyl iron powder were active fillers improving mechanical properties of elastomers. Additionally, they... 

FIGURE 12.6 Mechanical properties of elastomer composites based on NBR and SBR filled with (a-b) silica, (c-d) wollastonite, (e-f) kaolin TS - tensile strength, Eb -elongation at break. 

Elastomers have recently received considerable attention in the development of controlled drug-dehvery systems because they offer several advantages when compared to conventional fabricated materials [54]. Most importantly, the mechanical properties of elastomers can be manipulated to make them as soft as body tissues. Moreover, elastomers can recover and withstand mechanical challenges following implantation in a mobile part of the body. Elastomers have also been demonstrated to be effective as biomaterials for protein drug delivery. 

So far, we have discussed the dynamic mechanical properties of elastomers which are used for making pressure-sensitive adhesives. In the following sections, we shall discuss the dynamic mechanical properties of tackifying resins and pressure-sensitive adhesives. 

So far we have discussed the dynamic mechanical properties of elastomers and tackifying resins separately. We have also examined the dynamic mechanical properties of the commercial tape and label adhesives and defined their requirements for good pressure-sensitive adhesives. We will explain how to obtain PSA with the specific requirements in T, G (co), and G"(w) values from the nontacky elastomer and glassy tackifying resin. First, the simple two-component formulations will be examined for various elastomeric systems. 

The mechanical properties of elastomers prepared from natural products such as castor oil are generally inferior to those produced from synthetic polyols used commercially. They have been used for soft printers rollers and for preparing semi-rigid cellular materials but are not known to be of current importance. 

The typical pot life of many two-component polyurethane elastomer resins is a few minutes and the initial viscosity is in the vicinity of 20,000 cps at 20°C. Obviously, drops of such resin types cannot be used with narrow glass applicators or the knotting method. Typical viscosities of epoxy resins are in the range between 500 and 1000 cps and pot lives between 15 and 60 min. In order to determine the adhesion of elastomer resins, it was necessary to develop a new method. A further aim was to investigate the influence of the characteristics of the fiber surface on the mechanical properties of elastomer composites. 

The great majority of studies of mechanical properties of elastomers involved elongation, because of the simplicity of this type of deformation [9]. The apparatus typically used to measure the force required to give a specified elongation of a rubber-like material is indeed very simple, as can be seen from its schematic description in Fig. 1.10 [3]. The elastomeric strip is mounted between two clamps, the lower one fixed and the upper one attached to a movable force gauge. A recorder is used to monitor the output of the gauge as a function of time in order to obtain equilibrium values of the force suitable for comparisons with theory. The sample is... 

Termonia Y (1990) Molecular model for the mechanical properties of elastomers. 3. networks cross-linked in a state of strain. Macromolecules 23(7) 1976-1979... 

Lu YL, Liu L, Tian M, Geng HP, Zhang LQ (2005) Study on mechanical properties of elastomers reinforced by zinc dimethacrylate. Eur Polym J 41(3) 589-598... 

Kautchuk und Gummi Kunststoffe 50, No.4, April 1997, p.299-303 MECHANICAL PROPERTIES OF ELASTOMER COMPOUNDS IN SYNCHRONOUS AND V-RIBBED BELTS... 

Additives are utilized to extend service life and improve performance of oils in the engine room. These additives can reduce mechanical properties of elastomers and cause surface hardening [697]. The type of additive depends on the type of oil used. Table 5.105 compares the behavior of HNBR, NBR, and CPE exposed to ASTM oil no. 2 with various additive contents [796]. 

---