Rubber like polymers, traditional

Rubber-like materials now superseding the traditional mastics and putties used in the building industry. Such sealants (also termed mastics) are based on butyl rubber, liquid polysulphides, silicone rubbers, polybutylene, nitrile rubbers and plasticised vinyl polymers. SEBS... 

Urethanes are processed as rubber-like elastomers, cast systems, or thermoplastic elastomers. The elastomer form is mixed and processed on conventional mbber mills and internal mixers, and can be compression, transfer, or injection molded. The liquid prepolymers are cast using automatic metered casting machines, and the thermoplastic pellets are processed like all thermoplastic materials on traditional plastic equipment. The unique property of the urethanes is ultrahigh abrasion resistance in moderately high Shore A (75—95) durometers. In addition, tear, tensile, and resistance to many oils is very high. The main deficiencies of the urethanes are their resistance to heat over 100°C and that shear and sliding abrasion tend to make the polymers soft and gummy. 

It has been noted in several places (Sections 4.6,17.1, and 17.5) that certain thermoplastic polymers can be quite elastic (rubbery) at room temperature. They form a distinct class of materials, the thermoplastic elastomers (TPEs), which have been defined (ASTM D1566) as a family of rubber-like materials that, unlike conventional vulcanized rubber, can be processed and recycled like thermoplastic materials. The typical structure of these materials is the coexistence of soft domains that give rubbery behavior with hard domains that act as heat-labile cross-Unks. Although the thermoplastic elastomers compete in many of the applications traditionally assigned to conventional rubbers, the sensitivity of the cross-links to heat makes them unsuitable for an application such as automobile tires, where the... 

Nitrile and Acrylic Rubber. Nitrile rubbers are made by the emulsion copolymerization of acrylonitrile (9-50%) and butadiene (21) and are abbreviated NBR (eq. 11). The ratio of acrylonitrile (ACN) to butadiene has a direct effect on the properties and the nature of the pol5nners. As the ACN content increases, the oil resistance of the poljnner increases (14). As the butadiene content increases, the low temperature properties of the polymer are improved. Nitrile rubber is much like SBR in its physical properties. It can be compoimded for physical strength and abrasion resistance using traditional fillers such as carbon black, silica, and reinforcing clays. The primary benefit of the polymer is its oil and solvent resistance. At a medium ACN content of 34% the volume swell in IRM 903 oil at 70°C is typically 25-30%. Nitrile rubber can be processed on conventional rubber equipment and can be compression, transfer, or injection molded. It can also be extruded easily. Nitrile rubber compoimds have good abrasion and water resistance. They can have compression set properties as low as 25% with the selection of a proper cure system. The temperature range for the elastomers is from -30 to 125°C. The compounds are also plasticized nsing polar ester plasticizers. 

Thanks to all these properties, the dolocarbonate seems promising for different applications, first of all for all the applications of traditional low density mineral fillers. This material could for instance be used as a component in thermal insulating materials like panels or foams, as a filler in mortars or plasters or concretes to decrease their thermal conductivity, as a filler in polymer or rubber compositions to improve their fire and/or mechanical properties, as a filler in paints, papers, cosmetic compositions, as a rheology modifier (viscosifying agent) in mineral slurries, glues, bitumen or asphalts, polymer compositions, as an ad- or absorbant in different applications such as water or flue gas treatment or even in the field of catalysis, as e.g. a catalyst support, or as a carrier for perfumes, aromas, active substances, medicines... 

It is apparent from considerations of the structure in Section 4.2 that semi-crystalline polymers are essentially two-phase materials and that the increase in modulus is due to the presence of the crystals. Traditional ideas of the stiffening effect due to the presence of crystals were based upon the statistical theory of elastomer deformation (Section 5.3.2). It was thought that the crystals in the amorphous rubber behaved like crosslinks and produced the stiffening through an increase in crosslink density rather than through their own inherent stiffness. Although this mechanism may be relevant at very low degrees of crystallinity it is clear that most semi-... 

As emphasized above, the concept of nanoreinforcement is far less practiced for TPEs than for thermoplastics [1,2,4,6,8], thermosets [1,2,8,11] and even for traditional rubbers [3,12]. This remark holds especially for addition and condensation TPEs. On the contrary, considerable amount of work was done on olefinic and styrenic TPEs. What is the reason for paying little attention to the nanoreinforcement of TPEs This is likely due to the fact that the properties of addition and condensation TPEs can be tailored upon request via the related synthesis. Recall that this was also the major argument for their less explored blending with other polymers. A further analogy with blending is that markedly more reports addressed the nanoreinforcement of TPUs compared to poly(ether amide) and poly(ether ester) block copolymers (see also Chapter 15). 

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