Poly modified creep

By contrast, SolomatovI " found that the creep deformation in flexure of poly(vinyl acetate-dibutyl maleate)-modified mortar was several times larger than that of unmodified concrete at 20°C, and its catastrophic deformation occurred at 50°C since the polymer developed a high plasticity above its glass transition temperature. 

Poly(isobutylene) only crystallizes under stress. Because of the low glass transition temperature (-70 C), its lack of crystallinity, and the somewhat weak intermolecular forces, poly (isobutylene) is an elastomer. The low-molar-mass material is used as an adhesive or viscosity improver. The higher-molar-mass products are employed as rubber additives or for very airtight tubes. The cold flow (creep) can be diminished or eliminated by the addition of polyethylene. Poly(isobutylenes) modified by copolymerization are used as protective sheeting for building sites and as anticorrosive coverings (e.g., a copolymer of 90% isobutylene and 10% styrene). 

In the original paper [20], the authors reported work on the uniaxial tension of plasticized poly(vinyl chloride), sulphur vulcanizates of butyl rubber and polyisobutylene. Very successful predictions were made at extension ratios of up to 5. Zapas and Craft [21] applied their formulation to multistep stress relaxation and creep and recovery of both plasticized poly(vinyl chloride) and pol3dsobuty-lene. McKenna and Zapas applied a modified form of the model to the torsional deformation of poly(methyl methacrylate) [22]. McKenna and Zapas [23] have used the model in analysis of the tensile behaviour of carbon-black-fllled butyl rubbers. 

They also used modified impregnation method to make ceUulose/cellulose nanocomposites. These nanocomposites also showed improved tensile and creep properties over neat CNCs. They then used melt compounding technique to manufacture CNC/poly(Iaclic acid) nanocomposites, where polyethylene glycol (PEG) was used as plasticizer and maleic anhydride (MA) was used as a coupling agent. Composites made with and without plasticizer both showed increase in tensile properties. However, the maximum improvement in tensile properties was observed for composites made without plasticizer. The tensile modulus of these composites for 5 wt% CNCs improved by about 35 %, the tensile strength by about 90 %, and elongation to break by about 35 %. 

Kolarik J and Pegoretti A (2004) Indentation creep of heterogeneous blends poly(ethyl-ene-terephthalate)/impact modifier, Polym Testing 23 113-121. 

Butyl rubber is an elastomeric polymer used widely in adhesives and sealants, both as primary binders and as tackifiers and modifiers. Butyl rubber is poly(methylpropene-co-2-methyl-1,3-butadiene) or poly(isobutylene-co-isoprene). The latter is a copolymer of isobutylene with a small amount of isoprene [28]. These materials have relatively low strength and tend to exhibit creep under load. They are useful in packaging applications where their low permeability to gases, vapors, and moisture can be exploited. Butyl rubber is also used as an adhesive sealant. It is generally applied from a solvent-based solution [3,7]. Table 5.7 summarizes some of the important properties of butyl rubber adhesives. 

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