Viscoelastic properties of blends

Prest,W.M., Jr. Viscoelastic properties of blends erf entangled polymers, J. Polymer... 

PP-g-MA/amine-terminated PS Extrusion/morphology/varying viscoelastic properties of blend components/comparison to uncompatibilized blend Omonov et al. 2007... 

The elastic and viscoelastic properties of blends of PP and ethylene-propylene (EP) were investigated with the force modulation technique by Nysten and co-workers (250,251). In addition to a mapping of the distribution of the rubbery nodules of EP at the surface, the subsurface distribution of these nodules could be estimated. While the FMM data yielded qualitative data, more recent indentation mapping based on f-d curves allowed Nysten and co-workers to obtain quantitative information of the surface elastic modulus (252). 

The viscoelastic properties of blends of narrow-distribution polystyrenes and poly(methyl methacrylate)s have also been studied in detail by Onogi and collaborators. 

The results reported in this work on some selected polymer blends demonstrate that the melt rheology of multiphase systems is very complex, even in the linear viscoelastic domain. The main features exhibited by molten immiscible polymer blends are an increase of elasticity at low frequencies and longer relaxation times compared with that of the matrix. The linear viscoelastic properties of blends are satisfactorily described by the Palierne emulsion model and the enhancement of elasticity is ascribed to the deformability of the minor phase s droplets. 

Tackifying resins enhance the adhesion of non-polar elastomers by improving wettability, increasing polarity and altering the viscoelastic properties. Dahlquist [31 ] established the first evidence of the modification of the viscoelastic properties of an elastomer by adding resins, and demonstrated that the performance of pressure-sensitive adhesives was related to the creep compliance. Later, Aubrey and Sherriff [32] demonstrated that a relationship between peel strength and viscoelasticity in natural rubber-low molecular resins blends existed. Class and Chu [33] used the dynamic mechanical measurements to demonstrate that compatible resins with an elastomer produced a decrease in the elastic modulus at room temperature and an increase in the tan <5 peak (which indicated the glass transition temperature of the resin-elastomer blend). Resins which are incompatible with an elastomer caused an increase in the elastic modulus at room temperature and showed two distinct maxima in the tan <5 curve. 

The SAS data files that wera created as a results of the operations noted earlier have the important property that all three viscoelatic properties have either been measured or interpolated to the same temperature. Therefore one can merge data sets for different polymers by temperature (a SAS data set manipulation) and then perform blend calculations on the data quite simply in SAS. For example, one can calculate the expected viscoelastic properties of a blend from the pure components and their volume fraction using the equations of Uemura and Takaynagi (8). 

Ninomiya,K., Ferry,J.D., Oyanagi,Y. Viscoelastic properties of polyvinyl acetates. II. Creep studies of blends. J. Phys. Chem. 67,2297-2308 (1963). 

Watanabe H, Sakamoto T, Kotaka T (1985) Viscoelastic properties of binary blends of narrow molecular weight distribution polystyrene. 2. Macromolecules 18(5) 1008-1015 Watanabe H, Yao M-L, Osaki K (1996) Comparison of dialectric and viscoelastic relaxation behaviour of polyisoprene solutions Coherence in subchain motion. Macromolecules 29(1) 97—103... 

Abbasi F, Mirzadeh H, Katbab AA (2002) Comparison of viscoelastic properties of polydimethylsiloxane/poly(2-hydroxyethyl methacrylate) IPNs with their physical blends. J Appl Poly Sci 86(14) 3480—3485... 

Schneider HA, Cantow HJ, Percec V. (1982) Donor-acceptor complexation in macromolecu-lar systems. 1. Viscoelastic properties of polydonor-polyacceptor blends and of corresponding copolymers. Polym. Bull. (Berlin, Germany) 6 617-621. 

Homopolymers are sometimes modified by a mechanical admixture of another homopolymer. As only about 5 % of pairs of all known polymers are mutually miscible, compatibility may be a problem in mixtures (blends). Copolymerization is technically applied to overcome, for example, the brittleness of polystyrene, polypropylene and PVC. It is also applied for improving the curing properties and modifying the viscoelastic properties of rubbers. By copolymerization, the relation between the hydrophobic and hydrophilic properties of macromolecules can also be modified. Their resistance to solvents may be enhanced. 

Blend morphology commonly depends on the weight fraction and viscoelastic properties of each component, the interfacial tension between components, the shape and sizes of the discontinuous phase, and the fabrication conditions and setup. Most rheological experiments applied to homogeneous melts can also be similarly applied to these immiscible blends [55,63,88,89]. The viscoelastic properties arising from these studies should be labeled with a subscript apparent since the equations used to translate rheometer transducer responses to properties incorrectly assume that the material is homogeneous. Nevertheless, these apparent properties are often found to be excellent metrics of fabrication performance. 

Varkey, J.T. Augustine, S. Groeninckx, G. Bhagawan, S.S. Rao, S.S. Thomas, S. Morphology and mechanical and viscoelastic properties of natural rubber and styrene butadiene rubber latex blends. J. Polym. Sci. B Polym. Phys. 2000,38 (16), 2189-2211. 

Coffin, D. R., Fishman, M. L. 1993. Viscoelastic Properties of Pectin/Starch Blends. Journal of Agricultural and Food Chemistry, Vol. 41, pp. 1192-1197. 

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