Polymer, amorphous shape

If a modulus is plotted as a function of temperature, a very characteristic curve is obtained which is different in shape for the different types of polymer amorphous (glassy) polymers, semi crystalline polymers and elastomers (cross-linked amorphous polymers). 

Mather, P.T., Liu, C., 2011. Blends of Amorphous and SemicrystaUine Polymers Having Shape Memory Properties. Patent, PCX number PCT/US2003/032329. 

Chapter 3 discusses polymer chain shapes and packing in both crystalline and amorphous forms, while Chapter 6 explains the effect of polymer processing on the microstructure on a millimetre length scale. You should be able to synthesise these views, and use models on appropriate scales to explain the mechanical and physical properties of products. 

SMP based on miscible blends of semicrystalline polymer/amorphous polymer was reported by the Mather research group, which included semicrystalline polymer/amorphous polymer such as polylactide (PLA)/poly vinylacetate (PVAc) blend [21,22], poly(vinylidene fluoride) (PVDF)/PVAc blend [23], and PVDF/polymethyl methacrylate (PMMA) blend [23]. These polymer blends are completely miscible at all compositions with a single, sharp glass transition temperature, while crystallization of PLA or PVDF is partially maintained and the degree of crystallinity, which controls the rubbery stiffness and the elasticity, can be tuned by the blend ratios. Tg of the blends are the critical temperatures for triggering shape recovery, while the crystalline phase of the semicrystalline PLA and PVDF serves well as a physical cross-linking site for elastic deformation above Tg, while still below T ,. 

Nguyen, T.D., Qi, H., Castro, F., and Long, K.N. (2008) A thermoviscoelastic model for amorphous shape memory polymers incorporating stmctural and stress relaxation. Journal of the Mechanics and Physics of Solids, 56, 2792-2814. 

Constitutive Modeling of Amorphous Thermosetting Shape Memory Polymer and Shape Memory Polymer Based Syntactic Foam... 

The SSE process based on changes in polymer-billet shape is, first of all, characterized by the EDR value. The limited EDR value is determined by polymer type, molecular weight and morphology. For example, for HDPE it may reach more than 40 (1). For polyoxymethylene (POM), polypropylene (PP), PTFE the maximum values of draw ratio equal 10,6, and 4 (20-22), respectively. For polymethylmethacrylate (PMMA), polystyrene (PS), polycarbonate (PC), and other amorphous polymers they are even lower (21,23). The extruded specimens are highly oriented and possess improved mechanical properties. In the case of semicrystalline polymers, the extrusion results in a considerable increase of tensile modulus and strength (1,2). With amorphous polymers, a considerable increase of plasticity is observed alongside with increase of tensile moduli (21,23). 

By using this method, polymer nanoparticles of different polymers have been reported (Martmez-Tong et al. 2013, 2014 Landfester 2001). For amorphous polymers, the shape of the nanoparticles generated by this technique is spherical (Fig. 6.2). Variations of physical properties like the glass transition temperature of the polymer cmifined into the shape of this nanoparticles have been reported in the literature (Martmez-Tong et al. 2013, 2014). 

Heuchel, M., Cui, J., Kratzk, K. et al. (2010) Relaxation based modeling of tunable shape recovery kinetics observed under isothermal conditions for amorphous shape-memory polymers. Polymer, 51, 6216-6218. 

In polymer blends where the major matrix is amorphous in nature, and the dispersed phase is a crystal-Uzable polymer, the shape and size of the dispersed phase is a complex function of the blend composition, the melt viscosity of the dispersed phase and matrix, the viscosity ratio, the interfacial tension and the processing. And when there is the addition of nanoparticles, the localization of the nanoparticles... 

Elastomers are amorphous polymers that have the ability to stretch out and spring back to their original shapes. These polymers must have low Tg values and a small amount of cross-linking to prevent the chains from slipping over one another. In addition, the chains must have an irregular shape to prevent crystallite... 

Elastomer (Section 31.5) An amorphous polymer that has the ability to stretch out and spring back to its original shape. 

Solid state materials have been studied by nuclear magnetic resonance methods over 30 years. In 1953 Wilson and Pake ) carried out a line shape analysis of a partially crystalline polymer. They noted a spectrum consisting of superimposed broad and narrow lines which they ascribed to rigid crystalline and amorphous material respectively. More recently several books and large articles have reviewed the tremendous developments in this field, particularly including those of McBrierty and Douglas 2) and the Faraday Symposium (1978)3) —on which this introduction is largely based. 

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