Crystalline typical

Unlike the lower molecular weight poly(ethylene oxide)s these materials are tough and extensible, owing to their high molecular weight and their crystallinity. Typical mechanical properties of the polymer are given in Table 19.5... 

In terms of copolymerization, the addition of a comonomer to a crystalline polymer usually causes a marked loss in crystallinity, unless the second monomer crystallizes isomorphously with the first. Crystallinity typically decreases very rapidly, accompanied by reductions in stiffness, hardness, and softening point, as relatively small amounts (10-20 mol%) of the second monomer are added. In many cases, a rigid, fiber-forming polymer is converted to a highly elastic, rubbery product by such minor... 

Fluoroelastomers are for the most part based on the combination of vinylidene fluoride (VDF) with other monomers, which disrupt the high crystallinity typical for the PVDF homopolymer. The properties of the resulting elastomeric materials are determined by the short VDF sequences and low or negligible crystallinity. 

This chapter reviews the general aspects of the CSD method for ferroelectric thin-film preparation, with attention given to precursors, solution chemistry, and process development. An additional focus of the chapter is on the structural evolution of the solution precursor into the crystalline (typically perovskite) state and the impact of precursor chemistry and film fabrication conditions on the transformation process. Lastly, the chapter reviews the advantages and disadvantages of the CSD method and discusses industrial implementation of the technique. 

Source of the irregularity Polymer Degree of crystallinity (%) (typical)... 

PVDF is a linear partially fluorinate polymer containing 59.4 wt% fluorine and 3wt% hydrogen. The high level of intrinsic crystallinity, typically near 60%, provides stiffness, toughness, and creep resistant properties. Incorporation of various fluorinated comonomers at low levels, typically about 5-20 wt%, enhances flexibility and clarity of PVDF by reducing the crystallinity, which in turn reduces the end use temperature rating. PVDF is commercially produced via free radical polymerization either with emulsion or suspension processes. 

Features Nominal density 0.941-0.965 glcirt Melting Point 130-137°C, with high crystallinity Typical process temperature range 190-230°C Usually unreinforced but can be filled. 2% carbon black inhibits photo-oxidation (UV degradation). 

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