Extended chain crystals polyethylene

Fig. 8. Superheating of polyethylene extended chain crystals. Curves 1) at 421.7 K, 2) at 419.2, 3) at 417.7 K, 4) at416.7K, 5) at 414.7 K. The equilibrium melting temperature is 414.6 K. Drawn after Ref.40). "w is the weight fraction molten, obtained by isothermal calorimetry...

Wunderlich, B. and Melillo, L. (1966) Surface recrystallization of polyethylene extended-chain crystals, Science, 154, 1329-1330. 

Pak J, Wunderlich B (2002) Reversible Melting of Polyethylene Extended-chain Crystals Detected by Temperature-modulated Calorimetry. J Polymer Sci, Part B Polymer Phys 40 2219-2227. 

Extended chain crystal (ECC) Folded chain crystal (FCC) Growth Growth rate Induction period Melt relaxation Molecular weight Nucleation Nucleation rate Nucleus Optical microscope (OM) Polyethylene Polymer Power law ... 

By variation of the conditions of crystallization (see Sect. 1.3.3.3) polyethylene can be obtained either as folded lamellae, as extended chain crystals (high strength fiber), or as so-called shish kebabs (fibrils with a morphology similar to cellulose). All these variants differ in properties. 

Fig. 20. Phase diagram of polyethylene. The difference between folded and extended chain crystal melting temperatures is largely a size effect (1 kbar = 100 MPa). Curve based on data of Ref. I19>...

The polyethylene samples examined are shown in Table III slowly cooled or quenched from melt, original monofilament, annealed, over drawn, cold drawn, single crystal, cast film, extended chain crystal, etc. The sample-probe distance can be chosen from TO to 260 mm. The setting angle is defined as the angle between the molecular plane and the be plane according to Bunn (1 1) as shown in Figure 12. 

Fig. 22 Ratio of growth rates Gioo/Gno vs. crystallization temperature for extended-chain crystals of Ciggfbgg from 2% (w/v) solution in octacosane (diamonds) and for linear polyethylene from 0.05% solutions in hexane (squares). The polyethylene crystal at Tc = 70.0 °C and the C198H398 crystals above Tc = 110 °C are non-truncated lozenges these form for any Guo/ cos( /2) > G100, where cp/2 = tan 1(flo/ o) and ao, b0 are unit cell parameters (cf Fig. 10). Data for PE are from [32] (from [45])...

Wunderlich B Melillio L (1968) Morphology and growth of extended-chain crystals of polyethylene. Makromol Chem 118 250... 

Polyethylene glycols (PEG) have been intensively characterized by thermal analytic methods. The melting points of PEG increase with the molecular weight and decreases with the content of water as a result of eutectic formation. " Corrigan studied the different DSC peaks of PEG Once folded chain crystals and extended chain crystals are present in PEG 6000, which results in two DSC peaks. In PEG of higher molecular mass, only folded chain crystals are present. Lower molecular mass PEG contain only extended chain crystals. Craig reviewed the thermal studies of PEG, including properties in aqueous solutions. " " ... 

Figure 12. (F—E) Characteristic FTIR spectrum of 110 chain folds in solution-grown single crystals of n-alkane Ci98H3g8 (spectrum of extended-chain crystals subtracted from that of once-folded crystals) (PESC) solution-grown single crystals of polyethylene (bulk PE) melt-crystallized linear polyethylene. All bands are CH2 wagging defect modes except the CH3 band at 1378 cm-1. Spectra recorded at 110 K (from ref 68 by permission of Elsevier Science Publ.)...

Extended, or fully extended, chain crystallites contain straight chains at least 200 nm long and have been obtained for only a few polymers, such as polytetrafluoroethylene (PTFE), polyethylene and polychlorotrifluoro-ethylene, using special crystallisation techniques. Extended-chain polytetrafluoroethylene can be obtained by slow crystallisation from the melt the other two are obtained by crystallisation from the melt under elevated pressure. Solution crystallisation has so far not been shown to give rise to extended-chain crystals. 

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