Orientation solid state extrusion

Dilatometric studies have demonstrated the negative thermal expansivity for many oriented crystalline polymers 64,170 176). The results of these experimental studies may be summarized as follows. Cold-drawing of PE below Tm 172) and solid-state extrusion under elevated pressure 170 1711 lead to a monotonous decrease of the positive thermal expansion coefficient with increasing draw ratio. At a certain degree of orientation, dependent on temperature, PM becomes negative with Pi < Pell (Fig. 16). This is the second way of reaching negative expansivity applied, e.g. to POM (w = 63 % Tdr = 423 K) 173>. 

Solid-state extrusion has also yielded some of the highest properties for uniaxially oriented morphologies. Tensile moduli (210 GPa) nearing the theoretical value of a polyethylene single crystal have been attained.f ... 

Pan, S.J. Tang, H.I. Hiltner, A. Baer, E. Biaxial orientation of polypropylene by hydrostatic solid state extrusion. Part II. Morphology Properties 1987, 27 (12), 869. 

Mascia, L. Zhao, J. Transverse orientation dies for solid state extrusion of polymers. Part II. Orientation and properties of extrudates. Polym. Eng. Sci. 1991, 31 (9), 677. 

In addition, surface forces [240] and shear fields [%, 188, 241-243] have successfully been employed in orienting the LCPs. Solid state extrusion [10, 188] and mdt-spinning [96] produce fibers, with nearly perfect aligoonent of the director axes 0.9). This is demonstrated in Fig. 30. The H NMR spectra Ctop row) refer to melt-spun fibers of LCP 4 (a-CD ) and five different orientations of fiber axis and magnetic field. Drastical lineshape chan are observed when the sample is rotated. A detailed analysis, based on spectral simulations (bottom row), provides the parameters of micro- and macroorder, summarized in Table 9 [96]. 

Sawai D, Takahashi K, Imamina T et al (2002) Preparation of oriented p-form poly(L-lactic acid) by solid-state extrusion. J Polym Sci B Polym Phys 40 95-104... 

An extrusion technique that has siowiy been gaining popuiarity is solid-state extrusion. The polymer is forced through a die while it is below its melting point. This causes substantial deformation of the polymer in the die, but since the polymer is in the solid state, a very effective molecular orientation takes place. This orientation is much more effective than the one which occurs in conventional melt processing. As a result, extraordinary mechanical properties can be obtained. 

Keywords solid-state extrusion, roll-drawing, orientation, crystallinity, mechanical properties, a-relaxation, solid-state deformation, compression ratio, morphology, tie molecules, lamellar orientation, laminate theory, fibrillar structure, rolling. 

The most common orientation process is used to produce fibres and is described in research disclosures from ICI, academic literature and manufacturer processing guidelines. Melt spun fibres of PEKEKK have exhibited moduli as high as 13 GPa [33]. There are also a number of academic references to oriented material which, as expected, shows enhanced mechanical performance. Techniques such as solid-state extrusion [34] and die drawing have been applied to PEEK and a modulus of 11 GPa has been obtained [35]. Orientation processes are similar to those used for polyethylene terephthalate but there are some key differences in terms of orientation-induced crystallisation [36, 37]. 

Zachariades, A. E., Mead, W. T. and Porter, R. S. (1979) Recent developments in ultramolecular orientation of polyethylene by solid state extrusion, in Ultrahigh Modulus Polymers (A. Ciferri and I. M. Ward, eds), p. 77. Applied Science Publishers, London. 

Methods of Achieving Orientation. The most common ways of achieving orientation Tn semi crystal 1ine polymers are spinning from a gel, melt or solution, stretching in the solid state, or solid state extrusion. Biaxial orientation is found in blown films or in films prepared by passing a melt over a conical die. 

NEW METHODS OF PRODUCTION OF HIGHLY ORIENTED POLYMERS BY SOLID STATE EXTRUSION... 

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