Semicrystalline PEEK

Polyarylether Ketones. The aromatic polyether ketones are tme thermoplastics. Although several are commercially available, two resins in particular, poly ether ether ketone [31694-16-3] (PEEK) from ICI and poly ether ketone ketone (PEKK) from Du Pont, have received most of the attention. PEEK was first synthesized in 1981 (20) and has been well studied it is the subject of numerous papers because of its potential use in high performance aircraft. Tough, semicrystalline PEEK is prepared by the condensation of bis(4-fiuorophenyl) ketone with the potassium salt of bis(4-hydroxyphenyl) ketone in a diaryl sulfone solvent, such as diphenyl sulfone. The choice of solvent is critical other solvents, such as Hquid HE, promote the reaction but lead to premature low molecular-weight crystals, which do not exhibit sufficient toughness (21). 

Several liquid cryatalline polymers were melt blended with an amorphous (Ultem) and two semicrystalline (PEEK and PPS) engineering thermoplastics in a single screw extruder. Flat film was processed with different degrees of stretch imparted while the film was being cooled. In the case of Vectra, which was thought to be ideally suited to be blended with PPS based on thermal and rheological... 

Nakanishi, H., and Jean, Y. C., Positronium formation at free-volume sites in the amorphous regions of semicrystalline PEEK, J. Polym. Sci. B, 27, 1419-1424 (1989). 

Normally, PEEK is a linear molecule. Chen et al synthesized PEEK single size macrocycles and macrocyclic oligomer mixtures (22). The macrocycle monomers can be ring opening polymerized into semicrystalline PEEK with the initiators of a catalytic amount... 

The morphology of semicrystalline PEEK fractions in relation to their molecular weight has been recently investigated 46). The PEEK fractions were crystallized from the glassy state between 250 to 340 °C. The main results of this study will be... 

Aprotic polar solvents have to be used for several reasons. They are often good solvents for both monomers (including phenolates) and amorphous polymers. In addition, they can also stabilize the Meisenheimer intermediates. Common aprotic polar solvents, such as DMSO, /V,/V-dimcthyl acetamide (DMAc), DMF, N-methyl pyrrolidone (NMP), and cyclohexylpyrrolidone (CHP) can be used. Under some circumstances, very high reaction temperature and boiling point solvents such as sulfolane and diphenyl sulfone (DPS) have to be used due to the poor reactivity of the monomers or poor solubility of the resulting, possibly semicrystalline polymers, as in the PEEK systems. 

AS4/PEEK ICI Americas Inc. ICI Polyetherether ketone, semicrystalline thermoplastic... 

Poly(ether ether ketone) (PEEK) is an aromatic, high performance, semicrystalline polymer with extremely good thermal stability, chemical resistance, and electrical and mechanical properties. This polymer shows little solubility in organic solvents due to the crystallinity. One of the first ways to characterize PEEK was by sulfonating the polymer. By adding sulfonic acid groups to the backbone, the crystallinity decreased and solubility increased.Commercially available Victrex appears to be one of the more interesting poly(arylene ether) s used for postmodification. 

The model PBZT/ABPBI molecular composite system is limited since the rod and the matrix do not possess glass transition temperatures for subsequent post form consolidation. In an effort to improve the processability for molecular composites, thermoplastics were used as the host matrix. Processing from acidic solvents requires the thermoplastic host to be soluble and stable in meth-anesulfonic add. Thermoplastic matrices were investigated including both amorphous and semicrystalline nylons [71,72], polyphenylquinoxaline (PPQ) [73] and polyetheretherketone (PEEK) [74], Table 5 shows the mechanical properties obtained for various processed PBZT thermoplastic molecular composite systems. As an example, the PBZT/Nylon systems showed 50-300% improvement over uniaxially aligned chopped fiber composite of comparable compositions. However, the thermally-induced phase separation during consol-... 

Higher values can be reached for semi-crystalline polymers below Tg the crystalline phase is stiffer than the glassy amorphous phase (e.g. PEEK, E 4 GPa). Semicrystalline polymers above Tg have, however, a much lower E-value, such as PE (0.15 to 1.4 GPa) and PP 1.3 GPa) E is, in these cases, strongly dependent on the degree of crystallinity and on the distance to Tg. Sometimes a low modulus is also found for semi-crystalline polymers below Tg, due to the effect of one or more secondary transitions a strong example is PTFE (E = 0.6 GPa ). 

A number of authors have found that the lifetime spectra of semicrystalline polymers are best resolved into three components. In a study of PEEK (poly(ether ether ketone)), Nakanishi et al [14] found that a three component fit was best. They observed that the o-Ps lifetime (r3) did not change with an increasing amounts of crystallinity, but the o-Ps yield (I3) decreases linearly with an increasing amount of crystallininty. It was also demonstrated that I3 extrapolates to 0 at 100% crystallinity. No o-Ps lifetime was observed that might be attributed to the annihilation within the crystalline regions of the polymer. Lind et al [43] found a similar result for polypropylene where the x3 component changed very little with the amount of crystallinity, but the I3 value decreased with an increasing amount of... 

It should he noted that the first pair of polymers (PMMA and PVAc) are not capable of crystallizing and, therefore, are always present in the amorphous state, which is not the case with the second pair. PET and PEEK are high-melting semicrystalline polymers distinguished by relatively low crystallization rates and... 

Figure 3.5 shows the temperature variation of H for the four above mentioned polymers, namely PMMA, PVAc, PET and PEEK. In the case of the two amorphous polymers (PMMA and PVAc) H decreases with T and the Tg value can he clearly identified with a hend in the 7/ vs T plot. However, the two semicrystalline materials quenched into the amorphous state (PET and PEEK) show an apparent maximum just before the glass transition takes place. Also, in the case of PET tested immediately after quenching it is observed that H increases with T above room temperature. These phenomena will be discussed in Section 3.3 in the light of the physical ageing undergone by the above polymers. It is seen that H follows an exponential decrease as a function of T given by (see eq. (2.5))... 

This equation assumes that the semicrystalline polymer is a two-phase system and that the microhardness (yield) is due to plastic deformation taking place only in the crystalline regions. However, for polymers like PET or PEEK, when Tg > T the microhardness of the amorphous phase Ha 0 (Deslandes etal, 1991). 

Materials. The amorphous matrix polymer was polyetherimide (Ultem 1000) sold by the General Electric Company. The semicrystalline matrices were PEEK and a high molecular weight polyphenylenesulfide (PPS) provided by ICI and Phillips Petroleum Co. (Barthesville, OK.), respectively. The reinforcing phase was one of several LCPs a liquid crystalline aromatic copolyester consisting of 73 %... 

Polyetherimide was found to be miscible with polyetheretherketone (PEEK) exhibiting a single T. Since PEEK is a semicrystalline polymer with a T of ca. 150°C, the blend should have... 

PEEK is semicrystalline with a melting temperature (T ) of 335°C and a glass transition temperature (Tg) of 145°C. The degree of crystallinity can very from 40% (slow cooling) to essentially amorphous (quenching), but is usually about 35%. 

Materials for sintering and melting are plastics, metals, or ceramics. Plastics may be unfilled or filled with glass or aluminum spheres or egg-shaped geometries to improve properties like durability and thermal resistance. Also nanoscale particles are used. Unfilled plastics are mostly commodities like semicrystalline polyamides from the PAl 1 or PA12 type or amorphous plastics like polystyrene (PS). Engineering plastics like PEEK are available. 

A blend of HNA/0.73PHB with a more rigid semicrystalline polymer, poly (ether ether ketone) (PEEK) with a Tg of and of 338 C,... 

Slow, primary crystallization of PEEK is analyzed in Fig. 6.98 using long-time, quasi-isothermal TMDSC at 606.5 K, and in Fig. 6.99, using TMDMA at 605 K. The analysis of the TMDSC data is further illustrated in Fig. 6.100 and reveals an increase in heat capacity with time and crystallinity, instead of the decrease expected from a lower heat capacity of a semicrystalline sample. The crystallinity is derived from the integral of the total heat-flow rate, with time in Fig. 6.98. From Fig. 6.99 it... 

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