Structures and Mechanical Properties of PEEK/PEI/PES Plastics Alloys Blent by Extrusion Molding Used for Cable Insulating Jacketing

The PEEK/PEI/PES plastic alloys were processed by twin-screw extruder at 370 °C with five mass ratios of 70/30/0, 70/25/5, 65/30/5, 60/30/10, and 60/35/5, respectively. Their thermal properties and crystallization behavior were investigated by the differential scanning calorimetry. The measured results showed that all the plastic alloys had a single glass-transition temperature (Tg), which revealed good compatibility among the three members of PEEK, PEI and PES. For the alloy with the mass ratio of 70/30/0, the minimum Tg of 160.6 °C was obtained, but the alloy of 60/35/5 had the maximum Tg of 164.5 °C, which indicate that PEI, PES and the amorphous plastics could increase Tg of the PEEK alloys and was 20 °C higher than that of pure PEEK. The melting points (Tm) of these alloys were from 334.4 °C to 336.3 °C and their crystallinity degrees were from 35.8% to 37.8%, whereas both were slightly higher than that of pure PEEK. However, the cold crystallization temperatures of the alloys were lower than that of pure PEEK, which could be attributed to the reason that the rheological properties of the alloys were improved by PEI. Tensile strength of the plastic alloy with the ratio of 60/30/10 presented the maximum value of 108 MPa and was higher than that of pure PEEK. After thermal ageing at 158 °C (below Tg) or 178 °C (above Tg) respectively for 168 h, their tensile strengths decreased only slightly, but elongation rates at break reduced significantly, of which thermal ageing above Tg would recede the elongation at break more severely. The plastic alloy of 60/30/10 could be used as the cable insulating jacketing for nuclear power station.