Method of preparation of cardo polyetherketone (PEK-C) structural foam material
A method of preparation of a cardo polyetherketone structural foam material, including the following steps: 1) performing a mould pressing on a cardo polyetherketone resin by a high-temperature vulcanizing machine to prepare a foaming billet; 2) placing the foaming billet in a foaming cavity of a mould-pressing machine, performing a penetration and a swelling by introducing a supercritical fluid to achieve diffusion equilibrium, forming a polymer-supercritical fluid homogeneous solution, and 3) making the polymer-supercritical fluid homogeneous solution supersaturated through a sudden release of the inner pressure of the system, thereby inducing nucleation and foaming, and finally forming a structural foam having a closed pore structure with a uniform pore size and an adjustable pore density. The production process of the present invention is clean, environmentally friendly, and has relatively high efficiency. The obtained structural foam has good mechanical properties.
1. A method of preparation of a cardo polyetherketone structural foam material, comprising the following steps:
1) performing a mould pressing on a cardo polyetherketone resin by a high-temperature vulcanizing machine to prepare a billet having a thickness of 3-10 mm, wherein in step 1), multiple surface pressures ranging from 0.1 MPa to 3 MPa are applied before the mould pressing is performed;
2) placing the billet in a cavity of a preheated mould-pressing machine, and introducing a supercritical fluid for a penetration and a swelling; and
3) inducing a nucleation and a foaming by controlling a pressure change to form the cardo polyetherketone structural foam material having a closed pore structure.
2. The method of preparation of the cardo polyetherketone structural foam material of claim 1 , wherein, the cardo polyetherketone resin in the step 1) is an amorphous structure having a structure of formula (1):
wherein, 1≤t≤5; X, n are positive integers, and y is a non-negative integer; and
the cardo polyetherketone resin loses 5% by weight at a temperature of equal to or higher than 400° C., and loses 10% by weight at a temperature of equal to or higher than 500° C.
3. The method of preparation of the cardo polyetherketone structural foam material of claim 1 , wherein, a viscosity of the cardo polyetherketone resin in the step 1) ranges from 0.4 dl/g to 1.2 dl/g.
4. The method of preparation of the cardo polyetherketone structural foam material of claim 1 , wherein, a viscosity of the cardo polyetherketone resin in the step 1) ranges from 0.6 dl/g to 0.9 dl/g.
5. The method of preparation of the cardo polyetherketone structural foam material of claim 1 , wherein, the cardo polyetherketone resin in the step 1) has a glass transition temperature ranging from 208° C. to 230° C.
6. The method of preparation of the cardo polyetherketone structural foam material of claim 1 , wherein, a process of the mould pressing in the step 1) comprises:
preheating at a temperature of 200-230° C., and compacting and discharging gas under a first surface pressure of 0.1-2 MPa for 10 min;
slowly increasing the temperature from 230° C. to 280° C. within a heating time of 20 min, with a second surface pressure of 2-3 MPa during the heating time;
then, performing the mould pressing at 280-295° C. with a mould-pressing pressure of 4.5-6 MPa and a moulding time of 30-45 min; and
finally, cooling and releasing from the mould to obtain the billet having the thickness of 3-10 mm.
7. The method of preparation of the cardo polyetherketone structural foam material of claim 1 , wherein, a temperature inside the cavity of the mould-pressing machine in the step 2) is 230-265° C., the supercritical fluid is supercritical CO 2 , a pressure of the supercritical fluid is 7.5-15 MPa, and a duration of the swelling and penetration is 30-180 min.
8. The method of preparation of the cardo polyetherketone structural foam material of claim 1 , wherein, the pressure change in the step 3) ranges up to 15 MPa, and a pressure change rate is 75-150 MPa/s.
9. The method of preparation of the cardo polyetherketone structural foam material of claim 2 , wherein, a viscosity of the cardo polyetherketone resin in the step 1) ranges from 0.4 dl/g to 1.2 dl/g.
10. The method of preparation of the cardo polyetherketone structural foam material of claim 2 , wherein, a viscosity of the cardo polyetherketone resin in the step 1) ranges from 0.6 dl/g to 0.9 dl/g.
11. The method of preparation of the cardo polyetherketone structural foam material of claim 2 , wherein, the cardo polyetherketone resin in the step 1) has a glass transition temperature ranging from 208° C. to 230° C.