ABSTRACT
Objective To evaluate the static viscoelastic properties of the porous gradient UHMWPE material by the creep, stress relaxation and creep recovery tests. Method The porous gradient UHMWPE material was prepared by the template leaching (T-L) method. The porous structure was characterized by scanning electron microscopy(SEM) and the porosity and pore distribution of porous layer were measured by a pressure mercury analyzer. The creep, stress relaxation and creep recovery properties were tested by the experimental determination of flat indentation. Results The porous layer of T-L UHMWPE was well bonded with the substrate material. With the increase of NaCl content, the porosity and pore size distribution scope improved clearly. Creep deformation and modulus presented a nonlinear increase with time and the stress and modulus of stress relaxation showed a nonlinear decrease with time. The buffering capacity for impact loads of porous gradient UHMWPE was significantly higher than the compact UHMWPE. Experimental results showed that the creep recovery properties of the reasonable porosity of U50 and U60 samples were almost similar to the compact UHMWPE material. But the higher porosity caused the increase of the plastic deformation. Conclusions The porous structure of UHMWPE effectively increased the elastic property and strain response sensitivity, which may be beneficial to improve the lubrication of frictional contact surfaces and reduce the wear of artificial joints.