A rotary displacement pump (2; 62) for pumping flowable viscous materials, said rotary displacement pump comprising: a liner (26, 36; 70, 80); a rotor configured to be driven by a shaft; said rotor including a shaft portion and a radially protruding web having a configuration of an undulatory disk type; a scraper gate (38; 82) having an engagement slot of predetermined radial height and predetermined axial width, said engagement slot engaging said protruding web of said rotor; said scraper gate (38; 82) being supported by a scraper gate guide (40; 84) so as to be retained in circumferential direction and to allow a reciprocating movement in a substantially axial direction; a pump housing comprising a front end part and a rear end part, said pump housing enclosing said liner (26, 36; 70, 80), said rotor, said scraper gate (38; 82) and said scraper gate guide (40; 84), said shaft extending through said rear end part of said pump housing; said liner (26, 36; 70, 80) including a first liner element (26; 70) and a second liner element (36; 80), said first and second liner elements (26, 36; 70, 80) abutting to each other laterally along a radially outer abutment portion so as to form a liner channel through which said radially protruding web of said rotor runs and to define an enclosure that encircles a portion of said radially protruding web of said rotor; an inlet chamber and an outlet chamber being defined by said liner (26, 36), said scraper gate and said scraper gate guide or by said liner (70, 80), said pump housing, said scraper gate and said scraper gate guide; said scraper gate (38; 82) together with said scraper gate guide (40; 84) forming a partition between said inlet chamber and said outlet chamber; said inlet and outlet chambers being provided with respective inlet and outlet ports (16, 18); said liner channel extending from said inlet chamber to said outlet chamber; said web of said rotor being rotatable through said inlet chamber, said liner channel, said outlet chamber and said slot of said scraper gate (38; 82); characterized in that said scraper gate (38; 82) and/or said liner (26, 36) consists of 85 to 95 Vol-% of a Polyethylene basis material of ultra-high molecular weight and 15 to 5 Vol-% of glass particles of spherical or oval shape distributed within said Polyethylene basis material, such that the surface of said scraper gate (38; 82) and/or said liner (26, 36; 70, 80) comprising rounded surface portions formed by glass particles that protrude out constitutes a hard slide face for the flowable viscous materials to be pumped. a liner (26, 36; 70, 80); a rotor configured to be driven by a shaft; said rotor including a shaft portion and a radially protruding web having a configuration of an undulatory disk type; a scraper gate (38; 82) having an engagement slot of predetermined radial height and predetermined axial width, said engagement slot engaging said protruding web of said rotor; said scraper gate (38; 82) being supported by a scraper gate guide (40; 84) so as to be retained in circumferential direction and to allow a reciprocating movement in a substantially axial direction; a pump housing comprising a front end part and a rear end part, said pump housing enclosing said liner (26, 36; 70, 80), said rotor, said scraper gate (38; 82) and said scraper gate guide (40; 84), said shaft extending through said rear end part of said pump housing; said liner (26, 36; 70, 80) including a first liner element (26; 70) and a second liner element (36; 80), said first and second liner elements (26, 36; 70, 80) abutting to each other laterally along a radially outer abutment portion so as to form a liner channel through which said radially protruding web of said rotor runs and to define an enclosure that encircles a portion of said radially protruding web of said rotor; an inlet chamber and an outlet chamber being defined by said liner (26, 36), said scraper gate and said scraper gate guide or by said liner (70, 80), said pump housing, said scraper gate and said scraper gate guide; said scraper gate (38; 82) together with said scraper gate guide (40; 84) forming a partition between said inlet chamber and said outlet chamber; said inlet and outlet chambers being provided with respective inlet and outlet ports (16, 18); said liner channel extending from said inlet chamber to said outlet chamber; said web of said rotor being rotatable through said inlet chamber, said liner channel, said outlet chamber and said slot of said scraper gate (38; 82);