A polymer composition comprising an olefin-derived polymer component and a surface-modified non-halogenated mineral filler composition comprising a particulate mineral filler core comprising hydroxide groups bound to divalent or trivalent metal ions, said particulate mineral filler core having on its surface (i) one or more short-chain organosilano groups independently selected from the group consisting of CH 3 -Si(OR a)(OR b)(OR c), CH 3 CH 2 -Si(OR a)(OR b)(OR c), CH 3 CH 2 CH 2 -Si(OR a)(OR b)(OR c), CH 3 CH(CH 3)-Si(OR a)(OR b)(OR c), (CH 3) 2 Si(OR a)(OR b), (CH 3 CH 2) 2 Si(OR a)(OR b), (CH 3 CH 2 CH 2) 2 Si(OR a)(OR b), (CH 3 CH(CH 3)) 2 Si(OR a)(OR b), (CH 3) 3 Si(OR a), (CH 3 CH 2) 3 Si(OR a), (CH 3 CH 2 CH 2) 3 Si(OR a), (CH 3 CH(CH 3)) 3 Si(OR a), (CH 3)(CH 3 CH 2)Si(OR a)(OR b), (CH 3)(CH 3 CH 2 CH 2)Si(OR a)(OR b), (CH 3)(CH 3 CH(CH 3))Si(OR a)(OR b), (CH 3 CH 2)(CH 3 CH 2 CH 2)Si(OR a)(OR b), (CH 3 CH 2)(CH 3 CH(CH 3))Si(OR a)(OR b), (CH 3)(CH 3 CH 2) 2 Si(OR a), (CH 3)(CH 3 CH 2 CH 2) 2 Si(OR a), (CH 3)(CH 3 CH(CH 3)) 2 Si(OR a), (CH 3) 2 (CH 3 CH 2)Si(OR a), (CH 3) 2 (CH 3 CH 2 CH 2)Si(OR a), (CH 3) 2 (CH 3 CH(CH 3))Si(OR a), (CH 3 CH 2) 2 (CH 3 CH 2 CH 2)Si(OR a), (CH 3 CH 2) 2 (CH 3 CH(CH 3))Si(OR a), CH 3 -Si(OR a)Cl 2, CH 3 CH 2 -Si(OR a)(O 2 CR)(OR c), and CH 3 CH 2 CH 2 -Si(OR a)(NR 2)(OR c); and (ii) one or more long-chain organosilano groups independently selected from the group consisting of CH 3 (CH 2) 7 -Si(OR a)(OR b)(OR c), CH 3 (CH 2) 8 -Si(OR a)(OR b)(OR c), CH 3 (CH 2) 9 -Si(OR a)(OR b)(OR c), CH 3 (CH 2) 10 -Si(OR a)(OR b)(OR c), (CH 3 (CH 2) 7) 2 Si(OR a)(OR b), CH 3 (CH 2) 7 -Si(OR a)(OR b)(Cl), CH 3 (CH 2) 7 -Si(OR a)(OR b)(NHCH 3), CH 3 (CH 2) 7 -Si(OR a)(OR b)(O 2 CCH 3), and CH 3 (CH 2) n -Si(OR a)(OR b)(OR c); wherein each occurrence of R a, R b, R c is independently selected from the group consisting of a divalent or trivalent metal atom on the surface of the particulate mineral filler core, a silicon atom in another organosilano group, hydrogen, and R, wherein R is a hydrocarbon group containing one to six carbon atoms; and wherein the long-chain organosilano groups are present in an amount of equal to or greater than three mole percent and up to fifty-five mole percent of combined molar amount of long-chain and short-chain organosilano groups. (i) one or more short-chain organosilano groups independently selected from the group consisting of CH 3 -Si(OR a)(OR b)(OR c), CH 3 CH 2 -Si(OR a)(OR b)(OR c), CH 3 CH 2 CH 2 -Si(OR a)(OR b)(OR c), CH 3 CH(CH 3)-Si(OR a)(OR b)(OR c), (CH 3) 2 Si(OR a)(OR b), (CH 3 CH 2) 2 Si(OR a)(OR b), (CH 3 CH 2 CH 2) 2 Si(OR a)(OR b), (CH 3 CH(CH 3)) 2 Si(OR a)(OR b), (CH 3) 3 Si(OR a), (CH 3 CH 2) 3 Si(OR a), (CH 3 CH 2 CH 2) 3 Si(OR a), (CH 3 CH(CH 3)) 3 Si(OR a), (CH 3)(CH 3 CH 2)Si(OR a)(OR b), (CH 3)(CH 3 CH 2 CH 2)Si(OR a)(OR b), (CH 3)(CH 3 CH(CH 3))Si(OR a)(OR b), (CH 3 CH 2)(CH 3 CH 2 CH 2)Si(OR a)(OR b), (CH 3 CH 2)(CH 3 CH(CH 3))Si(OR a)(OR b), (CH 3)(CH 3 CH 2) 2 Si(OR a), (CH 3)(CH 3 CH 2 CH 2) 2 Si(OR a), (CH 3)(CH 3 CH(CH 3)) 2 Si(OR a), (CH 3) 2 (CH 3 CH 2)Si(OR a), (CH 3) 2 (CH 3 CH 2 CH 2)Si(OR a), (CH 3) 2 (CH 3 CH(CH 3))Si(OR a), (CH 3 CH 2) 2 (CH 3 CH 2 CH 2)Si(OR a), (CH 3 CH 2) 2 (CH 3 CH(CH 3))Si(OR a), CH 3 -Si(OR a)Cl 2, CH 3 CH 2 -Si(OR a)(O 2 CR)(OR c), and CH 3 CH 2 CH 2 -Si(OR a)(NR 2)(OR c); and (ii) one or more long-chain organosilano groups independently selected from the group consisting of CH 3 (CH 2) 7 -Si(OR a)(OR b)(OR c), CH 3 (CH 2) 8 -Si(OR a)(OR b)(OR c), CH 3 (CH 2) 9 -Si(OR a)(OR b)(OR c), CH 3 (CH 2) 10 -Si(OR a)(OR b)(OR c), (CH 3 (CH 2) 7) 2 Si(OR a)(OR b), CH 3 (CH 2) 7 -Si(OR a)(OR b)(Cl), CH 3 (CH 2) 7 -Si(OR a)(OR b)(NHCH 3), CH 3 (CH 2) 7 -Si(OR a)(OR b)(O 2 CCH 3), and CH 3 (CH 2) n -Si(OR a)(OR b)(OR c);