I've try this:
newmtl TapaPlastico
illum 1
Ka 0.627451 0.321569 0.176471
Kd 0.627451 0.321569 0.176471
Ks 0.627451 0.321569 0.176471
Ns 1.0
Tf 0.627451 0.321569 0.176471
Ni 10.0
d 0.7

without the "map_Kd Dual1214V2_TapaPlastico.png".
Is not need wile this is a transparent material.
You could try different value for d (transparency).
or this
newmtl TapaPlastico
illum 1
Ka 0.2 0.2 0.2
Kd 0.5 0.7 0.8
Ks 0.0 0.0 0.0
Ns 1.0
d 0.4

Hope it help!