Multi-layer thermoplastic films and bags configured to provide a perceivable color change upon being subjected to a strain and methods of making the same

A strained thermoplastic bag, comprising:

• a first wall and a second wall joined along a bottom edge, a first side edge, and an opposing second side edge, wherein each of the first wall and the second wall comprises:
• a transverse-direction strained multi-layer co-extruded film comprising a first thermoplastic film layer of a first thermoplastic material and a second thermoplastic film layer of the first thermoplastic material, wherein:
• the first thermoplastic film layer comprises a white color created by a first colorant and the second thermoplastic film layer comprises a black color created by a second colorant,
• the first and second thermoplastic film layers are co-extruded layers,
• the first thermoplastic material comprises linear low density polyethene (LLDPE);
• the transverse-direction strained multi-layer co-extruded film is devoid of voiding agents;
• and
• a plurality of raised rib-like elements formed in the first and second thermoplastic film layers about flat regions of the first and second thermoplastic film layers wherein the plurality of raised rib-like elements provide the strained thermoplastic bag with increased elasticity, wherein:
• a thickness of the first thermoplastic film layer comprising the white color comprises 40% of a thickness of the transverse-direction strained multi-layer co-extruded film;
• a thickness of the second thermoplastic film layer comprising the black color comprises 60% of the thickness of the transverse-direction strained multi-layer co-extruded film;
• a concentration by mass of the first colorant in the first thermoplastic film layer is between eight percent and ten percent;
• and
• the concentration by mass of the second colorant in the second thermoplastic film layer is between four and seven percent;
• the transverse-direction strained multi-layer co-extruded film has a color appearance that has a perceivable color change relative to a first color appearance when the plurality of raised rib-like elements are unstrained within a range of ΔE 3.0 and 7.00;
• the plurality of raised rib-like elements are strained in-plane with the flat regions by a strain applied subsequent to formation of the plurality of raised rib-like elements within a range of 40% to 60%.

A strained multi-layer thermoplastic bag comprising:

• a first wall and a second wall joined along a bottom edge, a first side edge, and an opposing second side edge, wherein each of the first wall and the second wall comprises a transverse-direction strained multi-layer co-extruded film comprising:
• a first thermoplastic film layer of a first thermoplastic material comprising a first pigment that provides the first thermoplastic film layer with a first white color and a second thermoplastic film layer of the first thermoplastic material comprising a second pigment that provides the second thermoplastic film layer with a second different black color, wherein:
• the first thermoplastic material comprises linear low density polyethene (LLDPE);
• the first pigment comprises TiO2 and wherein the second pigment comprises carbon black;
• the first and second thermoplastic film layers are co-extruded layers, the first and second thermoplastic film layers are devoid of voiding agents;
• and
• a plurality of raised rib-like elements formed in the first and second thermoplastic film layers about flat regions of the first and second thermoplastic film layers wherein the plurality of raised rib-like elements provide the strained multi-layer thermoplastic bag with increased elasticity, wherein:
• a thickness of the first thermoplastic film layer comprising the first white color comprises 40% of a thickness of a given wall of the transverse-direction strained multi-layer co-extruded film;
• a thickness of the second thermoplastic film layer comprising the second different black color comprises 60% of the thickness of the given wall of the transverse-direction strained multi-layer co-extruded film;
• a concentration by mass of the second pigment in the second thermoplastic film layer is between four percent and seven percent;
• a concentration by mass of the first pigment in the first thermoplastic film layer is between eight percent and ten percent;
• and
• the transverse-direction strained multi-layer co-extruded film has a color appearance that has a perceivable color change relative to a first color appearance when the plurality of raised rib-like elements are unstrained within a range of ΔE 3.0 and 7.00, wherein the plurality of raised rib-like elements are strained in-plane with the flat regions by a strain applied subsequent to formation of the plurality of raised rib-like elements within a range of 40% to 60%.