COC Boosts Performance in Multilayer LLDPE Packaging

Discrete layers of cyclic olefin copolymer (COC) were found to provide significant performance enhancements in three- and five-layer LLDPE packaging film structures.  The findings of the study conducted by TOPAS Advanced Polymers, Florence, Ky. were recently presented by market development manager Paul Tatarka at the SPE ANTEC 2017 technical conference in Anaheim, Calif.

TOPAS Advanced Polymers, Inc. researchers demonstrated, via design of experiments (DOE) methods, that COC provides greater than expected toughness, strength, stiffness, and appearance (low haze) in multilayer packaging structures made of LLDPE. Said Tatarka, “We found that by splitting COC into at least two layers in five-layer structures, further significant property enhancements are possible without changing COC content.”

To quantify how COC influences the performance of several key blown film properties in three-layer (90-micron thick) and five-layer (152-micron thick) structures, the TOPAS team studied glass transition temperature (Tg), COC modification, and blowup ratio. Results showed that the addition of one or more discrete layers of amorphous COC to LLDPE-based blown film significantly reduced total haze, including its internal and especially surface haze components. Moreover, stiffness measure secant modulus was more than doubled.

The addition of at least one discrete layer of amorphous COC modestly improved impact resistance. Films made with 65 C/149 F  Tg COC modified with TOPAS E-140 were shown to have a nearly 20% greater impact resistance than that of the LLDPE control film and close to the average for heavier gauge LDPE/LLDPE generic film. Moreover, tear resistance was significantly reduced while tensile properties were substantially improved. Splitting COC into two layers was shown to reduce loss in PE tensile strength, elongation, and impact resistance. Splitting COC into more than two layers will likely reduce this loss further, enabling efficient use of COC for all packaging film applications.

Thus far, COC has been proven to be a valuable component in numerous packaging applications. Included are soft shrink, sustainability-promoting TD and MD shrink labels, easy-tear pouches, flexible and rigid thermoformed trays, twist wrap, protective packaging, and heat seal and barrier films.

TOPAS’ examination of tensile properties, impact resistance, tear strength, and optics as a function of blow-up ratio, COC Tg and COC modification reportedly provides packaging designers and film manufacturers useful information to improve packaging performance. Study findings show an exceptional balance of properties that can be easily tailored and optimized to the specific requirements of many applications.