A study conducted by TOPAS Advanced Polymers reveals that discrete layers of cyclic olefin copolymer (COC) provide significant performance enhancements in three- and five-layer packaging film structures made of linear low-density polyethylene (LLDPE). The findings were recently presented by Paul Tatarka, Market Development Manager for TOPAS Advanced Polymers, at the SPE ANTEC 2017 technical conference in Anaheim, CA.
Via design of experiments (DOE) methods, TOPAS researchers demonstrated that COC provides greater than expected toughness, strength, stiffness, and appearance (low haze) in multilayer packaging structures made of LLDPE.
“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,” explained Tatarka. His full presentation can be found online at https://topas.com/tech-center/presentations.
The TOPAS team studied glass transition temperature, COC modification, and blow-up ratio 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 scientists found 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. It also more than doubled secant modulus—a stiffness measure.
Addition of at least one discrete layer of amorphous COC modestly improves impact resistance. Films made with 65⁰C Tg COC modified with TOPAS E-140 have impact resistance nearly 20% greater than that of the LLDPE control film and close to the average for heavier gauge LDPE/LLDPE generic film. Tear resistance was also significantly reduced while tensile properties were substantially improved. Splitting COC into two layers reduces 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.
Cyclic olefin copolymers have become a highly valuable component in numerous packaging applications globally. These include 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.
The TOPAS group’s examination of tensile properties, impact resistance, tear strength, and optics as a function of blow-up ratio, COC Tg, and COC modification provides packaging designers and film manufacturers useful information to improve packaging performance. The study reveals an exceptional balance of properties that can be easily tailored and optimized to the specific requirements of many applications.
TOPAS Advanced Polymers expects to see further property enhancements with the use of COC in multilayer films and will continue to evaluate its potential in future studies.