Lloyd A. Goettler

Film Blowing of Layered Silicate Nanocomposites

ABSTRACT Bubble formation and stability in the film blowing processing of in situ polymerized and melt-compounded polyamide 6-based layered silicate nanocomposites (LSNs) are correlated to their underlying rheology, structure, and crystallization behavior. The layered silicates enhance melt elasticity, induce γ -form crystallinity, and increase crystallization rates without having any significant effect on the extent of crystallinity. A bubble stability quantification method employed to assess the level of instability during the film blowing process finds the in situ polymerized LSNs to be more stable than PA6, while melt-compounded LSNs do not display such an improved processability. All of the LSN films produced by film blowing possess superior mechanical properties compared to neat nylon 6, despite their relatively rougher film surfaces.

Multiscale Reinforcement of Polymers Combining Cellulosic Wood Pulp with Layered Silicate Nanoplatelets

Synergies resulting from the combination of discontinuous reinforcing elements at two different size scales are examined in two polymer types — rubbery matrices comprising acrylonitrile-co-butadiene (NBR) elastomer and a high density polyethylene plastic. The latter is derived from a recycled post-consumer waste stream that is upgraded by the reinforcement to compensate for any degradation experienced during prior use or impurities introduced during recycling. The two reinforcements are wood pulp at the microscale and exfoliating layered silicate clays at the nanoscale. Appropriate compatibilizing agents are employed to allow wetting of the reinforcement with the polymer matrix, promote dispersion and provide a strong interface. In general, the microscale elements provide mechanical strengthening in tension, while the nanoscale reinforcements enhance stiffening and reduce failure propagation by tearing. The use of natural reinforcements and recycled feedstocks imparts environmental acceptability to such formulations.

Processing Characteristics of Layered Silicate Nanocomposites With Application to Blown Film

The aim of this study is to investigate the film blowing processing of various polyamide 6-based layered silicate nanocomposites (LSN’s) and to correlate their processing behaviors to the underlying rheology and structure. In-situ polymerized nanocomposites were found to possess a wider processing window compared to the base PA6. Shear and dynamic rheological measurements were employed to correlate the rheological behavior of the nanocomposites to the bubble formation and stability in the film blowing process. The in-situ plymerized LSN melts having higher elastic modulus (G′) were found to perform better in the film blowing process. DSC measurements indicated that nanoclays induce the γ type of crystallinity, which may also play a role in film blowing behavior.Copyright