For polymer nanocomposites, the small size of the fillers makes it difficult to analyze the degree of mixing quantitatively and often requires direct assessment via transmission electron microscopy (TEM). To date, qualitative comparisons and indirect measurements of the degree of mixing by measurement of certain properties are the most common methods. Better methods to quantitatively characterize the degree of mixing in nanocomposites would aid in studies investigating the effect of process conditions on the mixing behavior. Alumina/PET nanocomposites of identical composition, but with different degrees of mixing were prepared using a batch mixer. For evaluation of the degree of mixing with respect to both dispersion and distribution, three different techniques were applied and compared. TEM particle density was useful for dispersion, but did not adequately characterize distribution, while the Morisita's index gave poor results due to a wide range of effective particle sizes. Both methods ranked the samples differently compared to direct visual observation. In contrast, the skewness calculated by the quadrat method produced results consistent with visual rankings, and was found to be most effective in comparing and quantifying the degree of mixing. Although the quadrat method requires proper selection of quadrat size for a particular particle concentration, the skewness from the quadrat method was found to be most suitable as a standard index for the degree of mixing in nanocomposites. The usefulness of the quadrat method was verified using a second set of nanocomposites prepared by a twin screw extruder showing the potential for application of this technique for process development and quality control in commercial nanomanufacturing processes.

The direct assembly of polymer blends on chemically functionalized surfaces is shown to produce a variety of nonuniform complex patterns. This method provides a powerful tool for easily producing nonuniform patterns in a rapid (30 s), one‐step process with high specificity and selectivity for a variety of applications, such as nanolithography, polymeric optoelectronic devices, integrated circuits, and biosensors.

Directed assembly of polymer blends using chemically heterogeneous patterns during spincoating can be used to produce nanopatterned polymer structures. Well-ordered morphologies are obtained when the characteristic length of a polymer blend is commensurate with pattern periodicity. In this paper, spin-coating speed and solution concentration were used to control the characteristic length of a polystyrene (PS)/poly(acrylic acid) (PAA) blend. With increasing spin speed or reducing solution concentration, the characteristic length decreased. Critical spin speeds or solution concentrations that produced the required characteristic length commensurate with the given pattern periodicity were predicted. Well-ordered morphologies were obtained when spin speed or solution concentration was close to the critical value. A new method of image analysis was introduced to quantitatively evaluate the quality of replication of the underlying pattern. The range of commensurability between characteristic length and pattern periodicity for well-ordered morphologies was investigated. When the range of commensurability was within 20%, well-ordered morphologies were produced.

The use of microfeature-enabled devices, such as microfluidic platforms and anti-fouling surfaces, has grown in both potential and application in recent years. Injection molding is an attractive method of manufacturing these devices due to its excellent process throughput and commodity-priced raw materials. Still, the manufacture of micro-structured tooling remains a slow and expensive endeavor. This work investigated the feasibility of utilizing additive manufacturing, specifically a Digital Light Processing (DLP)-based inverted stereolithography process, to produce thermoset polymer-based tooling for micro injection molding. Inserts were created with an array of 100-μm wide micro-features, having different heights and thus aspect ratios. These inserts were molded with high flow polypropylene to investigate print process resolution capabilities, channel replication abilities, and insert wear and longevity. Samples were characterized using contact profilometry as well as optical and scanning electron microscopies. Overall, the inserts exhibited a maximum lifetime of 78 molding cycles and failed by cracking of the entire insert. Damage was observed for the higher aspect ratio features but not the lower aspect ratio features. The effect of the tool material on mold temperature distribution was modeled to analyze the impact of processing and mold design.

With production of nanocomposites, the product life cycle, including recycling, becomes critical.