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Increased Melt Strength

U.S. Patent 8,987,382 (March 24, 2015), “High Melt Strength Polyethylene Compositions and Methods for Making the Same,” Mehmet Demirors, Teresa Karjala, and Nicolas Mazzola (Dow Global Technologies LLC, Midland, Michigan, USA).

Many polyethylene resins have low melt strength, limiting their processing window in applications such as blown films. Demirors, Karjala, and Mazzola increased the melt strength of a polyethylene resin by reacting the resin with a free radical generator, such as an alkoxy amine with a decomposition temperature of less than 250°C, through extrusion. The LLDPE samples showed increases in melt strength of 2-3 times the original melt strength by extrusion. To be effective, the polyethylene resin must contain more than 50 wt% ethylene units.

Foam-Toughened Concrete

U.S. Patent 8,987,356 (March 24, 2015), “Flexible Polymer Concrete and Methods for Making Flexible Polymer Concrete,” Shubel Hudson Owen (Quadroc, LLC, Marshfield, Wisconsin, USA).

Conventional concrete is inexpensive, moldable, and durable and has high compression strength. However, it also has low tensile strength with little ability to flex without cracking. 

Owen developed a toughened concrete by adding a paste consisting of Portland cement, a polymeric foam, aggregate, and water to a concrete mix. The result is a concrete with 0.0001-0.0005 inch (0.0025-0.0127 mm) diameter bubbles in polystyrene. The polymeric foam fills spaces in the concrete, enabling some reversible stress deformation without cracking. A portion of the cement paste of a conventional concrete (10-30 vol%) is replaced with an equal volume of foamed styrene/polystyrene resin. Polymerization is heat-initiated, and the Portland cement exothermic reaction accelerates curing.

The flexible polymer concrete shows increased tensile strength in all directions. Applications include railroad ties, roof tiles, bridge decks, highway pavement, concrete blocks, concrete pipe, and earthquake-resistant structures.

Polylactide-graft-Lignin Copolymers

U.S. Patent 8,993,705 (March 31, 2015), “Polylactide-Graft-Lignin Blends and Copolymers,” John R. Dorgan, Michael Paul Eyser, and Clay Perbix (Colorado, USA). 

As the biomass industry grows, lignin availability is increasing. The attractive features of lignin include its three-dimensional aromatic structure with many reactive functional groups for grafting. Lignin is the second-most abundant natural biopolymer following cellulose, and easily the least-used despite its great potential as a filler and a thermal modifier. Meanwhile, polylactic acid (PLA) is an aliphatic renewable thermoplastic that is readily biodegradable, but it’s limited by a low glass transition temperature and a low heat distortion temperature.

Dorgan, Eyser, and Perbix produced useable PLA-graft-lignin copolymers. They found that all of the different lignins from biomass refining are soluble in lactic acid. Polylactide-graft-lignin blends are produced by butyrating a lignin and heating a PLA/butyrated lignin mixture from 160 to 190°C. They were also able to polymerize a lactide suspension of dried lignin to produce grafted copolymers. These copolymers make useful rubber reinforcers, panelboard adhesives, friction materials, and insulation.

Self-Reinforced Composites 

U.S. Patent 8,992,812 (March 31, 2015), “Self-Reinforced Composite Made of Recycled Materials and Process of Making the Same,” Fu-Jya Daniel Tsai (Alpharetta, Georgia, USA).

Pressures are growing to reduce landfill waste from the carpet and automotive industries. Thirteen percent of the municipal solid waste generated in the USA (over 245 million tons) includes plastics, rubber, carpets and textiles. At present, only about 6% of plastics, 19% of rubber, and 1% of carpets are recovered for recycling. The remaining is either landfilled or incinerated for energy recovery. Most synthetic polymer wastes consist of many different immiscible polymers. Recycling is difficult and expensive because of the need for sorting.

Tsai developed a self-reinforced composite from recycled plastics. Wastes from collection sites are cut, shredded, and sent without further sorting to a vented extruder, where the material is filtered and sent to a melt spinning line. The material is spun into a continuous fiber by phase-migration spinning. The result is core-shell fibers with high-melting temperature cores coated with low-melting temperature shells. The fibers are stretched and arranged into a mat, then thermoformed or compression molded into a fiber-reinforced material. The elimination of the complicated sorting and separation steps makes recycling more competitive. 

Melt Homogeneity

U.S. Patent 8,992,069 (March 31, 2015), “Plasticizing System Including Opposite-Facing Surfaces for Contacting Opposite Sides of Solidified-Resin Particle,” Manon Danielle Belzile (Husky Injection Molding Systems Ltd., Bolton, Ontario, Canada).

Extruders and injection molding screws melt, convey, and pressurize molten resin. However, the quality of the melt varies from shot to shot, and thermal homogeneity of the melt is difficult to achieve. In order to fully melt all of the plastic, residence times often need to be long, leading to degraded resin.

Belzile developed a plasticizing system based on a tapered tube with an internal barrier. The partially melted stream enters the plasticizing tube and is pushed though the tube with a plunger. The purpose of the system is to minimize energy and residence time, since pellets and melt are distributed evenly, and conduction, pressure, and drag are controlled at all times.

Heat Stabilizers

U.S. Patent 9,018,292 (April 28, 2015), “Heat-Stabilized Polyamide Composition,” Stéphane Jeol, Thierry Badel, Hae-Young Kim, and Franco Speroni (Rhodia Operations, Aubervilliers, France).

Polyamide is a synthetic high-performance polymer, but it is heat sensitive. This instability is reflected by reduced mechanical properties and color changes. This is particularly important for automotive engine applications. Heat stabilizers are used but there is a need for less expensive, more effective stabilizers.

Jeol et al. developed an alcohol stabilizer that is excellent in maintaining mechanical properties during heating. The alcohols have 3 to 8 hydroxyl groups along with other functional groups and do not require other heat stabilizers (examples are dipentaerythritol or tripentaerythritol). There seems to be a synergism between the alcohol and impact modifiers for the retention of tensile and impact properties during thermal aging in air.

Blow-Molded Sheds

U.S. Patent 9,016,003 (April 28, 2015), “Modular Blow Molded Shed with Connectors,” Michael Thuma, Torrence Anderson, and Michael R. Vogler (Suncast Technologies, LLC, Palm Beach Gardens, Florida, USA).

Utility sheds are needed for lawn and garden care and home storage space. However, blow-molded plastic components typically cannot be formed with the intricate shapes and sharp corners required for stable structures.

Thuma, Anderson, and Vogler developed a system of blow-molded panels having integrally formed connectors which can be linked together to form a shed. The wall panels have locking plugs that fit into corresponding sockets, rigidly connecting the components together. The connector sections are based on the I-beam design.

Blow molding the wall panels allows them to be formed with adequate height for a large walk-in enclosure, eliminating the need for stacking panels. The panels are blow-molded polystyrene, polypropylene, or polyethylene. In addition, the panels are strengthened with injection-molded connectors and a steel truss supporting the roof panels.