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Heat-Accumulating Polyamides

U.S. Patent 8,957,133 (February 17, 2015), “Polyamide Moldings Comprising Microencapsulated Latent-Heat- Accumulator Material,” Philippe Desbois, Tina Schroder-Grimonpont, Stephan Altmann, and Marco Schmidt (BASF SE, Ludwigshafen, Germany).

Cast polyamide moldings are based on alkaline rapid polymerization in a mold involving anionic polymerization of lactams. An advantage of this process is a single step from the monomer to the finished product. Starting with fluid monomers also enables high filler contents difficult to reach by other methods. These rigid moldings are used to replace metals. However, they have a low heat capacity compared to metals, leading to higher temperatures during use and increased thermal degradation.

Desbois et al. developed cast polyamide moldings containing microcapsules of a latent-heat-accumulator material. These accumulators are phase-change materials where the solid/liquid phase transition absorbs heat at constant temperature, later leading to slow heat dissipation. Thus, they can keep temperatures within a defined range. Suitable heat accumulators are aliphatic hydrocarbons, such as linear saturated or unsaturated C₁₀-C₄₀ hydrocarbons. These materials can be used in battery housings, electronic housings, and food packaging.

Toughened Poly(arylene ether)

U.S. Patent 8,957,143 (February 17, 2015), “Impact-Resistant Poly(arylene ether) Resins with Improved Clarity,” Kim G. Balfour (SABIC Global Technologies B.V., Netherlands).

Even though additives improve the properties of poly(arylene ether) materials—such as light colors, low haze, and flame-retardance—other problems remain. Optical-enhancing agents, along with flame-retardants, can give resins improved clarity and flame resistance, but they also reduce toughness. There is therefore a need in the packaging and healthcare industries for poly(arylene ether) materials with an improved balance of optical clarity and impact resistance. 

Balfour developed toughened poly(arylene ether) with improved transparency by adding radial and linear styrene-diene block copolymers, one or more optical enhancing agents such as alpha hydroxyl ketones, a hydrocarbon flow promoter, cyclopentene, and other additives. This material has a multi-axial impact toughness of at least 20 joules, a haze of 15% or less, and transmittance of 75% or more.

Grafted Nanoparticles

U.S. Patent 8,945,673 (February 3, 2015), “ Nanoparticles with Grafted Organic Molecules,” Lorenzo Mangolini, Uwe Kortshagen, Rebecca J. Anthony, David Jurbergs, Xuegeng Li, and Elena Rogojina (Univ. of Minnesota, Minneapolis, Minnesota, and Innovalight, Inc., Sunnyvale, California, USA).

Semiconductor nanoparticles are being used in the fabrication of nanostructured electronic devices. In many instances, grafting of molecules to nanoparticles is needed to fine-tune the most critical properties. The usual thermal grafting of these particles, while avoiding agglomeration, is limited to small particle concentrations, severely limiting its application.

Mangolini et al. improved passivation efficiency by grafting Group IV nanoparticles in the gas phase flowing through specially designed plasma chambers. The plasma causes the organic molecules to break into active groups which bond to the suspended nanoparticles. The nanoparticles are activated in the first plasma chamber and grafted in a second plasma chamber without agglomeration in milliseconds, compared to minutes and hours by the conventional grafting method.

High-Temperature Gaskets

U.S. Patent 8,940,841 (January 27, 2015), “Polyarylene Compositions, Methods of Manufacture, and Articles thereof,” Ping Duan, Gaurav Agrawal, and David P. Gerrard (Baker Hughes Incorporated, Houston, Texas, USA).

In down-hole oil drilling and oil wells, elastomer gaskets are used in applications such as packer elements, blow-out preventer elements, O-rings, and gaskets. These elastomers are exposed to high temperatures and harsh chemical and mechanical environments that degrade performance and reliability.

Duan, Agrawal, and Gerrard developed a crosslinked polyarylene with high-temperature elastomeric properties and excellent chemical resistance. The polyarylene consists of aromatic hydrocarbon rings with functional groups for crosslinking. The new elastomers have a glass transition above room temperature, but lower than the minimum application temperature. The crosslinked materials are useful in oil and gas downhole applications in the form of either solids or foams. The crosslinked polyarylenes are prepared by oxidative crosslinking in the presence of a molecular crosslinking agent.

Fabricating Composites

U.S. Patent 8,951,375 (February 10, 2015), “Methods and Systems for Co-Bonding or Co-Curing Composite Parts using a Rigid/Malleable SMP Apparatus,” David E. Havens, Matthew C. Everhart, Randy Kysar, Carl Ray Fiegenbaum, Jeffrey W. Priest, Delbert Leon Strelow, Kevin John Ford, and Kristin Dru Pickell (Spirit AeroSystems, Inc., Wichita, Kansas, USA).

Composite parts, such as those in aircraft, are constructed using various production methods such as filament winding, tape placement, overbraiding, chopped fiber roving, coating, or hand lay-up based on rigid tooling. Removing the tool or mandrel from the cured part after curing is difficult, costly, and time-consuming. There is a need for improved methods for separating cured parts from the tooling.

Havens et al. developed a method and apparatus for fabricating a composite part with shape memory polymer (SMP) tooling. The SMP structure is shaped, heated, and then attached to a rigid tool. During composite molding, the assembly is heated and cured. When the composite is cured and cooled, the SMP part of the tooling shrinks away from the cured composite material, facilitating removal.

This shape memory material may be an epoxy, a styrene copolymer, cyanate ester, polyurethane, polyethylene, styrene-butadiene copolymer, polyisoprene, acrylic and norbornene copolymer, napthalene polymer, or malemide.

Crosslinking Analysis

U.S. Patent 8,950,267 (February 10, 2015), “Methods and Apparatus for Detecting Cross-Linking in a Polymer,” Dan Doble, Rafal Mickiewicz, John Lloyd, Marco Jaeger, and William F. Hartman (Fraunhofer USA, Inc., Plymouth, Michigan, USA).

Direct conversion of solar energy to electrical energy can provide a virtually unlimited source of clean energy. Conventional photovoltaic (PV) modules typically include a stack of materials encapsulated in a transparent copolymer such as ethylene vinyl acetate (EVA). During lamination, EVA is applied to a photovoltaic module and cured and crosslinked to prevent long-term creep due to temperature and stress. The crosslinking is critical to long-term performance and must be monitored. Conventional crosslinking measurements are the gel fraction test and creep test, requiring destruction of the tested material. An automated, nondestructive test is badly needed.

Doble et al. measured cross-linking by localized deformation without damage to the PV module. A polymer sample is indented and the relaxation or a recovery recorded. This recovery is then compared to a reference material. An automated test for crosslinking could be a major step in quality control as well as for monitoring long-term performance.

Flow Enhancement

U.S. Patent 8,946,332 (February 3, 2015), “Flow Enhanced Thermoplastic Compositions and Methods for Enhancing the Flow of Thermoplastic Compositions,” Josephus Gerardus van Gisbergen, Chris van der Weele, Sreepadaraj Karanam, and Mark van der Mee (SABIC Global Technologies B.V., Netherlands).

For electrical applications, thermoplastic polymer composites need to meet specific flame retardance requirements requiring flame retardants. However, these flame retardants lead to poor flow, making fabrication difficult.

Van Gisbergen et al. developed a composite containing 30 to 95 wt% thermoplastics and an effective amount of a flow-enhancing component. The flow enhancement reduces the composite viscosity by at least 10%. The thermoplastics can be polycarbonates or polyesters. The flow-enhancing additive consists of metal oxides, with a mineral filler. The weight ratio of the two ranges from 1:25 to 25:1. One example composite consists of (1) 20 to 50 wt% bisphenol-A polycarbonate resin, (2) 10 to 45 wt% polybutylene terephthalate, (3) 3 to 20 wt% mineral filler, (4) 3 to 15 wt% core-shell impact modifier, (5) 5 to 30 wt% brominated polymer, (6) 1 to 10 wt% antimony oxide, and (7) 0 to 5 wt% polytetrafluoroethylene.

Nanoparticle Heat Transfer

U.S. Patent 8,945,687 (February 3, 2015), “Heat Transfer Medium and Heat Transfer Method using the same,” Seonmi Yoon, Jaeyoung Choi, Hyeon Jin Shin, Jeong Gun Lee, and Jongmyeon Park (Samsung Electronics Co., Ltd., South Korea).

A film or coating formed on a glass or plastic substrate is crosslinked, ordered, plasticized, or crystallized by the application of heat. This heat can be substantial, leading to fracture or deformation of the substrate. For example, titanium oxide (TiO₂) can form a transparent porous electrode for a photovoltaic (PV) cell. However, it must be sintered at 470°C, which is impossible for most plastic and glass substrates to resist.

Yoon et al. developed a heat transfer medium consisting of a light-transparent substrate coated with nanoparticles. The nanoparticles absorb incident light, producing heat, which is then transferred to the target. After heating, the particles can be removed by etching. The nanoparticles localize heating to selective portions of the target. Candidate nanoparticles include Au, Cu, Ag, Ti, Al, Pd, Pt, Rh, Ir, Fe, W, or Ni particles. Such a heat-transfer medium can even be used to anneal an organic film on a plastic.

Effective particle absorption depends on particle size and radiation wavelength. The gold nanoparticles in one example have a diameter of 10 nm and a length of 60 nm with a maximum absorbance at 800 nm radiation.