Hybrid’s Work With POSS in Fillers Featured in Compounding World Magazine
The below article about Hybrid’s POSS fillers, written by Mark Holmes, is featured in the August edition of Compounding World magazine. You can access the original article in its entirety by clicking here. To access the Compounding World Web site, click here.
…New treatment technologies are also being developed that allow existing fillers to deliver improved functionality. One company working in this area is Hybrid Plastics – the developer of POSS additives. “The trend is for multifunctional fillers that, in addition to providing filler effects such as reinforcement, adding volume and providing cost reductions, can also provide other enhancements including dispersion, fire retardancy, clarity and anti-scratch effects,” said Joe Lichtenhan, the company’s President. “Multifunctionality can simplify formulations, reduce formulation SKU count, and provide differentiation in the market place.”
Hybrid Plastics says that POSS – Polyhedral Oligomeric Silsesquioxane – is a nanostructure product that bridges the gap between ceramic and organic materials. POSS can improve product performance without sacrificing mechanical properties and is used in a range of industries. The company adds that POSS technology is derived from a continually evolving class of compounds closely related to silicones through both composition and a shared system of nomenclature.
POSS chemical technology has two specific features. Firstly, a chemical composition that is a hybrid, intermediate [RSiO1.5] between that of silica [SiO2] and silicone [R2SiO]. Secondly, POSS molecules are physically large with respect to polymer dimensions and nearly equivalent in size to most polymer segments and coils.
“POSS silanols – SO1458, SO1450 and SO1455 – are our primary surface treatment products,” explains Lichtenhan. “For thermoplastics, the POSS is compounded into a resin at the feeder throat with pellets, while the filler is b-staged. However, for pre-treatment of powders POSS is dissolved in solvent and/or sprayed onto powders and tumble mixed. Silanols are chemically unique and a bit rare, but POSS silanols are chemically stable. Silanols react to surfaces in a similar fashion to coupling agents. The POSS silanols bind to polar surfaces of powders or key ingredients and ultimately form a Si-O-Metal bond on the surface. No ethanol, methanol, or acetate is eliminated, with the reaction from Si-O-H to Si-O-M being thermodynamically driven which is favorable.”
Hybrid Plastics says that a wide range of fillers, such as metals, metal oxides, minerals, colourants, pigments and key ingredients containing polar groups, are suitable for treatment with POSS. Amine function POSS – AM0265 and AM0281 – are claimed to be effective for carbon-based fillers. “Improvements with POSS include a more effective use of the filler at lower loadings. This applies to reinforcing fillers and colorant. Hence, savings are realized by using less filler through the dispersion of the filler with POSS. It can also aid gloss and color intensity,” Lichtenhan adds. “Most customers also see a decrease in viscosity through the use of POSS dispersion agents. Filler loading and viscosity increases nearly go hand in hand. The use of POSS often breaks this paradigm. These improvements can be achieved because POSS forms cages that control the surface area and volume around particles. This affords enhanced dispersion, viscosity reduction at high filler loadings and more effective use of filler. Dispersion of fillers through the use of surface area and volume modification additives like POSS is new.”
Hybrid Plastics highlights a number of new capabilities for fillers for using POSS additives. Traditional coupling agents and surfactants do not control the surface area around a particle. They do provide a more compatible interface. POSS cages do not polymerize on the particle surface and the cages are rigid and contain compatibilizing organic groups. These cages dominate the surface area of the particle because they are rigid and around 1.5nm in diameter. Similarly, volume control around a particle is critical to controlling the viscosity of high solids and suspension stability. POSS cages provide volume around the particle and this allows flow and movement of the particles by each other resulting in lower viscosity. Similar viscosity reductions can be achieved by spherical particles, but it is more expensive to manufacture these. POSS can also bridge the gap between inorganic and organic materials. The hybrid organic-inorganic composition of POSS provides a technical inter-phase transition between a rigid/hard inorganic filler and the softer organic resin material.”
As an example of what is possible with POSS, Hybrid Plastics has been working with The Resin Enterprise Inc. on a new application on filled Temppeclear compounds. “We are adding flame retardants, glass fibre, carbon fibre, PTFE and impact modifiers in various combinations and/or singularly to a base resin of polyphenylene ether (PPE),” says Linda Marlin, President of the Resin Enterprise. “The addition of POSS has improved the material’s processing, physical properties and color. This material can now compete in the market place with Radel products, as well as polysulfone and PEI. Right now the industry is starved for alternatives to PEI and polysulfone because of a market shortage of these materials. PPE is normally alloyed with polystyrene which makes the base resin processable, but it also reduces some of its high temperature and chemical resistance capabilities. With the deletion of the polystyrene and the addition of POSS, many new opportunities for Temppeclear are emerging. The addition of POSS to PPE also enables the resin to become amber clear and we are continuing to develop methods to improve the translucency of this material to a window clear tint. Some of the markets we are working on include automotive, laboratory, food products and plumbing.”