masterbatch feature | Carrier materials Exilica’s
micron-sized porous
particles can absorb and then slowly
release a range of chemicals
degradation can decrease organoleptic properties, notes the company. The method is also useful for achieving very high concentrations of liquid flame retardants. Frilvam is using the Prisma Absorber in its own
masterbatch production, but will also supply the carrier to other masterbatch producers. The product line currently includes LDPE, EVA and PP versions. Exilica is a UK company that produces porous,
micron-sized, spherical particles composed of poly(1- methylpyrrol-2-ylsquarine) (PMPS). These can absorb and then slowly release a wide range of chemical species, including polymer additives such as fragranc- es, lubricants, antibacterials and insect-repellents. PMPS particles can be compounded into polymers at
The tubular structure of Applied Minerals’ Dragonite allows it to carry additives
C (Compounding World, September 2011, page 57). The particles are compatible with many polymers, including polyolefins as well as PVC, nylons and PET. New application areas include floor coverings, wall panelling, textile fibres, and consumer product packaging like bottles and caps, says Daniel Lynch, technical director at Exilica. Applied Minerals’ Dragonite halloysite is a natural, aluminosilicate clay with a hollow, tubular morphology that can be used, among many things, as an adsorbent and carrier of polymer additives. The particles are 1-2 microns long and 50 nm across, with a 15-nm diameter hole in the centre of the tube and a very high surface area of 65-120 m2
levels up to 4% without affecting polymer properties, and typical loading levels are 0.6-1.5%, says the company. Exilica has focused on using the particles to make fine-fragrance masterbatches, because in this market it offers the key benefit of protecting the fragrance through processing temperatures of up to 280o
/g.
One potential application is as a carrier for antioxi- dants. “Much of the antioxidant that should go into protecting a polymer is lost to migration,” explains Chris DeArmitt, CTO of Applied Minerals. “Adding
halloysite loaded with antioxidant to the formulation allows it to release slowly and protect the polymer from degradation at much lower use levels. While the possibility of slow-release of antioxidant has been known for some time, it is now beginning to be scaled- up and proven in polymer systems.” A carrier application that is now being used com-
mercially is loading chemical blowing agents into halloysite tubes. Because the blowing agent is being released from the very small tubes, it creates small bubbles. In addition, while foaming generally reduces strength and modulus, Dragonite in the formulation increases the strength and modulus of the end part. Masterbatch supplier KibbeChem found that master- batches with Dragonite resulted in 30% higher extruder throughput, better physical properties, and smaller bubbles for an improved surface finish. Another commercial application is loading the tubes, which themselves act as both a mineral flame retardant and a reinforcing agent, with a liquid flame retardant. For example, a customer needed to add flame retar- dancy to a high-end, glass-reinforced PET pallet application, but existing phosphorous-based systems plasticized the formulation and decreased the modulus to an unacceptable level, DeArmitt explained in a presentation at the recent AMI Fire Retardants in Plastics conference. A solution was found by loading Dragonite with a
non-halogenated, oligomeric phosphate ester flame retardant, resorcinol bis-diphenylphosphate (RDP). Absorbing RDP in the halloysite tubes created a slow release that prevented premature blooming. The combination of flame retardancy of the halloysite and that of 2% RDP is expected to meet the UL 2335 requirement.
In addition, the high aspect ratio halloysite acted as a reinforcing agent to replace a portion of the glass fibre
22 COMPOUNDING WORLD | August 2012
www.compoundingworld.com
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