ADDITIVES | COMPATIBILISERS
produce cooking oil. The new, experimental titanate is expected to function similarly, although it is a different molecule. Another titanate additive can be used to copolymerise PVC with other polymers. “The titanium catalysis effect of increasing polymer flow at lower temperatures allows for a wider range of plastics to be copolymerised, such as PVC with PC,” said Monte. The additive can also be used to copolymerise PVC with PE, nitrile rubber, and vinyl chloride-acrylonitrile copolymer for injection moulded, high-strength and large-size automotive interior trim parts. Kenrich is using its Ken-React coupling agent to
treat a sodium bicarbonate foaming agent to mimic the behaviour of azodicarbonamide as to the temperature and time duration of carbon dioxide release, resulting in improved foaming properties in thermoplastics such as LLDPE and PVC. The treated foaming agent is being evaluated as a functional substitute to azodicarbonamide foaming agents, which have been labeled as substances of very high concern in the EU.
Graphene work Kenrich coupling agents are also being evaluated with graphene, which is a nano-scale, two-dimen- sional additive that is seeing increased use for enhancing properties in thermoplastics. Challeng- es with graphene, however, are that it needs to be exfoliated in the finished product to deliver performance. In general, nano-particles agglomer- ate, and mechanical shear energy alone in the poly- mer melt is not sufficient to obtain complete exfoliation, said Monte. Coupling agents are often used to help solve problems of agglomeration and dispersion.
Another challenge is that the graphene surface is non-reactive with silanes, which means the
surface must be treated before it can be functional- ised with silane-based coupling agents. Unlike silanes, however, the 1.5 nm titanates and zirco- nates from Kenrich form atomic monolayers on the carbon surface via proton coordination, in situ, helping exfoliation and preventing reagglomera- tion, said Monte. “Reagglomeration is prevented by the interfacial
organometallic monolayers,” he explained. In addition, the titanate or zirconate reacts with the polymer phase, forming covalent bonds between the graphene and the polymer, which allows stress transfer over the graphene-polymer interface, to improve impact strength and flexibility. Monte said that the bond has been shown to have long-term strength in aging tests.
“So much know-how goes into using this technology properly,” he said. There are different methods for appropriately coupling in situ, depending on the formulation of the compound, the polymer type, the equipment used, and other variables. Once the right level and processing conditions are identified for a given situation, the additive will perform, he said. “I predict that titanates and zirconates will be for graphene composites what silanes are for fiberglass compos- ites,” he concluded.
PLA and rPET There is a need for bio-based and biodegradable additives for compounds with PLA or PLA-blends, said Tom Inch, Market Manager for Thermoplastic Additives at BYK USA, in a presentation at AMI’s Compounding World Expo in Cleveland, US, in November 2023. PLA (and other bio-based and biodegradable plastics) are expected to grow in use, and PLA needs additives to enhance its melt strength for plastics conversion processes and its flexibility and impact strength for end-use applications.
In a mixture of a small amount of polymer in a non-polar matrix, a compatibiliser increases interfacial adhesion between the non-polar matrix and the polar phase, reduces the particle size of the polar phase, and increases uniformity. Source: Ingenia Polymers.
62 COMPOUNDING WORLD | May 2024
www.compoundingworld.com
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