TECHNOLOGY | FUNCTIONAL FILLERS


Above: Imerys is using talc to compatibilise PE and PP to simplify


post-consumer recycling


our customers - and the industry at large - with superior, sustainable performance at the right cost.” Anaïs Berjeaud, Development Manager Plastics &


Rubber at the company, says that recycling plastics is one obvious way of going more sustainable. “The current challenge is to ensure that mechanical properties, which tend to deteriorate during the recycling process, are maintained or even enhanced to enable them to meet ever more stringent specifications and remain cost-effective,” she says.


Talc compatibilisers Talcs and carbonates can be added to recycled plastic compounds to restore mechanical perfor- mance, but a few years ago Imerys developed a mineral-based compatibiliser, ImerLink, to create effective links between the components of blends of polyethylene and polypropylene – which are normally mutually incompatible – through a reactive process. “This results in a fully compatibi- lised material having improved mechanical properties with an optimum stiffness/toughness balance,” she says. PE and PP are normally compatibilised using interfacial agents such as olefin block copolymers (OBCs), but Imerys says the resulting material still has two clearly visible phases and that this shows that the blend is not fully compatibilised. OBCs can also be quite expensive. ImerLink has been shown to be more effective because it not only changes the miscibility of the PE and PP phases but also creates a new network of bonds between the phases and the coated mineral. At another talc supplier, IMI Fabi, Product and


Application Development specialist Piergiovanni Ercoli Malacari says the company has achieved some significant developments in a variety of plastics applications. Special talc grades such as its


32 COMPOUNDING WORLD | June 2020


highly engineered HVTextra and its HVTultraC ultrafine grades are intended to support automo- tive lightweighting applications. “In particular, solutions for downgauging are available where thinner parts are designed, as well as solutions engineered to reduce the specific gravity in the finished parts, allowing a reduced mineral loading rate, preserving the original mechanical perfor- mances,” he says. “Another important field where talc can be actively used in weight reduction is for foamed applications. Talc NSultraC works perfectly to nucleate bubbles in foamed moulded parts granting precise bubble size and distribution for superior mechanical properties, preserving aesthetic properties, and offering the opportunity to produce foamed parts also for visible compo- nents,” says Malacari. Due to talc’s plate-like shape, highly micronised


grades show a relatively high volume in loose powder form. Malacari says IMI Fabi has been working on compaction technologies to reduce the volume of such fluffy powders for easier and more efficient handling. He says the company has been able to engineer a special free-flowing and dust-free grade, HTP1s, which can be used for multiple purposes. These include use as a carrier for costly chemicals, such as stabilisers, in additive pre-mixes. The spherical agglomerate is said to preserve the mix flowability for a precise additive dosing. “Because of its high degree of fineness and its high purity, talc HTP1s is a perfect additive for several applications including crystal growth nucleation and polyethylene antiblocking,” he says. The same compaction technology is also used for NoBlock-S, a recently-developed additive employed in LLDPE films. Malacari says the grade offers high antiblocking efficiency at low loading for extremely high transparency, together with free flowing and dust free features.


Filling bioplastics Any discussion of sustainability inevitably leads to biopolymers. Demand for bio-based and/or biodegradable plastics is rising but these materials provide a large variety of new challenges, with mechanical properties and thermal resistance often lower than standard thermoplastics and processing windows frequently narrower. “Talc [hydrated magnesium silicate] is a natural


mineral; it is inert, food contact approved and does not impede material recyclability, making it an ideal reinforcing agent for bioplastics,” says Cyril Coppel, Marketing Manager – Plastics, EMEA, at Imerys. “Imerys talcs such as HAR (High Aspect Ratio) and


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