MATERIALS | BIOPLASTICS
Graphs show the effect of Imerys Steamic and HAR talc filler in PLA on flexural modulus and heat distortion temperature
Source: Imerys
perspective. Recycling or composting is this advantage for many applications.” Nevertheless, requirements for bio-based plastics
are largely comparable to those for petroleum- based plastics. “For example, tighter spatial condi- tions require higher heat resistance,” says Sebö. “Thinner-walled components require improved rigidity and higher strengths are required to replace metal components. The required property profiles can often not be met by biopolymers alone.” HPF Minerals has developed a range of short- and long-needle, as well as coated, Tremin wollas- tonite functional fillers designed for use in a wide variety of biopolymers. “Freedom from distortion and high impact strength are required,” Sebö says. “With long-needle properties, higher stiffness can be achieved. The proportion of these fillers in PLA compounds can be 20-40% by weight, for example.” He says bioplastics reinforced in this way offer a multitude of possibilities in a wide variety of applications. “Wollastonite-reinforced PLA com- pounds can provide a number of properties, such as excellent rigidity, high dimensional stability (short-needle) and improved impact strength. We are also developing fillers for bioplastics that can also be used for additive manufacturing or auto- motive applications to meet the requirements that up to now have been restricted to synthetic polymers.” Imerys is also supplying fillers for bioplastic compounds and reports demand for bio-based and biodegradable materials is constantly rising. Challenges the bioplastics industry faces are wide ranging, the company says, and include the need for sustainable solutions that meet compostability and biodegradability targets, as well as the availability of feedstocks and raw materials. Broad processing windows are essential and mechanical properties and thermal resistance require attention
20 COMPOUNDING WORLD | September 2020
as many bioplastics tend to be inadequate for most applications. Unsurprisingly, cost-effectiveness is also a top priority. The company has developed a number of talc
products for use as fillers in bioplastic compounds. “For rigid applications, process-wise talc improves the melt strength of PLA and polyhydroxyalkanoate (PHA) and eliminates strand breakage during cooling and facilitates compound granulation,” says Anaïs Berjeaud, Development Manager Plastics & Rubber at Imerys. “As an effective nucleating agent, the use of talc can significantly increase the crystal- lisation speed of some biopolymers.” In terms of performance, Imerys says its Steamic, Jetfine and HAR talcs can act as reinforcing agents in biopolymers such as PLA, PBS (polybutylene succinate) and PHA. This can improve heat deflec- tion temperature, dimensional stability, barrier properties and stiffness. All these properties are key requirements for improving and optimising the final properties of bioplastics.
Compostable options Talc can also be used in compostable biopolymer formulations complying with European standard EN 13432. Imerys says its Eco-Delink engineered calcined kaolin has been developed specifically to enhance compostability. The addition of Eco-Delink not only considerably reduces the cost of a biopoly- mer formulation, but also significantly improves its processability by increasing melt strength and reducing tackiness. “At 20% loading in PHA, Eco-Delink provides faster degradation, as well as improving processing conditions,” says Mike Bird, Development Manager Plastics & Rubber. For bioplastic film applications, Imerys says it
also offers specific engineered calcium carbonate grades that can help maximise processing, optical and mechanical properties and reduce the cost of
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