ADDITIVES | CLARIFIERS AND NUCLEATORS
Right: Nucleant PP 4000389-E from Ampacet improves mechanical properties and stiffness without affecting polymer density or transparency
maintaining good impact performance. The resulting thermoformed parts provide a clean and fresh look said to rival PET.
Hyperform 909ei is also designed for use by thermoformers in PP homopolymers. While it offers good aesthetics and a favourable balance of stiffness and impact properties, it has been developed with a simpler chemistry for food-con- tact applications that results in one SML (specific migration limit) less than the previous-generation product. Millken says this is an advantage when developing products to meet European Union food contact regulations. Masterbatch maker Ampacet has developed
Nucleant PP 4000389-E, a nucleating additive that improves the mechanical properties and stiffness of injection moulded or thermoformed PP parts without affecting polymer density or transparency. It is said to allow downgauging of parts and end products while maintaining the same rigidity. The company says that Nucleant PP is suitable for use in both virgin and post-consumer recycled resins and, because it does not alter the density of the polymer, it does not prevent flotation separa- tion being used at recycling facilities so customers can meet sustainability goals. Suitable for opaque or transparent applications, Ampacet Nucleant PP is claimed to offer good optical properties, including improved clarity and reduced haze when used in transparent parts.
Beta nucleation Nucleating agents are used in PP to improve a variety of physical and optical properties. “The improved stiffness and strength of nucleated polypropylene and the faster achievable cycle times in moulding and extrusion leads to down- weighting and cost savings,” says Dr Philip Jacoby, independent consultant and President of Jacoby Polymer Consulting. “Nucleated polypropylene also exhibits higher heat deflection temperatures, allowing it to be used in more demanding, high temperature applications.” Jacoby says that aside from greater clarity,
reduced haze, enhanced strength and stiffness, and improved HDT, nucleation also results in reductions in cycle times and warpage and provides more uniform shrinkage. There is also a reduction in pigment sensitivity — different coloured pigments can result in significant and variable property changes — and processing can benefit in certain applications. In recent years, high performance nucleating agents have been introduced that achieve even better levels of clarity and stiffness, and further
48 COMPOUNDING WORLD | June 2022
reduce warpage and shrinkage. “Almost all commercially available nucleating agents nucleate the alpha crystal phase of polypropylene, which is the most common crystal form,” says Jacoby. “Another lesser-known crystal phase of polypropyl- ene, referred to as the beta phase, has been known for over 50 years. There are nucleating agents that will produce high levels of the beta crystal phase during moulding or extrusion. This phase results in some interesting properties including higher impact strength and ductility, a lower melting point, and a tendency to undergo self-cavitation or micro-voiding when stretched in the solid state.” In recent years, beta nucleating agents have been used to produce a number of products and have realised significant performance improve- ments. Jacoby says that examples include lighter weight pressure pipes with improved creep rupture resistance and microporous, breathable films used in protective clothing, roofing membranes, and battery separator membranes. High strength geogrids for use in road construction and soil stabilisation have also been developed that are lighter weight and less costly to produce. Lighter weight and stronger thermoformed
packaging is also possible through beta nucleation, including production of food containers that offer an opaque white appearance without the use of pigments due to the creation of micro voids. “One limitation on the use of beta nucleation concerns the fact that they cannot be used if high levels of clarity and low haze are required,” says Jacoby. “Nevertheless, the growing use of beta nucleating agents will continue to expand the markets and applications for polypropylene.”
CLICK ON THE LINKS FOR MORE INFORMATION: �
www.njceurope.com �
www.adeka-pa.eu �
www.milliken.com �
www.ampacet.com �
www.jacobypolymer.com
www.compoundingworld.com
IMAGE: AMPACET
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