ADDITIVES | NUCLEATORS AND CLARIFIERS


additional use of that know-how in designing a masterbatch for final applications,” he says. The Constab NC 00607 PP masterbatch with


BASF’s Irgaclear can be used at low levels in PP blown films to reduce haze, remove flowlines and visual defects, and improve stiffness and mechani- cal performance in both the machine and trans- verse direction. Weber cautions that it is not a ‘drop-in’ solution, but it does increase flowability, enable stable processing, and improve the processing window. He sees interest from the industry, as this technology could give more processors the ability to use PP.


Nucleating polyamides US-based distributor CAI Performance Additives recently introduced a nucleating agent for polyam- ides to the North American market. ST NA22D is sold as a granulated powder for compounding into PAs including PA6, PA66, PA11, and PA12. It is an additive blend of PA22 with a specially treated highly functional mineral that allows use at low dosages, says Richard Marshall, CEO of the company. It is said to be useful in unreinforced and reinforced polymers, forming a fine and uniform crystal structure in glass-filled PA resin. During moulding, the nucleating agent shortens cycles and improves dimensional stability, mechanical properties and stress cracking resistance. “While not every large volume PA will need this


sort of performance additive, there are many applications continuing to push the boundaries of performance,” says Marshall. “One application we are hearing about more and more is vehicle electrification. People are pushing thinner and more difficult to mould components. For non-struc- tural uses, they are looking for lighter, tougher parts,” says Marshall.


Film samples showing the haze improvement achievable in 3-layer blown PP film using Constab’s NC 00607 PP performance enhancer with Irgaclear Source: Constab Polyolefin Additives


Figure 3: Onset crystallisation temperature and crystallisation half time of a copolymer PP nucleated with Crys-Talc Source: Imerys


62 COMPOUNDING WORLD | June 2021


Mineral option Talc is widely used as a nucleating agent in semi- crystalline polymers — particularly in PP but also other polyolefins, polyamides, polyesters and polyacetals. “Usually, fine (10 micron top size) and ultrafine (3 micron top size) talc grades are used for nucleation of semicrystalline polymers because such grades contain a higher number of fine particles, which all act as crystal seeds,” says Michael Schmidt, Technical Service Manager at Imerys. The company’s Crys-Talc grade is said to be optimised for nucleation. This talc range features a micro-lamellar morphology and contains more ultrafine particles than conventional talc of similar fineness, according to Schmidt. “95% of the Crys-Talc particles are smaller than one micron. More than 50% of the particles are under 0.5 micron, whereas conventional talc with the same fineness does not contain these fine particles at all. That unique property makes Crys-Talc a high performing nucleating additive,” he says. As shown in Figure 3, nucleation of polypropylene with talc at addition rates as low as 0.5wt% results in an increase of recrystallisation temperature and the reduction of the crystallisation half time. This allows faster processing, resulting in increased extrusion and injection moulding productivity. Nucleation using talc also improves many polymer properties, including modulus and strength as well as impact resistance. “Additionally, the dimensional stability of plastic mouldings can be greatly improved, resulting in low warping, especially in combination with fibrous reinforce- ment such as in glass fibre/mineral hybrids,” says Schmidt. At addition rates higher than 0.5wt%


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