ADDITIVES | PROCESSING AIDS


level of maleated coupling agent (Viscospeed acts as a co-compatibiliser) in the formulations using the additive, tensile strength is maintained above the critical value of 10 N/mm2


. Viscospeed can also be used to advantage in


sheathing compounds based on POE (polyolefin elastomer) resins. Its use has also been investigated in several different bedding compounds with very high filler loadings. In recent months, the company has conducted


further trials on cable sheathing compounds with a fixed content of the coupling agent and these support the earlier results. “In combination with both typically-used base polymers (EVA-copoly- mers and POE) we could prove the improved processing behaviour without sacrificing the mechanical properties,” says Christoph Bornschein in the company’s Customer Technical Service. “Viscospeed has especially a beneficial effect on compounds based on milled MDH and shows in our case study an improvement of the MFI [Table 1]. In our trial formulation using an EVA-based sheathing formulation, the impact of Viscospeed was not so obvious when only looking at MFI values. Nonetheless, the further rheological evaluation using a Brabender showed a strong decrease in torque by almost 20%. These two trials show nicely that Viscospeed is able to optimise the dispersion of inorganic fillers in different HFFR compounds,” Bornschein says. Dow Plastics Additives highlights its Surecel


and Paraloid additives for technologies used to produce foamed PVC extrusions, of which there are


Table 1: Impact of Viscospeed on key properties of a POE/TPO HFFR cable formulation containing milled MDH


FORMULATION POE, MFI 0.5 TPO, MFI 0.5 Viscospeed


Compoline CO/LL Ecopiren 3,5


Silmastab AX2244 Silmastab AE1527


Silmaprocess AL1142A Total


PROPERTIES


MFI ( 21.6kg @ 190°C), g/10min Tensile strength, MPa Elongation at break, % Burning dripping


Source: Innospec Leuna 66 COMPOUNDING WORLD | April 2021


Standard Viscospeed 26 8


3 60


0.75 0.75 1.5


100


23 8 3 3


60


0.75 0.75 1.5


100


Standard Viscospeed 1


4 12


197 Yes


11.5 180 No


three main types – free foam extrusion, Celuka extrusion, and co-extrusion. “Surecel and Paraloid Processing Aids combined


with Paraloid Polymeric Lubricants contribute to reducing waste during manufacturing,” says the supplier. “Additionally, the thickness of the final product is easily controlled, offering manufacturers low density products without sacrificing the product’s performance.” The additives help create foams with very small cells and a narrow cell size distribution, the company adds. Included in the company’s offering are specially- designed Paraloid Processing Aids for foam core PVC pipes. “The weight is significantly reduced by obtaining the optimal retention of gas in the cells, which results in optimal pipe properties,” says Dow. Paraloid Polymeric Lubricants also prevent the melt from sticking to the hot metal surfaces of the equipment, even at high temperatures.


Foamed sheet In foamed PVC sheet production, the need to reduce product waste is a key challenge for converters, especially those that work with wide dies, says the company. The latest generation of Surecel Processing Aids


are specially designed to improve quality and reduce waste during production of PVC foam sheets. Surecel 488 Processing Aid, now available in North America and Latin America, has a high molecular weight and is designed to obtain excellent melt strength enabling thick foamed sheets. This new grade provides high efficiency and expansion, with an excellent cell structure, comprising very small cells and a narrow cell size distribution. The Surecel 4280 Processing Aid, which is available in the EMEAI region, is a very high molecular weight processing aid with a tailored molecular weight distribution. It helps to optimise the melt flow of the foamed PVC through the wide dies used for the free foaming extrusion process and stabilises the structure to create foamed PVC sheet with high cell density and small cell size. The products differ between regions due to the diversity in applications and differences in associ- ated rheological requirements. According to Dow, free-foamed PVC in the EMEAI region is most often used in thin sheet applications where large surfaces are inkjet or laser printed. “These applica- tions require a very smooth surface for printing and constant thickness,” says Ian Drake, Senior R&D Leader of Dow’s global Plastics Additives business. “If the thickness is inconsistent or the surface is not smooth enough, then the print definition is poor.” In North America, by contrast, by far the largest


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