ADDITIVES | POLYAMIDES
Right: Sectional view of a 40% carbon fibre reinforced PA foamed with Luvobatch blowing agent to achieve a 30% weight reduction
Below: Cooling systems on
electric vehicles operate for longer than their combus- tion counter- parts, calling for higher levels of polymer stabilisation
that can enhance a wide range of properties. As well as reducing cost, the company says mineral functional fillers can be used to increase heat resistance and stiffness, and reduce creep, shrinkage and flammability. They can be used to modify specific gravity (density) and flow, while improving abrasion resistance, dimensional stability and thermal conduc- tivity. Mineral functional fillers can also change electrical properties, improve moisture and impact resistance, and modify opacity and gloss. For polyamides, Sebö highlights two examples where mineral fillers can make significant property impro- vements – thermal conductivity and flame retardancy. Thermal conductivity relies on three main mechanisms: convection (material independent); conduction (material dependent); and radiation (influenced by the surface and design of the part). A thermally conductive compound can offer a number of advantages over metals, including freedom of design, part integration and the elimination of seondary processes such as pain- ting. An apporpriately designed part can also offer lighter weight than aluminium and provide a homogeneous temperature distribution. In a recent case study, Sebö cites a module flange for an HVAC automotive application that was produced in a PA6 compound with a fine, calcined aluminosili- cate filler plus coating that resulted in an isotropic thermal conductivity of 1.4 W/mK. As a flame retardant, Sebö says kaolin offers a number of advantages. Kaolin loses around 14% water at a temperature of 400°C and is therefore suitable as a flame retardant or synergist in flame retardant systems for engineering plastics. It is white in colour, improves impact strength, has low abrasion and is chemically inert. It can also be supplied coated or uncoated and in various particle sizes. In polyamide compounds, kaolin can
be used to partly replace common flame retardants such as phosphates and phosphonates. According to HPF, around 20% of phosphonates or phos- phates is typically needed in a 30% glass fibre filled PA to achieve UL94 V-O at a test specimen thick- ness of 0.8 mm. It is looking at replacing glass fibre with kaolin and/or wollastonite while reducing the amount of phosphonates and phosphate. Further investigations into kaolin as a flame retardant synergist are also underway, with some filler blends being trialled as lightweight fillers as an alternative to hollow glass bubbles.
Changing markets The LEHVOSS Group is also seeing an expanding and changing polyamide market. “There are a number of trends influencing new developments in polyamides,” says Mattias Bragvad, Global Business Team Manager. “Heat resistance and lightweighting are the principal issues in polyamide develop- ments. At present there is a lot of movement towards replacing PA66 with other solutions, but also increasing the temperature resistance of standard PA6. In addition, we are seeing increased interest in our blowing agents, which enable further lightweighting in automotive applications. Further- more, increasing interest in biaxially oriented PA (BOPA) films is driving new development in this field. Most of these applications benefit from the use of blowing agents for polyamides. This is a major advantage when trying to reduce weight, without losing significant mechanical properties.” Bragvad says LEHVOSS Group has recently
introduced some new masterbatch products in this area. Luvobatch PA BA 1001 and Luvobatch PA BA 1002 are newly developed endothermic blowing agents for polyamides based on PA6. In combina- tion, they are said to reduce the weight of polyam- ide parts by up to 30%. They work in filled PA compounds and are targeted at injection moulding applications in the automotive sector. PA PPA 9659 is a newly improved processing aid
for PA. Used at a low dosage of 1% in PA film production, both cast and blown, it can help to increase up-time between cleaning as well as
42 COMPOUNDING WORLD | February 2019
www.compoundingworld.com
PHOTO: SHUTTERSTOCK
PHOTO: LEHVOSS GROUP
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