ADDITIVES | POLYMER FILMS
Table 1: Dynamic coefficient of friction (µD) of 50 micron blown packaging film comprised of 0.75MFI PE with 3000ppm of different mineral antiblock additives
Product Unfilled
Trefil 1313-400 Trefil 1313-600 Sikron SF 4000
Microspar 1380-600 Microspar 1379-300 Microspar 1379-350 Microspar 1379-400 Microspar 1379-600
Source: HPF The Mineral Engineers
Table 2: IR transmission measurements of 50 micron blown agricultural greenhouse film comprised of 0.75MFI PE with 10% of different mineral additives
Product Unfilled
Microspar 1380-60 Microspar 1379-300 Microspar 1379-350 Microspar 1379-400 Microspar 1379-600
Source: HPF The Mineral Engineers
UV transmission and IR absorption. The additives used are characterised by a refractive index that is almost identical to that of the polyethylene films, resulting in good optical properties. Different particle size distributions also play an important role, especially with antiblocking films. Trefil 1313-400 and Trefil 1313-600 are finely
ground and processed natural anhydrite minerals belonging to the anhydrous sulphates group. Anhydrite has a tabular structure, density of 3.0 g/ cm3
, Mohs hardness of 3.5, high whiteness (Y=89)
and good transparency. Sikron SF 4000 is a cristabolite that is synthetically-produced from pure silica at around 1,500°C in a rotary kiln (cristabolite rarely occurs in nature). During this process the lattice structure is widened, which reduces the density and results in a high degree of whiteness. Like silica, cristobalite is chemically inert. It has a blocky structure, density of 2.35 g/cm3
, Mohs hardness of 6.5, high whiteness
(Y>94), high chemical resistance and a coefficient of thermal expansion of 54×10-6
/K (at 20-300°C).
Microspar 1380 and 1379 feldspars are chemically resistant tectosilicates with thick,
36 COMPOUNDING WORLD | January 2020
Transmission [%] 83.3 36.0 37.8 36.5 39.7 34.2
plate-like grain morphologies. Using mainly potash feldspar, HPF processes, separates, classifies and finely grinds this material. Properties include a thick tabular structure, density of 2.6 g/cm3
Inside against itself
0.48 0.46 0.43 0.46 0.38 0.48 0.46 0.47 0.39
Outside against itself
0.42 0.45 0.37 0.43 0.38 0.46 0.44 0.40 0.38
Inside against stainless steel
0.45 0.32 0.22 0.27 0.28 0.28 0.28 0.26 0.32
Outside against stainless steel
0.40 0.34 0.24 0.31 0.30 0.31 0.29 0.26 0.32
, Mohs hardness of 6, high
whiteness (Y>90), high chemical resistance, low refractive index and it behaves transparently in many binder systems. HPF says that in its study, a 60% polyethylene masterbatch with an MFI of 2.0g/10 min was produced using the different additives. 50 micron thick blown films were produced with an additive concentration of 3000ppm for the antiblocking films and 10% for the agricultural films. The base film polymer was an 0.75 g/10 min MFI (190°C/2.16 kg) grade. Dynamic COF results for the antiblocking films are shown in Table 1. Table 2 shows IR transmission results for the agricultural films, demonstrating improved thermal properties that will reduce energy costs in greenhouse applications. Total transmission in the visible wavelength range is only slightly influenced by the use of the additives, says HPF. However, too much direct light can have a harmful influence on plant growth so a higher proportion of diffused light is a positive, says the company.
CLICK ON THE LINKS FOR MORE INFORMATION: �
www.ampacet.com �
www.palsgaard.com �
www.basf.com �
www.polyone.com �
www.clariant.com �
www.merckgroup.com �
www.sabic.com �
www.dupont.com/industrial/
multibase.html �
www.kafrit.com �
www.hpfminerals.com
www.compoundingworld.com
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