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Strontium ferrite, Copper, Cu Glass fibres
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SrFe12O19
Thermal conduc- a:4.61G0.42, l 11:2.07G0.02,l33: l11:1.76G0.00,l33: l11:401 l:1.2–1.5
tivity (W/(m K)) a:5.10,l11:9.7 2.92G0.07, 10.69G1.35,
a:1.72G0.04 a:2.97,a:3.00G0.10,
a:6.10G0.90
Reference [13]
[13]
[13]
[14]
[15]
Mean particle diam- 9 1.5 2.0 1.5 15 11
eter (mm)
Particle shape Irregular Irregular Platelet Irregular Irregular Fibre
Density (g/cm3) 5.1 4.48 2.78 5.11 8.94 2.58
a denotes measurements on monomineralic aggregates. Directions of anisotropy are specified by the thermal conductivity tensor (l11, l22, l33), where l11, l22
and l33 are parallel to the crystallographic axes a, b and c, respectively.
polypropylene, e.g. for bottle closures (cosmetics industry, cf. Ref. [10]), strontium ferrite is used in polymer bonded
time t after injection. Neglecting higher order terms, Eq. (3) can be reduced for the position xZs/2 to
magnets, glass fibres are used for the reinforcement of materials, and talc is an anti-blocking agent. However, copper was chosen as additional filler because of its high
thermal conductivity compared to the other materials.
The thermal properties of these injection moulded samples and the injection moulding behaviour were investigated and correlated to the amount and the kind of filler material.
2. Theoretical considerations
The Fourier law of heat transport in one dimension is given by
vt vx2 (1)
with temperature T, time t, position x and thermal diffusivity a. In an homogeneous body, thermal diffusivity a and thermal conductivity l are interrelated by specific density r
and specific heat capacity cp according to
l Z cpra (2)
Assuming an injection moulding process with an isothermal filling stage for a polymer with a temperature TP and a constant temperature of the mould TM as well as a temperature independent thermal diffusivity a, an analytical solution of Eq. (1) results in [9]
4
Eq. (4) gives a relation between cooling rate and thermal diffusivity in an injection moulding process, where high thermal diffusivities result in a higher cooling rate and shorter process cycles.
3. Experimental