Page 35 - Plastics News May 2018

FeAtures
FEATURES

produced sheets was 1.6 mm. The consolidated plates were 2.3 Methods
then cut into 5 (wide) × 5 (length) mm2 sections (as pre-
impregnated pellets) suitable for injection moulding. The The construction and consolidation quality of the SR-PPCs
length dimension of these cut pieces determined the length were examined by reflection light microscopy (Olympus
of the reinforcing fibres. BX51M, Olympus Co., Japan) on polished cross sections of
the sheets cut perpendicular to the flow direction.
For comparison, additive-free and flame retarded ePP (Versify
4200) compounds with FR (Exolit AP766) contents of 0, 10, and The relative density, meaning the ratio between the
15 w% were produced by melt-compounding using a Labtech measured and the theoretical density, was determined
Scientific LTE-26-44 twin-screw extruder (Labtech Engineering for each type of samples. The density of the specimens
Co. Ltd. Samutprakarn, Thailand; L/D: 44) (with temperature (ρs) was obtained from weight measurements in air and
profile from feed zone to die of 200, 205, 210, 210, 210, water and calculated according to Equation 1, where ma is
and 215°C, and screw rotation speed of 70 1/min) to form the specimen's weight in air, me is the specimen's weight
non-reinforced elastomer sheets with identical FR contents in ethanol, and ρe is the density of ethanol at room
as those of the equivalent SR-PPCs (with 50% reinforcement temperature equal to 0.789 g/cm3.
content and double portion of FR additive in the matrix). (1)

Plaque specimens measuring 80 × 80 × 2 mm in dimensions and
with FR contents of 0, 10, and 15 wt% were injection moulded
both from the non-reinforced and reinforced (50 wt% fibre The theoretical densities were calculated by knowing
containing) granulates with fan gate. The process parameters the composition of the samples and the densities of the
are listed in Table 1. components. The density values of the used materials
given by the producers are 0.876 g/cm3 for the ePP
Table 1. Injection moulding parameters matrix material (Versify 4200), 0.910 g/cm3 for hPP
multifilament, and 1.600 g/cm3 for IFR (Exolit AP 766).
Injection Value Plaque specimens
moulding Standard UL94 flammability tests (ASTM D 635 and ASTM D
parameters 3801) were also performed on the composite specimens.
UL94 classification is used to determine dripping and flame
Injection volume 44 spreading rates.
[cm3]
Injection rate 50 The FR performance of the prepared samples was
[cm3/s] characterized by limiting oxygen index (LOI) measurements
Switch over 10 according to the ASTM D 2863 standard. The LOI value
expresses the lowest oxygen to nitrogen ratio where
point [cm3] specimen combustion is still self-supporting.
Holding pressure 400
[bar] Mass loss type cone calorimeter tests were carried out
by an instrument delivered by Fire Testing Technology
Holding time [s] 10
Ltd. (East Grinstead, West Sussex, United Kingdom)
Residual cooling 15 using the ASTM E 906 standard method. Specimens
time [s] (80 mm × 80 mm × 2 mm) were exposed to a constant
Screw rotational 15 heat flux of 50 kW/m2 and ignited. Heat release values
speed [m/min] and mass reduction were continuously recorded during
Back pressure 20 burning.
[bar]
Dynamic mechanical analyses were performed using a
Decompression 5 Q800 dynamic mechanical analyser (DMA, TA Instruments
volume [cm3/s] Inc., New Castle, DE, USA). Three-point bending mode
Decompression 5 was applied with a span length of 50 mm. The width and
rate [cm3/s] length of the specimens were 10 mm × 60 mm (cut by
Temperature of the zones: 120, 125, 130, 135, 140°C; water jet parallel to the flow direction), respectively.
temperature of the mould: 20°C The scanning range of temperature was −100°C to 70°C,
a heating rate of 5°C/min and a frequency of 1 Hz with a

35 May 2018 Plastics News