Page 36 - Plastics News May 2018

FeAtures

0.08% deformation were selected. Instrumented tensile impact tests were run on 2-side
notched specimens of 80 × 10 mm × 2 mm dimension (EN
Static tensile tests were performed on dumbbell-shaped
(EN ISO 8256 Shape 3) specimens cut from injection ISO 8256) with a Ceast Resil Impactor Junior (Ceast S.p.A,
moulded plaque specimens by water jet cutting parallel Torino, Italy) type instrument using a 15J hammer. The
to the flow direction (Figure 1). The tensile tests were speed at impact was 3.7 m/s.
carried out by a universal ZWICK Z020 testing machine Scanning electron microscopic (SEM) images were taken
(Zwick GmbH & Co. KG, Ulm, Germany) according to the from the fracture surface of the SR-PPCs using a JEOL
standard EN ISO 527-4:1997 standard. The cross-head JSM-5500 LV type apparatus (JEOL Ltd., Akishima, Tokyo,
speed was set to 5 mm/min, and each test was performed Japan) using an accelerating voltage of 15 keV. The
at room temperature (24°C); at least 5 specimens were samples were coated with gold-palladium alloy before
tested from each material. examination to prevent charge build-up on the surface.
Figure 1 3 RESULTS AND DISCUSSION
3.1 Morphology of the composites

In Figure 2, homogeneous distribution of both reinforcing
fibres and FR additives is revealed by the optical
microscopic photographs taken from the polished cross
sections (see Figure 1) of the injection moulded SR-
PPCs. There is no sign of fibre-matrix detachment or
voids, indicating adequate consolidation quality of the
composites. The skin-core formation, typical for injection
moulded products, is also observable; the fibres are
aligned in the flow direction. In Figure 2C, the contours
of the fibres of the 15% FR containing composite are less
Preparation of dumbbell specimens from the plaque specimens in the distinct as those of the additive-free (Figure 2A) and
parallel to the flow direction
10% FR containing composites (Figure 2B) which can be
Instrumented falling weight impact (IFWI) tests were attributed to the increased fibre-matrix fusion or partial
performed using a Ceast Fractovis 6785 instrument melting of the fibres, likely occurred as a result of firmer
(Ceast S.p.A, Torino, Italy) on the following settings: processing conditions generated by the abrasive effect
maximal energy: 131.84 J, diameter of the dart: 20 mm, of the FR additive being present at high concentration of
diameter of the support rig: 40 mm, weight of the dart: 30 wt% in the matrix of the SR-PP_FR15 composite.
23.62 kg and drop height: 1 m. Square specimens with
dimensions of 80 mm × 80 mm × 2 mm were subjected to Figure 2
IFWI tests at room temperature (25°C) and 25.5% relative
humidity. From the IFWI tests, the specific perforation
energy (Ep [J/mm]) (Equation 2) and the ductility factor
(Dr [%]) (Equation 3) were determined. The ductility factor
was calculated as the ratio of the total impact energy
(Emax [J]) to the energy absorbed until the maximum load
(EFmax [J]). EFmax represents mainly the energy required Optical microscopic images of the polished cross sections (opposite
to initiate fracture in the specimen and corresponds to side from the gate, perpendicular to the flow direction) of (A) SR‐PP,
the deformation at yield, while Emax indicates the total (B) SR‐PP_FR10, and (C) SR‐PP_FR15 [Colour figure can be viewed
energy absorbed until ultimate deformation. at wileyonlinelibrary.com]

(2) Density measurements confirmed that the fabricated
composites are well consolidated; the measured density
(3) values were higher than 95% of the theoretical density in
all cases (Table 2). With increasing FR content, however,
the measured density values do not properly follow the

Plastics News May 2018 36