Oil-Based and Bio-Derived Thermoplastic Polymer Blends and Composites 261
Table 8.15Influence of N 2 amount, injection speed, weight reduction and mold temperature on
shrinkage, warpage, mechanical properties and cell density of WPC foams.
Dissolved
gas amount
(%)
Injection
speed
(ccm s−^1 )
Weight
reduction
(%)
Mold
temperature
(∘C)
Shrinkage
(%)
Warpage
(%)
Yield
stress
(MPa)
Young’s
modulus
(MPa)
Cell
density
(cells cm−^3 )
0.1 70 10 30 0.70 0.28 5.84 205 6.24E+ 06
0.1 110 20 30 0.78 0.29 4.30 152 3.26E+ 06
0.2 110 10 30 0.76 0.35 5.45 210 1.51E+ 07
0.2 70 20 30 0.94 0.33 4.38 158 1.02E+ 07
0.1 110 10 50 0.80 0.60 5.84 209 8.25E+ 06
0.1 70 20 50 1.07 0.40 4.44 157 2.12E+ 06
0.2 70 10 50 0.83 0.13 6.29 218 1.33E+ 07
0.2 110 20 50 1.09 0.64 3.95 147 1.22E+ 07
Yoonet al. 2009 [62]. Reproduced with permission of Taylor and Francis.
Table 8.16Comparison of properties and cost between HDPE and
WPC foam (weight reduction of 20%).
HDPE WPC foam (20%) Difference
Density (g/cc) 0.95 0.88 7% reduced
Cost (CAD/kg) 1.5 0.9 40% reduced
Shrinkage (%) 3.5 0.87 68% reduced
Warpage (mm) 4.5 0.37 91% reduced
Yield stress (MPa) 4.898 5.059 3% increased
Young’s modulus (MPa) 141.1 181.4 29% increased
Yoonet al. 2009 [62]. Reproduced with permission of Taylor and Francis.
Newspapers are one of the widespread sources of waste paper, and many studies have
been conducted on it.
Sanadiet al. proposed one of the first studies on newspaper’s fibre introduction
in thermoplastic composites in 1994 [65]. They introduced 40 wt% of recycled old
newspaper fibres (ONFs) in polypropylene, resulting in a tensile strength of 34.1 MPa,
and unnotched Izod impact strength of 112 J m−^1. Thanks to the addition of MAPP (3%
of the fibre weight), a 57 MPa tensile strength and a 212 J m−^1 Izod impact strength were
achieved. This study shows the good effect of newspaper introduction in polypropylene
matrix, and the good effect of coupling agent. More recent works [66–70] not only
validate the good results obtained by newspapers fibres but also proposed the possibil-
ity to substitute 20–30 wt% fibreglass (GF)–polypropylene composites by 40–50 wt%
ONFs–polypropylene (PP) composites. This involves a reduction in the use of synthetic
polymers, avoiding glass fibres, and exploiting the environmentally friendly character of
natural fibres. Some interesting results about these works are summed up in Table 8.17.
Some interesting studies have been conducted on the introduction of paper sludge
in thermoplastic composites. Sludge is an abundant waste source; about 300 kg of
sludge is produced for each ton of recycled paper [71]. Properties and composition
