260 Introduction to Renewable Biomaterials
0.0
0 0.5 1
Azocarbonamide as CBA
CBA content (phr)
Density (g/cm
3 )
1.5 2 2.5
0.5
- 5
2.0
0.0
0 0.5 1
Sodium bicarbonate as CBA
CBA content (phr)
(a) (b)
Density (g/cm
3 )
1.5 2 2.5
0.5
- 5
2.0
Figure 8.17Influence of exothermic (a) and endothermic (b) blowing agents on PVC/wood flour
density. Adhikaryet al. 2012 [60] Reproduced with permission of Sage Publication.
Table 8.14Influence of CBAs on
average cell size.
CBA phr Cell size
Azocarbonamide 0.5 44
Azocarbonamide 1 42
Azocarbonamide 2 41
Sodium bicarbonate 0.5 65
Sodium bicarbonate 1 65
Sodium bicarbonate 2 64
Adhikaryet al. 2012 [60]. Reproduced
with permission of Sage Publications.
injection speed. Moreover, cell density was conditioned by N 2 amount, injection speed
and weight reduction. Some results are display in Tables 8.15 and 8.16.
WPCs are a well-established class of materials, with their known properties and
their own market. However, improvement in order to increase WPC properties and
environmental friendly character could still be done. The use of virgin wood for WPC
materials could overcome its usual application; moreover, WPCs can be processed
through traditional thermoplastics processes and post-processed with the same method
of traditional wood.
8.3.2 Waste Paper as Filler in Thermoplastic Composites
Problems related to paper disposal has grown during last year, despite paper being the
most recycled product in Europe and 54% of paper industry’s raw materials come from
waste paper and paperboard [63].
Paper cannot always be subjected to traditional recycling processes. In fact, approx-
imately just 50% of all the cellulosic wastes is used in recycling processes, the rest has
to be send to incinerators or landfilled as solid wastes [64].
In order to reduce the environmental impact of paper industries, the possibility of
introducing different kinds of waste paper is opened.
