(181br) Modification of Recycle-PET and Its Compression Molding Process Foamed By Supercritical CO2 | AIChE

(181br) Modification of Recycle-PET and Its Compression Molding Process Foamed By Supercritical CO2

Authors 

Liu, T. - Presenter, East China University of Science and Technology
Zhao, L. - Presenter, East China University of Science and Technology
Chen, Y. - Presenter, East China University of Science and Technology
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normal">Modification
of Recycle-PET and its Compression Molding Process Foamed by Supercritical CO2

Yichong Chen, Tao
Liu*, Ling Zhao*

Shanghai Key
Laboratory of Multiphase Materials Chemical Engineering, East China University
of Science and Technology, Shanghai 200237, PR China

liutao@ecust.edu.cn,
zhaoling@ecust.edu.cn; Phone: (+86) 21 64253470; Fax: (+86) 21 64253528

normal">ABSTRACT

Polyethylene
terephthalate (PET) foam has good mechanical properties, which is mainly used
for core materials in wind power, aviation, transportation and other fields.
However, the melt strength of ordinary PETs, especially for recycle-PET (R-PET)
which usually is mixed with other low melt strength polymers or inorganic
materials, is too low to meet foaming requirement. In addition, most of the
large-scale PET foam production processes are extrusion technology using CO2/alkane
compound
foaming agents, which usually have larger cell size and lower mechanical
properties. Compression molding process foamed by supercritical CO2 is
a new technology to produce microcellular PET foams with large-size outline
dimension.

In this study, R-PET was
modified chemically in the twin-screw extruder. The low loss factor (tan ¦Ä) and
high characteristic relaxation time (¦Ë) fitted by Maxwell model (Figure.1) of
modified R-PET showed its long branched chain structure, which is beneficial for
supercritical CO2 foaming. The R-PET-4 foams were produced by a
one-step depressurization process in a self-made compression molding foaming
device. The expansion ratio of R-PET-4 foam could reach 16.42. Its cell size is
reduced by nearly 10 times compared with the commercially extrusion foam sample
under the similar expansion ratio (Figure.2 and Table.1), which results in much
better mechanical properties (Figure.3).

(a)

(b)

normal">Figure.1 (a) The loss factor (tan ¦Ä) of
modified R-PET under 0.1-100 rad/s; (b) The relaxation time (¦Ë) of modified R-PET fitted by Maxwell model

(I)

(II)

(III)

(IV)

normal">Figure.2 SEM of foamed PET samples: Compression molding
foamed R-PET-4 foaming at 250¡æ (I), 253¡æ (II), 255¡æ (III); Commercially extrusion
foam sample provided by Gruit (IV) " times new roman>

normal">Table.1 Data of cell structure
for different foamed samples

Sample

Expansion ratio

Average cell diameter (¦Ìm)

Cell density (cells/m3)

I

2.47

21.91

6.60E+12

II

12.08

81.79

2.78E+11

III

16.42

99.88

2.05E+11

IV

15.41

905.14

4.81E+8



normal">Figure.3 Mechanical properties comparison