|
Home > MacroLetter > 3.2 - Summer 1997 > Extrusion of Highly Degradable Materials
Extrusion of Highly Degradable Materials
In order to be successful in PVDC extrusion, extreme attention must be paid to the following: extrusion conditions; residence time; equipment design; material used; and precise control of the extrusion process. Our many years of experience has been applied to the design of new PVC and PVDC co extrusion dies for 3 and 5 layer applications.
These recent developments in die design open new opportunities for processors using highly degradable materials (i.e. PVC, PVDC, EVOH, etc) for barrier packaging applications. For example, PVDC not only has excellent barrier properties for oxygen and aromatic hydrocarbons but also for water vapor. These barrier properties make PVDC a very suitable candidate for freezer meat packaging to eliminator “freezer burn”. Other packaging applications include: dry biscuits; fruit; cheese; aromatic spices; and medical applications, where moisture prevention is absolutely essential in the packaging of most pharmaceutical drugs.
The table below indicates barrier properties of different resins. As you can see from the comparison, EVOH in a dry environment has excellent barrier properties for O2. However, in a moist environment, these properties dramatically deteriorate.
| |
O2(a) |
H2O(b) |
Tensile Strength
(mpa) |
Impact Strength
(kg-cm) |
Haze (%) |
| PVDC(c) at 0% RH |
0.08-0.2 |
0.05-0.2 |
55-400 |
10-15 |
2 |
| PVDC(c) at 100% RH |
0.08-0.2 |
0.05-0.2 |
55-400 |
10-15 |
2 |
| EVOH F at 0% RH |
0.01 |
|
80-130 |
|
1.5 |
| EVOH F at 90% RH |
1.15 |
3.8 |
|
|
1.5 |
| PA 6 |
2.6 |
24-26 |
48-124 |
4-6 |
2 |
| BOPA |
2 |
12 |
172-210 |
30 |
1-2 |
| LDPE (LLDPE) |
250-840 |
1.0-1.5 |
14 (24-55) |
7-11 (8-13) |
4-10 (6-20) |
| HDPE |
30-250 |
0.3-0.65 |
21-52 |
1-3 |
25-50 |
| PP |
150 |
0.25-0.7 |
35 |
30 |
1-2 |
| OPP |
110 |
0.3-0.4 |
172-210 |
5-15 |
3 |
| PVC |
5-1500 |
2.8 |
14-110 |
12-20 |
1-2 |
| PET |
4.8-9 |
1.8-3 |
172 |
25-30 |
4 |
| EVA (> 12% VA) |
515-645 |
3.9 |
21-34 |
11-15 |
2-10 |
| Ionomer |
226-484 |
1.3-2.1 |
24-38 |
6-11 |
1-15 |
| PS |
100-200 |
5.0 |
34-55 |
12-16 |
0-1 |
(a) permeability measured as cc mil/100 in2 day atm @ 23C
(b) g mil/100 in2 day @ 38C, 90% RH (Relative Humidity)
(c) coextrusion grade
|
