This document is posted to help you gain knowledge. Please leave a comment to let me know what you think about it! Share it to your friends and learn new things together.
Barrier EVOH has a superior gas barrier when exposed to low moisture conditions
EVOH has a poor WVTr barrier
PVDC has a very good gas barrier and Not affected by moisture conditionsPVDC has excellent moisture (WVtr) barrierAt low temperature (4°C) the PVDC has a better Oxygen barrierPVDC performs well in retort process EVOH looses barrier level after retort
Process EVOH is reasonable easy to process. EVOH is hydroscopic, that can impact both the processability and end use of EVOH
EVOH can be coextruded with many different polymers in coextrusion process
Some grades of EVOH can be difficult to process (low PE content high barrier))
PVDC : new extrusion technologies has been developed in which PVDC is coextruded with many different polymers
PVDC is very heat sensitive, which makes it difficult to process. Special alloys necessary to process PVDC
Shrinkage Bioriented Film PVDC can reach 50 and more % of shrink in the both direction, without delamination problem
EVOH is limited in shrink ratio (bioriented film)
Recycle EVOH regrind can be reused PVDC is more difficult to reused (solutions exist)
New extrusion technology for multilayer blown film (No shrink film)
Interest in multilayer blown films with PVDC has grown Can lead to a one-step process, eliminating laminations Use the advantages & benefits of PVDC for non-shrink applications
The challenge: Larger dies are used (>20 cm), which extend the residence time inside the die, and can accelerate degradation
2 concepts to overcome this: Pre-encapsulation of PVDC by another resin which is thermally
stable and compatible with PVDC. Macro Engineering Improved thermal insulation between layers Brampton Engineering
Barrier after Retort (No Shrink film) Brampton Line
Function Processing temperature Thicknessµm
PA 666 copolymer PA 6 and PA 6,6 (80/20) mechanical properties 245 - 250 °C 17reduced cristallisation puncture resistance (PA limited to skin layer)better transparency thermoformingbetter BURfrost line shifted
E MAH maleic anhydride reacts chemically with PA tie layer 215-225 °C 20E is miscible with LDPE
LDPE cost reduction 185 - 190 °C 24EVA tie layer 185-190 °C 19
PVDC barrier 160 °C 31EVA tie layer 185 - 190 °C 22
m LLDPE metalloscene LDPE sealing layer 215 - 225 °C 40clarity, low temperature seal(blending ionomer is also an option)
Total thickness (µm) 173OTR @ 25 °C 1,2 cc/m2.d.b (dry and humid 85 %)
0,7 cc/m2.d.b after sterilisation
similar film structure containing EVOH excellent OTR dry < 1 but increased > 10 cc/m2.d.b after sterilisation