Degradation behavior of polymer materials in
the high pressure hydrogen gas exposure

test

Polymer materials have an important role for the hydrogen storage cylinder. But it is not completely clarified
how the high pressure hydrogen affects the polymer materials. The degradation behavior of the high density
polyethylene molding exposed the high pressure H2 gas is investigated by various analysis methods.

・ Optical micrograph of the test specimen
section ・ Bending strength of the test specimen

Schematic overview of the Highpressure cylinder and the test sample

60

The test specimenBendingStress/Mpa
曲げ応力/ MPa

Before the test
5mm

After the test
2.6mm

1cm-4-50

0ENDO.

50100150200010250

1520Temperature/
温度 / ℃ C

25302Θ / deg

3540

The crystallites sizes became
The crystallinity was slightly slightly larger after the test.
decreased after the test.

6866

WhiteArea

6465％
62 64％
60
02
46Position/ /mmSurface
表面 ← ← 測定位置mm

Before
暴露前
After
暴露後

d W / d Log M

0.5
0.4
0.3
0.20.1
0.0 210103

104105 106
分子量107108

相対強度（存在確率） / a.u.

0.6

Free Volume Distribution
Diameter
0.3Before
暴露前
Afterof Free
暴露後
0.2 Volume0.620nm
0.1 0.628nm
0.00.20.40.60.8

細孔直径 / /nm
自由体積直径nm

1.0The MWD was not change The free volume sizes became
before and after the test. slightly larger after the test.

Inner

2322

暴露前
Before
暴露後
After

WhiteArea

21 22.1nm
20 21.5nm
190246Surface
表面 ←← Position/
測定位置 mm/ mm

810→Inner
内部

810→ Inner
内部

The (convert) crystallinity was decrease and lamella sizes
became smaller in the white area.

・ Molecular Weight Distribution (MWD) by GPC
・ Free Volume Distribution by PALS
MWD

暴露前
BeforeAfter
暴露後Surface

Lamella Size Distribution

ラメラサイズ / nm

Crystallites
sizes
20024.1nm
25.1nm

5000

102470Lamella Size/ nm

Crystallinity
76％
75％-2(Convert) Crystallinity Distribution

Before
暴露前
After
暴露後

110
10000

468Deflection/ mm
曲げたわみ/ mm

Crystal structure distribution
analysis by Raman spectroscopy

15000
Intensity / a.u.

Heat熱流Flow/
Wg-1‐1/ Wg

22

Sub‐ m cavities and defect structure may be formed.
The analysis focused on the crystal structure is performed usingby following methods.

XRD Patterns

023.7MPa

The bending strength was decreased andirregular stress liberation behavior wasobserved in the exposure sample.

The area from the surface to about
4mm in depth whitened by theexposure test.

Crystal structure analysis by DSC and XRD
DSC curves

Decrease00(Convert)
Crystallinity/換算 結晶化度/％ %Type‐4 cylinders are more efficiency in manufacturing
processes and lighter than the aluminum lined type‐3.

Before暴露前After
暴露後20←

Sample:High density polyethylene
molding before and after
the exposure test.

EXO.

40

3.9mm
2cm

Before
暴露前After
暴露後35.8MPa←Type‐4Surface layer： CFRP, liner：Resin

Bending
Strength

DSC

XRD

Crystallinity Crystallites size

Before35.8MPa76％

24.1nmAfter

23.7MPa75％

25.1nm

Raman

GPC

PALS

(Convert)
Crystallinity

LamellaSize

Weight‐average
Molecular Weight

Mw

Diameter ofFree Volume

Before65.2％

22.1nm6110000.620nm

After

64.2％

21.5nm6070000.628nmAfter high pressure H2 exposure test, the surface of the molding whitened and the bending strength was decrease. In
the white area, the crystal and amorphous structure changed slightly. It is concluded that the changes of theappearance and the strength were caused by generation sub‐ m cavities and defect structure.
2016年6月TRCポスターセッション2016 No. Ⅳ-2
P01472材料物性第１研究室20160421
STC：開(20160623)