PSI - Issue 45

Kentaro Yamauchi et al. / Procedia Structural Integrity 45 (2023) 125–131 Author name / Structural Integrity Procedia 00 (2019) 000 – 000

128

4

Table 3. Size parameters of the shear tensile test pieces (mm).

a

b

c 3

d

e 3

f

g 3

h 1 1

Polymer test pieces Coated test pieces

50

17 17

97

0 4

100

3.2

173

19

27

The shear tensile strength was defined as the adhesion strength. 3. Results 3.1. Contact angles and surface free energy The contact angles of water and methylene iodide on each sample are presented in Table 4 .

Table 4. Contact angles of water and methylene iodide.

Adherend

Specification

Water contact angle (Degree)

Methylene iodide contact angle (Degree)

PTFE dispersion composite coated

HIREC1100

140 112 104 101 91.0 84.7 79.6

125 84.5 74.6 67.0 61.5 52.0 38.0

Fluorine resin coated Polytetrafluoroethylene Silicone resin coated Silicone resin coated

INT333

PTFE

KR4000G

KR400

Polyethylene

PE

Polyethylene terephthalate

PET

By applying the values presented in Table 2 and Table 4 to the Owens and Wendt theory, the surface free energy γs of each sample in the shear tensile test is obtained, as shown in Table 5.

Table 5. Surface free energy γs of adherends.

Adherend

Specification

Surface free energy γs (mN/m)

PTFE dispersion composite coated

HIREC INT333

2.3

Fluorine resin coated Polytetrafluoroethylene Silicone resin coated Silicone resin coated

15.3 20.4 24.6 28.5 34.3 41.6

PTFE

KR4000G

KR400

Polyethylene

PE

Polyethylene terephthalate

PET

3.2. Adhesion strength A deviation from the linear relationship between the adhesive strength F and surface free energy γs in the low surface free energy region was observed, as shown in Fig. 3. With respect to the adhesion of epoxy resin and polymers, it has been previously reported that the adhesion strength F increases linearly with an increase in γs for the region that has surface free energy greater than 20 mN/m. As shown in Fig. 3(a), the lower limit of the linear relationship between F and γs was extended from the conventional value of 20 mN/m to 15.3 mN/m. For the region of γs less than 15 mN/m, F was almost constant, which represents a deviation from the linear relationship.