Interface analysis of deuterated and non-deuterated polyamide 66 with neutron reflection
Kobe University, Takuya Matsumoto
1. Introduction
Polyamide 66, namely nylon 66, is widely accepted as an engineering plastic in the field of the vehicle industry.
Therefore, the component materials based on polyamide 66 are integrated in the vehicle framework. However,polyamide 66 has an disadvantage on its adhesion property and the low adhesion property leads to the trouble ofthe products. Additionally, the weld line formed in the molding process and the weak boundary interface ofthermal fusion trigger mechanical defects of the products. The analysis of interface consisted of components swith the same chemical structure in the weld lines is a challenge because of no difference between theircomponents. The mechanical property at the adhesion interface depends on the thickness of the adhesion layers.
The interfacial layer is controlled by mutual diffusion of their components. Therefore, we investigate the mutual
diffusion of polyamide 66 at the interface from the view point of molecular dynamics. The polymers with thesame chemical structure in their interface layers were not able to discriminate with one another in conventional
method such as X-ray and microscopic measurements.
We focused on the interface between protonated and deuterated polyamide 66 in order to detect them
spectroscopically with Raman scattering and neutron beam. In advance, we investigated their structure andproperties. The mechanical and thermal properties of protonated and deuterated polymers are remarkably similar,
whereas Raman scattering bands originated from CH2 and CD2 and neutron scattering length densities aresignificantly different. The measurements with Raman scattering and neutron beams detect the difference in theirpolymers. Moreover, the neutron beam possesses high material permeability. Therefore, the analysis of ever innerinterfacial structure by neutron beams can be accessed non-destructively. The elucidation of their interfacial
structure leads to the mechanism of the adhesion of the same polymer.
Herein, we prepared double-layers on silicon wafers with protonatedand deuterated polyamide 66 (H-PA66 and D-PA66) and investigated theirinterface structures with time-sliced neutron reflectivity (NR) measurements.
We have synthesized D-PA66 and H-PA66 and measured their thermal
properties and structure. Their thermal properties and structures werecorresponded with each other, while in the NR measurements ofFigure

single-layered films, their thin films were distinguished.

double layer model.

2. ExperimentWe
D-PA66/H-PA66/Si

1.

D-PA66/H-PA66

preparedsamples,asshown in Figure 1. Before thermal
annealing, we measured NR of
their samples at room temperature.
Theqranges

intheNRmeasurements were from 0.01 Å−1
to 0.10 Å−1. We analyzed and fitted
the NR profiles with Motofitsoftware.

Figure 2. NR and SLD profiles of D-PA66/H-PA66 double layer atroom temperature.
1Next, under thermal annealing, time-sliced neutron reflective measurements were performed at 80 °C, 120 °C,
150 °C and 230 °C. The q ranges in the NR measurements were from 0.01 Å−1 to 0.06 Å−1.
3. Results
Figure 1 shows NR profile of D-PA66/H-PA66/Si at room temperature and the fitting data. From the neutron
scattering density profiles, the thickness of D-PA66 and H-PA66 were 114.9 nm and 71.0 nm, respectively. Thethickness of interfacial region was 4.4 nm. The obtained thickness of films corresponded approximately to theresults from AFM topological images.
The time-sliced NR profiles under annealing at various temperature are shown in Figure 3. Under annealingat less than 150 °C, the NR profiles were not changed for 8 h. In contrast, under annealing at 230 °C, the NR
profiles were changed within the first hour. Therefore, we focused on the NR profiles within 30 min annealing
time. The gradual changes of the NR profiles were observed.
In the laminated films with 200 µm thickness, it was observed from the Raman scattering measurements withline scanning that the expansions of interfacial region were enhanced by annealing at 150 °C. The results werecontradictory to NR measurements. The reason would be that the laminated films with 200 µm thickness wereprepared with heat-pressing under 6.0 MPa, while the double layers were annealed under non-pressure in thetime-sliced NR measurements.

Figure 3. NR profiles of D-PA66/H-PA66 double layer at (a) 150 °C, (b) 230 °C and(c) 230 °C in the first 30 min.
4. Conclusion
It is proved from the obtained NR profiles that the double layers with low roughness were formed. Fromtime-sliced NR measurements, the structure of the double layer was changed by annealing at 230 °C, not at150 °C. Unfortunately, the results disagreed with the experiments of laminated films with 200 µm thickness.
Therefore, we have plans to measure time-sliced NR of the double layers under thermal annealing withcompression pressures. We are going to apply this proposal as 2018B term experiments.

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