Photon Factory Activity Report 2017 #35 (2018)

BL-6A/2017G582

Changes in Long Period of Polyamide 6 Filament by Heating
Kai Kimura and Masatoshi Shioya*
Tokyo Institute of Technology, 2-12-1-S8-34 Ookayama, Meguro-ku, Tokyo 152-8552, Japan
1 Introduction
Recently, actuators made with twisted polymer
filaments which contract and recover in response to thetemperature change attract great attention for their
extraordinary large actuation stroke and silent operation[1]. It has been considered that their extraordinary large
stroke is related to the negative thermal expansion
coefficient in the filament axis direction, to which theentropic elasticity may play an important role. However,details of the mechanisms of the actuation have not been
completely clarified yet. The present experiments aim atcollecting basic data required for considering themechanisms of the actuation of the polymer filament
actuators. The changes in the long period of thepolyamide 6 filament during heating and cooling cycles
have been investigated.
2 Experimental
A polyamide 6 filament (BERRY LINE Nylon,Tackleberry Co., LTD.) with the glass transition
temperature at about 47 oC, the melting temperature atabout 220 oC, and the diameter of 370 μm was used forthe experiments. The nylon filament was heat treated at
180 oC for 1 hr by holding it at a constant length sincesimilar heat treatment is applied to produce the polymer
filament actuators. The SAXS measurements wereperformed at BL-6A in Photon Factory using the X-ray
with the wavelength of 0.15 nm at the sample-to-detector
distance of 1.4 m. The nylon filament was heated andcooled at a fixed length using a heating apparatus (Instec,HCS302) during the SAXS was detected with PILATUS31M.
3 Results and Discussion
Fig. 1 shows the SAXS pattern of the nylon filament at
180 oC. The filament axis is in parallel to the up-anddown direction of this figure. The layer-line scattering is
caused by the long-period structure of nylon 6 which
consists of the alternative repetition of the crystallites andthe amorphous regions in parallel to the filament axis.
Fig. 2 shows the SAXS intensity distributions along theline in the meridional direction and passing through thecenter of the incident beam, which were measured during
the heating process of the 2nd heating and cooling cycle.
It can be found that the scattering peaks shift to the lower
scattering angles with increasing temperature. Thisindicates that the long period increases with increasing
temperature. It can be also found that the scattering
intensity increases with increasing temperature above theglass transition temperature. This indicates that theelectron density difference between the crystallites andFig. 1: SAXS pattern of nylon filament obtained at
180 oC.

Fig. 2: SAXS intensity distributions of nylon
filament obtained at temperatures shown inthe figure.

Fig. 3: Long period vs. temperature during 1st and2nd heating and cooling cycles shown in thefigure for nylon filament.
the amorphous regions increases due to the expansion of
the free volume in the amorphous regions.

Photon Factory Activity Report 2017 #35 (2018)

Fig. 3 shows the changes in the long period during
heating and cooling cycles. It can be found that longperiod increases during heating. It has been reported thatoriented nylon 6 shows negative thermal expansion attemperatures above about 100 oC. [2] This difference mayarise due to the difference in the extent of orientation
between the specimens used in this study and theliterature. Further experiments are needed forunderstanding the results shown in Fig. 3.
Acknowledgement
The authors are indebted to Profs. N. Igarashi, N. Shimizu,H. Takagi and T. Mori at PF for their experimentalsupport.
References[1] C. S. Haines, et al., Science, 343, 868 (2014).
[2] C. L. Choy, et al., J. Polym. Sci. Polymer Physics
Edition, 19, 35 (1981).
* shioya.m.aa@m.titech.ac.jp