Effects of vapor‐phase‐formaldehyde treatments on thermal conductivity and diffusivity of ramie fibers in the range of low temperature

Abstract

To understand the influence to thermal conductivity by bridging in the polymer fibers, the thermal conductivity, and thermal diffusivity of ramie fiber and those bridged by formaldehyde (HCHO) using vapor‐phase method (VP‐HCHO treatment) were investigated in the lower temperature range. The thermal conductivities of ramie fiber with and without VP‐HCHO treatments decreased with decreasing temperature. Thermal diffusivities of ramie fiber with and without VP‐HCHO treatments were almost constant in the temperature range of 250–50 K, and increased by decreasing temperature below 50 K. Thermal conductivity and thermal diffusivity of ramie fiber decreased by VP‐HCHO treatment. The crystallinities and orientation angles of ramie fibers with and without VP‐HCHO treatment were measured using solid state NMR and X‐ray diffraction. These were almost independent of VP‐HCHO treatment. Although tensile modulus decreased slightly by VP‐HCHO treatment, the decrease could not explain the decrease in thermal conductivity and diffusivity with decreasing sound velocity. The decrease of the thermal diffusivity and thermal conductivity by VP‐HCHO treatment suggested the possibility of the reduction of the mean free path of phonon by HCHO in VP‐HCHO treated ramie fiber. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 2754–2766, 2005

Radiation effect on the thermal conductivity and diffusivity of ramie fibers in a range of low temperatures by γ rays

“…It is reported in a previous article 40 that the behavior of thermal diffusivity is almost independent of the number of measuring filaments. Therefore, the influence of thermal radiation and fiber bundling on the measurement of the thermal diffusivity can be neglected.…”

“…The dependence of the observed thermal conductivity on the number of filaments was reported in a previous article. 40 In the temperature range over 200 K, the observed thermal conductivities depend on the number of filaments. It has been inferred to be caused by a thermal radiation effect.…”

“…The details are described in a previous article. 40 The temperature dependence of the thermal conductivity of the ramie fibers with ␥-ray treatments in the fiber direction from 10 to 150 K is shown in Figure 10. The thermal conductivities of all the samples decrease with decreasing temperature.…”

Thermal Conductivity of High-Strength Polyethylene Fiber and Applications for Cryogenic Use

“…For example, thermal conductivity of ramie fiber in fiber direction changes by the following treatments, drawing in water (water treatment), irradiation with γ-rays (γ-rays treatment), and vapor-phase-formaldehyde treatments (VP-HCHO treatment). Those treatments induce the extension, chain scission, and bridging to molecular chains as shown in Figure 3 [26][27][28]. The thermal conductivities of the ramie fibers before and after those treatments are shown in Figure 4 [26][27][28].…”

“…Those treatments induce the extension, chain scission, and bridging to molecular chains as shown in Figure 3 [26][27][28]. The thermal conductivities of the ramie fibers before and after those treatments are shown in Figure 4 [26][27][28].…”