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

Abstract

ABSTRACT:To understand the influence on the thermal conductivity by the length of the molecular chain in the polymer fiber, the thermal conductivity and thermal diffusivity of ramie fibers and those irradiated by ␥ rays, which induced molecular chain scission of cellulose, were investigated in a range of low temperatures. The degrees of polymerization, crystallinities, and orientation angles of ramie fibers and those irradiated by ␥ rays (␥-ray treatment) were measured by the solution viscosity method, solid-state NMR, and X-ray diffraction. Only the degree of polymerization decreased with the ␥-ray treatment, and the crystallinities and orientation angles were almost independent of the ␥-ray treatment. The thermal conductivities of the ramie fibers with and without ␥-ray treatments decreased with decreasing temperature. The thermal diffusivities of the ramie fibers and those irradiated by ␥ rays were almost constant from 250 to 100 K, increased slightly with the temperature decreasing from 100 to 50 K, and increased rapidly with the temperature decreasing below 50 K. The thermal conductivity and thermal diffusivity of the ramie fibers decreased with the ␥-ray treatment. The mean free path of the phonon in the ramie fibers was reduced by the ␥-ray treatment. This decrease of the thermal diffusivity and thermal conductivity was explained by the reduction of the mean free path of the phonon by molecular chain scission with ␥ rays.

Extremely oriented tunicin whiskers in poly(vinyl alcohol) nanocomposites

“…PVA seems to result in good interfacial adhesion or interaction with CWs, yielding simultaneous orientation of both components during drawing. Using the same crystal plane (102) of ramie fiber, a natural cellulose‐rich fiber with high degree of crystal orientation,43 a π value of 0.88 was obtained. This indicates that an extreme orientation of cellulose crystals higher than that of a ramie fiber is achieved in our composite fibers.…”

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].…”

Effects of γ-ray radiation grafting on aramid fibers and its composites

“…The polymer materials include polypropylene [17], polyethylene terephthalate [18], polyNIMMO [poly(3-nitratomethyl-3-methyloxetane)] [19], polyurethane [20], poly(ethylene-co-tetrafluoroethylene) (ETFE) film [21], polyethylene film [22], polyethylene terephthalate (PET) film [23], the high-density polyethylene (HDPE) film [24], ramie fibers [25], carbon fibers [26], PBO fibers [27], ultra-highmodulus-polyethylene fibers (UHMPE) [28], ultra-high-molecular-weight-polyethylene fibers (UHMWPE) [29] and so on. Consequently g-ray radiation seems to be an alternative technique for the surface treatment of aramid fibers.…”