A novel method to assess degree of crystallinity of aramid filament yarns

Abstract

An equation was developed to predict the morphology of aramid fibers using dissolution time (t) data of Kevlar and Nomex multifilament yarns, which were heat set at various temperatures. The degree of crystallinity of the fibers was characterized by WAXS and the dissolution time of the samples was measured. The degree of crystallinity and dissolution time of the fibers increases with both heat treatment time and heat treatment temperature. The coefficient of correlation between 1/t and the X-ray degree of crystallinity was found to be À0.88 for Nomex aramid and À0.95 for Kevlar aramid multifilament yarns. The dissolution times of completely amorphous and fully crystalline fibers can be predicted using regression and were substituted in a novel equation to characterize the morphology of the aramid fibers. New equations were proposed to assess the degree of crystallinity of the aramid multifilament yarns. For Nomex, the equation is c = [(0.053) À (1/t)]/(0.00054). For Kevlar, the equation is c = [(0.12) À (1/t)]/(0.0015).

Deposition of carbon nanotubes onto aramid fibers using as-received and chemically modified fibers

“…The modification of the aramid fiber surface (with FSC previously removed, see section 2.3.1) was performed by immersing the yarn in a 3.0 M mixture of HNO3 and H2SO4 for 1 h. Then, the aramid fibers were washed with 1.5 L of distilled water. This treatment is expected to affect the amorphous phase of the aramid fibers (< 24 %) through amide bond opening situated at the backbone of the fiber structure and the generation of amide and carboxyl groups in some fiber sections, see Figure 1 [26,27]. These functional groups can interact through hydrogen bonds with the carboxyl and hydroxyl groups of the previously oxidized MWCNTs [28].…”

“…The subsequent inmersion in distilled water is expected to convert the sulfuryl chloride groups into sulfonic groups (SO3H), as discussed in [4]. This treatment is also expected to modify the amorphous phase of the aramid fiber surface [26,27]. The central amide group of the fiber can separate due to sulfonation yielding carboxylic functional groups (see Figure 2), which are expected to interact with the OH, COOH and CO functional groups of the oxidazed MWCNTs through hydrogen bonding [28].…”

Study on Crystallization Behaviors and Properties of F-III Fibers during Hot Drawing in Supercritical Carbon Dioxide

“…Hot-drawing treatment at a temperature above the Tg of AFs has accelerating effects on the crystallinity and degree of orientation of AFs [25,26,27]. The crystallization behavior can be employed as an important index to reflect the mechanical performance of AFs to some extent.…”

New Approach for Optimising the Impregnations of Individual Batches of Aramid Fabrics

“…Input data are represented as vectors X1-X5 corresponding to 5 columns in the design matrix with 32 rows related to the 32 setting points (see Table 2). A special architecture of error back-propagation neural network was used (5,2,5), in which the data are fed into the 5-nodes input layer and then transferred through the 2-nodes hidden layer (compared to a bottleneck) to the 5-nodes output layer. The number of nodes in the input and output layers correspond to the number of independent variables which is equal to 5 (number of factors in DOE).…”

“…e technology of AuTx has a large potential for development [1]. Nowadays the high interest for goods produced from aramide bres and fabrics has been proved by numerous research [2][3][4][5][6][7][8]. In this paper we examined the impregnation processes of high performance fabrics made from aramid bres designed for the manufacturing of athletic sportswear for extreme sports using the neural network mapping technique when searching for optimal conditions regarding the studied process.…”