Correlating the fineness and residual gum content of degummed hemp fibres

It is well known residual gum exists in degummed or retted hemp fibres. Gum removal results in improvement in fibre fineness and the properties of the resultant hemp yarns. However, it is not known what correlation if any exists between the residual gum content in retted hemp fibres and the fibre fineness, described in terms of fibre width in this paper. This study examined the mean width and coefficient of variation (CV) of fibre width of seventeen chemically retted hemp samples with reference to residual gum content. The mean and CV of fibre width were obtained from an Optical fibre diameter analyser (OFDA 100). The linear regression analysis results show that the mean fibre width is directly proportional to the residual gum content. A slightly weaker linear correlation also exists between the coefficient of variation of fibre width and the residual gum content. The strong linear co-relation between the mean of fibre width and the residual gum content is a significant outcome, since testing for fibre width using the OFDA is a much simpler and quicker process than testing the residual gum content. Scanning Electron Microscopy (SEM) reinforces the OFDA findings. SEM micrographs show a flat ribbon like fibre cross-section hence the term “fibre width” is used instead of fibre diameter. Spectral differences in the untreated dry decorticated skin samples and chemically treated and subsequently carded samples indicate delignification. The peaks at 1370 cm⁻¹, 1325 cm⁻¹, 1733 cm⁻¹, and 1600 cm⁻¹ attributed to lignin in the untreated samples are missing from the spectra of the treated samples. The spectra of the treated samples are more amine-dominated with some of the OH character lost.

A new method of evaluating the fineness and residual gum content of hemp fibres

The demand for eco-friendly apparel and technical textiles has led to a resurgence of interests in bast fibres such as hemp. The lack of fast and objective evaluation of the quality attributes of bast fibres has been a major barrier to the advancement of the bast fibre industry. One of the most important quality attributes of a fibre is its fineness. For bast fibres, the fibre fineness measurement can also reflect the degree of fibre separation during retting or degumming. The traditional method of evaluating the fineness and residual gum content of bast fibres is a very tedious process. In this paper, degummed hemp fibres have been measured for fineness on an Optical Fibre Diameter Analyser (OFDA), and the results have been co-related with the residual gum content in the fibre samples. Since hemp fibres do not have a circular cross section, it is the width of the fibre that gets measured by the OFDA instrument, and this width has been used as an indication of the fibre fineness in this paper. The findings from this study suggest that the optical method can provide a fast and objective way of evaluating the fineness of hemp fibres, and that there is a good correlation between the fibre „width‟ measurement and the residual gum content.

Needleless electrospinning : influences of fibre generator geometry

The fibre generator shape and dimension are key factors affecting the needleless electrospinning process and fibre fineness. In this work, cylinder with rounded rim, disc and ball were used as spinnerets to electrospin polyvinyl alcohol and polyacrylonitrile solutions. A finite element method was used to analyse how the spinneret geometry affected the electric field generated during electrospinning and the associated changes in fibre diameter and productivity. For cylinder spinnerets, increasing the rim radius reduced the discrepancy of electric field intensity between the cylinder end and middle area, which affected the fibre productivity. The electrospinning failed to operate when the rim radius was over 20 mm. With decreasing cylinder diameter, the electric field intensity in the middle area increased, improving the fibre productivity. Thinner disc spinnerets increased the electric field intensity, resulting in finer nanofibres and higher productivities. Ball spinnerets produced evenly distributed electric field, but failed to electrospin fibres when the diameters were below 60 mm. It has been found that strong and narrowly distributed electric field in the fibre-generating area can significantly facilitate the mass production of quality nanofibres.

Preparation of nanofibre yarns from electrospun nonwoven strips

From ancient to modern time, humans have been trying to use finer fibres to make fibrous products for various purposes and believing that finer fibres have better aesthetic qualities. So far, the commercial fibres have been reduced to microns in diameter, but it seems difficult to further reduce the fibre fineness to submicrons using conventional fibre-making techniques.
Electrospinning is a promising technique to produce continuous fibres with diameters on nanometre scales. This technique involves stretching a polymer fluid under a strong electric field into fine filaments, which are deposited randomly on the electrode collector forming a nonwoven nanofibre mat in most cases. Despite considerable efforts in exploring the applications of electrospun nanofibres in non-fibrous fields [1], very limited work has been conducted on using this material to process mechanically robust nanofibre yarns [2,3].

Recent research on natural fibres and textiles

This paper provides an overview of recent research on a range of natural fibres and textiles. The focus is on work carried out at Deakin University’s Centre for Material and Fibre Innovation, which is a multidisciplinary research centre with over 100 researchers. The fibres include hemp, wool, silk, and alpaca fibres. Research on yarns, fabrics, and fine powders made from wool and silk fibres are briefly discussed also.

The within-fibre diameter variation of wool has been examined systematically, which highlights the importance of this hard-to-measure fibre attribute. A relationship between hemp fibre fineness and residual gum content has been established, which provides a rapid means of assessing the residual gum content in the degummed hemp fibres. Silk and wool fibres have been converted into ultrafine powders for advanced applications. The Resistance to Compression (RtC) behaviour of wool and alpaca fibres has been closely examined, which challenges the belief that RtC is a good indicator of fibre softness. Ways of reducing the hairiness of natural fibre yarns, predicting the pilling propensity of wool knits, and functionalising fabrics for superhydrophobicity and photochromic or colour changing effects are discussed.

Evaluation of bast fibre retting systems on hemp

In this paper the effect of eight different retting methods on decorticated hemp skins were analyzed. The methods were taken from six publications that looked at the retting of different bast fibres such as ramie, flax and kenaf. The fibres were batch retted in a package dye-vat at 100oC under 2 bar of pressure. The rinsed fibres were opened twice using a Shirley cotton trash separator. The opened fibre was assessed for fibre width, fibre width variation, colour and handle. It was found that the fibre that had undergone chemical retting with 7% Sodium Hydroxide (NaOH) and 0.5% Sodium Sulphite (Na2SO3) had the best diameter (18.39 micron) and the best coefficient of variation of diameter (57.32%). The fibre that was processed with 7% Sodium Hydroxide (NaOH) and 0.5% Sodium Sulphite (Na2SO3) had the whitest colour (YI D1925 = 31.61). The method treated with 1% Sodium Hydroxide (NaOH) and 1% Sodium Sulphite (Na2SO3) had the softest handle and the method treated with 1% Sodium Hydroxide (NaOH) and pre-rinsed with 0.3% Hydrochloric Acid (HCl) showed the best conversion of decorticated skins into spin able fibre (33.9% of dry green skins). It was decided that method treated with 1% Sodium Hydroxide (NaOH) and pre-rinsed with 0.3% Hydrochloric Acid (HCl) had the best fineness of fibre micron, conversion to spin able fibre (33.9% of dry green skins), whitest colour (YI D1925 = 36.13) and softest handle for the cost of chemicals involved.

Eri silk fibre attributes and sliver preparation

Eri silk produced by Philosamia cynthia ricini silkworm is a fibre not well-known to the silk industry, in spite of the fact that Eri silk is finer, softer, and has better mechanical and thermal properties than most animal fibres. Eri silk has a high commercial potential, as the host plants of Eri silk worms are widespread in diverse geographical locations, and the worms also have a higher degree of disease resistance than most other silk worms. Mills are often not aware of the properties of Eri for designing appropriate end products. Thus, Eri silk yarn is traditionally produced by hand spinning, and Eri silk usually ends up as material for handwoven shawls. The potential for bulk fibre processing and the development of soft luxurious novel Eri silk products is yet to be discovered. To better understand the material and its processing behaviour, Eri silk was characterised and cocoons were processed into tops through degumming, opening, and cutting filaments into different lengths, followed by a worsted spun silk processing route. Fibre properties such as fineness, crimp, strength and length at different processing stages up to combed tops were measured. The results indicate that staple Eri silk can be processed via the worsted topmaking route, using a cut length of 200 mm or 150 mm for filament sheets prepared from degummed cocoons.

Decision support in using fibre reinforced polymer (FRP) composites in rehabilitation of concrete bridge structures

This paper compares and reviews the recommendations and contents of the guide for the design and construction of externally bonded FRP systems for strengthening concrete structures reported by ACI committee 440 and technical report of Externally bonded FRP reinforcement for RC structures (FIB 14) in application of carbon fiber reinforced polymer (CFRP) composites in strengthening of an aging reinforced concrete headstock. The paper also discusses the background, limitations, strengthening for flexure and shear, and other related issues in use of FRP for strengthening of a typical reinforced concrete headstock structure such as durability, de-bonding, strengthening limits, fire and environmental conditions. A case study of strengthening of a bridge headstock using FRP composites is presented as a worked example in order to illustrate and compare the differences between these two design guidelines when used in conjunction with the philosophy of the Austroads (1992) bridge design code.

Corneal confocal microscopy : a novel means to detect nerve fibre damage in idiopathic small fibre neuropathy

Patients with idiopathic small fibre neuropathy (ISFN) have been shown to have significant intraepidermal nerve fibre loss and an increased prevalence of impaired glucose tolerance (IGT). It has been suggested that the dysglycemia of IGT and additional metabolic risk factors may contribute to small nerve fibre damage in these patients. Twenty-five patients with ISFN and 12 aged-matched control subjects underwent a detailed evaluation of neuropathic symptoms, neurological deficits (Neuropathy deficit score (NDS); Nerve Conduction Studies (NCS); Quantitative Sensory Testing (QST) and Corneal Confocal Microscopy (CCM)) to quantify small nerve fibre pathology. Eight (32%) patients had IGT. Whilst all patients with ISFN had significant neuropathic symptoms, NDS, NCS and QST except for warm thresholds were normal. Corneal sensitivity was reduced and CCM demonstrated a significant reduction in corneal nerve fibre density (NFD) (Pb0.0001), nerve branch density (NBD) (Pb0.0001), nerve fibre length (NFL) (Pb0.0001) and an increase in nerve fibre tortuosity (NFT) (Pb0.0001). However these parameters did not differ between ISFN patients with and without IGT, nor did they correlate with BMI, lipids and blood pressure. Corneal confocal microscopy provides a sensitive non-invasive means to detect small nerve fibre damage in patients with ISFN and metabolic abnormalities do not relate to nerve damage.

An investigation of rail condition monitoring by Fibre Bragg Grating sensors

Condition monitoring on rails and train wheels is vitally important to the railway asset management and the rail-wheel interactions provide the crucial information of the health state of both rails and wheels. Continuous and remote monitoring is always a preference for operators. With a new generation of strain sensing devices in Fibre Bragg Grating (FBG) sensors, this study explores the possibility of continuous monitoring of the health state of the rails; and investigates the required signal processing techniques and their limitations.