Influence of pH on hygral expansion, relaxation shrinkage and extensibility of wool fabric

The standard tests for relaxation shrinkage and hygral expansion of wool fabric take no account of pH. It is shown in this work that the pH of the solution in which wool fabric is relaxed as part of the procedure for measuring dimensional properties has a significant influence on the results. At around pH 4.8, which is close to the isoelectric point of wool, the hygral expansion reaches its greatest value and drops at both lower and higher pHs. A similar relationship between pH and extensibility of wool fabric was observed. Values of relaxation shrinkage were found to be dependant on pH. The reasons for the pH dependence of dimensional properties are discussed and these include changes in wool fiber swelling, yarn crimp and polymer relaxation phenomena with changes in pH.

Shrinkage induced stretchable micro-wrinkled reduced graphene oxide composite with recoverable conductivity

A novel thermo-mechanical shrinking method is reported to fabricate a three dimensional (3D) stretchable and highly conductive micro-wrinkled reduced graphene oxide (MWrGO) supported on an elastic polydimethylsiloxane (PDMS) substrates. This 3D rGO architecture not only increases the specific area for more electrons to pass through but also bestows stretchability to the conductive pathway. The structural change of micro-wrinkles has been monitored by an in situ straining microscopy. The electrical conductivity of the samples remained fairly constant and stayed above 25 S/m under low deformation (no more than 30% strain) for up to 500 mechanical stretching-release cycles. Additionally, the MWrGO/PDMS composite can be stretched bi-axially because the shrinking process itself is isotropic. This MWrGO based stretchable composite with stable electrical properties and long life span could form a new platform of stretchable electronics.

A physarum-inspired vacant-particle model with shrinkage for transport network design

Physarum can form a higher efficient and stronger robust network in the processing of foraging. The vacant-particle model with shrinkage (VP-S model), which captures the relationship between the movement of Physarum and the process of network formation, can construct a network with a good balance between exploration and exploitation. In this paper, the VP-S model is applied to design a transport network. We compare the performance of the network designed based on the VP-S model with the real-world transport network in terms of average path length, network efficiency and topology robustness. Experimental results show that the network designed based on the VP-S model has better performance than the real-world transport network in all measurements. Our study indicates that the Physarum-inspired model can provide useful suggestions to the real-world transport network design.

Free and restrained shrinkage behaviours of OPC and slag concretes with admixed polypropylene fibres

This paper presents the results of an investigation that studied the effects of admixed polypropylene (PP) fibres on the long-term drying shrinkage of hardened concrete. Five concrete mixtures, made with 100% Ordinary Portland Cement (OPC) as the binder and containing different volume fractions of PP fibre (0%, 0.05%, 0.1%, 0.2% and 0.5%) were tested. Also, three concrete mixtures were made with 65 % slag-blended cement binder incorporating 0% and 0.2% volume fraction of PP. The results show higher water loss and higher drying shrinkages in concretes that incorporate PP fibres than concrete without fibre. The results of early age cracking tendency of slag concrete, with and without fibre, under fully restrained and drying conditions, show that that PP fibre concrete had higher cracking tendency than concrete without fibre. Higher cracking tendency of PP fibre concrete was due to higher drying shrinkage and elastic moduli.

Body shrinkage due to Arctic warming reduces red knot fitness in tropical wintering range

Reductions in body size are increasingly being identified as a response to climate warming. Here we present evidence for a case of such body shrinkage, potentially due to malnutrition in early life. We show that an avian long-distance migrant (red knot, Calidris canutus canutus), which is experiencing globally unrivaled warming rates at its high-Arctic breeding grounds, produces smaller offspring with shorter bills during summers with early snowmelt. This has consequences half a world away at their tropical wintering grounds, where shorter-billed individuals have reduced survival rates. This is associated with these molluscivores eating fewer deeply buried bivalve prey and more shallowly buried seagrass rhizomes. We suggest that seasonal migrants can experience reduced fitness at one end of their range as a result of a changing climate at the other end.

Prediction error property of the Lasso Estimator and its generalization

The lasso procedure is an estimator-shrinkage and variable selection method. This paper shows that there always exists an interval of tuning parameter values such that the corresponding mean squared prediction error for the lasso estimator is smaller than for the ordinary least squares estimator. For an estimator satisfying some condition such as unbiasedness, the paper defines the corresponding generalized lasso estimator. Its mean squared prediction error is shown to be smaller than that of the estimator for values of the tuning parameter in some interval. This implies that all unbiased estimators are not admissible. Simulation results for five models support the theoretical results.

Self-crimping bicomponent nanofibres electrospun from polyacrylonitrile and elastomeric polyurethane

Two polymer solutions were brought together via a microfluidic device and subjected to an electrospinning process. The two polymer solutions flowed into the microfluidic channel side-by-side with very little intermixing due to their laminar nature. High speed stretching of the polymer solutions resulted in side-by-side bicomponent fibres. The electrospun nanofibres exhibited an extremely high propensity to self-crimp when an elastomeric polymer (polyurethane) and a normal polymer (polyacrylonitrile PAN) were involved in the electrospinning process. The formation of self-crimping fibre morphology was attributed to the differential shrinkage of the two polymers.

Squeeze pin implementation in a high pressure die casting

This paper discusses the implementation of hydraulically operated squeeze pins to reduce porosity formation in cast aluminium bearing caps. Two complete sets are cast in an eight-cavity die with a 2000t cold chamber high pressure die casting machine. The initial die configuration used a sliding core assembly with stationary pins to core a through hole in a thick section of the front cam caps. This configuration resulted in high post machining scrap rates, primarily due to porosity associated with solidification shrinkage. Replacement of the sliding core assembly with a squeeze pin unit substantially reduced shrinkage porosity in the critical region, with consequent reductions in the scrap rate. The squeeze pins are actuated 1.5s after the piston reaches the high shot changeover position, but can be successfully engaged between I and 3.5 seconds after high shot changeover. Density measurements and visual inspection confirmed the substantial improvement in porosity levels in the critical region of the castings.

The effects of ultrasonic agitation in laundering on the properties of wool fabrics

This paper investigates the use of ultrasonic agitation as a method for reducing felting and area shrinkage during the laundering of wool fabric. Work was conducted to evaluate the changes in fibre and fabric properties after repeated exposure to ultrasonic agitation, and also the effectiveness of ultrasonic treatment to remove common stains. Fabric colour, appearance, tensile strength, dimensional stability and thickness were measured before and after each test. Ultrasonic agitation produced fine cracks in the scale structure of the fibre, but these had negligible effects on the strength and colour when compared to hand washing. Ultrasonic agitation caused less fibre migration than hand washing, with a reduced rate of thickness increase and felting. Ultrasonic agitation increased the level of stain removed from the fabric when compared with hand washing.

The effect of fabric strain during pressure steaming on fabric dimensional properties

It is shown that tension applied to fabric which is then permanently set by steaming under pressure for a short time has a significant effect on fabric dimensional properties. Increasing levels of stretch applied to fabric before pressure steaming resulted in decreases in fabric hygral expansion and relaxation shrinkage and also lowered fabric shrinkage that resulted from permanent setting. The setting conditions resembled those used in conventional pressure decatising, and it is suggested that in batch decatising, precise control of the length and width of fabric as it is batched up with the wrapper before steaming under pressure could enable predictable changes in fabric dimensions, relaxation shrinkage and hygral expansion to be obtained.

The dimensional and mechanical properties of wool/polyester fabrics made from vortex and ring-spun yarns

Fabric woven from wool/polyester (PES) Murata vortex spun (MVS) blend yarn is a commercially viable proposition particularly on the basis of advantageous wear-resistant properties, compared with fabric made from traditional worsted ring-spun yarn. However, in some early industrial trials with fabric made from 45/55-blend wool/PES MVS yarn, significantly greater relaxation shrinkage was found relative to comparable worsted ring-spun fabric. It was noted at the time that the amount of relaxation shrinkage in MVS fabric could be reduced to a large extent by using steamed MVS yarn.

In this study, the extent of variations in the dimensional and mechanical properties of fabric samples woven from a combination of steamed and unsteamed MVS yarn and equivalent worsted ring-spun yarn is examined. In general, greater hygral expansion and relaxation shrinkage were found in loom-state fabrics made from unsteamed MVS yarns, whereas the fabric made from steamed MVS and ring-spun yarns gave relatively low levels of relaxation shrinkage and hygral expansion. Permanent setting of fabrics, by pressure steaming, was found to be more effective than yarn pre-steaming in reducing relaxation shrinkage levels of fabrics made from unsteamed MVS yarn. After pressure steaming, all fabrics showed similar levels of relaxation shrinkage and hygral expansion.

Permanent setting of the fabrics, by pressure steaming, resulted in similar levels of relaxation shrinkage and hygral expansion, irrespective of the yarn production method; relaxation shrinkage fell to around 1% and hygral expansion increased by about 1%, relative to the loom-state samples. MVS fabrics were relatively heavier and fuller and had a firmer handle than the worsted ring-spun fabrics, reflecting the greater fabric weight, thickness and shear rigidity measured on these fabrics. These attributes are associated with different structures of the worsted ring-spun and MVS yarns used to make the fabrics.