Izabella Krucińska

DSC investigations of polyamide 6 in hybrid GF/PA 6 yarns and composites

Abstract Glass/PA 6 composites were manufactured from specially designed hybrid yarns. The hybrid yarns were produced by three different spinning systems: friction spinning, ring twisting and pneumatic texturing. Each of these systems gives a different structure of the yarn and a different level of blending of the reinforcing and thermoplastic fibres. The crystallization and melting behaviour of PA 6 in the yarns and the composites were studied by differential scanning calorimetry. The different structure of the hybrid yarns leads to differences in the crystallinity of PA 6 in the yarns and the composites. The mechanical properties of the thermoplastic yarns and the composites are influenced, among other factors, by the crystal structure of the polymer.

Correlation Between Copolymer Characteristics, Conditions of Fiber Formation, and Mechanical Properties of PAN Carbon Fiber Precursor: Part I: Effect of Copolymer Intrinsic Viscosity Distribution on Mechanical Properties

We present an..analysis of the copolymer molecular weight distribution effect on the mechanical properties of polyacrylonitrile (PAN) fibers. The conditions of the fiber forming process are constant for each of six copolymers. The analysis shows that the highest values of Youngs modulus are obtained for copolymers that contain 70% by weight of fractions having intrinsic viscosities that range from 1 and 3. The tensile strength of the fibers depends on deformations occurring during the fiber forming process rather than on the molecular weight distribution of the copolymer.

Influence of the calender temperature on the crystallization behaviors of polylactide spun-bonded non-woven fabrics:

In this paper the influence of calender temperature on the crystallization behavior of polylactide (PLA) non-woven fabrics during their manufacturing by the spun-bonding technique is described. Non-woven samples were studied by wide-angle X-ray diffraction, differential scanning calorimetry and birefringence. In addition, physical–mechanical properties of the non-woven fabrics were determined. The results are discussed in terms of structural changes of PLA and meso-phase content during the calendering process in the temperature range 70–130℃. The rebuilding of the supermolecular structure of the investigated samples of PLA fabrics under the influence of increasing calender temperature is observed in terms of the disorder-to-order phase transition (ά to α form) during heating around 110℃, and increased degree of crystallinity up to 100℃. The presented structural rebuild of PLA explains observed changes of physical–mechanical properties of the non-woven fabrics obtained at different calendering temperatures. During calendering above 100℃, thermal degradation of PLA occurs at the point of contact between the non-woven fabrics and the calender rollers.

The effect of raw material composition of clothes on selected physiological parameters of human organism

Present studies were undertaken to determine the influence of clothing made from natural and synthetic fibres and their blends, which transiently covered a human body, on the activity of motor units of forearm muscles determined by electromyographic method. The clothes made out of 100% linen, 100% polyester (PES) and their blends with a different percentage of both kinds of raw material were examined. The studies proved that there were considerable changes in the parameters of skin–clothes microclimate that depend on the share of polyester fibres in the blends with linen. These changes can be the reason of differences in electromyographic records of motor unit activity of the muscles covered by tested clothes, even if the volunteers taking part in this experiment had not been doing any physical exercises. The results of tests showed that clothing made from polyester fabric was a reason of changes in muscle electromyograph (EMG) records of the wearers, which indicated occurrence of desynchronization of motor units. The clothes made of fabrics composed of polyester and linen fibres higher than 25% did not cause desynchronization of motor units in healthy muscles while providing the wearer with optimal comfort of using.

Fibrous Polymeric Composites Based on Alginate Fibres and Fibres Made of Poly-ε-caprolactone and Dibutyryl Chitin for Use in Regenerative Medicine

This work concerns the production of fibrous composite materials based on biodegradable polymers such as alginate, dibutyryl chitin (DBC) and poly-ε-caprolactone (PCL). For the production of fibres from these polymers, various spinning methods were used in order to obtain composite materials of different composition and structure. In the case of alginate fibres containing the nanoadditive tricalcium phosphate (TCP), the traditional method of forming fibres wet from solution was used. However in the case of the other two polymers the electrospinning method was used. Two model systems were tested for biocompatibility. The physicochemical and basic biological tests carried out show that the submicron fibres produced using PCL and DBC have good biocompatibility. The proposed hybrid systems composed of micrometric fibres (zinc and calcium alginates containing TCP) and submicron fibres (DBC and PCL) meet the requirements of regenerative medicine. The biomimetic fibre system, the presence of TCP nanoadditive, and the use of polymers with different resorption times provide a framework with specific properties on which bone cells are able to settle and proliferate.

Investigation Of Sound Absorption Properties Of Bark Cloth Nonwoven Fabric And Composites

Abstract The quest for sound-absorbing materials that are not only environmentally friendly, but also sustainable is the foremost reason for natural fibre-acoustic materials. Bark cloth is a natural non-woven fabric that is largely produced from Ficus trees. An exploratory investigation of bark cloth a non-woven material and its reinforcement in epoxy polymer composites has been fabricated and investigated for the sound absorption properties so as to find the most suitable applications and also to see whether bark cloth can be used in some applications in place of man-made fibres. Three types of material species were investigated with their respective composites. The fibre morphology showed bark cloth to be a porous fabric that showed promising sound absorption properties at higher frequencies. The sound absorption results of four-layer material selections of Ficus natalensis, Ficus brachypoda and Antiaris toxicaria bark cloth showed sound absorption coefficient of 0.7; 0.71 and 0.91 at f > 6400 Hz, respectively. The bark cloth reinforced laminar epoxy composites had reduced sound absorption coefficients, which ranged from 0.1 to 0.35, which was attributed to decreased porosity and vibration in the bark cloth fibre network.

A smart fabric with increased insulating properties

A new textile fabric prototype providing more heat insulation composed of shape-memory elements was investigated. The shape-memory elements in the form of spirals characterized by two-way action were made of nitinol (NiTi) one-way wires with the inner state transition temperature of 35℃. The fabric prototype developed was made of three layers of nonwovens manufactured from the blends of flax and steel fibers and the two interlayers included spirals, made from NiTi or a reference copper (Cu) wire. The inner layer (heater) was heated by electrical current. The external prototype layers imitated the fabric. Mirrors and an infrared camera were used to measure the thermal properties. The temperature of the external surfaces was analyzed as a function of heating time. At approximately 35℃, a change in the curve of the dependence of temperature on the heating time of the prototype with NiTi elements could be observed; the rate of the temperature increase began to decrease. The width of the interlayer with air and NiTi elements increases by approximately 2.5 mm during heating. The observed phenomenon is caused by the expansion of the NiTi spirals and did not occur with the prototype composed of non-active reference Cu elements. In the final second of heating, the temperature on the external surface of the prototype with NiTi elements was lower by 2–3℃ than that on the prototype with Cu elements. A theoretical model of the system was developed and a satisfactory agreement between the experimental and theoretical results was obtained.

Effect of processing variables on the thermal and physical properties of poly(L-lactide) spun bond fabrics

In this paper, the influence of the take-up velocity (Vt–u) of fibers on the molecular ordering and ά – α form transition of polylactide (PLA) non-woven fabrics during their manufacturing by spun-bonding is described. Non-woven samples were studied by wide-angle X-ray diffraction, differential scanning calorimetry and Fourier transform infrared spectroscopy. In addition, the physical and mechanical properties of the non-woven fabrics were determined. The results are discussed in terms of the structural changes of the PLA and the meso-phase content during the spun-bonded non-woven fabric forming process. This technological process includes preliminary molecular ordering of the PLA fibers in a downstream spinning block and crystallization on a calender system at a temperature higher than the glass transition. The molecular ordering of the investigated PLA fabric samples under different technological conditions was observed as follows: creation of the meso-phase and a disorder-to-order phase transition (ά to α form) during heating to approximately 110℃ and an increase in the degree of crystallinity for take-up velocities higher than 1400 m/min. The structural changes of the PLA explain the observed changes in the physical and mechanical properties of the non-woven fabrics obtained under different technological conditions.

Investigation of the Influence of PLA Molecular Structure on the Crystalline Forms (α’ and α) and Mechanical Properties of Wet Spinning Fibres

In this paper, the influence of the molecular structure of polylactide (PLA)—characterised by its molar mass and content of d-lactide isomer—on the molecular ordering and α’–α form transition during fibre manufacturing by the wet spinning method is described. Fibres were studied by wide-angle X-ray diffraction (WAXD) and differential scanning calorimetry (DSC). Additionally, the physical and mechanical properties of the fibres were determined. This study also examines the preliminary molecular ordering and crystallisation of PLA fibres at various draw ratios. The performed experiments clearly show the dependence of the molecular ordering of PLA on the molar mass and d-lactide content during the wet spinning process. The fibres manufactured from PLA with the lowest content of d-lactide and the lowest molar mass were characterised by a higher tendency for crystallisation and a higher possibility to undergo the disorder-to-order phase transition (α’ to α form). The structural changes in PLA explain the observed changes in the physical and mechanical properties of the obtained fibres.

Sound-absorbing green composites based on cellulose ultra-short/ultra-fine fibers

In this paper studies on sound absorption of the thermoplastic composites on the basis of waste natural fibers are presented. Cotton fibers and cellulose ultra-short and ultra-fine fibers obtained from flax fibers following enzymatic and additional mechanical treatment were used as the components of polylactide composites, and their influence on sound absorption behavior was investigated. The composites were obtained from a pressing process of fibrous multilayer structures. The sound absorption properties of three types of composites were compared: composites reinforced by cotton fibers, composites reinforced by cellulose ultra-short and ultra-fine fibers, and composites reinforced by cotton fibers and cellulose ultra-short and ultra-fine fibers. The role of cellulose ultra-short and ultra-fine fibers in changing the sound absorption properties of composites was determined. It has previously been shown that using natural fibers with a thermoplastic polymer results in increased sound absorption. The best improvement of sound absorption can be obtained by combining cotton fibers and cellulose ultra-short and ultra-fine fibers, especially nanofibers, as a reinforcement.