Binder fiber distribution and tensile properties of thermally point bonded cotton‐based nonwovens

Cotton‐based nonwovens are generally produced by carding and then bonding. One of the most important characteristics of nonwoven materials is the uniformity of their structure and properties. However, the carded webs always have irregularities caused by processing and material variables. The binder fiber distribution in carded cotton‐based nonwoven fabrics was analyzed based on the crystallization behavior of one of the components of the binder fibers by DSC. The effects of process parameters, such as bonding temperature and binder fiber component, on the uniformity were discussed in detail in this article. Also, the relationship of binder fiber distribution and the strip tensile property and single‐bond tensile strength were investigated. The results showed that if the binder fibers were not well distributed in the fabric, it would be hard to get the same trend of temperature effect on tensile property for the strip and single‐bond tests. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 91: 3148–3155, 2004     

玻璃纤维非织造布

非织造布是用化学、机械、加热或溶剂处理方式把纤维交缠形成的织物状材料。国际上的玻璃纤维非织造布在玻璃纤维产品中占有较大比例,应用范围颇广。文中讲述了玻璃纤维非织造布的主要类型及它们的应用范围和市场动态,借此展示玻璃纤维的宽泛用途和强大生命力。     

Use of wet‐laid techniques to form flax‐polypropylene nonwovens as base substrates for eco‐friendly composites by using hot‐press molding

The wet‐laid process with flax (base) and polypropylene (binder) fibers has been used to obtain nonwovens for further processing by hot‐press molding. Mechanical characterization of nonwovens has revealed that slight anisotropy is obtained with the wet‐laid process as better tensile strength is obtained in the preferential deposition direction. The thermo‐bonding process provides good cohesion to nonwovens, which is critical for further handling/shaping by hot‐press molding. Flax:PP composites have been processed by stacking eight individual flax:PP nonwoven sheets and applying moderate temperature and pressure. As the amount of binder fiber is relatively low (<30 wt%) if compared with similar systems processed by extrusion and injection molding, it is possible to obtain eco‐friendly composites as the total content on natural fiber (flax) is higher than 70 wt%. Mechanical characterization of hot‐pressed flax:PP composites has revealed high dependency of tensile and flexural strength on the total amount of binder fiber as this component is responsible for flax fiber embedment which is a critical parameter to ensure good fiber–matrix interaction. Combination of wet‐laid techniques with hot‐press molding processes is interesting from both technical and environmental points of view as high natural fiber content composites with balanced properties can be obtained. POLYM. COMPOS., 2012. © 2011 Society of Plastics Engineers     

Polymer adhesion in heat‐treated nonwovens

Polymer adhesion and sintering in compound nonwovens was studied. Nonwovens containing a mixture of binding bi‐component (BICO) fibers embedded in a fibrous matrix were heated to melt the outer shell of BICO fibers and interlock the matrix to create stiff load‐bearing surfaces. It was found that stiffness depends on heat‐treatment regimes. In low‐temperature regimes, BICO fibers melt, but do not fully flow and encase the surrounding filler matrix. At sufficiently high temperatures, the shells of BICO fibers melt and flow which results in encasing the neighboring filler fibers. This results in an abrupt increase in the nonwoven stiffness which is independent of heat‐treatment temperature. At significantly high temperatures, the filler matrix fibers sinter to each other leading to a further increase in stiffness. The experiments were conducted with co‐polymers frequently used in the shells of BICO to demonstrate the interlocking mechanism characteristic of these compound nonwovens. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46165.     

Effects of porosity,fiber size,and layering sequence on sound absorption performance of needle‐punched nonwovens

The relationships between the material parameters, i.e., the fiber fineness, porosity, areal density, layering sequence, and airflow resistivity with the normal‐incidence sound absorption coefficient of nonwoven composites consisting of three layers have been studied. The monofiber or multifiber needle‐punched nonwovens included poly(lactic acid) (PLA), polypropylene (PP), glass fiber, and hemp fibers. Air flow resistivity was statistically modeled and was found to increase with decreasing fiber size and nonwoven porosity. The former models developed for glass fiber mats in the literature were found to be inconsistent with the air flow resistance of the nonwovens reported below. The effects of the layering sequence on air flow resistivity and sound absorption were obtained. It was found that when the layer including reinforcement fibers, i.e., hemp or glass fiber, faced the air flow/sound source, the air flow resistance and the absorption coefficient were higher than the case when the layer including reinforcement fibers was farthest from the air flow/sound source. The difference was more pronounced if there was a greater difference between the resistivity values of the constituent layers of the nonwoven composite. Sound absorption coefficient was statistically modeled in terms of air flow resistivity and frequency. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Preparation and oil–water separation evaluations of polypropylene/low‐melt‐point polyester composites reinforced by thermal bonding and one‐step solution immersion

Nonwoven fabrics have been fabricated for oil–water separation, but simplifying the manufacturing processes is still a challenge. In this work, a facile and easily scaled up approach based on thermal bonding and one‐step solution immersion has been successfully developed to prepare nonwoven fabrics with high separation efficiency and flux of oil. Here, polypropylene (PP) and low‐melt‐point polyester (LPET) fibers with a unique sheath–core structure are employed to form PP/LPET nonwoven fabrics. Thermal bonding by hot press and hydrophobic treatment with 1H,1H,2H,2H‐perfluorodecyl‐1‐thiol (PFDT) are used to manufacture oil–water separation nonwoven fabrics. Effects of the ratio of LPET fibers and the concentration of PFDT are discussed in terms of mechanical properties, morphology, surface chemical composition, water contact angle and performance of oil–water separation and flux of the nonwoven fabrics. The results show that the strength of the nonwoven fabrics gradually increases with increasing ratio of LPET fibers. After immersion in PFDT, the nonwoven fabrics show high hydrophobicity with a water contact angle of 143°. They can be used to separate oil–water mixtures. The separation efficiency is 97–99% and the oil flux is 62 364.92 L m^?2 h^?1. This study provides a new prospect for simple introduction of a hydrophobic agent on a nonwoven fabric to achieve various functional oil–water separation materials. © 2020 Society of Chemical Industry     

Review of thermally point‐bonded nonwovens: Materials,processes, and properties

Recent research on all aspects of thermally point‐bonded nonwovens has led to considerable improvements in the understanding of material requirements for these nonwovens, the changes that occur during bonding, and the mechanical properties of the resultant nonwoven materials. This article will review (1) how the thermal bonding process transforms the material properties of feed fibers, (2) the implications for material selection, and (3) the resultant failure properties of the bonded nonwoven. The formation of a bond during thermal bonding follows in sequence through three critical steps: (1) heating the web to partially melt the crystalline region, (2) reptation of the newly released chain segments across the fiber–fiber interface, and (3) subsequent cooling of the web to re‐solidify it and to trap the chain segments that diffused across the fiber–fiber interface. The time scales for these processes closely match commercial practice. In addition, adequate pressure is required to compress the fibers that form the bond spots and enhance heat transfer to these fibers. However, pressures typically used in commercial practice are insufficient to increase the melting temperature significantly or to produce significant heating due to compression of the fibers. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci, 2006     

Frictional properties of thermally bonded 3D nonwoven fabrics prepared from polypropylene/polyester bi‐component staple fiber

The frictional properties of the three‐dimensional nonwoven samples produced using the recently developed air laying and through‐air thermal bonding system are evaluated. The samples were made from commercially available polypropylene (PP)/polyester (PET) (sheath/core) bi‐component staple fiber. In particular, the effects of the process parameters on the frictional properties were investigated by employing a statistical approach involving the uniform design of experiments and regression analysis. Stick‐slip frictional traces were obtained as a result of the presence of fiber loops, overlapping of fibers at bonding points, and deformation of fibers due to melting. The effect of normal load on both the static and dynamic friction forces can be described using the power‐law relationship. Both the static and dynamic friction factors increase with increase of the thermal bonding temperature and the dwell time. POLYM. ENG. SCI., 46:853–863, 2006. © 2006 Society of Plastics Engineers     

Relationships Between Birefringence of Constituent Fibers and Properties of Thermally Bonded Nonwovens

Summary: Three‐dimensional nonwoven fabrics have been produced using a newly developed air‐laid web forming and through‐air thermal‐bonding process directly from commercial PP/polyester (sheath/core) bi‐component staple fibers. Following the previous study on the morphology and structure of constituent fibers, this paper reports the breaking force and abrasion resistance of the fabrics. Results indicate that the relationships between both the breaking strength and abrasion resistance of the samples, and the thermal‐bonding process conditions are similar to each other. The appropriate thermal‐bonding temperature and dwell time are critical for achieving fabrics with high breaking strength and abrasion resistance. Such relationships are inconsistent with those between the tensile strength of the constituent fiber reflected by the birefringence and the thermal‐bonding process conditions. The birefringence of the constituent fiber appears to decrease with increasing thermal‐bonding temperature and dwell time. These results provide evidence that both the breaking force and abrasion resistance for the thermally bonded nonwoven fabrics are governed not only by the mechanical properties of constituent fibers, but also by the bonding properties between the fibers.

Abrasion mass loss and breaking force of fabric and birefringence of constituent fiber for the thermally bonded nonwoven samples as functions of the dwell time.     

Wetting behavior of thermally bonded polyester nonwoven fabrics: The importance of porosity

The wetting properties of thermally bonded polyester nonwoven fabrics with different basis weights were studied. These nonwovens had the same composition: 85% poly(ethylene terephthalate) and 15% poly(butylene terephthalate) fibers. Two techniques, the 3S wicking test and sessile drop method, yielded similar water contact angles for all the nonwovens, but these results differed from the values obtained with the single fibers. In the nonwoven fabrics, the pore structure played a dominant role in the wetting properties: the existence of large pores in the thinner nonwovens reduced the dimensions of the liquid–solid interfacial perimeter. Compared with the water contact angle of the constituent single fibers, the contact angle of the fabrics was increased. A crenellated surface model was created to quantify the influence of pores on the wettability of nonwovens. It was possible to deduce the surface porosity of the fabric with this model, but only in the case of contact with nonwetting liquids such as water: this surface porosity corresponded only to the outermost layers of the fabric structure. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 387–394, 2006     

Structure–property relationships of thermally bonded polypropylene nonwovens

The effect of fiber structure and morphology on the resultant mechanical and low load deformation properties of thermally bonded nonwoven polypropylene fabrics has been studied. Commercially available staple polypropylene fibers varying in linear density and draw ratio (Herculon and Marvess staple fibers) were used in this study. The orientation of these fibers was characterized by birefrigence measurements. Differential scanning calorimetry measurements were made to determine the heat of fusion and melting point of fibers. Experiments confirm that tensile strength and stiffness of the fabrics correlate with this fiber structure. Under the same bonding conditions fabrics made from fibers with low draw ratios show higher tensile strength and stiffness than do fibers with high draw ratios. The mechanical properties of fabrics were found to be greatly affected by the thermal bonding temperature. The tenacity and flexural rigidity of fabrics made from poorly oriented fibers show higher values than those made from highly oriented fibers. The shrinkage of the fabrics was observed to increase with increasing bonding temperature in both machine and cross machine directions. The changes in fabric thickness due to the thermal bonding are considerably lower for poorly oriented fibers.     

Deep‐black‐coloring effect of fabrics made of noncircular cross‐section polyester filaments

The effects of noncircular cross‐section (NCCS) poly ethylene terephthalate (PET) filaments and its shape factor on deep‐black‐coloring of dyed fabrics were investigated by comparing to that of the circular cross‐section PET ones. Indexes such as K/S, L* and Integ values were used for characterizing the deep‐black‐coloring effect on fabrics. The results indicated that fabrics made with NCCS PET filaments exhibited good deep‐black‐coloring effects. The calculated shape factor of the NCCS PET fiber had a significant correlation with the degree of deep‐black‐coloring exhibited by the fabric made from the fibers. A qualitative optical analysis of the NCCS PET fibers was carried out to explain the causes of the deep‐coloring of the NCCS fibers. This analysis implies that the contours of the NCCS fiber composed of surfaces with varied curvature increase the scattering of light by lowering specular reflection and increasing interior reflected and refracted light. This, in turn, strengthens the deep‐coloring effect. © 2013 Wiley Periodicals, Inc. Col Res Appl, 39, 511–518, 2014     

Generation of polymer ultrafine fibers through solution (air‐) blowing

Solution (air‐) blowing, an innovative technique for generation of ultrafine polymer fibers from solutions, was developed by feeding polymer solutions (instead of melts) to a die assembly similar to that used in the conventional melt (air‐) blowing process. Micro‐ to nano‐scaled polyvinylpyrrolidone (PVP) fibers were produced using PVP solutions with water, ethanol, and/or their mixtures as the solvents; and the morphologies of the fibers were examined by scanning electron microscopy. The processing variables, including PVP concentration, air‐blowing pressure, solution‐feeding pressure, and the volatility of the solvent system (the ratio of ethanol to water), were systematically investigated. The results indicated that solution (air‐) blowing was a viable technique to produce nonwoven fabrics consisting of ultrafine polymer fibers with diameters ranging from micrometers to nanometers. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Mechanical properties of surface modified jute fiber/polypropylene nonwoven composites

In this study, the jute/polypropylene nonwoven reinforced composites were prepared using film stacking method. The surface of jute fibers was modified using alkali treatment. These alkali treated jute fiber nonwoven composites were analyzed for their tensile and flexural properties. Increasing the amount of jute fibers in the nonwovens has improved the mechanical properties of their composites. The effect of stacking sequence of preferentially and nonpreferentially aligned nonwovens within the composites was also investigated. The flexural and tensile moduli of composites were found to be significantly enhanced when nonwovens consisting of preferentially and nonpreferentially aligned jute fibers were stacked in an alternate manner. The existing theoretical models of tensile modulus of fiber reinforced composites have been analyzed for predicting the tensile modulus of nonwoven composites. In general, a good agreement was obtained between the experimental and theoretical results of tensile modulus of nonwoven composites. POLYM. COMPOS., 35:1044–1050, 2014. © 2013 Society of Plastics Engineers     

Synthesis and characterization of polymer‐filled nonwoven membranes

Polymer‐filled nonwoven membranes were prepared by filling the open pores of nylon nonwovens with poly(2‐acrylamido‐2‐methyl‐1‐propanesulfonic acid) (PAMPS). PAMPS was synthesized via radical polymerization and crosslinked to prevent its dissolution in water. PAMPS‐filled nylon nonwoven membranes showed enhanced dimensional stability and mechanical properties when compared with PAMPS membranes without nonwovens. The conductivities of PAMPS‐filled nylon nonwovens were slightly lower than those of PAMPS membranes. Compared with PAMPS membranes without nonwoven hosts, both linear and crosslinked PAMPS‐filled nylon nonwoven membranes exhibited lower vapor permeabilities for water, methanol, acetone, and dimethyl methylphophonate (DMMP). In addition, crosslinked PAMPS‐filled nonwoven membranes presented high permselectivity on DMMP over water, which is critical for chemical protection application. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Effect of cellulase pretreatment of raw and bleached cotton fibers on properties of hydroentangled nonwoven fabrics

This study was undertaken to investigate the effect of enzymatic pretreatment of cotton (polysaccharides) fibers on the properties of resulting nonwoven fabric. Enzymatic treatment is known to improve the esthetical properties of fabrics but will likely lead to a reduction in strength. In the case of nonwovens the strength loss can be even more drastic as cellulase may attack bonded areas of the fabric. In this work, raw and bleached cotton fibers were treated with enzyme solutions prior to fabric formation to avoid possible damage to the bonded areas and improve strength retention. These fibers were first modified with commercially available whole cellulases and monocomponent endoglucanase enzyme solutions. Then they were formed into a fabric and bonded via hydroentangling. Parameters such as bending modulus, fabric tenacity, fiber strength, length and reducing power were measured for each sample. The pretreatment of cotton fibers prior to fabric formation showed that the resulting nonwovens could be stronger and more drapeable than the same fabric composed of untreated fibers. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Fabrication of Multifunctional Filters via Online Incorporating Nano‐TiO2 into Spun‐Bonded/Melt‐Blown Nonwovens for Air Filtration and Toluene Degradation

Multifunctional air filters with high filtration efficiency for aerosol and good degradation for toluene and bacteria are fabricated via online incorporation of TiO₂/Ag nanoparticles into the composite nonwovens with spun‐bonded/melt‐blown (SM) hierarchical structure. Today, severe environmental pollution attributed to atmospheric pollutants, mainly including particulate materials, and gaseous volatile organic compounds, as well as bacterial and viral contaminants, has drawn worldwide attention. In this work, a novel online incorporation technique to fabricate a multifunctional air filter with hierarchical structure of SM nonwovens and TiO₂ based nanoparticles is proposed. The in situ incorporation technique not only enables the SM nonwovens filters with four orders increment on toluene degradation rate, but also increases filtration quality factor Q_f of the SM filters to 0.2251 Pa^?1. This research shows promising applications of the multifunctional TiO₂/SM nonwoven filters for indoor air remediation. In addition, this scale‐up fabrication method of fiber‐based filters will potentially promote engineering of macromolecular fiber materials.     

亚麻纤维增强热固性树脂复合材料板材的研究

本文以亚麻纤维作为原料,经过针刺工艺制得亚麻纤维针刺毡,作为复合材料的增强体.通过改变纤维、热固性树脂种类,利用真空辅助RTM方法及模压法制备复合材料板材.对板材进行了拉伸及弯曲性能测试,比较了不同纤维和树脂的结合情况,进一步阐述了板材破坏机理.     

Softness evaluation of keratin fibers based on single‐fiber bending test

The evaluation of single‐fiber softness by bending is an ingenious and vital approach for the basic investigation of both the fiber bending properties and the textile softness. The bending behavior and bending modulus of wool, alpaca and silk fibers have been measured by an axial‐buckling method developed by the authors, which uses the fiber compression bending analyzer (FICBA). The bending properties of single fibers were quantified by calculating the equivalent bending modulus and the flexural rigidity by measuring the protruding length and diameter of fiber needles and the critical force, P_cr, obtained from the peak point of the force‐displacement curve. The measured data showed that the equivalent bending modulus of the alpaca fiber is higher than that of wool fiber, and even the rigidity is 10 times as high as wool, but its friction coefficient is lower than that of wool, which means that the soft handle of alpaca fabrics is mainly due to the smooth surface and low friction coefficient of alpaca fibers in contrast to that of wool fiber. For the silk fiber, despite high equivalent bending modulus, the smoother handle of silk should be mainly due to the thin fiber diameter in contrast to that of keratin fibers. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 701–707, 2006     

Fiber diameter of polybutylene terephthalate melt‐blown nonwovens

A polymer air‐drawing model of Polybutylene Terephthalate (PBT) melt‐blown nonwovens has been established. The predicted fiber diameter coincides with the experimental data. The effects of the processing parameters on the fiber diameter have been investigated. A lower polymer flow rate, a higher initial air velocity, and a larger die‐to‐collector distance can all produce finer fibers, whereas too high an initial air velocity and too large a die‐to‐collector distance contribute little to the polymer drawing of PBT melt‐blown nonwovens. The results show the great potential of this research for the computer‐assisted design of melt‐blowing technology. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 1750–1752, 2005