Weight Loss Of Fibers Research Articles

Modification of Polylactic Acid Fiber with Enzymatic Treatment

Enzymatic modification of polylactic acid fibers is investigated using various kinds of protease and lipase. The effects of enzymes on the hydrolysis of polylactic acid fibers is evaluated by means of fiber weight loss, fiber strength and fiber surface observation. It is found that proteases derived from Bacillus subtilis and Bacillus licheniformis had remarkable activities on polylactic acid fibers. It is also observed that the hydrolysis of polylactic acid fibers with these enzymes causes a serious drop in fiber strength, although fiber weight loss is lower.

Sorption Properties of Flax Fibers Depending on Pretreatment Processes and their Environmental Impact

The purpose of this research was to investigate the influence of different pre-treatment processes, on the sorption properties of flax fibers and the impact of residual treatment baths on environmental pollution. Flax fibers were subjected to different scouring processes (alkaline, acidic and enzymatic scouring) and, subsequently, oxidative bleaching, with and without application of ultrasound energy. The sorption properties of differently pre-treated flax fibers were defined by iodine sorption value, moisture sorption, and water retention power. The residual pre-treatment baths were ecologically analyzed using total organic carbon, chemical oxygen demand, biochemical oxygen demand and biological degradability. The obtained results indicated that the alkaline, acidic and enzymatic scourings of flax fibers have a significant effect on their sorption properties and, consequently, on the bleaching process. The application of ultrasound in the scouring and bleaching bath increased the fiber weight loss and water retention power of the flax fibers, as well as improving the ecological parameters. The optimal pre-treatment process was enzymatic bioscouring because it provided a lower weight loss, a better absorptivity of the flax fibers, and is less environmentally harmful.

Effects ofIn Vitro degradation on the weight loss and tensile properties of PLA/LPCL/HPCL blend fibers

PLA/LPCL/HPCL blend fibers composed of poly (lactic acid) (PLA), low molecular weight poly (ɛ-caprolactone) (LPCL), and high molecular weight poly (ɛ-caprolactone) (HPCL) were prepared by melt blending and spinning for bioabsorbable filament sutures. The effects of blending time and blend composition on the X-ray diffraction patterns and tensile properties of PLA/LPCL/HPCL blend fibers were characterized by WAXD and UTM. In addition, the effect ofin vitro degradation on the weight loss and tensile properties of the blend fibers hydrolyzed during immersion in a phosphate buffer solution at pH 7.4 and 37°C for 1–8 weeks was investigated. The peak intensities of PLA/LPCL/HPCL blend fibers in X-ray diffraction patterns decreased with an increase of blending time and LPCL contents in the blend fibers. The weight loss of PLA/LPCL/HPCL blend fibers increased with an increase of blending time, LPCL contents, and hydrolysis time while the tensile strength and modulus of the blend fibers decreased. The tensile strength and modulus of the blend fibers were also found to be increased with an increase of HPCL contents in the blend fibers. The optimum conditions to prepare PLA/LPCL/HPCL blend fibers for bioabsorbable sutures are LPCL contents of 5 wt%, HPCL contents of 35 wt%, and blending time of 30 min. The strength retention of the PLA/LPCL/HPCL blend fiber prepared under optimum conditions was about 93.5% even at hydrolysis time of 2 weeks.

Surface hydrolysis of filaments based on poly(trimethylene terephthalate) spun at high spinning speeds

AbstractThe surface alkaline hydrolysis of fibers made from poly(trimethylene terephthalate) (PTT) was studied after extruding the polymer at high spinning speeds from 2000 to 6000 m/min and heat setting in the range of temperatures from 100 to 180°C. Fiber weight loss increased with an increasing heat‐setting temperature but it was also dependent on the spinning speed. Some of the partially hydrolyzed fibers had a well‐developed, hydrophilic surface, and pore size in the range of 0.69 to 1.20 μm. The optimum reaction and morphological conditions for increasing porosity in PTT fibers depends on spinning speed and heat‐setting temperature. A temperature of 180°C is the upper limit for heat‐setting PTT filaments but seems to be the most effective for making porous fibers. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 1724–1730, 2004

Studies on biodegradable poly(hexano-6-lactone) fibers. Part 3. Enzymatic degradation in vitro (IUPAC Technical Report)

Abstract Poly(hexano-6-lactone) (PCL*) fibers were enzymatically degraded by a hydrolase in vitro. The extent of degradation of PCL fibers was examined by weight loss, mechanical properties loss such as tensile strength and ultimate elongation decreases, and visual observations by scanning electron microscopy. The in vitro degradation of PCL fibers was carried out using a lipoprotein lipase (Lipase-PS) as a hydrolase. The kinetic study on the weight loss of PCL fiber accompanying the enzymatic degradation suggested that the degradation of PCL fibers gradually takes place from the surface, not bulk degradation. The rate of degradation was found to depend on draw ratio and crystallinity of the PCL fibers. The strength loss of PCL fibers in the course of degradation took place faster than the weight loss of PCL fibers. Sonic velocity measurements as well as dynamic mechanical properties of PCL fibers were also examined as a function of weight loss of sample fibers with Lipase-PS treatments. It was shown that sonic velocity and value of loss tangent d changed steeply for undrawn PCL fiber in the first step with enzymatic digestion.

Pore development in alumino-silicate fiber treated in hydrofluoric acid solutions

Melt-blown alumino-silicate ceramic fibers were treated in hydrofluoric acid solutions at room temperature to produce microporous refractory fibers. The pore development of the fibers was studied as a function of HF concentration and treatment time. Surface area and weight loss of fibers was measured simultaneously after exposure to the HF solutions. Changing the HF concentration of the solution from 0.25 to 1.5 mol dm −3 linearly increased the weight loss from 8 to 46%. At HF concentration ranged from 0.5 to 1.5 mol dm −3, BET area also linearly increased from 8 to 40 m 2 g −1 with increasing treatment time from 6 to 48 h. The dominant pore size of the HF treated fibers had a radius range of 1.7–1.9 nm. Fourier Transform infrared (FTIR) spectra of the obtained microporous fibers showed that absorption bands in the range of 2700–3100 cm −1 and 3200–3700 cm −1 increased with increasing BET area of fiber.

Enzymatic Degradation of Poly(ε-caprolactone) Fibers in vitro

Poly(e-caprolactone) (PCL) fibers were enzymatic degraded by a hydrolase in vitro. The extent of degradation of PCL fibers was examined by weight loss, mechanical properties loss such as tensile strength and ultimate elongation decrease, and visual observation by scanning electron microscopy. The in vitro degradation of PCL fibers was carried out using Lipase F-AP as a hydrolase. A kinetic study on the weight loss of PCL fiber accompanying the enzymatic degradation suggested degradation of PCL fibers gradually from the surface of the fibers into their core. Scanning electron microscopy supported surface, not bulk degradation. The rate of degradation was found to depend on draw ratio and crystallinity of the PCL fibers. Strength loss of PCL fibers in the course of degradation took place faster than weight loss of PCL fibers.

Stoichiometric Analysis of the Weight-Decrease in the Enzymatic Treatment of Cotton Fiber: A Guide to Real-Time Monitoring System for the Treatment.

Enzymatic hydrolysis of cotton fiber was studied in detail to find out a good way to monitor the weight loss of fiber precisely. In this enzymatic treatment the linear relationship between the weight loss and the glucose formation was confirmed. Stoichiometric analysis of the hydrolysis products revealed that both glucose and oligosaccharides are formed from cellobiose in a constant ratio to give the linearity. This may be attributed to the cellobiose hydrase and polymerase activities involved in the cellulase used (originated from Filamentous fungi). Based on this finding, a new monitoring system using the chemi-luminescence of luminol was examined for assessing the glucose formation, which was related with the total weight loss of cotton fiber. This method is superior to other methods in terms of shortness of measuring time and applicable for monitoring the weight loss of dyed fabrics.

Surface characterization of electrochemically oxidized carbon fibers

High strength PAN-based carbon fibers were continuously electrochemically oxidized by applying current to the fibers serving as an anode in 1% wt aqueous KNO3. Progressive fiber weight loss occurred with increasing extents of electrochemical oxidation. XPS studies (C 1s and O 1s) indicated that the oxygen/carbon atomic ratio rose rapidly to 0.24 as the extent of electrochemical oxidation was increased from 0 to 133 C/g and then remained almost constant as the extent of electrochemical oxidation rose to 10 600 C/g. Fitting the C 1s spectra demonstrated that the rise in surface oxygenated functional groups was mainly due to an increase in carboxyl (COOH) or ester (COOR) groups. An increase in the intensity of the O 1s peak (534.6–535.4 eV) after electrochemical oxidation corresponded to chemisorbed oxygen and/or adsorbed water. Electrochemical oxidation increased surface activity by generating more surface area via the formation of ultramicropores, and by introducing polar oxygen-containing groups over this extended porous surface. FT-IR spectra showed a broad peak at about 1727 cm−1 from C=O stretching vibrations of carboxyl and/or ketone groups, the relative intensity of which increased significantly with the extent of electrochemical oxidation. Post-oxidation heat-treatments in flowing nitrogen at 550°C for 30 min. caused further weight losses due to decarboxylation of carboxyl groups and other reactions in which oxygenated functions decomposed. These weight losses increased with the extent of electrochemical oxidation. This demonstrated that more oxygenated groups formed on the internal pore surfaces as pores increasingly penetrated deeper into the fibers with increased electrochemical treatment. Weight loss depended on the heat treatment temperature since different types of carbon–oxygen surface groups were formed during the electrochemical oxidations. Different functions have different abilities to decarboxylate or decarbonylate. The amount of Ag+ and NaOH uptake by electrochemically oxidized fibers rapidly decreased as the temperature of the post heat treatment increased to 550°C. Beyond 550°C the progressive decrease in Ag+ adsorption and NaOH uptake continued at a slower rate and approached 0 μmol/g after heating to 850°C. Conversely, after heat treatment I2 adsorption showed a marked increase as the treatment temperature was raised. Thermal decomposition of carbon–oxygen complexes within the pore structure leads to a lower hydrophilicity of the pore surface. The extensive micropore surface area generated by electrochemical oxidation becomes more accessible to I2 as CO2 and CO evolve. Very narrow pores (<10 Å diameter) blocked by hydrogen bonding and oxygenated functions become more open. XPS analyses illustrated that the surface oxygen content decreased significantly after heat-treating to 550 or 850°C and was lowest after the 850°C treatment.

Treating Cotton with Cellulases and Pectinases: Effects on Cuticle and Fiber Properties

Cellulases and pectinases are used to treat raw cotton fibers and unscoured cotton fabrics. The structural changes in the surfaces of cotton caused by the enzymatic treat ments and resulting properties are the main focus of this study. Both staining tests and microscopy observations confirm that the cuticle is removed by the pectinases and cellulases. All evidence of fiber weight loss and fabric water absorbency shows that significant changes in cotton fiber and fabric properties occur with mild treatment conditions. Physical changes in the cotton surfaces are clearly revealed by scanning electron micrographs. All fiber weight loss values stemming from the enzymatic treat ments are smaller than or near the cotton cuticle weight. Sufficient water absorbency for textile processing is obtained with mild enzymatic treatments, corresponding to a small but statistically significant fiber weight loss.

Thermo-Oxidative Stability and Fiber Surface Modification Effects on the Inplane Shear Properties of Graphite/PMR-15 Composites

Experiments were conducted to study the effects of thermo-oxidative stability (weight loss) and fiber surface modification on the inplane shear properties of graphite/PMR-15 unidirectional composites. The isothermal aging was conducted at 316°C and up to 1000 hours of aging times. The role of fiber surface treatment on the composite degradation during the thermo-oxidative aging was investigated by using A-4 graphite fibers having three different surface modifications, namely untreated (AU-4), surface treated (AS-4), and surface treated and sized with epoxy-compatible sizing (AS-4G). Weight loss of matrix, fibers, and composites was determined during the aging. The effect of thermal aging was seen in all the fiber samples in terms of their weight loss and reduction in fiber diameter. Calculated values of weight loss fluxes for different surfaces of rectangular unidirectional composite plates showed that the largest weight loss occurs at those cut surfaces where fibers are perpendicular to the surface. Consequently, the largest amount of damage was also noted on these cut surfaces. Optical observation of neat matrix and composites plates subjected to the different aging times revealed that the degradation (such as matrix microcracking, void growth, etc.) occurred within a thin surface layer near specimen edges. The inplane shear modulus of the composites was unaffected by the fiber surface treatment and the thermal aging. The shear strength of the composites having the untreated fibers was the lowest and it decreased with aging. Fracture surface examination of the composites having untreated fibers suggests that the weak interface allows the oxidation reaction to proceed along the interface and thus expose the inner material to further oxidation. The results indicate that fiber-matrix interface affects the composite degradation process during its thermal aging and that the weak interface accelerates the composite degradation.

Modification of polyethylene terephthalate (Dacron) via denier reduction: effects on material tensile strength, weight, and protein binding capabilities.

Thrombosis remains a significant and potentially catastrophic complication of polyethylene terephthalate (Dacron) prosthetic vascular graft implantation. Numerous attempts have been made to create a novel surface that reduces the adverse effects of blood interaction with the material. The purpose of this study was to create reactive groups on Dacron without significantly altering the chemical and physical properties of the biomaterial. These groups would then serve as "anchor sites" for covalent attachment of the blood protein albumin to the surface, thus creating a more biocompatible surface. Denier reduction, an established textile chemistry procedure that creates carboxyl groups on the fiber surface via hydrolysis of the material, was performed at 100 degrees C using sodium hydroxide concentrations of 0.5, 1.0, 2.5, and 5.0% (treated materials referred to as 0.5% hydrolyzed etc.). Tensile strength determination of hydrolyzed materials revealed no statistically significant difference in material strength between control, 0.5, and 1.0% hydrolyzed materials; the 2.5 and 5.0% hydrolyzed materials had significant strength loss as compared to the controls. Significant fiber weight loss occurred in the 1.0, 2.5, and 5.0% hydrolyzed Dacron segments. The 0.5% hydrolyzed material did not have any significant weight loss. Covalent linkage of 125I-albumin to these modified materials using the crosslinker 1-ethyl-3-(3-dimethyl aminopropyl)-carbodiimide hydrochloride (EDC) resulted in the 0.5% hydrolyzed material having the greatest protein binding (330 ng/mg Dacron, 2,4-fold greater than control). Incubation of the 0.5% hydrolyzed material with EDC and various concentrations of 125I-albumin resulted in the 14.80 microM solution permitting the greatest binding per milligram Dacron (330 ng/mg Dacron). Scanning electron microscopy, performed blindly, revealed no change in the 0.5% hydrolyzed Dacron as compared to untreated Dacron. The 5.0% hydrolyzed Dacron, however, had noticeable structural damage on the outer periphery of the fiber surface. Observation of the untreated Dacron with nonspecifically bound albumin showed scattered areas of albumin adherent to the fiber surface whereas covalent linkage of albumin to the 0.5% hydrolyzed Dacron via EDC crosslinking showed numerous albumin moieties on each fiber. This study demonstrates that a clinically accepted biomaterial (Dacron) can be chemically modified, without significantly altering the physical and chemical characteristics of the biomaterial, in order to covalently bind albumin to the fiber surface. Thus, these results serve as foundation for creating potential novel biomaterials without significantly altering the properties of the original biomaterial.

Analysis of Swelling Behavior of Silk Fibers by Small-Angle X-Ray Scattering.

The small angle X-ray scattering of domestic and wild silk fibers were examined under air-dried, water-swollen, and sodium hydroxide aqueous solution-swollen conditions. The scattering intensity of those fibers were higher in water-swollen state than in dried state. It became much higher when a sodium hydroxide solution was used to swell the specimens, exhibiting a maximum or a shoulder in the scattering curve. This suggests the appearance of structures having a long period in the direction perpendicular to the fiber axis. The increase of scattering intensity was larger in domestic silk fiber than in wild silk fiber. The weight-loss of fibers due to the treatment with a sodium hydroxide solution was also larger in domestic silk fiber. The increase in scattering intensity of swollen domestic silk fiber became less marked when they had been subjected to the treatment with a metal-salt solution or the tannin fixing treatment in advance. These experimental evidences suggest that the molecular chains in amorphous region of the wild silk fibers seem to be rigidly linked by the coloring and the mineral matter.

Effect of Heat-Setting Temperature on the Hydrazine Treatment of Poly (ethylene Terephthalate) Partially Oriented Yarn

Poly (ethylene terephthalate) partially oriented yarn (PET POY) was heat set at 100 to 220°c in a fixed state and then treated with hydrazine. Although crystallinity of the heat-set PET POY increased with increased heat-setting temperature, weight loss from the hydrazine treatment initially decreased at a temperature up to 120°c and subsequently increased above 120°c. The hydrazinolyzed POY fiber is dyeable with acid dyes because of the hydrazide groups incorporated by hydrazinolysis. Nitrogen content and dye exhaustion with CI acid orange 7 showed trends similar to the weight loss of the hydrazinolyzed POY fibers. On the other hand, the dyeability of the hydrazinolyzed POY fibers with CI disperse violet 1 was lower than that of the untreated fibers. Many cracks appeared on the surface of the hydrazinolyzed fibers, and they were smallest on the fibers that were heat set at 120°c.

Biodegradation of microbial polyesters in the marine environment

The biodegradation of microbial copolyesters, poly(3-hydroxybutyrate-co-3-hydroxyvalerate)(P(3HB-co-3HV)) and poly(3-hydroxybutyrate-co-4-hydroxybutyrate) (P(3HB-co-4HB)), were studied under marine exposure conditions in sea water during the period from January to December. The processes of biodegradation were analyzed by monitoring the time-dependent changes in weight loss (erosion), molecular weight and mechanical strength of films, plates and fibers. All the samples exposed in sea water were degraded via surface dissolution. The rate of surface erosion was almost independent of the copolymer compositions of P(3HB-co-3HV) and P(3HB-co-4HB) samples, but markedly dependent upon the temperature of the sea water. Two strains of actinomycetes ( Streptomyces) capable of using P(3HB) as the sole carbon source have been isolated from sea sediment.

Pressure Effects on the Thermal Stability of Silicon Carbide Fibers

Commerically available polymer‐derived SiC fibers were treated at temperatures from 1000° to 2200°C under vacuum and at argon gas pressures of 0.1 and 138 MPa. Effects of increasing inert gas pressure on the thermal stability of the fibers were determined through studies of the fiber microstructure, weight loss, grain growth, and tensile strength. The 138‐MPa argon gas treatment was found to shift the onset of fiber weight loss from 1200° to above 1500°C. Grain growth and tensile strength degradation were correlated with weight loss and were thus also inhibited by high‐pressure treatments. Retreatment in 0.1 MPa of argon of the fibers initially treated in 138 MPa of argon caused further weight loss and tensile strength degradation, thus indicating that high‐pressure inert gas conditions were effective only in delaying fiber strength degradation and that no permanent microstructural changes were induced.

Resin/fiber thermo‐oxidative interactions in pmr polyimide/graphite composites

AbstractThe amounts of resin weight loss and fiber weight loss in four PMR polyimide/graphite fiber composites were calculated from the composite weight losses and the fiber/resin ratios of the composites after long term thermo‐oxidative aging in 600° F air. The accelerating effect of graphite fiber on resin weight loss, compared to neat resin weight loss, indicated the presence of a deleterious resin/fiber thermo‐oxidative interaction, presumably due to fiber impurities. Similarly, the declerating effect of the protective matrix resin on fiber weight loss, compared to bare fiber weight loss, was also demonstrated. The amount of hydrazine indigestible resin and the amount of loose surface graphite fiber that formed during 600° F exposure of the composites were quantitatively determined. The indigestible residual resin was also qualitatively studied by scanning electron microscopy.