Liangfeng Sun

Reducing Automotive Interior Noise with Natural Fiber Nonwoven Floor Covering Systems

Eliminating unwanted noise in passenger compartments of vehicles is important to automobile manufacturers. The ability to reduce noise inside the vehicle enhances the perceived value of the vehicle to the consumer, and offers a competitive advantage to the manufacturer. Several methods are presently employed to reduce noise and its sources, one of which uses sound-absorbing materials attached to various components such as floor-coverings, package trays, door panels, headliners and trunk liners. Natural fibers are noise-absorbing materials that are renewable and biodegradable, making them an effective choice for the automobile industry. Floor coverings using natural fibers (kenaf, jute, waste cotton, and flax) in blends with polypropylene (PP) and polyester (PET) were developed as carded needle-punched nonwovens. The acoustical absorption coefficients of these floor coverings, and of floor coverings in combination with an underpad (either a rebonded polyurethane foam, or a soft cotton nonwoven) were evaluated by ASTM E— 1050 in the frequency range of 100 to 3200 Hz. By stacking an underpad and a floor covering together, a floor covering system was created. The measurements demonstrated that each of the natural fiber-based nonwoven floor coverings contributed to noise reduction, e.g., coefficients = 0.54—0.81 at 3.2 kHz. Noise was significantly reduced with a floor covering system using either of the underpads. The most reduction occurred with a polyurethane pad; for example, for kenaf floor covering C20-1 the coefficients at 3.2 kHz were: 1.0 with polyurethane versus 0.81 with cotton pad.

Natural fibers for automotive nonwoven composites

Two types of nonwoven composites, uniform and sandwich structures, are produced using bagasse, kenaf, ramie, and polypropylene (PP) fibers. The experimental uniform composites include kenaf/PP (70/30), bagasse/PP (50/50), and ramie/PP (70/30). The experimental sandwich composites include kenaf/bagasse/kenaf and ramie/kenaf/ramie. A comparative study of these experimental composites is conducted in terms of mechanical properties, thermal properties, and wet properties. Composite tensile and flexural properties are measured using a desktop tensile tester. Composite thermal properties are characterized using dynamic mechanical analysis (DMA). Water absorption and thickness swelling of the composites are evaluated in accordance with an ASTM method. Scanning electron microscopy is used to examine the composite bonding structures. Statistical method of ANOVA is used for the comparative analysis. The study finds that the uniform structures have higher tensile strength and modulus, as well as higher flexural yielding stress and modulus than the sandwich structures. In terms of the wet properties, the uniform composites have less water absorption but higher swelling rate than the sandwich composites. The DMA results show that the uniform composites feature a higher softening temperature (140 C) and melting temperature (160 C), in contrast to the sandwich composites with the softening point 120 C and melting point 140 C. Within the uniform structure group or sandwich structure group, the composite thermal mechanical properties did not differentiate very much among the different natural fibers, indicating that the composite thermal mechanical strength was largely dependent upon the thermal property of the polypropylene bonding fiber.

Regenerated cellulose fibers from waste bagasse using ionic liquid

Regenerated cellulose fibers from bagasse and wood were produced under various processing conditions using the ionic liquid 1-butyl-3-methylimidazolium chloride (BMIMCl) as a solvent. Two different ionic liquid solutions were prepared with 6 wt% of bagasse cellulose and 6 wt% of wood cellulose. The solutions were extruded with a dry-jet and wet-spinning method using water as a coagulation bath. A thermogravimetric analyzer (TGA) was used to measure the thermal properties of these regenerated fibers. Dynamic mechanical analysis (DMA) was used to determine the thermal mechanical property of the regenerated cellulose fibers and wide-angle X-ray diffraction (WAXD) was used to measure the degree of crystallinity, as well as the degree of crystal orientation for those experimental fibers. To evaluate the quantity of ionic liquid residue in the regenerated fibers, the instrumental methods of FT-IR and mass spectrometry were applied to test the residues of BMIMCl in the regenerated fibers. Research results indicated increases in the degree of crystallinity and storage modulus under a higher fiber drawing speed. Both regenerated bagasse film and regenerated wood film had similar thermal properties. However, the regenerated bagasse fibers showed a higher degree of crystallinity, and higher tenacity than the regenerated wood fibers obtained under the same condition. The study also revealed that water treatment would be helpful for eliminating the ionic liquid residue in the regenerated fibers.

Crystalline characteristics of cellulose fiber and film regenerated from ionic liquid solution.

Regenerated cellulose fiber, fiber extrudate, and film were produced from cellulose solution prepared with raw pulp and ionic liquid solvent 1-butyl-3-methylimidazolium chloride ([BMIM]Cl). Spinning setting was based on a dry-jet and wet-spun approach including extrusion, coagulation, drawing, drying, and winding. Crystallization of the experimental fiber, fiber extrudate, and film was evaluated using a technique of wide angle X-ray diffraction (WAXD). Crystallinity index, crystallite size, and crystal orientation factor were calculated and compared among these samples. Influence of die shape, die dimension, and drawing speed on the regenerated cellulose crystallinity was discussed. The study indicated that the pulp cellulose was a Cellulose I type structure. The cellulose regeneration from the [BMIM]Cl solution completed a transformation from this intermediate phase to a final Cellulose II phase. The die shape and dimension and drawing speed were all important factors affecting the crystallinity of regenerated cellulose fiber and film.

Kinetics modeling of dynamic pyrolysis of bagasse fibers.

The thermal decomposition mechanism of raw and treated bagasse fibers was modeled with three parallel independent first-order reactions. The kinetic parameters and pseudo components which best fit the experimental dynamic pyrolysis rate of bagasse was determined by means of the Matlab program using the least-square method. The calculated rate of thermal decomposition for each bagasse sample was consistent with experimental pyrolysis rate very well. A method was adopted to calculate the contents of cellulose, hemicelluloses, and lignin for bagasse fiber based on the dynamic pyrolysis model. The calculated contents of the untreated bagasse fiber agreed very well with some reported values from the literature. The effect of treatment conditions on the bagasse fiber compositions was also studied. From the three-dimensional plot for each of the three components, it could be observed that bagasse fibers treated under the intermediate alkaline condition could achieve the higher content of cellulose.

Antimicrobial regenerated cellulose/nano-silver fiber without leaching

The formation of antimicrobial regenerated cellulose fibers using an ionic liquid solvent, 1-butyl-3-methylimidazolium chloride, and silver nanoparticles was studied. The cellulose preparation and dispersion efficiency of the silver nanoparticles in the solvent were evaluated via scanning electron microscope and transmission electron microscopy in terms of different processing conditions. The influence of silver nanoparticles on regenerated cellulose fiber crystallization and strength was examined using a wide angle X-ray diffractometry and tensiometry, respectively. The bioactive efficacy of the cellulose/nano-silver fiber was tested in accordance with the standard method of ASTM E 2149-10. The cellulose/nano-silver fibers were bioactive and killed Escherichia coli almost completely without any leaching problems. The addition of nano-silver significantly increased the cellulose fiber tensile strength and modulus with an insignificant reduction in fiber elongation, and a slower thermal decomposition rate, evidenced by increased fiber crystallinity. Higher processing temperatures improved the nano-silver dispersion efficiency. The final nano-silver suspension in the regenerated cellulose matrix was composed of scattered clusters with an average size of 700 nm and a distribution density of 14,098 mm−2.

Evaluating Efficiency of Alkaline Treatment for Waste Bagasse

Cellulose, lignin, raw bagasse fiber, and extracted bagasse fibers chemically processed with different concentrations of sodium hydroxide solution and treatment time were measured by thermogravimetry analysis (TGA). The thermal characteristics of these fibers were determined by thermogravimetry (TG) and derivative thermogravimetry (DTG) profiles and analyzed based on the onset degradation temperature, peak rate of thermal decomposition, and residual weight. According to the observations from the experimental data from TGA and DTG profiles and literature reports, it was found that higher content of cellulose and lower content of lignin would result in higher onset degradation temperature, higher peak rate of decomposition, and lower residual weight. Statistical analysis of the onset decomposition temperatures, peak rate of weight loss, and residual weights of different extracted bagasse fibers showed that most of their values were significantly different. The three‐dimensional surface plots of onset decomposition temperature and peak rate of weight loss indicated that higher content of cellulose occurred in the bagasse fiber treated under the condition close to the region around 2 N NaOH for 2 hours or 1.5 N NaOH for 1.5 hours.

Comparative Study of Hemp Fiber for Nonwoven Composites

Abstract Hemp fiber is a strong natural fiber similar to flax, kenaf, and ramie, possessing very good fiber quality and physical properties of strength, durability, and absorbency. Hemp fiber has been increasingly used for making nonwoven composites that are ideal for the production of biobased auto interior parts. This paper studies the physical properties of a hemp/polypropylene composite and compares these properties with those of a kenaf/polypropylene composite, a ramie/polypropylene composite, and a bagasse/polypropylene composite. The hemp/polypropylene nonwoven was produced by carding and needle-punching techniques and was thermo-bonded to form a hemp composite. Tensile and bending properties were measured using an Instron tensile tester. Dynamic mechanical properties were tested using a DMS instrument. The thermal property was analyzed using a TG instrument. A preliminary study on the ability of the hemp fiber composite to resist termite attack was also conducted. In comparison, the hemp composite featured a better thermal property; the kenaf composite had better mechanical properties; the ramie composite indicated a better acoustical property; and the bagasse composite exhibited better wet properties. Neither hemp nor bagasse fiber composite was capable of resisting termite attack.

Characterization of epoxy prepreg curing process

ABSTRACT The isothermal and dynamic curing process of epoxy composite was studied using differential scanning calorimetry (DSC), thermal gravimetric analysis (TGA), and other techniques. The variation of degree of curing with time and temperature was analyzed. The degree of curing was limited at any particular temperature because of the diffusion control in isothermal curing process. Half-life and maximum cure time were discussed in the analysis of the isothermal curing process. The modeling result from isothermal curing process indicated that degree of curing calculated with diffusion control agreed well with experimental data. The degree of curing calculated by two methods for dynamic curing process had a deviation with experimental data in either earlier or later cure stages. The relationship between T g and the degree of curing was described by two models. Both models agreed well with the experimental T g . The isothermal curing diagrams of time–temperature–transformation (TTT) and conversion–temperature–transformation (CTT) were constructed. Each region in TTT and CTT diagrams corresponded to the phase state of the curing process, so that the curing mechanism was clearly reflected in diagrams. The thermal stability analysis indicated the epoxy resin system was very thermally stable under temperature of 300°C.

Regenerated Cellulose Fiber and Film Immobilized with Lysozyme

The present work reports an initial engineering approach for fabricating lysozyme-bound regenerated cellulose fiber and film. Glycine-esterified cotton was dissolved in an ionic liquid solvent 1–Butyl–3–methylimidazolium Chloride (BMIMCl) in which lysozyme was activated and covalently attached to cotton cellulose through an enzymatic conjugation between its carboxyl groups and glycine cellulose’s amino groups. The resulting solution was extruded for fiber/film formation in a water bath. After performing a bicinchoninic acid (BCA) protein assay, quantity of attached lysozyme to cellulose fiber/film was evaluated. The study exhibited that a synthesis of lysozyme conjugation on cellulose in BMIMCl could be completed in a control manor, resulting in a cellulose solution suitable for fiber/film production. It was also found that lysozyme could be successfully immobilized onto the cellulose fiber and film regenerated from solution spinning with a reasonable amount ranging from 197.6 to 343.7 μg/mL.mg.