Micromechanics of hemp strands in polypropylene composites

The present paper investigates micromechanics of hemp strands. The main objective of the present work has been the determination of the intrinsic strength of hemp strands. Hemp strands have been used as reinforcement of Polypropylene composites. Different percentages of hemp strands and coupling agents (MAPP) have been tested to obtain a map of the mechanical properties of that kind of composites and the effect of the components on the final properties. Mechanical properties of the different specimens have been tested using standard experimental methods and equipment. Micromechanics of the strands have been obtained using Hirsch model, Bowyer-Bader methodology and Kelly-Tyson model.Fil: Vallejos, María Evangelina. Universidad Nacional de Misiones; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Nordeste; ArgentinaFil: Espinach, F. X.. Universidad de Girona; EspañaFil: Julián, F.. Universidad de Girona; EspañaFil: Torres, L.. Universidad de Girona; EspañaFil: Vilaseca, F.. Universidad de Girona; EspañaFil: Mutjé. P.. Universidad de Girona; Españ

Acoustic properties of agroforestry waste orange pruning fibers reinforced polypropylene composites as an alternative to laminated gypsum boards

The present paper investigates the acoustic properties of natural fiber reinforced composites. Fibers from orange tree pruning were obtained and subject to different treatments in order to obtain mechanical, thermomechanical and chemi-thermomechanical pulps. These pulps were used as reinforcement for a polypropylene matrix. The obtained composite materials were submitted to acoustical tests in an impedance tubes device. The transmission losses obtained against the fiber content were obtained and discussed. Latter it was researched the influence of the fiber treatments on the soundproof characteristics. A numerical method was used to preview the acoustic insulation of the materials against the sound frequency. Finally the results were compared with that of the most usual lightweight soundproof solutions. (C) 2014 Elsevier Ltd. All rights reserved.Reixach, R.; Rey Tormos, RMD.; Alba Fernández, J.; Arbat, G.; Espinach, FX.; Mutjé, P. (2015). Acoustic properties of agroforestry waste orange pruning fibers reinforced polypropylene composites as an alternative to laminated gypsum boards. Construction and Building Materials. 77:124-129. doi:10.1016/j.conbuildmat.2014.12.041S1241297

Influence of pretreatment and mechanical nanofibrillation energy on properties of nanofibers from Aspen cellulose

The characteristics of cellulose nanofibers (CNFs) depend on many factors such as the raw material, type and intensity of the pre-treatment, and type and severity of the mechanical defibrillation process. The relationship among factors is complex but crucial in determining the final, fit-for-use CNF properties. This study aims to find the relationship between the CNF properties morphology, aspect ratio, nanofibrillation yield, transmittance and cationic demand, and the production process using bleached Aspen thermomechanical pulp as the raw material. Five different types of pretreatments were carried out and five different defibrillation intensities of highpressure homogenization were evaluated. Pretreatments were: PFI refining at 20,000 revolutions, enzymatic hydrolysis with 80 and 240 g of enzyme per ton of dry pulp and TEMPO (2,2,6,6-tetramethylpiperidine-1-oxyl)–mediated oxidation with 5 and 15 mmol of NaClO per gram of dry pulp. From the twenty-five different procedures evaluated, results show that both the pretreatment and the severity of the high-pressure homogenization determined both the fibrillation yield and the CNF morphology. Moreover, the main properties of CNFs (cationic demand, yield, transmittance and aspect ratio) can be estimated from the carboxylic content of the pretreated pulp, which would facilitate the control of the CNF production and their tuning according to the production needs

TENSILE STRENGTH CHARACTERISTICS OF POLYPROPYLENE COMPOSITES REINFORCED WITH STONE GROUNDWOOD FIBERS FROM SOFTWOOD

The behavior of stone groundwood / polypropylene injection-molded composites was evaluated with and without coupling agent. Stone groundwood (SGW) is a fibrous material commonly prepared in a high yield process and mainly used for papermaking applications. In this work, the use of SGW fibers was explored as a reinforcing element of polypropylene (PP) composites. The surface charge density of the composite components was evaluated, as well as the fiber’s length and diameter inside the composite material. Two mixing extrusion processes were evaluated, and the use of a kinetic mixer, instead of an internal mixer, resulted in longer mean fiber lengths of the reinforcing fibers. On the other hand, the accessibility of surface hydroxyl groups of stone groundwood fibers was improved by treating the fibers with 5% of sodium hydroxide, resulting in a noticeable increase of the tensile strength of the composites, for a similar percentage of coupling agent. A new parameter called Fiber Tensile Strength Factor is defined and used as a baseline for the comparison of the properties of the different composite materials. Finally the competitiveness of stone groundwood / polypropylene / polypropylene-co-maleic anhydride system, which compared favorably to sized glass-fiber / polypropylene GF/PP and glass-fiber / polypropylene / polypropylene-co-maleic anhydride composite formulations, was quantified by means of the fiber tensile strength factor

Recovered and recycled Kraft fibers as reinforcement of PP composites

Recycled Kraft fibers coming from old sacs were used for the preparation of polypropylene (PP) composites. Composites up to 50 wt.% of reinforcement were obtained and maleated polypropylene (MAH-PP) was used as coupling agent for improving the fiber-matrix compatibility and adhesion. In the present work, the mechanical properties of the obtained composites as well as the evaluation of interfacial behavior are studied. The results discussion is based on the analysis of the mechanical properties of composites, measurements of surface polarity, specific surface, fiber dimensions, spectroscopic and microscopic analysis. Different adhesion mechanisms at fiber-matrix interface must be presumed depending on the existence of MAH-PP coupling agent, as revealed the analysis of the modification reaction and the conducted proofs. The results showed that the addition of maleated polypropylene favored the incorporation of the relatively high amounts of this natural reinforcement and promoted the stress transfer inside the composite. Thus, an increase up to 50 wt.% of recycled Kraft fibers increased two times the ultimate tensile strength of the non-reinforced matrix. Additionally, the intrinsic mechanical properties of recycled Kraft fibers are deduced by means of modified rule of mixtures and compared to those available in the literature. Finally, an approach of the industrial competitiveness of these fibers, daily present in the market, with respect to E fiberglass is carried out. For this reason a comparison between the mechanical properties and the final cost of PP composites from recycled Kraft fibers or E fiberglass has been considered. © 2007 Elsevier B.V. All rights reserved.Fil: Vilaseca, F.. Universidad de Girona; EspañaFil: Méndez, J.A.. Universidad de Girona; EspañaFil: López J.P.. Universidad de Girona; EspañaFil: Vallejos, María Evangelina. Universidad de Girona; España. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Nordeste. Instituto de Materiales de Misiones. Universidad Nacional de Misiones. Facultad de Ciencias Exactas Químicas y Naturales. Instituto de Materiales de Misiones; ArgentinaFil: Barberà, L.. Universidad de Girona; EspañaFil: Pèlach, M.A.. Universidad de Girona; EspañaFil: Turon, X.. Universidad de Girona; EspañaFil: Mutjé, P.. Universidad de Girona; Españ

Low environmental impact bleaching sequences for attaining high brightness level with eucalyptus SPP pulp

The alternatives used for minimizing the usage of chlorine dioxide in bleaching sequences included a hot acid hydrolysis (Ahot) stage, the use of hot chlorine dioxide (Dhot) and ozone stages at medium consistency and high consistency (Zmc and Zhc), in addition to stages with atmospheric hydrogen peroxide (P) and pressurized hydrogen peroxide (PO). The results were interpreted based on the cost of the chemical products, bleaching process yields and on minimizing the environmental impact of the bleaching process. In spite of some process restrictions, high ISO brightness levels were kept around 90 % brightness. Additionally, the inclusion of stages like acid hydrolysis, pressurized peroxide and ozone in the bleaching sequences provided an increase in operating flexibility, aimed at reducing environmental impact (ECF Light). The Dhot(EOP)D(PO) sequence presented lower operating cost for ISO brightness above 92 %. However, this kind of sequence was not allowed for closing the wastewater circuit, even partially. For ISO brightness level around 91%, the AhotZhcDP sequence presented a lower operating cost than the others