This work is inspired by the current European policies that aim to reduce plastic waste. This is especially true of the packaging industry. The biocomposites developed in the work belong to the group of environmentally friendly plastics that can reduce the increasing costs of environmental fees in the future. Three types of short fibers (flax, hemp and wood) with a length of 1 mm each were selected as fillers (30% mass content in PHBV). The biocomposites were extruded and then processed by the injection molding process with the same technical parameters. The samples obtained in this way were tested for mechanical properties and quality of the molded pieces. A significant improvement of some mechanical properties of biocomposites containing hemp and flax fibers and quality of molded pieces was obtained in comparison with pure PHBV. Only in the case of wood–PHBV biocomposites was no significant improvement of properties obtained compared to biocomposites with other fillers used in this research. The use of natural fibers, in particular hemp fibers as a filler in the PHBV matrix, in most cases has a positive effect on improving the mechanical properties and quality of molded pieces. In addition, it should be remembered that the obtained biocomposites are of natural origin and are fully biodegradable, which are interesting and desirable properties that are a part of the current trend regarding the production and commercialization of modern biomaterials.
This study assessed the impact of alkali treatment of hemp and flax fibers on mechanical properties (determined by means of the uniaxial tensile test, impact tensile strength test and hardness test), processing properties (the course of the extrusion and injection process) and usable properties (shrinkage of molded pieces, degree of water absorption) of biocomposites on the base of poly (3-hydroxybutyric-co-3-hydroxyvaleric acid) (PHBV) biopolymer. For this purpose, 1 mm of length flax and hemp fibers was surface-modified by means of aqueous solution of NaOH (sodium hydroxide) with concentrations of 2%, 5% and 10%. The composites were made using the extrusion technology. The test specimens were produced by injection molding technology. In total, eight types of biocomposites with modified and non-modified fibers were produced, and each biocomposite contained the same filler content (15 wt.%). Their properties were compared in some cases with pure PHBV polymer. In the case of biocomposites filled with hemp fibers, it was noted that an increase of the alkalizing solution concentration improved most of the tested properties of the obtained biocomposites. On the other hand, in the case of flax fibers, there was a significant decrease in most of the mechanical properties tested for the composite containing fibers etched by 10% NaOH solution. The obtained results were verified by examining fibers and the destroyed specimens with a scanning electron microscope (SEM) and an optical microscope, which confirmed, especially, the significant geometry changes of the flax fibers etched by 10% NaOH solution. This procedure also resulted in a significant change of processing properties—a composite of this fiber type required about 20 °C lower temperature during the extrusion and injection molding process in order to obtain the right product. These results lead to the important conclusion that for each filler of the plant-origin and polymer matrix, the fiber alkalization method should be selected individually in order to improve the specific properties of biocomposites.
The fibers orientation in the polymer matrix is an important factor determining mechanical properties of products made of composites by means of an injection molding process. The fibers arrangement has an effect on shrinkage of the composite and the dimensional accuracy of molded piece. The knowledge of fiber orientation can determine the proper dimensions and design of the molding cavities and then correct some of physical and mechanical properties of the molded piece. The orientation of fillers depends on many factors, among which the important role play processing parameters including the injection speed. The aim of this study was to assess the orientation of the fibers in wood-polymer composite on the selected examples. The knowledge and proper use of micromechanical models allow to evaluate the fibers flow and their orientation in polymer matrix. The research was performed both for numerical simulations and experimental studies for results verification.
This paper aims to experimentally determine the properties of the poly [(3-hydroxybutyrate)-co-(3-hydroxyvalerate)]—(PHBV)—30% hemp fiber biocomposite, which is important in terms of numerical simulations of product manufacturing, and to evaluate the mechanical properties by means of micromechanical modeling. The biocomposite was manufactured using a single-screw extruder. Specimens for testing were produced by applying the injection molding technology. Utilizing the simulation results of the plastic flow, carried out by the Moldflow Insight 2016 commercial software and the results of experimental tests, the forecasts of selected composite mechanical properties were performed by means of both numerical and analytical homogenization methods. For this purpose, the Digimat software was applied. The necessary experimental data to perform the calculations for the polymer matrix, fibers, and the biocomposite were obtained by rheological and thermal studies as well as elementary mechanical tests. In the paper, the method of determining selected properties of the biocomposite and the method of forecasting its other properties are discussed. It shows the dependence of the predicted, selected properties of the biocomposite on the filler geometry assumed in the calculations and the homogenization method adopted for the calculations. The results of the work allow for the prediction of properties of the PHBV biocomposites—hemp fiber for any amount of filler used. Moreover, the results allow for the estimation of the usefulness of homogenization methods for the prediction of properties of the PHBV-hemp fiber biocomposites. Furthermore, it was found that for the developed and tested biocomposites, the most effective possibility of mechanical properties prediction is using the Mori-Tanaka homogenization model, which unfortunately has some limitations.
Abstract:In this paper a novel way of a digital analysis of fibers orientation with a five-step algorithm was presented. In the study, a molded piece with a dumbbell shape prepared from wood-polymer composite was used. The injection molding process was examined in experimental and numerical way. Based on the developed mathematical algorithm, a significant compliance of fiber orientation in different areas of the molded piece was obtained. The main aim of this work was fiber orientation analysis of wood-polymer composites. An additional goal of this work was the comparison of the results reached in numerical analysis with results obtained from an experiment. The results of this research were important for the scientific and also from the practical point of view. In future works the prepared algorithm could be used to reach optimal parameters of the injection molding process.
Cukrzyca to grupa chorób metabolicznych, w których występuje hiperglikemia będąca skutkiem niewydzielania lub niewłaściwego wydzielania insuliny. W przypadku osób, które zwracają się do lekarza, żeby potwierdzić zachorowanie na cukrzycę, należy stwierdzić jedno z następujących zaburzeń: StreszczenieZ doniesień naukowych wynika, że odpowiedni styl życia ma wpływ na zapobieganie wystąpienia cukrzycy typu 2. Głównym powodem zachorowania na ten rodzaj cukrzycy jest insulinooporność, której przyczynę upatruje się w niewłaściwej diecie, siedzącym trybie życia oraz długotrwałym stresie. Spożywanie dużej ilości cukrów prostych, które znajdują się m.in. w słodyczach, przekąskach i białym pieczywie, doprowadza do hiperglikemii, zwiększenia wydzielania insuliny, a co za tym idzie -do wyczerpania jej zapasów w komórkach β wysp trzustkowych, zmniejszenia wrażliwości mięśni szkieletowych oraz innych tkanek na jej działanie. Siedzący tryb życia, spędzanie wielu godzin przed komputerem czy telewizorem nasilają wspomniany patomechanizm, gdyż mięśnie nie pracując, nie mogą zużywać nadmiaru przyjmowanej glukozy. Stres w domu lub pracy dodatkowo powoduje utrzymywanie się dużego stężenia glukozy, doprowadzając do zmniejszenia wrażliwości tkanek na insulinę oraz nasilając dodatkowo chęć podjadania. Przestrzeganie diety bogatej w węglowodany złożone, które znajdują się w chlebach gruboziarnistych, razowych makaronach, warzywach, zmniejsza występowanie hiperglikemii i jej dalszych skutków. Prowadzenie aktywnego trybu życia, umiarkowany, a częsty wysiłek fizyczny oraz unikanie stresu są podstawą zapobiegania cukrzycy typu 2. Stosowanie tych zaleceń u osób cierpiących już na cukrzycę typu 1 lub 2 umożliwia wyrównanie glikemii, lepszą kontrolę choroby, a więc poprawę jakości życia pacjentów (Piel. Zdr. Publ. 2015, 5, 4, 63-67).Słowa kluczowe: cukrzyca, aktywność fizyczna, dieta, otyłość, insulinooporność. AbstractThe scientific research indicates that a healthy lifestyle is significant for type 2 diabetes prevention. The main reason of type 2 diabetes is insulin resistance caused by poor nutrition, sedentary lifestyle, and chronic stress. Excess sugar consumption, including sweets, snacks and white bread leads to hyperglycemia. In consequence, the increase of insulin production results in the exhausting accumulation of this hormone in a pancreas, decreasing the sensitivity of skeletal muscles and other tissues to it. Sedentary lifestyle, spending long hours at the computer or TV, intensifies this pathomechanism. Muscles do not work and cannot consume the excess of glucose. In addition, stress at work or home causes the steady retention of a high level of glycemia leading to the decrease of the sensitivity of tissues to insulin, consequently, intensifying the desire for having snacks. A diet rich in complex carbohydrates, such as: coarse bread, whole wheat pasta and vegetables reduces the occurrence of hyperglycemia and its further consequences. Keeping an active lifestyle, avoiding stress, doing moderate and frequent exercises are essent...
The paper presents selected properties of the developed biocomposites based on PHBV poly (3-hydroxybutyric co-3-hydroxyvaleric acid) biopolymer. The PHBV biopolymer is obtained by the copolymerization of 3-hydroxybutyric acid and 3-hydroxyvaleric acid. The biopolymer used for the tests contained 8% of poly (3-hydroxyvaleric acid). For the preparation of the composite, three types of fillers: wood flour, hemp fiber and flax fiber were used in search for the best possible mechanical properties of composite. During the selection of filler types, the availability and price in the geographical area of Poland as well as mechanical properties were taken into account. Fillers were alkalized and fiber modification parameters were determined. The following mass percentages of fillers in the tests: 15%, 30%, 45%, 50% and various fiber lengths were used. To produce the biocomposites the single-and twin screw extruders made by Zamak Company were used. The initial processing parameters were determined using DSC thermogram analyses. The technological parameters depended on the type of filler and its percentage content. The best mechanical properties, compared to generally available polymers like PP, PE, PVC or PS were obtained for the composite with hemp fiber. The developed composite is completely biodegradable. Better mechanical properties of produced composite in relation to e.g. PE or PP allow using it for the production of parts that are used in various branches of the economy.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.