G. Hinrichsen

Biofibres, biodegradable polymers and biocomposites : An overview

Recently the critical discussion about the preservation of natural resources and recycling has led to the renewed interest concerning biomaterials with the focus on renewable raw materials. Because of increasing environmental consciousness and demands of legislative authorities, use and removal of traditional composite structures, usually made of glass, carbon or aramid fibers being reinforced with epoxy, unsaturated polyester, or phenolics, are considered critically. Recent advances in natural fiber development, genetic engineering and composite science offer significant opportunities for improved materials from renewable resources with enhanced support for global sustainability. The important feature of composite materials is that they can be designed and tailored to meet different requirements. Since natural fibers are cheap and biodegradable, the biodegradable composites from biofibers and biodegradable polymers will render a contribution in the 21st century due to serious environmental problem. Biodegradable polymers have offered scientists a possible solution to waste-disposal problems associated with traditional petroleum-derived plastics. For scientists the real challenge lies in finding applications which would consume sufficiently large quantities of these materials to lead price reduction, allowing biodegradable polymers to compete economically in the market. Todays much better performance of traditional plastics are the outcome of continued RD however the existing biodegradable polymers came to public only few years back. Prices of biodegradable polymers can be reduced on mass scale production; and such mass scale production will be feasible through constant R&D efforts of scientists to improve the performance of biodegradable plastics. Manufacture of biodegradable composites from such biodegradable plastics will enhance the demand of such materials. The structural aspects and properties of several biofibers and biodegradable polymers, recent developments of different biodegradable polymers and biocomposites are discussed in this review article. Collaborative R&D efforts among material scientists and engineers as well as intensive co-operation and co-ordination among industries, research institutions and government are essential to find various commercial applications of biocomposites even beyond to our imagination.

Surface modification of jute and its influence on performance of biodegradable jute-fabric/Biopol composites

Surface modifications of two varieties of jute fabrics, i.e. hessian cloth (HC) and carpet backing cloth (CBC), involving dewaxing, alkali treatment, cyanoethylation and grafting, have been made with a view to their use as reinforcing agents in composites based on a biodegradable polymeric matrix, Biopol. The chemically treated fabrics are characterized by Fourier-transform infrared spectroscopy (FTIR) and thermogravimetric analysis (TGA). The effects of different fibre surface treatments and amounts of fabrics on the performance of the resulting composites are investigated. Mechanical properties such as tensile strength, bending strength and impact strength increase in comparison to pure Biopol as a result of reinforcement with jute fabrics. More than 50% enhancement in tensile strength, 30% in bending strength and 90% in impact strength of the composites relative to pure Biopol sheets have been observed under the present experimental conditions. Scanning electron microscopy (SEM) investigations show that surface modifications improve the fibre/matrix adhesion. From degradation studies we find that after 150 days of compost burial more than 50% weight loss of the jute/Biopol composite occurs.

Surface characterization of natural fibers; surface properties and the water up-take behavior of modified sisal and coir fibers

The influence of fiber surface modifications like dewaxing, alkali treatment and methyl methacrylate grafting on the thermal and electrokinetic properties of coir (coconut) and sisal fibers has been investigated. Additionally scanning electron microscopy was performed to follow changes in the fiber surface morphology. Electrokinetic properties were measured using the streaming potential method. The measured time dependence of the ζ-potential offers the possibility to characterize the water up-take, i.e. the swelling behavior of natural fibers. The investigated natural fibers, as expected, contain dissociable surface functional groups as verified by measuring the pH-dependence of the ζ-potential. The influence of fiber surface modifications on the ζ-potential was compared to the influence of fiber surface modifications on measured (tensile and flexural strength) mechanical biocomposite properties. The ζ-potential measurement is a very efficient technique to investigate the various changes effected by different surface modifications, which are necessary to improve the compatibility of such natural fibers and polymer matrices for making eco-friendly and low cost composite materials.

Effect of chemical modification on the performance of biodegradable jute yarn-Biopol® composites

Jute yarn-Biopol® composites are prepared by hot-press moulding technique. Jute yarns of two varieties (7.36 lbs/spy and 11.86 lbs/spy) are used for composite fabrications. Effects of temperature, yarn amount, chemical modification like dewaxing (defatting), alkali treatment, graft copolymerization and orientation of yarn winding on the performance of resulting composites have been investigated. The mechanical properties like tensile strength, bending strength, impact strength and bending-E-modulus increased substantially in comparison to pure Biopol® as a result of reinforcement with jute yarns. The most remarkable observations of our present investigations include more than 150% enhancement in tensile strength, impact strength, bending-E-modulus and more than 50% enhancement in bending strength of the resulting composites as compared to pure Biopol® sheets. Amount of jute yarn, chemical modifications and measurement of mechanical properties on the direction of winding of yarns contribute significantly to the mechanical properties of resulting composites.

Influence of novel coupling agents on mechanical properties of jute reinforced polypropylene composite

The modern technology relies heavily on the development of new materials having superior properties, such as mechanical and thermal properties along with toughness. Fiber reinforced composites have successfully proven their versatile qualities because of their specific properties e.g. high mechanical properties, stiffness, light weight etc. The potential of natural fiber based composites prepared mainly from jute as reinforcing fiber in polymer matrix has received much attention among the composite scientists [1–3]. Jute fibers are polar and of hydrophilic nature due to the presence of several hydroxyl groups in their cellulosic backbone. However, this is the most important disadvantage of using natural fiber in non-polar polymer like polypropylene (PP). Selection of proper coupling agents is important to improve the fiber-matrix interaction. The purpose of this study reported here is to investigate the effect of two monomers HEMA and EHA used as coupling agents on the performance of jute fabric (hessian cloth) PP composite. Hessian cloth (jute fabrics) was modified with 2hydroxy ethylmethylacrylate (HEMA) and 2-ethylhexylacrylate (EHA) by soaking in solution of different concentration of monomer in methanol for 5 min. Dicumyl peroxide was used as thermal initiator. The treated hessian cloth (HC) was dried at ambient temperature. Hessian cloth-polypropylene (Vestolen GmbH, Germany) composite was prepared by sandwiching two layers of HC and three layers of PP. The prepreg temperature, pressure and pressing time were 180 ◦C, 0.2 MPa and 5 min, respectively. The prepreg samples were cooled to room temperature, then cut to desired size in the mold and again heat-pressed at 130 ◦C for 5 min under 20 MPa pressure to get final composite. Tensile strength (TS) and three point bending strength (BS) of the composites were studied following DIN 53455 and DIN 53452 standard methods, respectively. The tensile as well as bending strength of the composite thus formed are shown in Fig. 1 as a function of monomer concentration. It is observed that

Mechanical studies of methyl methacrylate treated jute and flax fibers under UV radiation

Jute and flax fibers were improved under UV radiation using methyl methacrylate (MMA) mixed with methanol (MeOH). There was a 30% enhancement of tenacity for these fibers against 3–8% grafting of MMA with the fibers. Incorporation of 1% of one of the additives 2-ethyl hexyl acrylate (EHA), urea (U), or N-vinylpyrrolidone to MMA + MeOH solution increased the grafting very slightly and enhanced the tenacity of jute by 110% and flax by 50%. Enhancement of elongation of the treated fibers was up to 30%.

Study on physical and mechanical properties of biopol-jute composite

Abstract A Biopol-jute composite (BJC) was prepared using a hot-press treatment by reinforcing the Biopol polymer with hessian cloth (jute fabrics) placed in between the layers of Biopol polymer films. Both the tensile and bending strengths of the composite increased substantially, in comparison to the pure Biopol. Jute fabrics were treated with different additives to improve the composite properties. Among them, 2-ethyl hexyl acrylate (3%), γ-rnethacryloxypropyltrimethoxy silane (2%), and trimethoxy vinyl silane (0.5%) were found to be effective in enhancing tensile properties up to 80% with respect to Biopol. Mixed additives increased the tensile properties of the composites to some extent but not as much as the single additive did.

Flax and cotton fiber reinforced biodegradable polyester amide composites, 1. Manufacture of composites and characterization of their mechanical properties

Biodegradable composites consisting of flax (FF) and cotton (CT) fiber mats and poly(ester amide) (PEA) films were hot pressed using the film stacking process. The process parameters press temperature, pressure, press time in the tool, and drying conditions of fiber and matrix were optimized with regard to the mechanical properties as well as the visual quality of the composites. Press temperature turned out as being the most important quantity. The mechanical properties of the composites were characterized. Biologisch abbaubare Verbundwerkstoffe aus Flachs- und Baumwollfasern sowie Polyesteramid(PEA)-Folien wurden nach dem Filmpresverfahren hergestellt. Die Verfahrensparameter, wie Prestemperatur, Presdruck, Verweilzeit in der Presform und Trocknungsbedingungen von Faser und Folie, wurden im Hinblick auf die mechanischen Eigenschaften und das Aussehen der Verbunde optimiert. Es stellte sich heraus, das die Prestemperatur den wichtigsten Einflusparameter darstellt. Die mechanischen Eigenschaften der Verbunde wurden gemessen.

On the deformation mechanisms of oriented PET and PP films under load

Uniaxially orienred semicrystalline poly(ethylene terephthalate) (PET) and poly(propylene) (PP) films were loaded parallel to draw direction at various temperatures. Changes in the submicroscopical structure of the films under load were examined by small and wide-angle x-ray scattering (SAXS; WAXS) and birefringence measurements. WAXS measurements reveal a decrease of the initial high orientation of the chains in the crystallites during deformation. Simultaneously, an increase of the birefringence was detected, indicating an orientation of chains in the amorphous regions. The alteration of the long period reflections in the SAXS patterns give strong evidence that lamellar stacks with different orientation angles according to load direction are present. Depending on the orientation of stacks, the contribution of lamellar separation to sample deformation alters, giving rise to different amounts of density changes in the stacks. Absolute intensity measurements of SAXS using a Kratky apparatus reveal that lamellar separation occurs preferentially below or in the range of the glass-transition temperature at small strain. With increasing strain and temperatures above the glass-transition slip deformation mechanisms become more important. The formation of microvoids was observed at strain near to elongation at break below or in the range of glass-transition temperature.

On nonorientation drawing of polyethyleneterephthalate (PET)

SummaryThe drawing behaviour of amorphous PET-films in the temperature interval between room temperature and 160 °C has been investigated in the present paper. Measurements of stress-strain behaviour, of birefringence, of density, of heat of fusion, of melting point, of glass temperature, of crystal structure and of superstructure prove that drawing temperature and drawing velocity posses a determining influence on forming morphology and technological properties. Within the temperature interval from 85 to 105 °C using low drawing velocities a drawing process of films without any molecular orientation is observed.ZusammenfassungDas Verstreckverhalten von amorphen PET-Folien im Temperaturbereich von Raumtemperatur bis 160 °C wird in der vorliegenden Arbeit untersucht. Messungen des Spannungs-Dehnungs-Verhaltens, der Doppelbrechung, der Dichte, der Schmelzenthalpie, des Schmelzpunktes, der Einfriertemperatur und der Kristall- und Überstruktur zeigen, daß Verstrecktemperatur und Verstreckgeschwindigkeit einen entscheidenden Einflußβ auf die entstehende Morphologie und die technologischen Eigenschaften besitzen. Im Temperaturbereich zwischen 85 und 105 °C beobachtet man bei kleinen Verstreckgeschwindigkeiten eine Verstreckung der Folien ohne molekulare Orientierung. nt]mis|With 13 figures and 1 table