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Some Exploitation Properties of Wood Plastic Hybridcomposites based on Polypropylene and Timber Industry Waste
No full textDuring last 20-30 years many researchers have paid attention to studies of properties of the
wood plastics composites (WPC). A lot of works are close related to investigations of
exploitation properties of wood fibres or flour containing polyolefine composites [1]. The
most useful from wide selection of polyolefines are polypropylenes, but as reinforcement of
WPC often are used different waste materials comprising lignocellulose fibres. Such materials
also are a lot of waste which produce timber industry. In this work we approbated for
reinforcing of polypropylene (PP) one of the waste product of plywood technology-plywood
sawdust (PSWD), which contain wood fibres fractions with different length (l). The main
fraction (50% ) have fibres with length l=0.5-1 mm. Our previous studies [2] showed that
PSWD is promising filler for PP reinforcing. That additions of the PSWD up to 40-50 wt.%
increase WPC tensile and flexural modulus, but decrease deformation ability of PP matrix,
impact strength, water resistance and fluidity of composite melts. Modification of the
composites with interfacial modifier maleated polypropylene (MAPP up to 5-7 wt.%)
considerably improve all the above-mentioned properties. One more way how to make better
properties of the WPC is to form hybridcomposites. Very popular WPC modifiers are
nanoparticles additions like nanoclays which increases WPC physical-mechanical properties,
microhardness, water resistance and diminish combustibility. The goal of this study is to
investigate nanoclays influence on PSWD containing WPC composites physical-mechanical
properties. As polymer matrix PP type Mosten MA-712 was used, but as modifiers Licocene
PP MA-7452 and nanoclays grade Cloisite 15A. Composites were prepared by mixing on two
rolls mill, then cooled, granulated and pressed in 1 mm thick sheets for tensile strength
measurements (ASTM D 638M). Tensile, flexural and impact strength tests were done.for
standard specimens (EN ISO 178 and ASTM D 256M respectively) bars produced by
injection moulding. Melt fluidity (melt flow index-MFI) was estimated by standard ASTM D
1238. Water resistance measurements were done according to the standard ASTM D 570-88.
From previous [2] studies as optimal composition of the composite containing PSWD was
chosen PP+40 wt.%WF+7.0 wt.% MAPP. Changing nanoclays amout and controling tensile,
flexural and impact strength properties was noted optimal concentration of nanoclays in the
composite (3wt.%). Then was examined MAPP influence on mentioned properties and
optimal concentration was gained 7wt.%. As result of these studies was found optima
l
composition of hybrid composite based on polypropylene and 40 wt.% of PSWD+3wt.%
nanoclay+7wt.% MAPP which have better mechanical properties than composites without
nanoclays. Additons of nanoclays improve also fluidity of investigated hybrid composites
(MFI reaches 6g/10min) and increase of water resistance
Membrane Extraction of Chromium(VI) by Tri-n-Octylamine during Electrodialysis
No full textA new process for chromium(VI) removal from aqueous solutions is presented. The process includes the transport of chromium(VI) anionic complexes from chloride acidic solutions through bulk liquid membranes at galvanostatic electrodialysis. Solutions of tri-n-octylamine with admixtures of di(2-ethylhexyl)phosphoric acid in 1,2-dichloroethane have been used as the liquid membranes. Effects of current density, chromium(VI) and acid concentration in the feed solution, carrier and admixture concentration in the liquid membrane, type of acid in the stripping solution are studied, and optimum conditions are determined. Practically complete removal of chromium(VI) from the feed solution containing 0.01 mol/L K2Cr2O7 is achieved during 1.0 − 4.0 hours of electrodialysis. Maximum stripping degree of ~ 90 % is obtained under optimum conditions. A possibility of effective single-stage removal of chromium(VI) into dilute solutions of hydrochloric, sulphuric, perchloric, phosphoric acids and water is demonstrated
Dielectric and Mechanical Relaxation in the Modified Carbon Nanofillers Containing Polyvinyl Alcohol Composites
No full textConsequently in the current research carbon nanofiller (polyvinylpyrrolidone treated
graphite, graphite oxide, reduced graphite oxide) containing polyvinyl alcohol composites have
been obtained via solvent casting route. The content of carbon nanofillers in the polyvinyl alcohol
matrix has been changed within the borders between 0 and 5 wt. %. Technological parameters of
the method for manufacturing of polyvinyl alcohol composites with aforementioned carbon
nanofillers have been optimized. The effect of the concentration of polyvinylpirrolidone on the
dispersion ability of the carbon nanofillers in the polyvinyl alcohol matrix has been evaluated.
Besides it structure, as well as dielectric and mechanical relaxation properties of polyvinyl alcohol –
carbon nanofiller composites have been investigated
The Transition to Chaos and Criteria of Chaotic Behavior in Dynamical Systems with Linear and Nonlinear Damping
No full textThe achieved result is the elaboration of the basic theory for searching chaotic oscillations and nonlinear effects based on the concepts of periodic skeletons, complete bifurcation groups and method of rare attractors. The chaotic attractor possesses the characteristic amount of periodic skeletons and order of bifurcation groups. The approach allows us to forecast and to find new groups with rare catastrophic or rare useful phenomena with chaotic attractors in the nonlinear driven systems with linear and nonlinear damping. The results of work can be used in the engineering recommendations on how to use complex periodic, chaotic and rare attractors in the engineering systems for the purpose of favorable usage of nonlinear effects in the vibro-technology. It can also be used to forecast catastrophic situations and chaotic oscillations in the mechanics or other nonlinear dynamic systems
Nanocoating Surface Wear Assessment Using Methods of Non-Contact Scanning Probe Microscopy
No full textWear resistance of machine parts is the main exploitation index of the quality of the design, and application of nanocoatings provides effective resistance to wear and ensures long service life of machine parts. Since any surface loses its mechanical characteristics in the course of operation, it is expedient to control the surface in order to determine its state. This article describes the methods of measuring the state of nanocoatings, specifically wear, using non-contact methods, with the goal to already use a specific method for determining the durability of the investigated nanocoatings in the future
Development of Lifetime Data Management Algorithm for Power Transformers
No full textThe paper provides a short insight into the structure of Latvian high voltage transmission network, describing existing system of complex diagnostic and analyzing maintenance data to reveal the most frequent locations of faults in power transformers. Modified inspection schedule of power transformers is described that serves as a base for developing effective algorithm for assessment of technical condition by using transformers’ maintenance data, considering the results of diagnostic tests and including prediction of remaining service life. Calculations, performed by Weibull cumulative distribution function, for determining service life of the tap changer of 2 power transformers are presented as a case study
Informācijas un komunikācijas tehnoloģijas kā līdzeklis starpnozaru disciplīnu izveidei
No full textRaksta mērķis ir teorētisks pētījums par starpdisciplīnu ietekmi uz mācību procesu. Darba uzmanības centrā ir trīs studiju kursa komponenti – informācijas un komunikācijas tehnoloģijas (IKT), studiju kurss/mācību priekšmets un pedagoģija.
Starpdisciplīnu ietekmes rezultātā radās jauns IKT pielietojums un noformējās jauns e-studiju kurss. Šajā rakstā e-studiju kurss ir svešvalodas mācīšana un mācīšanās, pielietojot IKT, kā svešvaloda izvēlēta angļu valoda.
Rakstā analizētas mūsdienu latviešu un ārzemju e-kursa interpretācijas
Concrete Bridge Deterioration Caused by De-Icing Salts in High Traffic Intensity Road Environment in Latvia
No full textDesign for durability of road infrastructures is becoming increasingly important in view of its large impact on economics. Reinforcement corrosion is the most common cause of concrete deterioration of bridge structures in Latvia. The ingress of chlorides is often considered to be the major threat to durability of concrete structures. During the winter season de-icing salts are spread out on roads to avoid formation of ice and ensure the anti-sliding properties of the road surface. The melting water mixes with de-icing salt and is splashed and sprayed on reinforced concrete pier structures by passing vehicles. Absorbed water with chloride ions initiates and accelerates the reinforcement corrosion process. This paper highlights the results of investing accumulation of chlorides in reinforced concrete bridge piers located near high-intensity roads in Latvia. The chloride contents were determined on different surfaces of reinforced concrete piers. Environmental conditions were analysed and prediction of remaining service life for chloride induced reinforcement corrosion was performed
Procedures for Calculation of 3D Nanometric Surface Texture Parameters
No full textIn this article the method and algorithms for three
dimensional digital evaluation of surface nanometric texture is
proposed. Description of machined surfaces is based on the
model containing a certain number of single asperities. For
calculation of texture parameters the array of surface point
elevations is used. Such array of point heights may be obtained
by parallel scanning of surface along a specific number of surface
profiles. Any kind of measuring equipment may be used for
scanning