Volume 52, Issue 1

Abstract: A number of inventions, and theoretical and experimental research allowed to increase the thermal homogenous melt flow-rate delivered by the screw. On the other hand, quality of the extruded product depends on geometrical considerations of the extrusion head and on a large scale on the rheological behaviour (viscous and elastic) of the polymer melt. Non-harmonizing the design of the screw-barrel unit with the construction of the extrusion head can lead to low-quality products. In this paper, the extrusion head working field was drawn based on limitations imposed by the screw-barrel unit, i.e.: maximum flow-rate assuring required melt thermal homogeneity; - maximum flow-rate for which the heating system on the barrel (and screw, eventually) assures the extrusion temperature; -minimum flow-rate corresponding to screw diameter. Keywords: extruder head working field, extruder performance, rheological behaviour, screw-barrel unit

Abstract: The spectral shifts in the visible electronic absorption spectra of B3 in water-ethanol mixtures were correlated with the macroscopic parameters (refractive index and electric permittivity) of the solvents. The contributions of the intermolecular interactions upon the spectral shifts as a function of the solvent macroscopic parameters were expressed by multiparameter regressions. The dependence of the wave number in maximum vibronic band of B3 vitamin on the solvent macroscopic parameters demonstrates the prelevance of the orientation interactions in the studied solutions. Some electro-optical parameters and global descriptors of B3 vitamin were computed by Spartan program. In present, the assimilation of the B3 vitamin copolymeric compounds in medicine and cosmetics must fullfil the complexity of the biological issues that result from using them. We note that the B3 vitamin can be incorporated in the polymeric structures to improve its functions. Keywords: solvents effects, absorption spectra, B3 vitamin

Abstract: Protonation, quaternization and addition reactions of poly(N-vinylimidazole) to the imidazole nitrogen atom in the position 3 to obtain the corresponding ionic derivatives were studied by NMR Spectroscopy. Information and data about the reaction type and product microstructure are presented. The chain tacticity is a special structure aspect which was in detail studied by means of proton and carbon NMR spectra confirming that the chain configuration is not modified by any of the three polymer-analogous reactions. Keywords: poly(N-vinylimidazole); polyelectrolytes; benzyl chloride; trifluoroacetic acid; acrylic acid; chain tacticity; polymer microstructure

Abstract: This paper, intended to continue the previous work under the same title, published in the previous number – aims at presenting the experimental results, obtained by laboratory tests, referring to the influence of the massic percentage of the hemp hurds within the composites, as well as to the influence of the participation percentages of the filling materials (cement, lime, sand, plaster etc.), on the thermal-transfer factor. The experimental results place thereby this composite in a position comparable to other construction materials; which emphasizes the importance of this composite, with a view to its being used as construction material, both as boards (for lining) and as blocks (for filling). The analysis of the experimental results shows that this type of composite can be ”programmed” and ”controlled” in terms of thermal-transfer factor, through the massic participation percentage of the hemp hurds. In this way, one can extend the use of these composites over constructions in areas with variable temperature differences, especially in the cold season. Moreover, by these experimental values, one can devise a methodology for sizing the construction elements, based on thermal-transfer factor to be achieved and, implicitly, on the thermal insulation capacity to be provided by the respective construction. Keywords: composite, hemp hurds, thermal-transfer factor

Abstract: This paper presents an analysis of a composite cell at a micro level. The authors modeled the interface between a micro sphere and a polymeric matrix for two cases: an interface characterized by a strong bond between the two involved bodies and an interface with low friction between the micro sphere and the polymeric matrix. Even if these models are ideal images of actual composites, the analysis of strain and stress distributions reveals there is a big difference in the mechanical behaviour of the two micro cells. These two cases were analyzed considering a perfect elastic behaviour of involved materials. The shape and the intensity of stress distributions are different for the analyzed models. A weak interface makes the matrix to have restrained zones with high values of von Mises stresses, concentrated on top and bottom of the sphere (on the loading direction). An actual cell of a similar composite (polymeric matrix and a micro sphere as reinforcement) could not have an „extremist” behaviour as these two here presented, but an intermediate one, depending on actual properties of the materials and the nature of the interface. Keywords: micro cell composite, strain distribution, stress distribution

Abstract: In this paper we studied the dyeing behaviour of polyester fibers from recycled polyester and virgin dyed with Foron brilliant rot SGL (CI Disperse Red 121). The amount of dye fixed recycled fiber is higher than that of virgin. Elemental analysis confirms a slight change in the carbon and oxygen content of recycled fiber compared to virgin. Thus the recycled polyester fiber carbon content is higher than virgin fiber in oxygen exchange is less. Dyed samples were treated with AgNO3 in order to confer antibacterial properties. The analyses SEM/EDAX have highlighted the presence of silver ions on the surface of fibers. Keywords: dyeing, recycled PET, virgin PET, disperse dye, antimicrobian effect

Abstract: In this paper the buckling problem is solved for the laminated composite structures from a thin-walled metallic cylindrical shell which is strengthened by fiber-reinforced polymers. The research concerning the influence of composite thickness and fiber orientation on axial critical buckling load is executed. For linear buckling problem, the purposed method is based on modified relations for an orthotropic cylinder. The method was verified by comparison with buckling theories of laminated composite shells and with numerical results based on finite element method. Keywords: lamina/ply, buckling, analytical modelling, numerical analysis

Abstract: This paper analyses the influence of processing temperatures of polyamide 6.6 Grivory type HTV-3H1 noir 9205, polyamide 6.6 Grivory type HTV-45H1 noir 9205 and polyamide 6.6 Grivory type HTV-6H1 noir 9205 on some mechanical properties, when injecting items used in various technical articles. The test-specimens on PA 6.6 Grivory type HTV-3H1 noir 9205 were molded at the following injection temperatures: 310, 320, 330, 340 and 350°C. The test-specimens on PA 6.6 Grivory type HTV-45H1 noir 9205 were molded at the following injection temperatures: 320, 330, 340, 350 and 360°C. The test-specimens on PA 6.6 Grivory type HTV-6H1 noir 9205 were molded at the following injection temperatures: 330, 340, 350, 360 and 370°C. These specimens were tested using methods for determination of the following mechanical properties: tensile strength, Izod impact strength and hardness (Shore). For all these polymers, it was determined that increasing of injection temperature results in insignificant changes of hardness. The Izod impact strength decreases with increasing the injection temperature. After reaching the minimum value, Izod impact strength increases again if the processing temperature is raised further. The tensile strength at break increases with increasing the processing temperature. After reaching the maximum value, tensile strength at break decreases if the processing temperature is raised further. Keywords: polyamide 6.6 (PA 6.6), tensile tests, Izod impact test, Shore Durometer hardness test

Abstract: The present study evaluates the marginal adaptation of fixed partial prosthesis made from resin composite. The main goal is to obtain restorations with excellent aesthetics and extremely high quality which increase the lifetime of the prosthesis system - dental structures. The method allowed the observation of defects that might occur during the technological processing, as well as their correction. It was used the 3D Shape software with which have been achieved scans for the virtual presentation the marginal adaptation. Following the investigation it was showed, that the cementation is extremely important, the errors occurring in this phase are influencing of the final results and behaviour. Composite resin fixed partial prosthesis are restorations which through a correct technology can compete with the ceramic fixed partial dentures. Keywords: aesthetic restoration, marginal adaptation, defects, 3D Shape software

Abstract: In the last years, researches regarding the manufacture of polyamide parts using selective laser sintering process have developed increasingly more because of the advantages this materials offer. This paper was focused on a comparative study about the mechanical proprieties and surface roughness of parts manufactured by Selective Laser Sintering (SLS) from PA2200 powder. Tested parts were achieved on DTM Sinterstation 2000 Machine and EOS Formiga P 100 Machine. The results obtained lead to the conclusion that the mechanical proprieties obtained for the test parts made at 7,5W laser power on DTM Sinterstation 2000 Machine, are close to the results obtained for the test parts made at 30W on EOS Formiga P 100 Machine. Keywords: Polyamide, Selective Laser Sintered, mechanical proprieties, roughness

Abstract: The concern for quality assurance and improvement of the manufacturing processes of plastic materials is of great interest to industry companies offering the guarantee to ensure the conformity, performance, competitiveness and profitability. This paper addresses the importance of improving the quality of plastics manufacturing processes, on high (flow) performance. It illustrates the application of the “Six Sigma” statistical method for injected products that have certain defects / nonconformities, especially dimensional manufacturing. Keywords: plastic products, quality, six sigma, manufacturing process, efficiency

Abstract: The bile duct system has two distinct components: one intrahepatic and another extrahepatic. Both components are subject to large anatomical variability. Knowledge of intraparenchimatous bile duct system distribution is particularly useful for planning and performing major surgical resection and liver transplantation. For this reason, the training of students and medical residents must use liver corrosion casts. On the 130 pieces of hepatic corrosion casts, a percentage of 80.75% of cases have modal typology, homologated by Terminologia Anatomica (1998). On a percentage of 19.25% of the studied cases were found major variations of the intrahepatic bile duct system (classified into four morphological types). In 16.15% of cases, the posterior branch in his passage to the left hepatic duct intersects the main portal fissure. Medial and lateral branches showed no major variations on the studied material. Use of human intrahepatic bile duct system corrosion casts with major anatomical variations, can compensate for lack of clinical material in training of medical students and residents. Keywords: corrosion casts, intrahepatic bile duct system, major variations, training

Abstract: Chitosan (CHI) and poly(acrylic acid) (PAA) polyelectrolyte multilayers were constructed onto silica microparticles with particle diameter of 40 – 60 mm (Daisogel type). The multilayers were subject to two post-treatment strategies: (i) immersion in an aqueous solution with pH = 2.4 for 5 min, followed by immersion for 1 min in water and thermal treatment at 120oC for 60 min and (ii) cross-linking with glutaraldehyde for 60 min. The sorption properties for a cationic dye were investigated taking methylene blue (MB) as a model. The reusability of (CHI/PAA)n multilayers deposited onto Daisogel microparticles in the consecutive sorption/desorption cycles of MB was investigated as a function of the number of double layers and the post-treatment strategy. Keywords: polyelectrolyte multilayer; chitosan; poly(acrylic acid); methylene blue; silica

Abstract: The aim of the study was to compare using atomic force microscopy the surface roughness of three types of composite resins after finishing and polishing procedure with three different systems. A hybrid (Valux Plus, 3M ESPE), a microhybrid (Filtek Z 250, 3M ESPE) and a nonohybrid (Herculite XRV Ultra, Kerr) composite resins were chosen for this study. A number of 28 samples having 10 mm in long ,7 mm in width and 2 mm in high of each composite resin were obtained. The samples were equally split in 4 groups. In control group 7 specimens of each material received no finishing and polishing treatment after being cured under plastic matrix strip. In the first study group 7 samples of each material were finished using fine, safe end taper tungsten carbide bur, 7 samples were finished using superfine needle diamond bur and 7 samples used diamond impregnated one stage polisher. The surface of all composite samples was analyzed using atomic force microscopy. The results were expressed as root mean square surface roughness (nm). The results were statistically analysed using ANOVA and post hoc Bonferroni test at a 0.5 significance level. Significantly differences were obtained in the surface roughness of all three tested composite resins after finishing and polishing when comparing to surface roughness from control group. The one-step diamond abrasive polisher leaded to a significant lower surface roughness for all three composite resins when comparing to the surface roughness when tungsten carbide bur or diamond bur were used. Surface roughness of Valux Plus was higher than that observed for Filtek Z 250 or Herculite XRV Ultra, irrespective of the system used for finishing and polishing. The surface roughness of composite resins is in relation with the type of composite resin and the type of finishing and polishing system. The one-step diamond abrasive polisher was more efficient in obtaining smooth surface when comparing to tungsten carbide bur or diamond bur. The nanohybrid composite resin has a lower surface roughness when comparing to microhybrid and the hybrid composite resin after finishing and polishing. Keywords: composite resins, surface roughness, AFM, finishing and polishing system

Abstract: The polymer foils, obtained from pure and coloured (with cycloimmonium ylids) poly (vinyl) alcohol (PVA) gel, are studied from the optical anisotropy point of view. The dried foils were stretched under heating and their optical birefringence was measured for different degrees of stretching. The changes in the birefringence were correlated with the stretching degree of the polymer foils. The influence of the cycloimmonium ylid structural peculiarities on the coloured foils’ anisotropy is also discussed. Keywords: cycloimmonium benzoyl anilido-benzoyl methylids, optical birefringence, stretched coloured and pure PVA foils

Abstract: Within this paper an experimental analysis of an advanced composite U-beam pultruded profile based on isophtalic polyester resin reinforced with unidirectional glass fibres and overlay veil has been carried out to determine its most important mechanical properties. Tensile tests have been accomplished on specimens cut from the pultruded profile along and transverse to the fibers direction. Over thirty mechanical properties including Young’s moduli, stiffness, load-extension as well as stress-strain distributions determined at maximum load, maximum extension and at break have been determined on a Lloyd Instruments LS-100KPlus materials testing machine. Typical failure mechanisms such as fibres pull-out and delaminations have been noticed. The tests show that this kind of unidirectional glass fibers-reinforced isophtalic polyester resin with overlay veil obtained in the putrusion process is suitable for a large range of applications from the automotive and aerospace industry and put into evidence its strong anisotropy. Keywords: Pultrusion, Isophtalic polyester resin, Mechanical anisotropy, Tensile tests, Stiffness

Abstract: The article presents the importance of using polymer additives in the hydraulic fluid flow, to reduce the friction, to reduce the linear pressure losses, to increase the flowing velocity, to reduce the pumping energy, to increase the efficiency of the hydraulic machines. The article highlights the Toms effect in hydraulic industrial applications. Its also shows experimental results on single stage centrifugal pump operating with additives in water in different poly acryl amide concentration, highlighting the significant increase of the pump efficiency when the concentration does not affect the fluid viscosity. The pump efficiency increased with 8-10% when the polymer additives concentration was 0,04%. Experiments were performed in Hydraulic Laboratory of University Politehnica of Bucharest. Enhancing theoretical and experimental research in this area, based on the viscosity and elasticity anisotropic properties of the polymer additives solutions, can be created new premises for hydrodynamics and hydro power applications. Keywords: polymer additives, hydraulic performances, centrifugal pumps

Abstract: The goal of this paper is to study the creep behaviour of multi-walls carbon nanotubes (1, 3, 5 wt.% MWCNTs) filled polypropylene (PP) through the instrumented indentation technique. Two types of the 3-step indentation test were considered to analyse viscoelastic behaviour through sharp indentation at room temperature. Under the loading conditions, the PP/MWCNTs samples present a time-independent plastic behaviour which must be considered not to under/overestimate the viscoelastic properties. The ratio of residual indentation depth to the maximum indentation depth at peak load calculated from the initial portion of the unloading curve was over 0.7 and demonstrated the plastic character of tested materials. The indentation hardness and modulus calculated from the slope at the unloading curve were changed due to the presence of plastic deformation from the loading phase, to the load intensity and hold time. The local distribution of carbon nanotubes lead to the variation in creep response and also, in the mechanical properties of material. Calculating the creep rate, a better creep response was offered by the higher concentration of carbon nanotubes during the indentation test at peak load of 1 N. A 3-step standard indentation test (Oliver and Pharr method) was considered to avoid the influence of the duration from the holding phase on the mechanical parameters. We found that a holding phase of 40 seconds was enough to have a negligible influence of creep on the indentation modulus for 5 wt.% of MWCNTs sample. Keywords: indentation, creep, carbon nanotubes, indentation hardness, indentation modulus

Abstract: In order to perform standardized diagnostic and operative techniques the knowledge of the anatomical setup is essential. The main goal of our study was to determine the position of the lumbar dorsal rami of the spinal nerve at the level of the articular process, as well as the position of the surrounding structures. Plastinated slices with 1.5 mm thickness are produced out of five non-pathologic vertebral columns. Subsequently the slices were digitalized and processed anatomically and topographically. The gained data of digitalization offered in the next step the possibility to determine the localization of the spinal nerve and its medial branch as well as to build an anatomical three-dimensional computer model of the region. The plastinated slices produced by E12-technique showed intact and unimpaired anatomical structures and highly transparent tissue. This base was used for the analysis and measurement of structural episodes and for the three-dimensional reconstruction of a lumbar moving segment. The constructed 3D-model displays the morphology of the region in the same quality as the cadaver specimen. Based on our anatomic data, the dorsal ramus of the spinal nerve passes very closely to the neck of the superior articular process at the level of the cranial border of the transverse process. Anatomic characteristics should be kept in mind when denervation techniques of the zygapophyseal joints are performed, thereby reducing the risk of injury to the dorsal ramus. Keywords: plastination, ramus medialis nervus spinalis, E12 technique, radiofrequency facet denervation

Abstract: The paper aims to evaluate the optical and dielectric properties of the nanocomposites based on polystyrene containing various amounts of barium titanate. The characteristics of the thermoplastic polymer are determined using the connectivity indices formalism, while those corresponding to the nanocomposites are evaluated using the parallel and series models. The variation of the optical and dielectric properties with the volume fraction of the nanofiller is discussed. Keywords: polystyrene, nanocomposites, optical properties, dielectric constant

Abstract: The present context of the international studies identifies the electrospinning process as one of the key technologies for obtaing nanofibers. The dynamics of the studies connected to the implementation of this technology is given by the great diversity of the applications of the obtained nanofibers which start from filtering mediums and separating membranes to sensors and actuators, implants, structures for the controlled release of drugs up to the molecular photonics. This paper aims to present a new equipment for obtaining the nanofibers from polymer solutions by means of the electrospinning technology. The suggested equipment accomplishes the computerized control of the electrospinning technological parameters on starting from the idea of modularity and automatic control of the electrospinning process. The equipment allows the real time control for the electrospinning process based on determination of both jet characteristics and the obtained nanofibers properties. Keywords: nanofibers, equipment, technology, modular conception, electrospinning

Abstract: relied on conventional mechanical, anti-infective modalities, followed by a range of regenerative procedures. An innovative medical device, using thermoforming ethylene acetate base, with an electromagnetic applicator, homologated with CE mark in class 2a, was used in the treatment of second degree teeth mobility. The affected areas were exposed to a precise, totally atraumatic and noninvasive electromagnetic field. The preliminary study on 10 subjects was performed with this medical device, using a standard protocol of 30 exposures of 2 h each, on the affected area. Subjects were both male and female, aged between 20-70 years, in healthy state and having a good oral hygiene status. After 2 months, the results were recorded by testing the mobility of the affected teeth, by measuring the periodontal pockets depth and by comparing the radiographs effectuated before and after the treatment. The results were assessed and proved the appreciable reduction of teeth mobility, the reduction of periodontal pockets depth and bone regeneration in the regions exposed to the electromagnetic applicator. The conclusions of this preliminary study recommend this innovative medical device for the use in the healing of periodontal lesions as noninvasive and atraumatic therapy. Keywords: periodontal lesions, innovative medical device, healing

Abstract: Alternative research techniques are essential in order to prove the efficacy of graphene dental materials and their viability, especially if we associate them with other materials studied so far. It is important to determine the effects of these techniques because they can demonstrate the viability and credibility of the research on its properties. The purpose of this study was to measure and analyze the mechanical properties of several composite materials with/without graphene and commercial composite Herculite, designed for dental composites restorations. The materials were composed of a visible light-curing monomer mixture (Bis-GMA+TEGDMA) as a matrix and hydroxyapatite with graphene, bioglasses, colloidal silica as a reinforcing filler. Ten specimens of different composites were prepared for each mechanical test: flexural strength, Young’s modulus, diametral tensile strength, and compressive strength test (Lloyd Instruments- LR5k Plus). Mean values and standard deviations were calculated and ANOVA and Student Newman Keuls multiple comparison tests were applied (P[ 0.05). The addition of 5-10 wt% of hydroxyapatite with graphene nanoparticles to the unfilled monomer mixtures led to the increase of both Young’s modulus, surface hardness of the material, and the flexural strength. Hydroxyapatite with graphene has been used as reinforcing nanofiller in polymeric materials, having potential applications for restorative composites. Keywords: graphene, hydroxyapatite, dental composites restoration, mechanical properties

Abstract: Rubber is widely used in railway infrastructure and in rolling stock. Rubber pads are used in fastening systems of rail to sleepers and rubber elements are used in the primary suspension of Romanian (and foreign) electric locomotives, in freight and passengers railway cars, metro trains and trams; the trams wheels are built with rubber insertion in order to reduce the vehicle unsprung mass. Also, rubber elastic elements are used in railway vehicles buffers. From these examples it can be seen that the rubber elements are used in the construction of parts which are directly contributing to traffic safety. Keywords: rubber, railway car, suspension, railway safety

Abstract: This paper is the first note on experimental protocol development regarding the use of Iosipescu test specimens with acrylic fibre insertion or without the insertion, with metal or textile fibres in a series of tests in which the structural and constructive characteristics of matrix biomaterials are optimised for removable prosthetic restoration. Tensile and shear tests allowed the determination of specimen consolidation with aluminium plates of clamping jaw heads. Based on the theoretical protocol, the following were determined: shape, size and loading of Iosipescu specimen and deck sizing. The CT-1 silicone adhesive behaviour was evaluated based on experimental data. Poly (methyl methacrylate), denoted as PMMA, was used in the study. PMMA has polyethylene fibre and copper wire mesh inserts. These were individually assembled using this adhesive that was used to fix aluminium plates on the clamping jaw heads. The values obtained for the maximum normal traction stress, smax ranged between 22 and 60 MPa, and the tangential shearing stress tmax, of the adhesive ranged between 2 and 6 MPa, with an average value of 4.75 MPa, both depending on the dimensional characteristics and structural composition of the specimens, thus confirming the role of stratification and inserts in the mechanical strength of the specimens. Stress values of smax and tmax allowed the determination of the dimensions of the surface the specimen clamping jaws are fixed upon, practical aspect influencing the accuracy of the final results. Keywords: Iosipescu test, silicon resin, poly (methyl methacrylate), removable prostheses

Abstract: The goal of this study was to measure and analyze the water sorption and mechanical properties of 5 experimental flowable composites with different filling ratios and two types of initiation systems: self cured and light-cured. The samples were analysed, in order to observe the influence of initiation type and the amount of filler on the properties required to satisfy the conditions for dentistry use. We have determined the water sorption and mechanical properties (compressive strength, flexural strength, diametral tensile strength) according to ISO 4049/2000 and international norms “American Dental Association’s Specification No.27. The measurements were done using a mechanical testing machine Lloyd Instruments-LR5k Plus. Increased water absorption weakens the bonds in the polymer matrix, causing separation of filler by the polymer matrix, filler hydrolytically degrade, leading ultimately to reducing the mechanical resistance, which represents a major step in the characterization of dental materials to be used in dentistry. Among all the mechanical stress from oral cavity, the compression and the tension are the predominant forces, during which are developing the highest forces that dental hard tissues are subject to. The results of this study highlight the relationship between the composition, initiation system of the dental materials and their properties. Keywords: flowable dental composites, water sorption, compressive strength, flexural stiffness, tensile strength

Abstract: IOL opacification is a growing issue reported lately in the speciality literature. [1-5] This article follows a series of retrospective cases regarding hydrophobic IOLs that were explanted from three different patients. The explants were examined using AFM and SEM (with EDS), in order to find more details about the surface morphology and the composition of the deposits. The results indicate that they are composed mainly of calcium and phosphate. The authors suggest that ocular comorbidity and other systemic factors are contributing to this complication. Keywords: IOL opacification, explanted IOL, surface deposits

Abstract: The hepatic portal vein (HPV) is the central element of liver afferent pedicle. The intraparenchymal distribution of HPV determines the liver segmentation. The medial branches (MBs) serving left medial division (LMD) of the liver present the greatest morphological variability. On a total of 125 pieces of liver corrosion casts, one examined the intraparenchymal distribution of portal MBs and the segmentation of LMD. Regarding the intraparenchymal distribution of the branches in the LMD of the liver, we showed three distinct morphological types: Type I (81.6% of cases) where are present several small MBs with oblique downward trajectory; Type II (15.2% of cases) that has two distinct MBs, originating in the distal part of the PHV left branch, with slightly upward trajectory; Type III (3.2% of cases) that has three MBs, originating in the distal part of the PHV left branch, the higher with upward trajectory, the lower with downward trajectory, and the middle branch with variable trajectory and originated from the PHV left branch or in one of the first two MBs. Knowledge of this morphological types of portal MBs is important for clinical and surgical practice. Keywords: corrosion casts; hepatic portal vein; medial branches; variability; morphological typologies

Abstract: The influence of the painting process on a biocompostable waste is studied. Disintegration degree (D %) of a 100% biocompostable plastic made from potato almidon is calculated for both painted and non -painted samples. Solid matrix is also characterized by means of a laboratory scaled composting process following UNE-EN norms [2, 3]. It can be concluded that painting has a negative influence on biocomposting process decreasing 4.48% disintegration degree. Average D% for painted samples is 84.56 %, and 89.04 for non- painted ones. Regarding to solid matrix, dry mass after composting is double (91.12 %) as before process (43.63 %) for painted samples and 91 % and 45.41 % after and before composting for non-painted samples. Volatile solids are reduced 5.17 % after composting for painted samples, and 8.78 % for non-painted. Organic nitrogen is reduced 0.34 % and 0.16% for painted and non-painted samples respectively. The negative effect of painting is mainly due to the barrier effect of the paint that prevents microorganisms from converting organic components of the biopolymer into water, CO2 and compost. Keywords: biodisintegration; composting; painted; bioplastic; waste

Abstract: In order to investigate the pyrolysis characteristics and mechanism of moso bamboo, its pyrolysis behaviour has been investigated by thermo-gravimetric analysis (TGA), which can be described as four steps: dehydration, hemicellulose pyrolysis, pyrolysis of cellulose and lignin, and residue decomposition. The decomposition of hemicellulose, cellulose and lignin are the main contributions for pyrolysis weight loss. Furthermore, the pyrolysis mechanism has been clarified based on pyrolysis kinetics model fitting. Detailedly, the pyrolysis kinetics of hemicellulose agrees with first order chemical reaction, whereas the pyrolysis kinetic equation of cellulose and lignin accords with the 1D-diffusion parabolic curve. And the apparent activation energy of them is 124.62 and 232.64 KJ/mol, respectively. Keywords: Moso bamboo, pyrolysis characteristics, pyrolysis kinetics, thermo-gravimetric analysis

Abstract: The paper presents the results of compressive tests performed on Biomet® orthopedic bone cement currently used in arthroplasty. By direct molding of the cement, cylindrical test specimens were manufactured with cross section diameter of 6 mm and height of 12 mm. The stress–strain curves of all specimens tested exhibited similar linear elastic regime with a local maximum followed by yielding. The average compressive strength of the samples is 91.55 MPa, while the average modulus of elasticity was calculated at 1483 MPa. The obtained results can be used in order to asses the fatigue life-time of this type of bone cement. Keywords: total hip replacement, bone cement, PMMA, compression, elastic modulus, Poisson’s ratio