Effect of particle size on the surface properties and morphology of ground flax

Flax fibers were ground with a ball-mill and four fractions with different size ranges were collected by sieving. These were tested for water sorption, degree of polymerization (DP), copper number, hydroxyl number and analyzed by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and inverse gas chromatography (IGC). Significant differences were found between the properties of the flax fiber and those of the ground versions, including fragmentation of fibers, increase of water sorption, copper number, hydroxyl number and surface O/C ratio, and decrease of DP, crystallite size and dispersive component of surface energy (gammasd). Some parameters depended on the particle size: O/C ratio and hydroxyl number had local maxima at 315-630 μm, while gammasd increased steadily with the decrease of particle size. These relationships were explained by fiber disintegration, destruction of waxy surface layer, exposure of cellulosic components, increase of surface area and crystalline imperfections

Thermoplastic Starch/Wood Composites: Effect of Processing Technology, Interfacial Interactions and Particle Characteristics

hermoplastic starch (TPS)/wood composites in a wide composition range were prepared in an internal mixer followed by compression molding. Three types of lignocellulose fibers were used to study the effect of particle and surface characteristics on the processability as well as the mechanical and water absorption properties of the composites. The mechanical properties of these composites were also compared with those of the composites processed by injection molding in an earlier study, and the effect of processing technology on the mechanical properties was also investigated. The processing of TPS/lignocellulose composites in the internal mixer demanded more energy with increasing amount and aspect ratio of the fibers as a result of a network formation. Only a small variation among the dispersion component of the surface tension of the wood samples was found, and almost no difference in the stiffness and strength of the composites prepared in the internal mixer was observed. The results proved that the influence of the processing method on the stiffness and strength of the composites depends strongly on the aspect ratio of the wood particles. Increasing anisotropy results in increasing difference in the mechanical properties of the composites prepared by different methods. The equilibrium water uptake of the fibers and the composites depended especially on the size and, consequently, on the specific surface area of the wood fibers

EFFECTS OF PREPARATION METHODS ON THE STRUCTURE AND MECHANICAL PROPERTIES OF WET CONDITIONED STARCH/MONTMORILLONITE NANOCOMPOSITE FILMS

TPS/Na-montmorillonite nanocomposite films were prepared by solution and melt blending. Clay content changed between 0 and 25 wt% based on the amount of dry starch. Structure, tensile properties, and water content of wet conditioned films were determined as a function of clay content. Intercalated structure and VH-type crystallinity of starch were found for all the nanocomposites independently of clay and plasticizer content or preparation method, but at larger than 10 wt% clay content nanocomposites prepared by melt intercalation contained aggregated particles as well. In spite of the incomplete exfoliation clay reinforces TPS considerably. Preparation method has a strong influence on mechanical properties of wet conditioned films. Mechanical properties of the conditioned samples prepared by solution homogenization are much better than those of nanocomposites prepared by melt blending. Water, which was either adsorbed or bonded in the composites in conditioning or solution mixing process, respectively, has different effect on mechanical properties

CHEMICAL REACTIONS DURING THE PROCESSING OF STABILIZED PE; DISCOLOURATION AND STABILIZER CONSUMPTION

A series of experiments was carried out to develop an additive package for HDPE blown films. The evaluation of the results yielded interesting correlations relating the colour of the polymer to its chain structure and to the properties of the films. Additional experiments proved that all reactions are related to each other. The discolouration of the polymer could be described by simple first order reaction kinetics and a linear correlation was found between stability and a quantity calculated from the kinetic model. The reaction of the vinyl functionality of the polymer seems to be related to the changes in its rheological properties. In spite of the good general correlations found, some details remained unexplained and need further investigation

CHEMICAL REACTIONS DURING THE PROCESSING OF STABILIZED PE; STRUCTURE/PROPERTY CORRELATIONS

Interesting correlations were observed in an optimization project directed towards the development of a recipe for blown film production. Analysis of the data and additional experiments indicated that some reactions take place during the processing of stabilized PE which also change the structure of the polymer. Modification of the rheological properties of the polymer and the mechanical characteristics of blown films can be related to these chemical processes. A close correlation was found among basically all rheological and mechanical properties. A tentative explanation was given which relates chemistry to the structure of the polymer and the properties of the product. According to the hypothesis long chain branches are formed during processing which decrease MFI, change the orientation of the film in the perpendicular direction and result in a considerable decrease in the strength of the blown films

Az emberi kapcsolatok hatása a szubjektív életminőségre = Subjective Quality of Life and the Effect of Social Network

Az emberi kapcsolatok fokozzák vagy csökkentik a szubjektív életminőséget, az elégedettséget és boldogságot. Az emberek létfeltétele differenciált, ám az objektív feltételek különbözősége ellenére mindenki elégedetten és boldogan akar élni. Az individuális adaptációt azonban nehezítik a makro-társadalmi korlátok, kihívások. A közösségi kapcsolat általános szükséglet, ám a közéletiség igénye csak a minta ötödénél található. Emocionális erőforrásokat, de bánatot is az emberek döntően közvetlen kapcsolataiktól kapnak. Az együtt töltött idő fokozza a szubjektív életminőséget, különösen a magántársaság, de örömforrások a virtuális kötelékek is. A kapcsolatok kompenzációs és adaptációs hatásával alakuló szubjektív életminőségi csoportok szerint a társadalom háromnegyede eddigi életével relatíve elégedett, fele jelenleg relatíve boldog, ötöde nem elégedett és nem is boldog. A kapcsolatok szubjektív életminőségre gyakorolt hatásának 24 európai országot összehasonlító nemzetközi vizsgálata azt jelzi, hogy a társadalom többségének szubjektív életminősége a legkedvezőbb az északi országokban, ahol nincs szélsőséges egyenlőtlenség, erős a bizalom, s integrált a társadalom. A legkedvezőtlenebbnek a poszt-szocialista országok és a relatíve szegény déli országok válaszadói érzik életminőségüket. | The life conditions of people are differentiated, however, all of us want to lead a satisfied and happy life, despite the diversity of objective circumstances. Community relations are generally desired, but only the fifth of the sample is characterised by the need of public life. People primarily receive both emotional resources and sorrow from their direct relations. Time spent together, especially private company, raises subjective well-being; however, virtual relations are also sources of happiness. According to the subjective quality of life groups, created by the compensation and adaptation effects of relationships, three quarters of the society are relatively satisfied with their lives, half of them are relatively happy at present, and one fifth is neither satisfied nor happy. An international comparative survey of twenty-four European countries, that investigated the effect of relationships on subjective quality of life, indicates that the subjective well-being of the majority of society is the most favourable in the Northern countries, where no extreme inequalities exist, trust is strong and society is integrated. Respondents of the post-communist and the relatively poor Southern European countries experience their quality of life to be the most dissatisfactory

Characterization of the surface properties of cellulosic fibers in fibrous and ground forms by IGC and contact angle measurements

Surface properties of fibrous and ground cotton and linen were investigated by inverse gas chromatography (IGC) and the contact angle with different liquids was also measured on fabrics composed of both fibers. Results proved that dispersion component of surface tension (γsd) determined by IGC depends not only on the surface energy, but also on several factors influencing the adsorbability of probe molecules on the cellulosic substrates. For cotton samples, the trapping of n-alkanes among waxy molecules in the outer layer of fibers can be presumed. This effect results in larger γsd for cotton fibers than for linen in spite of the higher wettability of the linen fabrics. Besides the surface energy and trapping effects, the grinding also influences the γsd values. Specific enthalpy of adsorption (ΔHAab) of polar probes could be determined on all linen samples, but only on the ground cotton sample. Lewis acid-base character calculated for linen and ground cotton samples depends on the same effects as the γsd does. The similar ΔHAab values of chloroform (acidic) and THF (basic) measured on each of the samples support the conclusion that the surface character is amphoteric, which is also proved by the high ΔHAab values of the amphoteric ethyl acetate and acetone probes

A keményítő módosítása – A faliszt hatása a termoplasztikus keményítő mechanikai és funkcionális tulajdonságaira.

Jelen cikkünkben a termoplasztikus keményítő (TPS) létrehozásának és módosításának lehetőségeit foglaljuk össze, különös tekintettel a faliszttel erősített kompozitokra. 36 m/m% glicerinnel lágyított keményítő felhasználásával állítottunk elő TPS/faliszt kompozitokat. A komponenseket gyorskeverőben homogenizáltuk, extrudáltuk, majd fröccsöntéssel készítettünk próbatesteket. Meghatároztuk a kompozitok mechanikai jellemzőit, szerkezetét, vízfelvételét és méretváltozását a faliszttartalom függvényében, amelyet 0 és 40 v/v% között változtattunk 7 lépésben. A TPS faliszttel való társítása több szempontból igen előnyös. A merevség és szilárdság nő a töltőanyag-tartalommal, különösen nagy szálhossz esetén. Mindez részben a mátrix gyenge tulajdonságaira, részben pedig az erős szemcse-mátrix adhézióra vezethető vissza. Ez utóbbi a vártnál is nagyobb csökkenést eredményez a kompozitok vízfelvételében, ezzel együtt a víztartalom még 40 v/v% faliszttartalomnál is jelentős marad. A fröccsöntött TPS próbatestek zsugorodása rendkívül nagymértékű, és a méretváltozás igen hosszú idő alatt játszódik le. Mindez már 15-20 v/v% töltőanyag hozzáadásával kiküszöbölhető, a faliszt tehát eredményesen javítja a kompozitok mérettartósságát

HIPS/zeolite hybrid composites as active packaging materials: Structure and functional properties

Desiccant composites were prepared from seven high impact polystyrene copolymers (HIPS) with different butadiene content and dispersed droplet size to study the effect of structure on their functional and application properties. A 4A type zeolite was used as desiccant. The thermodynamic analysis of structure development revealed that the embedding of the zeolite into the polybutadiene droplets is the thermodynamically favored process. Comparison of composite stiffness to theoretically predicted values indicated that considerable embedding occurs during composite preparation. The extent of embedding depends on zeolite content, but also on other factors like butadiene content and the droplet size of the elastomer. Composite stiffness and strength decreases with increasing extent of embedding, while functional properties are dominated by zeolite content. The initial rate of water adsorption increases, while overall rate decreases with increasing desiccant loading. Embedding influences only the initial rate of water adsorption which decreases slightly with increasing extent of encapsulation

Desiccant effect of starch in polylactic acid composites

Polylactic acid (PLA)/starch and PLA/starch-glycerol composites with different glycerol contents were prepared in a wide composition range, in order to study their applicability as packaging materials for dry products. Water uptake was determined at a temperature of 23 °C and different relative humidities. Structure and mechanical properties were also investigated. PLA/ unplasticized starch composites could absorb a considerable amount of water. As a result, they may be adequate as a biodegradable inner container in dry packaging. The absorption capacity of the composites increased significantly with increasing starch content and relative humidity, respectively. Unplasticized starch exhibited not only a desiccant but also a reinforcing effect in PLA, thus both stiffness and strength increased with increasing starch loading. The influence of glycerol content on the water uptake was difficult to reveal due to the migration of glycerol from the bulk to the surface. Furthermore, glycerol weakened the PLA/starch adhesion and softened starch particles