Search

The aim of this work was to investigate the suitability of electrospinning for biodrug delivery and to develop an electrospinning-based method to produce vaginal drug delivery systems. Lactobacillus acidophilus bacteria were encapsu- lated into nanofibers of three different polymers (polyvinyl alcohol and polyvinylpyrrolidone with two different molar masses). Shelf life of the bacteria could be enhanced by the exclusion of water and by preparing a solid dosage form, which is an advantageous and patient-friendly way of administration. The formulations were stored at -20, 7 and 25°C, respec- tively. Viability testing showed that the nanofibers can provide long term stability for huge amounts of living bacteria if they are kept at (or below) 7°C. Furthermore, all kinds of nanowebs prepared in this work dissolved instantly when they got in contact with water, thus the developed biohybrid nanowebs can provide new potential ways for curing bacterial vagi- nosis.

Upgrading of polypropylene waste was performed by different composite technologies, in order to improve the flame retardancy combined with preserved or improved mechanical properties. The polymer waste of density below 900 kg/m 3 is originated from end-of-life vehicles (ELV) after comminution, density separation and comprehensive analy- sis. Intumescent flame retardant system was used for reducing the flammability; while chopped glass fibre reinforcement was used to compensate the deterioration of mechanical properties caused by flame retardant additives. In mixed composite beside of flame retardants, the reinforcement effect of glass fibre can not be realized; therefore with modification of com- posite structure (but maintaining the composition) a multilayer composite was developed, which contains 65.5% of recy- cled polymer, where the core is reinforced with glass fibre covered by flame retarded shell layers. Enhanced flame retardancy (4 min longer time to escape) was achieved by using this layered composite compared to the mixed composite, thus the time to escape could be extended only with modification of composite structure.

Solvent and melt techniques were used to obtain molecular dispersion of the poorly soluble spironolactone (SPIR) model drug enhancing its dissolution rate. DSC study of the interaction between SPIR and hydroxypropyl-β-cyclodextrin confirmed the need for molecular dispersion if their complexation is required. Solvent-free twin-screw extrusion was suitable for forming inclusion complex significantly below the melting temperature of the SPIR. According to DSC, Raman and XRPD results fine dispersion of both components was achieved in a hydrophilic polymer. The molecules of the active ingredient are separated from each other in the polymer and the lack of the lattice energy causes faster dissolution.

The surface of poly(tetrafluoroethylene) (teflon, PTFE) was treated by saddle field fast atom beam (FAB) source in hydrogen, helium and nitrogen with about 1 kV accelerating voltage, up to an estimated particle fluence of 1017 cm− 2. The untreated and FAB-treated samples were characterised by XPS, Raman microspectroscopy, single pass topographic and multipass wear tests and water contact-angle measurements. According to XPS results, upon FAB-treatment the surface F/C value decreased drastically. Raman microspectroscopic measurements testified to the formation of a carbonised surface layer. The thickness of the graded, amorphous carbon-containing layer determined by in-depth Raman microspectroscopic analysis ranged between 5.5 ± 1 and 10.5 ± 1 μm. In addition to radiation damage, a decisive role of degradation induced by thermal effects and diffusion of reactive particles was suggested. The small scale wear resistance of the hydrogen and nitrogen FAB-treated samples improved in comparison with that of the untreated PTFE. The mean surface roughness increased for the treated samples in the order of N < He < H. Water contact-angle decreased upon FAB-treatment. The effect of increased wettability remained durable for at least three months.

Flame retarded thermoplastic polymer compounds were prepared containing recycled rubber tyres, low density polyethylene, ethylene vinyl acetate copolymer and an intumescent additive system consisting of waste polyurethane foam and ammonium polyphosphate. The effect of the additives on the combustion properties was characterised by Limiting Oxygen Index, UL 94 and mass loss calorimetric measurements. The environmental impact was estimated by determining the gas components of CO2 and CO evolving from the compounds during the burning process using a gas analyser system constructed by coupling an FTIR unit to a mass loss calorimeter. The new material forms a thermoplastic rubber of excel- lent processability making it suitable for application in construction industry.

Flame retardant effect of newly synthesized phosphorus-containing reactive amine, which can be used both as crosslinking agent in epoxy resins and as flame retardant, was explored. The effect of montmorillonite and sepiolite additives on thermal stability and flame retardancy was compared in the epoxy resin matrix. Copyright © 2006 John Wiley & Sons, Ltd.

Interface modifications optimized for fire retardancy require detailed research. Confocal Raman microscopy was used to analyze the degradation locally in the area of the nanotube and clay additives. The double-walled carbon nanotube (DWCNT), containing Co catalyst residue, accelerates the deacetylation process of poly(ethylene-co-vinylacetate) (EVA) considerably, while the montmorillonite (MMT) has no significant influence under static circumstances. The compounding process influences the effect of MMT, which causes partial crosslinking in EVA during the compounding. This mechanochemical reaction is catalyzed by uncovered MMT particles, while organophillized MMT promotes the charring process. Inorganic surface modification with various metal ions has also some stabilizing effect. Spray drying of MMT results in microparticles of increased surface area and improved thermal stability of the EVA system. The lowest rate of flame spreading was achieved using uncoated MMT, while coating with cationic surfactant was most efficient for hindering dripping. The rate of heat release (RHR) of the organically modified and the spray dried MMT was approximately the same. The combined organic-inorganic modified clay moderates both the dripping and the flame spreading in the EVA. Copyright © 2006 John Wiley & Sons, Ltd.

Common consideration and classification of surface and interface phenomena in wide areas of material science are discussed through three examples: basalt fiber reinforced composite; flame retarded polypropylene and polyorganosiloxane nanocomposite. Interface-related characteristics of polymer composites and biomaterials are discussed using uniform principles. A new classification of the interphases is introduced including the compatible, adaptive and smart interfacial layers. In case of basalt fiber reinforced polypropylene reactive interface modification is performed in a new and economic way using reactive surfactants. These additives accomplish the compatibilization of the phases during reactive compounding/processing. The fire retardancy of polypropylene system containing ammonium polyphosphate and clay nanoparticles is enhanced by adaptive polysiloxane interphase. Clay additive provides thermal and pH responsive character to silicone based biomaterial thus it can be applied for forming smart interphases.

The efficiency of ammonium polyphosphate in different biocomposites was compared. For the comparison flame retarded lignocellulosic filler reinforced biocomposites were prepared using polypropylene (PP), polyurethane (PUR) and fully biodegradable starch matrices. The compatibility of wood flake with PP was improved by application of an alkoxy silane based reactive surfactant. The silylation improved not only the compatibility but also the thermal stability of the wood flake according to TG measurements. Raman spectroscopic analysis of the silylated product showed that the improved thermal stability is the result of reduced ratio of the amorphous phase of cellulose. The phosphorus additives in flame retarded PUR biocomposites, comprising waste bio fillers and recycled polyol, proved to be very effective because both the matrix and the filler components participate in mechanism of flame retardancy. Plasticised thermoplastic starch could be flame retarded efficiently by as little as 10% ammonium polyphosphate. After their service life the biocomposites can be utilised as chemical fertilizer.

The deterioration of naturally aged low-density polyethylene (LDPE) film was observed by elongation properties, DSC melting enthalpies and surface geometric characteristics by use of atomic force microscopy (AFM). The decrease of elongation at break under the influence of ageing was in good accordance with the increase of melting enthalpies and both phenomena could be explained by the gradual decrease of molecular mass of the polymer. On the wavy surface with a wavelength range of 10–15 μm, valleys with amplitudes from 160 to 600 nm could be observed by AFM depending on the time of ageing. The increase of deepness of valleys was explained not by the gradual erosion of the degraded surface but by the gradual increase of crystallinity, consequently the gradual shrinking on the surface of the polymer film. The gradual increase of crystallinity in the surface region of the film could be demonstrated by confocal Raman microscopy.

This article deals with the study of the efficiency of different compatibilizing agents in the intumescent polypropylene/polyamide-6/ammonium polyphosphate (PP/PA-6/APP) blend. The migration of additive was first investigated by X-ray photoelectron spectroscopy. The study showed that ethylene–butyl acrylate–maleic anhydride is not efficient in preventing the exudation of APP to the surface. However, ethylene vinyl acetate (EVA) prevented such a phenomenon. Second, the modifications in the blends were analyzed as a function of their compositions. Optical microscopy analysis showed that adding EVA to PP/PA-6/APP promoted a decrease in the size of PA-6 droplets. X-ray diffraction was used to characterize the effect of each component on the PP crystallinity. It was clearly shown that the crystallinity depends on the composition of the blend. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 402–411, 2004

Basalt fibers, similarly to other silicate fibers, can be introduced into both thermoplastic and thermosetting polymer matrices. In this work some basalt fiber reinforced polypropylene composites were investigated. The fiber-matrix adhesion was improved by commercial and non-commercial maleic anhydride derivatives. The latter types, called reactive surfactants, were prepared in laboratory scale and the progress of the syntheses was determined by Raman microscopy. The additives allowed performing reactive interface modification during the compounding process. Due to the interface modification with the additives in low concentration the mechanical properties improved. The boundary layers on the surface of the reinforcing fibers were observed using scanning electron microscopy (SEM).

The Raman microscope is one of the most convenient instruments for analyzing the structural characteristics and changes in the interfacial region of multicomponent systems. This is confirmed by the results obtained in the field of packaging materials, nanocomposites, and basalt fibre reinforced composites. In the course of this study, the chemical character of the surface and interfacial regions were investigated and, in addition, the local characteristics of the crystallization process of the polymer matrix could be determined.

Polypropylene-based composites were prepared containing non-treated and various treated cotton fibre and wood flakes. A correlation was observed among the fibre treatment and compounding parameters, mechanical and discoloration properties. The structural changes in fibres were demonstrated by Raman spectroscopic and DSC measurements. The possibility for forming cellulose fibre containing flame retardant composites was also investigated. The efficiency of various treatments on compounding, discoloration and mechanical properties enhance in the following order: no treatment < non ionic surfactant < reactive silicone segment containing non ionic surfactant < special silylation treatment. The best results obtained with the special silylation treatment were explained with the more organophilic character and by the thermal stability of the treated fibres. Cellulose fibre as a polyol-charring component and ammonium-polyphosphate together constitute a high performance intumescent flame retardant system in the PP matrix.

Addition of Ammonium Polyphosphate/Polyamide-6 system is known to provide flame retardancy in many polymers blends via an intumescent process. Particulate fillers (talc and calcium carbonate) are used in large quantities in PP. Combination of fillers in PP can modify the properties of the polymeric matrix. This study investigates the effect of fillers (talc and calcium carbonate) on the fire performance of the Polypropylene/Ammonium polyphosphate/Polyamide-6 blend. It is shown that the fire performance strongly depends on the nature of the filler used. Talc increases and calcium carbonate decreases in the fire performance of the blend.

The effects of fillers (talc and calcium carbonate) were investigated on polypropylene /ammonium polyphosphate/polyamide-6 (PP/APP/PA-6) intumescent system by using mechanical testing, LOI method, cone calorimetry and thermoanalytical techniques. Calcium carbonate and talc affect the fire protective properties of PP/APP/PA-6 system in different ways. It is shown that talc induces an increase in the Young's modulus and a decrease in the elongation at break. Calcium carbonate leads to a decrease in the elongation at break, but there is no improvement in the Young's modulus. Talc increases fire protective performance due to forming a ceramic like protective shield at the surface, whereas calcium carbonate decreases it because of a reaction with APP. Effects of talc and calcium carbonate were furthermore investigated on PP/APP/PA-6 system by measuring Rate of Heat Release (RHR), Total Heat Emitted (THE), CO/CO 2 evolution and residual mass. Results are interpreted by means of decomposition, chemical reaction between components and formation of a protective shield at the surface at ignition.

Monophosphorylated hydroxy phenols were synthesized in a selective way and incorporated in different percentages into epoxy resins as reactive flame retardants. The LOI values of the epoxy resin samples could be increased this way up to 28%. The DSC results show that by increasing the percentage of incorporated monophosphorylated hydroquinone (HMP), the exothermic effect of the curing is decreased, which implies lower network density. An optimum balance is necessary between the flame retardant effect, determined by percentage of HMP, and the lower degree of crosslinking.

Montmorillonite nanoparticles were found to be inefficient in polypropylene because of the lack of a heat insulating char layer and the decomposition of the compatibilising surfactant layer on their surface. Combination with an ammonium polyphosphate-based intumescent system showed some synergism due to modified rheology. The effect of surface and interface modification was analysed using Raman microscopy and X-ray photoelectron spectroscopy. Forming a heat resistant coating layer of low surface energy around the nanoparticles promotes their migration to the surface and formation of a flexible barrier layer, and thus leads to better performance.

Fire retardant (FR) properties, including limiting oxygen index, peak rate of heat release and smoke parameter have been measured and compared for unfilled and filled polyvinyl-chloride (PVC) based cable formulations, containing various amounts of uncoated and zinc-hydroxystannate (ZHS)-coated alumina trihydrate (ATH) and magnesium hydroxide (MH) fillers. Uncoated ATH or MH proved to be efficient FR additives, but when coated with ZHS, further improvements were observed. ATH was more effective than MH in both uncoated and ZHS-coated forms. For a halogen-free ethylene-vinyl acetate (EVA) cable formulation, the content of vinyl acetate and loading of ZHS-coated ATH required to yield optimum FR properties was determined. The interaction between ATH substrate and ZHS coating was also studied by X-ray photoelectron spectroscopy and diffuse reflectance infrared Fourier-transform spectroscopy, using samples with ZHS-contents ranging from 1 to 15 wt%. An increase in the binding energies of the Zn 2p3/2 and Sn 3d5/2 peaks was found, together with alterations in the positions of the (Sn)O—H stretching bands. There was no evidence for condensation and the formation of Al—O—Sn bonds.

The principle of multilayer interphases was proposed earlier for modifying the mechanical properties and UV stability of various multicomponent polymer systems. This paper focuses on the applicability of this principle for improving the performance of intumescent flame-retardant systems using melamine-treated ammonium polyphosphate, silicone modified polyol + ammonium polyphosphate, and silicone modified nanoparticles in polypropylene. The structure–property relationship of the formed systems was studied. A melamine layer of 1.45 nm thickness was formed around ammonium polyphosphate in order to improve the hygrothermal stability, but this layer was not shear-resistant enough. An interphase formed using a special silicone additive is more stable and acts with the intumescent flame-retardant system synergistically. The advantageous interfacial structure is quite complex in this case: polyphosphate particles are surrounded with a macromolecular layer formed from polyol, silicone, and reactive surfactant in order to ensure good stability, efficiency and compatibility. AFM, XPS and a Cone Calorimeter were used for determining the structure and flame-retardancy of these systems. Nanocomposites combined with silicone-containing intumescent system were developed in order to avoid dipping at ignition in the vertical position. SAXS and µ-TA methods were used for determining the structure of this material. Copyright ­© 2003 John Wiley & Sons, Ltd.

Mg(OH)2 and ammonium polyphosphate (APP) based flame retarded polyethylene (PE) and polypropylene (PP) compounds were prepared in a plastograph and the influence of additive systems on the microstructure, mechanical, and melt characteristics of the compounds was investigated by DSC, Raman microscopy, and rheological measurements. A high loading of Mg(OH)2 has a nucleating and crystallinity reducing effect in low density PE. The crystallinity reducing effect was explained by formation of a partially ordered but noncrystallized interfacial region around the flame retardant (FR) particles. The nucleating effect was hindered when the particles were embedded in elastomer. The nucleating effect of APP in PP was also reduced when a polyol layer surrounded it. The incorporation of boroxo siloxane (BSil) elatomer FR synergist, introduced additionally to the above additives, resulted in a further nucleating effect, and increased the melt viscosity. Polymer layered montmorillonite, applied instead of BSil elastomer,...

A model system of intumescent flame retardants, consisting of ammonium polyphosphate and pentaerythritol was prepared and investigated in polypropylene and without the polymer matrix. Thermal scanning oscillation rheometric investigation in the temperature range of 170–500 °C was used to detect the rheological behaviour in the region of melting of the polymer and the plasticity of the char formed at higher temperature. Addition of boroxo siloxane to the model system caused advantageous changes in both regions. Increased complex viscosity and viscoelsasticity of the melt and char respectively contributes to better flame retardancy. According to DTG and FTIR studies the reactions of boroxo siloxane with pentaerythritol and ammonium polyphosphate are the reasons for the rheological changes.

Optimal concentration of boroxo siloxane elastomer synergist was determined by LOI and cone calorimetric measurements on ammonium polyphosphate and pentaerythritol containing intumescent flame retardant for polypropylene. The increased viscosity of the melt and plasticity of intumescent char due to boroxo siloxane elastomer could be proved by a thermal scanning rheometric investigation. It is presumed, the increased melt viscosity is created by the product of boroxo siloxane-pentaerythritol, formed during the compound preparation, while the improved char plasticity is the result of product formed at high temperature from boroxo siloxane and ammonium polyphosphate.

The deterioration of differently stabilised and pigmented high density polyethylene films was investigated by DSC and UV spectroscopy methods in the course of accelerated photo-ageing and compared to earlier XPS and gel-content results. Unexpectedly quick destruction of phthalocyanine containing film was observed and explained by the adsorptive removal of the stabiliser from the polymer matrix. In the pigment (filler)-solvent-stabiliser model systems the high susceptibility of hindered phenol type heat-stabiliser to adsorb on talc and phthalocyanine pigment was proved by UV spectroscopic measurements. Surface coating of the talc and pigment with a reactive surfactant considerable reduced the adsorption capacity and thus improved the photo-stability of the pigmented film.

Pentaerythritol may react with tetraethoxy-silane and ammonium-polyphosphate in flame retarded polyolefins and an interfacial layer can be formed around the ammonium-polyphosphate particles. It is advantageous to study such systems using methods of thermal and surface analysis together.

Increased strength, adsorption capacity and improved resistance against a flame of split film polypropylene fibers could be achieved by applying particulate additives with modified interphases. In the presence of an elastomer interlayer a high drawing ratio could be achieved. A reactive surfactant additive was more appropriate for increasing the tensile strength of filled fibers, while oil adsorbent fibers required fillers covered with non-reactive surfactants for improving the adsorption capacity. Model experiments using XPS and DSC methods and SEM analysis were applied for studying the cause of these effects. The migration of flame retardant additives to the surface of PP fibers could be followed using the XPS method. This advantageous effect can be promoted by silicone interphase.

Nanocomposite structure of polymer intercalated montmorillonites was formed in ethylene vinyl acetate copolymer/magnesium hydroxide flame retarded polymer system. Generally the presence of magnesium hydroxide flame retardant particles disturbs the structural analysis of such systems. Raman microscopic method was successfully applied for evaluating the distribution of components in presence of high concentration of flame retardant additives. The interphase formed around the nanoparticles influences the structure and the temperature dependency of the rheological characteristics, which was evaluated by thermal Scanning Rheometer. Surprisingly the combination of unmodified and modified montmorillonites provided the most advantageous rheology profile for improving the fire retardancy (reducing dripping and increasing the char-stability).

Engineering application of polypropylene requires the employment of flame retardants. Reactive compounding of ammonium-polyphosphate and synergist additives with polypropylene is an effective way for forming flame retardant polypropylene. Both the ammonium-polyphosphate and the additives used for improving its performance effect the crystallization and melting behavior of polypropylene. Encapsulation of flame retardant additives with appropriate elastomer, in order to improve their water resistancy, causes further changes in degree of crystallinity and consequently in the mechanical properties.

Interfacial structure plays an important role in the performance of polypropylene composites. Transcrystalline interfacial layer were determined in talc filled polypropylene. The crystallization and melting behaviour of talc and CaCO 3 filled polypropylene could be modified with smaller amount of additives like elastomer and surfactants. Through the effect of these additives the structure of interface and the degree of crystallinity could be controlled in filled polypropylene.

Interfacial structure plays an important role in the performance of polypropylene composites. Transcrystalline interfacial layer were determined in talc filled polypropylene. The crystallization and melting behaviour of talc and CaCC3 filled polypropylene could be modified with smaller amount of additives like elastomer and surfactants. Through the effect of these additives the structure of interface and the degree of crystallinity could be controlled in filled polypropylene.

Different levels of fibre technologies and application, from synthesis to degradation has been studied using the methods of thermal analysis. Recent results of these studies on synthetic and natural fibres are summarized. The effect of chemical and physical modification of polyolefin fibres as well as the synthesis of polymer emulsion used as additive in fibre technologies could be followed by DSC, DMA, TG methods.

Various flame retardant, recycled ground rubber containing compounds were prepared in a polyethylene-ethylene vinyl acetate blend matrix with the help of a reactive surfactant. The beneficial effect of ground rubber was demonstrated on the flame retardancy, noise damping, and environmental impact of the compounds.

The rapidly growing polymer market increases the risk of fire. The competition for reducing the costs and the activities for increasing the recyclability are advantageous from many aspects but promote the use of cheap and flammable polymers. The relative amount of the types of fire retardants (FRs) used in polymers is changing. The halogen containing compounds initiate corrosion, furthermore, some of them proved to be harmful to the environment and human health. Therefore the new European regulations promote the substitution of some conventional flame retardants by environmental-friendly ones. Reactive processing methods bond the additives to the polymer chains thus provide solution against their release to the environment, which is critical especially for some potential pseudohormones. Beyond the increasing importance of reactive methods the nano-concept is the most widely investigated novel approach to fire retardancy. Promising is the low environmental impact of nanofillers and influence on the macromolecular arrangement owing to their high surface area (reducing the heat distortion and melt dripping at high temperature). However, their fire retardancy performance should be enhanced, which requires better understanding of the mechanism of their action. It has to be clarified what is the relative role of their catalytic and physical action. The importance of the geometric dimensions, quality of dispersion and the potential synergism between different types should be clarified as well. Furthermore, the undesirable by-effect of removing stabilizers from the polymer matrix through their high surface area has to be eliminated. Most recent concepts are the in situ formation of nanofillers (during extrusion of the polymers) and of FR-active interfaces or surfaces around inclusions. Advancement of these concepts require the development of new micro-scale fire modeling/testing methods. Based on the described research activities increasing use of reactive, halogen free solutions in combination with nanofillers of well designed interfaces are predicted. Economic approaches applying recycled polymer matrices, nanofillers and multifunctional additives will increase in the close future. A multifunctional flame retardant can be applied for example as adaptive interlayer in a multiphase systems facilitating good mechanical, transport or adhesive performance at ambient temperature and transforming to protective (heat and combustiblegas barrier) layer at the temperature of combustion.

Modified interfacial layers were studied in polypropylene—calcium carbonate systems compounded in a single-step process with a surface-active agent and an elastomer simultaneously. Samples with etched and non-etched surfaces were investigated by dielectric spectroscopy and scanning electron microscopy. An increase in the thickness of the interfacial layer was brought about by the increasing elastomer content of the system. However, when the concentration of the latter exceeded a critical upper limit, a new disperse elastomer phase could be observed in the matrix. The value of the critical concentration depends upon the type of elastomer and it is a characteristic parameter for a given polymer—elastomer system. Deformations and failure in the composite system are determined by the interfacial layer. A thick elastomer interphase around the filler particles acts as a bumper layer and stops the crazes. The interactions between the components and the change in the mechanical properties induced by the presence of named additives were also investigated by mechanical spectroscopy.

A mechanistic scheme is suggested for lactam polymerisation initiated by hydrochloric acid on the basis of the general mechanism put forward earlier by Bertalan et al. According to this mechanism during the polymerization conditions are created which can initiate further polymerizations resulting in a characteristic inflection type kinetic curve. Experimental results can be well interpreted qualitatively on the basis of this mechanism, and therefore it can serve as a starting point also for a quantitative kinetic model.

One way to improve the fire performance of polymers is by the development of intumescent systems. The addition of ammonium polyphosphate/polyamide-6 is known to provide flame retardancy in many polymers via an intumescent process. The development of appropriate formulations is limited by their mechanical properties. This study shows that polypropylene based intumescent blends are efficient fire retardant systems and that acceptable mechanical properties can be obtained. It is also shown that adding talc improves the mechanical properties of intumescent polypropylene formulations without decreasing their fire retardancy.