Effect of UV-Irradiation and Ozone Exposure on Thermal and Mechanical Properties of PLA/LDPE Films

The mechanical properties of polymer composites based on polylactide vary significantly over a wide range of values. It has been established that photodegradation of low-density polyethylene – polylactide blends occurs both in the amorphous and in the crystalline phase of the PLA matrix, which leads to deterioration of the mechanical properties of the studied mixtures. Ozonolysis affects the strength parameters of polylactide-polyethylene samples as well as photodegradation. By the differential scanning calorimetry it is determined that the melting point of polylactide decreases by 2-4 °C, the glass transition temperature - by 1-3 °C, while the degree of crystallinity increases by 3-6%. In the process of ozonolysis, the thermophysical characteristics of PLA/LDPE have changed.

POLYMER COMPOSITE MATERIALS BASED ON POLYTETRAFLUOROETHYLENE FILLED WITH MODIFIED MONTMORILLONITE

Актуальность исследования состоит в том, что одними из перспективных конструкционных и функциональных материалов остаются полимерные композиты на основе политетрафторэтилена. Благодаря уникальным базовым свойствам он находит широкое применение во всех отраслях промышленности, прежде всего в качестве антифрикционных материалов для узлов трения. В условиях низких температур композиты на основе ПТФЭ являются наиболее перспективными триботехническими материалами для сохранения работоспособности техники и оборудования Севера и арктических регионов. Недостатком ПТФЭ являются низкая износостойкость, хладотекучесть, высокий коэффициент термического расширения, которые можно улучшить добавлением наполнителей.Целью работы является исследование влияния монтмориллонита марки Метамона®1Н1 на свойства и структуру политетрафторэтилена (ПТФЭ).В качестве полимерной матрицы использован политетрафторэтилен марки ПТФЭ марки ПН-90, ООО «Галополимер»,г. Пермь.В качестве наполнителя использован Монтмориллонит марки МЕТАМОН® 1Н1 – гидрофильная глина, представляющая очищенный природный Na+ - монтмориллонит.Введение активированного метамона в композиты позволяет повысить деформационно-прочностные характеристики ПКМ по сравнению с исходным ПТФЭ.В данной работе представлены результаты исследований влияния органомодифицированного механоактивированного монтмориллонита (оММТ) марки 101/102 на физико-механические характеристики и структуру политетрафторэтилена. Содержание наполнителя варьировали от 0,5 до 7 мас. %. Установлено, что при введении 0,1-5,0 мас. % оММТ в ПТФЭ прочность ПКМ увеличивается на 25 %, относительное удлинение на 21%. Структурными исследованиями зарегистрирована трансформация надмолекулярной структуры ПТФЭ с формированием сферолитоподобных образований, центрами кристаллизации которых являются частицы оММТ. Для этих концентраций наполнителя установлены более высокие показатели энтальпии плавления и степени кристалличности методом дифференциальной сканирующей калориметрии. The development of modern technology requires the search for new structural materials that surpass traditional ones in their deformation-strength, elastic and wear-resistant properties. Composite materials based on PTFE are very promising structural materials for many industries.PTFE is widely used in friction units of technical systems due to its operability in a wide temperature range while maintaining low and stable values of the coefficient of friction, as well as its ability to provide self-lubrication during friction. Such disadvantages of PTFE as cold flow, low wear resistance, high coefficient of thermal expansion are eliminated by modification, one of the common methods of which is filling.The paper focuses on the effect of organomodified mechanically activated montmorillonite (OMMT) of 101/102 grade on the physical and mechanical characteristics and structure of polytetrafluoroethylene. The filler content varied from 0.5 to 7 wt. %. With the introduction of 0.1-5.0 wt. % OMMT in PTFE, the strength of PCM increases by 35%, and the elongation by 21% was found. Structural studies have registered the transformation of the supramolecular structure of PTFE with the formation of spherulite-like formations, the centers of crystallization of which are particles of OMMT. For these filler concentrations, higher values ​​of the enthalpy of melting and the degree of crystallinity were established by the method of differential scanning calorimetry.

β-Cyclodextrin Inclusion Complexes of Budesonide with Enhanced Bioavailability for COPD Treatment

Chronic obstructive pulmonary disease (COPD) is a life-threatening disease of the respiratory system, affecting many patients worldwide. Budesonide (BUD), a synthetic glucocorticosteroid applied for the treatment of COPD patients, is a hydrophobic compound with low bioavailability. The formation of inclusion complexes of hydrophobic compounds with β-cyclodextrin (CD) through the solvent evaporation technique is an appealing method for the amelioration of the compounds’ in vitro release behavior. In the present study, CD–BUD complexes were prepared through the solvent evaporation technique. The effect of the applied solvent was evaluated through FTIR, scanning electron microscopy (SEM), X-ray diffraction (XRD) analysis, and in vitro release behavior measurements. It was found that the optimum complexes with the minimum degree of crystallinity and the optimum in vitro release behavior are prepared in the solvent ratio H2O/EtOH 80/20 v/v. In a further step, the formation of CD–BUD complexes containing different amounts of BUD was prepared. Through XRD measurements, the degree of crystallinity of the samples was calculated confirming the diminished crystallinity of BUD in CD complexes. The in vitro release of the samples showed the improved release behavior of BUD from the complexes in comparison to neat BUD while a direct correlation between the degree of crystallinity and in vitro release behavior was demonstrated.

Determination of the Degree of Crystallinity of Poly(2-methyl-2-oxazoline)

A new method for purification of 2-methyl-2-oxazoline using citric acid was developed and living cationic ring-opening polymerization of 2-methyl-2-oxazoline was carried out. Polymerization was conducted in acetonitrile using benzyl chloride—boron trifluoride etherate initiating system. According to DSC data, the temperature range of melting of the crystalline phase of the resulting polymer was 95–180 °C. According to small-angle X-ray scattering and wide-angle X-ray diffraction data, the degree of crystallinity of the polymer was 12%. Upon cooling of the polymer melt, the polymer became amorphous. Using thermogravimetric analysis, it was found that the thermal destruction of poly(2-methyl-2-oxazoline) started above 209 °C.

Comparative Study of Crystallization, Mechanical Properties, and In Vitro Cytotoxicity of Nanocomposites at Low Filler Loadings of Hydroxyapatite for Bone-Tissue Engineering Based on Poly(l-lactic acid)/Cyclo Olefin Copolymer

A poly(l-lactic acid)/nanohydroxyapatite (PLLA/nHA) scaffold works as a bioactive, osteoconductive scaffold for bone-tissue engineering, but its low degradation rate limits embedded HA in PLLA to efficiently interact with body fluids. In this work, nano-hydroxyapatite (nHA) was added in lower filler loadings (1, 5, 10, and 20 wt%) in a poly(l-lactic acid)/cyclo olefin copolymer10 wt% (PLLA/COC10) blend to obtain novel poly(l-lactic acid)/cyclo olefin copolymer/nanohydroxyapatite (PLLA/COC10-nHA) scaffolds for bone-tissue regeneration and repair. Furthermore, the structure-activity relationship of PLLA/COC10-nHA (ternary system) nanocomposites in comparison with PLLA/nHA (binary system) nanocomposites was systematically studied. Nanocomposites were evaluated for structural (morphology, crystallization), thermomechanical properties, antibacterial potential, and cytocompatibility for bone-tissue engineering applications. Scanning electron microscope images revealed that PLLA/COC10-nHA had uniform morphology and dispersion of nanoparticles up to 10% of HA, and the overall nHA dispersion in matrix was better in PLLA/COC10-nHA as compared to PLLA/nHA. Fourier transformation infrared spectroscopy (FTIR), powder X-ray diffraction (XRD), and differential scanning calorimetry (DSC) studies confirmed miscibility and transformation of the α-crystal form of PLLA to the ά-crystal form by the addition of nHA in all nanocomposites. The degree of crystallinity (%) in the case of PLLA/COC10-nHA 10 wt% was 114% higher than pure PLLA/COC10 and 128% higher than pristine PLLA, indicating COC and nHA are acting as nucleating agents in the PLLA/COC10-nHA nanocomposites, causing an increase in the degree of crystallinity (%). Moreover, PLLA/COC10-nHA exhibited 140 to 240% (1–20 wt% HA) enhanced mechanical properties in terms of ductility as compared to PLLA/nHA. Antibacterial activity results showed that 10 wt% HA in PLLA/COC10-nHA showed substantial activity against P. aeruginosa, S. aureus, and L. monocytogenes. In vitro cytocompatibility of PLLA/COC10 and PLLA nanocomposites with nHA osteoprogenitor cells (MC3T3-E1) and bone mesenchymal stem cells (BMSC) was evaluated. Both cell lines showed two- to three-fold enhancement in cell viability and 10- to 30-fold in proliferation upon culture on PLLA/COC10-nHA as compared to PLLA/nHA composites. It was observed that the ternary system PLLA/COC10-nHA had good dispersion and interfacial interaction resulting in improved thermomechanical and enhanced osteoconductive properties as compared to PLLA/nHA.

Study of particles of plasma dynamic synthesis product in the Ti-O system by high-resolution transmission electron microscopy

The paper demonstrates the possibility of obtaining a dispersed product in the Ti-O system by the method of plasma dynamic synthesis. It was revealed that the product consists of two modifications of TiO2: anatase and rutile. The degree of crystallinity is at a level of ~ 98.0%, which indicates the practical absence of an amorphous component. The predominant phase is anatase, which is confirmed by the results of quantitative X-ray phase analysis and high-resolution transmission electron microscopy.

Differential scanning calorimetry/small-angle X-ray scattering analysis of ultraviolet sensible polypropylene filaments

In this work, ultraviolet (UV) sensible metallocene isotactic polypropylene (miPP) filaments were produced with different drawing ratios and various concentrations of photochromic pigment. The effects of pigment concentration and drawing ratio on the chromatic properties and the structural modification for the miPP filaments were studied extensively by differential scanning calorimetry (DSC) and small- and wide-angle X-ray scattering (SAXS/WAXS) measurements. The change in melting temperature and the polymeric structures, such as lamellar thickness, long period and degree of crystallinity of miPP with the addition of a UV sensible pigment into miPP and the drawing process, were evaluated. The results show that the pigment concentration and the drawing ratio influence the inner structure of miPP filaments. Finally, our investigation shows that SAXS and also WAXS are appropriate to determine the lamellar thickness and the degree of crystallinity established by the DSC approach. This work attempts to correlate the results of lamellar thickness, the degree of crystallinity and the higher-order structure of the polymer acquired by DSC as well as X-ray diffraction (XRD) techniques in order to develop an appropriate approach to find the influence of pigment concentration and drawing ratio on miPP filaments.

Selectively Etched Halloysite Nanotubes as Performance Booster of Epoxidized Natural Rubber Composites

Halloysite Nanotubes (HNT) are chemically similar to clay, which makes them incompatible with non-polar rubbers such as natural rubber (NR). Modification of NR into a polar rubber is of interest. In this work, Epoxidized Natural Rubber (ENR) was prepared in order to obtain a composite that could assure filler–matrix compatibility. However, the performance of this composite was still not satisfactory, so an alternative to the basic HNT filler was pursued. The surface area of HNT was further increased by etching with acid; the specific surface increased with treatment time. The FTIR spectra confirmed selective etching on the Al–OH surface of HNT with reduction in peak intensity in the regions 3750–3600 cm−1 and 825–725 cm−1, indicating decrease in Al–OH structures. The use of acid-treated HNT improved modulus, tensile strength, and tear strength of the filled composites. This was attributed to the filler–matrix interactions of acid-treated HNT with ENR. Further evidence was found from the Payne effect being reduced to 44.2% through acid treatment of the filler. As for the strain-induced crystallization (SIC) in the composites, the stress–strain curves correlated well with the degree of crystallinity observed from synchrotron wide-angle X-ray scattering.

THE EFFECT OF CRYSTALLINITY ON THE THERMAL CONDUCTIVITY OF POLYMERS

The aim of this research is investigating the direct effect of crystallinity of thermoplastic polymers on their thermal conductivity values. The study has included many materials, namely: polyoxymethylene (POM), high-density polyethylene (HDPE), low-density polypropylene (LDPE), polypropylene (PP), polyamide (PA) and polyethylene terephthalate (PET). The degrees of crystallinity ranged from high-values (60-70%), mid-values (30-40%) and low-values (10-20%). The work has done theoretically and experimentally. Theoretical work has used mathematical function extracted from reliable empirical relationships. The experimental work has included: manufacturing the specimens; specifying the cooling procedure in order to get the required degree of crystallinity; measuring the coefficient of thermal conductivity for different polymers at various conditions; and finally analyze the data and introduce the experiences obtained from the investigation. In general, theoretical values as well as experimental data were both behave similarly with respect to the variation of thermal conductivity with the degree of crystallinity. The results show that by increasing the degree of crystallinity the thermal conductivity of the polymer has increased by 10-20%.

Effect of the Environment on the Characteristics of a Polymer

The polycarbonate (PC) is a highly valued polymeric material for its various characteristics and low cost. Its transparency and impact resistance justify its use in a severe radiation and temperature environment. The aim of this article is to subject this material to aging under ultraviolet (UV) radiation with a wavelength of 253 nm and a temperature of 80°C for various times. The physicochemical and mechanical characterizations of the virgin and aged material have allowed the revelation of the aging effects on the properties. The Fourier Transform Infrared Spectroscopy (FTIR) technique highlight breaks in chemical bonds in the molecular chains of the PC subjected to the combined effects of UV and heat. X-ray analysis have showed a reduction in crystallites and a tendency towards an amorphous state at short times, but the degree of crystallinity increases again at long exposure times of the material. As a result, the microhardness of the aged material is strongly affected on the exposed surface with less effect depending on the depth.