Characterization of polyethylene terephthalate/polyaniline blends as potential antioxidant materials

Polyethylene terephthalate (PET) blends with a nanorod form of polyaniline (NR-PANI), formed by a falling pH synthesis, were prepared by dispersion in a melt of PET at 265 °C. Blends with 1, 2 and 3 wt% NR-PANI loading were prepared. Optical microscopy revealed an even distribution of NR-PANI particles within the PET matrix. The blends were characterized using FTIR, XPS, DSC and DMTA. Melt flow index values suggested hydrolysis of PET chains to lower molecular weight units when NR-PANI was blended. Some PET hydrolysis was also evident from the increasing oxygen to carbon ratios with an increased NR-PANI content in the blends. While the PET glass transition temperature remained relatively unaffected, the degree of PET crystallinity was increased with the addition of NR-PANI. The electrical conductivity as well as the free radical scavenging capacity of PET increased with greater NR-PANI loading in the matrix. The mechanical properties of PET, however, declined with NR-PANI loading suggesting a lack of adequate interfacial adhesion between the NR-PANI particles and the PET matrix.     

Dispersed phase morphology and fractionated crystallization of high-density polyethylene in PET/HDPE blends

The fractionated crystallization of high density polyethylene dispersed in a poly(ethylene terephthalate) matrix at composition of 15 wt-% was studied. The effect of the molecular weight of polyethylene with and without compatibilization was particularly addressed regarding its influence on the morphology of the blends. For non-compatibilized blends, the dramatic influence of the molecular weight of the polyethylene on the viscosity ratio and therefore on the dispersion is reflected on the relative intensities of the twin crystallization peaks of polyethylene that are developed upon cooling. These peaks reflect two sets of particles that are nucleated by more or less active heterogeneities. The influence of the addition of an ethylene-glycidyl methacrylate copolymer on the morphology and on the crystallization of the blends was also investigated. For a high molecular weight polyethylene, the compatibilizer shows less efficiency as far as dispersion is concerned.     

The effect of metallocene-catalyzed linear low-density polyethylene on the physicomechanical properties of its film blends with low-density polyethylene

Films comprising a metallocene-catalyzed linear low-density polyethylene (mLLDPE) blended with either of two different low-density polyethylene (LDPE) materials were prepared. The physicomechanical, optical and melt flow properties of the films were measured. A novel adaptation of conventional radar plots was used to process the acquired data to identify the level at which mLLDPE should be incorporated in either of the LDPEs to produce optimal overall properties. In general, the addition of mLLDPE to LDPE improved most of the properties considered and the LDPE material having the higher polydispersity produced blends having superior properties. A level of mLLDPE of between 20–30% (w/w) was required in order to achieve optimization.     

Influence of a fine talc on the properties of composites with high density polyethylene and polyethylene/polystyrene blends

Fine talc filled high density polyethylene (HDPE) and HDPE/polystyrene (PS) blends were extruded, injection moulded and characterized. Some of the mechanical properties of the talc filled HDPE and talc filled 75/25 HDPE/PS blend were deduced from stress–strain measurements. A comparison between the effect of the talc on the properties of the filled HDPE and filled 75/25 HDPE/PS blend showed that the mineral filler had the same effect on both systems provided that its array in the organic matrix is almost the same in both cases. In fact, the rheological results proved that the dispersion of talc in the HDPE matrix was not really affected by the presence of PS. The study particularly focused on the effect of talc on the ultimate tensile strength of the filled HDPE and that of the filled blend. It has been noted that the brittle nature of PS neutralizes, to a certain extent, the degrading effect of talc on this property. Furthermore, both PS and talc have a complementary effect on the stiffness and the resilience of HDPE/PS/talc blend composites.     

Mechanical and thermal properties of compatibilized composites of polyethylene and esterified lignin

Lignin have been esterified using phthalic anhydride and then blended with (up to 40 wt.%) low density polyethylene (LDPE). Maleic anhydride grafted LDPE has been added as compatibilizer. The mechanical and thermal properties of the blends were measured according to ASTM standards and compared with those of neat LDPE. The results reveal that addition of compatibilizer improved the mechanical properties significantly approaching values close to those of neat LDPE. The scanning electron micrographs of the blend specimens also support the above observations. Thermogravimetric analysis showed greater thermal stability for the compatibilized blends. The char content has been found to increase with increasing filler (lignin phthalate) content. DSC analysis revealed that the crystallinity values of the blends slightly increase by the addition of filler (lignin phthalate).     

Morphology and antibacterial properties of plasticized chitosan/metallocene polyethylene blends

In this work, plasticized chitosan-based materials were produced through a molten process. A thermo-mechanical treatment was used to achieve chitosan plasticization in the presence of water, acetic acid, and glycerol. Water and glycerol acted as plasticizers, while acetic acid was used as a solvent and plasticizer for chitosan. The influence of acetic acid total content, chitosan/acetic acid solution ratio, and chitosan/glycerol ratio were examined in this study. The various plasticized compounds were blended with a metallocene polyethylene (mPE) and the morphology, rheological, and antibacterial properties of this novel blend system were examined. It was found that an increase in acetic acid content allowed better chitosan dissolution, while a higher glycerol concentration resulted in improved dispersion of the plasticized chitosan phase in the mPE. Following thermo-mechanical treatment, blends presented good antibacterial properties with a reduction of the number of bacteria (non-pathogenic Escherichia coli) by 2 log(CFU/mL) for the chitosan-containing systems with respect to neat mPE. Mechanical properties of the mPE/plasticized chitosan blends were improved by compatibilization with ethylene vinyl acetate, while antibacterial properties were not affected.     

Kraft lignin and silica as precursors of advanced composite materials and electroactive blends

In this study, advanced multifunctional silica/lignin composite materials have been prepared. The main focus of this study includes the chemical modification of Kraft lignin, and its interaction with silica matrix, thereby providing the possibility of applying the obtained systems in a number of areas, including electrochemistry. Analysis of dispersive–morphological properties revealed that the samples containing 10–20 parts by weight of lignin had the best parameters. The elemental analysis of the final composites, thus, obtained indicated an increase in the contents of carbon, hydrogen and sulphur with increasing quantity of lignin used. Spectrophotometric evaluation of the products obtained, proves the successful synthesis of silica/lignin composites which is manifested by the presence of characteristic bands of appropriate functional groups. The increasing intensity of these bands with increasing content of lignin in the silica matrix conforms entirely with the expectations. Thus, obtained composite powders were blended with multiwalled carbon nanotubes at the mass ratio of 1:2 with the aid of ultrasound. The blends were cast-deposited on glassy carbon electrode and the electrochemical activity was assessed by cyclic voltammetry. It revealed the presence of a redox system assigned to lignin-derived quinone/hydroquinone couple.     

An investigation of the potential of ethylene vinyl acetate/polyethylene blends for use in recyclable high voltage cable insulation systems

Ethylene vinyl acetate (EVA) co-polymers can potentially provide novel materials for inclusion into extruded high voltage cable systems, providing a degree of electrical conductivity whilst avoiding the dispersion problems associated with conventional particulate fillers or conducting polymers. Although a degree of conductivity can decrease the electrical breakdown performance, it can help to suppress the development of space charge and increase the tree initiation voltage leading to enhanced dielectric properties. In addition, novel two phase morphologies can be formulated leading to the ability to control key thermal and mechanical properties and the ability to tailor these to suit the application. In addition, one of the problems with conventional cross-linked polyethylene (XLPE) is that it cannot easily be recycled; therefore, in this time of increasing environmental awareness, it is prudent to begin investigations into alternative recyclable materials to replace XLPE in extruded cables for the medium to long term. The current article focuses on the crystallisation behaviour, morphology, mechanical and dielectric properties of a range of polymeric insulation systems based on an EVA co-polymer together with a high density polyethylene (HDPE) component. The morphology was controlled by choosing co-polymers containing different vinyl acetate contents together with appropriate crystallisation routes. The relationships between the morphology and the mechanical and dielectric properties were explored. Blends containing a low vinyl acetate content co-polymer combined with HDPE have significant potential to replace XLPE in cable systems and have the advantage of being easily recycled at the end of their service life.     

On the use of nanoscale indentation with the AFM in the identification of phases in blends of linear low density polyethylene and high density polyethylene

The microstructures generated by blends of linear low density polyethylene (LLDPE) and high density polyethylene (HDPE) following isothermal crystallization from the melt have been studied using several techniques. The traditional methods of electron microscopy, wide angle X-ray scattering, and differential scanning calorimetry were used to examine the superstructures, lattice spacings, and thermal properties, respectively. In addition, nanoindentation of specific moieties within the microstructure was performed using the atomic force microscope (AFM). The indentation measurements were used to generate values for the relative elastic moduli of the crystalline features and to identify phases within the superstructures. The AFM results were compared to results obtained from the aforementioned techniques and to microhardness measurements.     

聚乙烯/废天然橡胶的老化和力学性能研究

通过汞灯辐射试验对制备的聚乙烯/废天然橡胶共混物进行了紫外老化试验,研究了防老剂4010对聚乙烯/废天然橡胶的紫外老化性能的影响。结果表明:老化初期聚乙烯/废天然橡胶(60/40)的拉伸强度提高,老化中后期聚乙烯/废天然橡胶拉伸强度下降。防老剂4010的加入提高了聚乙烯/废天然橡胶的紫外老化性能。     

An investigation of the potential of polypropylene and its blends for use in recyclable high voltage cable insulation systems

Most modern extruded high voltage cables employ cross-linked polyethylene (XLPE) as the insulation material. XLPE has excellent thermo-mechanical properties, is relatively cheap and has a low dielectric loss, which make it an ideal material for this application. Unfortunately, XLPE is not easily recycled at the end of its lifetime leading to questions concerning its long-term sustainability. A previous investigation in this series considered the potential of a range of ethylene-based systems to provide suitable recyclable alternatives to XLPE. Whilst blending could allow systems having similar thermo-mechanical and electrical properties to XLPE to be designed, it was not possible to obtain better performance than XLPE using these systems. Polypropylene offers, potentially, a route to improved insulation systems by virtue of its higher melting point and excellent dielectric properties. However, traditional isotactic polypropylenes have always had the problem of being too brittle for inclusion into practical cable designs. Recently a broad range of propylene co-polymers having improved ductility have become available, which may prove more suitable. The current study compares traditional isotactic and syndiotactic polypropylenes to a range of commercially available propylene co-polymers and focuses on their morphology, thermal, thermo-mechanical and electrical properties. These parameters were then taken together to identify the most suitable candidate materials for future cable applications. The use of blending as a means to further optimise the various material properties was also explored.     

Microstructure and properties of polyester/urethane acrylate thermosetting blends,and their use as composite matrices

Thermosetting blends of a rigid polyester (PE) and a poly(urethane acrylate) elastomer (UA) have been investigated over a wide range of compositions in the cast condition, and in use as matrices of unidirectional glass-fibre composites. Transmission electron microscopy showed that blends in the composition range 20%–60% UA have a two-phase structure, probably with a phase inversion from PE-rich to UA-rich matrix between 40% and 50% UA. It was found that the observed variation in Young's modulus with blend composition could be represented by a simple geometrical model based on series/parallel combination of phases with a regular dispersion. This analysis provided supporting evidence for the proposed phase structures of the blends. Further evidence as to the phase structures was the rapid decline in indentation hardness and in temperature of distortion under load which occurred between 40% and 50% UA. Blends with up to 15% UA were found to have higher tensile strength, and slightly higher failure strain, than the unblended polyester. For composites with PE-rich matrices, the transverse Young's modulus exceeded that of the matrix in bulk, and it was found that the relationship could be expressed approximately by a version of the series/parallel model referred to above. Transverse tensile strengths of the composites were, in all cases, lower than the bulk matrix strength. To account for the observed relationship, a modified version of the Cooper and Kelly model for transverse strength is presented.     

Thermal properties of thermoplastic starch/synthetic polymer blends with potential biomedical applicability

Previous studies shown that thermoplastic blends of corn starch with some biodegradable synthetic polymers (poly(-caprolactone), cellulose acetate, poly(lactic acid) and ethylene-vinyl alcohol copolymer) have good potential to be used in a series of biomedical applications. In this work the thermal behavior of these structurally complex materials is investigated by differential scanning calorimetry (DSC) and by thermogravimetric analysis (TGA). In addition, Fourier-transform infrared (FTIR) spectroscopy was used to investigate the chemical interactions between the different components. The endothermic gelatinization process (or water evaporation) observed by DSC in starch is also observed in the blends. Special attention was paid to the structural relaxation that can occur in the blends with poly(lactic acid) at body temperature that may change the physical properties of the material during its application as a biomaterial. At least three degradation mechanisms were identified in the blends by means of using TGA, being assigned to the mass loss due to the plasticizer leaching, and to the degradation of the starch and the synthetic polymer fractions. The non-isothermal kinetics of the decomposition processes was analyzed using two different integral methods. The analysis included the calculation of the activation energy of the correspondent reactions.     

Use of rice husks as potential filler in styrene butadiene rubber/linear low density polyethylene blends in the presence of maleic anhydride

In the present study, rice husks filled styrene butadiene rubber (SBR)/linear low density polyethylene (LLDPE) 50/50 blends with a compatibilizer, maleic anhydride (MAH) were prepared using a brabender plasti-corder. Virgin SBR/LLDPE blend was also prepared. The physico-mechanical as well as dielectric properties were investigated. Increasing MAH concentrations in SBR/LLDPE blends resulted in an increase in the tensile strength, elongation at break and hardness. After a certain concentration (2.5 phr), a reduction in these properties was found. On the other hand an increase in the dielectric properties as well as in the mass swell in both toluene and oil with MAH was noticed. After certain concentration of rice husk filler (25 phr) an abrupt increase in permittivity ε′ and dielectric loss ε″ was obtained. These results are supported by the mechanical properties measurements. The scanning electron microscopy (SEM) indicates that the presence of MAH increases the interfacial interaction between SBR/LLDPE blends on one hand and also rice husk filler and the blend on the other hand.     

木质素及其衍生物对酶的吸附

研究了高沸醇木质素、高沸醇木质素酚、高沸醇木质素胺和木质素树脂对菠萝蛋白酶和木瓜蛋白酶的吸附性能,结果表明:这几种木质素类吸附剂都可以吸附菠萝蛋白酶和木瓜蛋白酶;经改性的高沸醇木质素胺和高沸醇木质素酚的吸附性能优于高沸醇木质素和木质素树脂,且吸附后的酶还能保持较高的活性,高沸醇木质素衍生物有望成为菠萝蛋白酶和木瓜蛋白酶的浓缩吸附剂或固定化的载体.     

Grafting effects of polypropylene/polyethylene blends with maleic anhydride on the properties of the resulting wood-plastic composites

In the presented study, polypropylene (PP) and high density polyethylene (PE) were blended at the ratios of 80/20 and 20/80 to simulate recycled waste thermoplastic mixtures. The effects of in situ grafting of PP/PE blends with maleic anhydride through the extruder on the mechanical and rheological properties of resulting wood/plastic composites were investigated. Different ratios of PP and PE in the blends created distinct properties in the resulting composites. Grafting of PP and PE blends improved the tensile and flexure properties of the resulting composites. The composites exhibited a reduced water uptake and resultant dimensional swelling due to grafting with maleic anhydride. Grafting of the blends also considerably improved the interfacial bonding and enhanced the dispersion of wood in the matrix, as evidenced by rheological analysis and scanning electron microscopy.     

Influence of interaction promoter on the properties of thermoplastic elastomeric blends of natural rubber and polyethylene

The influence of a third component as interaction promoter on the properties of natural rubber-polyethylene thermoplastic blends, both uncured and cured, has been studied. The third component chosen has some structural similarity with polyethylene and is amorphous in nature. Ethylene propylene diene (EPDM) rubber, chlorinated polyethylene and chlorosulphonated polyethylene have been used as the third component. All the third components have better adhesion with the plastic phase and the rubber phase. The adhesive strength is highest with EPDM. The properties are improved by using the above third components both for cured and uncured blends. In comparing the properties, the strength of the composite is divided by the modulus of the composite to take care of the hard-phase contribution. The size of the dispersed domain is reduced by using the third component and is approximately 1.2 m. All the properties could be explained in terms of the strengths of the individual phases, the morphology and the adhesion between components.