Aging properties and mechanism of the modified asphalt by packaging waste polyethylene and waste rubber powder

For the consideration of the environmental and economic issues, retrieved packaging waste polyethylene and waste rubber powder were selected as modifiers to modify the ordinary oil asphalt, and the rotating film oven test was adopted to study the aging process of the modified asphalt. The results showed that the performance of the modified asphalt deteriorated, as indicated by the increase in the softening point and the reduced ductility and penetration. However, compared with nonmodified asphalt, the rangeability of the performance indicators of the modified asphalt before and after aging became narrow, indicating that the aging properties of the modified asphalt were improved. In the modified asphalt system, the swelling of the polymer modifiers was caused by the absorption of the light components of the asphalt, thereby reducing the formation of asphaltenes in the aging process. The polymer modifiers absorb the light oil of the asphalt, which can reduce the content of free radicals and improve the aging properties of the asphalt. In addition, the waste rubber power containing antioxidants and anti‐ozone agents effectively improves the antiaging properties of the asphalt. Copyright © 2012 John Wiley & Sons, Ltd.     

Improving the aging resistance of styrene-butadiene-styrene tri-block copolymer modified asphalt by addition of antioxidants

The aging properties of base asphalt and styrene-butadiene-styrene tri-block copolymer (SBS) modified asphalts (PMA) are evaluated using Fourier Transform Infrared (FTIR) spectroscopy. An aging cell fitted to the FTIR microscope was used to continually and directly study the oxidation of the PMA. In particular, Attenuated Total Reflectance, ATR, with a zinc selenide prism was used to quantify the changes in the spectra of the PMA before and after thin film oven test (TFOT). The effect of a small amount (1 wt%) of some modifiers, zinc dialkyldithiophosphate (ZDDP), zinc dibutyl dithiocarbamate (ZDBC) or naphthenoid oil, on the chemical and physical properties of the PMA was studied. The modification extent of the modifiers increases in the order: oil, ZDBC, ZDDP. With the aging of the PMA, carbonyl groups formed and the intensity of the absorption peak at 965 cm⁻¹ (the characteristic peak of SBS) decreased. Antioxidants, ZDDP or ZDBC modified PMA are resistant to the formation of carbonyl to some extent, indicating the improvement of aging resistance of the PMA by the addition of the antioxidants. ZDDP and ZDBC as antioxidants can retard the oxidation of the PMA through the inhibition of peroxides and radical scavenging. Furthermore, ZDDP in a liquid state at room temperature acts as plasticiser, giving rise to a good aging resistance of PMA.     

Preparation of new full UV-absorbing carbon dots from quercetin and their application in UV-absorbing systems for waterborne polyurethane coatings

In this paper, a kind of novel fully UV absorbing carbon dots (QC-CDs) were prepared as UV absorbers by a one-step hydrothermal method using quercetin as raw material. The prepared QC-CDs have high absorption efficiency (over 98%) in the whole ultraviolet region (200–400 nm), and are almost completely transmitted in the visible light region. The prepared QC-CDs have good stability and resistance to photobleaching. After the treatment with different pH and temperature, the QC-CDs maintained good absorption stability. QC-CDs have a wider UV absorption range than commercial water-soluble organic UV absorbers-BP-4. In terms of aging resistance, QC-CDs can achieve the same effect as BP-4. After subjecting QC-CDs and BP-4 to different pH values, it was found that QC-CDs remain fully UV absorbing at different pH conditions and maintain good absorption stability, but BP-4 loses its function as a UV absorber under alkaline conditions. Then, the UV absorption mechanism of QC-CDs has also been investigated and applied to the UV absorption systems of waterborne coatings PU. Finally, the QC-CDs@PU with full UV absorption properties was applied in the photodegradation prevention experiment of Rhodamine B. At present, the preparation process of QC-CDs is simple and environmentally friendly. QC-CDs have the potential to become a new generation of water-soluble UV absorbers.     

A study on the dispersion, preparation, characterization and photo-degradation of polypropylene traced with rare earth oxides

This research work deals with the effect of rare earth oxides on the PP matrix with respect to the thermal and mechanical properties and to the photo-degradation under UV irradiation exposure. The rare earth oxides are used as tracers for the identification of polymer materials, in order to have an economically efficient recycling and high speed automatic sorting of plastic wastes. The addition of 0.1 wt% of such particles of a micrometric size has a minor effect on the mechanical and thermal properties of the traced materials, as well as on the photo-degradation of the polymer after UV irradiation exposure. For 1 wt% tracer content, before UV irradiation treatment, the melting and crystallization temperatures as well as the thermal stability of the PP matrix are slightly increased, whereas the elongation at break decreases from 10 to 50% for a cross-head speed of 250 mm/min. However, the addition of 1 wt% of CeO₂ improves the photo-degradation resistance of the PP matrix to UV exposure due to the UV light screening effects offered by these particles. The SEM images together with the results obtained from image processing show a homogenous dispersion of tracers in the PP matrix.     

UV aging behaviour of ethylene-vinyl acetate copolymers (EVA) with different vinyl acetate contents

The mild UV aging of ethylene-vinyl acetate copolymer (EVA) with two vinyl acetate (VAc) contents (14, 18 wt%) was performed in a xenon arc source chamber. The degradation mechanism was analyzed via attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR), gel content and high temperature gel permeation chromatography (HTGPC). Photo-chemically induced deterioration was first initiated from vulnerable VAc units. Ketone formation preceded lactone generation, especially in EVA with high VAc content. Un-stable structures induced further degradation in the main chain. Competition between radiation induced cross-linking and chain scission in EVA was observed, and the later was confirmed to be dominant. Higher VAc content resulted in remarkable drop in molecular weight and growth in polydispersity. Apparent re-arrangement in crystallisation and consequent decrease in thermal stability are discussed through differential scanning calorimetry (DSC) and thermo-gravimetric analysis (TGA), which accorded well with the chain scission tendency. Interaction between photo-chemical degradation and physical annealing accounted for the first increasing then decreasing tendency in the mechanical properties of both EVAs.     

Effect of BaTiO3 on the aging process of PLA fibers obtained by centrifugal spinning

This study focused on the fabrication of a composite of polylactic acid fibers reinforced with barium titanate (BT) and obtained by centrifugal spinning. Different concentrations of inorganic powder (5, 10, and 15 wt%) have been added to the polymeric solution and the samples have been studied to monitor any modification in chemical, morphological, thermal, and mechanical properties. Subsequently, samples have been subjected to UV/O₃ irradiation at two different times (5 and 10 min) with the aim to verify the resistance to aging, which is considered a key factor for medical applications and outdoor. The presence of BT influenced strongly the structure of the fibers in many aspects. Samples with the lowest amount of BT showed a clear decrease of chemical and consequently of mechanical properties manifested with the breakage of the fibers subjected to treatment. The other composites apparently showed similar chemical properties comparing with the one without fillers but the mechanical properties clearly decreased. However, what emerged from the study is a clear stability during the aging tests promoted by the presence of BT. The samples with 10 and 15 wt% of BT presented chemical, thermal, and mechanical stabilities differently from the other samples. These results suggested that the fillers clearly modified the degree of crystallinity acting as nucleation agents and promoting the development of a stable crystalline phase during the treatment.     

Influence of thermal and UV treatment on the polypropylene/graphite composite

Electrically conductive polypropylene/graphite (PP/graphite) composites were prepared via blending granulated PP with maleic anhydride grafted PP and natural graphite. Electrical conductivity of prepared samples containing either 65, 70, or 75 wt% of graphite was measured and the most conductive sample containing 75 wt% of graphite was exposed to UV irradiation for 1 and 24 h or thermally treated at 170 °C for 1 h. The influence of thermal and UV exposure on the structural and electrical changes in such treated samples was studied. Local current measurements on the surface were made using scanning spreading resistance microscopy and morphology of the surface was studied by atomic force microscopy. X-ray diffraction analysis, infrared and Raman spectroscopy were also used for the structural characterization. Properties of treated and untreated samples are compared and differences are discussed.     

Mechanical,aging, optical and rheological properties of toughening polylactide by melt blending with poly(ethylene glycol) based copolymers

Two novel biodegradable copolymers, including poly(ethylene glycol)-succinate copolymer (PES) and poly(ethylene glycol)-succinate-l-lactide copolymer (PESL), have been successfully synthesized via melt polycondensation using SnCl₂ as a catalyst. The copolymers were used to toughen PLA by melt blending. The DSC and SEM results indicated that the two copolymers were compatible well with PLA, and the compatibility of PESL was superior to that of PES. The results of tensile testing showed that the extensibility of PLA was largely improved by blending with PES or PESL. At same blending ratios, the elongation at break of PLA/PESL blends was far higher than that of PLA/PES ones. The elongation maintained stable through aging for 3 months. The moisture absorption of the blends enhanced due to the strong moisture absorption of PEG segments in PES or PESL molecules, which did not directly lead to enhance the hydrolytic degradation rate of the PLA. The PLA blends containing 20–30 wt% PES or PESL were high transparent materials with high light scattering. The toughening PLA materials could potentially be used as a soft biodegradable packaging material or a special optical material.     

Impact resistance of hybrid glass fiber reinforced epoxy/nanoclay composite

The effect of nanoclay addition in Glass Fiber Reinforced Epoxy (GFRE) composites on impact response was studied. The epoxy nanocomposite matrix with 1.5 and 3.0 wt% loading of I.30E nanoclay was produced by high shear mixing. Hybrid GFRE nanoclay composite plates were manufactured by hand layup and hot pressing techniques using electrical grade-corrosion resistant (E-CR) glass fiber mats. The laminates were then subjected to low-velocity impact with energies between 10 and 50 J. Addition of nanoclay was found to improve peak load and stiffness of GFRE. Nanoclay loading of 1.5 wt% resulted in optimum properties, with 23% improvement in peak load and 11% increase in stiffness. A significant reduction in physical damage was also observed for hybrid nanocomposite samples as compared to GFRE. This was mainly attributed to transition in damage mechanism due to nanoclay addition. Clay agglomeration in samples with 3.0 wt% loading contributed towards limiting the improvement in impact resistance.     

Influence of aging on thermal behavior and characterization of SBR compound-modified asphalt

Sulfur and polyphosphoric acid (PPA) were used to improve the thermal stability and high-temperature property of styrene–butadiene rubber (SBR)-modified asphalt before and after short-term and long-term aging. The physical, rheological properties, and thermal behavior of asphalt binders were studied. The study showed that the addition of PPA improved the thermal stability and high-temperature property of SBR-modified asphalt evidently, and the improved property caused by the gelation effect of PPA was not influenced by aging further. Though sulfur also improved thermal stability and high-temperature property of SBR-modified asphalt before aging, the improved properties declined evidently with further aging, due to the susceptibility of SBR/sulfur-modified asphalt to aging. It is reasonable to assume that the SBR-modified asphalt could be improved further only by the addition of PPA. In the study of polymer-modified asphalts, thermodynamic analysis can reflect the structural characteristics of asphalt binders before and after aging efficiently and confirms the conclusions of physical and rheological testings to some extent.     

Deactivation of excited states of kynurenine covalently linked to nitroxides

Due to ability of stable nitroxides to interact with free radicals, they are used as antioxidants for therapeutic and research goals in biology and medicine. A modern trend in medical chemistry is the design of multifunctional molecules such as UV absorbers covalently bound to nitroxides, which provides both UV protection and antioxidant properties combined in the same molecule. In the present work, we report the synthesis of conjugates of a natural UV filter kynurenine (KN) with nitroxides (KN‐RNO^• conjugates) and the study of their photochemical properties in aqueous and methanol solutions. Due to the spin‐exchange interaction between KN and nitroxide moieties, the triplet lifetimes in conjugates are much shorter than in KN molecule, but the triplet quantum yields are significantly higher. The reaction of intramolecular electron transfer between photoexcited KN and nitroxide moieties is the main factor determining the quantum yield of KN‐RNO^• conjugates photodecomposition. Consequently, KN‐RNO^• conjugates in aqueous solution are photochemically less stable than the parent KN molecule. Nevertheless, the photostability of KN‐RNO^• conjugates is much higher than that of cinnamates which are widely used as UV absorbers in modern sunscreen formulations. Thus, the combination of the endogenous chromophore KN with nitroxides is very promising for medical applications.     

Sound absorption behavior of flexible polyurethane foams including high molecular‐weight copolymer polyol

Noise pollution is an important issue for automotive industries. In this article, the high molecular‐weight copolymer polyol is blended in the polyol mixtures for fabricating flexible polyurethane foams to improve sound absorption efficiency. Changes of cavity size and material density of the foams are negligible by inclusion of copolymer polyol in the polyol mixture, but the closed pore ratio and specific airflow resistance increase for the copolymer polyol content higher than 20 wt% because of changes of phase separation behavior from drainage flow rate reduction that occurs with increased viscosity. Sound absorption efficiency increases with increasing copolymer polyol content up to 20 wt%, but it decreases beyond this point. The sound absorption property mainly results from the closed pore ratio, not from the cavity size. The compression strength increases with increasing copolymer polyol contents by increased amount of hard segments. Therefore, an optimum amount of high molecular‐weight polyol is recommended for enhanced sound absorption property.     

亲水性聚硅氧烷改性天然乳胶的性能

以亲水性聚硅氧烷KGF-903共混改性天然乳胶,通过拉力试验、老化试验、接触角测量和扫描电子显微镜等研究了聚硅氧烷的添加量对天然乳胶力学性能、抗老化性能、亲水性能和表面形貌的影响。结果表明,KGF-903含量在1.5%时拉伸强度有最佳的改性效果;KGF-903添加量约为3%时断裂伸长率达到最大,老化前后的断裂伸长率比改性前分别提高57%和50%。随着KGF-903含量的增加,改性天然乳胶片的水接触角逐渐减小;扫描电子显微镜观察的结果表明,添加聚硅氧烷能改变乳胶的分散状态。利用小试的最佳配方(即KGF-903的添加量为1.5%)生产了2批次医用导尿管,其表面光洁度、导尿管球囊的成品率、管身硬度、连接器与导尿管排泄锥形接口所承受的拉力和充气漏斗与引流漏斗连接处所承受的拉力等均有显著的提高,有效改善了产品的质量。     

Soft-templating synthesis and adsorption properties of mesoporous carbons with embedded silver nanoparticles

Mesoporous carbons containing silver nanoparticles have been successfully synthesized under acidic conditions by employing resorcinol and formaldehyde as carbon precursors and triblock copolymer EO₁₀₁PO₅₆EO₁₀₁ (Lutrol F127) as a soft template. Silver nanoparticles of ∼90 nm were added to the synthesis mixture to achieve 10 wt% and 20 wt% of Ag loading in the carbon. Also, tetraethyl orthosilicate (TEOS) was introduced to the system in order to improve adsorption properties of the silver-carbon composites and to reinforce its structure. The resulting carbons with incorporated silver nanoparticles featured high surface areas, large total pore volumes and primary mesopores in the range between ∼6–7 nm.     

Electrospun fibrous membranes of poly (lactic-co-glycolic acid) with β-tricalcium phosphate for guided bone regeneration application

Guided bone regeneration (GBR) have been proved great success for the treatment of bone defects in oral implantology. Bone defects are reconstructed by the use of a barrier membrane which prevents the invasion of soft tissue and create a space for guiding new bone growth into the bone defect. To develop GBR membranes with higher bioactivity, poly (lactic-co-glycolic acid) (PLGA) fibrous membranes containing β-tricalcium phosphate (β-TCP) were fabricated via electrospinning. The presence of 5 wt% and 10 wt% of β-TCP in the fibers improved mechanical properties. In vitro biocompatibility results have shown that all membranes are non-cytotoxic and the presence of β-TCP increased cell adhesion and proliferation. Furthermore, cell viability results demonstrated that the presence of 5 wt% β-TCP is advantageous for osteoblast proliferation. Therefore, the results suggest that PLGA with 5 wt% β-TCP fibrous membranes meet the requirement of morphological, physical, mechanical and bioactive properties for an effective GBR membrane.     

Magnetic field assisted μ-solid phase extraction of anti-inflammatory and loop diuretic drugs by modified polybutylene terephthalate nanofibers

A magnetic nanocomposite consisting of nanoparticles–polybutylene terephthalate (MNPs–PBT) was electrospun and used as an extracting medium for an on-line μ-solid phase extraction (μ–SPE)–high performance liquid chromatography (HPLC) set–up with an ultraviolet (UV) detection system. Due to the magnetic property of the prepared nanofibers, the whole extraction procedure was implemented under an external magnetic field to enhance the extraction efficiencies. The developed method along with the synthesized nanocomposite were found to be appropriate for the determination of trace levels of selected drugs including furosemide, naproxen, diclofenac and clobetasol propionate in the urine sample. The prepared MNPs-PBT electrospun nanocomposite was characterized using the scanning electron microscopy (SEM), energy dispersive spectroscopy (EDX) and Fourier transform infrared (FT–IR) spectroscopy. The prepared magnetic fibers showed high porosity, which was another driving force for the extraction efficiency enhancement. Major parameters affecting the extraction efficiency of the selected drugs were optimized. The limits of detections (LOD) of the studied drugs were in the range of 0.4–1.6 μg L⁻¹ and the limits of quantification (LOQ) were 1–4 μg L⁻¹ under the optimized conditions. Relative standard deviation (RSD%) for three replicates at three concentration levels of 6, 100 and 400 μg L⁻¹ were 5.9–8.0% while acceptable linear range with two orders of magnitude was obtained (R² = 0.99). The method was validated by the determination of the selected drugs in urine samples and the results indicated that this method has sufficient potential for enrichment and determination of the desired drugs in the urine sample. The relative recovery values were found to be in the range of 78–91%. Implementing the developed on–line μ–SPE method under the external magnetic field induction, led to higher extraction efficiencies for the selected drugs with various diamagnetic properties.     

Toughening of isothermally polymerized cyclic butylene terephthalate for use in composites

Interest in thermoplastic composites is growing because of their advantages over thermosets in recyclability and in toughness. The melt viscosity of thermoplastic polymers is very high, which makes fibre impregnation difficult. This can be solved by using in-situ polymerization with cyclic butylene terephthalate (CBT). However this leads to a brittle PBT. To solve this problem physical and chemical modification of the polymerized CBT (pCBT) was performed, to disturb the crystallization. Chemical modification with PC and with PTHF has an embrittling effect because of a bad chemical interaction. When polycaprolactone is added to the CBT a copolymer is formed which leads to a lower crystallinity, resulting in a higher toughness of the pCBT. This tougher matrix material was used in composites and a two times tougher composite is produced when only 7 wt% PCL is added to the CBT. The physical modification evaluated was the addition of carbon nanotubes (CNT). Although an increase in stiffness and strength of the pCBT is seen when CNTs are added up to 0.1 wt%, the failure strain decreases.     

Morphology, crystallization behavior and properties of impact-modified polypropylene copolymer with or without sodium benzoate as a nucleating agent

 The morphology, crystallization behavior, and properties of an impact-modified polypropylene (PP) copolymer with or without sodium benzoate were investigated. The contents of ethylene–propylene rubber (EPR) in the reactor-made PP copolymer is about 15 wt%. For comparison, blends of PP and EPR containing the same EPR composition were prepared by melt-mixing. Morphological studies by scanning probe microscopy indicated that the impact-modified copolymer consists of three different phases, i.e., polyethylene, PP, and EPR phases, which is considerably different from the morphology of the conventional PP/EPR blend of the corresponding composition. The impact-modified PP copolymer exhibited a higher crystallization rate in terms of the lower crystallization half-time and thus higher thermal and mechanical properties, such as impact strength and hardness, than the PP/EPR blend did. The addition of sodium benzoate as a nucleating agent to the copolymer increased the crystallization rate and the mechanical properties. Received: 4 June 2001 Accepted: 31 October 2001     

SBS改性沥青机理研究进展

介绍了沥青的特性、苯乙烯-丁二烯-苯乙烯三嵌段共聚物(SBS)的性能,分析了SBS与基质沥青之间的溶胀性和相容性问题,着重论述了SBS改性沥青机理的研究进展,指出机理主要分为物理共混和化学改性两类:物理共混——SBS微粒受到沥青组分中油分的作用发生溶胀而均匀分散在沥青中,SBS与沥青之间没有发生化学作用,只是一种分子间作用力;化学改性——加入添加剂使沥青和SBS之间发生加成、交联或接枝等化学反应,形成较强的共价键或离子键,改善沥青的化学性质。提出化学改性是提高SBS改性沥青路用性能的重要手段。     

Effect of UV-absorbing agents on photodegradation of tranilast in oily gels

Tranilast (TL) oily gels containing UV-absorbing agents (UV absorber) were prepared, and the effect of the agents against photodegradation of TL was investigated. When 0.1% TL oily gel without UV absorber was exposed to light, TL was photochemically decomposed to the extent of 74.1% of its initial content at the end of the first hour. Although there were differences in the preventive effect on photodegradation of TL depending on the UV absorbers employed, 2-(2-benzotriazolyl)-p-cresol (BTPC) was the most effective absorber. The addition of UV absorbers to the oily gel did not affect the release of TL from the gel, the skin permeation, or the skin concentration of TL following topical application. UV absorbers added to TL oily gel penetrated into skin; however, their concentration in skin was similar to that following application of commercial sunscreen. These results suggest that the addition of UV absorbers to the oily gel of TL may be useful in preventing photodegradation of TL in the gel.