Ageing by UV radiation of an elastomer modified bitumen

Laboratory methods to simulate the short- and long-term ageing occuring during the service life of pure and polymer modified bitumens in a pavement are standardized but none of them takes into account the influence of UV radiations. If the impact of thermal ageing on the degradation of SBS elastomers in bitumens has been extensively studied, there is not study dealing with the photo-oxidation of these copolymers in a bituminous matrix. So, the aim of our study was to investigate, by FTIR spectrometry and SEC chromatography, whether the architecture of elastomers (linear or radial) might have any influence on their ageing by UV radiation in a bituminous matrix. The results show that the elastomers oxidation kinetic, unlike the disappearance kinetic of trans-butadiene double bond, does not depend on their architecture. But, when putted into the same base bitumen, the two copolymers show exactly the same oxidation kinetic and the same decreasing kinetic of trans-butadiene double bond. So, this study has revealed that inside the bituminous matrix, on the one hand, the elastomers architecture does not influence on its degradation when submitted to UV radiation and, on the other hand, there is a “protection” of the elastomers by the studied bitumen towards UV radiation.     

Infrared microscopy investigation of oxidation and phase evolution in bitumen modified with polymers

Increase in traffic volume has led to a wider use of Polymer modified Bitumens (PmB’s) in road construction. Although the mechanical properties of such materials have been widely studied, their change with time in service, also called ageing, is yet to be fully understood.One of the most important issues is to identify the process involved: is PmB ageing a consequence of bitumen ageing, polymer ageing or both at the same time? Moreover, most PmB’s feature a two-phase structure made of polymer rich areas along with polymer poor regions, depending on the bitumen chemistry, the polymer nature and content. It is therefore important to take this peculiar structure into consideration when trying to sort out the respective effect on ageing of the polymer and the bitumen. Infrared microscopy allows characterizing separately different phases in heterogeneous products; therefore it is appropriate for PmB’s.In this paper, PmB’s were studied in their original state and after conventional tests claimed to simulate the ageing during the mixing process and several years of road service (RTFOT + PAV). The PmB’s included plastomers and elastomers, some of them being in situ crosslinked. Infrared microscopy was used to determine for each phase the polymer rate and functional indices characterizing the bitumen such as aromaticity, aliphaticity and condensation, and also to map the polymer distribution in the PmB.The characterization of PmB in their original state points out which species of the bitumen are involved in the polymer swelling and the effect of the polymer nature. The characterization of the same PmB’s after the RTFOT + PAV ageing shows how the bitumen species responsible for the swelling evolve during ageing. In addition, kinetic studies were performed using an heating cell fitted to the IR microscope. They confirmed the tendencies obtained with the conventional ageing tests.These studies come to the conclusion of an interdependence of the ageing of the different constitutive phases in a PmB and of chemical exchanges between them. They make clear the micro-morphological modification induced by ageing in a PmB. They finally help to better understand the effect of a crosslinking on the PmB microstructure and its ageing mechanism.     

微藻油改性沥青耐老化性能研究

为缓解石油沥青短缺局势,探索微藻油用于沥青改性可行性及改性沥青长期性能,将微藻液经降解、离心、萃取得到微藻油并制备改性沥青。通过不同微藻油掺量下改性沥青延度、软化点和黏度确定微藻油最佳掺量,通过高低温流变试验、混合料路用性能试验分析微藻油改性沥青经旋转薄膜烘箱(RTFOT)短期老化、压力老化容器(PAV)长期老化和紫外老化后性能变化并与SBS改性沥青对比,借助红外光谱分析微藻油改性沥青分子结构组成。结果表明:微藻油掺量为30%(外掺质量分数)时,改性沥青延度达到最大值,软化点和黏度满足改性沥青要求;微藻油改性沥青和苯乙烯-丁二烯-苯乙烯嵌段共聚物(SBS)改性沥青经RTFOT短期老化后性能差异不显著,微藻油改性沥青耐PAV长期老化和耐紫外老化性能优于SBS改性沥青,尤其是耐紫外老化性能更优。红外分析表明两种改性沥青均含有乙烯基双键、芳香族C—H、甲基和亚甲基等类似成分,但芳香族C—H、伸缩C—C成分含量存在差异。微藻油改性沥青比SBS改性沥青增加的酰胺不饱和基团和羧基利于改性沥青形成网络分子结构。     

Improvement of bitumen performance with epoxy resin

This paper studies the modification of petroleum bitumen with epoxy resin. Different amounts of epoxy were doped into bitumen with 50/70 penetration grade and variations in viscosity as a function of temperature and additive concentration were determined. The effects of the epoxy additive were examined by rheometer, penetration, softening point, DSR (dynamic shear rheometer), DSC (differential scanning calorimeter), RTFOT (rolling thin film oven test), PAV (pressure aging vessel), BBR (bending beam rheometer) and surface tension tests. Adhesion and stability of bitumen aggregate mixtures prepared using original and modified bitumen were compared using Nicholson stripping and Marshall tests. The optimum dosage of the additive yielding the best rheological and performance properties was found to be 2% (w/w). Appreciable decrease in the formation of rutting, bleeding, stripping and cracking of modified bitumen may be obtained through epoxy addition.     

Artificial aging of polymer modified bitumens

This paper presents an investigation of artificial aging of polymer modified binders, prepared from three base bitumens and six polymers. Aging of the binders was performed using the Thin Film Oven Test (TFOT), the Rolling Thin Film Oven Test (RTFOT), and modified RTFOT (MRTFOT). The binders were characterized by means of infrared spectroscopy, different types of chromatography, and dynamic mechanical analysis. It was found that the effect of aging on the chemistry and rheology of the modified binders was influenced by the nature of the base bitumens and was strongly dependent on the characteristics of the polymers. For styrene–butadiene–styrene (SBS) and styrene–ethylene–butylene–styrene (SEBS) modified binders, aging decreased the complex modulus and increased the phase angle. Aging also increased the temperature susceptibility of these modified binders. The rheological changes of SBS modified bitumens were attributed to polymer degradation and bitumen oxidation. However, for SEBS modified bitumens, the mechanisms of aging are unclear. In the case of ethylene vinyl acetate (EVA) and ethylene butyl acrylate (EBA) modified binders, the process of aging increased the complex modulus and elastic response (decreased phase angle), and reduced temperature susceptibility. These changes were mainly due to the oxidative hardening of the base bitumens. The study also showed statistically significant correlation between TFOT, RTFOT, and MRTFOT. However, no definite conclusions could be drawn regarding the difference in severity of aging between these methods. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 76: 1811–1824, 2000     

Physico-chemical analysis of five hard bitumens: Identification of chemical species and molecular organization before and after artificial aging

The present paper focuses on a physico-chemical analysis of five different types of bitumens, both before and after aging. These bitumen samples were chosen based on: the original crude oil (straight-run bitumens with different asphaltene and crystallized fraction contents), mode of refining (straight-run vs. half-blown bitumen), and modifier characteristics (straight-run vs. polyphosphoric acid (PPA)-modified bitumen). The aim of this study is to determine both the aging effect on chemical species and the chemical organization as a function of the type of bitumen sample.In order to obtain information on bitumen chemistry, n-heptane precipitation (Standard NF EN 12591), IATROSCAN chromatography (coupling between a thin-layer liquid chromatography on a silica gel and a flame ionization detector), FTIR spectroscopy and differential scanning calorimetry (DSC) have all been used. Size exclusion chromatography under “high-speed” conditions (HS-SEC), which yields information relative to asphaltene associations, was also introduced. Several years of road aging were simulated through 25 h of a pressure aging vessel (PAV) test.The coupling of IATROSCAN chromatography and n-heptane precipitation made it possible to identify and quantify polar resins.In accordance with previous studies, the use of HS-SEC combined with IATROSCAN chromatography indicates that a modification by PPA leads to an increase in asphaltene content and a more dispersed asphaltene structure than that found in pure bitumen. This same conclusion can be drawn from observations of the half-blown bitumen sample. The half-blown bitumen actually contains less asphaltene than one of the straight-run bitumens in the study; furthermore, its asphaltenes are more highly agglomerated. These results demonstrate that asphaltene association does not systematically depend on quantity alone, as its chemical type also enters into play. Moreover, during aging, even though asphaltene content is increasing for all bitumen samples, its agglomeration is still highly dependent on the type of bitumen. It would therefore appear that the presence of crystallized fractions exerts a major influence on this process.     

Multi-fractal morphology of un-aged and aged SBS polymer-modified bitumen

Polymer-modified bitumen (PmBs) has been characterised by fluorescence microscopy, conventional performance tests and by the rheological measurements, before and after the Rolling Thin Film Oven Test (RTFOT), and by multi-fractal analysis. The addition of 2–7 wt-% of linear styrene-butadiene-styrene block copolymer (SBS-L) or radial block copolymer (SBS-R) increased viscosity, softening point and complex modulus of PmBs. Hardening of PmBs occurred and the elastic response decreased after RTFOT aging. SBS-L PmBs are more susceptible to RTFOT aging. Digital fluorescence micrographs of sections of PmBs qualitatively exhibit different morphological structures which can be quantitatively probed by multi-fractal analysis: differences are reflected in the f (α) spectrum. The PmBs which appear less multi-fractal have the best rheological properties. In another approach, the focal fractal dimensions’ distributions for the SBS-modified bitumen have peak around 2.35 (which corresponds to the bitumen-rich phase) and around 2.7 (which corresponds to the noncontinuous SBS-rich phase).     

Rheological properties of styrene butadiene styrene polymer modified road bitumens

The use of polymers for the modification of bitumen in road paving applications has been growing rapidly over the last decade as government authorities and paving contractors seek to improve road life in the face of increased traffic. Currently, the most commonly used polymer for bitumen modification is the elastomer styrene butadiene styrene (SBS) followed by other polymers such as styrene butadiene rubber, ethylene vinyl acetate and polyethylene. This paper describes the polymer modification of two penetration grade bitumens with SBS. Six polymer modified bitumens (PMBs) were produced by mixing the bitumens from two crude oil sources with a linear SBS copolymer at three polymer contents. The rheological characteristics of the SBS PMBs were analysed by means of conventional as well as dynamic mechanical analysis using a dynamic shear rheometer (DSR). The results of the investigation indicate that the degree of SBS modification is a function of bitumen source, bitumen-polymer compatibility and polymer concentration, with the higher polymer concentrations in a high aromatic content bitumen producing a highly elastic network which increases the viscosity, complex modulus and elastic response of the PMB, particularly at high service temperatures. However, ageing of the SBS PMBs tends to result in a reduction of the molecular size of the SBS copolymer with a decrease in the elastic response of the modified road bitumen.     

Influence of poly(phosphoric acid) on the properties and structure of ethylene–vinyl acetate‐modified bitumen

Ethylene–vinyl acetate (EVA) modified (EM) bitumen was modified further by the addition of poly(phosphoric acid) (PPA). Owing to the gelation and acidification effect of PPA, the high‐temperature properties and compatibility of EM bitumen were improved greatly. Part dissolution of EVA after acidification was confirmed by the viscous behavior of EVA/PPA‐modified (EPM) bitumen in rheological tests to some extent. Morphology observation illustrated the decomposition of EVA in bitumen after PPA modification and ageing. Fourier transform infrared analysis proved that the hydrolysis reaction took place between the vinyl acetate segment of EVA molecule and the extra hydrogen protons of PPA. Thermal analysis displayed the thermodynamic behaviors of EM and EPM bitumens before and after ageing and confirmed the part dissolution of EVA further after PPA acidification. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46553.     

Artificial weathering effect on the structure and properties of polypropylene/polyamide‐6 blends compatibilized with PP‐g‐MA

The degradation of uncompatibilized and compatibilized PP/PA‐6 (70/30 wt %) with PP‐g‐MA under accelerated UV light was investigated using Fourier Transform Infrared Spectroscopy (FTIR) spectroscopy, melt flow index (MFI) tester, tensile test, differential scanning calorimetry (DSC), thermogravimetric analysis (TGA) and scanning electron microscopy (SEM). FTIR analysis of the structure of the compatibilized and uncompatibilized blends after exposure to UV light showed the formation of photoproducts corresponding to both components. The MFI and mechanical results obtained revealed that photooxidation started primarily in PA‐6 rather than PP. In addition, the uncompatibilized blends exhibited a higher degradation rate compared to neat polymers for long exposure time, and the addition of PP‐g‐MA increased slightly their ageing rate in accordance with TGA data. Further, DSC analysis showed an increase in the crystallinity index and a decrease in the melting temperature of PP and PA‐6 after UV exposure either as neat polymers or as blend components. SEM micrographs of the cryo‐fractured surfaces of the samples illustrated the formation of cracks and fractures after UV irradiation. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41722.     

不饱和聚酯树脂／大麻纤维复合材料紫外老化性能的研究

采用模压工艺制备不饱和聚酯树脂/大麻纤维复合材料,研究紫外线光老化试验对此种复合材料及氨水处理复合材料力学性能的影响,利用红外光谱(FTIR)技术研究老化前后复合材料结构的变化.研究结果表明,氨水处理大麻纤维可以改善复合材料的拉伸性能以及拉伸模量.未处理及氨水处理的复合材料,在试验一个周期后,两种复合材料的拉伸强度较老化前分别提高了10.8%和19.1%,未处理的复合材料的弯曲强度在两个试验周期时达到最大值.氨水处理的复合材料,在试验的第一周期时,拉伸模量下降最快,进一步老化之后,下降幅度明显减缓.氨水处理的复合材料的拉伸模量在第三个试验周期结束时,弯曲模量和冲击强度比未老化前分别上升6.3%和25.3%.FTIR显示,老化后,两种复合材料的吸收峰强度减弱,但氨水处理的复合材料吸收峰强度比未处理的强.     

再生沥青流变性能对比评价研究

通过对三种再生剂制备的再生沥青及其RTFOT后残留沥青、PAV后残留沥青进行SHRP分析,研究了具有不同化学组成和分子量的三种再生剂R1、R2、R3对老化沥青的再生能力。实验结果表明:再生剂的加入使再生沥青的高温抗车辙能力与新鲜基质沥青相比略有降低;再生剂的加入增强了再生沥青的抗疲劳能力及抗低温开裂能力,其中芳香分含量较高的再生剂在改善沥青抗疲劳能力及抗低温开裂能力方面具有优势。     

三元乙丙橡胶热氧老化试验与密封条寿命预测

运用热空气加速老化试验方法对塑钢窗密封条用三元乙丙橡胶进行了不同温度下的老化,并对其使用寿命进行了预测。首先建立了基于Arrhenius原理的老化寿命预测模型,然后对该数学模型进行了验证和统计分析。结果表明,模型预测结果与实验值吻合很好,相关系数大于0.99。根据预测值与试验值的偏差对预测模型进行了进一步修正,根据修正后的模型预测得到30℃下、拉断伸长率保持率在70%时,密封条的使用寿命为68.73年。     

Structure and artificial ageing behavior of organo montmorillonite bitumen nanocomposites

This paper studied the structure and ageing behaviors of bitumen modified with organo montmorillonite (OMt). Two OMt with different surfactants were used to modify one base bitumen using a laboratory high-shear mixer. The rolling thin film oven test and the pressure air oven test were performed to simulate the short term (ST) and long term (LT) ageing on the bitumen, respectively. The structures of OMt were determined by X-ray diffraction, fluorescence microscopy and computed tomography (CT) scanning. The ageing behaviors were evaluated with a dynamic shear rheometer. The intercalated structure of both OMt was observed in the bituminous matrix. This structure improved the ST ageing behaviors of bitumen. With respect to the LT ageing, an automatic accumulation of OMt particles took place under the tough artificial ageing conditions, and consequently led to a less improvement in the ageing behavior.     

Effect of UV and hygrothermal aging on the mechanical performance of polyurethane elastomers

In this study, the effects of environmental aging on the mechanical performance of elastomeric polyurethane (PU) were investigated using two accelerated aging techniques, namely, ultraviolet (UV) and hygrothermal (HT). Samples were prepared and subjected to UV and HT exposure for a period of 5 months and removed and mechanically tested at different time intervals. Differential scanning calorimetry (DSC) was performed. A noticeable change in the chemical structure of the PU after 1 month of UV exposure was found, however, that was not the case after 1 month of HT exposure. The stress and strain to failure, tearing energy, and storage modulus were evaluated at different intervals for both aging techniques. It was found that the UV exposure caused severe degradation of the PU in comparison with the HT. A reduction of more than 98% in the tearing energy was observed for the UV‐exposed samples after 5 months when compared with only a 35% reduction in the tearing energy for the HT‐exposed samples. A similar trend was observed for tear strength and storage modulus. The degradation mechanisms of the PU elastomers have been identified using SEM and correlated with the tearing energy. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Assessment of Asphalt Rheological Behaviors by Studying Their Aromatic Structures

Abstract

Assessment of asphalt rheological behaviors during road service life requires to better know original asphalt chemical structures responsible of its main mechanical features. For this purpose, the nature of the asphalt chemical structures were characterized by using Fourier transformed Infrared (FTIR) and Synchronous UV Fluorescence (SF) spectroscopies. Indices based on the ratios of some FTIR absorption bands were established to evaluate aromatic and aliphatic structure contents of 10 asphalt cements. For instance, valuable information about aromatic families was obtained from SF indices which were related to FTIR indices. Relationships between these structural characteristics and the rheological properties were evaluated using Principal Component Analysis and Multivariate Linear Regression. As a result, bitumen rheological properties, at low or at high temperature, were found to greatly depend on the aromatic substitution and condensation degree, the aliphatic/ aromatic structure ratio and the vanadium contents. Hence, some rheological properties could be predicted from less than five SF/FTIR indices.     

Natural Weathering Test of Styrene Butadiene Rubber and Recycled Acrylonitrile Butadiene Rubber (SBR/NBRr) Blends

The effect of recycled acrylonitrile butadiene rubber (NBRr) content of SBR/NBRr blends on natural weathering was studied. Three different size of NBRr (S1; 117–334 µm, S2; 0.85–15.0 mm and S3; direct sheeted form) were used and the blends were exposed to natural weathering for 3 and 6 months. The results indicated that the SBR/NBRr blends with smallest size of NBRr (S1) show a better retention of tensile properties, which are able to withstand better weathering than coarser size (S2 and S3) of SBR/NBRr blends. The presence of hydroxyl, carbonyl and nitro group after exposure to natural weathering was detected in FTIR analysis, which related to the UV oxidation process of rubber blends. The scanning electron microscopy proved that the SBR/NBRr blends with smallest size of NBRr (S1) with higher content of NBRr, shows a better resistant to natural weathering.     

Influence of ageing on viscoelastic properties of PMMA/ATH modified bitumen

This article deals with the influence of the ageing treatment on the viscoelastic behavior of PMMA/ATH modified paving bitumen. Waste composite powder (polymethyl methacrylate filled with aluminium trihydrate)—PMMA/ATH and Fischer–Tropsch wax were used as modifying agents for 70/100 paving grade bitumen. Measurements in intermediate temperature range were carried out under oscillatory shear conditions on a dynamic shear rheometer (DSR). Creep testing in low temperature range was conducted on a bending beam rheometer (BBR). The time‐dependent behavior of investigated samples was presented in a form of relaxation moduli G(t) and E(t). Dynamic moduli, i.e., G′(ω) and G″(ω), were converted to relaxation modulus G(t) using the Schwarzl method. The interconversion between tensile creep compliance D(t), and tensile relaxation modulus E(t) was performed using the Hopkins and Hamming approach. It was found that modified binders are less susceptible to the oxidation process during bitumen ageing, since the viscoelastic properties changed less than for the base bitumen. Our results indicate that the use of waste PMMA/ATH in the selected bitumen altered the time‐dependent deformation behavior of asphalt binder. The effect of ageing treatment on material functions was particularly manifested at longer times. Different stress relaxation behavior of modified binders could result in higher deformation resistance of asphalt mixture. POLYM. COMPOS., 36:1738–1747, 2015. © 2014 Society of Plastics Engineers     

Degradation behavior of an ultraviolet and hygrothermally aged polyurethane elastomer: Fourier transform infrared and differential scanning calorimetry studies

The degradation behavior of an elastomeric polyurethane (PU) was investigated with accelerated ultraviolet (UV) and hygrothermal (HT) techniques. Samples were subjected to UV exposure and HT conditions for 3 or 5 months and were removed in 1‐month intervals from the test chambers. Their chemical structure was evaluated with Fourier transform infrared (FTIR) spectroscopy. The thermal transitions of the aged samples were evaluated with differential scanning calorimetry (DSC). Both FTIR and DSC results showed no evidence of significant structural damage to the HT‐aged PU throughout exposure. FTIR analysis of the UV‐aged samples showed a noticeable change in the chemical structure of the polymer after 1 month of UV exposure. The results from DSC correlated with the FTIR analysis of the UV‐aged samples. Spectroscopic and thermal analysis of the aging of the PU samples was correlated to mechanical analysis. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Effect of waste polymer addition on the rheology of modified bitumen

This paper deals with the modification of petroleum bitumen with four different types of waste polymers. EVA, EVA/LDPE blend, crumb tire rubber and ABS, all of them coming from recycling plants of waste plastic materials, were used as modifying agents of the bitumen employed in the pavement building. Optical microscopy, modulated calorimetry and a set of different rheological tests were developed in order to characterise the modified bitumens. The results obtained reveal that tire rubber as well as its blends with other polymers can be considered as an interesting modifier of the bitumen in a wide range of temperatures. As an elastomer, it endows the pavement a higher flexibility, which makes it more resistant to the traffic loading. The blend composed of EVA and LDPE displays quite promising results at high in-service temperatures, due to the development of a polymer network throughout the modified bitumen. Furthermore, the calorimetry tests carried out demonstrate different degrees of compatibility between the bitumen and the polymers used.