摘要
将苯并三唑(UV326)光稳定剂插至层状双氢氧化物(LDHs)层间得到UV326插层LDHs,探究了其对沥青抗紫外老化性能的影响.结果表明:与复合UV326/LDHs改性沥青相比,UV326插层LDHs与沥青的相容性和对紫外光的吸收能力上有较大提升效果; UV326插层LDHs掺量为1%时,其对沥青的常规性能、高温稳定性及抗疲劳性能提升效果最佳;掺量较高时,相较于复合UV326/LDHs,UV326插层LDHs对沥青的弹性性能、疲劳性能及抗紫外老化性能的劣化效果更弱.
现有科学研究证实,控制紫外光对沥青光老化的影响,可以极大地延长强紫外线辐射地区公路的使用寿
苯并三唑(UV326)是紫外吸收剂(UVA)中产量最大的一类,其研究工艺成熟,原料成本低,在UVA改性沥青的研究中,表现出较好的改性效
基于插层手法,将具有特定功能的插层客体插入至具有层状结构的主体插层物层间,一方面能赋予主体插层物指定功能,另一方面能提高客体的稳定性.本文将UV326插层至LDHs层间得到UV326插层LDHs,研究其对沥青物理性能、流变性能、抗疲劳性能及紫外老化性能的改善效果.
沥青为中国石化生产的70# A级道路石油沥青;LDHs由合肥巴斯夫生物生产,分子式为Mg6Al2(OH)16CO3·4H2O;UV326由东莞山一塑化有限公司生产,分子式为C17H18N3OCl.
采用离子交换法,对UV326与LDHs进行插层处理,再利用硬脂酸钠对插层后的LDHs浆液进行有机化处

图1 插层流程示意图
Fig.1 Schematic diagram of intercalation process
改性剂包括:LDHs与UV326摩尔比为1∶1的复合UV326/LDHs;UV326插层LDHs.改性剂的掺量w(质量分数,以沥青的质量计)为0%(基质沥青)、1%、3%、5%.采用上海Frank公司生产的FM300高速剪切混合机,通过熔融共混配制沥青样品.设置温度为(150±5) ℃,加热基质沥直至其完全流动,将复合UV326/LDHs、UV326插层LDHs添加至沥青中混合,以5 000 r/min的剪切速率剪切1.0 h.基质沥青、复合UV326/LDHs改性沥青、UV326插层LDHs改性沥青分别记为OA、RLA、ILA.试样命名规则为:RLA1为改性剂掺量w为1%的RLA;其他类推.
采用波长为365 nm的LED紫外灯作为光源,对3组沥青开展紫外老化试验.试验过程为:将试样放入预热硅胶模具中,冷却至25
采用日本Rigaku Smartlab9KW型X射线衍射仪(XRD)对UV326插层LDHs进行微观结构表征.采用德国Leica DM4 M型荧光显微镜对ILA与RLA进行荧光显微镜成像,评价复合UV326/LDHs、UV326插层LDHs与沥青的相容度.使用日本岛津UV‑2700紫外-可见分光光度计测试UV326插层LDHs与复合UV326/LDHs改性沥青紫外-可见光谱,分辨率为1 nm.基于动态剪切流变(DSR)试验的温度扫描模型,温度区间为30~60 ℃,得到老化前后沥青的复数剪切模量G*和相位角δ.基于DSR的LAS模型,在25 ℃下测试了沥青老化后的抗疲劳性能,以累积损伤参数D为横坐标,复数剪切模量与初始复数剪切模量G的绝对值之比|G*|/|G|(表征沥青完整性的参
LDHs、UV326插层LDHs的XRD图谱见

图2 LDHs、UV326插层LDHs的XRD图谱
Fig.2 XRD patterns of LDHs and UV326 intercalated LDHs
RLA5及ILA5的荧光显微镜图像见

图3 RLA5及ILA5的荧光显微镜图像
Fig.3 Fluorescence microscope images of RLA5 and ILA5
沥青的紫外光吸收曲线见

图4 沥青的紫外光吸收曲线
Fig.4 UV absorption curves of asphalts
研究了沥青的25 ℃针入度P、10 ℃延度D、软化点S及135 ℃布氏黏度V等物理性能,结果见

图5 沥青的物理性能
Fig.5 Influence of physical properties of asphalts
沥青的相位角δ、复数剪切模量G*及车辙因子G*/sin δ见

图6 沥青的相位角、复数剪切模量及车辙因子
Fig.6 Phase angles, complex shear modulus and rutting factors of asphalts
沥青的抗疲劳性能见

图7 沥青的抗疲劳性能
Fig.7 Fatigue resistance of asphalts
根据AASHTO TP101‑14《Standard method of test for estimating damage tolerance of asphalt binders using the linear amplitude sweep》,计算沥青的平均疲劳寿命Nf,考虑到不同应变水平对沥青疲劳性能有影响,设置应变水平为2.5%与5.0

图8 沥青的平均疲劳寿命
Fig.8 Average fatigue life of asphalts
采用残留延度保留率DRR、针入度比PRR、软化点增量SPI和黏度老化指数VAI这4个指标来评价UV326插层LDHs改性沥青的抗老化性能,其计算式为:
(1) |
(2) |
(3) |
(4) |
式中:、分别为老化前、老化后沥青的延度;、分别为老化前、老化后沥青的针入度;、分别为老化前、老化后沥青的软化点;、分别为老化前、老化后沥青的黏度.
PRR与DRR越大,SPI与VAI越小,表明沥青的老化程度越

图9 沥青的抗老化性能
Fig.9 Anti‑aging performances of asphalts
根据FTIR光谱,计算了沥青的亚砜基指数SI和羰基指数C
(5) |
(6) |
式中:分别为亚砜基峰面积、羰基峰区面积;为600~2 000 c
老化后改性沥青的FTIR光谱见

图10 老化后改性沥青FTIR光谱
Fig.10 FTIR spectra of modified asphalt after UV aging
Asphalt | Absorption peak area | CI | SI | ||
---|---|---|---|---|---|
A | A | A | |||
UVOA | 3 514.488 | 50.363 | 202.798 | 0.014 | 0.058 |
UVRLA1 | 3 529.097 | 20.257 | 139.287 | 0.006 | 0.042 |
UVRLA3 | 3 577.094 | 31.929 | 273.512 | 0.009 | 0.076 |
UVRLA5 | 3 689.912 | 23.529 | 302.767 | 0.006 | 0.082 |
UVILA1 | 2 524.737 | 9.648 | 86.697 | 0.004 | 0.034 |
UVILA3 | 2 896.905 | 12.139 | 118.786 | 0.004 | 0.041 |
UVILA5 | 3 484.299 | 61.376 | 148.192 | 0.018 | 0.043 |
(1)插层使UV326嵌入LDHs的层间,改善了复合UV326/LDHs在沥青中的团聚.掺入复合UV326/LDHs及 UV326插层LDHs后,其对沥青的紫外光吸收能力增强.
(2)改性剂掺量为1%时,复合UV326/LDHs及UV326插层LDHs对沥青的基本物理性能起到增强效果,且UV326插层LDHs减少了改性剂掺量增加所带来的不利影响.
(3)添加较低掺量的复合UV326/LDHs与UV326插层LDHs均可显著提高沥青弹性性能与抗疲劳性能,且改性剂掺量增加后复合UV326/LDHs对沥青弹性能与疲劳性能表现出劣化效果,相较而言,UV326插层LDHs对沥青弹性性能与疲劳稳定性的劣化影响更小.
(4)当改性剂掺量低于3%时,复合UV326/LDHs及UV326插层LDHs均能提高沥青的抗紫外老化性能,其中UV326插层LDHs改性沥青的抗紫外老化性更优;改性剂掺量超过3%后,复合UV326/LDHs劣化了沥青的抗紫外老化性能,相较而言,UV326插层LDHs对沥青抗紫外老化性能的劣化影响更小.
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