Experimental study of fibers in stabilizing and reinforcing asphalt binder

This investigation examines fibers’ physical properties, reinforcing effects and mechanisms for stabilizing and reinforcing asphalt binder. Laboratory tests of water absorption, mesh-basket draindown, and oven heating were designed and performed on five fiber types (two polyesters, one polyacrylonitrile, one lignin and one asbestos), to evaluate their wettability, asphalt absorption and stabilization, and thermostability, respectively. The cone sink experiment was designed to study fiber modified asphalt’s resistance to flow, and the standard dynamic shear rheometer test was conducted to evaluate fiber modified asphalt’s rheological properties and rutting resistance. Fibers’ microstructures and spatial network formed in asphalt binder were observed using Scanning Electron Microscopy (SEM). Results indicate that fibers can effectively improve asphalt binder’s resistance to rutting and flow, and dynamic shear modulus. Fiber reinforces asphalt matrix through its functions of spatial networking, adhesion and stabilization of asphalt binder. Polyester and polyacrylonitrile fibers seem to have greater network effect than the lignin and asbestos fibers, and their antenna features at fibers’ ends further strengthens this effect. The lignin fiber has the highest water absorption while lowest thermostability. The lignin and asbestos fibers pose greater effects of asphalt absorption and stabilization than do polymer fibers.     

线形和星形聚L-丙交酯大分子单体的合成

以辛酸亚锡为催化剂,分别以聚乙二醇、甲基丙烯酸羟乙酯、三羟甲基丙烷、季戊四醇、甘露醇和山梨醇等和L-丙交酯反应,得到末端为羟基的线形和星形聚L-丙交酯。通过和甲基丙烯酰氯反应,在上述线形和星形聚L-丙交酯成功引入双键,得到了相应的反应性大分子单体,其双键的存在经红外谱图和高锰酸钾试验得到证实。通过在过氧化二苯甲酰引发下的热交联,研究了上述大分子单体的反应性,发现端基数对交联产物的性质有一定影响。溶解试验、凝胶含量测定和热重分析表明,端基数目较多的大分子单体的交联产物有较高的凝胶含量,交联密度较大,热性能较好。     

星状支化PS的合成与表征

利用原子转移自由基聚合方法,以α-溴代苯乙烷为引发剂,CuBr／2,2'-联二吡啶作为催化体系,合成星状支化聚苯乙烯(PS)。引发二苯甲烷双马来酰亚胺／苯乙烯电荷转移络合物体系就地优先生成多官能团引发剂,再引发苯乙烯聚合。采用核磁共振、凝胶渗透色谱、多角度激光散射和特性黏数等分析方法对聚合过程、聚合物结构、聚合物相对分子质量及其分布进行分析与表征。由多角度激光散射法测定的绝对重均分子量是由凝胶渗透色谱测定的4倍左右,相同相对分子质量的线型PS的特性黏数是星状PS的20倍,证实聚合产物确实具有支化结构。     

Functionalized star-shaped polymers having PEO and/or polyglycidyl arms and their properties

The introduction of methacrylic, carboxylic and phosphate functional groups on the core and at the end of the poly(ethylene oxide) (PEO) arms in the PEO star-shaped polymers is described. In the polyglycidol (PGL) star-shaped polymers phosphate groups were attached to the PGL arms as side groups. Polymers were characterized by NMR and SEC analysis with triple detection. The conversion of the unsubstituted star-shaped polymers into functionalized has been confirmed by ¹H and ¹³C NMR spectra. The influence of the length of arms, their structure and the presence of functional groups on melting (T_m) and crystallization (T_c) temperatures and the degree of crystallinity (X_c) by differential scanning calorimetry (DSC) has been studied.     

Phase equilibrium in solutions of star-shaped macromolecules: an improved Okada-Numasawa model

The two-region Okada-Numasawa model for solutions of star-shaped polymers has been improved by means of a change in the integration order and introduction of a concentration-dependent and molar-mass-dependent Flory-Huggins interaction parameter (the second and third approximations of the Flory-Huggins theory). To overcome calculation difficulties, a special algorithm for computing coexistence curves of polymeric systems with an UCST has been used. The agreement between the experimental and calculated coexistence curves for the star-shaped polystyrene (PS)-cyclohexane system has been improved: the difference between T_cs is ∼0.33 K against ∼12 K as given by the original model.     

星形多臂三嵌段聚合物h-PCMS-g-PMMA-b-PBMA的合成及表征

通过对氯甲基苯乙烯(CMS)自引发ATRP技术,制备了准球形聚对氯甲基苯乙烯(h-PCMS),再以h-PCMS作为大分子引发剂,通过连续两步ATRP聚合,合成了星形多臂共聚物h-PCMS_(2700)-g-PMMA_(20000)-b-PBMA_(30000)(下标为分子量),分子量分布为2. 0。采用IR、GPC、¹H NMR及DSC等技术对聚合物的结构和性能进行确认。1H NMR定量分析证明,h-PCMS中的苄基氯能够进一步引发单体MMA进行接枝聚合,而次苄基氯由于空间位阻较大不能进一步引发MMA的接枝反应。在每一个h-PCMS表面,有接近1/3的苄基氯参与反应,平均接枝臂数为4。     

线型及星形端羟基聚丁二烯的合成与表征

以叔丁基二甲基硅氧基丙基锂为引发剂,丁二烯为单体,环己烷为溶剂,甲基三氯硅烷为偶联剂,采用活性负离子聚合法合成了线型端羟基聚丁二烯(L-HTPB)和星形端羟基聚丁二烯(S-HTPB),并用凝胶渗透色谱和核磁共振氢谱对其结构进行了表征。结果表明,采用该方法合成的2种聚丁二烯,其1,4-结构摩尔分数均接近90.00%,L-HTPB的平均官能度接近2.00,S-HTPB的平均官能度接近3.00,与分子设计值基本相符。     

Fluorescence study of the dynamics of a star-shaped poly(?-caprolactone)s in THF: A comparison with a star-shaped poly(l-lactide)s

Molecular dynamics of 2-, 4- and 6-arm star-shaped poly(?-caprolactone)s (PCLs) functionalized with pyrene at all chain ends followed by excimer formation were investigated in THF as a solvent. Dilute solutions (10⁻⁸ to 10⁻⁶ mol L⁻¹) of these polymers revealed excimer emission due to the intramolecular cyclization, proceeding via chain end interaction. Time-resolved fluorescence measurements of star-shaped PCLs showed complex decay profiles of monomer and excimer fluorescence. An intensity rise component of decay profiles monitored in excimer region (500 nm) was observed for star-shaped polymers due to dynamic formation of excimers. Dipyrene-PCL (2-arm) also showed partial formation of static pyrene excimers as followed from measurement of excitation spectra at ambient temperature in THF. Excimer intensity of di- and four pyrene-telechelic PCLs was found to be comparable with that of di- and four pyrene-telechelic polylactide (PLA) polyesters having similar molar masses. 6-Arm PCL showed depressed excimer formation with regard to 6-arm PLA under the otherwise identical conditions contrary to the conclusion expected from the higher flexibility of the PCL chain. Eventually, molecular dynamic simulations showed that possible explanation can be related to different conformations of 6-arm PLA versus PCL stars.     

A theory of topological separation of linear and star-shaped polymers by two-dimensional chromatography

Topology influences the size of macromolecules, but polymers are usually distributed with respect to molar mass, which also results in the size distribution within a polymeric sample. Due to this fact size-exclusion chromatography (SEC) is not able to separate even moderately polydisperse polymers by topology; the same is also true for the adsorption chromatography (AC). The full separation by molar mass and topology is not possible by any single mode of chromatography. These problems can be solved by means of two-dimensional chromatography which combines SEC and AC mechanisms. A theory of interactive chromatography of linear and star-shaped ideal-chain polymers is used to analyze two-dimensional chromatographic separation of polydisperse linear and star polymers. Basing on this theory, we simulate 2D-chromatograms for model mixtures of polydisperse linear and star-shaped polymers of equal average molar mass, and demonstrate that 2D-separation of such polymers by topology is possible. A possibility to separate symmetric and very asymmetric stars by 2D-chromatography is predicted. The influence of the molar-mass heterogeneity, pore size and adsorption interaction parameter on the 2D chromatographic pattern is analysed, and the conditions for a good separation of linear and star polymers are formulated. The theoretical results are in a qualitative agreement with the experimental data, which have been reported previously by Gerber and Radke.     

Synthesis, characterization and thermal properties of hexaarmed star-shaped poly(ε-caprolactone)-b-poly(d,l-lactide-co-glycolide) initiated with hydroxyl-terminated cyclotriphosphazene

Hexakis[p-(hydroxymethyl)phenoxy]cyclotriphosphazene was prepared by the reaction of hexachlorocycltriphosphaneze with the sodium salt of 4-hydroxybenzaldehyde and subsequent reduction of aldehyde groups to alcohol groups by using sodium borohydride. Hexaarmed star-shaped hydroxyl-terminated poly(ε-caprolactone) (PCL) were successfully synthesized via ring-opening polymerization of ε-caprolactone (CL) with the above hydroxyl-terminated cyclotriphosphazene initiator and stannous octoate catalyst in bulk. The number-average molecular weight of PCL linearly increased with the molar ratio of monomer to initiator. The star-shaped PCL with hydroxy end groups could be used as a macroinitiator for block copolymerization with d,l-lactide (d,l-LA) and glycolide (GA) using stannous octoate catalyst. IR, ¹H NMR and GPC analysis showed the star-block copolymers were successfully synthesized and the molecular weights and the unit composition of the star-shaped block copolymers were controlled by the molar ratios of d,l-LA and GA monomers to CL. The copolymer presented a two-phase structure, namely, PCL crystalline and d,l-LAGA amorphous domains, which made the copolymer different from linear PCL and star-shaped PCL in crystallinity and thermal behaviors.     

Synthesis and characterization of polyethylene-based ionomer nanocomposites

A solvent-free reaction of polyethylene-g-maleic anhydride with a tertiary amino alcohol is used to prepare an ammonium carboxylate polyampholyte (PE-g-PA), whose structure is characterized through spectroscopic comparisons to an appropriate model compound. The introduction of ionic functionality results in substantial increases in melt elasticity and viscosity, as well as a demonstrably improved ability to exfoliate onium ion-exchanged montmorillonite clay (NR₄⁺-MM) and to disperse nanosilica (SiO₂). Physical and rheological analysis of these nanocomposites suggest that in spite of its relatively small surface area and its capacity to engage only in ion-dipole interactions with PE-g-PA, nanosilica provides a better balance of viscoelastic and mechanical properties when compared with onium-ion exchanged montmorillonite.     

支化聚合物的合成及表征

支化聚合物由于其独特的结构和性能以及可实现规模化生产的特点,已迅速成为一类重要的和具有广阔应用潜力的高分子材料。本文综述了近年来制备支化聚合物常用的合成方法：主链引发法、主链-支链偶联法以及单体-大分子单体共聚法;介绍了表征支化聚合物支化度的方法：红外光谱法、核磁共振法、差热分析法、GPC和自动粘度计联用法,并评价了各种方法的优缺点,目的在于加深人们对该领域的了解,从而促进该领域的快速发展。     

Chemical characterization of oil-based asphalt release agents and their emissions

Four commercial asphalt release agents were chemically characterized using different analytical methods. Functional groups and molecular weight distributions were determined by fourier transform infrared spectroscopy-attenuated total reflectance (FTIR-ATR), gel permeation chromatography (GPC) and mass spectrometry (MS). General compositions of the agents were obtained as petroleum hydrocarbons, fatty acid methyl esters (FAMEs), fatty acids and glycerides using gas chromatography-mass spectrometry (GC-MS) and MS probe inlet method. The contents of health related analytes, such as aromatic hydrocarbons and polycyclic aromatic hydrocarbons (PAHs), were determined. Asphalt release agents emission was investigated using thermogravimetric analysis (TGA) and headspace solid-phase microextraction (HS-SPME). The emission proneness as well as emission level of aromatic hydrocarbons from these agents were compared. The results obtained were used for ranking the agents with regard to health hazards.     

Synthesis and characterization of four-armed star mesogen-jacketed liquid crystal polymer

The synthesis of four-armed star mesogen-jacketed liquid crystal polymer was achieved by atom transfer radical polymerization in chlorobenzene solution using pentaerythritol terakis(2-bromoisobutyrate) (PT-Br) as an initiator and CuBr/sparteine complex as a catalyst. The results show that the number average molecular weigh is creased linearly vs. monomer conversion, and that the polydispersities were quite narrow (<1.19), which is the character of controlled polymerization. The structure was experimentally confirmed by ¹H NMR. The liquid-crystalline behavior of the four-armed star polymer was studied using DSC and POM. Only the polymer with a M_n,GPC beyond 3.68×10⁴ g/mol formed a liquid crystalline phase which was quite stable with a high clearing point.     

Synthesis and characterization of well-defined comb-like branched polymers

Well-defined comb-like branched polymers having one branch in each repeating unit have been successfully synthesized by the coupling reaction of living polystyrene (PS) and polyisoprene (PI) anions with 1, 1-diphenylethenyl (DPE) groups along PS backbone prepared via atom transfer radical polymerization (ATRP) of 4-vinylbenzyloxy benzophenone (Sc) followed by Wittig reaction. The resulting comb-like branched polymers were characterized by IR, ¹H-NMR, gel permeation chromatography (GPC) and static light scattering (SLS) in detail. The effect of living chains and DPE group molar ratio on grafting efficiency was discussed. The results show the coupling reaction of living chains and DPE groups was highly effective, and the coupling efficiency can be controlled via the feed molar ratios of living chains and DPE groups. Moreover, the effect of molecular weights of backbone (PSe) and PSLi or PILi on grafting efficiency was also discussed. The results show that when excess living polymers were used, the almost quantitative grafting efficiency could be achieved. __________ Translated from Acta Polymerica Sinica (China), 2007, (3): 203–208 [译自: 高分子学报]     

Synthesis and characterization of well-defined comb-like branched polymers

Well-defined comb-like branched polymers having one branch in each repeating unit have been successfully synthesized by the coupling reaction of living polystyrene (PS) and polyisoprene (PI) anions with 1, 1-diphenylethenyl (DPE) groups along PS backbone prepared via atom transfer radical polymerization (ATRP) of 4-vinylbenzyloxy benzophenone (Sc) followed by Wittig reaction. The resulting comb-like branched polymers were characterized by IR, ¹H-NMR, gel permeation chromatography (GPC) and static light scattering (SLS) in detail. The effect of living chains and DPE group molar ratio on grafting efficiency was discussed. The results show the coupling reaction of living chains and DPE groups was highly effective, and the coupling efficiency can be controlled via the feed molar ratios of living chains and DPE groups. Moreover, the effect of molecular weights of backbone (PSe) and PSLi or PILi on grafting efficiency was also discussed. The results show that when excess living polymers were used, the almost quantitative grafting efficiency could be achieved.     

羧基丁苯胶乳的研究与应用进展

介绍了羧基丁苯胶乳的分类以及相关的合成方法,着重介绍了羧基丁苯胶乳的乳液聚合方法,以及国内外的相关研究进展;并对羧基丁苯胶乳的改性进行了相关慨述,简要介绍了羧基丁笨胶乳的应用。     

改性沥青用丁苯胶乳粉末化制备及应用

以丁二烯和苯乙烯为原料，采用高低温复合工艺制备了高固含量(60%)丁苯橡胶乳液，后经凝聚法制备出粒径分布均匀(＜1mm)的粉末丁苯橡胶(PSBR)，探讨了凝聚原理，并优化了粉末丁苯橡胶的制备工艺。通过偏光显微镜研究了粉末丁苯橡胶形成阶段的形貌变化。结果表明，凝聚阶段的絮凝剂、凝聚剂和隔离剂对PSBR形貌影响最大。复配隔离剂(硬脂酸钠、油酸钠和硅油)的隔离效果最好，使用氯化钠为絮凝剂〔添加量为1.3%（以胶乳质量为基准，下同）〕，硫酸镁为凝聚剂（添加量为2.5%）时，丁苯胶乳成粉效果最佳，呈均匀粒径的粉末状橡胶。使用PSBR改性70#基质沥青，PSBR添加量为1.0%（以沥青的质量为基准，下同）时，改性沥青的软化点由70#基质沥青的47.6℃提高到51.8℃，5℃延度提高到100cm以上，优于目前丁苯橡胶(SBR)胶粉改性沥青。