Liquid-liquid phase separation in blends of a linear low-density polyethylene with a low-density polyethylene

A linear low-density butene copolymer, of overall branch content 3 mol %, has been blended with a low-density polyethylene. The low-density polyethylene has an overall branch content of 5 mol %, including both long and short branches. The two materials were blended in a wide range of compositions and the phase behavior investigated using indirect experimental methods, the examination of quenched blends by differential scanning calorimetry, and transmission electron microscopy. After quenching from temperatures up to 170°C, blends, of almost all compositions, show two crystal populations, separated on a micron scale. It is argued that this implies that the blends were phase separated in the melt before quenching. This behavior shows good agreement with predictions based on previous extensive studies of binary and ternary blends of linear with lightly branched polyethylenes. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 65: 1921–1931, 1997     

影响低密度聚乙烯光接枝的因素

研究了空气气氛中以二苯甲酮为光敏剂时影响低密度聚乙烯（LDPE）光接枝的工艺因素。结果表明：随光照时间的延长、反应温度的升高、紫外光光强的增加，LDPE的有效接枝率增加；与丙烯酰胺单体相比，LDPE接枝丙烯酸的有效接枝率高，当单体浓度为2mol/L时，有效接枝率达极大值。光接枝LDPE对水的接触角随有效接枝率的增加而降低，当接枝率达一定值时，接触角不再随接枝率的变化而变化。     

Effects of polyphosphoric acid (PPA), styrene-butadiene-styrene (SBS), or rock asphalt on the performance of desulfurized rubber modified asphalt

To improve the performance of desulfurized rubber modified asphalt (DRMA), especially its high-temperature performance, three modifiers (including polyphosphoric acid [PPA], styrene-butadiene-styrene [SBS], and rock asphalt) were selected to modify DRMA respectively. The conventional performance, rheological properties, chemical composition, and thermal decomposition were characterized to analyze the performance and modification mechanism of DRMA and its composites. Test results show that, the addition of PPA, SBS, and rock asphalt can all improve the high temperature of DRMA, among which the desulfurized rubber/rock asphalt compound modified asphalt (DRMA-ROCK) has the best high-temperature performance; however, its construction workability, storage stability, and low-temperature performance are poor. In contrast, desulfurized rubber/PPA compound modified asphalt (DRMA-PPA) not only has better high-temperature performance, but also has excellent low-temperature performance, storage stability, and fatigue performance. Fourier infrared spectroscopy (FTIR) test confirms that the modification process of DRMA by these modifiers is chemical modification, and the characteristic peak indexes obtained from FTIR also prove that DRMA-ROCK has better high-temperature performance but poor construction workability from the microscopic point of view. Furthermore, thermogravimetric analysis-differential scanning calorimetry test shows that the addition of rock asphalt improves the thermal stability of DRMA, while PPA and SBS decrease its thermal stability. From the above results, it can be concluded that DRMA-PPA has excellent comprehensive properties.     

胶粉改性沥青的流变特性及改性机理

研究了胶粉改性沥青(CRMA)母料的流变特性,考察了混合时间及混合温度对CRMA母料流变特性的影响,提出并验证了胶粉对沥青改性的"力化学"机理。结果表明,与基质沥青相比,CRMA母料的表观黏度较高,黏流活化能与非牛顿指数较低,加入胶粉显著降低了沥青流变特性对剪切速率和温度变化的敏感性;提高混合温度与延长混合时间对CRMA母料流变特性的影响较大,最佳的混合时间为2h;胶粉与沥青混合过程中,混合体系的温度和胶粉的降解度随着混合时间的延长而增大,且在混合时间为2h时,80%以上的胶粉已发生降解;改性机理符合"力化学"原理。     

Development of novel elastomeric blends containing natural rubber and ultra-low-density polyethylene

This study sought to develop novel elastomeric compounds using natural rubber (NR) and ultra-low-density polyethylene (ULDPE). Blends were prepared by means of a two-roll mill for three ratios (70/30, 60/40, and 50/50 NR/ULDPE). Conventional vulcanization was performed in a compression mold. The physical and mechanical properties of the blend were determined according to ASTM standards. The results were compared with those obtained from NR blended with styrene-butadiene rubber (SBR). The morphological examinations with scanning electron microscopy indicated that ULDPE was compatible with NR; thus, the addition of a compatibilizer was not necessary. The cocontinuous phase was dominant in the NR/ULDPE blend containing 50 and 60 wt % NR. The tensile properties, tear resistance, and aging resistance of the NR/ULDPE blends were found to be superior to those of NR/SBR blends. On the other hand, the abrasion and flex cracking resistances of the NR/ULDPE blend were inferior to those exhibited by SBR blends but the Mooney viscosity and resilience of both blends fell in the same range. However, the addition of dicumyl peroxide appeared to have caused crosslinking of the ULDPE phase in the blend, which in turn increased the tensile properties and abrasion and aging resistance. The properties of the tertiary NR/SBR/ULDPE blend were investigated as well. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 650–660, 2001     

氯化聚乙烯橡胶自由发泡性能的研究

试验研究氢氧化铝、滑石粉和三氧化二锑的用量对氯化聚乙烯橡胶(CM)自由发泡材料的泡孔结构、密度和阻燃性能的影响。结果表明:随着氢氧化铝或滑石粉填料用量的增大,发泡CM的密度增大,泡孔尺寸变小,均匀性变差,发泡体的氧指数随填料用量增大而不断增大,阻燃性能得到提高。三氧化二锑对CM发泡材料泡孔结构及密度影响不大,但在氢氧化铝用量为20份时,少量三氧化二锑能显著提高材料的氧指数。     

Physical and rheological characteristics of liquid natural rubber modified bitumen

Polymer modification of commercially available bitumen has been attempted by the incorporation of liquid natural rubber (LNR) of medium viscosity. Both soft and blown bitumens have been studied. Physical and rheological characteristics of the samples were investigated. Improvement in physical properties such as shear strength and ductility in the case of blown bitumen and resistance to flow in the case of soft bitumen were observed. It was also found that as a result of addition of LNR, the activation energy of flow increases in the case of soft bitumen and decreases in blown bitumen. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 68:53–61, 1998     

Photografting of methacrylic acid on low-density polyethylene film in presence of polyfunctional monomers

Photografting (λ > 300 nm) of methacrylic acid (MAA) on low-density polyethylene (PE) film (thickness = 30 and 60 μm), on which xanthone photoinitiator was coated earlier, was investigated at 60°C in the presence of polyfunctional monomers such as N,N′-methylenebisacrylamide (MBAAm) and trimethylol propane triacrylate (TMPTA). Addition of the polyfunctional monomers (0.01 and 0.1 wt %) to the grafting system largely accelerated the photografting, and the magnitude of the enhancement was larger for TMPTA than MBAAm. MBAAm component was incorporated into PE substrate and/or MAA-grafted chains through the grafting reaction. Double bonds of the introduced polyfunctional component seemed to act as a new site for the grafting initiation, leading to the promoted grafting. The polyfunctional monomer did not affect distribution of the grafted chains in the cross section of the resultant MAA-grafted film, which was measured by electron probe microanalysis. Wettability of the MAA-grafted PE film was not influenced by the addition of MBAAm, but water absorbency was reduced by using a higher concentration of MBAAm. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 63: 1635–1641, 1997     

Crumb tire rubber and polyethylene mutually stabilized in asphalt by screw extrusion

In order to put recycled rubber and plastics into practical use for asphalt's modification, the polyethylene (PE)/crumb tire rubber (CTR) blends were blended to prevent them from phase separation in asphalt during hot storage. The effect of screw extrusion on storage stability, morphology, and thermal properties of modified asphalt were investigated. The results showed that the storage stability of PE/CTR modified asphalt was significantly improved after screw extrusion in the presence of a compatibilizer. The extruded PE and CTR were more finely and uniformly dispersed in the asphalt. The rheological properties of modified asphalts were improved at both higher and lower temperature's range. The density discrepancy between asphalt and the extruded PE/CTR particles was neutralized by the combination between PE and CTR. The interactions among PE, CTR and asphalt were improved by the compatibilizer. Both the reduction of density difference and the enhanced interactions are critical to obtain a stable modified asphalt system. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 41189.     

废旧胶粉改性沥青抗老化性能及效益分析

以辽河沥青为基质沥青,以废旧胶粉为改性剂,以糠醛抽出油为调合剂,可制备改性沥青。采用失重系数法、针入度比法考察2种沥青的抗老化性能。结果表明,与基质沥青相比,废旧胶粉改性沥青具有较好的抗老化性能。通过经济效益和社会效益分析,证明用废旧橡胶粉对沥青进行改性,既减少了废旧橡胶对环境的污染,又降低了改性沥青的生产成本。     

Mechanical properties and blend compatibility of natural rubber –chlorosulfonated polyethylene blends

Natural rubber (NR) was blended with chlorosulfonated polyethylene (CSM) with various formulation and blend ratios (NR/CSM: 80/20 –20/80, wt/wt). Rubber blends were prepared by using a two‐roll mill and vulcanized in a compression mold to obtain the 2 mm‐thick sheets. Tensile properties, tear resistance, thermal aging resistance, ozone resistance, and oil resistance were determined according to ASTM. Compatible NR/CSM blends are derived from certain blends containing 20–30% CSM without adding any compatibilizing agent. Tensile and tear strength of NR‐rich blends for certain formulations show positive deviation from the rule of mixture. Thermal aging resistance depends on formulation and blend ratio, while ozone and oil resistance of the blends increase with CSM content. Homogenizing agents used were Stuktol®60NS and Epoxyprene®25. Stuktol®60NS tends to decrease the mechanical properties of the blends and shows no significant effect on blend morphology. Addition of 5–10 phr of epoxidized natural rubber (ENR, Epoxyprene® 25) increases tensile strength, thermal aging resistance, and ozone resistance of the blends. It is found that ENR acts as a compatibilizer of the NR/CSM blends by decreasing both CSM particle size diameter and α transition temperature of CSM. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 127–140, 2006     

Thermoplastic vulcanizate nanocomposites based on polyethylene/reclaimed rubber: A correlation between carbon nanotube dispersion state and electrical percolation threshold

A three-step melt blending process was utilized to produce linear low-density polyethylene (LLDPE)/reclaimed rubber (RR)/carbon nanotube (CNT) nanocomposites in the presence of maleic anhydride grafted polyethylene as a compatibilizer. The effect of LLDPE/RR ratio and CNT content on the morphological, thermal, mechanical, and rheological behavior of these dynamically vulcanized LLDPE/RR nanocomposites were investigated. The morphological study showed that the RR was dispersed in the LLDPE matrix, and CNT addition led to an improved morphology as smaller RR sizes inside LLDPE were observed. The mechanical results revealed that increasing the RR content decreased the hardness, modulus of elasticity, and elongation at break while CNT improved the tensile properties and other mechanical properties. The differential scanning calorimeter analysis showed that the CNT improved the LLDPE crystallization by acting as nucleation agents. Dynamic mechanical analysis showed higher storage modulus and lower loss factor as compared to the neat blend due to mobility restrictions of the polymer chains induced by the presence of CNT. For the conditions studied, the electrical percolation threshold was found to occur at a very low CNT concentration (about 1 wt %) compared to the literature because of the specific structure produced leading to CNT residing in the LLDPE matrix and at the interface between both polymeric phases. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47795.     

Measurement of solubility and diffusion coefficients of ethylene in solid and molten low-density polyethylene with different melt indices

The diffusion behavior of ethylene in polyethylene is of great importance for the polymerization and degassing of polyethylene (PE) industry. Based on the gravimetric sorption and desorption measurement approach, an intelligent gravimetric analyzer is applied to obtain the solubility and diffusion coefficients of ethylene in solid low-density PE (LDPE) with different melt indices at 30°C to 70°C, 0 to 4 atm and in molten LDPE at 160°C to 230°C, 0 to 4 atm, respectively. Results indicate that both the solubility and diffusion coefficients of ethylene in solid LDPE are smaller than those in molten LDPE, while the dissolution enthalpy and diffusion activation energy of ethylene in solid LDPE are higher. In addition, one- and two-dimensional diffusion models are built and the effects of particle size, polymer properties, and operation conditions are systematically investigated on the diffusion behaviors of ethylene in solid and molten LDPE.     

Rheological properties of glass bead-filled low-density polyethylene composite melts in capillary extrusion

The melt flow of glass bead-filled low-density polyethylene composites in extrusion have been observed by using a capillary rheometer to investigate the effects of temperature, shear rate, and filler content on the rheological properties of the melts. The results show that the melt shear flow obeys a power law, and the dependence of the apparent shear viscosity, η_app, on temperature is in accord with an Arrhenius equation. At the same temperature and shear rate, η_app increases slightly with increasing the volume fraction of glass beads, but the flow behavior index decreases with increasing filler content. In addition, the first normal stress difference of the melts linearly increases with increasing wall shear stress. Good agreement is shown with the N₁ calculated with the equation presented in this article and the pressured data from the sample melts. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 1451–1456, 1999     

几种茂金属线性低密度聚乙烯的结构与性能研究

采用红外光谱(IR)、凝胶渗透色谱(GPC)、差示扫描量热分析(DSC)和热失重分析(TGA)等方法分析了传统线性低密度聚乙烯(LLDPE1和LLDPE2)、茂金属线性低密度聚乙烯(m-LLDPE)和茂金属聚乙烯(m-PE)在结构上、相对分子质量分布上、结晶性能和热稳定性上的差异,并测试了其流动性能和拉伸性能。研究结果表明,m-LLDPE与其它产品相比在结构上存在着差异,其具有不同的几何构型,且相对分子质量分布较窄,而LLDPE与m-LLDPE相比则相对分子质量分布宽,且有拖尾现象;m-LLDPE的结晶性能、拉伸性能及热稳定性与传统的LLDPE相比都极其优越。     

氯化聚乙烯(CM140B)与氯丁胶(CR322)的共混改性

主要研究了CM140B与CR322的共混改性.CR322经并用CM140B后,其混炼胶的加工性、压出表面及硫化胶的耐老化性及耐油性能不断得到改善.随着共混胶中CM140B用量的增加,硫化胶的拉伸强度先减小再增加,扯断伸长率、阿克隆磨耗量、回弹性、自黏性不断减小,100%定伸应力、撕裂强度、硬度、氧指数不断增加.采用噻二唑和金属氧化物硫化CM140B和CR322的共混胶时,硫化胶的综合性能较好.     

钙土在橡胶中的应用研究

用不同改性剂及不同改性方法对钙土进行了改性实验．制备了钙土／丁苯橡胶复合材料,讨论了材料的力学性能及影响因素。添加适量的钙土．可以获得性能较好的产品,并能降低产品的成本。     

橡胶型氯化聚乙烯的并用

研究了不同橡胶型氯化聚乙烯(CM)并用时硫化体系及条件、增强体系和增塑剂对并用胶硫化行为及性能的影响.结果表明,将不同的CM并用改善了硫脲-硫黄硫化体系的硫化行为,出现了硫化平坦区.硫化温度为160℃、硫化时间为50 min时,CM并用硫化胶的拉伸强度达到14.8 MPa;将质量比为50/50的炭黑N 375与N 774用于增强CM并用胶时,其硫化胶的永久变形最小;增塑剂有助于改善CM并用硫化胶的弹性及硬度,但其用量不宜过多,以30份(质量)为好;CM并用胶的各项性能指标均可以满足制备大型橡胶制品的要求.     

废旧橡胶粉改性沥青的制备及其影响因素

采用类似湿法的加工工艺,用废旧橡胶粉改性基质沥青,研究了制备胶粉改性沥青的影响因素,根据优化的参数制备了胶粉改性沥青,并与美国废旧轮胎胶粉改性沥青标准(FHWA-SA-92-002)的指标进行了对比。结果表明,制备胶粉改性沥青的最佳工艺参数为:剪切温度约180℃,剪切转速约7 000 r/min,剪切时间约40 min,胶粉用量不超过25份以及调和油的用量不超过4份;根据最佳工艺参数制备的胶粉改性沥青,其针入度、软化点、延度和弹性恢复等指标达到了FHWA-SA-92-002的要求;与基质沥青相比,其抗低温开裂性、耐疲劳性和耐老化性能都得到了不同程度的改善。     

丁腈橡胶/聚氧乙烯共混体系对聚氧乙烯结晶性能的影响

通过溶剂浇注法制备了丁腈橡胶/聚氧乙烯(NBR/PEO)共混物,通过接触角测试、傅里叶变换红外光谱分析和差示扫描量热分析,研究了NBR和PEO相互作用对PEO结晶性能的影响。结果表明,NBR/PEO共混物的表面能和附着功分别为8.80 mJ/m2和56.90 mJ/m2,两者之间具有一定的相容性;NBR中的腈基和PEO中的醚基之间并没有相互作用,两者之间具有一定的相容性,是由非极性部分贡献;NBR/PEO共混体系中随着PEO含量的减少,PEO分子链采取旁式构象的结晶结构增多,并使PEO的结晶度和结晶熔融温度明显降低,在PEO含量为5份时,NBR/PEO共混体系中PEO结晶度和结晶熔融温度分别下降80%和10.5℃,NBR的加入明显抑制了PEO的结晶。