天然橡胶/聚乙烯共混体相容性的研究

本工作首先对橡胶/聚乙烯共混体系的相容性进行了计算,推测聚乙烯的非晶部分和橡胶间有一定的互容性,提出了橡胶和聚乙烯相互作用模型。然后用动态力学方法、有效网链密度测定、密度测定和广角X-射线衍射方法对天然橡胶分别未交联和交联的天然橡胶(NR)/低密度聚乙烯(LDPE)共混体系的相容性进行了验证。实验结果表明,LDPE非晶部分和NR之间存在一定的相互渗透。     

纳米SiO2增强NR/HDPE共混型热塑性弹性体的研究

以动态硫化法制备纳米二氧化硅(SiO2)改性天然橡胶／高密度聚乙烯(NR／HDPE)共混型热塑性弹性体。研究了纳米SiO2对NR／HDPE弹性体力学、耐热变形、耐溶剂和热塑性能的影响，并用SEM分析了弹性体的断面形貌。结果表明：纳米SiO2通过细化交联NR分散相，改善了NR与HDPE的相容性，两相界面粘结强度明显提高。当纳米SiO2质量分数为0．03时，NR／HDPE弹性体的综合性能最好。     

茂金属聚乙烯共混体系液液相分离行为

研究了茂金属催化的高密度聚乙烯 (mPEO)和传统工艺生产的低密度聚乙烯 (LDPE)共混体系液 液相分离行为 .用DSC测试了共混体系在两种聚乙烯熔点之间的等温结晶动力学 ,发现共混体系经过 15 0℃培养 ,其等温结晶速率明显增快 .在排除成核作用和共结晶的影响后 ,表明上述结果是由于聚乙烯共混体系在熔融态发生了液 液相分离引起的 .从而为聚乙烯共混体系液 液相分离的存在提供了新证据     

动,静态硫化（NR＋SBR）／PE共混体系的结构与性能

用TEM研究了(NR SBR)/PE共混体系经动、静态硫化后的形态结构及其与力学性能的关系。未硫化和静态硫化体系的形态结构与其组成有关,均以含量大的组份为连续相;对动态硫化体系,当(NR=SBR)/PE<70/30时,均以PE为连续相,其性能主要依赖于构成连续相组份的性质。 动态硫化体系的T_g值低于静态体系,随PE组份含量的增加变化不大,而静态硫化体系的T_g值则随PE含量增加向高温方向迁移。用DSC测得动态硫化体系的结晶度比静态体系的大。前者的应力-应变性能也低于后者。     

聚乙烯在天然橡胶／聚乙烯共混体系中的结晶行为

本工作主要利用DSC、x-射线衍射、小角激光光散射以及偏光显微镜等方法,对天然橡胶/低密度聚乙烯共混体系(NR/LDPE)中LDPE的晶体结构、结晶度、球晶尺寸和形态、微晶尺寸、成核过程以及结晶动力学等方面进行了研究,得到了一些有意义的结果。     

聚乙烯/超高分子量聚乙烯共混体系相行为的动态流变学研究

研究了高密度聚乙烯(HDPE)/超高分子量聚乙烯(UHMWPE)、线性低密度聚乙烯(LLDPE)/UHMWPE、低密度聚乙烯(LDPE)/UHMWPE三种共混物的动态流变性能。从弹性模量、复数粘度、特征频率和松弛时间的对数线性加和性、Cole-Cole曲线、Han曲线以及时温等效原理的分析表明LDPE/UHMWPE共混物在熔体状态是相容的,而LLDPE/UHMWPE和HDPE/UHMWPE共混物在熔体状态下发生分相过程。     

不同分子量的高密度聚乙烯与茂金属线型低密度聚乙烯的相容性

采用动态流变学测试和结晶动力学的方法研究了两种分子量的高密度聚乙烯(HDPE)与茂金属线型低密度聚乙烯(m-LLDPE)共混体系的相容性.流变学研究表明,HDPE/m-LLDPE共混物在低ω区域lgG′-lgω关系曲线偏离线性规律,在熔融态为非均相体系.DSC分析发现HDPE/m-LLDPE共混物体系中HDPE的熔点随着m-LLDPE含量的增多而逐渐下降,说明HDPE与m-LLDPE二者具有机械相容性.当HDPE在m-LLDPE的熔体中等温结晶,分子量较高的HDPE结晶速率与纯HDPE相近,m-LLDPE的含量变化对Avrami指数n的影响不大;分子量较低的HDPE指数n和半结晶时间t1/2随m-LLDPE含量的增加逐渐增大,结晶速率随着m-LLDPE含量的增加逐渐下降,表明熔融态的m-LLDPE和HDPE存在着较强的分子间相互作用,二者具有一定的相容性.     

“半稀溶液”中超高分子量聚乙烯链缠绕结构的演变行为北大核心CSCD

通过熔融共混法制备超高分子量聚乙烯/线性低密度聚乙烯(UHMWPE/LLDPE)和超高分子量聚乙烯/聚乙烯蜡(UHMWPE/PE-wax)共混物,以振荡剪切流变测试和脆断截面SEM研究不同浓度UHMWPE对共混物流变行为和材料微观形貌变化的影响,尤其是UHMWPE在共混物中达到一定浓度开始形成缠结结构时的行为变化。UHMWPE/LLDPE共混物在流变测试中相容性良好,当UHMWPE浓度大于0.84%(wt),即临界交叠浓度(孤立高分子线团逐渐靠近开始成为线团密堆积时的浓度)的4倍,频率扫描曲线在低频区显示为与频率无关的类固态凝胶行为,网络结构开始形成;时间扫描曲线表明UHMWPE的浓度在大于0.84%(wt)时储能模量逐渐增大,UHMWPE的缠结有所体现。采用分子量低于缠结分子量Me的聚乙烯蜡为基体,UHMWPE/PE-wax共混物的时间扫描在浓度0.84%(wt)(临界交叠浓度的4倍)时储能模量增加明显。通过SEM观察UHMWPE/PE-wax共混物脆断面,发现该浓度下开始出现丝状物结构,表明了缠结和网络结构的形成。     

聚乙烯尼龙共混物的PGC-MS和FT-IR联用鉴别

采用裂解气相色谱-质谱法和红外光谱法研究聚乙烯和尼龙共混物的组成;据此建立鉴别聚乙烯共混物组分的方法;红外光谱法可以准确鉴别出尼龙组分,裂解气相色谱-质谱法可以准确鉴别出聚乙烯组分以及尼龙的具体结构;二种方法结合使用,可以准确鉴别聚乙烯和尼龙共混物的组分。     

傅里叶变换红外光谱结合差示扫描量热法分析PE/PP再生料

利用傅里叶变换红外光谱(FTIR)与差示扫描量热法(DSC)相结合,鉴别原料聚乙烯(PE)、再生聚乙烯,原料聚丙烯(PP)、再生聚丙烯及聚乙烯/聚丙烯共混物。以对二甲苯为溶剂,无水乙醇为沉淀剂,应用溶解–沉淀法消除着色剂、填料等添加剂对高聚物组分的干扰。根据PE/PP共混物的红外光谱特征,分别确定719,730 cm~(–1)为PE的定量分析波数,1 165 cm~(–1)为PP的定量分析波数。聚乙烯和聚丙烯组分比例与特征波长红外吸收峰面积比有良好的线性关系,相关系数为0.998 9,测定结果的相对标准偏差为1.14%(n=5)。FTIR和DSC结合的方法具有准确度高、取样量少、检测时间短的特点,计算结果相对误差均小于6%,该方法测定的组分比例(PE与PP的质量比)为0.50～2.0。该法能满足海关快速商品定性和归类的要求。     

Microbial desulfurization of SBR ground rubber by Sphingomonas sp. and its utilization as filler in NR compounds

Microbial desulfurization of waste tyre rubber has been investigated with great efforts since 1990s, because waste rubber has created serious ecological and environmental problems. A microbial desulfurization technique for SBR ground rubber has been developed by a novel sulfur‐oxidizing bacterium Sphingomonas sp. The adaptability of Sphingomonas sp. with SBR ground rubber was tested with the amounts of SBR ground rubber varying from 0.5 to 4% g/l. The sol fraction of desulfurized SBR ground rubber increased 70%, compared with SBR ground rubber without desulfurization. Fourier transform infrared spectroscopy‐attenuated total reflectance (FTIR‐ATR) spectrum and X‐ray photoelectron spectroscopy (XPS) analysis of the desulfurized surface of vulcanized SBR flakes revealed that not only the oxidation of crosslinked S? S and S? C bonds, but also the rupture of C?C double bonds had happened to SBR vulcanizates during microbial desulfurization. The cure characteristics, such as scorch time and optimum cure time of natural rubber (NR) vulcanizates filled, were found to decrease with increasing contents of desulfurized SBR ground rubber, due to some reactive groups on its surface. NR vulcanizates filled with desulfurized SBR ground rubber had lower crosslink density and hardness, higher tensile strength and elongation at break, compared with those filled with SBR ground rubber of the same amount. Dynamic mechanical properties indicated that there were better crosslink distribution and stronger interfacial bonding between NR matrix and desulfurized SBR ground rubber. Scanning electron microscope (SEM) photographs showed that the fracture surfaces of NR vulcanizates filled with desulfurized SBR ground rubber had more smooth morphologies. Copyright © 2010 John Wiley & Sons, Ltd.     

A SAXS and swelling study of cured natural rubber/styrene–butadiene rubber blends

A small‐angle X‐ray scattering (SAXS) and swelling study of natural rubber and styrene–butadiene rubber blends (NR/SBR) is presented. To this aim, specimens of NR and SBR and blends with 75/25, 50/50, and 25/75 NR/SBR ratios (in phr) were prepared at a cure temperature of 433 K and the optimum cure time (t₁₀₀). This time was obtained from rheometer torque curves. The system of cure used in the samples was sulfur/n‐t‐butyl‐2‐benzothiazole sulfenamide. From swelling tests of the cured samples, information about the molecular weight of the network chain between chemical crosslinks was obtained. For all cured compounds, in the Lorentz plots built from SAXS scattering curves, a maximum of the scattering vector q around 0.14 Å^?1 was observed. However, the q position shows a linear‐like shift toward lower values when the SBR content in the SBR/NR blend increases. In pure NR or SBR the q values show a different tendency. The results obtained are discussed in terms of the existence of different levels of vulcanization for each single phase forming the blend and the existence of a third level of vulcanization located in the interfacial NR/SBR layer. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 2320–2327, 2009     

Effects of Sericite Modified by Macromolecular Dispersant on the Thermal,Mechanical and Electrical Properties of the NR/SBR Composites

A new hydrosoluble macromolecular dispersant and modifier, poly(ethylene glycol)-maleic anhydride-acrylic acid (PEG-MA-AA) terpolymer was synthesized via ring-opening reaction and free radical polymerization. The chemical structure of the PEG-MA-AA terpolymer was confirmed by Fourier transform infrared (FTIR) spectra and nuclear magnetic resonance spectroscopy (NMR), and its average molecular weight was determined by gel permeation chromatography (GPC). Modified sericite (MSE) was synthesized from sericite (SE) by the surface modification with PEG-MA-AA. The NR/SBR/MSE composites were prepared via the blending of the modified sericite and NR/SBR rubber. The thermal, mechanical and electrical properties of the composites were investigated by TGA, tensile test machine and high-insulation resistance meter. The results showed that the thermal stability and the mechanical and electrical insulation properties of NR/SBR/MSE composites were improved significantly. SEM also revealed that modified sericite possessed good dispersibility.     

Morphology and mechanical and viscoelastic properties of natural rubber and styrene butadiene rubber latex blends

The morphology and mechanical and viscoelastic properties of a series of blends of natural rubber (NR) and styrene butadiene rubber (SBR) latex blends were studied in the uncrosslinked and crosslinked state. The morphology of the NR/SBR blends was analyzed using a scanning electron microscope. The morphology of the blends indicated a two phase structure in which SBR is dispersed as domains in the continuous NR matrix when its content is less than 50%. A cocontinuous morphology was obtained at a 50/50 NR/SBR ratio and phase inversion was seen beyond 50% SBR when NR formed the dispersed phase. The mechanical properties of the blends were studied with special reference to the effect of the blend ratio, surface active agents, vulcanizing system, and time for prevulcanization. As the NR content and time of prevulcanization increased, the mechanical properties such as the tensile strength, modulus, elongation at break, and hardness increased. This was due to the increased degree of crosslinking that leads to the strengthening of the 3‐dimensional network. In most cases the tear strength values increased as the prevulcanization time increased. The mechanical data were compared with theoretical predictions. The effects of the blend ratio and prevulcanization on the dynamic mechanical properties of the blends were investigated at different temperatures and frequencies. All the blends showed two distinct glass‐transition temperatures, indicating that the system is immiscible. It was also found that the glass‐transition temperatures of vulcanized blends are higher than those of unvulcanized blends. The time–temperature superposition and Cole–Cole analysis were made to understand the phase behavior of the blends. The tensile and tear fracture surfaces were examined by a scanning electron microscope to gain an insight into the failure mechanism. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 2189–2211, 2000     

硼酰化钴在橡胶与镀锌钢丝粘合中的应用研究

研究硼酰化钴的用量变化对丁苯橡胶／天然橡胶与镀锌钢丝粘合的影响,通过表面分析对其粘合机理进行了研究。研究表明：硼酰化钴对丁苯橡胶／天然橡胶与镀锌钢丝粘合的粘合增强作用十分明显。硼酰化钴添加2phr左右,粘合性能最佳,同时硫化胶的物理性能得到改善。X-射线光电子能谱分析表明,粘合物镀锌钢丝界面中存在ZnO、ZnS、CoS2,说明粘合时发生了Zn的硫化反应,硼酰化钴中的钴向钢丝表面迁移,继而在锌层中扩散,提高了ZnO和ZnS晶格的缺陷浓度,这两种行为的共同作用,使橡胶与镀锌钢丝的粘合强度显著提高。     

Natural rubber nanocomposites with SiC nanoparticles and carbon nanotubes

Single-walled carbon nanotubes (SWNTs) and SiC nanoparticles were dispersed in natural rubber (NR) polymer solution and subsequently evaporated the solvent to prepare NR nanocomposites. Using this technique, nanoparticles can be better dispersed in the NR matrix. The influence of nano-fillers on the mechanical properties of the resulting nanocomposites was quantified.Mechanical test results show an increase in the initial modulus with nanoscale reinforcements for up to 50% strain compared to pure NR. The modulus and strength of natural rubber with 1.5% SiC nanoparticles appear to be superior to those of SWNTs with the same filler content. In addition to mechanical testing, these nanocomposites were studied using the SEM and Raman spectroscopy techniques in order to understand the morphology of the resulting system and the load transfer mechanism, respectively. The Raman spectrum of the SWNT/NR system is characterized by a strong band at 1595 cm⁻¹ (G mode—C-C stretching) and other two bands at 1300 cm⁻¹ (D mode-disorder induced) and 2590 cm⁻¹ (D* band). A shift of the 2590 cm⁻¹ Raman band to the lower wavenumber was observed after subjecting SWNT/NR sample to cyclic stress testing. Ageing SWNT/NR specimen in distilled water for 30 days also provided a similar result. The Raman shift in aged samples indicates internal stress transfer from the natural rubber matrix to the SWNTs implying the existence of bonding at the interface.     

The morphology and thermal properties of liquid natural rubber (LNR)-compatibilized 60/40 NR/LLDPE blends

The effects of LNR as a compatibilizer in binary blends of 60/40 NR/LLDPE have been investigated by means of differential scanning calorimetry, dynamic mechanical analysis and scanning electron microscopy. Special emphasis was given to the role of LNR in inducing interactions between NR and LLDPE. It has been observed that increasing LNR content decreases T_m and ΔH_f which are indicators of the crystalline part of the blends. The decrease reflects a reduction in the degree of crystallinity which is due to the interference in the form of NR dissolution into the LLDPE phase. The phenomenon leads to a shift in T_g of the amorphous part of LLDPE to higher temperatures as observed by DMA thermograms. The dissolution effect creates better interactions between the phases leading to improvements in the compatibility of the blends. Further confirmation was obtained through SEM examination.     

Morphology and performance of styrene butadiene rubber filled with modified graphite nanoplatelet and carbon black

In our work, effects of 2‐mercapto‐1‐methylimidazole modified graphite nanoplatelet (MMI–GN) and carbon black (CB) on static and dynamic mechanical properties of styrene butadiene rubber (SBR) composites were studied. MMI–GN is synthesized by ball‐mill process, and the result reveals that π–π interactions existed between MMI and GN. The results demonstrate that the static and dynamic mechanical performances of SBR/CB/MMI–GN composites are significantly improved over these of SBR/CB and SBR/CB/GN composites. Compared with SBR/CB, the tensile strength, tear strength, and modulus at 300% elongation of SBR/CB/MMI–GN–3 are greatly improved by 45%, 27%, and 4%, respectively. And the rolling resistance of SBR/CB/MMI–GN–3 is reduced by 3.7% with remaining almost unchanged in the wet grip property. The superiority of MMI–GN in the enhancement for the overall performance of SBR/CB composites is attributed to the well dispersion of GN throughout the SBR matrix and the enhanced interfacial interactions between GN and the SBR matrix. This work might expedite synthesis of the graphite‐based materials for enhancing rubber composites, and enlarge the potential applications of modified graphite to fabricate the high‐performance rubber composites. Copyright © 2016 John Wiley & Sons, Ltd.     

Compatibilized natural rubber/recycled ethylene-propylene-diene rubber blends by biocompatibilizer

Biocompatibilizer-based refined, bleached, deodorized palm stearin was successfully used as compatibilizer for natural rubber/recycled ethylene–propylene–diene rubber (NR/R-EPDM) blends. It seems effective in improving the state of cure, tensile properties, as well as the swelling resistance and morphology of the blends, indicating an improvement in compatibility between the NR matrix and R-EPDM rendered by biocompatibilizer. This was clearly verified by the dynamic mechanical properties of the blends. The dynamic responses obtained were clearly corresponding to the swelling result. It proves that the cross-link density plays a major role in the changes of storage modulus and degree of entanglement.     

Determination of bound rubber composition of filled SBR/BR blend compounds by analysis of the unbound rubber composition and bound rubber content

Analytical method for determination of the bound rubber composition of a filled SBR/BR blend compound was developed using measurement of the bound rubber content and microstructural analysis of the unbound rubber composition. Various filled SBR/BR blend compounds with different blend ratios were prepared using SBRs with different microstructures. This method included measurement of the bound rubber content, extraction of the unbound rubber, microstructural analysis of the unbound rubber composition, and process for determination of the bound rubber composition. Composition of the unbound rubber was analyzed using liquid proton nuclear magnetic resonance spectroscopy (H-NMR) and transmission Fourier transform infrared spectroscopy (FTIR). It was found that the analytical results using H-NMR had less experimental errors than those using transmission-FTIR. The raw SBR/BR blends were also analyzed in order to evaluate level of the experimental errors. Average SBR/BR ratios of the unbound rubbers were obtained using the 1,2- and 1,4-unit contents determined by the H-NMR analysis. The bound rubber compositions were obtained using the bound rubber contents and the average unbound rubber compositions. It was found that most of the bound rubbers had higher SBR ratios than the formulation value.