HDPE-g-PB接枝共聚物的合成及其与聚丁二烯的共混

利用~(60)Co辐照合成了HDPE与丁二烯的接枝共聚物,PE-g-PB。动态力学试验表明,它与PB较PE与PB有更好的相容性。PB含量相同时PB/PE-g-PB共混物比PB/PE共混物有较高的抗张强度和断裂伸长率。前者中两相分布较均匀,相区尺寸较小。     

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。     

HDPE／LDPE共混体系的晶性研究

用DSC和WAXD方法考察了高密度聚乙烯和低密度聚乙烯共混体系(HDPE/LDPE)的结晶性能。结果表明,在共混物中HDPE含量大于50%时,共混物只出现HDPE的熔融峰,且熔融温度随HDPE含量减小而降低;LDPE含量大于50%时,DSC图上只出现熔点介于HDPE和LDPE之间的新熔融峰。DSC和WAXD法所测结晶度均偏离共混物的线性加和值,而晶胞参数则随共混物组成变化出现最小值,表明HDPE和LDPE可以形成共晶相容体系。Raman光谱测得介晶相αb值的膨胀,支持这一观点。     

HIPS／SBS共混物的形态结构和性能

通常,高抗冲聚苯乙烯(HIPS)为多相体系,由连续聚苯乙烯(PS)相和分散的聚丁二烯(PB)颗粒组成。PB含量一般为5～15%,粒径范围为0.5～10μm,PB颗粒是交联的,同时含有接枝的PS,其内部结构由制备工艺决定。HIPS力学性能与其制备工艺、PB含量、PB分子结构、相区尺寸及内部结构密切相关。PS和PB嵌段共聚物(SBS)通常为热塑弹性体,由于PS段和PB段的不相容性而呈现微相分离的结构特征。SBS常用于与其它聚合物共混以增加后者的韧性。本工作研究了HIPS/SBS共混物的形态结构和力学性能。     

原子力-红外光谱定量分析聚1-丁烯／聚丙烯共混物的相区组成

在聚1-丁烯（PB）中混入聚丙烯（PP）能够调节前者的结晶行为，二者的共混物因此引起了人们的兴趣，其中关于两个组分的相容性目前还存在争议。本文首先建立PB／PP共混物组成的傅里叶变换红外光谱仪（FT-IR）定量分析方法，以1460和1378 cm^－1吸收峰的面积比来确定共混物中PB的质量分数，进而利用原子力-红外（AFM-IR）光谱与FT-IR光谱的一致性将其应用于AFM-IR谱的数据处理，以获得共混物中微相区的组成。研究发现PB质量分数为70%的PB／PP共混物发生了相分离，两个组分部分互溶，形成了富PB相和富PP相，分别含有78%和19%的PB。     

茂金属聚乙烯和低密度聚乙烯共混物的流变行为

研究了茂金属催化乙烯丁烯1共聚物mPE和LDPE共混物的流变行为.测定了一系列共混物的稳态剪切粘度和动态粘弹性,用改进Cross模型拟合实验数据.mPE的零切粘度η₀较小,从牛顿型转变为非牛顿型所需的剪切速率较大,转变应力较高,在挤出加工剪切速率范围内熔体粘度高,对剪切敏感性差,这是由于它有较低的重均分子量、窄的分子量分布(M_w/M_n=21)所致.对于对数加和规律,共混物η₀在mPE/LDPE为50/50和25/75时有强烈的正偏差,这是由于共混物自由体积减小所致.共混物的转变应力τ^*和非牛顿指数n随LDPE加入量增大而降低,表明共混物对剪切的敏感性提高,加工性得到改善.G'和G”的一致性说明mPE和LDPE共混是相容的.     

低密度聚乙烯/乙丙烯三元共聚(LDPE/EPO)共混体系的相容性及其结晶结构

DDV、DSC、WAXD、萃取和Raman光谱实验表明,在所有组成下,LDPE/EPO共混体系共晶相容.WAXD法测定表明,LDPE/EPO共混体系的结晶度随EPO组分含量的增加而降低,EPO未能进入LDPE晶胞中.     

聚乙烯与聚顺-1,4-丁二烯共混材料的结构与性能

聚乙烯(PE)用顺-1,4-丁二烯(PB)增韧改性以获得耐卷绕的被复线(一种野外用电话线)。采用光学显微镜、电子显微镜、X-射线衍射、光学解偏振等技术研究不同共混组成对序态结构的影响,以及序态结构与耐折性能之间的关系。结果表明,当PB由分散相开始转变成连续相以前,PB用量愈多,共混材料的耐折性能愈好。不论是线型、支化或分子量不同的PB,经用PB增韧后,其耐折性能可提高7.6—11.5倍左右。     

聚丙烯／顺丁橡胶动态硫化增韧的研究

研究了在聚丙烯(pp)与顺丁橡胶(BR)共混过程中加入橡胶硫化剂使共混体系中橡胶相动态硫化交联。研究结果表明,采用动态硫化法可提高共混物的冲击强度和拉伸强度。借助于SEM和DMA,证实了动态硫化使PP/BR共混体系具有相界面粘结良好的多相结构,改善了两相相容性。探讨了动态硫化增韧的机理。     

低密度聚乙烯/乙丙烯三元共聚(LDPE/EPO)共混体系的相容性及其结晶结构

 DDV、DSC、WAXD、萃取和Raman光谱实验表明,在所有组成下,LDPE/EPO共混体系共晶相容.WAXD法测定表明,LDPE/EPO共混体系的结晶度随EPO组分含量的增加而降低,EPO未能进入LDPE晶胞中.     

Reactive compatibilization of recycled low density polyethylene/butadiene rubber blends during dynamic vulcanization

For reactive compatibilization of the recycled LDPE with butadiene rubber (BR) an equal quantity of few couples of reactive polyethylene copolymer/reactive polybutadiene (1/1) were introduced into the corresponding phases before the dynamic vulcanization. The LDPE/BR thermoplastic dynamic vulcanizates (TDVs) produced using the poly(ethylene-co-acrylic acid), PE-AA/polybutadiene terminated with isocyanate groups, PB-NCO compatibilizing couple with different ratio of functional groups have demonstrated the best mechanical properties and have been characterized by X-Ray analysis and DMTA measurements. For all of systems studied the increasing components compatibility due to the formation of the essential interface layer have been observed. The PB-NCO modifier participates in two processes: it is co-vulcanised with BR in rubber phase and reacts in the interface with the PE-AA dissolved in LDPE. The amorphous phase of LDPE is dissolved by rubber phase, i.e. the morphology with dual phase continuity is formed that provides an improvement of mechanical characteristics of material obtained. The best combination of mechanical characteristics was obtained for LDPE(PE-AA)/BR(PB-NCO), PB-NCO=7.5 wt.% per PB, COOH/NCO=1/1. The tensile strength and an elongation at break for these blends were 3.9 MPa and 353% and for the basic non-compatibilized blend 3.2 MPa and 217%, relatively.     

Metallocene polyolefins and their blends#

Commercial copolymers of 1‐octene and ethylene: metallocene catalyzed (mLLDPE) and Ziegler‐Natta catalyzed (znLLDPE), a low density polyethylene (LDPE), and high density polyethylene (HDPE), were characterized with respect to branching, crystallization behaviour and dynamic‐mechanical properties. It was found that the crystallinity of the polymers is more influenced by the homogeneity of the short‐chain branching than by its content. The study of blends of mLLDPE and znLLDPE with LDPE and HDPE showed that the interaction between mLLDPE and LDPE is stronger than between znLLDPE and LDPE. Blends containing mLLDPE showed a composition depending improvement of the storage modulus G' which was not observed in znLLDPE/LDPE blends. The HPDE blends followed a linear mixing rule. Co‐crystallization was found mLLDPE/LDPE and partially in znLLDPE/LDPE and znLLDPE/HDPE blends, respectively.     

The compatibilization effect of ethylene/styrene interpolymer on polystyrene/polyethylene blends

In this study, ethylene/styrene interpolymer (ESI) was used as compatibilizer for the blends of polystyrene (PS) and low‐density polyethylene (LDPE). The mechanical properties including impact, tensile properties, and morphology of the blends were investigated by means of uniaxial tension, instrumented falling‐weight impact measurements, and scanning electron microscopy. Impact measurements indicated that the impact strength of the blends increases slowly with LDPE content up to 40 wt %; thereafter, it increases sharply with increasing LDPE content. The impact energy of the LDPE‐rich blends exceeded that of pure LDPE, implying that the LDPE polymer can be further toughened by the incorporation of brittle PS minor phase in the presence of ESI. Tensile tests showed that the yield strength of the PS/LDPE/ESI blends decreases considerably with increasing LDPE content. However, the elongation at break of the blends tended to increase significantly with increasing LDPE content. The compatibilization efficiency of ESI and polystyrene‐hydrogenated butadiene‐polystyrene triblock copolymers (SEBS) for PS/LDPE 50/50 was further compared. Mechanical properties show that ESI is more effective to achieve a combination of LDPE toughness and PS rigidity than SEBS. The correlation between the impact property and morphology of the ESI‐compatibilized PS/LDPE blends is discussed. The excellent tensile ductility of the LDPE‐rich blends resulted from shield yielding of the matrix. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 2136–2146, 2007     

Effects of reprocessing on polymers—Part III: Photo-oxidation of polyethylene-polypropylene blends

It is shown that blends of low density polyethylene (LDPE) and polypropylene (PP) photo-oxidise more readily than LDPE alone and there was evidence of cross-linking between the two phases. An ethylene-propylene rubber (EPDM) which improved the mechanical performance of LDPE/PP blends caused an increase in the rate of photo-degradation as measured by carbonyl formation and by loss of toughness.     

Effect of organoclay loading and electron beam irradiation on the physico‐mechanical properties of low‐density polyethylene/ethylene‐vinyl acetate blend

The influence of electron beam (EB) irradiation and organoclay (OC) loading on the properties of low‐density polyethylene (LDPE)/ethylene‐vinyl acetate (EVA) blends was investigated. The samples were subjected to the EB irradiation with the dose values of 50 and 250 kGy. X‐ray diffraction (XRD), gel content, mechanical, thermal, and electrical properties were utilized to analyze the characteristics of the LDPE/EVA blends with and without OC at different irradiation dosages. Gel content analysis showed that the OC promotes considerably the insoluble part so that the LDPE/EVA blends filled with OC become fully crosslinked at 250 kGy; possibly through the formation of further crosslinks between OC and polymer chains. The samples irradiated by EB showed enhanced mechanical properties due to the formation of three‐dimensional networks. In addition, thermogravimetric analysis indicated that combined OC loading and radiation‐induced crosslinking improved thermal stability of LDPE/EVA blends considerably. Copyright © 2011 John Wiley & Sons, Ltd.     

Morphology and mechanical properties of extruded ribbons of LDPE/PA6 blends compatibilized with an ethylene-acrylic acid copolymer

Two grades of low density polyethylene (LDPE) were blended with polyamide-6 (PA) in the 75/25 and 25/75 wt/wt ratios and shaped into ribbons with a Brabender single screw extruder. An ethylene-acrylic acid copolymer (EAA) was used in the 2 phr concentration as a compatibilizer precursor (CP). The morphology of the ribbons and its evolution during high temperature annealing were investigated by scanning electron microscopy (SEM). The results confirmed that EAA does actually behave as a reactive compatibilizer for the LDPE/PA blends. In fact, in the presence of EAA, the interfacial adhesion is improved, the dispersion of the minor phase particles is enhanced and their tendency toward fibrillation is increased, especially for the blends with the higher molar mass LDPE grade. The mechanical properties of the latter blends were found to be considerably enhanced by the addition of EAA, whereas the improvement was relatively modest for the blends with the lower molar mass LDPE. The fracture properties of double end notched samples of the ribbons prepared with the blends containing the lower molar mass LDPE grade were also studied. It was shown that, despite of the increased interfacial adhesion caused by the presence of EAA, the latter plays a measurable positive effect on the fracture properties only for the blends with LDPE as the matrix.     

Study on rheological properties and relaxational behavior of poly(dianilinephosphazene)/low-density polyethylene blends

Rheological properties and relaxational behavior of blends of low-density polyethylene (LDPE) and poly(dianilinephosphazene) (PDAP) have been investigated to check miscibility and molecular relaxations in the crystalline and amorphous phases. In the studied shear rate range, all PDAP/LDPE blends exhibited a shear thinning behavior. The experimental data were fitted using the logarithmic rule and serial model to investigate the miscibility of blends. It was found that LDPE and PDAP can achieve a certain degree of miscibility in the molten state. The dynamic mechanical α-, β- and γ-relaxation behavior obtained from dynamic mechanical thermal analysis imply that the two components in the amorphous phase were miscible. The wide-angle X-ray diffraction result showed that these two components interact with each other.     

Solid-state relaxations in linear low-density (1-octene comonomer), low-density,and high-density polyethylene blends

Extensive thermal and relaxational behavior in the blends of linear low-density polyethylene (LLDPE) (1-octene comonomer) with low-density polyethylene (LDPE) and high-density polyethylene (HDPE) have been investigated to elucidate miscibility and molecular relaxations in the crystalline and amorphous phases by using a differential scanning calorimeter (DSC) and a dynamic mechanical thermal analyzer (DMTA). In the LLDPE/LDPE blends, two distinct endotherms during melting and crystallization by DSC were observed supporting the belief that LLDPE and LDPE exclude one another during crystallization. However, the dynamic mechanical β and γ relaxations of the blends indicate that the two constituents are miscible in the amorphous phase, while LLDPE dominates α relaxation. In the LLDPE/HDPE system, there was a single composition-dependent peak during melting and crystallization, and the heat of fusion varied linearly with composition supporting the incorporation of HDPE into the LLDPE crystals. The dynamic mechanical α, β, and γ relaxations of the blends display an intermediate behavior that indicates miscibility in both the crystalline and amorphous phases. In the LDPE/HDPE blend, the melting or crystallization peaks of LDPE were strongly influenced by HDPE. The behavior of the α relaxation was dominated by HDPE, while those of β and γ relaxations were intermediate of the constituents, which were similar to those of the LLDPE/HDPE blends. © 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 35 : 1633–1642, 1997     

Étude des propriétés des mélanges pebd régénéré / pebd vierge

This study is a contribution to the valorization of recycled low-density polyéthyléne (LDPE). First the characterization of five recycled LDPE produced from wastes coming from different sources was performed. The physical properties (density, melt flow index), chemical structure (Fourier transform infra-red spectroscopy) and mechanical properties (tensile strength and hardness) were investigated. The effect of the ratio of virgin LDPE on these physical and mechanical properties was studied in the case of the blends of recycled LDPE / virgin LDPE.     

EFFECTS OF COMPATIBILIZERS ON THE MECHANICAL PROPERTIES OF LOW DENSITY POLYETHYLENE/LIGNIN BLENDS

Low density polyethylene(LDPE)/lignin blends were prepared using melt blending.Two kinds of compatibilizers, ethylene-vinylacetate(EVA) which is softer than LDPE and polyethylene grafted with maleic anhydride(PE-g-MA) which is harder than LDPE were used to improve the interfacial adhesion.Scanning electron microscope(SEM) was used to investigate the dispersion of lignin in LDPE matrix.The results showed that both of the compatibilizers could improve the interaction between the low density polyethylene an...