动态硫化EPDM／PP共混体系中PP相的结晶度及晶体结构的研究

研究了动态硫化ＥＰＤＭ／ＰＰ共混物中ＰＰ相的结晶度及晶体结构,同时讨论了制备工艺条件以共混物中ＰＰ相的结晶度和晶体结构的影响。结果表明：在动态硫化ＥＰＤＭ／ＰＰ共混物中,硫化的ＥＰＤＭ的分子键没有穿入ＰＰ的晶区,ＰＰ的结晶度随ＥＰＤＭ含量的增加而下降。提高共混温度,加入软化剂或碳黑均使共混物中ＰＰ的结晶度降低,共混时间１５ｍｉｎ时,共混物中ＰＰ相的结晶度最低,但ＰＰ的晶格不受制备工艺条件的影响。     

聚丙烯／顺丁橡胶动态硫化共混物的交联行为和结晶性能的研究

研究了聚丙烯／顺丁橡胶动态硫化共混物橡胶相的交联行为、动态硫化共混物的结晶行为和结晶结构。结果表明，顺丁橡胶的加入对ＰＰ的熔点无明显影响，但结晶度降低。动态硫共化共混物在低于熔点处另有一熔化转变。动态硫化使共混物中ＰＰ的结晶速率提高。     

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。     

PP/EPDM共混物热氧稳定性研究

通过热氧加速老化的方法研究了不同的EPDM含量和抗氧剂对聚丙烯和三元乙丙橡胶共混物(PP/EPDM)热氧稳定性的影响.通过对老化前后试样的力学性能变化分析,热失重(TG)分析和扫描电镜(SEM)分析,结果表明:在热氧加速老化的初期,PP/EPDM共混物的拉伸强度随着时间的增长呈逐渐上升的趋势;在老化中期,共混物的拉伸强度变化不大;在老化后期,共混物的拉伸强度逐渐下降.在整个老化过程中,断裂伸长率都呈逐渐下降的趋势.而随着EPDM含量的增加,相应共混物的拉伸强度和断裂伸长率的下降减缓;相应共混物的分解温度得到较大的提高;抗氧剂的加入,能进一步提高共混物的热氧稳定性.     

共混过程中EPDM/PP共混热塑弹性体的结构、形态和性能的变化

用SEM,TEM,DSC,WAXD和有效网链密度(v_e)测定,研究了共混时间长短和返炼对EPDM/PP共混物结构和性能的影响。两相分散随共混时间和返炼而更趋均匀。随共混时间,PP结晶度(x_c)先行降低然后升高,抗张强度正相反,v_e则降低x_e和v_e返炼后总是较一次共混降低。影响强度的因素主要是两相分散均匀和两相界面的相互渗透。     

PP/EPDM共混体系的辐射效应

聚丙烯和三元乙丙橡胶(EPDM)的γ辐射效应及辐射后的聚丙烯熔体流动速率的测定表明,在限定空气中聚丙烯随着辐照剂量的增加,熔体流动速率急剧下降,而三元乙丙橡胶随辐射剂量的增加,凝胶含量逐渐增加。在20kGy的剂量辐照下,凝胶含量为22．7％,加入2％的三聚异氰酸三烯丙酯,在相同的剂量辐照下,凝胶含量达到68％。在低剂量下辐照对共混物的拉伸强度影响不大,对冲击强度有很大的影响。在20kGy的剂量辐照下,加入50％EPDM的聚丙烯的缺口冲击强度由1．95kJ／m^2提高到30kJ／m^2,维卡软化温度由85．9℃提高到97．0℃。     

辐射增强PP／BR共混体系的力学性能

研究了在多官能团单体－三烯丙基异氰酸酯存在下，共混体系聚丙烯／１．４－聚丁二烯橡胶的辐射效应，用ＤＳＣ，动态粘弹谱对其进行表征。结果显示，三烯丙基异氰酸酯主要分布于聚丙烯／１．４－聚丁二烯橡胶共混物的界面自高能射线作用下，被引发参与界面反应，从而改善了共混体系的相容性，增强也界面粘接，提高了共混物的力学性能。     

应力引发官能化EPDM/HDPE及其对PA66/EPDM/HDPE 共混物相形态和力学性能的影响

通过提高双螺杆挤出机螺杆转速的方法,研究了熔融挤出过程中高剪切应力对马来酸酐(MAH)官能化三元乙丙橡胶(EPDM)与高密度聚乙烯(HDPE)共混物的接枝率、熔体流动速率及凝胶含量的影响.随着双螺杆挤出机螺杆转速的增加,强烈的机械剪切应力引发EPDM/HDPE共混物大分子链的断链反应形成大分子自由基,从而引发接枝反应制...     

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。     

Study on Dynamic Vulcanized EPDM/PP Thermoplastic Elastomer

Based upon the THE,HAAK RHEOCORD 90 and Wx-ray observation,a study was made on the structure and property of ethylene-propylene-ethlidene norborene (EPDM)/polyprolene (PP) blending systems ,and the experimental results were fully explained. (1) The effect of Mooney viscosity (ML)of EPDM、 melt flow rate(MFR) of peroxide(DCP) and mixing steps on mechanical properties of EPDM/PP blends was studied. The results showed that the mechanical and process properties of EPDM?PP thermoplastic elastomers were better using EPDM with the ML of 60 and PP with MFR of 7.5g/10min as matrix,DCP with the content of 1.2 per cent with the help of twostep curing process at the temperature of 170-175 ℃.     

Dynamically Photocrosslinking of Polypropylene／EPDM Blends as a Thermoplastic Elastomer

The mechanical properties and the crystal morphological structures of the dynamically photocrosslinked polypropylene (PP)/ethylene-propylene-diene terpolymer (EPDM) blends have been studied by means of mechanical tests, wide-angle X-ray diffraction(WAXD), and differential scanning calorimetry(DSC). The dynamically photocrosslinking of the PP/EPDM blends can improve the mechanical properties considerably, especially the notched Izod impact strength at low temperatures. The data obtained from the mechanical tests show that the notched Izod impact strength of the dynamically photocrosslinked sample with 30% EPDM at -20℃ is about six times that of the uncrosslinked sample with the same EPDM component. The results from the gel content, the results of WAXD, and the DSC measurements reveal the enhanced mechanism of the impact strength for the dynamically photocrosslinked PP/EPDM blends as follows: (1) There exists the crosslinking of the EPDM phase in the photocrosslinked PP/EPDM blends ; (2) The β-type crystal structureof PP is formed and the content of α-type crystal decreases with increasing the EPDM component; (3) The graft copolymer of PP-g-EPDM is formed at the interface between the PP and EPDM components. All the above changes of the crystal morphological structures are favorable for increasing the compatibility and enhancing the toughness of the PP/EPDM blends at low temperatures.     

Study of the Impact Resistance of Physically and Dynamically Vulcanized Mixtures of PP/EPDM

Physically and dynamically vulcanized (TPV) mixtures of polypropylene (PP) and ethylene propylene diene terpolymer (EPDM) are prepared by extrusion in order to improve the impact resistance of PP. To enhance the chemical compatibility and provide better interaction between the PP and EPDM in the physical mixtures, both polymers are modified with maleic anhydride (MAH) in solution using xylene as solvent and dicumyl peroxide (DCP) as initiator. The qualitative and quantitative determination of the degree of grafting is study by Fourier Transform Infrared Spectroscopy (FTIR) and varying the amount of DCP and/or amount of MAH in order to determine the optimum amounts to obtain the highest degree of grafting. The effect of the relation of PP/EPDM, the amount of reinforcement filler and mix rate are studied for modified polymer mixtures (PP-g-MAH/EPDM-g-MAH). For the TPV of PP/EPDM the effects of amount and triallylisocyanurate (TAC) as coupling agent in presence of different amounts of DCP are studied. The physical mixtures of modified polymers prepared with a PP/EPDM ratio of 80/20 and the TPVs blends prepared with a PP/EPDM ratio of 70/30 and containing 15% filler at 60 rpm show the highest impact resistance. The impact resistance, melt flow index and hardness of the different mixtures are measured to determine their possible applications to prepare front panels and bumpers for automobiles by injection molding.     

Design of PP/EPDM/NBR TPVs with tunable mechanical properties via regulating the core-shell structure

In this work, polypropylene (PP)/ethylene-propylene-diene monomer (EPDM)/butadiene acrylonitrile rubber (NBR) TPVs with different EPDM/NBR ratios were prepared by the core-shell dynamic vulcanization. The relationship between the core-shell structure and mechanical properties of the TPVs were thoroughly investigated. The formation of core-shell structure by adding NBR is conducive to the mechanical properties of the TPVs. The ratio of EPDM to NBR has an important effect on the structure and performances of the final products, and there is a critical ratio for this effect change. Transmission electron microscope (TEM), tensile test, reprocessing test, ageing test, rheological behavior test and stress relaxation were used to characterize the morphology and properties of the TPVs in detail. It was found that when the ratio of EPDM/NBR was 2:4, the tensile strength increased by ~14% compared with PP/EPDM TPV without NBR. Meanwhile, the reprocessing properties, rheological characteristics and instantaneous tensile deformation, etc. all exhibited sudden changes at this critical ratio.     

Photoinitiated crosslinking of EPDM/inorganic filler blends and characterization of related properties

<正>Photoinitiated crosslinking of ethylene-propylene-diene terpolymer(EPDM) blends filled with calcium carbonate, talc and calcined kaolin(CK) in the presence of benzil dimethyl ketal as photoinitiator and trimethylolpropane triacrylate as crosslinker and their related properties have been studied by different analytical methods.The results from gel content and heat extension determination show that the efficiency of photocrosslinking of EPDM increases with increasing the content of diene and its molecular weight.The EPDM blends with 100 phr different inorganic fillers can be photocrosslinked to gel content of above 60%by 5 s UV-irradiation under optimum conditions.Under the same conditions of irradiation,the orders of photocrosslinking rate and final gel content are EPDM/CaCO_3EPDM/talcEPDM/CK.The data from thermogravimetric analysis,dynamic mechanical thermal analysis,electrical properties,mechanical tests and scanning electron microscopy show that UV irradiation crosslinking apparently enhances the thermal stability,mechanical properties and electrical properties of the photocrosslinked EPDM/inorganic filler samples.Although the attenuated total-reflection FTIR data show that inorganic fillers can promote the surface photo-oxidation of EPDM/inorganic filler samples with increasing the irradiation time,the above related properties of the photocrosslinked EPDM blends irradiated within 5 s are enough to satisfy many applications in the cable industry.     

Mechanical and Rheological Behavior of Unvulcanized and Dynamically Vulcanized i-PP/EPDM Blends

The mechanical and rheological behavior of dynamically vulcanized PP/EPDM blends is examined and compared with those of unvulcanized blends. The effect of blend ratio and dynamic vulcanization of EPDM rubber on tensile properties and flow are investigated. The mechanical properties of the blends are strongly influenced by the blend ratio. With the increasing of EPDM content the value of yield stress in a solid state decreases with the elastomer volume fractions less than 0.45 for the unvulcanized blends. For the dynamically vulcanized blends the interval of EPDM content, at which the yield peak is seen, is rather limited below 0.25 elastomer volume fractions. It is shown that dynamic vulcanization changes the deformational behavior of PP/EPDM blends. The rheological properties of dynamically vulcanized blends depending on the ratio of the components may be similar to the properties of polymer composites containing the highly disperse structuring filler. The distinction between the rheological behavior of unvulcanized and dynamically vulcanized blends is related to differences of their structures and viscoelastic characteristics of unvulcanized and vulcanized EPDM phase.     

Structure and mechanical properties of SRP/HDPE/POE (EPR or EPDM) composites

The effects of dicumyl peroxide (DCP) and ethylene-octylene copolymer (POE), ethylene-propylene copolymer (EPR) or ethylene-propylene-diene terpolymer (EPDM) on the structure and properties of scrap rubber powder (SRP)/high-density polyethylene (HDPE) composites were studied. Torque and gel content results show that DCP promotes crosslinking of the SRP/HDPE/POE (EPR or EPDM) composites. The SRP/HDPE/POE (EPR or EPDM) composites containing a small amount of DCP have better mechanical properties than their corresponding composites without DCP. Highest tensile strength and elongation at break are found in the dynamically vulcanized SRP/HDPE/POE composite. Scanning electron microscopy (SEM) results show that good bonding between SRP and matrix is formed in the SRP/HDPE/POE (EPR or EPDM) composites with DCP.     

EPDM/PP热塑性弹性体在循环应力下的老化行为研究

本文研究了动态硫化EPDM/PP热塑性弹性体的动态疲劳老化行为,考察了其力学性能的变化,并分析了产生力学性能下降的原因。实验结果表明,随着疲劳时间的延长、疲劳振幅的增大,材料的断裂强度降低,并认为疲劳过程中完全硫化的EPDM橡胶粒子和热塑性塑料PP界面处的分子链断裂、滑移导致了断裂强度的降低;紫外光的加入,加速了材料在疲劳过程的分子链断裂、滑移速率,使材料的断裂强度有更大程度的降低;在机械疲劳老化单独作用下,材料体系几乎没有发生氧化反应,而紫外光的加入,促使了机械疲劳老化过程中氧化反应的发生。