接枝LDPE与PET共混物的热力学性能和形态研究

通过红外光谱对合成的三种极性单体接枝ＬＤＰＥ进行了确证,采用热分析仪和扫描电镜研究了接枝ＬＤＰＥ／ＰＥＴ共混物的热力学性能和相形态结构。结果表明,接枝ＰＤＰＥ与ＰＥＴ共混,对ＰＥＴ结晶过程有一定的加速促进作用;由缺口冲击断面观察发现,接枝ＬＤＰＥ以分散相分布在ＰＥＴ连续相中,但相界面之间有丝状物相连,说明接枝ＬＤＰＥ与ＰＥＴ有较好的相容性。     

LDPE与HDPE共晶问题的研究：Ⅱ共混物的结晶形态

本文应用偏光显微镜。考察各种不同牌号的ＬＤＰＥ与ＨＤＰＥ配伍的结晶结构，表明不同品种、不同牌号，即不同链结构的聚乙烯共混物，其相同条件下形成的球晶形态不同。     

LDPE/POE共混物的结晶行为和力学性能

采用熔融共混法制备了低密度聚乙烯（LDPE）／聚烯烃弹性体（POE）共混物,通过差示扫描量热法和广角X射线衍射表征了共？昆物的结晶行为及LDPE、POE结晶的相互影响,研究了共混物的力学性能。随着POE用量的增加,LDPE的结品度稍有减小,结晶的完善性和均一性变差,晶粒尺寸逐渐变小;LDPE在结晶过程中出现了二次结晶;共混物的硬度、定伸应力和熔体流动速率均逐渐减小,拉伸断裂应变则逐渐增加。当w（POE）为30％时,材料的拉伸强度达到最大值,为21.5MPa。随着LDPE含量的增加,POE的结晶度逐渐减小。     

硅烷接枝PE-LLD结晶行为的研究

用傅里叶变换红外光谱（FT-IR）、X射线衍射仪（XRD）、差示扫描量热仪（DsC）分析了熔融接枝反应对线形低密度聚乙烯（PE—LLD）晶体结构和熔融行为的影响，并对晶体结构和熔融行为之间的关系进行了初步探索。结果表明：随着接枝率增加，晶面间距基本不变，晶粒尺寸逐渐减小；接枝后熔点降低，DSC曲线对应的高温熔融峰，即稳定的正交晶型因重排受阻，其含量逐渐减小，低温熔融峰对应的非稳定晶型逐渐增多。将XRD得到的晶粒大小代入Tbomas-Chbbs方程，求得正交晶型的理论熔融温度与DSC的高温熔融温度基本符合，表明PE-LLD接枝后熔融行为的变化是由晶粒尺寸和晶型的改变造成的。     

硅烷接枝交联LDPE、LLDPE及其共混物的结构研究

利用红外光谱、凝胶渗透色谱、热延伸试验、差示扫描量热法、扫描电子显微镜等方法研究了低密度聚乙烯（LDPE）、线型低密度聚乙烯（LLDPE）及其共混物的乙烯基硅烷接枝及交联产物的分子结构、熔融行为和形态。结果表明：硅烷接枝后,LDPE、LLDPE的重均摩尔质量小幅增加;硅烷接枝交联能力为：LLDPE〉LDPE／LLDPE共混物〉LDPE;接枝和交联使LDPE、LLDPE及其共混物的结晶度降低,晶粒变得不均匀;硅烷接枝和交联能增加LDPE／LLDPE共混物的相容性;交联结构提高了LDPE、LLDPE及其共混物的抗冲性。     

PE-HD/E-TMB共混物的结晶形态研究

用自制增韧母料(E-TMB)分别与2200J高密度聚乙烯PE-HD(HE1)和5000S PE-HD(HE2)热机械共混制得HE1/E-TMB和HE2/E-TMB共混物,用偏光显微镜研究了两种共混物之间结晶形态的不同、两种共混物与其简单共混对照样之间结晶形态的不同,讨论了母料中弹性体不同配比、共混物中弹性体不同含量对共混物结晶形态的影响。     

LDPE/LLDPE共混物的研制

通过低密度聚乙烯 (LDPE)与线型低密度聚乙烯 (LLDPE)并用 ,采用双辊开炼机共混制成LDPE/LLDPE共混物 ,并对共混物的比例和稳定剂的加入量进行了探讨 ,结果表明共混物的力学性能明显提高     

LDPE熔融接枝丙烯酸的研究

本文选择丙烯酸作为接枝单体与过氧化二异丙苯、低密度聚乙烯混合，在单螺杆挤出机中进行熔融接枝反应。实验研究了挤出条件、ＤＣＰ用量以及丙烯酸单体用量对熔融接枝的影响。     

LDPE/iPB共混物的性能

采用传统共混方法制备了低密度聚乙烯(LDPE)/全同聚1-丁烯(iPB)共混物,测定了力学性能和热性能。通过偏光显微镜观察和差示扫描量热法等研究了LDPE/iPB体系的结晶行为。结果表明:随着w(LDPE)的增加,共混体系的拉伸强度和弯曲强度出现最小值,热性能下降,结晶变得不完善,LDPE/iPB共混物的相容性较差。     

硅烷接枝LLDPE结晶结构的研究

用傅立叶变换红外光谱(FT-IR)、X射线粉末衍射仪(XRD)、差示扫描量热仪(DSC)分析了接枝率对硅烷接枝线型低密度聚乙烯(SGLLDPE)晶体结构和熔融行为的影响,并对晶体结构和熔融行为之间的关系进行了初步探索。结果表明:随着接枝率增加,晶面间距基本不变,晶粒尺寸逐渐减小;接枝后熔点降低且低温熔融峰热流量逐渐增大,高温熔融峰热流量逐渐减小。     

多组分单体接枝三元乙丙橡胶／PET共混体系的形态结构研究

以PS、DCP、GMA作为PET/EPDM共混体系的增容剂，以DSC和X射线衍射探讨了PET/EPDM共混物的结晶性能，以偏光显微镜和扫描电子显微镜探讨了共混物的形态。结果表明，PET／EPDM共混体系的熔点可提高10℃，玻璃化温度降低，结晶起始温度提高约20℃。共混体系中，当EPDM含量低时，PLM下观察到的是较为完整的球晶，随着EPDM含量逐渐提高，观察得到的是不完善的球晶、微晶、晶粒这样一个晶体变化过程，结晶完善程度降低。     

聚甲醛/共聚酰胺共混物的结晶形态及力学性能

研究了共聚酰胺含量对聚甲醛/共聚酰胺(POM/COPA)共混物结晶形态及力学性能的影响。结果表明:POM/COPA共混物中存在氢键相互作用;结晶温度对POM的结晶形态有较大影响,温度较高时POM结晶较完善,球晶尺寸较大;同时,COPA的加入使共混物的球晶细化,极大地改善了POM的韧性。当COPA含量为4%时,共混物缺口冲击强度达到最大值,拉伸强度几乎不变,POM/COPA具有较理想的综合力学性能。     

LDPE/PS就地相容化研究

在熔融状态下，利用Friedel-crafts烷基化反应就地增容低密度聚乙烯（LDPE）／聚苯乙烯（PS）合金，考察了催化剂品种及其用量、温度、时间等对接枝反应及合金性能的影响。结果显示，无水三氯化铝为一有效催化剂，能实现大分子间的接枝反应，形成LDPE-g-PS，其用量增大时可使体系产生凝胶；升高温度、延长反应时间都不利于接枝百分比的提高；增容后的LDPE／PS合金，其性能得到显著改善。     

mLLDPE及mLLDPE/LDPE共混物挤出加工性能的研究

使用双螺杆挤出机、单螺杆挤出机研究了mLLDPE及mLLDPE/LDPE共混物挤出表面、螺杆扭矩与喂料速度、螺杆转速之间的关系 ,并讨论了有机硅对mLLDPE/LDPE共混物挤出性能的影响     

PP／LDPE共混物熔体流动特性的研究

将两种熔融流动指数（ＭＦＩ）相差大的聚丙烯（ＰＰ）分别与一低密度聚乙烯（ＬＤＰＥ）进行共混，用熔体流动速率仪测定其流动特性。发现ＭＦＩ值高的ＰＰ，当共混比ＰＰ／ＬＤＰＥ为５０／５０时，其熔体流动速率（ＭＦＲ）为最大，本文对此作了初步的分析和讨论。     

PTT/PE共混体系结品动力学及结晶形态研究

采用差示扫描量热法(DSC)研究了聚对苯二甲酸乙二醇酯/聚乙烯(PTT/PE)共混体系的非等温结晶动力学,通过热台偏光显微镜(POM)对共混物在等温条件下的结晶形态进行了研究.结果发现:PTT/PE共混体系各样品的结晶峰温度随着冷却速率的提高而下降,而半结晶时间t1/2随着冷却速率的提高而提高;结晶动力学常数Zc随着冷却速率的提高而下降,表明共混体系的结晶速率随着冷却速率的提高而降低;在POM观察的时间范围内各样品的球晶尺寸随着时间的延长而增大,PTT/PE(30/70)共混体系在190℃结晶时,球晶尺寸较大,即球晶生长较快.     

POE接枝衣康酸增容PA6/POE共混物性能及形态研究

以衣康酸（ITA）为接枝单体,采用双螺杆挤出机和熔融接枝技术制备了一系列乙烯-辛烯共聚物接枝物（POE-g-ITA）,通过红外光谱对接枝物的结构进行了表征,研究了引发剂和单体用量对POE-g-ITA接枝率和熔体流动速率的影响,当POE/ITA/过氧化二异丙苯（DCP）=94/6/0.36时,接枝率达到1.36 %;通过双螺杆挤出机将相容剂POE-g-ITA引入到聚酰胺6/乙烯-辛烯共聚物（PA6/POE）共混物中,研究了共混物的力学性能和形态结构。结果表明,加入5份（质量份数,下同）POE-g-ITA后,PA 6/POE共混物的冲击强度提高到纯PA 6的12.78倍,PA6与POE两相界面变得模糊,分散相尺寸明显减小,界面相互作用明显增强,相容性得到显著提高。     

Structure and Morphology Development in Films of mLLDPE/LDPE Blends During Blowing

Summary: In this work the analysis of the structure orientation, morphology, relaxation time and optical properties of blown films of mLLDPE, LDPE and their blends were performed by using WAXD, SALS, AFM, DSC and rheological and haze tests. For mLLDPE film, the crystals do not present “a”‐axis orientation along the machine direction; a distinct spherulite like superstructure is seen. The film surface is very rough. The values of bulk and surface haze are higher than LDPE and blends, whereas the relaxation time is lower. For LDPE film the (110) planes are parallel and at same time twisted with respect to the layer of the film with the “a”‐axis well oriented along the machine direction. No spherulite superstructure is observed and the surface of the film is more regular. High values of relaxation time are observed. The surface haze is the predominant contribution to the total haze. For the blend films no clear and distinct spherulite structures are observed. The orientation degree increases with composition never approaching that of LDPE. The surface is very more regular and smooth than that of the pure polymers. The haze values are below the values of pure materials. It was underlined that bulk and surface morphology and orientation degree of the crystalline planes along the machine direction dictate the optical properties of the films. Moreover both orientation and morphology are defined by the PE molecular and melt rheology characteristics, processing conditions and blend composition.

Total, bulk and surface haze of mLLDPE/LDPE blend films as a function of composition.     

Compatibilizing Effect of SEBS for Electrical Properties of LDPE/PS Blends

Summary: In the previous study, we observed compatibilizing effects of low density polyethylene (LDPE)/polystyrene (PS) with polystyrene‐block‐poly(ethylene‐co‐butylene)‐block‐polystyrene (SEBS), a triblock copolymer. Blends consisting of 70 wt.‐% LDPE and 30 wt.‐% PS were prepared with a SEBS concentration of up to 10 wt.‐%. This study examined the electrical properties such as the electrical breakdown, water tree length, permittivity and tan δ in the blends. The possibility of using these blends as insulating material substitutes for LDPE was investigated. The electrical breakdown strength reached a maximum of 66.67 kV/mm, which is superior to 50.27 kV/mm of the LDPE used as electrical insulators for cables. In addition, the water tree length decreased with increasing SEBS concentration. The water tree lengths of the blends containing SEBS were shorter than that of the LDPE. The permittivity of the blends was 2.28–2.48 F/m, and decreased with increasing SEBS concentration with the exception of S‐0. Tan δ of the blends increased smoothly with increasing SEBS content.

Breakdown strength , water tree length, permittivity and tan δ of the LDPE/PS/SEBS blends and raw materials.     

Effect of Morphology on the Biodegradation of Thermoplastic Starch in LDPE/TPS Blends

In this study, thermoplastic starch (TPS) was mixed with low density polyethylene with different melt flow indexes in a one-step extrusion process to produce LDPE/TPS blends varied from 32% to 62% by weight of TPS. The influence of starch content and LDPE viscosity on morphology, biodegradation and tensile properties of LDPE/TPS blends were evaluated. Starch continuity and biodegradability were studied by hydrolytic, enzymatic and bacterial degradation. The LDPE viscosity had a considerable effect on the morphology and the connectivity of the starch particles. Evaluation of hydrolytic extraction showed that blends having TPS content above 50 wt% possessed a full connectivity. Studies of biodegradation indicated that the bacterial attack on starch resulted in weight loss of TPS of 92%, 39% and 22%, for PE1/TPS having 62% and 32% TPS, and PE2/TPS (31% TPS), respectively. Comparatively, the weight loss was more significant at 100%, 66% and 31% by hydrolytic extraction. Differences between these two techniques were discussed in terms of the accessibility of starch domains to microorganisms. Tensile properties (ε_b and E) decreased with increasing exposure time to activated sludge. Changes in tensile properties were highly dependent on the biodegradation rate. PE1/TPS blends having 32% starch remained ductile after 45 days of exposure to bacterial attack.