聚乙烯、聚丙烯及乙丙共聚物/正烷烃体系低临界共溶温度（LCST）的研究

高分子溶液的低临界共溶温度（LCST），即在高温发生相分离的温度，除受溶剂，体系压力以及高聚物的分子量影响外，还与高聚物本身的结构有很大关系。本文深入细致地研究了聚乙烯、聚丙烯以及乙丙二元共聚物的结构、组成与LCST的关系。首先进行溶剂的选定，测定了不同分子量的乙丙共聚物在正戊烷、正已烷和正庚烷中的LCST。发现分子量的差异对LCST的影响以在正庚烷中为最小，故而选定了正庚烷为溶剂。采用小川的方法，将LDPE和LLDPE在Soxhlet萃取器中分别先后用正已烷、正庚烷抽提分级。用红外光谱法、DSC分别测定了原始样及各级分的支化度、结晶度。结果表明：从正已烷级分、正庚烷级分到庚烷剩余级分，支化度依次降低，结晶度依次增大。以正庚烷为溶剂，测定了原始样及各级分的LCST。结果表明：聚乙烯的LCST随其支化度的增大而增高。测定一系列支化度不同的超低密度聚乙烯（VLDPE，乙烯与戊烯共聚，控制C_2/C_5比来合成）~*的LCST得到同样结果。采用红外光谱法测定了几种不同催化体系（Vcacac)_3、VOCl_3、V_(5-9)和TiCl_4）合成的一系列乙丙共聚物（EPC）的组成（C_3% mol）。以正庚烷为溶剂测定了它们的LCST。结果表明：对于同一种催化体系合成的EPC，LCST随着C_3%的增高而逐渐升高。同样C_3%含量下，钒催化体系合成的EPC的LCST则比钛催化体系合成的EPC的LCST要高。比较三种钒催化体系合成的EPC的LCST，发现在C_3%含量较低时（C_3% < 18%），相同C_3%含量下三者的LCST大致相同；而当C_3% > 20%时，相同C_3%含量下则有LCST_(V(acac)_3) > LCST_(V_(5-9)) > LCST_(VOCl_3)。这说明VOCl_3催化体系合成的EPC有较长的乙烯序列，V_(5-9)催化体系次之，V(acac)_3的序列均匀性最好。这个结果与于旻用结晶速率法研究的结果一致。为进一步深入研究乙丙共聚物中乙烯序列长度对LCST的影响，对几种C_3%含量不同的钛催化体系合成的EPC用小川序列分级的方法进行分级，得到组成相近（红外测定C_3%）、序列长短不同（DSC，红外给出证据）的EPC。以正庚烷为溶剂测定各级分的LCST，结果表明：在组成一定（大致相同）的条件下，随着EPC中乙烯序列的增长LCST逐渐降低。以上结果用CMO（Correlations of Molecular Orientations）理论均予以圆满解释。以正已烷、正庚烷为溶剂测定了聚乙烯、聚丙烯、乙丙共聚物以及聚乙烯/乙丙共聚物、聚乙烯/聚丙烯、聚丙烯/乙丙共聚物和聚丙烯/乙丙共聚物/聚乙烯混合体系的LCST分布曲线（浊度—温度变化曲线）。一元、二元、三元体系分别有一个、二个、三个浊度突变点。混合体系的突变点与组成该体的单组分的浊点（LCST）相对应，这一结果表明可以通过测定共聚合产物的LCST分布曲线来鉴定聚合物的生成与否。初步建立了一种利用LCST分布曲线方法来表征分子量分布的相对方法。用此方法测定了经GPC柱淋洗分级的乙丙共聚物单级分和组合级分的分子量分布，得到的规律与GPC测得的结果相符。

聚烯烃复合膜的附生结晶研究

本文以电子显微镜、光学显微镜为手段，系统地研究了结晶温度，样品厚度、降温速率、分子支化等因素对聚乙烯（PE）与全同立构聚丙烯（ipp）复合膜附生结晶的影响。降温速率过慢或过快均对HDPE/ipp体系的附生结晶不利。HDPE/ipp体系的附生界面层厚度在降温速率缓慢时约为900A；在降温速率过快时约为1200A；在附生结晶的最佳降温速率下的约为1800A。HDPE分子支化对PE/ipp体系的附生结晶也不利。支化越严重，附生界面层厚度越薄。在最佳降温速率下，HDPE附生界面层厚度约为1800A；LLDPE约为1200A；LDPE不足300A。以偏光显微镜研究HDPE/ipp体系的附生结晶较为成功，在HDPE厚达3600A时，仍可看到很少量的HDPE取向结晶。而以偏光显微镜研究LLDPE/ipp、LDPE/ipp体系附生结晶则较为困难。

Effects of SEBS-g-BTAI on the morphology, structure and mechanical properties of PA6/SEBS blends

Styrene-b-(ethylene-co-1-butene)-b-styrene (SEBS) triblock copolymer functionalized with epsilon-caprolactam blocked allyl (3-isocyanate-4-tolyl) carbamate (SEBS-g-BTAI) was used to toughen polyamide 6 (PA6) via reactive blending. Compared to the PA6/SEBS blends, mechanical properties such as tensile strength, Young's modulus, especially Izod notched strength of PA6/SEBS-g-BTAI blends were improved distinctly. Both theological and FTIR results indicated a new copolymer formed by the reaction of end groups of PA6 and isocyanate group regenerated in the backbone of SEBS-g-BTAI. Smaller dispersed particle sizes with narrower distribution were found in PA6/SEBS-g-BTAI blends, via field emitted scanning electron microscopy (FESEM). The core-shell structures with PS core and PEB shell were also observed in the PA6/SEBS-g-BTAI blends via transmission electron microscopy (TEM), which might improve the toughening ability of the rubber particles.

Shape-gradient composite surfaces: Water droplets move uphill

The approach of water droplets self-running horizontally and uphill without any other forces was proposed by patterning the shape-gradient hydrophilic material (i.e., mica) to the hydrophobic matrix (i.e., wax or low-density polyethylene (LDPE)). The shape-gradient composite surface is the best one to drive water droplet self-running both at the high velocity and the maximal distance among four different geometrical mica/wax composite surfaces. The driving force for the water droplets self-running includes: (1) the great difference in wettability of surface materials, (2) the low contact angle hysteresis of surface materials, and (3) the space limitation of the shape-gradient transportation area. Furthermore, the average velocity and the maximal distance of the self-running were mainly determined by the gradient angle (alpha), the droplet volume, and the difference of the contact angle hysteresis. Theoretical analysis is in agreement with the experimental results.

Low-density polyethylene superhydrophobic surface by control of its crystallization behavior

A simple and inexpensive method for forming a low-density polyethylene (LDPE) superhydrophobic surface by controlling the crystallization behavior of LDPE by adjusting the crystallization time and nucleation rate has been proposed. The resulting porous surface, with hierarchical micro- and nanostructures on the beautiful floral designs, has a water contact angle of 173.0degrees +/- 2.5degrees.

Electrically conductive, melt-processed ternary blends of polyaniline/dodecylbenzene sulfonic acid, ethylene/vinyl acetate, and low-density polyethylene

Although polyaniline (PANI) has high conductivity and relatively good environmental and thermal stability and is easily synthesized, the intractability of this intrinsically conducting polymer with a melting procedure prevents extensive applications. This work was designed to process PANI with a melting blend method with current thermoplastic polymers. PANI in an emeraldine base form was plasticized and doped with dodecylbenzene sulfonic acid (DBSA) to prepare a conductive complex (PANI-DBSA). PANI-DBSA, low-density polyethylene (LDPE), and an ethylene/vinyl acetate copolymer (EVA) were blended in a twin-rotor mixer. The blending procedure was monitored, including the changes in the temperature, torque moment, and work. As expected, the conductivity of ternary PANI-DBSA/LDPE/EVA was higher by one order of magnitude than that of binary PANI-DBSA/LDPE, and this was attributed to the PANI-DBSA phase being preferentially located in the EVA phase. An investigation of the morphology of the polymer blends with high-resolution optical microscopy indicated that PANI-DBSA formed a conducting network at a high concentration of PANI-DBSA. The thermal and crystalline properties of the polymer blends were measured with differential scanning calorimetry. The mechanical properties were also measured.

Characterization and properties of the neutral and doped blends of poly(3-dodecylthiophene) with low-density polyethylene

In this paper, the structures and properties of the neutral and doped blends of poly(3-dodecylthiophene) (P3DDT) with low-density polyethylene (LDPE) were investigated. Wide-angle X-ray diffraction (WAXD), differential scanning calorimetry (DSC), Fourier transform infrared spectra (FTIR), and scanning electron microscopy (SEM) were used to characterize the structures and morphologies of the blends, and conductivity was also measured. It was found that separate crystallizations occur between P3DDT and LDPE. When the amount of P3DDT is small in the blend, it has the effect of a nucleation reagent and has some influence on the crystal structure. After doping, the interaction force between the molecular chains increases, and leads to a more compact packing and a more uniform dispersion in morphology. Through blending, the thermal stability of pure component could be greatly improved, especially when the P3DDT content is 5 wt %. The conductivity measurements indicate that the conductivity increases with the increase of the P3DDT composition and doping time.

Efforts to decrease crosslinking extent of polyethylene in a reactive extrusion grafting process

Grafting of acrylic acid and glycidyl methacrylate onto low density polyethylene (LDPE) was performed by using a corotating twin-screw extruder. The effects of residence time and concentration of initiator and monomers on degree of grafting and gel content of grafting LDPE were studied systematically. Paraffin, styrene, p-benzoquinone, triphenyl phosphite, tetrachloromethane, and oleic acid were added to try to decrease the extent of crosslinking of LDPE. 4-hydroxyl-2,2,6,6-tetramethyl-1-piperidinyloxy (4-hydroxyl-TEMPO) and dipentamethylenethiuram tetrasulfide were also tried to inhibit crosslinking reaction of LDPE during its extruding grafting process. It was found that p-benzoquinone, triphenyl phosphite and tetrachloromethane were good inhibitors for crosslinking of LDPE. (C) 2000 John Wiley & Sons, Inc.

辐照对不相容聚合物共混物相界面粘接的影响

介绍了改善不相容聚合物共混物界面粘接状况的一种崭新方法，应用SEM、TEM技术研究了辐射敏化界面反应对iPP/LDPＥ不相容共混物体系相界面粘接的影响，并结合溶解度参数的方法评估了多官能团单体—三烯丙基异氰酸酯(TAIC)在iPP/LDPE共混物中的分布状况。结果表明，辐射增强界面反应的方法是改善不相容聚合物共混物界面粘结的有效途径。

兰光转换膜的研制及其水稻育秧效果试验

本文介绍了以LDPE与LLDPE为基料的农用兰光转换水稻育秧膜的研制与性能，以及该膜用于水稻育秧的应用效果试验。最终增产效果为5．5％。

On morphology and the competition between crystallization and phase separation in polypropylene-polyethylene blends

Blends of polypropylene (PP) and low density polyethylene (LDPE) have been examined for a series of compositions using differential scanning calorimetry and permanganic etching followed by transmission electron microscopy. Thermal analysis of their melting and recrystallization behaviour suggests two possibilities, either that below 15 wt % PP the blends are fully miscible and that PP only crystallizes after LDPE because of compositional changes in the remaining melt, or else that the PP is separated, but in the form of droplets too small to crystallize at normal temperatures. Microscopic examination of the morphology shows that the latter is the case, but that a fraction of the PP is nevertheless dissolved in the LDPE. (C) 1998 Kluwer Academic Publishers.

Studies on the PTC/NTC effect of carbon black filled low density polyethylene composites

The positive temperature coefficient (PTC) and negative temperature coefficient (NTC) effect of carbon black (CB) filled low density polyethylene (LDPE) composites was studied using electrical resistivity spectra, DSC, tensile mechanical analysis (TMA) and small-angle X-ray scattering (SAXS) techniques. The three LDPEs used have a similar crystallinity and different melting index (MI). The experimental results indicate that the CB has no significant effect on the crystallinity and the long spacing of crystalline domains of LDPE. Based upon the TMA and dynamic elastic modulus spectra, it can be concluded that the PTC effect is related to the thermal expansion of the polymer matrix, and the NTC effect is caused by a decrease of the elastic modulus of the polymer at high temperatures. The NTC effect can be reduced by enhancing either the elastic modulus or the interaction between carbon black and matrix. (C) 1997 Elsevier Science Ltd.

Chemiluminescence studies of radiation induced oxidation of various polyethylenes

The chemiluminescence (CL) emission from three kinds of polyethylene, HDPE, LLDPE and LDPE, which had been exposed to 80 kGy dose from Co-60 in both air and nitrogen, has been examined. CL measurement was done under both nitrogen and oxygen atmosphere. The results show that the CL emission from irradiated samples does not result from irradiation itself, but from the oxidation reactions occurring during and after irradiation. Addition of 1 phr of an antioxidant, Irganox 1010, can effectively inhibit the radiation induced oxidation in LLDPE and LDPE. In the case of HDPE, however, it was found that pure HDPE has the best resistance to radiation-induced oxidation of the polymers examined in this work. However, incorporation of Irganox 1010 was found to have not only a stabilizing effect against radiation induced oxidation, but also to promote the oxidation in some cases.

高密度聚乙烯／低密度聚乙烯／乙烯－醋酸乙烯共聚物共混体系的结晶行为

通过ＤＳＣ和ＷＡＸＤ研究了高密度聚乙烯／低密度聚乙烯／乙烯－醋酸乙烯共聚物（ＨＤＰＥ／ＬＤＰＥ／ＥＶＡ）三元共混体系的热行为和结晶性能。发现当ＨＤＰＥ含量小于４０％时，ＥＶＡ对ＬＤＰＥ起稀释剂作用，促进ＨＤＰＥ、ＬＤＰＥ的晶相分离，使ＨＤＰＥ、ＬＤＰＥ单独结晶．当ＨＤＰＥ含量高于４０％时，ＬＤＰＥ片晶进入ＨＤＰＥ晶相。形成与ＬＤＰＥ在片晶水平上的共晶。

反应性挤出聚乙烯接枝低偶联马来酸酯

将低密度聚乙烯(LDPE)、过氧化二异丙苯(DCP)、低偶联马来酸酯(LCME)均匀混合后,在单螺杆挤出机中进行反应性挤出,得到聚乙烯接枝低偶联马来酸酯(PE-LCME)产品。红外光谱分析确证有部分LCME接枝到PE分子链上。示差扫描量热法(DSC)测定揭示了反应性挤出过程中化学反应的起始温度、峰温和终止温度,以及在静态下反应所需的时间。并且从不同升温速度的DSC曲线可以初步确定挤出温度及分布。反应性挤出得到PE—LCME的接枝率(G)随PE的型号、不同DCP的浓度而呈规律性变化。