Enhanced propoxylation of alcohols and alcohol ethoxylates

An alkoxylation catalyst consisting of a calcium/aluminum complex partially neutralized in an alcohol ethoxylate base was found to be substantially more active than a conventional potassium hydroxide catalyst in the propoxylation of alcohols and alcohol ethoxylates. With the Ca/Al alkoxide catalyst, propoxylation was faster, required less catalyst, and proceeded at lower temperatures. The latter is desirable since it could help reduce the formation of allyl alcohol and allyl alcohol propoxylate by-products. The two catalysts produced different oligomer distributions, particularly at higher temperatures, which were found to have a marginal impact on surface chemistry. Presented at the annual meeting of the American Oil Chemists' Society, Chicago, Illinois, May 1998.     

Polarity of broad and narrow distributed ethoxylates of fatty alcohols

The polarity of broad- and narrow-range alcohol ethoxylates was studied by inverse gas chromatography. The narrow-range alcohol ethoxylates (NRD) exhibit higher polarity at 70°C than the broadly distributed products (BRD). The difference in polarity between BRD and NRD products decreases, however, with increasing temperature and diminishes at 110°C, which can be predicted from structural increments. The rise of the average number of oxyethylene units increases polarity of the examined products. The changes of ethoxylate polarity are well described by examined parameters with the exception of ΔG^m _s(CH₂).     

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。     

Viscosity,pour point,and chain length relations for the alcohol ethoxylates

Because pour points of surfactant alcohol ethoxylates are important and tedious to determine experimentally, it is desirable to have methods for calculating pour points from other properties, e.g., viscosities (1). To facilitate calculating pour points, several types of equation were developed that relate (a) chain lengths of the alcohol ethoxylates to pour points, (b) chain lengths to viscosities, and (c) viscosities to pour points.     

Photoinduced crosslinking of polyolefine blends. I. Crosslinking of LDPE,PP, and LDPE/PP blends

Photocrosslinking of low-density polyethylene, (LDPE), polypropylene (PP) and their blends was investigated using xanthone and triallyl cyanurate as a photoinitiator and a coagent, respectively. The influence of the change of UV-irradiation conditions on the yield of photoinitiated processes was found to be very similar at any composition, while the crosslinking efficiency decreases with increase of PP content in the blend. The mechanism of the TAC action in photocrosslinking process was proposed and the effect of TAC reactions is discussed with regards to the effectivity of crosslinking of LDPE, PP, or the blends. © 1995 John Wiley & Sons, Inc.     

Silane grafting reactions of LDPE,HDPE, and LLDPE

Vinyl trimethoxysilane and vinyl triethoxysilane grafting reactions, induced by dicumyl peroxide, of LDPE, HDPE, and LLDPE were investigated. The apparent activation energy of vinyl trimethoxysilane grafting reactions was positive when the reactions were induced by 0.2 phr of the peroxide. The apparent activation energies were negative when 0.05, 0.1, 0.15, and 0.25 phr of peroxide were used. The extents of vinyl trimethoxysilane grafting reactions of polyethylenes were in the order of LLDPE > LDPE > HDPE, although the extents of peroxide cross‐linking were in the order of LDPE > LLDPE > HDPE. As compared with vinyl trimethoxysilane, vinyl triethoxysilane produced a relatively high extent of grafting reactions of LDPE but showed a relatively low rate of water cross‐linking reactions of the silane‐grafted LDPE. The investigation of effects of the amount of peroxide on the vinyl trimethoxysilane grafting reaction heats demonstrated that the extent of silane grafting reactions increased proportionally as peroxide was increased until a certain amount (the value was dependent on the amount of silane used). Beyond this amount of peroxide, the silane grafting did not increase, whereas the peroxide cross‐linking appeared to increase significantly with increasing amounts of peroxide. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 3404–3411, 1999     

Rheology of LLDPE,LDPE and LLDPE/LDPE blends and its relevance to the film blowing process

The relevance of polymer melt rheology in film blowing process for linear low‐density polyethylene (LLDPE) and its blends with three different low‐density polyethylenes (LDPEs) has been discussed. The effect of different LDPE components as well as their concentration on shear and elongational viscosity has been investigated. A good correlation has been observed between the extensional rheological parameters of LDPEs measured by different experimental techniques. The molecular structure of parent polymers as well as blend composition play an important role in the rheology of these blends and consequently their performance in the film blowing process. © 2000 Society of Chemical Industry     

LDPE HDPE LLDPE的硅烷接枝反应

研究了DCP (过氧化异丙苯)为引发剂,A1 71 (乙烯基三甲氧基硅烷)与A1 51 (乙烯基三乙氧基硅烷)在LDPE (低密度聚乙烯) ,HDPE (高密度聚乙烯) ,LLDPE (线性低密度聚乙烯)上的接枝反应。A1 71接枝反应过程中,当过氧化物的加入量为0 .2 %时,活化能为正值。而当加入量为0 . 0 5%、0 . 1 %、0 . 1 5%、0 2 5%时,活化能为负值。尽管过氧化物在PE (聚乙烯)中交联反应程度的顺序为:LDPE >LLDPE >HDPE ,但A1 71接枝反应程度的顺序为LLDPE >LDPE >HDPE。与A1 71相比,A1 51在LDPE上具有较高的接枝反应速率,但它在水交联反应过程中,呈现出相对较低的反应速率。通过研究加入过氧化物量的变化对A1 71接枝反应热的影响,可知在过氧化物未达到一定量前(这个数值取决于所加入的硅烷的量) ,当过氧化物增加时,反应热是随之增加的。     

Dynamic modeling of multizone,multifeed high-pressure LDPE autoclaves

A comprehensive mathematical model is developed to simulate the dynamic behavior of multizone, multifeed high-pressure ethylene polymerization autoclaves. To describe the complex flow patterns occurring in low-density polyethylene (LDPE) autoclaves, a user-specified multisegment, multirecycle model representation of the actual multizone reactor is established. A general reaction mechanism is employed to represent the kinetics of ethylene polymerization. Dynamic mass, molar species, and energy balances are derived to predict the polymerization rate, monomer conversion, molecular weight developments (e.g., M_n, M_w, long- and short-chain branching), and temperature profile with respect to time and spatial position in the reactor. Detailed results on the start-up and grade transition of a four-zone autoclave reactor are presented and the effects of the macromixing parameters (e.g., number of segments per reaction zone and the total and side external recycle ratios) on the dynamic behavior of the reactor are investigated. It is shown that the model macromixing parameters can significantly affect the initiator consumption rate in a reaction zone. The present model is capable of predicting accurately the dynamic behavior of LDPE autoclaves and, thus, can be employed in the design, optimization, and control of these reactors. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 2327–2348, 1999     

Mineralogical features of size and density fractions in Sasol coal gasification ash,South Africa and potential by-products

Bulk gasification ash (a mixture of coarse and fine ash particles), a by-product of coal gasification, is formed at elevated temperatures and pressures by the interaction of included minerals present in the coal and “stone”. From the detailed mineralogical and chemical analyses of the pulverised screened size fractions and one density float fraction (<1.9 g/cm³) a number of potential viable by-products were identified.Screening and density separation produced a high ash, low volatile carbon-rich by-product, which is potentially suitable as an energy source for the cement industry. In addition, this carbon-rich product has included devolatilised kaolinite and quartz that are a source of Al₂O₃ and SiO₂. This product could potentially replace the amount of clay required in the cement process. This high ash carbon product is not suitable as a reductant in the metallurgical industry.The ?38 + 20 μm ash size fraction is characterised by a comparatively high proportion of aluminosilicate (transformed product of kaolinite) and Ca-oxide/CaMg-oxide (transformed product of calcite/dolomite). These phases will enhance the pozzolanic reactivity of this ash size fraction and provide material suitable for the cement/concrete industry.The coarse ash size fractions are used as aggregate in road construction and in the manufacture of bricks. If economically and technically feasible, anorthite in the coarse ash size fractions could be beneficiated and used in a refractory.     

Green,catalytic oxidations of alcohols

Three methods are described, in the context of the guiding principles of green chemistry, for the catalytic oxidation of alcohols. The first employs a recyclable oligomeric TEMPO catalyst (PIPO) and sodium hypochlorite as the oxidant in a bromide-free and chlorinated hydrocarbon solvent-free system. The second involves a ruthenium/TEMPO catalyst and oxygen as the oxidant. The third consists of a recyclable water-soluble palladium-diamine complex in conjunction with air as the oxidant in an aqueous biphasic system. The mechanisms of the ruthenium/TEMPO- and palladium-catalyzed oxidations are discussed, and the mechanism of the former is compared with that of the analogous copper/TEMPO catalyst.     

LDPE及LDPE/TiO_2纳米复合材料的熔限及等温结晶研究

采用熔融共混法制备了LDPE／TiO2纳米复合材料,以膨胀计对LDPE及LDPE／TiO2复合材料的熔点、熔限及等温结晶进行了研究。结果表明：膨胀计可用于LDPE及LDPE／TiO2纳米复合材料熔点及熔限的测试：与LDPE相比,LDPE／TiO2复合体系的半结晶期及AVrami指数较小,表明TiO2粒子对LDPE的结晶具有明显的异相成核作用;而Avrrdmi指数为非整数,且Avrami作图直线的最后部分与实验点的偏离,则表明LDPE及LDPE／TiO2纳米复合材料的等温结晶过程比Avrami方程要复杂得多。     

Wavelength sensitivity of enhanced photodegradable polyethylenes,ECO, and LDPE/MX

The wavelength sensitivity for decrease in percent elongation at break of ethylene carbon monoxide copolymer (ECO) and a low density polyethylene containing a metal compound prooxidant (LDPE/MX) on exposure to a borosilicate-filtered xenon-arc source was determined using a set of sharp cut-on filters. The spectral region primarily responsible for the degradation at 60°C is 323–328 nm for ECO and 323–338 nm for LDPE/MX. At 77°C, the sensitivity shifts about 10 nm to longer wavelengths. Based on the wavelength sensitivity of these materials to solar simulated radiation and the transmission properties of window glass, these materials can be expected to lose desirable mechanical properties when exposed to window-glass-filtered sunlight. © 1996 John Wiley & Sons, Inc.     

低密度聚乙烯/改性水滑石纳米复合材料的制备、结构与性能

采用共沉淀法制备了镁铝水滑石(Mg-Al-LDHs),并以之为原料通过柱撑法制备了Zn O柱撑Mg-Al-LDHs。采用硬脂酸(SA)对其进行有机改性,得到改性水滑石(LDHs-SA),然后通过熔融插层法制备了低密度聚乙烯(LDPE)/LDHs-SA纳米复合材料。通过红外光谱分析、热分析、流变学分析、力学性能分析等对LDPE/LDHs-SA纳米复合材料的结构、性能进行了表征与分析。结果表明:当LDHs-SA的添加量为3%时,LDPE/LDHs-SA纳米复合材料的力学性能达到最优,其拉伸强度、断裂伸长率和冲击强度较之LDPE分别提高了4.4%、30.2%和13.1%。此外,LDHs-SA的加入改善了LDPE材料的热稳定性和流变性能。     

Reactive Compatibilizer Precursors for LDPE/PA6 Blends, 4

Summary: The effectiveness of some thermoplastic elastomers grafted with maleic anhydride (MA) or with glycidyl methacrylate (GMA) as compatibilizer precursors (CPs) for blends of low density polyethylene (LDPE) with polyamide‐6 (PA) has been studied. The CPs were produced by grafting different amounts of MA or GMA onto a styrene‐block‐(ethylene‐co‐1‐butene)‐block‐styrene copolymer (SEBS) (KRATON G 1652), either in the melt or in solution. A commercially available SEBS‐g‐MA copolymer with 1.7 wt.‐% MA (KRATON FG 1901X) was also used. The effect of the MA concentration and of other characteristics of the SEBS‐g‐MA CPs was also studied. The specific interactions between the CPs and the blends components were investigated through characterizations of the binary LDPE/CP and PA/CP blends, in the whole composition range. It was demonstrated that the SEBS‐g‐GMA copolymers display poor compatibilizing effectiveness due to cross‐linking resulting from reactions of the epoxy rings of these CPs with both the amine and the carboxyl end groups of PA. On the contrary, the compatibilizing efficiency of the MA‐grafted elastomers, as revealed by the thermal properties and the morphology of the compatibilized blends, was shown to be excellent. The results of this study confirm that the anhydride functional groups possess considerably higher efficiency, for the reactive compatibilization of LDPE/PA blends, than those of the ethylene‐acrylic acid and ethylene‐glycidyl methacrylate copolymers investigated in previous works.

SEM micrograph of the 75/25 LD08/PA blend (with 2 phr SEBSMA1).     

Thermoplastic dynamic vulcanisates containing LDPE,rubber, and thermochemically reclaimed ground tyre rubber

Abstract

Thermochemically devulcanised ground tyre rubber (GTR^DL) was added to fresh rubber compositions, which were then melt blended with low density polyethylene (LDPE). Styrene/butadiene rubber (SBR), natural (NR), and ethylene/propylene/diene (EPDM) rubbers were selected as the fresh rubbers. During blending, dynamic curing was achieved using sulphuric, phenolic, and peroxide curing agents. Some of the GTR was decomposed in the presence of 6 phr Regen^TM Agent-S reclaiming compound before being incorporated into the blends. The resulting thermoplastic dynamic vulcanisates had constant compositions, namely LDPE/rubber/GTR=50:25:25. Sulphuric and phenolic curing agents proved to be most suitable for dynamic curing. The thermoplastic dynamic vulcanisates with the best mechanical performance contained SBR and EPDM rubbers. The observed improvements in mechanical performance were attributed to chain entanglement and co-crosslinking in the interphase between the GTR^DL particles and the surrounding matrix (i.e. with the fresh rubber and/or LDPE). The phase morphology, which was assessed using scanning electron microscopy on the etched surfaces of cryogenically fractured thermoplastic dynamic vulcanisate compositions, is discussed.     

LLDPE/LDPE blends. I. Rheological,thermal, and mechanical properties

Structure and mechanical properties were studied for the binary blends of a linear low density polyethylene (LLDPE) (ethylene‐1‐hexene copolymer; density = 900 kg m⁻³) with narrow short chain branching distribution and a low density polyethylene (LDPE) which is characterized by the long chain branches. It was found by the rheological measurements that the LLDPE and the LDPE are miscible in the molten state. The steady‐state rheological properties of the blends can be predicted using oscillatory shear moduli. Furthermore, the crystallization temperature of LDPE is higher than that of the LLDPE and is found to act as a nucleating agent for the crystallization of the LLDPE. Consequently, the melting temperature, degree of crystallinity, and hardness of the blend increase rapidly with increases in the LDPE content in the blend, even though the amount of the LDPE in the blend is small. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 3153–3159, 1999