Effect of nanocomposite of attapulgite/EVA on flow behavior and wax crystallization of model oil

Nanocomposites of attapulgite (ATT)/ethylene vinyl acetate copolymer (EVA) were prepared with organically modified ATT covering in EVA. Organically modified ATT was prepared using KH550 and organic acid. The effect of nano-hybrid on the flow behavior of model oil containing 15?wt% wax was evaluated. The wax crystallization and crystal morphology of the model oil at low temperature were observed by polarizing optical microscopy (POM). The results indicated that the nano-hybrid with long-chain organic acid-modified ATT exhibited a better effect compared with the nano-hybrid with short-chain organic acid-modified ATT, pure EVA. In addition, it is interesting to note that EVA (VA?=?32%)/stearic acid-modified ATT composite polymeric pour-point depressant (PPD) S-AtPPD(32) provided better cold-flow improvement for the model oil than EVA (VA?=?32%)-modified nano-SiO₂ composite PPD N-SiPPD (32) with a low dose, which resulted in a regular, bar-shaped, and uniform arrangement of wax morphologies. The pour point of the model oil was reduced from 30°C to ?1°C when doped at 200?ppm S-AtPPD(32).     

倍半硅氧烷/改性乙烯-乙酸乙烯酯共聚物复配降凝剂对蜡油倾点的影响

乙烯-乙酸乙烯酯共聚物(EVA)是原油常用的降凝剂(PPDs),但其分子结构相对比较单一,对部分油品降凝效果不佳。 为了提高EVA的降凝效果,使用硬脂酰氯与羟基化的EVA直接反应的方法制备烷基长链接枝改性EVA,并与带有烷基长链的倍半硅氧烷(SS)纳米粒子进行复配。 研究了改性EVA和SS复配降凝剂对蜡油的降凝效果和降凝机理。 结果表明:复配降凝剂为蜡提供晶核,使蜡晶变小并降低蜡的沉淀量,导致蜡油中形成的蜡晶难以搭接在一起,形成了松散的结构,当复配质量比m(EVA-g)∶m(SS-L)=1∶2时,在蜡油中的质量分数为0.1%时,蜡油倾点降低了25 ℃。     

Effect of the liquid–liquid phase separation on the crystallization behavior of a poly(ethylene‐ran‐vinyl acetate) and paraffin wax blend

The effect of liquid–liquid phase separation (LLPS) on the crystallization behavior of poly(ethylene‐ran‐vinyl acetate) with a vinyl acetate content of 9.5 wt % (EVA‐H) in the critical composition of a 35/65 (wt/wt) EVA‐H/paraffin wax blend was investigated by small‐angle light and X‐ray scattering methods and rheometry. This blend exhibited an upper critical solution temperature (UCST) of 98°C, and an LLPS was observed between the UCST and the melting point of 88°C for the EVA‐H in the blend. As the duration time in the LLPS region increased before crystallization at 65°C, both the spherulite size and the crystallization rate of the EVA‐H increased, but the degree of the lamellar ordering in the spherulite and the degree of crystallinity of the EVA‐H in the blend decreased. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 707–715, 2000     

Effect of the liquid–liquid phase separation on the crystallization behavior and mechanical properties of poly(ethylene‐ran‐vinyl acetate) and paraffin wax blend

The effect of liquid–liquid phase‐separation (LLPS) on the crystallization behavior and mechanical properties of poly(ethylene‐ran‐vinyl acetate) (EVA) with various amounts of vinyl acetate and paraffin wax blend was investigated. The blend of EVA‐H (9.5% vinyl acetate) and the wax became homogeneous at temperatures greater than its upper critical solution temperature (UCST) (98°C), and an LLPS was observed between UCST and the melting point of 88°C for EVA‐H in the blend. The existence of the LLPS is attributed to the relatively large amount of the hydrophilic component of vinyl acetate in EVA, although the molecular weight of the wax was just 560. However, LLPS did not occur for the EVA/wax blend when the content of vinyl acetate in EVA was less than 3%. This behavior was explained by using the Flory–Huggins lattice model with an effective interaction parameter. The degree of crystallinity of EVA‐H in the EVA‐H/wax blend, judged from a melting endothermic peak in differential scanning calorimeter (DSC) thermograms obtained during heating runs, decreased with increasing duration time in the LLPS region. The flexural modulus of the EVA/wax blend became maximum at certain blend composition (about 30 ∼ 40 wt % EVA depending upon the amount of vinyl acetate). This behavior can be explained by the fact that this blend composition has the largest relative degree of crystallinity of EVA measured by DSC and wide‐angle X‐ray scattering method. We found that the flexural modulus of the binder itself is directly related to that of a feedstock consisting of larger amounts of metal powder and the binder, which can help someone to develop a suitable binder system for a powder injection molding process. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 37: 1991–2005, 1999     

Theoretical study of the prohibited mechanism for ethylene/vinyl acetate co-polymers to the wax crystal growth

To understand the effect of pour point depressants (PPD) on the wax growth is important for designing PPD additives for use with different oils with high efficiency and good economics. In our current study, molecular mechanics, molecular dynamics, and quantum mechanics calculations were performed to investigate the prohibited mechanism of ethylene/vinyl acetate (EVA) additives on the paraffin deposition in oils. On the wax surface, a single C18 molecule and clusters were preferably deposited on the wax surface (010) in a parallel conformation, which resulted in the formation of large blocks of wax crystal. MD simulation indicated that the linear conformation of EVA was more favorable to be adsorbed onto the carbon backbone of the wax surface (010) with the polar fragments of vinyl acetate staying upside of the surface. Furthermore, four EVA molecules can efficiently optimize the inhibition effect for the deposition of the solute C18 molecules over 10x8 size wax surface (010). According to the simulation results, a simplified rational model was established to estimate the minimum dosage of EVA-type PPD for fuels with different paraffin contents. In a certain degree, this simplified model has provided an effective route to correlate microstructures and the properties of polymer-involving systems, which will shed light on the application of theoretical studies in industries.     

Synthesis of Some Additives and Study Effect of Gas Oil Composition on Flow Properties

Nine additives were prepared by esterification of dibasic acid (succinic, adipic, sebacic acid) and polyethylene glycol (Mol.wt.=600, 1000, 4000). These additives were characterized by infrared spectral analysis, average molecular weight and polydispersity index. Their influence on the depression of pour point for two type of paraffin gas oils (G1 and G2) were investigated, blends of paraffin gas oils G1 and G2 by different ratio, when their untreated and treated by additives were evaluated as pour point depressant in comparison with the original paraffin gas oils G1 and G2.

The effect of additive type and gas oil composition on wax crystal modification were studied using the photo micrographic analysis. Diethoxylate (eo=182) sebacate with blend gas oil No. 3 has achieved the best performance as pour point depressant. The photo micrographic analysis showed that, the wax morphology was greatly modified to fine dispersed crystals of compact size. A correlation between the pour point depression and the extent of wax modification was detected.     

Slurries and emulsions of waxy and heavy crude oils for pipeline transportation of crude oil

The high viscosity of many asphaltic crude oils and the high pour points of many waxy crude oils present significant problems in their transportation over long distances by pipeline and tanker. While heating the oils and insulating the pipelines will help alleviate the problem, there is danger associated with an extended shutdown of flow and either congealing or solidification of the oil. A possible solution which we have studied in the laboratory is the emulsification or dispersion of the oil in water or brine so that shear takes place in the continuous aqueous phase rather than the oil droplets or particles.Synthetic waxy crude oils were prepared by dissolving paraffin wax in white mineral oil at slightly elevated temperatures and then measuring the pour point. One containing 30% wax had a pour point of 43°C and was selected for preparations of the dispersions. This was emulsified in water at a temperature higher than the pour point by using a suitable surfactant as an emulsifying agent. Rheological properties were measured at various temperatures and are reported in the paper. The method shows great promise for use in countries such as China which produce significant quantities of waxy crude oil and have seasonal temperatures significantly lower than the pour point of the crude oil.     

Study on the Inherent Factors Affecting the Modification Effect of EVA on Waxy Crude Oils and the Mechanism of Pour Point Depression

The Ar-Sai waxy crude oils were taken as the research objects, and the viscosity reduction rates and the condensation point reduction rates were regarded as the evaluation indexes, the impacts of components content of the crude oils and carbon number distribution of waxes on the modification effect of EVA-type pour point depressant (PPD) were analyzed by using gray correlation analysis method. The oil wax was acquired by applying the extraction and separation techniques initially, then the structures and the lattice parameters of wax crystals before and after adding the PPD were studied by polarized light microscopy observation and x-ray diffraction techniques, the mechanism of pour point depression was discussed at last. The results indicate that wax content and the low carbon number wax have significant influences on the modification effect of PPD, while the impact of high carbon number wax is relatively small. Co-crystallization is the main mechanism of pour point depression, nevertheless, the impacts of the asphaltenes, resins, solid particles, and light components of the crude oils on the modification effect of the PPD cannot be ignored.     

Synthesis and Evaluation of Some Novel Polymeric Surfactants Based on Aromatic Amines Used as Wax Dispersant for Waxy Gas Oil

Dicarboxy methyl ethoxylated aniline and 1,3‐dicarboxy methoxy benzene were synthesized as intermediate monomers to prepare six polyester surfactants. The first three of them were obtained by polyesterification of dicarboxy methoxy ethoxylated (EO=10) aniline with polyethylene glycol (M. wt.; 400, 600, 1000). The product named as An E₁₀ 400, An E₁₀ 600, and An E₁₀ 1000. The later three was obtained by polyesterification of 1, 3 dicarboxymethoxy benzene with the same PEG at different molecular weights. The product named as; R 400, R 600, and R 1000. These polyesters were characterized by FT.ir, and GPC. These polyesters were evaluated as pour point depressants of a mixed blend of Egyptian Western desert gas oil, (PP=18^oC). The obtained data showed that, the maximum reduction of pour point was obtained with An E₁₀ 1000 (ΔPP=15°C) and R 1000 (ΔPP=18°C) regarding to the two groups of polyesters respectively. Blends from these compounds were done. From the results, it was found that, the blend IV exhibit the maximum depression of pour point, (ΔPP=24°C). The photomicrographic investigation for the change of wax crystals morphology and size as the results of using the pour point dispersants was carried out after the treatment by the blends. The photomicrographic pictures showed a great modification of wax crystals was obtained as a result of dispersion of wax by the additives. The results were compared with a commercial additive at 1000 ppm. It was found that, its ΔPP=18°C. This work was extended to study the surface active properties of these polyesters at liquid/air interface. The obtained data were used to explain the discrepancy of these polyesters toward pour point depression.     

Thermal behavior and solid fraction dependent gel strength model of waxy oils

Thermal behavior of waxy oils is investigated using the techniques of thermogravimetric (TG) analysis and differential scanning calorimetry (DSC). Model waxy oils and real waxy crude oils are utilized. Decomposition temperatures of waxy oils are obtained using TG analysis. The effects of thermal history, wax content, and additive on the gelation process of waxy oils are investigated using DSC. The DSC method provides a measure of wax solubility as well as solid fraction. An integration method and a computation method are utilized to predict solid fraction. In addition, wax crystallization onset points are obtained at the cooling rates ranging from 1 to 20 °C min^?1. Similarly, wax dissolution endset points are obtained at heating rates ranging from 1 to 20 °C min^?1. Extrapolated onset and endset points yield wax precipitation temperature and wax dissolution temperature, respectively. Subsequently, wax solubility curves are obtained using thermodynamic computations. A wax precipitation temperature method and a wax dissolution temperature method combine thermodynamic phase behavior with onset/endset points to predict solid fraction. Both the wax precipitation temperature method and the wax dissolution temperature method can predict solid fraction of waxy oil samples. The wax precipitation temperature method and the wax dissolution temperature method are accurate when the temperature is close to the wax appearance temperature. A heat-integration method provides accurate values of the solid fraction at temperatures significantly below the wax appearance temperature. Therefore, integration method and wax precipitation temperature/wax dissolution temperature method are combined to predict solid fraction. The effect of solid fraction on yield stress is also investigated using differential scanning calorimetry and rheometry. Finally, a new solid fraction dependent gel strength model is obtained for shut in and restart of waxy crude oil pipelines.     

Submicron carbon-based hybrid nano-pour-point depressant with outstanding pour point depressant and excellent viscosity depressant

We have investigated the effective utilization potential of carbon nanomaterials in the field of pour point depressants, and reported three kind of carbon-based hybrid nano-pour-point depressants with different dimensions. In this paper, poly-α-olefins-acrylate high-carbon ester pour point depressant (PAA-18) was prepared by esterification and polymerization as the basic pour point depressant. Then, the basic pour point depressant PAA18 was modified by solvothermal method with graphene oxide (GO), carbon nanospheres (Cna) and carbon nanotubes (OCNTs). The morphology and structure of the composites were analyzed by SEM, FTIR and XRD. The results showed that PAA18 was successfully in situ polymerized on GO, Cna and OCNTs. We took the simulated oil as the experimental object, and evaluated its pour point, rheological properties and wax crystal morphology, and achieved excellent results. In the three carbon-based hybrid nano-pour-point depressants with different carbon contents, the oxidation carbon nanotubes composite pour point depressant (PAA18-1 % OCNTs) with carbon content of 1 % had the best pour point and viscosity reduction effect when the dosage was 1250 ppm, which could make the pour point of the simulated oil containing wax decrease by 16 °C. PAA18-1 % OCNTs reduced the pour point by 5 °C more than PAA18. This paper provides reference for the application of carbon nanomaterials in the field of pour point depressant.     

Comparative methods in the determination of wax content and pour points of crude oils

In this research, differential scanning calorimetry (DSC) and gas chromatography is used to determine the wax content of fourteen crude oils of different sources. Different empirical equations were applied to compare the wax content of crude oils. For the fourteen crude oil samples with the wax content ranging from 7.5 to 43.8 mass%, it was observed that the results of empirical equations were in good agreement with those determined by DSC and GC. Accordingly, a correlation between ASTM pour point and the temperature at which 2 mass% of wax has precipitated out from crude oil is developed.     

表面接枝改性纳米二氧化硅填充聚丙烯的结晶行为

应用差示扫描量热方法研究了纳米二氧化硅 (SiO2 )及其表面接枝改性对聚丙烯 (PP)结晶过程、等温与非等温结晶动力学的影响 ,并研究了上述等温结晶的熔融行为和平衡熔点 .研究发现纳米SiO2 具有明显的异相成核效应 ,能够提高PP的结晶温度、熔融温度、结晶度和结晶速率 ,但降低聚丙烯结晶的完善程度 .粒子的表面接枝处理 ,因改善了粒子与基体的亲和性而有利于粒子成核效应的提高 ,而且此效应尚与粒子的分散相关     

Multiple melting behavior of poly(lactic acid) filled with modified carbon black

Two melting peaks are generally observed in a heating scan for isothermally crystallized poly(lactic acid) (PLA)/carbon black (CB) and PLA/modified carbon black (MCB) composites. To investigate the origin of the above double melting behavior, the melting behavior after isothermal crystallization was analyzed with differential scanning calorimetry, wide‐angle X‐ray diffraction, and small angel X‐ray scattering techniques. The double melting of the crystallized samples can be explained by the model of two populations of lamellae, the double peaks of low and high temperatures are contributed to the melting of the small lamellae produced by secondary crystallization and that of the major crystals formed in the primary crystallization process, respectively. Spherulitic growth rates of the neat PLA and PLA/MCB composite were analyzed and the occurrence of a regime transition was demonstrated. For the PLA, a clear regime transition was observed at around 125 °C. For the PLA/MCB, it occurred at 130 °C. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 1971–1980, 2009     

Synergistic effect between surfactants and polyacrylates-maleicanhydride copolymers to improve the flow properties of waxy crude oil

Four copolymers were prepared by copolymerization of octadecyl acrylate with maleic anhydride abbreviated as [ODM], the resulted copolymer was reacted with octadecylalcohol [ODMSA], hexadecylamine [ODMCA], benzyl alcohol [ODMBA] and aniline [ODMAn]. Three oil-soluble surfactants were also prepared by esterification of mono, di and tri ethanolamine with oleic acid, abbreviated as [MEAO, DEAO and TEAO]. These compounds were purified and characterized by FTIR, ¹H-NMR and GPC. The prepared copolymers were evaluated individually and mixed with the oil-soluble surfactants and evaluated as flow improvers and pour point depressants for waxy crude oil. It was found that, the polymer with aromatic side chain [ODMBA] exhibited the maximum pour point depression ΔPP?=?24°C at concentration 1000?ppm, while the minimum pour point depression was obtained by [ODMCA] which pronounced ΔPP?=?15°C at 1000?ppm. Furthermore, the blend [B4] between [ODMBA] and oil-soluble surfactant [TEAO] achieved extra depression of pour point (ΔPP?=?30°C). The rheological properties of the treated and untreated crude oil with the polymeric additives were also investigated and it was found that Bingham yield value (τ_B) was decreased from 1.63?Pa at 32°C to 0.3?Pa at the same temperature and 500?ppm concentration of [ODMBA].     

Preparation the Esters of Oleic Acid-Maleic Anhydride Copolymer and Their Evaluation as Flow Improvers for Waxy Crude Oil

Five comb-like copolymers derived from oleic acid-maleic anhydride were prepared and then esterified by long-chain fatty alcohol (POMA C_n), where n = 18, 20, 22. These polymers were characterized by FTIR and ¹H NMR analysis. The molecular weight was determined by using gel permeation chromatography (GPC). The prepared copolymers were investigated as flow improvers and pour point depressants (PPD) for crude oil. From the evaluation, it was found that, the maximum depression of PP was obtained by (POMA₂ C₂₂) with long-chain alcohol (C₂₂–OH) from 27°C to 15°C (ΔPP_3000ppm = ?12°C). On the other side, it was remarked that no depression obtained by (POMA₂ C₁₈), which esterified by alcohol (C₁₈–OH) at the same condition. The depression of pour point effectiveness was discussed on the light of polymers structure, molecular weights, and their concentrations. By analysis the results of the rheological flow properties, it was found that the POMA₂ C₂₂ enhanced the Bingham yield values (τ_β). The τ_β for crude oil without additives against 15, 27, and 39°C were 0.286, 0.131, and 0.075 Pa respectively, whereas the τβ for the treated crude oil with POMA₂ C₂₂ were 0.027, 0.022 and 0.010 Pa at 3000 ppm at the same temperatures. By using the photomicrography analysis, it was found that, the wax morphology was greatly modified to fine dispersed crystals of compact size.     

Two‐way multi‐shape memory properties of peroxide crosslinked ethylene vinyl‐acetate copolymer (EVA)/polycaprolactone (PCL) blends

Rare studies have investigated on the 2‐way shape memory crosslinked blends with multiple shape memory behavior up to date. To consider the merit of commercial cost‐competitive crystalline polymers, ethylene vinyl‐acetate copolymer (EVA) / polycaprolactone (PCL) blends (60/40 and 30/70) were peroxide‐cured to form the 2‐way multi‐shape memory crosslinked blends using a melt‐blending method. Both resins were selected to have a similar controlled crosslinking degree, which allowed us to distinctly evaluate their actuation contributions from the cooling‐induced elongation (crystallization) and from the entropy‐driven elongation during cooling process, respectively. In the 2‐way process for the 60/40 system, 2 respective peaks contributed from the cooling‐induced crystallization of EVA and PCL in the cooling curves based on the strain derivate rates at various temperatures were observed. After the cooling process under the loading stress of 150 kPa, the 2‐step heating‐induced contraction process with increasing temperature started at 54.1°C above the melting temperature of PCL at 52.3°C and EVA at 78.3°C, demonstrating 2‐way multi‐shape memory behavior. The multi‐step behavior was more prominent at higher PCL composition and higher load for the 30/70 system. It was found that the entropy‐driven contribution to the overall actuation magnitude increased with increasing nominal loads due to the increased orientation of molecular networks in the blends. The current approach offers numerous possibilities in preparing 2‐way multi‐shape memory crosslinked blends.     

Influence of crystallization conditions on the crystalline transformation behavior of nylon 10 14

Three kinds of nylon 10 14 crystals with different perfections were prepared under various crystallization conditions. The Brill transition behavior of these nylon 10 14 crystals was investigated by variable-temperature X-ray diffraction. It was found that the crystallization conditions influence the Brill transition temperature greatly. The Brill transition temperature of the lamellar crystals grown from dilute solution is so high that no Brill transition temperature can be observed before melting. However, for crystals postannealed at 125 °C, the Brill transition temperature is as low as 130 °C. The results show that the Brill transition behavior of nylons is strongly dependent on the crystallization conditions, for example, the perfections of the crystals.     

Controlled synthesis of polymethylene-b-poly(ethylene glycol) as well as its crystallization and self-assembly behavior

Polymethylene-b-poly(ethylene glycol) (PM-b-PEG) with different block length ratio was synthesized by a combination of polyhomologation and coupling reaction. The effect of hydrophilic and hydrophobic block length on the crystallization process and self-assembly behavior of PM-b-PEG was self-assembled were investigated. The results showed that with the increase of methylene units, the crystallization temperature of PM block raised from 54.59?°C to 70.93?°C gradually, while that of the PEG block reduced from 17.54?°C to 15.23?°C. In addition, the amphiphilic PM-b-PEG was self-assembled into star-like micelles in water, and its diameter extended from 98.2?nm to 151.9?nm as the block length of hydrophobic PM increased from 30 to 70. And the micelles also exhibit super stability when the concentration of copolymer precursor is 0.50?～?0.90?mg/ml and the storage temperature lies in the range of 25?～?60?°C.     

Differential thermal analysis of polyethylene under high pressure

The design of a differential thermal analysis apparatus for use at elevated pressure is described. Experiments on melting and crystallization of folded-chain crystals of polyethylene and poly(ethylene–butene-1) copolymer, and melting of extended-chain polyethylene crystals have been conducted at pressures up to 4200 bars. The precision in transition temperature measurement was ±1°C. The Clausius-Clapeyron equation predicts the melting point increase with pressure at atmospheric pressure to be 32.0°C/kb. The melting point depression due to copolymerization remained constant over the complete pressure range analyzed on the poly(ethylene–butene-1) used in this study. Crystallization of polyethylene is retarded at elevated pressures, and a 50% larger degree of supercooling is necessary at 5000 bars to give a crystallization rate equal to that observed at atmospheric pressure. The difference in melting point between folded-chain and extended-chain polyethylene increases from 8.4°C at 1 bar to 25.6°C at 3000 bars.