The influence of paraffin wax addition on the isothermal crystallization of LLDPE

The influence of paraffin wax addition on the isothermal crystallization kinetics of linear low density polyethylene (LLDPE) was studied in a temperature range where the wax was always in the molten state and could be considered a solvent for LLDPE. The LLDPE/wax blends were prepared by melt mixing in the following compositions: 100/0, 95/5, 90/10, 80/20, 70/30, and 60/40. The results obtained show that the rate of isothermal crystallization is depressed by wax addition at constant crystallization temperatures. LLDPE needs a higher amount of supercooling to start crystallizing as the content of wax increases in the blends. The Flory–Huggins theory (FH) for polymer/diluent mixtures was applied employing equilibrium melting temperature values obtained by extrapolation with the Hoffman–Weeks method. The results of the FH analysis indicate that the interactions between wax and LLDPE are nonlinear and strongly depend on composition. This nonlinear composition dependence of wax/LLDPE interactions is reflected in the complex way in which the overall crystallization kinetics rate depends on both supercooling and composition. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44398.     

添加剂对氯化钠结晶的影响

考察了不同添加剂种类、用量及蒸发结晶温度对氯化钠晶体形状、堆密度的影响。实验结果表明,添加剂葡萄糖和山梨醇对氯化钠晶体形状影响较明显。当蒸发温度60℃、葡萄糖用量0.15%~0.20%(占氯化钠的质量分数)时,有较多的星型晶体,且产品堆密度比不加添加剂时低;当蒸发温度75℃、山梨醇用量(占氯化钠的质量分数)0.05%~0.15%时,氯化钠晶体的形状变化较大,堆密度明显降低,且效果优于添加剂葡萄糖。     

Solubility of paraffin wax in kerosene

The solubility of fully refined paraffin wax (51–54 °C m.p.) in a commercial kerosene has been determined and compared with theoretical and empirical prediction equations. Over the limited range of these experiments the experimental results and the theoretical and empirical curves show similar trends; at concentrations up to about 10 wt % wax the empirical equation seems to predict the experimental results reasonably well, but between 10 and 50 wt % wax the theoretical equation seems more accurate.     

石蜡应用研究进展

综述了国内外石蜡、乳化蜡的最新应用情况,分析了国内石蜡产业存在的问题,并展望了今后特种蜡的发展趋势和方向。     

Influence of non-volatile additives on the diffusion of solvents in polymeric coatings

In many cases, the mutual diffusion coefficient of organic solvents in polymeric solutions limits the drying rate during the drying process. It is known, that the concentration of the solvent in the solution has a significant influence on the diffusion coefficient. The effects of small amounts of non-volatile additives in polymeric solutions on the diffusion coefficient of the solvent are often neglected. In this work, the influence of non-volatile plasticizer triphenylphosphat on the mutual diffusion coefficient of methylenchlorid in the system methylenchlorid–triphenylphosphat–polyvinyl acetate was determined. The results showed that small amounts of plasticizer have significant influence on the mutual diffusion coefficient of solvents in polymeric coatings – especially at low solvent concentrations.     

Deacidification of model vegetable oils using polymeric membranes

Selectivity of polymeric hydrophobic nonporous and hydrophilic nanofiltration (NF) membranes was assessed for the deacidification of model vegetable oils with and without addition of organic solvents. In the model undiluted system, oleic acid permeated preferentially over triacylglycerols in the nonporous membrane, over a wide range of concentrations (?5–70%). The effect of oleic acid concentration on selectivity indicated that the solubility of triacylglycerols in oleic acid played a role in determining the selectivity, besides the solubility and diffusivity of the permeating components. Dilution with hexane improved oil flux by 14‐fold; however, membrane selectivity was completely lost as both triacylglycerols and oleic acid permeated along with the solvent, which clearly showed that the solvent played a greater role than the membrane. Processing of the model oil after diluting with acetone showed that oleic acid was retained less than triacylglycerols by the NF membrane, resulting in higher selectivity (7), indicating its potential. However, the selectivity decreased during successive runs, owing to the gradual loss of hydrophilicity due to polarity conditioning of the membrane. The differences in molecular size, solubility, diffusivity and polarity between triacylglycerols and oleic acid appear insufficient for achieving direct deacidification in terms of reasonable selectivity and throughput with these two membranes. Direct deacidification using membranes still remains as a challenge.     

氧化石蜡乳化研究

以Co/SBA-15为催化剂,52号石蜡为原料,制备氧化石蜡,并考察了乳化温度、乳化时间、乳化剂用量等因素对乳化效果的影响.结果表明,HLB值为9.3的复配型非离子乳化剂具有较好的乳化效果.较适宜的乳化条件为:乳化剂质量分数为7.3%(占总量)、乳化时间55 min、乳化温度75 ℃、乳化用水质量分数为69.96%(占总量).制得的乳液具有稳定性好、保质期长、无毒无味、色泽好等优点.石蜡氧化后乳化性能有很大提高,乳化剂用量减少.     

石蜡无催化剂氧化工艺研究

研究了石蜡在一种氧化引发剂作用下的氧化反应工艺,考察了反应温度、空气量、反应时间、引发剂的用量、引发温度、引发时间等对石蜡氧化的影响。结果表明,石蜡氧化的最佳工艺条件是:反应温度140℃左右,反应时间6.5～7 h,引发剂用量2.0%,引发温度160℃,引发时间30 min,空气量0.5～0.75 m3/(h.kg)。在此条件下,制备出了具有良好性能、符合产品性能指标的氧化石蜡。     

石蜡乳液制备及性能研究

以高速分散器为乳化设备,58#工业级全精炼石蜡为原料制备了石蜡乳液.考察了乳化剂的组成及其HLB值,乳化剂用量,乳化温度,转速和乳化时间等因素对石蜡乳液性能的影响.结果表明,适宜的乳化工艺条件为:以Span80,K12和助乳化剂A为复配乳化剂,其HLB值为11,乳化剂用量为7％,乳化温度为85℃,转速为2×2 800 r/min,乳化时间为1min.     

氧化石蜡微乳液的研制

对氧化石蜡制备微乳液进行了研究，考察了微乳液的配方组成、乳化工艺条件及石蜡氧化改性程度对制备氧化石蜡微乳液的影响，结果表明：石蜡通过适当的氧化改性，在乳化剂D用量超过改性石蜡重量的60％，乳化温度超过改性石蜡熔化温度的条件下，可以制备氧化石蜡微乳液。     

石蜡的国内外市场

石蜡在国际市场上相对稳定，预计２０００年的需求量为３５０万ｔ，价格仍将维持在目前的水平。１９９５年我国石蜡的产量为８４．５万ｔ，预计２０００年国内需求量约６０万ｔ，出口量将达５０万ｔ     

氧化石蜡及其衍生物的研究进展

氧化石蜡是重要的化工产品,广泛应用于浮选药剂、日用化学、皮革、陶瓷等工业.随着工业技术的发展,氧化石蜡产品性能要求越来越高,氧化石蜡的改性成为当前的研究重点.本文介绍了氧化石蜡的合成工艺、改性方向,同时对氧化石蜡及其改性产品的特点和应用做了阐述.     

基于正交设计法的石蜡氧化改性研究

采用H2O2为引发剂,考察了反应温度、反应时间、引发剂加入量、空气流量和搅拌速度等因素对氧化石蜡酸值的影响,结果表明,搅拌速度和空气流量影响不大;当引发剂加入量为5%,反应温度为150℃,反应时间为8 h,空气流量为200 mL/min时,石蜡经氧化后酸值可达到32.1 mg KOH/g。经与硬脂酸作为引发剂进行比较,该改性氧化蜡具有颜色浅、气味轻等优点,可以替代天然蜂蜡制成性质稳定的乳化蜡。     

新型无催化剂石蜡氧化改性研究

分别以硬脂酸和H2O2为引发剂进行了石蜡氧化改性研究,考察了空气流量、氧化引发剂的质量分数、反应温度和反应时间对石蜡氧化过程的影响,以及反应条件对氧化石蜡性质的影响,并确定了最佳的氧化工艺条件:其中氧化温度为145~150℃,氧化时间为6~8 h。并对两种引发剂的反应效果进行了比较,其中硬脂酸效果更佳。结果表明,采用上述两种引发剂,在不添加任何催化剂的前提下,选取适当的反应条件,可以制备出酸值高、颜色浅、气味轻的氧化蜡。制得的氧化石蜡性质与天然蜂蜡相近,而且能替代天然蜂蜡制成稳定的乳化蜡。     

新型石蜡加氢精制催化剂的研制

开发了一种能适应较高空速的石蜡加氢催化剂。该催化剂具有大孔容、高比表面积、表面酸性适宜和活性组分分散性好等特点。在小型加氢精制装置上对催化剂进行了评价。结果表明，在较高空速下，该催化剂加氢活性高于国内同类催化剂，且活性稳定性好，长时间运转后，催化剂积炭量显著低于参比剂。     

添加剂对石蜡物理性能影响的研究

采用聚乙烯蜡作为石蜡改性的添加剂,考察了改性工艺条件和添加剂加入量对石蜡性能的影响。结果表明,最佳改性工艺条件为：改性时间、加热温度和搅拌速度分别为：4 h、150℃和600 r/min。聚乙烯蜡的加入可以显著改善石蜡的使用性能,在聚乙烯蜡的添加量为0~16%时,改性石蜡的滴熔点由59.2℃上升到88.2℃。采用SPSS软件进行线性回归,得出了聚乙烯蜡加入量与石蜡滴熔点、石蜡针入度（25℃）和针入度（38℃）的回归方程,石蜡滴熔点回归方程的显著性值分别为3.304E-4,9.468E-8,9.465E-7均远小于0.05。因此,可认定所建立的回归方程有效。     

Characterization of wax sediments in refined canola oils

Turbidity components in refined canola oils were collected by filtration at 4 and 20°C. Major components (thin-layer chromatography) at both temperatures were wax esters (WE), hydrocarbons (HC) and triacylglycerols (TG) while free fatty acids (FFA) and fatty alcohols (FAL) were found in minor amounts at 4°C. WE had carbon numbers of 40 to 56 (made up of combinations of C16 to C30 alcohols and C16 to C28 fatty acids). HC were mostly C29 and C31 with lesser amounts of C24, C28 and C32. TG, compared to the corresponding liquid oil, still contained C18:1 as the major component, but had less C18:2 and particularly less C18:3 and at least two times higher levels of saturated fatty acids. The FFA were mainly long-chain C22:0, C24:0 and C20:0 (in order of amount). FAL were mainly long-chain C26:0, C28:0 and C30:0 but ranged from C16:0 to C32:0. Presented in part at the 1991 American Oil Chemists’ Society Annual Meeting and Exposition, Chicago, May 15. Received Outstanding Paper Award 1991, Chicago (82nd) Annual Meeting.     

Confined crystallization of polymeric materials

The interest in confined crystallization has greatly increased with the development and progress of nanotechnology applications. Polymeric confined crystallization has been studied in droplets, ultrathin films, nanolayers, nanostructures from solutions, blends, copolymers, polymers infiltrated within AAO templates and nanocomposites. As confinement increases, the crystallization temperature first decreases, then splits into several fractions (i.e., fractionated crystallization) and finally occurs in one step at the maximum possible supercooling, near the glass transition temperature. Two factors are responsible for these effects: (a) a change in nucleation mechanism, from heterogeneous nucleation to surface nucleation (or in extreme cases, homogeneous nucleation), (b) the dependence of the crystallization temperature on the volume or the surface (or interphase) of the crystallizable micro or nanodomains. The melting point also decreases with confinement but to a lesser degree. A preferential orientation of polymeric crystals is generally induced by one or two dimensional confinement. Avrami indexes decrease with confinement until values of 1 (or even lower) are achieved in the limit of isolated domains, as the material approaches a first order crystallization kinetics. This type of kinetics reflects that nucleation is the rate determining step in the overall crystallization of ideally confined polymers.     

Surface hydrophobicity alteration of fractionated paraffin wax, crude by-product polyolefin wax and their blend

The surface compositions of crude by-product polyolefin wax (wax K) from a naphtha cracking unit, fractionated commercial paraffin wax (wax J) and their blend (wax M) were compared, under various conditions, by using FT-IR. Then a practical criterion was theoretically derived by back-of-the-envelope-calculation to estimate the diffusivity for the surface enrichment of hydrophilic functional groups. The hydrophobicity in terms of chemical structure and functional groups was altered by changing the environment as well as by blending wax K with wax J. The surface properties of wax J and wax M turned out more hydrophobic than that of wax K within the experimental period of water-submerged condition, even though the structure and functional groups on the surfaces of all waxes under ambient atmospheric condition are extremely similar. Thus the blend of wax M behaved unlike wax K but similarly to wax J in terms of alteration of hydrophobicity. Such values of diffusivity as 1.35×10⁻¹¹ cm²/s and 1.96×10⁻¹¹ cm²/s are established for wax J and wax M, respectively, under 1 day water-submerged condition. Furthermore, under 1 week water-submerged condition, the values of their diffusivity for wax J, wax K and wax M are estimated as 3.06×10⁻¹² cm²/s, 7.23×10⁻¹¹ cm²/s and 1.50×10⁻¹¹ cm²/s, respectively. The obtained values of diffusivity are consistent, in terms of the order of magnitude, with the value of diffusion coefficient of 5.75×10⁻¹¹ cm²/s obtained, using a very complicated empirical-formula, by Chen et al. for the investigation of surface-modifier enrichment. Thus, the suggested criterion may be very useful and practically applied to clarify the process of surface enrichment from general polymer-blends.