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101.
The production of porous polymeric particles is attractive for a large number of applications and can be achieved by various techniques. Although numerous production schemes exist for glassy polymers, difficulties arise for soft, rubbery materials that need a chemical crosslinking step, such as elastomers. This is particularly true for poly(dimethylsiloxane) (PDMS), which shows the lowest glass‐transition temperature among the polymers. Recent studies suggest in situ hydrogen bubble formation or vacuum drying of water droplets dispersed in the polymer matrix in order to generate porous PDMS structures. In this work we report early results based on the chemical crosslinking of water in PDMS emulsion droplets in a mechanically stirred thermostated water vessel. This approach is shown to lead to high porosity PDMS beads (ca. 10?3 m particle diameter) with an open structure whose properties (diameter and porosity) are strongly influenced by the starting composition (solvent, surfactant, and polymer types and ratios), as well as the operating parameters (agitation and temperature). The possible uses of these derived beads are discussed. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 967–971, 2002 相似文献
102.
特超稠油污水回掺降粘集输工艺 总被引:4,自引:1,他引:3
通过对河南古城油田BQ10区特超稠油乳状液的室内试验分析,指出该种乳状液的实际相突变点为68%左右,当相浓度Φ≥68%时,以W/O型为主的乳状液突变为以O/W型为主的乳状液.乳状液变型后,原油与管道内壁之间的摩擦以及原油之间的摩擦转变为水与管道内壁及水与水之间的摩擦,从而大幅度降低其粘度和摩阻损失;通过对古城BQ10区特超稠油区块单元内部污水回掺降粘集输的现场试验,证明与室内试验分析得出的结论相符合,说明区块单元污水回掺不同于常规的掺热水,也不同于掺联合站处理过的净化污水,它优于单井掺稀油.最后指出该工艺可有效地降低井站回压,方便生产管理,降低开采成本,提高采油效率和经济效益,具有低耗节能的优点. 相似文献
103.
Flory–Huggins interaction parameters, λ, were determined for a series of probes in an amine cured epoxy resin matrix (433–493 K) and its precursors (324–363 K) by inverse gas chromatography (IGC). Hildebrand–Scatchard theory was combined with Flory–Huggins theory in order to estimate infinte dilution solubility parameters (δ2) for the matrix and its precursors at 298 K. It was shown that the value of the solubility parameter for the cured resin matrix lies between those of its precursors. Compared to the majority of published work, an unusual aspect of this application of IGC is that solubility parameters have been determined when the stationery phases are (i) small molecules and (ii) a highly crosslinked polymer. Moreover, all possible attempts have been made to ensure equilibrium conditions between probe and stationary phase, and compensation for asymmetry of peak profile has been applied in determining δ2. The solubility parameters estimated by IGC are in good agreement with those calculated by other methods. 相似文献
104.
HPVC/PP共混改性研究:Ⅲ低分子量反应性化合物作相容剂 总被引:3,自引:0,他引:3
采用低分子量反应性化合物作相容剂,即化学交联体系来改善HPVC/PP共混物的相容性。考察了在不同共混比下,不同化学交联体系对共混物力学性能的影响,并观察了共混物的微观形态。结果表明,采用低分子量反应性化合物作相容剂,共混物的拉伸强度提高,但冲击强度无改善。分散相尺寸减小,相间粘接得到改善。并比较了3种增容方法的效果,发现CPE是HPVC/PP共混物的最佳相容剂。 相似文献
105.
本文讨论了温度、搅拌和时间三要素对感光乳剂和工艺过程的影响,指出了上述影响的后果和严格过程控制的重要性,提出克服影响的措施。 相似文献
106.
In the paper the control of the product quality in polymerization reactors is analysed in the presence of persistent perturbations (unmodeled disturbances, modeling errors), as met in industrial reactors. The free radical polymerization of methyl-methacrylate in a continuous stirred tank reactor is studied. It is shown that state estimators (Extended Kalman Filters) with constant parameters cannot give offset free performance. Criteria for the selection of a set of parameters to be updated as additional states in the filter and to evaluate their effectiveness in opposing the action of realistic perturbations are given by an analysis of the linearized model of the system. Performance of different types of estimators, including one and two-time scale filters, with and without updating of parameters, is analysed by simulation on the full order process and the predictions made by previous analysis are confirmed. In the most common case of presence of perturbations affecting the energy balance and the concentration of initiator in the reactor, offset free control of the molecular weight of the product can be achieved by means of a filter which is based only on measurements of temperature and conversion and makes an update of two parameters. In the case that also the kinetic model of the polymerization reaction is affected by errors, a two-time scale filter, which makes use also of Molecular Weight values and updates three parameters, becomes necessary to obtain offset free performance. 相似文献
107.
Ziegler-Natta烯烃聚合催化剂进展 总被引:1,自引:0,他引:1
综述了Ziegler-Natta催化剂在乙烯聚合和丙烯聚合方面的研究开发现状,重点介绍了采用新型二醚化合物作为内给电子体的丙烯聚合催化剂的进展。随着合成树脂向功能化方向发展,开发综合性能优越的新型催化剂及给电子体将是今后的研究方向。 相似文献
108.
Polyurethanes were prepared from pure 4,4′-diphenylmethane diisocyanate (MDI), 1,4-butane diol (BDO) or 1,2-ethane diol (EDO) and α,ω-hydroxyl poly(propylene oxide) (PPO) by reaction injection moulding (RIM). Hard segment (MDI + BDO or EDO) level was 45–50 wt%. The PPO had about 20% ethylene oxide copolymerized in at the chain ends to provide 80% primary OH end groups. Mn was varied from 2000 to 4000. Dibutyl tin dilaurate catalyst and mould temperature were varied. Dynamic mechanical, wide-angle X-ray, differential scanning calorimeter, molecular weight and tensile elongation measurements were made on the RIM polyurethanes. At low reaction rates (low catalyst or temperature) highly crystalline, well phase separated but low molecular weight polymers were produced. At high catalyst or temperature levels more poorly phase separated but high molecular weight, tough polymers resulted. Higher Mn PPO gave better phase separation and EDO gave higher melting temperatures. Preventing hard segment crystallinity by substituting asymmetric MDI or glycols resulted in phase compatibility. 相似文献
109.
叠前地震数据的规则化 总被引:6,自引:1,他引:5
本文通过对动校正前积分法DMO原理的探讨,在借鉴Canning(1996)提出的利用DMO实现三维数据规则化的方法和Biondi(1998)提出的三维叠前地震数据方位角校正方法的基础上,从方位角校正的角度入手,利用DMO和DMO^-1相结合的处理流程对地震数据进行规则化,以得到新的规则的观测系统下具有所需特定方位角的观测数据。此方法可用于解决叠前地震数据道插值、陆上地震勘探中不规则观测数据的规则化和海上地震勘探中的羽状现象校正等问题,可将已有地震观测数据转变为特定观测系统的叠前地震数据,以便于某些处理方法的应用。此方法原理简单并具有广泛的适用性。 相似文献
110.