高分子材料工程专业英语课后材料文章Reading Materials.doc

嘉兴学院 高分子系 吴佰程整理Reading Materials第6单元Purification of Polymers聚合物的提纯The usual purification operations used with low molecular weight compounds (for example, distillation and recrystallization) are usually not applicable to macromolecular compounds.针对低分子量化合物通常的提纯方法，如蒸馏和重结晶通常都不能用于高分子化合物。Distillation, 蒸馏Macromolecular compounds are not volatile and cannot simply be recrystallized from saturated solutions. One therefore has to be satisfied with extracting them in suitable solvents and thus removing the impurities.Volatilevoltail, 飞行的，易挥发的，快活的，爆炸性的，易激动的，反复无常的，短暂的。Extract, v，萃取，extraction, 萃取高分子化合物不是挥发性的，而且不能简单地从饱和溶液中再结晶。因此人们不得不用合适的溶剂来萃取这些高分子，从而去除杂质。The purification effect of the extraction is in most cases rather slight because in many instances the impurity is held to the polymer by strong secondary valence forces. Secondary valence force, 次（化合）价力Hold to 坚持，紧握在大多数场合，萃取的提纯效果是很有限的，因为在许多情况下杂质被聚合物强的次价力束缚。Consequently, one usually first dissolves the macromolecular compound and then precipitates it by addition of a nonsolvent. 因此，我们通常首先溶解高分子化合物，然后用非溶剂填加物把高分子沉淀下来。Precipitate，沉淀The precipitate comes out as a more or less strongly swollen gel. Come out，长出，（花）开，由。产生，由。出来，结果是，显现，（污点）被去掉，（颜色）被褪去，（题目）被解出，（商品）被展出，被供应，（总数）计，总计Swell，溶胀，gel，凝胶，溶胶，sol，溶胶-凝胶法，sol-gel沉淀大体上以强烈溶胀的凝胶形式产生出来。And the impurities remain at least partly in solution. 而杂质至少有一部分保留在溶液中。The gel can be removed by sedimentation if necessary, in the centrifuge. 如果需要的话，凝胶可以用离心机沉降移出。Usually it is necessary to repeat this precipitation 10-20 times. 通常这个沉淀过程有必要重复10到20次。The solvents and precipitating agents have to be carefully selected from case to case. 根据不同场合，溶剂和沉淀剂必须仔细选择。Many vinyl polymers are easily dissolved in benzene and toluene and precipitate under addition of methanol. Toluence，甲苯Methanol，甲醇许多乙烯基聚合物容易溶解在苯或甲苯中，而在添加甲醇的情况下发生沉淀。Methanol is a sort of general precipitating agent in which most polymers, both the benzene soluble ones and the water-soluble polymers, are insoluble. 甲醇是一种常见的沉淀剂，无论是苯溶还是水溶聚合物，大多数聚合物在甲醇里是不溶解的。Since methanol is miscible in all proportion both with benzene and with most other organic solvents and also with water, it can be used as a precipitant in both cases, i.e., with organic and with aqueous polymer solutions.Miscible, 可混溶的，miscibility，相溶性（分子层面上的混溶）compatible,相容的， Compatibility,相容性（相层面上的混溶）因为甲醇与苯等有机溶剂，与水都可以所有的比例混溶的。在有机和水的高分子溶液中，甲醇可以用来做沉淀剂。One has to expect that the polymers is somehow affected by the extraction, regardless of whether this is done by heating or by precipitation. 聚合物受萃取过程的影响是肯定的，不管这个过程是通过加热还是沉淀。Thus if one extracts with acids or bases, hydrolytic degradation usually causes a lowering in the degree of polymerization (for example, hydrolytic degradation of polysaccharides). Hydrolytic, 水解的，Degradation, 降解反应。Polysaccharide, 多糖，聚糖因此如果我们用酸或碱来萃取，水解降解反应通常导致聚合度降低，如聚糖的水解。In the process of dissolving and reprecipitation, one usually finds that low molecular weight components remain in solution (fractionation), and therefore the precipitated part has a higher average molecular weight and more uniform molecular weight distribution.Uniform, （尺寸、大小，形状等）均一的，distribution,分布在溶解和再沉淀过程中，通常我们发现低分子量组分保留在溶液中（分级），因此，沉淀部分具有高的平均分子量，而且分子量分布更均一。This may or may not be desirable, but in any case one should be aware of it.这可能和我们的意，也可能不合我们的意，但是，无论什么情况，我们都应该知道这一点。With synthetic polymers, purification may be avoided sometimes by choosing a method of synthesis where the polymer is immediately obtained in pure form. 对合成聚合物而言，提纯过程有时是可以避免的。通过选择合成方法，我们可以很快得到纯的聚合物， Usually an extreme purification of the monomer is simpler and more effective than a later purification of the polymer. 通常单体的最大程度的提纯比聚合物后提纯更简单，而且也更有效。Initiators and other additives, such as emulsifying agents and protective colloids, are also selected wherever possible in a such way that they can remain in the polymer without causing problems.引发剂和其他添加剂，如乳化剂和保护胶体，也可以保留在聚合物中任何可能的地方而不至于带来麻烦。Emulsify, 乳化， Protective colloid, 保护胶体。 Dispersions, as obtained by emulsion polymerization, can be coagulated or precipitated by the addition of electrolytes. Dispersion, 分散相，分散体系. Emulsion polymerization, 乳液聚合Coagulate, 凝结. Electrolyte, 电解质从乳液聚合得到的分散相可以通过添加电解质而凝结或沉淀。Formic acid or sodium chloride is used most often. 甲酸或氯化钠是最常用的电解质。The purification effectiveness of such a precipitation is rather incomplete, because the emulsifying agents are not completely removed; their content is only lowered. 这样一个沉淀的提纯效果是相当不完全的，因为尽管含量很低，乳化剂没有完全被去除掉。However, even this is often sufficient to make precipitation of the polymer dispersion preferable to a direct drying on the mill or by spraying. Mill, 研磨机。 Spray, 喷雾然而，在研磨机上或喷雾方式直接干燥是经常使用的聚合物分散相沉淀的制备方法。Polymer dispersions can also often be precipitated and purified by pouring them into methanol, by adding methanol, or by cooling the dispersion in some kind of a cooling mixture (-20 to -40).聚合物分散相也经常被沉淀或提纯，如把高分子倒入到甲醇里，向高分子分散相添加甲醇，或通过用某种冷却混合物（20-40度）冷却分散相的方法。Of special importance is the purification of natural macromolecular compounds. 天然高分子化合物的提纯是很重要的。These usually contain low molecular weight materials or other macromolecular compounds, and in some cases there is even a chemical combination between the different compounds; for example, cellulose with lignin (in wood), or pectins ( in flax). 天然高分子通常包含低分子量材料或其他大分子化合物，而且在一些情况下，甚至在不同的化合物之间存在化学结合，如纤维素和木质素（在木材里），或果胶（在亚麻纤维）。Cellulose, 纤维素Lignin，木质素Pectin，果胶Flax，亚麻纤维In such cases it is justified to consider this combination as a new macromolecular substance. 在这个情况下，证实了这个结合产生了新的高分子物质。Since it is usually not possible to isolate the macromolecules without chemical reaction and therefore usually one does not obtain them in an unchanged form, one does not give these compounds a proper name but calls them propopectin or protocellulose, etc. Isolate, 隔离，析出，绝缘Propopectin, 原果胶Protocellulose,原纤维素因为没有化学反应而析出高分子通常是不可能的，因此不改变形式的大分子是不可能得到的。我们不能给这些化合物一个恰当的名字，而只是称它们为原果胶或原纤维素等。the isolation of the pure compounds (pectin or cellulose) can be brought about by acid, or alkaline, or enzymatic hydrolysis (wood pulp by the sulfite process or by alkali treatment).Bring about, 带来，造成Pulp，浆状物，wood pulp,木浆Sulfite，亚硫酸盐通过酸，或强碱，或酶催化水解（木浆被亚硫酸盐化过程，或被碱处理），可以让纯的化合物析出。Low molecular weight impurities (for example, residues or solvents or monomers) can usually be removed by heating in vacuum. Residue, 残余物低分子量杂质（如残留物或溶剂或单体）通常可以通过真空加热的方法去除掉。Since one cannot mix the molten polymer in some kind of a stirred vessel, (because of its high viscosity) one has to use special techniques and apparatuses, depending on the polymer. Stir, 移动，摇动，搅拌，激动Vessel, 容器因为我们不能混合在某种搅拌容器中的熔融高分子，（因为它的高粘度），根据高分子的不同，我们必须使用特殊的技术和设备。Macromolecular substances with a high softening point (over 100) can often be dried in the form of a powder or in granules. Granule, 颗粒，细粒具有高软化点（超过100度）的高分子物质常常可以在粉末或细粒状态下进行干燥。This is done by spreading them out in a vacuum oven and heating them usually with an infrared lamp. 我们可以把这些高分子物质散播在真空炉中而且用红外灯加热。If the materials which is to be removed is volatile only at a temperature which it is higher than the softening point of the polymer, one can use certain extruders in which it is possible to apply vacuum at certain places along the machine and thereby remove the solvent. 如果该可去除的材料仅仅在高于聚合物软化点以上的温度下是挥发性的，我们可以使用某种挤出机，沿着该机器的某个地方可以应用真空而去除溶剂。In such vacuum extruders (welding machine) one can treat thermoplastic materials, such as polystyrene or polymethylmethacrylate (at 180 to 250). 用这样的真空挤出机（焊接机），我们可以处理如聚苯乙烯或聚甲基丙烯酸甲酯这样的热塑性材料As a result of constant renewing of surface by the milling process in the vacuum-zones of the extruder, a very rapid and effective removal of the volatile compounds is obtained. Renew, 修复，重复，更新. Zone,区，带，层在挤出机真空区用研磨工艺对聚合物进行恒定的表面更新，我们就可以非常迅速而有效地去除挥发性化合物。Great care must be taken in the isolation of proteins from their aqueous solutions because they usually degenerate even at rather low temperatures. 蛋白质从水溶液中析出需要特色小心，因为蛋白质即使在相当低的温度下也常常发生退化。Such solutions can often be concentrated by freeze-drying. 这样的溶液常常用冷冻干燥的方法得到浓缩。This is done by bringing the surface of the solution in close contact with a cold condenser and applying high vacuum to the entire apparatus so that the water from the solution forms as ice on the condenser. 通过让溶液表面与冷凝器接触，并把高真空用于整个设备的方法，使水从溶液变成冰。The solution to be concentrated can be in a frozen state during this process.在这个过程中，被浓缩的溶液可以处于冷冻状态。Low molecular weight impurities which are not volatile, such as inorganic salts in natural products, can be removed by dialysis, or eletrodialysis, of the polymer solution.不具有挥发性的低分子量杂质，如天然产品中的无机盐可以通过渗析法，电渗析法从高分子溶液中去除。Dialysis,渗析 The separation of different macromolecular compounds which are present in the mixture is particularly difficult. 在混合物中的不同高分子的分离是相当困难的。This is especially so if the solubility is the same, so that extraction or precipitation does not bring about a separation. 如果特殊到溶解性相同，那么用萃取或沉淀方法不能分离它们。This problem is often encountered in protein chemistry. 在蛋白质化学中，这个难题是经常遇到的。Since the protein molecules are usually present in the solution in the form of ions, one can use the difference in their rate of diffusion in an electric f