bài giảng đại cương về polymer

1. Chất dẻo a) Định nghĩa: chất dẻo là những vật liệu polime có tính dẻo, tức là có khả năng bị biến dạng dưới tác dụng bên ngoài và giữ được biến dạng sau khi ngừng tác dụng. b) Thành phần: - Thành phần cơ bản: là 1 polyme nào đó. Ví dụ thành phần chính của êbônit là cao su, của xenluloit là xenlulozơ nitrat, của bakelit là phenolfomanđehit. - Chất hoá dẻo: để tăng tính dẻo cho polime, hạ nhiệt độ chảy và độ nhớt của polime. Ví dụ đibutylphtalat,… - Chất độn: để tiết kiệm nguyên liệu, tăng cường một số tính chất. Ví dụ amiăng để tăng tính chịu nhiệt. - Chất phụ: chất tạo màu, chất chống oxi hoá, chất gây mùi thơm. c) Ưu điểm của chất dẻo: - Nhẹ (d = 1,05 ¸ 1,5). Có loại xốp, rất nhẹ. - Phần lớn bền về mặt cơ học, có thể thay thế kim loại. - Nhiều chất dẻo bền về mặt cơ học. - Cách nhiệt, cách điện, cách âm tốt. - Nguyên liệu rẻ. d) Giới thiệu một số chất dẻo. - Polietilen (P.E) : Điều chế từ etilen lấy từ khí dầu mỏ, khí thiên nhiên, khí than đá. Là chất rắn, hơi trong, không cho nước và khí thấm qua, cách nhiệt, cách điện tốt. Dùng bọc dây điện, bao gói, chế tạo bóng thám không, làm thiết bị trong ngành sản xuất hoá học, sơn tàu thuỷ. - Polivinyl clorua (P.V.C) Chất bột vô định hình, màu trắng, bền với dung dịch axit và kiềm. Dùng chế da nhân tạo, vật liệu màng, vật liệu cách điện, sơn tổng hợp, áo mưa, đĩa hát… - Polivinyl axetat (P.V.A) Điều chế bằng cách : cho rồi trùng hợp. Dùng để chế sơn, keo dán, da nhân tạo. - Polimetyl acrilat và polimetyl metacrilat Điều chế bằng cách trùng hợp các este tương ứng. Là những polime rắn, không màu, trong suốt. Polimetyl acrilat dùng để sản xuất các màng, tấm, làm keo dán, làm da nhân tạo Polimetyl metacrilat dùng làm thuỷ tinh hữu cơ. - Polistiren Dùng làm vật liệu cách điện. Polistiren dễ pha màu nên được dùng để sản xuất các đồ dùng dân dụng như cúc áo, lươc… - Nhựa bakelit: Thành phần chính là phenolfomanđehit. Dùng làm vật liệu cách điện, chi tiết máy, đồ dùng gia đình. - Êbonit: là cao su rắn có tới 25 - 40% lưu huỳnh. Dùng làm chất cách điện. - Têflon : rất bền nhiệt, không cháy, bền với các hoá chất. Dùng trong công nghiệp hoá chất và kỹ thuật điện. 2. Cao su Cao su là những vật liệu polime có tính đàn hồi, có ứng dụng rộng rãi trong đời sống và trong kỹ thuật. a) Cao su thiên nhiên: được chế hoá từ mủ cây cao su. - Thành phần và cấu tạo: là sản phẩm trùng hợp isopren. n từ 2000 đến 15000 - Mạch polime uốn khúc, cuộn lại như lò xo, do đó cao su có tính đàn hồi. Cao su không thấm nước, không thấm không khí, tan trong xăng, benzen, sunfua cacbon. - Lưu hoá cao su: Chế hoá cao su với lưu huỳnh để làm tăng những ưu điểm của cao su như: không bị dính ở nhiệt độ cao, không bị dòn ở nhiệt độ thấp. Lưu hoá nóng: Đung nóng cao su với lưu huỳnh. Lưu hoá lạnh: Chế hoá cao su với dung dịch lưu huỳnh trong CS2. Khi lưu hóa, nối đôi trong các phân tử cao su mở ra và tạo thành những cầu nối giữa các mạch polime nhờ các nguyên tử lưu huỳnh, do đó hình thành mạng không gian làm cao su bền cơ học hơn, đàn hồi hơn, khó tan trong dung môi hữu cơ hơn. b) Cao su tổng hợp: - Cao su butađien (hay cao su Buna) Là sản phẩm trùng hợp butađien với xúc tác Na. Cao su butađien kém đàn hồi so với cao su thiên nhiên nhưng chống bào mòn tốt hơn. - Cao su isopren. Có cấu tạo tương tự cao su thiên nhiên, là sản phẩm trùng hợp isopren với khoảng 3000. - Cao su butađien - stiren Có tính đàn hồi và độ bền cao: - Cao su butađien - nitril: sản phẩm trùng hợp butađien và nitril của axit acrilic. Do có nhóm C º N nên cao su này rất bền với dầu, mỡ và các dung môi không cực. 3. Tơ tổng hợp: a) Phân loại tơ: Tơ được phân thành: - Tơ thiên nhiên: có nguồn gốc từ thực vật (bông, gai, đay…) và từ động vật (len, tơ tằm…) - Tơ hoá học: chia thành 2 loại. + Tơ nhân tạo: thu được từ các sản phẩm polime thiên nhiên có cấu trúc hỗn độn (chủ yếu là xenlulozơ) và bằng cách chế tạo hoá học ta thu được tơ. + Tơ tổng hợp: thu được từ các polime tổng hợp. b) Tơ tổng hợp: - Tơ clorin: là sản phẩm clo hoá không hoàn toàn polivinyl clorua. Hoà tan vào dung môi axeton sau đó ép cho dung dịch đi qua lỗ nhỏ vào bể nước, polime kết tủa thành sợi tơ. Tơ clorin dùng để dệt thảm, vải dùng trong y học, kỹ thuât. Tơ clorin rất bền về mặt hoá học, không cháy nhưng độ bền nhiệt không cao. - Các loại tơ poliamit: là sản phẩm trùng ngưng các aminoaxit hoặc điaxit với điamin. Trong chuỗi polime có nhiều nhóm amit - HN - CO - : + Tơ capron: là sản phẩm trùng hợp của caprolactam + Tơ enan: là sản phẩm trùng ngưng của axit enantoic + Tơ nilon (hay nilon): là sản phẩm trùng ngưng hai loại monome là hexametylđiamin và axit ađipic : Các tơ poliamit có tính chất gần giống tơ thiên nhiên, có độ dai bền cao, mềm mại, nhưng thường kém bền với nhiệt và axit, bazơ. Dùng dệt vải, làm lưới đánh cá, làm chỉ khâu. - Tơ polieste: chế tạo từ polime loại polieste. Ví dụ polietylenglicol terephtalat. Tơ lapsan rất bền cơ học, bền An ion-exchange resin or ion-exchange polymer [1] is an insoluble matrix (or support structure) normally in the form of small (1–2 mm diameter) beads, usually white or yellowish, fabricated from an organic polymer substrate. The material has highly developed structure of pores on the surface of which are sites with easily trapped and released ions. The trapping of ions takes place only with simultaneous releasing of other ions; thus the process is called ion-exchange. There are multiple different types of ion- exchange resin which are fabricated to selectively prefer one or several different types of ions. Ion exchange resin beads Ion-exchange resins are widely used in different separation, purification, and decontamination processes. The most common examples are water softening and water purification. In many cases ion-exchange resins were introduced in such processes as a more flexible alternative to the use of natural or artificial zeolites. Most typical ion-exchange resins are based on crosslinked polystyrene. The required active groups can be introduced after polymerization, or substituted monomers can be used. For example, the crosslinking is often achieved by adding 0.5-25% of divinylbenzene to styrene at the polymerization process. Non-crosslinked polymers are used only rarely because they are less stable. Crosslinking decreases ion- exchange capacity of the resin and prolongs the time needed to accomplish the ion exchange processes. Particle size also influences the resin parameters; smaller particles have larger outer surface, but cause larger head loss in the column processes. Besides being made as bead-shaped materials, ion exchange resins are produced as membranes. The membranes are made of highly cross-linked ion exchange resins that allow passage of ions, but not of water, are used for electrodialysis. There are four main types differing in their functional groups: • strongly acidic (typically, sulfonic acid groups, e.g. sodium polystyrene sulfonate or polyAMPS) • strongly basic, (quaternary amino groups, for example, trimethylammonium groups, e.g. polyAPTAC) • weakly acidic (mostly, carboxylic acid groups) • weakly basic (primary, secondary, and/or ternary amino groups, e.g. polyethylene amine) There are also specialised types: • chelating resins (iminodiacetic acid, thiourea, and many others) Contents [hide] • 1 Uses o 1.1 Water softening o 1.2 Water purification o 1.3 Production of high purity water o 1.4 Ion-exchange in metal separation o 1.5 Catalysis o 1.6 Juice Purification o 1.7 Sugar Manufacturing o 1.8 Pharmaceuticals • 2 See also • 3 Notes • 4 Sources [edit] Uses [edit] Water softening Main article: Water softening In this application, ion-exchange resins are used to replace the magnesium and calcium ions found in hard water with sodium ions. When the resin is fresh, it contains sodium ions at its active sites. When in contact with a solution containing magnesium and calcium ions (but a low concentration of sodium ions), the magnesium and calcium ions preferentially migrate out of solution to the active sites on the resin, being replaced in solution by sodium ions. This process reaches equilibrium with a much lower concentration of magnesium and calcium ions in solution than was started with. The resin can be recharged by washing it with a solution containing a high concentration of sodium ions (e.g. it has large amounts of common salt (NaCl) dissolved in it). The calcium and magnesium ions migrate off the resin, being replaced by sodium ions from the solution until a new equilibrium is reached. This is the method of operation used in dishwashers that require the use of 'dishwasher salt'. The salt is used to recharge an ion-exchange resin which itself is used to soften the water so that limescale deposits are not left on the cooking and eating utensils being washed. [edit] Water purification In this application, ion-exchange resins are used to remove poisonous (e.g. copper) and heavy metal (e.g. lead or cadmium) ions from solution, replacing them with more innocuous ions, such as sodium and potassium. Few ion-exchange resins remove chlorine or organic contaminants from water - this is usually done by using an activated charcoal filter mixed in with the resin. There are some ion-exchange resins that do remove organic ions, such as MIEX (magnetic ion-exchange) resins. Domestic water purification resin is not usually recharged - the resin is discarded when it can no longer be used. [edit] Production of high purity water Water of highest purity is required for electronics, scientific experiments, production of superconductors, and nuclear industry, among others. Such water is produced using ion- exchange processes or combinations of membrane and ion-exchange methods. Cations are replaced with hydrogen ions using cation-exchange resins; anions are replaced with hydroxyls using anion-exchange resins. The hydrogen ions and hydroxyls recombine producing water molecules. Thus, no ions remain in the produced water. The purification process is usually performed in several steps with "mixed bed ion-exchange columns" at the end of the technological chain. [edit] Ion-exchange in metal separation Ion-exchange processes are used to separate and purify metals, including separating uranium from plutonium and other actinides, including thorium; and lanthanum, neodymium, ytterbium, samarium, lutetium, from each other and the other lanthanides. There are two series of rare earth metals, the lanthanides and the actinides, both of which families all have very similar chemical and physical properties. Ion-exchange is the only practical way to separate them in large quantities. This application was developed in the 1940's by Frank Spedding. A very important case is the PUREX process (plutionium-uranium extraction process) which is used to separate the plutonium and the uranium from the spent fuel products from a nuclear reactor, and to be able to dispose of the waste products. Then, the plutonium and uranium are available for making nuclear-energy materials, such as new reactor fuel and nuclear weapons. The ion-exchange process is also used to separate other sets of very similar chemical elements, such as zirconium and hafnium, which incidentally is also very important for the nuclear industry. Zirconium is practically transparent to free neutrons, used in building reactors, but hafnium is a very strong absorber of neutrons, used in reactor control rods. [edit] Catalysis In chemistry ion-exchange resins are known to catalyze organic reactions. See for instance self-condensation. [edit] Juice Purification Ion-exchange resins are used in the manufacture of fruit juices such as orange juice where they are used to remove bitter tasting components and so improve the flavor. This allows poorer tasting fruit sources to be used for juice production. [edit] Sugar Manufacturing Ion-exchange resins are used in the manufacturing of sugar from various sources. They are used to help convert one type of sugar into another type of sugar, and to decolorize and purify sugar syrups. [edit] Pharmaceuticals Ion-exchange resins are used in the manufacturing of pharmaceuticals, not only for catalyzing certain reactions but also for isolating and purifying pharmaceutical active ingredients. Three ion-exchange resins, sodium polystyrene sulfonate, colestipol, and cholestyramine, are used as active ingredients. Sodium polystyrene sulfonate is a strongly acidic ion-exchange resin and is used to treat hyperkalemia. Colestipol is a weakly basic ion-exchange resin and is used to treat hypercholesterolemia. Cholestyramine is a strongly basic ion-exchange resin and is also used to treat hypercholesterolemia. Colestipol and cholestyramine are known as bile acid sequestrants. Ion-exchange resins are also used as excipients in pharmaceutical formulations such as tablets, capsules, and suspensions. In these uses the ion-exchange resin can have several different functions, including taste-masking, extended release, tablet disintegration, and improving the chemical stability of the active ingredients. [edit] See also • Ion exchange [edit] Notes 1. ^ IUPAC "strongly discourages" the use of the term 'ion-exchange resin' to refer to an ion-exchange polymer, but it remains very common: International Union of Pure and Applied Chemistry (2004), "Definitions of Terms Relating to Reactions of Polymers and to Functional Polymeric Materials (IUPAC Recommendations 2003)", Pure Appl. Chem. 76 (4): 889–906, http://media.iupac.org/publications/pac/2004/pdf/7604x0889.pdf [edit] Sources • http://www.remco.com/ix.htm • http://www.dow.com/liquidseps/service/ix_techinfo.htm • F. Helfferich, Ion Exchange, McGraw Hill, New York, 1962 (Bible of the subject). • Ion Exchangers (K. Dorfner, ed.), Walter de Gruyter, Berlin, 1991. • C. E. Harland, Ion exchange: Theory and Practice, The Royal Society of Chemistry, Cambridge, 1994. • Ion exchange (D. Muraviev, V. Gorshkov, A. Warshawsky), M. Dekker, New York, 2000. • A. A. Zagorodni, Ion Exchange Materials: Properties and Applications, Elsevier, Amsterdam, 2006. Retrieved from "http://en.wikipedia.org/wiki/Ion-exchange_resin" Categories: Polymers | Water | Synthetic resins | Polyelectrolytes Polymer Solutions by Susana B. Grassino The importance assigned to polymer solutions, a topic whose discussion has evolved from a mere informative mention in textbooks to whole books exclusively devoted to that subject, has become increasingly notorious. The reasons are based on key factors. In the first place, the understanding of the behavior and both physical and chemical properties of macromolecules has been mainly sustained in studies carried out in solution, like for example the determination of the relative molecular mass, made by viscometry or gel permeation chromatography (GPC). On the other hand, since polymer solutions are highly viscous even at low concentrations, their commercial application includes a wide range of products, from paintings to processed foods. Therefore, we can then consider polymer solutions as liquid mixtures made of long macromolecular chains, and small, light molecules of solvent (Grosberg and Khokhlov, 1997). This, by the way, is not a usual situation. The large size of this [...]... value This point, where polymer- solvent and polymer- polymer interactions are of the same magnitude, is known as θ state and depends on: the temperature, the polymer- solvent system (where ∆H is mainly affected) and the molecular weight of the polymer (where ∆S is mainly affected) It may be inferred then, that lowering the temperature or the solvent quality, the separation of the polymer in decreasing... the polymer- solvent interactions are higher than the polymer- polymer attraction forces, the chain segment start to absorb solvent molecules, increasing the volume of the polymer matrix, and loosening out from their coiled shape (Figure 1b) We say the segments are now "solvated" instead of "aggregated", as they were in the solid state Figure 1 Schematic representation of the dissolution process for polymer. .. of Polymers" / John W Nicholson, Royal Society of Chemistry, Cambridge, UK, 1991 • "Fundamental Principles of Polymeric Materials" / Stephen L Rosen, Series: SPE Monographs, John Wiley & Sons, New York, 1982 • "Textbook of Polymer Science" / Fred W Billmeyer, Jr., 2nd Ed., WileyInterscience, New York, 1971 • "Principles of Polymer Chemistry" / Paul J Flory, Cornell University Press, Ithaca, 1953 • "Polymer. .. the dissolution behavior shown by polymers Due to their size, coiled shape, and the attraction forces between them, polymer molecules become dissolved quite slowly than low molecular weight molecules Billmeyer Jr (1975) points out that there are two stages involved in this process: in the first place, the polymer swelling, and next the dissolution step itself When a polymer is added to a given solvent,... longer suitable to evaluate the contribution of each macromolecule in particular To learn more about Polymer Solutions, just click on any of the following links: Summary  What Is "Solubility" And What It Depends On  How a Polymer Gets Dissolved  Thermodynamic Considerations For Polymer Solubility  How Polymers Behave In Dilute Solutions  Statistical Parameters  How Can You Measure The Statistic Parameters?... takes a long time, and given it is influenced only by the polymer- solvent interactions, stirring plays no role in this case However, it is desirable to start with fine powdered material, in order to expose more of their area for polymer- solvent interactions When crystalline, hydrogen bonded or highly crosslinked substances are involved, where polymer- polymer interactions are strong enough, the process does... molecules filling the empty space between the loosen segments Hence, the polymer coil, along with solvent molecules held within, adopts a spheric or ellipsoid form, occupying a volume known as hydrodynamic volume of the polymer coil (Figure 1c) The particular behavior shown by polymer molecules, explains the high viscosity of polymer solutions Solvent and low molecular weight solutes have comparable... useful when studying how capable is a polymer to being dissolved in a given solvent However, it should be pointed out that equation [3] is valid only for solutions where strong polymer- solvent interactions do not take place Numerous tables showing solubility parameters for both solvent and polymers have been published Some examples are detailed below Solvent δ s (MPa1/2) Polymer δ p (MPa1/2) Acetone 20.3... Polystyrene 17.4-21.1 Water 47.9 Nylon 6.6 27.8 Table 1 Solubility parameters for solvents and polymers more commonly used (Taken from "Polymer Handbook" / J Brandrup and E.H Immergut, Eds., 3rd Ed., WileyInterscience, New York, 1989) In absence of specific polymer- solvent interactions, it has been established that, for a polymer to be dissolved in a given solvent, the term (δ s - δ p)2 in equation [3], must... that of the polymer, the attraction forces between chain segments are smaller than the polymer- solvent interactions; the random coil adopts then, an unfolded conformation In a "poor" solvent, the polymer- solvent interactions are not favored, and therefore attraction forces between chains predominate, hence the random coil adopts a tight and contracted conformation In extremely "poor" solvents, polymer- solvent . parameter. If the polymer- solvent interactions are higher than the polymer- polymer attraction forces, the chain segment start to absorb solvent molecules, increasing the volume of the polymer matrix,. "http://en.wikipedia.org/wiki/Ion-exchange_resin" Categories: Polymers | Water | Synthetic resins | Polyelectrolytes Polymer Solutions by Susana B. Grassino The importance assigned to polymer solutions, a topic whose discussion. case of polymers. Thus, polar macromolecules like poly (acrylic acid), poly (acrylamide) and polyvinyl alcohol, among others, are soluble in water. Conversely, nonpolar polymers or polymer