聚合物的降解与稳定化

聚合物稳定与降解（Polymer stability and degradation）The first chapter, introduction1. the concept of aging (degradation)The storage, processing and use of polymer materials in the process of chemical properties, physical and mechanical properties will gradually become worse, known as aging or degradation. P1Characteristic：The inevitable, irreversible process.The relatively short time scale.2. factors that lead to the degradation of the polymer(a) internalThe composition and structure of A. polymer chain.(1) different composition and degradation of different(2) the activity may be the main cause of the degradation of the matrix(3) the active hydrogen is more likely to be seized(4) head to head (tail tail) structure of polyolefin are more likely to become active points.(5) the effect of molecular weight change: changes in the structure of the molecular weight of the internal rules increases, causing stability. On the contrary, if the irregular structure is reduced, increased stability.(6) effects of the molecular weight distribution: down a wide molecular weight distribution and stability.(7) the degree of branching effect: the degree of branching increases, the weak link in the molecular chain also increased, more prone to degradation.The aggregation state of B. polymersThe stability of amorphous polymer material less than crystalline polymer materialsThe reason: amorphous materials (low density polymer chain irregular arrangement), easy to be oxygen, water, chemical infiltration, degradation.3. impurities in polymersIn the two kinds of polymer impurity:(1) a small amount of impurities mixed in the process of the inevitable;(2) additive.Most of the impurities will accelerate the degradation of polymers.(two) external causes:Effects of A. heat, temperature and heat and oxygen: heat the polymer chain scission, the formation of free radicals (reversible, bidirectional) hot oxygen polymer crosslinking or degradation of the material performance decline.Effect of B. lightEffect of C. oxygen and ozone oxygen to polymer degradation in heat and light effect. The ozone of unsaturated bond (such as rubber) the damage is very serious.Effect of D. water and damp of water dissolving and extraction of components; hydrolysis and chain scission.Effect of E. and other factors: the effect of microorganism; other organisms; effects of various process factors. Often a variety of external synergy.The second chapter, the basic principle of polymer degradation and stability.(a) the type of thermal degradationDepolymerization; random chain scission reaction; small molecular chain breaking elimination reaction;Features: simple caused by heat, no oxygen in.1. the depolymerization reaction (zipper degradation)The depolymerization began or weak molecular chain end point. Only product: monomer.Characteristic：(1) the early change of molecular weight polymer small, great mass loss;(2) to the degradation of polymer quality almost completely lost when the polymer relative molecular weight decreased dramatically.2. random chain scission reaction -- almost all polycondensate and add substantial degradation of polymersIrregular polymer chain scission reaction; the main product is low molecular weight polymer.Characteristic：(1) the initial molecular weight decreased rapidly and the quality of the polymer basically unchanged;(2) degradation to later stage, a large number of low molecular volatile polymer mass quickly disappeared.3. small molecular backbone fracture elimination reactionPolymer degradation caused by the elimination of side groups; and finally caused the main chain scission and comprehensive degradation.Features: from any part of the molecular chain of random elimination(two), the mechanism of degradationThe thermal oxidative degradation of the polymer at a certain temperature and oxygen in the air and the degradation reaction.Auto oxidation is the main feature of thermal oxidative degradation, but also the core of degradation.[heat: Auto oxidation reaction at room temperature to 150 DEG C, thermal oxidation is auto catalytic characteristics in the typical free radical chain mechanism, the. ]Schematic diagram of the polymer thermal oxygen cycleThe polymer thermal oxygen cycle, which represents the thermal oxidation process automatically. Seen from the figure, with each cycle, an initial alkyl radical R - at least 3 into a R, alkyl radical concentration is more and more high, the reaction speed is more and more fast, the formation of auto oxidation reaction.The rate of oxidation1. when the concentration of oxygen concentration in the air reaches or higher, with the rate of R and oxygen is very fast, [R -] < [ROO.Therefore, ROO double dominant coupling termination. The initiation rate is equal to the suspension rate (to reach steady state), available at steady state concentration of ROO.The oxygen concentration is greater than or equal to the oxygen concentration in the air, the oxidation reaction rate and the concentration of oxygen;2. oxygen concentration is very low, [R]>>[ROO, the reaction rate of the oxidation reaction rate depends on R and oxygen.In R, the termination reaction coupling termination dominant base,The oxygen concentration is very low, the oxidation rate of oxygen concentration.(three) the classification and method of adding antioxidant.Two kinds of antioxidants:The main antioxidant (radical scavenger): free radical reaction and auto oxidation process, interrupt the chain reaction.Features: automatic change of oxidation process.The auxiliary antioxidant (preventive antioxidant): can produce automatic decomposition of the oxidation process of ROOH without generating free radicals.Features: only reduce the oxidation rate, does not change the auto oxidation process.Principle: the sooner the better polymer added antioxidants.The type and mechanism of A. primary antioxidantThe main antioxidant can be divided into: hydrogen donor; electron donor; free radical trapping; benzofuran ketones.Hydrogen donor: is the most common secondary aromatic amines and hindered phenolic antioxidant.2,6-di-tert-butyl-4-methylphenolThe electron donor of tertiary amine containing reactive functional group of N-HGenerally, they can be given, generating onium cation.Radical trapping body can capture free radicals, and the product will no longer trigger free radical chain reaction.Benzofuran ketone - dilute oxygen conditions, alkyl radical captureWith B. antioxidantUse a variety of antioxidants, there will be synergistic effect, additive effect and antagonistic effect.Synergy: 1+1>2Two (or more) with antioxidant effect, the sum of more than separately use effect. Can be divided into both synergistic effect and hybrid Association effect.[cases] are synergistic effects of two kinds of hindered phenol.Antagonistic effect: 1+1<2Two (or more) with antioxidant effect, to separately use effect.Additive effect: 1+1 = 2Antioxidants used alone or in conjunction with other antioxidant,The effect of the same.(four) initiation of carbonylThe Norrish type I reaction between carbonyl and alpha carbon atoms bond cleavage.The Norrish type II reaction: only occurred in the gamma ketocarbonyl carbon atoms, at least one hydrogen atom under the condition can occur at room temperature.The Norrish type III reaction: through transfer of beta hydrogen atoms and C - C bond cleavage near the carbonyl side, the formation of aldehydes and alkenes.(five) stabilized light degradation and light degradation of oxygenA commonly used type of light stabilizer: light shielding agent; UV absorber; quenching agent; hindered amine light stabilizerThe 1. light shielding agentThe reflection or absorption of light at the polymer surface, or reduce the amount of transmission to the polymer, the main physical stabilization method.(1) surface protection agent: on the surface of polymer materials for coating or plating metal film protection.(2): carbon black pigment is the most effective light shielding agent.2. UV absorbersA kind of light stabilizer and most strongly and selectively absorb ultraviolet light, with low-energy radiation heat or harmless way to release energy.(1) two o-hydroxyl benzophenone UV absorber is the most importantCarbonyl ortho must contain a hydroxyl group to form hydrogen bonds through the chelate ring, keto enol tautomerism and to absorb and release energy. The intramolecular hydrogen bond strength is greater, more conducive to the process of tautomerism.No ortho hydroxy carbonyl when the compounds become photosensitizer.Six. The reaction of ozone with rubber- double bond addition reactionOzone cracking: the destruction of the ozone stress on the rubber, causing cracking in the direction perpendicular to the stress direction.Crack: rubber cracking caused by oxidative degradation.Seven. Biodegradable polymersNatural polymers are biodegradable, relatively natural polymer, synthetic polymer is difficult to be biodegraded.The third chapterA polyolefin.The structure of the polyolefin and polymer degradation and stability.The thermal stability of various key and group respectively:The thermal stability of order polyolefin as follows: polyethylene polypropylene polyisobutylene > >Main order: Polyolefin oxidation stability of high density polyethylene and low density polyethylene polypropylene > >Two PVC.The thermal stability of PVC is poor, without the stabilizer, cannot be processed into products by melting method.The thermal degradation of PVC 1.(1) the characteristics of degradation of PVC: the release of HCl -- the typical features; the presence of oxygen, accelerated degradation.The mechanism of HCl decomposition 2.PVC:(I) free radical mechanism: (II) ion molecule mechanism: (III) molecular mechanism:The photodegradation of PVC 3.PVC degradation and crosslinking during UV irradiation, the production of conjugated polyene and hydrogen chloride.The fourth chapterThe factors that cause a degradation in the processing andMechanical force, temperature, oxygen, water and other medium, such as trace metal impuritiesThe evaluation method of degradation and stabilization of polymer processing, twoAccording to the processing before and after processing (after different time or several times after processing) a performance test of polymer compared to make a judgment on the polymer degradation degree or stability.OneThe melt flow rate method. 2. the determination of relative molecular mass and its distribution. 3. rheological method. 4. yellow indexTwo. The degradation of PVC in the machining process1. the characteristics of degradation of PVCViscous flow temperature (160 to 212 DEG C) > the decomposition temperature (170 C)De HClThe dark - conjugated polymerThe molecular structure of polyene and intramolecular cyclization - polymer crosslinking and viscosity increase and the decrease of fluidityThe role of oxygen leads to removal of HCl increased;With polyene structure reaction, delay PVC color.Three. The influencing factors of the stability of PVC processingThe performance of the 1. polymer itself: molecular weight; particle morphology of resinInfluence of 2. factors on the degradation of PVC formula in the process ofCan reduce the viscosity of polymer melt.To improve the liquidity, reducing agent -- polymer degradation of PVC in the process of riskTo improve the processing of - PVCThe fifth chapterA polymer stabilizer.1. kinds of polymer stabilizersHeat stabilizer; light stabilizer; antioxidant capacity; chemical stabilizer; fungicideTwo. The mechanism of heat stabilizer1. preventive effect: to prevent the dehydrochlorination reaction, or at least can postpone the reaction.(1) the absorption of HCl, inhibit the auto catalytic role: metal carboxylate, organic tin mercaptide, epoxidized fatty acid esters(2) the replacement of labile chlorine atoms in the molecule of PVC, such as allylic chlorine or a chlorine atom of tertiary carbon, eliminate the trigger: metal soap, organic tin(3) to capture free radicals, prevent the auto oxidation of phenolic antioxidants:2. passivation effect: heat stabilizer can shorten the polyene sequence structure, and can form the PVC damage in the process of heating the carbon onium salt.Only organic tin stabilizer with thiol passivation and prevention functionThree types of heat stabilizers.1. lead heat stabilizer stabilizer2. organic tin stabilizer3. metal carboxylate stabilizer4. other metal stabilizer5.metal free 6. auxiliary stabilizerThe sixth chapterProcessing technology of waste plasticsThe establishment of waste plastics recycling system is feasible to eliminate environmental pollution and ensure waste plastic recycling.The main way of waste plastics recycling1. mechanical regenerationSimple regenerationAdvantages: economical and feasibleDisadvantages: requires relatively clean waste; high separation technology; end use markets products co.;Belongs to labor-intensive processing2. modified regenerationAdvantages: the mechanical property of the product is improved, can be recycled products of high gradeDisadvantages: process is complicated and some specific equipment3.: depolymerization is an advanced technology with the rapid development of recycling4. pyrolysis and gasificationAdvantages: pyrolysis can handle all can not be treated by other ways of waste plastics,Liquefaction condition can be selectedWithout the prior separation of plastic, also do not need to remove the impuritiesDisadvantages: gasification process General requirements for harsh conditionsThe pyrolysis liquid products need to be purified to more hydrocarbon components5. burningAdvantages: energy, fuelDisadvantages: exhaust pollution6. landfillAdvantages: simpleDisadvantages: loss of all available energy; space; exudate pollution; waste plastic refractory; huge investmentThe seventh chapterThe combustion characteristics of polymer materials.1. heat temperature of2.3. high flame burning speed of4. burning poisons released5. in the combustion will produce deformation, softening, melting and dropping phenomenon, which has a great influence on the combustion state, often cause the spread of fire, which makes it difficult to fire.Two. The combustion process of polymer materials3. fire by properties of materials are as follows 1. decomposition of the heating and melting heat: 2. flash temperature, autoignition temperature, limit oxygen index4. burningNet heat of combustion to combustion >0Net heat of combustion <0 stop burning5. flame propagationThree. Combustion process of polymers1. in the combustion of organic matter, the first thermal oxidation degradation reaction of polymer chain, long chain rapid collapse, liquid or solid organic materials into combustible gas (hydrocarbon),Combustion is a free radical chain reaction of 2. small molecule hydrocarbon, eventually forming carbon dioxide and water.3. polymer combustion, the main fuel is hydrogen, instead of carbon; in the polymer structure as the hydrogen molecule from substitutionThe key is to capture the 4. flame retardant free radical and free radical resistance and low energy. The combustion of PVC leaving the fire extinguish, because it generates hydrogen chloride can capture free radicals in the cleavage process.Four. Flame retardant agent and flame retardant mechanism1. basic options: (1) the polymer itself has a certain flame retardance (2) combustion velocity is relatively small(3) (4) good heat resistance and flame retardant filler, good compatibility2. flame retardant flame retardantThe endothermic effect covering effect of dilution effectThe inhibitory effect of enhancement effect3. as a flame retardant with four service conditions:(1) flame retardant is not flammable or low flammable material.(2) have good dispersion in polymer materials.(3) cannot be destroyed by the physical properties of flame retardant material. (4) flame retardant itself or under combustion conditions do not release toxic gases4. kinds of flame retardantsAdd type* easy to use, wide application range,* but there is a certain impact on the performance of polymer,* mainly used in polyethylene, polypropylene, polyvinyl chloride and polystyrene resin.* such as chlorinated paraffin, four Bromethyl, aluminium hydroxide and magnesium hydroxide etc..Reaction type* as a monomer in polymerization, the polymer with flame retardant properties.* operation and processing complex* four phthalic anhydride and two bromine chloride four bisphenol A is a reactive flame retardant.* for the polycondensation reaction, such as polyurethane, unsaturated polyester, epoxy resin, polycarbonate, etc..5. flame retardant mechanism of flame retardantDifferent flame retardant, the flame retardant mechanism is different, but the overall physical effect and chemical effect of.- physical effects of dilution of combustible materials, heat effect and air isolation effect;Chemical interaction in carbonation, eliminate free radicals and phosphorus acylation.The stability and degradation of the eighth chapter of medical polymer materialsOneBiomedical materials can be divided into three categories: medical metal materials, medical ceramic materials and medical polymer materials2.. Various factors in vivo degradation:* after a large number of studies show that the release of inflammatory cells (enzymes and enzyme hydrolase) and oxidant (O2 *, H2O2, OH), acidic substances (such as fatty acids) and substances in body fluids (Ca2+, phospholipid, cholesterol) constitute environmental degradation.* all non endothelialization surfaces of synthetic materialsstimulate certain levels of immune response in vivo, such as inflammatory reactions, and therefore all materials in the body are degraded.* the inflammatory response of the material depends on the interaction of the material surface with the protein in the body fluid. The adsorption and denaturation of the protein is the cause of the biological response to the cell and material interface.3. natural materials: gelatin, chitosan, cellulose, protein, natural coralDegradation of 4.PCL5. polylactic acid (PLA)direct methodThe relative molecular weight of polylactic acid produced by the method is less than 4000, and the strength is low, so the practicability is not strong.indirect method* first, DL- lactic acid was prepared by condensation polymerization with ZnO powder as catalyst* polylactic acid was synthesized by vacuum polymerization under the high temperature with ZnO as catalyst. The synthesized PLA has a molecular weight of 7.3 * 1046. tissue engineeringThe relationship between structure of mammalian tissues using the principle and method of engineering and life sciences to understand the normal and pathological features, biological tissue substitutes and development of live, used to repair, maintain and improve the function of human body.Three major elements of tissue engineering (1)Cell carrier materialThe separation of the cells themselves may not form the organization, they need temporary support material growth, the three-dimensional simulation of the natural counterpart, often in the extracellular matrix, which plays a physical support role, and adhesive substance cell loading in vitro and late implantationThree major elements of tissue engineering (two)Isolation and culture of cellsIndividual cells were collected from healthy parts of the donor tissue and isolated and then transplanted to the site needed by the patient.Three major elements of tissue engineering (three)Cell growth factorIn tissue and organ regeneration, various tissue inducing factors, growth factors and angiogenesis stimulating factors are beneficial to the formation of tissue, but it can not be implanted directly into the body.。

聚合物溶液稳定性在聚合物驱机理中，聚合物通过增加水相黏度，同时降低水相渗透率，改善流度比，提高波及系数。

聚合物分子的任何降解都会导致流度控制的失败。

因此，保持聚合物溶液在地下的强度至关重要，这也是聚合物驱成功的最重要的条件。

保证聚合物溶液的稳定性，也就是要防止聚合物降解。

聚合物降解是指聚合物主链断裂，或主链保持不变而改变了取代基的过程。

聚合物降解主要取决于聚合物本身的化学结构(尤其是化学键键能。

外界因素如应力、温度、含氧量、残余杂质都对聚合物降解有很大影响。

在聚合物驱油中，通常将聚合物的降解分为机械降解、化学降解和微生物降解三个大类。

下面将分别介绍三种降解的原因，影响因素以及保持聚合物溶液黏度所采取的措施。

1．机械稳定性在聚合物驱过程中，聚合物溶液经地面注入(搅拌罐、静混器、闸门和射孔眼进入地层后，其黏度损失主要是由聚合物的机械降解作用引起的。

机械降解是指聚合物分子受到的拉伸应力超过了聚合物分子内化学键所承受的能力时，聚合物分子链断裂的现象。

在常用的聚合物中，部分水解的聚丙烯酰胺(HPAM的机械稳定性较差，而黄胞胶却具有较好的抗剪切性，因此，下面将主要对HPAM机械稳定性进行讨论。

1聚合物驱中的机械降解过程在所有聚合物驱应用中，聚合物都会存在机械降解的可能性。

(1地面设备中流速变化处如闸门、喷嘴、静混器、泵、管线等部位中都有可能降解。

(2在搅拌中，聚合物的降解不仅与转速有关，而且还与搅拌器形状及叶片分布有关。

(3聚合物溶液在地层中尤其是在井筒附近区域的机械降解最为严重。

由于岩石孔隙很小，流速很高，拉伸应力很大，因此降解非常严重。

如果射孔密度不大，射孔炮眼中机械降解也比较严重。

2影响剪切降解因素影响剪切降解的因素有流速、流场应力分布、聚合物相对分子质量、水解度以及地层水矿化度。

流速越高，拉伸应力和拉伸速率越大，分子越容易断链。

拉伸速率为：式中 Q——流速；A——截面积；φ——孔隙度；——岩石颗粒平均半径。

聚合物稳定与降解第一章、绪论1.老化（降解）的概念高分子材料在加工、贮存、使用过程中，物理化学性质和力学性质会逐渐变差，称为老化，或降解。

p1特点：不可避免，不可逆的过程。

时间尺度上相对较短。

2.导致聚合物降解的因素（一）内因A．聚合物的组成及其链结构。

（1）组成不同、降解情况不同（2）活性基体可能是降解的主要内因（3）活泼氢更容易被夺取（4）头－头（尾－尾）结构的聚烯烃更易成为活性点。

（5）分子量变化的影响：分子量的变化使其内部不规则的结构增加，造成稳定性下降。

反之，若不规则结构减少，则稳定性增加。

（6）分子量分布的影响：分子量分布宽、则稳定性下降。

（7）支化度的影响：支化度增加，分子链中的薄弱环节也增加，越容易发生降解。

B. 聚合物的聚集状态非晶聚合物材料稳定性小于结晶聚合物材料原因：非晶材料密度小(高分子链排列不规则），易被氧、水、化学物质渗透、降解。

3. 聚合物中的杂质聚合物中的杂质分两类：（1）加工过程中必然混入的少量杂质；（2）添加剂等物质。

多数杂质会加快聚合物的降解。

（二）外因：A．热、温度和热氧的影响：热使聚合物断链，形成自由基（可逆、双向）热氧作用使聚合物交联或降解，最终使材料性能下降。

B.光的影响C.氧和臭氧的影响：氧易在热、光作用下使聚合物降解。

臭氧对不饱和键（如橡胶）的破坏极为严重。

D. 水和潮湿的影响：对水溶性成分的溶解、抽提；水解、断链。

E.其它因素的影响：微生物的影响；其它生物的影响；加工过程中各种因素的影响。

各种外因往往协同作用。

第二章、聚合物降解与稳定化的基本原理（一）热降解的类型解聚反应；无规断链反应；主链不断裂的小分子消除反应；特点：单纯由热引起，没有氧参与。

1. 解聚反应（拉链降解）解聚始于分子链端部或薄弱点。

惟一产物：单体。

特点：（1）初期相对分子质量变化小，聚合物质量损失较大；（2）降解至聚合物质量几乎完全损失时，聚合物相对分子量急剧降低。

2. 无规断链反应——几乎所有缩聚物和大量加聚物的降解方式聚合物无规则断链；反应主要产物为低相对分子量聚合物。

聚合物降解与稳定化
聚合物降解是指聚合物在所受外界条件的作用下，发生化学结构的变化，导致聚合物分子链的破坏和物理性能的下降。

聚合物降解的原因主要有热氧化降解、光辐射降解、机械应力引起的降解等。

降解会导致聚合物材料的拉伸强度、弹性模量等物理性能下降，甚至使其完全失去使用价值。

而聚合物稳定化是为了延缓聚合物降解的过程，提高聚合物材料的耐久性和使用寿命。

常见的聚合物稳定化方法有添加抗氧化剂、紫外吸收剂等。

抗氧化剂可以防止聚合物在高温、氧气和紫外光等环境下发生自由基氧化反应，从而延缓聚合物的降解速度；紫外吸收剂则可以吸收紫外光，减少紫外光对聚合物材料的照射和损伤。

聚合物降解与稳定化是聚合物材料研发和应用中需要重点考虑的问题。

降解会限制聚合物材料的使用寿命和应用范围，稳定化则可以提高聚合物材料的耐久性和可靠性。

因此，在聚合物材料的设计和生产过程中，需要选择合适的降解机理和稳定化方法，以满足不同应用环境和需求。