PVC formulation quality stand or fall, the lubrication

A lot of research and practice show that the degree of plasticizing PVC -u at around 65%, its the best mechanical properties, so when you in the processing of PVC - U must have appropriate knowledge of the plasticizing degree, the lubricant in reducing plasticizing torque at the same time can promote the plasticizing (shorter plasticizing time), extra lubricant in improving the liquidity of PVC -u and also can delay the plasticizing.In formula design of PVC - U, adjusting the ratio of internal and external lubricants and adding amount, can regulate plasticizing rate of PVC -u (plasticizing time), and regulating the plasticizing rate is an important content of internal and external balance of lubrication.However, due to the variability of plastic lubrication and balance the diversity of lubrication in domestic haven't seen a monograph about lubrication balance article, the author is plastic lubrication balance (hereinafter referred to as the lubrication balance) puts forward some ideas and reference for the readers.The design of the lubrication balanceLubrication balance PVC -u formula design is the design of the most key link.1.1 lubricants and lubrication is not the real meaning of theory and lawFor general PVC -u formula design, the author thinks that the difficulty of formula design and the main content is the selection of internal and external lubricants and their ratio and adding amount of design.Total lubricants to join should be appropriate, and the proportion of the internal and external lubricant is more important, although total enough, but if the ratio, also be continuously produce qualified products.However is vital for PVC -u processing lubrication system, theory, the not yet may be called theory even formula can effectively guide the experiment rule.The only discipline is reference to the similar miscibility regularity in general chemistry, which is the more similar the polarity of the lubricant and the polarity of the PVC resin, its compatibility is rape, and thus its lubrication effect is better;Outside of the lubrication effect is stronger, but the rules for judging formula design guidance is also limited because the polarity of the lubricant is according to the chemical structure of lubricants, lubricant molecules containing hydroxyl, ester base, carboxyl, amide group and ether base, ketone group type and quantity of polar functional groups and the proportion of long chain alkyl.Because of the lubricantComplex chemical structure, diversity, as well as the adjacent functional groups influence each other, makes the size of the polarity judgment of lubricant is more difficult, it is caused by the polarity of the lubricant to infer lubricant lubrication and lubricants lubrication role actually between difference than people think.1.2 lubrication of the complexity of the problem of variability is not only that, the more important is the lubricant and the compatibility of resin (i.e., lubrication) also influenced by other conditions, especially the influence of other lubricants with additives such as plasticizers, this change can make the lubricant into the lubricant inside even, that is to say, the same kind of lubricant lubrication with the adding amount of different, along with other additives in the formulation of different, and subject to change with different processing conditions.1.3 the diversity of internal and external lubrication balance as a matter of fact, different types of processing equipment such as twin screw and single screw extrusion, injection molding, calendering and other equipment, all require different lubrication balance.Strictly speaking, the same kind equipment, products of different manufacturers, and even the same equipment, old and new equipment, the lubrication balance all have different requirements.Different types of products, such as pipes, sheet, film, and profiles, should have their own different lubrication balance.Such as section complex profiles, sheet extrusion, injection molding products, hollow products, blown film and high transparent products requirements have higher plasticizing degree, better melt fluidity and thus require internal and external lubricants, especially want to some more, for the amount of lubricant inside the pipe to the melt viscosity and liquidity requirements is relatively high, plasticizing degree with 60% ~ 70% advisable, therefore external lubricant can be relatively than the lubricant with a bit more.But plastic injection products require as little as possible with nonpolar lubricant, in order to minimize the external lubricant's influence on the strength of weld mark.The diversity of the content above all illustrates the lubrication balance.This makes lubrication theory research is relatively difficult, in the actual formula design, also greatly increase the difficulty of lubricant formulation.The author thinks that, in the case of general PVC -u, formula design is the key internal and external lubricant type, proportion and adding amount of design, it is the design of the lubrication balance. B lubricating balance research methodsFor the design of the lubrication balance, neither jing chu internal and external lubricants lubrication of actual strength in the formula, and I don't know other lubricant and other additives on the lubricating effect of the specific situation.The simplest method, is to use only for the final results, regardless of its effect mechanism of macroscopic research method, which only considers factors (internal and external lubricant additives and other) contribution to the final results (lubrication balance) method, which is no matter how between internal and external lubricant additives and other the size of the interaction and influence degree, only to see them for lubrication balance the end result of comprehensive effect. The definition of C lubrication balance and their quantitative expressionInternal and external lubricants varieties, appropriate proportion of internal and external lubricants and adding appropriate amount, to reach the appropriate plasticizing rate and melt viscosity (torque rheological curve on appropriate plasticizing time and plasticizing torque).Which can guarantee the specific processing equipment and process economically, continuously produce qualified plastic products of lubrication system, is the internal and external balance lubrication system.Plasticizing time 3.1 appropriate lubrication balance is not a fixed value, and because of the lack of lubrication of basic data, so the quantitative expression of lubrication balance is very difficult.So, can only use contrast analogy for lubrication balance were studied.Is the first research has identified is lubrication balance system, put it in the plastic processing equipment on the plasticizing and its in torque rheological curve of plasticizing condition were compared.It is found that the lubrication balance system on torque rheological curve of plasticizing time corresponding to the extruder about two-thirds position, namely corresponding extruder plasticizing period will end, homogenization section will start position.If not lubrication balance system, the plasticizing time corresponding to the location of the extruder will change.Plasticizing time corresponding to the location of the extruder is less than two-thirds of the period, the excessive plasticizing, for PVC -u possible thermal decomposition, material yellow;Plasticizing time corresponding to the location of the extruder is more than 2/3, the plasticizing degree is insufficient, products is relatively rough and brittle.From the above analysis can be concluded that can use the torque rheological curve of plasticizing time as the quantitative standard to determine whether a lubrication system in balance.3.2 appropriate plasticizing torque for PVC -u, plasticizing torque balance than the size of the torque is closer to the end of the plastic processing the actual resin melt torque, that is to say, the material viscosity in plasticizing torque place close to the actual plastic processing at the end of the melt viscosity.So-called internal and external lubricants and appropriate amount refers to the use can meet the technical requirements, the resin has a suitable plasticizing rate, melt viscosity and appropriate adhesive, thus ensuring processing equipment can be economical, continuous production of qualified or high quality products.Extruder while also gives the torque value or host current value, but said they are solid resin by glass state gradually transformed into high elastic state, the whole process flow of the average torque values or average consumption of energy, can not correctly reflect the resin viscosity on plasticizing or torque value. D in the production and laboratory and how to determine the lubrication balanceLow dosage of lubricant is have adhesion phenomenon, plasticizing time short, the sample surface is not smooth;Excessive is plasticizing time significantly prolong lubricant, mechanical performance degradation, crisp, there may be precipitation phenomenon, serious when hand feel sample.In the low dosage of lubricant is plasticizing larger torque and plasticizing time longer;Excess lubricant inside the plasticizing time is shorter, plasticizing torque is small, but the thermal stability of time also shorter, thermal decomposition, there were sample the lining is not smooth E inside and outside the proportion of lubricant and the determination of total lubrication balance designNumber of internal and external lubricants varieties or determined, want to make sure that the use of internal and external lubricants proportion and amount of joining in the formulation.Only determine a suitable proportion of internal and external lubricants and the addition of the total, to reasonably PVC resin of melt flow rate, and viscous, and give attention to two or morethings plasticizing rate, to meet specific processing equipment, the special requirements of technology and products, and only in this way can the lubrication system of guarantee economically, or continuous production high quality products, which meet the lubrication balance.Due to many factors, which affect the lubrication, and because of the diversity of the lubrication balance, so the formula workers according to the specific processing equipment and product features to design a lubrication balance system is relatively difficult.Unable to accurately determine the plasticizing time, plasticizing torque and other important values, and lack of control the plasticizing rate, melt liquidity (that is, the melt viscosity).If you have a reference, the standard sample or similar standard sample, the problem solution of the struggle.So, first determine the lubrication balance experimental program is a test of standard sample.Standard sample had better choose machining performance is good, good quality, the same kind equipment in the production of high speed stirring the mixture of the same kind of product(1) of the standard sample test: add a certain quality of sample to the torque rheometer, at a certain speed and temperature measuring small its plasticizing time, plasticizing torque and time parameters such as thermal decomposition.(2) the change in the variety and quantity of lubricant, such as plasticizing torque values to make it close to the value of standard sample.Also is the change of PVC melt fluidity, namely the melt viscosity.(3) in the basic adjust resin melt viscosity or under the premise of plasticizing torque, outside by changing the type and quantity of lubricant, adjust the plasticizing time, than standard sample slightly extended, extend probably around 3%.Lubricant in a certain range can also affect plasticizing torque, with an increase in the amount of lubricant, plasticizing torque is also reduced.Pay special attention to the plasticizing torque value must not be higher than the value of standard sample, must be plasticizing torque value is slightly lower than the standard sample, it is advisable to reduce about 1% ~ 2%.If plasticizing time has been extended by about 3% than the standard samples, the plasticizing torque when still can not meet the requirements, may be increased in proportion to the amount of internal and external lubricants, until the plasticizing time and plasticizing torque are up to par.Because minor differences from the torque rheometer experimental data can cause huge impact to the actual industrial production.(4) the adhesion: if the torque of the plasticizing and plasticizing time after basic satisfaction, prevent adhesion insufficient, can be appropriate in proportion to increase the amount of internal and external lubricants, if feel material has not stuck rheometer mixing head rotor, is likely total lubricants, reached a high level of lubrication balance.May be appropriate in proportion to reduce the amount of internal and external lubricants, until when some slightly sticky.Based on the way to fine tune appropriately adding internal and external lubricants, until not tacky, again a bit more, this is a lower level of lubrication balance, is more close to the practical level of lubrication balance.A high level of lubrication balance while you can slightly improve the thermal stability of resin mixture, extend the time of thermal decomposition, slightly reducing the amount of heat stabilizer, reduce the cost formula, but external lubricant precipitation phenomenon may be more serious, adverse to the continuous production, stop times is likely to increase, productivity is likely to decline, and bring inconvenience, also may affect the product quality and secondary processing performance.Because of internal and external lubricant is, after all, small molecules, processing AIDS, can satisfy the requirement of processing and product quality, the quantity is too much is bound to affect the mechanical properties of products.(5) amplification experiment: the experiment (4) the primary formula in the production of amplification experiment, examine and discover the existing problems and serious or excessive torque such as adhesion to host current is too large, or the plasticizing rate is too big, too small, and so on.Can adjust the lubrication system of a targeted.So repeated several times to design a satisfactory, and can satisfy the requirement of specific equipment and process of lubrication balance system.(6) if there is no standard formula, to have the power of technology foreign manufacturers of large-scale heat stabilizer and lubricant for reference formula, according to the reference formulation trial production time, find out the problems existing in the process and product quality.Workability problems include the melt viscosity is too high, the host torque value or host current is too large, the operation is smooth and continuous driving time is too short, such as adhesive is a serious problem.Products quality problem including inner quality is in line with the standard and secondary machining are satisfied.Appearance quality problems include: the color is yellow, or black, dark gray or yellow stripes, whether the surface is shining, the lining of concave and convex inequality.At the same time with the same formula on the torque change flow meter to experiment, the rheological experimental results and the problems in the mass production against each other, find out the insufficient lubrication or outside lubrication, or internal and external lubrication are deficient.Then according to the experiment procedure, to improve the experiment or use the low price products to replace the original reference formula of imported lubricant experiment F increase the lubrication system of the elasticity of operationGood lubrication system not only has strong lubrication, lubricants consumption and some excellent properties of the foregoing, should also has a wide operation flexibility, such as, subtle differences in the proportioning process condition fluctuations (such as temperature, the change of the main engine rate of revolution, etc.), plastic processing practitioners hope lubrication system is still in a state of equilibrium.This requires the internal and external lubricant is tie-in, not only to advance in the should also have a large elasticity of operation.This can be solved in two ways:Without or with less volatile lubricant (such as paraffin, Hst and butyl stearate more volatile), in the whole process, the middle and late due to fluctuations in temperature and other process parameters influence the degree to which they are volatile, resulting in the equilibrium system imbalance.With some there are both polar groups and super long alkyl compounds, such as brown refined acid derivatives, fatty acids, fatty alcohols low molecular OPE so on polyester class, outside of lubricant, internal and external lubricant can automatically adjust the lubrication balance in different extent.If for some reason shows insufficient lubrication, the lubrication excess;Or contrary phenomenon, if there is a certain number of formulas of the internal and external lubricants, can automatically adjust to a certain extent, the glut of lubrication into lubrication, or internal lubrication into external lubrication.The generation of this kind of phenomenon is because the change of process condition change the resin melt caused by the apparent solubility with lubricant.