PVC crisp reasons and solutions (-)

PVC brittle basically in products fully reflect the physical and mechanical properties of.Its main characteristic is: blanking collapse, cold rushed to rupture.Physical and mechanical properties of profile product there are many reasons for the poor, mainly for the following: A, formulation and mixing process is not reasonable:1, packing:Profile according to the present market price is low, and the pattern of rising prices of raw materials, material manufacturers are on the lower costs for the article.Normal profile manufacturers through the combination of the formula, is on the premise of not reduce the quality, reduces the cost;Some manufacturers are to reduce costs at the same time also reduces the quality of products.Because of formula components, is the most direct and effective way to increase the packing, in PVC -u plastic special-shaped material that is commonly used in packing for calcium carbonate.Formula system mostly before filling calcium compound, its purpose is to increase the rigidity and reduce the cost, but coarse whiting because itself is irregular shape and particle size is coarse particles and PVC resin intermiscibility of ontology is poor, so add attachments are low, and the number increases will affect profiles of colour and lustre and apparent.With the development of technology, now mostly using superfine light activated calcium carbonate, even the nano-sized calcium carbonate, its not only have the effect of increasing rigidity and filling, but also have the function of the modification, but the add quantity is not unlimited, the ratio should be controlled.Now some manufacturers in order to reduce the cost to add calcium carbonate to 20 to 50 quality, which greatly reduces the profile of the physical and mechanical performance, this chapter said profile brittle phenomenon.2, impact resistant modifier add type and quantity:Impact modifier is under stress, the total energy can improve PVC burst of a polymer.The rigid PVC impact modifier main varieties of CPE, ACR, MBS, ABS, EVA, etc., including CPE, EVA, does not contain a double bond in the molecular structure of the ACR modifier, good weather resistance, suitable for outdoor building materials, they and PVC blend, can effectively improve the impact resistance of rigid polyvinyl chloride, processability and weatherability, and within a certain range increased the strength of welding Angle.In PVC/CPE blend system, its impact strength increased with the increase of the dosage of the CPE, s-shaped curve.Adding amount in 8 quality, system impact strength growth is very small;Adding amount in 8-15 biggest increase when the quality of;After growth and flatten out.When the dosage of CPE 8 quality copies of the following is not enough to form a mesh structure;When the dosage of CPE in 8-15 quality, its continuous evenly dispersed in the blending system, the formation of split phase separation of mesh structure, to maximize the impact strength of blending system growth.When the dosage of CPE than 15 quality, will not be able to form a continuous uniform dispersion, but a part of CPE gel formation, so that on the two phase interface won't have suitable CPE particles dispersed to absorb the impact energy, thus the impact strength growth tends to slow.But in PVC/ACR blending system, ACR can significantly improve the shock resistance of the blend system.At the same time, "a nuclear shell" particles can be evenly dispersed in PVC matrix, PVC is the continuous phase, ACR is dispersed phase, dispersed in PVC continuous phase, and the interaction with the PVC have the effect of processing AIDS, promote the plasticization of PVC and gelation, plasticizing time is short, has a good processing performance.Forming temperature and plasticizing time less impact on the notched impact strength and bending elastic modulus decline is also small.General dosage in 5-7 quality, the ACR modified hard PVC products have excellent impact strength at room temperature or low temperature impact strength.And the experimental demonstration, ACR and CPE impact strength is higher than 30%.So as far as possible in the formula using PVC/ACR blending system, and modified by CPE and dosage less than 8 often caused when the quality of material brittle. 3, stabilizers, too little or too much:The function of stabilizer is inhibiting degradation, or with the release of hydrogen chloride reaction and prevent discoloration of PVC processing.Stabilizer according to the different dosage is different, but the general point, use too much could delay the material plasticizing time making material still owe plasticizing export mode, the formula between system is not fully amalgamation, insecure between the molecular structure.And will cause the amount is too small relative low molecular formula system degradation or decomposition (or into a plasticizing), the stability of between different components of molecular structure.So how much dosage of stabilizer is also will affect the impact strength of profiles, too much or too little can brittle phenomenon caused by the decrease of strength of profiles profiles.4, external lubricant consumption too much:Lubricant and resin intermiscibility is low, can promote the sliding between the resin particles, thereby reducing the friction heat and delay the melting process, the role of lubricant early in the process (that is, in the external heating function and internal friction heat lose resin complete melting and melt in the resin identification features before) is the biggest of all.Lubricants and lubrication points in the early and late outside lubrication, the lubrication excessive material in various conditions are characterized by poor appearance, it is no good if the dosage of lubricant, may cause the flow mark, low yield, turbidity, impact, rough surface, adhesion, plasticizing etc.Especially when dosage too much, can cause profiles, poor compactness of plasticizing, poor, and lead to impact performance is poor, cause material brittle.5, hot charging order, temperature set value and curing time on the performance of the material also has a decisive factor:PVC -u formula of many components, the selected sequence should be conducive to play the role of each of these additives, and is helpful to improve the dispersion speed, and avoid its negative synergies, additives of sequence should help to improve the effect of fertilizer supplement each other, overcome phase grams of destructive effects, should be dispersed in PVC resin additives, fully into the inside of PVC resin.A typical system of lead salt stability formula feeding sequence is as follows: