PVC stabilizers detection

1 hydrotalcite, organic auxiliary classes of organic compounds such as single-use type, the thermal stability is not good, often with a metal-containing heat stabilizer compound used. Currently used thermal stabilizers are organic polyols, phosphite, epoxidized soybean oil, 1,3 - dione. Polyhydric alcohol is the mechanism: generating a complex catalytic effect of chloride, thereby enhancing the effect of the thermal stability of metal. The most commonly used polyols are pentaerythritol, dipentaerythritol sorbic alcohol. WangMing other studies of pentaerythritol heat stabilizer for calcium zinc thermal stabilization, S.van E.Daan polyols and other studies on PVC processing performance. Organic phosphite heat stabilizer is the most important and the calcium stearate largest use one, when compounded with the metal soap is used, the effect is obvious. Commonly used are alkyl and aryl phosphites. Epoxy oils has attracted more and more people's attention, such compounds are characterized by a molecule containing one or more epoxy groups, PVC heat generated when hydrogen chloride, an epoxy group to quickly react with , blocking the hydrogen chloride from the catalyst for PVC, thereby improving the thermal stability of PVC. As the epoxy oils of PVC has a strong plasticizing action and non-toxic, in recent years, many such as food packaging for soft cork bottle plasticizers and heat stabilizers. Wu Maoying other studies β-diketone compound and zinc heat stabilizing effect, that the β-diketone complexes of zinc with excellent thermal stability performance. PVC heat stabilizers organic research is entering the 21st century one of the hotspots. As the representative of Egypt Sabaa researchers studied a variety of organic compounds and their derivatives stabilizing effect on PVC, typical substances vanillin - Schiff base, barbituric acid, etc. These organic compounds have excellent thermal stability. In addition to the calcium zinc stabilizer organic auxiliary heat stabilizers, thermal stability of the PVC industry, hydrotalcite, synthetic zeolites, and other inorganic perchlorate also used in supplemental heat stabilizers. Hydrotalcite layered inorganic metal material, its molecular formula is: Mg6Al2 (OH) 16CO3, while water of crystallization with a conventional synthesized by coprecipitation method. When a hydrotalcite is used as heat stabilizers for PVC, and PVC processing can be released during the degradation reaction of hydrogen chloride, when the hydrotalcite is used alone as heat stabilizers for PVC, the effect is not ideal, and a metal soap compound generally used. Hydrotalcite obvious disadvantage is poor compatibility with PVC, in recent years, different researchers by reducing the size of the hydrotalcite to improve their dispersion in PVC or molecular modification hydrotalcite enhance compatibility. Synthetic zeolite molecular sieves or more types of structure of the compound, usually containing oxides of silicon and aluminum composite, also contain water of crystallization, the molecule containing regular pore structure. In recent years, zeolite PVC industry as a heat stabilizer also been studied and used. Using an oil bath pot, built glycerin, will be tested PVC heat stabilizers mixed with the material after being loaded into a small test tube, so that the material becomes a slight concussion and firm, and then placed in an oil bath pot among glycerol oil bath pot set in advance a temperature of approximately 170 ℃, PVC material within the small tube and the upper surface of the upper surface level of glycerin, small tube top, with a thin tube inserted into the plug, the upper and lower transparent glass, the glass tube Congo red paper hit the bottom of the roll inserted so Congo red paper with the lower edge of the upper edge of the PVC material is located about 2 cm. After the start of the experiment, record the test tube to the test tube from Congo red paper turns blue start time is the thermal stabilization time. The basic theory of this experiment is that when the PVC at a temperature of about 170 ℃ when rapid decomposition, but with the addition of a heat stabilizer, suppresses the decomposition, with time, the heat stabilizer consumption occurs when the antimony oxide consumption is completed , PVC dramatically HCl gas decomposition in this case, the test tube as Congo Red reagent reacts easily with HCl and discoloration, will be immediately apparent, a note of the time determined by the length of time to heat stabilizer the effect of pros and cons. 2.2 Preparation of the static oven test in addition to thermal stability of PVC powder and other agents other processing aids (such as lubricants, impact modifiers, fillers, etc.) of the high-speed mixed sample. The sample must be taken, according to certain proportion of different thermal stabilizers, after mixing, add to the double-stick kneading machine for preparation of test pieces, generally without the addition of a plasticizer in the case, two roll temperature is set at 160 ~ 180 ℃, adding a plasticizer, the roller temperature is generally about 140 ℃. Tabletting using two stick repeatedly to obtain a uniform film after the backsheet, and clip, a certain size with different samples PVC heat stabilizer. Different PVC sheet placed in a test fixture, and then placed at constant temperature (180 ℃) of the oven at regular intervals (eg 10 min or 15 min), to record the color change of the test piece until the black so far. An oven aging test, can determine the thermal stability of PVC heat stabilizer effect to the merits, particularly ability to inhibit the color change is generally believed that, PVC heat, the color will occur white - yellow - brown - brown - black range from shallow deep changes, through a certain period of time to determine the color of PVC degradation. Torque rheometer torque rheometer is an imitation of the actual PVC processing of a typical small pilot-type apparatus. Outside of the instrument a closed processing tank, connected to the instrument by the computer can control the machining tank temperature, and within two roll speed, torque rheometer added quality of materials is generally 60 ~ 80 g, depending on the apparatus and different models. Experimental procedure is: be prepared in advance with different thermal stabilizer masterbatch, masterbatch formulations, in addition to base other than PVC general there ACR, CPE, 64 engineering applications 2011, Volume 39, No. 8 CaCO3, TiO2, lubrication agent. Torque Rheometer advance the set temperature, when the temperature rose to specify and steady speed, will be weighed mixture added processing chamber, quickly closed records on a computer connected to a variety of parameters, namely flow curve. After processing, you can also get different extrudate physical characteristics, such as whiteness, whether shaping, smoothness and so on. These parameters can determine the corresponding potential industrial heat stabilizers, heat stabilizers suitable shall have suitable torque and plasticizing time of the extrudate should be preferably molded and whiteness, surface smoothing. Torque rheometer in laboratory studies and between industrialized mass production to build a convenient bridge [24]. 2.5 blackened roll as a dynamic measurement test the effect of a thermal stabilizer class helper methods, dynamic rheometer double roll is used in the absence of experimental double-rolled sheet, select the instrument, which will be combined with high-speed mixed powder, pressed sheet forming, the resulting samples were subjected to repeated extrusion until the black test piece until completely black record time, the time is called blackening. Blackening by comparing the length of time to determine the type of thermal stabilizer effect of the thermal stability of PVC. 4 LDHs as PVC heat stabilizers research LDHs are a class of special structure and properties of inorganic crystalline materials, the typical structural features: ordered nanoscale laminates; has exchangeable interlayer anions; Shelf element according to the design requirements can be adjusted within a certain range; isomorphous substitution can also be introduced by other metal atoms, such as the host layer alkaline. Synthetic hydrotalcite with other thermal stabilizer compound as PVC heat stabilizer, can significantly increase the thermal stability of PVC, PVC material may also be given a number of other excellent properties, which is due to the hydrotalcite has a unique structure and properties. Huayou Qing [4] studied the Mg-Al hydrotalcite layered double hydroxides right through the base of PVC rigid and lightweight thermal stability, introduced the stabilizer coprecipitation synthesis method, and its X- ray diffraction analysis and thermal gravimetric analysis; results show that this kind of novel thermal stabilizer has important environmental value and economic benefits. Zhang Li [5] by colorimetry, pyrolysis studies hydrotalcite, lead salts, organic tin, as well as hydrotalcite and lead salts, organic tin compound stabilizers for PVC composite stabilizing effect, study the lead salt stabilizer system and hydrotalcite and organic tin compound stabilizer systems for PVC mechanical and rheological properties. The results showed that: hydrotalcite can not be the primary stabilizer of PVC, it should only be a secondary PVC stabilizer or stabilizer compounded with other compound stabilizers for use ratio of Mg 2 DLHs effect on the thermal stability of PVC most Jia, respectively, and lead salts hydrotalcite, organotin compound were carried out with good synergies and the latter better stability of PVC. Which, PVC, hydrotalcite and organic tin compound to 100:1.5:1.5 mass ratio of thermal stability of the composite system is not only superior to the conventional lead salt system, with good mechanical and rheological properties. Liu Zhiyuan [6] in the appropriate conditions, by coprecipitation synthesis of a series Mg-Al hydrotalcite products. Mg-Al-based hydrotalcite adjustable main characteristics of the chemical composition of shelves, first explores the Mg-Al-based hydrotalcite-doped calcium possibilities. The flame retardant and smoke suppression function of calcium into the main body of Mg-Al hydrotalcite chemical composition of laminates, laminates replace some or all of the magnesium ion, achieved through the experimental study of calcium magnesium aluminum layered product type three metaclasses and calcium aluminum hydrotalcite Bivariate Hydrotalcite synthesis. Using XRD, FT-IR on their composition and structure were characterized. XRD results that the samples are synthesized hydrotalcite layer structure, good crystal, high purity. IR analysis of samples tested synthetic interlayer anions are good symmetry of CO32-, further confirmed the Ca / Mg / Al Hydrotalcite successful synthesis. First studied as a flame retardant, heat stabilizer in PVC applications. Experimental results show that the Ca / Mg / Al hydrotalcite can improve the thermal stability of PVC. Under comparable conditions, MgAl-CO3-LDHs flame retardant and smoke suppression performance than Al (OH) 3 and Mg (OH) 2. At the same dosage (20phr) case, calcium magnesium aluminum type ternary Mg-Al hydrotalcite exhibited than hydrotalcite and hydrotalcite-type calcium aluminum better flame retardant and smoke suppression performance, indicating Ca2 + has improved materials flame retardant and smoke suppression effect.