Suspension Resin Research Articles

Processing of precipitated nongranular PVC in the brabender measuring mixer

AbstractThe structure and properties of processed poly(vinyl chloride) (PVC) depend on temperature, shear rate, operations time, and morphology of the PVC grains. The aim of our research was the preparation of a nongranular PVC and the examination of its processing during kneading in a Brabender plastographometer in comparison with the processing of commercial PVC. It was stated that grains of virgin PVC‐S61, a commercial suspension resin, cause a self‐heating of the compound during kneading in such a way that point X of the plastograms occurs at a temperature 15°C lower than that of precipitated PVC (i.e., PVC without grains). As a result of self‐heating, time of compound processing needed to reach point depends largely on the grain morphology of the PVC. The less compact structure, the smaller bulk density, and the greater absorption of plasticizer, result in a longer processing time. Homogeneous, loosely packed particles of powder and the crystalline structure of precipitated PVC are different from PVC‐S61 morphology and cause a high degree of gelation and low melt flow rate values for compounds processed at 175°C and higher. J. VINYL ADDIT. TECHNOL., 18:147–152, 2012. © 2012 Society of Plastics Engineers

Dynamic mechanical, rheological, and morphological studies of polyacrylate‐graft‐poly (vinyl chloride) suspension resin

AbstractA series of polyacrylate‐graft‐poly (vinyl chloride) (ACR‐g‐PVC) resins were prepared through suspension graft copolymerization. Three kinds of polyacrylate latices were grafted by vinyl chloride using suspension polymerization method at 57 ± 0.1°C, respectively. The dynamic mechanical and rheological properties and the morphology of the resulting ACR‐g‐PVC resins were investigated. Poly (butyl acrylate)‐graft‐poly (vinyl chloride) (PBA‐g‐PVC) resin exhibited better toughness, and the optimized content of PBA in ACR‐g‐PVC resin was 6–8 wt%. The melt viscosity of ACR‐g‐PVC resin was much lower than that of pure PVC. The nature of the fracture surfaces of ACR‐g‐PVC material indicated that it has good toughness. The impact strength of the PBA‐g‐PVC material was greatly improved compared with that of pure PVC. The Young's modulus of the ACR‐g‐PVC material containing less than 15 wt% of PBA was comparable to that of pure PVC according to their dynamic mechanical analysis curves. For all of the ACR‐g‐PVC resins, there were two individual relaxations in the low‐temperature range. One was β transition of PVC, and the other was α transition of ACR. The glass transition temperature of PVC in the ACR‐g‐PVC resin shifted to lower temperature when the content of the PBA was above 50 wt%. POLYM. ENG. SCI., 47:996–1003, 2007. © 2007 Society of Plastics Engineers

Relationship between the isotopically exchangeable and resin‐extractable phosphate of deficient to heavily fertilized soil

SummaryThe rate and extent of soil–solution transfer of orthophosphate ions (Pi) depend both on soil solution Pi concentration and on time. This is so both in experiments on sorption–desorption and in those on isotopic exchange. Because the two methods are based on different principles, it is questionable whether they give a similar quantification of Pi transfer.The amount of isotopically exchangeable Pi, E, was determined over periods of 100 minutes and described as a function of both time and Pi concentration in solution for three soil samples taken from field plots having different P fertilizer histories over 26 years of annual application. In separate experiments, amounts of Pi, Qd, were extracted from soil suspensions using three levels of anion exchange resin strips for periods ranging from 10 minutes to 7 days. Both initial and final solution Pi concentrations were measured. These concentrations and periods of resin‐contact were used to predict the difference in E, ΔE, between the initial and final states of the suspension–resin system using extrapolations of the equations fitted to the exchange data. Under conditions in which the solution concentration of Pi decreased during extraction the ΔE values and the resin‐extracted Pi values, Qd, were equal. It is thus possible, using the description of E, to predict the amount of Pi released from soil suspension knowing the initial and final solution Pi concentrations and the time it took for the system to pass from the initial to the final state. For the soil studied, identical amounts of mobile Pi, i.e. the Pi which participates in the soil–solution dynamics, may therefore be assessed by either isotopic exchange or desorption.

Extrusion‐rotomolding of plasticized PVC formulations

AbstractIn this work, we present a novel process to produce plasticized PVC articles. Plasticized PVC dispersion resin (dry blend) was extruded and poured into a hot mold. The mold was transferred to a rotomolding machine, where the final geometry was obtained. Formulations using commercial PVC suspension resin and three different types of plasticizers were prepared under different processing conditions. The physical appearance of the articles and the tensile properties of the materials were evaluated.

The nonyl phthalate ester and its use in flexible PVC

AbstractSix di‐nonyl phthalates varying in degree of branching are evaluated in both suspension and low soap plastisol resin formulations. Comparative plasticizer performance properties of these systems are studied in terms of plasticizer structural differences and their affects on processing parameters and physical properties of suspension resin and low soap dispersion resin formulations.

The influence of poly(vinyl alcohol) suspending agents on suspension poly(vinyl chloride) morphology

AbstractThe requirements for PVC suspension resin have changed considerably in the last few years, so much so that few companies have products on their ranges that are more than 4 or 5 years old. The suspending agent has a crucial influence on the morphology of the resin, so the changes in resin characteristics have largely been achieved by changes in the suspending agent systems.After a brief review of the mechanism of PVC suspension polymerisation, the properties of polymers made using PVOH suspending agents are related to changes in the latter. The effect of variations in PVAc degree of hydrolysis and viscosity are related to changes in surface tension. Methods of achieving higher porosity by using low hydrolysis co‐suspending agents are described. It is shown that higher bulk densities can be achieved by delayed addition of the PVOH. Levels of conjugated unsaturation and copolymer distributions are also shown to have important influences.

The effect of the interior particle structure of PVC suspension resin on the behavior of plasticizer absorption

Abstract In the suspension polymerization of vinyl chloride, halting at low conversions and polymerizing with certain organic chemical additives in the reactor recipe result in resins that exhibit somewhat faster plasticizer absorption behavior. By fitting vinyl chloride monomer sorption rate data for some specially prepared suspension resins to a Fickean diffusion model, the effective diameters of sorbing sphere structures in resin grain interiors were measured and were identified as groups of primary particles knitted together into compact 3-μm agglomerates. Good correlation between these measured agglomerate diameters and the reduction in plasticizer dry times, which were induced either by lowered conversion or increased use of an organic chemical additive during polymerization, led to the conclusion that these polymerization variables achieve their effects primarily by reducing the size of the agglomerates.

The morphology, rheology and processing properties of polyvinyl chloride

The critical observations of Berens and Folt (1) and Collins and Krfer (2) have focused research on the particulate nature of PVC. It has been shown by many working in the field that this particulate nature is the controlling feature in both the fusion and flow behavior of PVC compounds. The morphological nature of the suspension resin can be related to the ease of processing of PVC compounds. Resin particles with interior particulate material loosely packed break apart easily and are more readily processed than tightly packed systems. Resin particle uniformity is also important in the fusion process. A model for the fusion process of PVC is proposed based upon these findings. The effects of additives used in compounds is discussed. The factors the author views as being important for the future development of PVC processing is presented. Polyvinyl chloride is the world's second largest commercial polymer and one of the oldest. Surprisingly, the work that has been done characterizing its rheological, morphological and physical properties has only taken place in the last two decades. The other major polymers such as polystyrenes and polyolef ins, technical history goes back at least three or four decades. The reasons for this delay in the technical investigations of PVC was most likely due to the unique and complex properties of this polymer. In addition to the complex properties of PVC, a second major drawback to its study is its thermal degradation

Behavior of plasticizers in poly (vinyl chloride) resins. I. A method for measuring dynamic plasticizer absorption in suspension resin grains

AbstractAn instrument which measures the absorption of plasticizer in resin grains as a function of time is described. From a single experiment, one is able to determine directly the capacity of the resin for a desired plasticizer and the time and temperature required for complete absorption or “drying‐up” of the plasticizer by the resin. Based on data for a series of resins with different polymerization histories, observations regarding the effects of grain morphology on plasticizer absorption are discussed.

A method for the determination of the internal particle structure of poly(vinyl chloride) suspension resins by analyses of vinyl chloride desorption rate data

AbstractA method has been developed for analyzing the vinyl chloride desorption rate data from poly(vinyl chloride) resins. This technique, based on Fickean diffusion kinetics already demonstrated for this system, yields fundamental internal particle morphology information, which is in agreement with that determined by other methods. The approach detailed in this manuscript can be applied to other particle‐penetrant systems for which the nature of the diffusion kinetics is known.

Polyvinylchloride melt rheology II—the influence of molecular weight on flow activation energy

AbstractThe flow behaviors of a series of polyvinylchloride (PVC) resins covering a broad range of molecular weight have been examined at several temperatures. It has been shown that the influence of temperature on viscosity depends on the temperature range. That is, the flow activation energy is not constant but can be approximated by two values, one applicable to low temperatures, the other to high temperatures.The flow activation energy based on viscosities at constant shear rate decreases as the molecular weight increases. In contrast, the flow activation energy from viscosities at constant shear stress increases with molecular weight.The fact that the activation energy is dual valued does not seem to be associated with the polymer type. Both emulsion and suspension resins exhibit this behavior. Addition of certain modifiers appears to alter the activation energy at lower temperatures. These observations indicate that the shift in the activation energy in the low temperature range is due to a change in the flow mechanism.