Air release in PVC plastisols

The ability of a PVC plastisol to liberate entrapped air during mixing and processing is an important factor to the processors. This property, known as air release, is affected by several variables such as resin, plastisol viscosity, surface tension, surfactant system and plasticizer type. A study was conducted to obtain a more fundamental understanding of the effects of these variables on air release. Complicating the accurate study of a plastisol's air release properties is the fact that current test procedures such as the vacuum rise, syringe test and Huff or ring test each have limitations imposed by either plastisol properties or by testing technique. Any one of these procedures alone may not adequately measure air release. This paper, in addition to studying the factors affecting air release, discusses these testing limitations and makes recommendations as to the best methods for evaluating air release properties in the laboratory.     

Testing variability in viscosity measurements of PVC plastisols

An experiment was conducted to compare the variability of the Brookfield Viscometer, the Severs Extrusion Rheometer, and the Haake Rotational Viscometer in measuring flow characteristics of PVC plastisol. The author discusses variability of the different test methods involved with the Severs and the Haake viscometers. Also discussed are operator, environmental, and day-to-day variation.     

Processing and properties of high-temperature creep-resistant PVC plastisols

The effect of the use of an unsaturated reactive plasticizer trimethylopropane trimethacrylate, TMPTMA, on the structure and the creep behavior of poly(vinyl chloride), PVC, plastisols has been investigated as part of a program to develop a high-temperature creep-resistant liner material. The crosslinking reaction was initiated with a peroxide. The effect on the network structure of using a free radical scavenger in the formulation has also been studied. Gel yield and grafted PVC content in the gel increase with increased TMPTMA content in the plastisol. However, the residual unsaturation of TMPTMA decreases with increase of TMPTMA content. Introduction of TMPTMA into the plastisol promotes the creep resistance at high temperatures, and the effectiveness increases when there are PVC molecules grafted onto TMPTMA networks.     

Viscoelasticity and mechanical properties of reactive PVC plastisols

Reactive poly(vinyl chloride) (PVC) plastisols have been developed to substitute the hydrocarbon diluents generally used in low viscosity PVC plastisols. For this purpose, methacrylate monomers (5–15%) were added in the PVC suspension (based on diisononyl phtalate plasticizer) to reduce the viscosity at room temperature and to polymerize (by radical polymerization initiated by an organic peroxide) during the gelation process. Both the reactive processing and the gelation process were carried out between the plates of a rheometer cell in the linear viscoelasticity domain (small deformation) and under increasing temperature from room temperature up to 160°C (ω = 6.283 rad s^?1, = 5°C min^?1). A temperature criterion was proposed to define the right balance between the polymerization and the gelation to get the best mechanical properties (i.e., elongation and stress at break). The polymerization process must be slower than the gelation process as the polymerization must take place when PVC grains have fused together to form a homogeneous medium at least at the microscale. Actually, the polymerization kinetics can be controlled by the decomposition kinetics of the organic peroxide. Finally, triethylene glycol dimethacrylate and lauryl methacrylate monomers and dicumyl peroxide as initiator turned out to be the best reactive system for some potential industrial applications. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers     

Dynamic TG studies on the thermal decomposition of PVC plastisols

The kinetics involved in the thermal decomposition of PVC plastisols and unmixed PVC-plasticizer systems were compared using dynamic thermogravimetric (TG) analysis. Three kinetic models were tested. In all cases thermograms obtained at different heating rates were simultaneously correlated with the same constants. Significant differences indicative of PVC-plasticizer (DOP) interactions were found between the plastisol systems and the unmixed PVC-plasticizer systems. When the plasticizer is in the paste, its evolution suffers a delay with respect to the case when PVC and plasticizer were separated. The activation energy for DOP evolution takes the value 109.2 in the first case and 81.6 KJ/mol in the second case. PVC decomposition takes place at lower temperatures when it is in the paste, and its activation energy is 177.4 and 206.7 KJ/mol for PVC in plastisol and unmixed PVC, respectively.     

Kinetic analysis of the thermal degradation of PVC plastisols

The thermal degradation of plasticized polyvinyl chloride (plastisol) is reported here. Plastisols used in the present work were prepared with the plasticizer diethylhexyl phthalate in different proportions. Thermogravimetric analysis has been applied to study the behavior of plastisols at high temperatures and to evaluate their degradation kinetics. Several tests were carried out at different heating rates and the variation of the degree of reaction with time and temperature was calculated. The influence of the heating rate in dynamic measurements (5–40°C/min) on kinetic parameters, such as activation energies and reaction orders, has also been studied. These parameters were calculated from dynamic thermogravimetric analysis tests using Friedman analysis and a kinetic model for the degradation of poly(vinyl chloride) and plastisols has been then developed. The obtained model was able to simulate the thermal degradation process of plastisols in dynamic conditions and was used to evaluate the effects of additives in the degradation. The results of this study can be used to optimize the concentration of plasticizers and stabilizers in poly(vinyl chloride) formulations. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 1069–1079, 1999     

PVC plastisols: Preparation,properties, and application

The engineering issues of plastisol preparation, composition, properties, and application are considered. Special attention has been paid to the adhesion characteristics of plastisol coatings.     

Effects of paste resins on the foaming properties of PVC plastisols

This article studies the foaming properties of PVC plastisols prepared from six different types of PVC paste resins with different degrees of polymerization that were produced through two methods, a seed emulsion method and a micro-suspension method. The underlying mechanisms that result in differences in the foaming properties are discussed as well. The results indicate that formulation S5 has the best foaming quality using past resins produced with the seed emulsion method, and formulation S6 made the best plastisol samples from paste resins produced through the micro-suspension method. Seed emulsion-produced paste resins with low degrees of polymerization are more suitable for preparing high-quality foam materials. The parameters used to judge the foam quality are the initial decomposition temperature T_f (5%), T_f − Tη_max and T_f (5%) − Tη_max. The greater the value of these three parameters, the better the foaming effect. The degree of polymerization of the paste resin and the particle morphology directly affect the rheological parameters, namely Tη_max, of PVC plastisol, and subsequently affect the magnitude of T_f − Tη_max and T_f (5%) − Tη_max, which in turn affect the quality of the foam.     

Fusion behavior of plastisols of PVC studied by ATR-FTIR

The behavior of PVC plastisols during gelation and fusion was studied by the ATR-FTIR technique (Attenuated Total Reflectance-Fourier Transform Infrared Spectroscopy). DBP, DOP, and DIDP, three common phthalate plasticizers for PVC, were used in plastisols formulations. Three heating rates—5, 10 and 15°C/min—and formulations with different plasticizer concentrations were studied. The IR spectra of a plastisol coincides with the IR spectra of the plasticizer except for the bands at 1435 and 613 cm^?1 from the PVC (CH₂ wagging and C—Cl stretching, respectively). When the plastisol is heated, a progressive decrease of the plasticizer bands areas can be observed, while bands from PVC increase their intensity, probably because of the adsorption of the plasticizer by the resin. On cooling, the area of all bands follows the same path as when heating, but the paths separate at a certain temperature, showing the irreversible nature of this process. The analysis of the band at 1280 cm^?1 (C(O)—O from plasticizer) during heating and cooling, shows that the temperature of separation areas (T_s) takes place at temperatures coherent with plasticizer compatibility. Studies at different heating rates and different plasticizer content are in good agreement with results using other techniques, available in the literature.     

Gelation and fusion profiles of PVC dispersion resins in plastisols

Poly(vinyl chloride) (PVC) plastisols are used for coatings, films, sheets, foams, and rotational castings. In order to satisfy the requirements for the different applications, a variety of PVC dispersion resins are manufactured. The requirements for the plastisols are many: for example, good air release, viscosity stability, fine particle size, foamability, and good heat stability. Processability is another important requirement, which emphasizes the rheological behavior at room temperature and the gelation—fusion behavior. This paper documents research to fingerprint the gelation and fusion profiles of various PVC dispersion resins. The viscoelastic measurements were used to continuously monitor the changes of moduli during gelation and fusion under a heating rate which simulates the temperature profile of the processes. The effects of molecular weight, resin type, and copolymer on the gelation–fusion behavior are discussed.     

Study of the processability of commercial PVC plastisols by rheology

A qualitative model that satisfactorily explains the rheological behavior of PVC plastisols during gelation and fusion is shown. Several industrial production cases have been analyzed, and the rheological characterization of the corresponding plastisols during gelation and fusion processes has proved to be a valuable technique to improve the knowledge and understanding of the industrial rotomolding process.     

Influence of crystallinity in the curing mechanism of PVC plastisols

The influence of the crystalline areas observed in poly(vinyl chloride) (PVC) the mechanical and thermal properties of PVC plastisols was studied. Several industrial‐degree PVC resins were used to obtain a broad range of molecular weights and processing conditions for PVC plastisols. The gelation process was fully studied at different temperatures and was related to the existence of crystalline areas at high temperatures, even near the glass transition. A simple explanation of the phenomena observed during the gelation of plasticized PVC is proposed, according to the variation in the mechanical and thermal properties at different temperatures. The final gelation was obtained at 140–150°C, which was a lower temperature than those at the beginning of the thermal degradation process. The thermodynamic aspects of the gelation of plasticized PVC were mainly controlled by the PVC resin properties, whereas the plasticizer only influenced the diffusion and stability of the material. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 538–544, 2004     

Modification of epoxy resins by the addition of PVC plastisols

An epoxy resin based on bisphenol A has been modified by the addition of different amounts of a plastisol, based on poly(vinyl chloride) (PVC) and diethylhexyl phthalate (DOP). The fluid state of those materials makes their blending easier. After a curing process, some different materials, with properties ranging from the rigidity of a thermosetting resin to the flexibility of a plastisol, can be obtained. The variation of different parameters, such as tensile strength, Young's modulus, dielectric constant, and others, with the concentration of plastisol, has been studied. Some materials with properties similar to common thermoplastics (PP, ABS, or SB) can be processed, depending on the epoxy-to-plastisol ratio. The obtained results enable us the use of those materials in prototyping and other industrial processes. The obtained prototypes should have a similar mechanical behavior to thermoplastics. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 67:1769–1777, 1998     

Processability of PVC plastisols containing a polyhydroxybutyrate‐polyhydroxyvalerate copolymer

Plastisols based on polyvinyl chloride (PVC) can be processed by different techniques; their processability markedly depends on their flow properties and gelation/fusion processes. Classically, PVC has been the only polymer present in plastisol formulations. The present work explored the possibility of adding polyhydroxyalkanoates (PHAs), a type of biopolymer that, according to previous work, exhibits a good miscibility with PVC processed by other techniques (internal mixer and compression molding). The influence of PHA particles on flow properties, gelation‐fusion processes, tensile strength, hardness, and processability by rotomolding was evaluated. Although the biopolymer markedly increased the viscosity of PVC plastisols and caused a decrease in tensile strength in processed specimens, formulations including 20% by weight of biopolymer presented a good thickness distribution in rotomolded items, an elongation at break of around 300%, and an ultimate tensile strength of around 6–7 MPa. J. VINYL ADDIT. TECHNOL.,, 2012. © 2012 Society of Plastics Engineers     

Characterization of resol resins modified by the addition of PVC plastisols

Plastisols, which are a blend of poly(vinyl chloride) resin and a plasticizer (DEHP), were used as a toughening agent of a resol resin in order to improve the mechanical properties. It was not possible to formulate resol blends by adding more than 10 % of plastisol owing to a lack of apparent homogeneity in the systems, which also showed many air bubbles. The relationship between dynamic mechanical, mechanical and thermal properties and the amount of plastisol added was studied. It was determined from the infrared spectroscopy and dynamic mechanical results that the resol–plastisol blends seem to be formed by a reaction between the phenol and PVC giving a higher crosslinked structure. An improvement in the thermal resistance of the blends at lower temperatures was observed with an increase in the percentage of plastisol. Flexural analysis showed the elastic behaviour of the systems. However, it was not possible to observe the effect of the plasticizer (DEHP) owing to the low quantity of plastisol that was added to the resol. Copyright © 2004 Society of Chemical Industry     

A rheological study of the ageing of emulsion and microsuspension-based PVC plastisols

A PVC plastisol is a homogeneous dispersion of PVC resin in a liquid continuous phase consisting basically of a plasticizer and a thermal stabilizer; the PVC resin being usually a fine powder is polymerized by emulsion or microsuspension processes. Plastisol rheology is affected by many aspects of the plastisol formulations, such as type and amount of each ingredient, the mixing procedure, temperature, and the effect of PVC resin properties. In this work, the ageing behavior of PVC plastisols with different resin types was studied, with the results showing an unexpected behavior in the elastic modulus, probably originating from plasticizer adsorption at the surface of the PVC particles. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Formulation and mechanical characterization of PVC plastisols based on low‐toxicity additives

New formulations of plastisols based on low‐toxicity plasticizers were proposed and characterized. Traditional phthalate plasticizers were replaced in the plastisols studied in this research by polymeric plasticizers (i.e., saturated polyesters), produced by the reaction of a diol and a carboxylic acid. The main drawback for the use of these plasticizers in formulations of PVC plastisols is a significant increase of the paste viscosity, which decreases their processability; thus, the use of additional additives to reduce viscosity is recommended. This study also includes the optimization of the processing conditions (cure temperature and time) of the proposed plastisols: complete cure was obtained at 140°C and 10 min. It is reported that the final properties of plastisols are very sensitive with respect to the processing conditions; in fact, insufficient plasticization or degradation can affect the material when processed out of the optimum conditions. The influence of the plasticizer concentration on mechanical and optical properties, such as tensile strength, hardness, brightness, and the like, is also reported. In summary, the proposed plastisols, with low‐toxicity plasticizers, offer a valid alternative to traditional PVC plastisols based on phthalate plasticizers. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 1881–1890, 2001     

硅油和白炭黑比表面积对硅橡胶性能的影响

气相法白炭黑是硅橡胶补强的最佳填料,羟基硅油是硅橡胶补强中常用的1种结构控制剂。本文研究了羟基硅油的用量以及气相法白炭黑比表面积对硅橡胶力学性能的影响。结果表明:随着羟基硅油用量的增加,硅橡胶的硬度、拉伸强度均逐渐降低,而断裂伸长率却随羟基硅油用量的增加而逐渐增大;随着气相法白炭黑比表面积的增大,硅橡胶的硬度、拉伸强度逐渐增大,而断裂伸长率逐渐减小。     

The effect of melt-flow properties of PVC plastisols during fusion cycle on flooring wear layer surface quality

A rheological test to characterize the melt in various vinyl coating resins in a flooring wear layer formulation shows that the surface quality (absence of orange-peel) of the resilient foamed flooring is associated with the viscoelastic nature of the wear layer resin during the cure cycle: Resins with high molecular weight of a sufficiently high melt viscosity showed no entrapment of air bubbles or tendency to orange-peel, while resins with low melt viscosity produced very severe orange-peel. Orange-peel is independent of the type of foam resin used. For a given formulation, the proper selection of wear layer resin or resin mixtures that will develop the desired hot melt strength to contain the gases given off by the decomposition of the blowing agent, will help to alleviate or minimize orange-peel.