Juan Carlos García

Rheological study of the influence of the plasticizer concentration in the gelation and fusion processes of PVC plastisols

The influence of the type of plasticizer and its concentration on the rheological behaviour of plastisols made from several commercial resins during the gelation and fusion processes has been studied. The use of different concentrations of plasticizers as well as plasticizers with different compatibilities has allowed the observation of relevant differences in the behaviour of the elastic and viscous moduli in plastisols with low concentration of plasticizer as well as in plastisols prepared with plasticizers having higher compatibility with PVC. In addition, scanning electron microscopy has been used in order to obtain a better understanding of the gelation and fusion processes.

Infrared spectral changes in PVC and plasticized PVC during gelation and fusion

Abstract The behaviour of PVC and PVC plastisols has been studied during their thermal treatment using an in situ FTIR technique. The plasticizer introduces certain modifications in the spectrum of the resin which are more marked in the case of the more compatible plasticizers. The A 1427 A 1435 and A 637 A 616 ratios of the intensities of the crystalline and amorphous bands of the resins, decrease in the plastisols when increasing the compatibility of the plasticizer. On the other hand, when the plastisol undergoes the gelation process, a great decrease of these ratios is observed, showing that the increase in temperature produces a decrease in the amount of the crystalline phase in the resin with respect to the amorphous phase. This behaviour has also been observed when the resin is heated without plasticizer, and is a reversible process. The CO band corresponding to the plasticizer shows a different behaviour to the resin bands. When the temperature increases, a shift to lower wavenumbers is observed. This displacement is irreversible (the band does not recover its original location after cooling) and the process occurs in a relative narrow temperature interval. This temperature range, where the carbonyl band suffers these changes, is in good agreement with the gelation temperature as measured by other techniques.

RHEOLOGICAL STUDY OF PVC PLASTISOLS DURING GELATION AND FUSION

Abstract A rheological study of the behaviour of different plastisols during gelation and fusion processes has been carried out. For this purpose, ten different commercial PVC resins have been employed. The influence of the heating rate, oscillation frequency and type of resin and plasticizer has been analyzed.

Influence of the type of resin in the gelation and fusion processes of PVC plastisols

Abstract A rheological study of the influence of the type of resin in the gelation and fusion processes of PVC plastisols was carried out using several commercial PVC resins, with different particle size distribution and molecular weight. Results obtained prove that the gelation rate and the moduli developed increase with decreasing both the particle size and molecular weight.

Qualitative model for viscoelastic measurement during gelation and fusion of PVC plastisols

In previous studies [Marcilla, A. and Garcia, J. C., Eur. Polym. J., 1997, 33(3), 357; Garcia, J. C. and Marcilla, A., Polymer, 1998, 39(2), 431; Garcia, J. C. and Marcilla, A., Polymer, 1998, 39(15), 3507] the behaviour of PVC plastisols during gelation and fusion was monitored by analysing their viscoelastic properties obtained in oscillation tests. Results have shown that elastic and viscous modulus reflect gelation in a different way. On the one hand, the elastic modulus may undergo two processes (attributed to the solvation of different zones of the resin), whereas on the other hand, the viscous modulus may undergo up to three processes, two of them occurring simultaneously with those observed in the elastic modulus and a third step appearing between the others. A qualitative model has been suggested in order to explain these behaviours.

THEORETICAL MODEL FOR THE GELATION AND FUSION MECHANISMS OF PVC PLASTISOLS BASED ON RHEOLOGICAL MEASUREMENTS

Abstract The influence of plasticizer concentration in the processes of gelation and fusion of PVC plastisols has been studied by viscoelastic oscillatory tests. A theoretical model has been developed, based on our experiments and on microscopic observation, which is capable of accurately representing the behaviour of the viscoelastic properties of the pastes during the gelation and fusion dynamic experiments.

Thermal decomposition behaviour of crosslinked plasticized PVC

Abstract Thermal stability and thermal decomposition behaviour of plasticized PVC poly (vinyl chloride) and crosslinked plasticized PVC films has been studied. Two effective crosslinking agents have been used: the sodium salt of γ-mercaptopropyltrimethoxysilane (MSi) and γ-aminopropyltriethoxysilane (ASi). Clear differences have been observed in the thermogravimetric behaviour of the different samples. MSi crosslinked films show a certain delay in the decomposition process as compared to plasticized PVC as well as three clear decomposition processes, probably involving the plasticizer and different fractions produced in the crosslinking reactions. In the case of the films prepared with ASi a single decomposition stage is observed at temperatures much lower than those obtained in the other PVC films studied, showing the strong influence of this compound in the thermal behaviour of plasticized PVC. ©

Study of the flow properties and the ageing process in PVC plastisols from commercial PVC resins

The influence of the particle size distribution and the molecular weight distribution in the flow properties and ageing process of commercial PVC plastisols have been studied. An accelerated method to study the interactions between the resin and the plasticizer during the ageing process of the plastisols has been suggested.

Computing the Principal Local Binary Patterns for face recognition using data mining tools

Local Binary Patterns are considered as one of the texture descriptors with better results; they employ a statistical feature extraction by means of the binarization of the neighborhood of every image pixel with a local threshold determined by the central pixel. The idea of using Local Binary Patterns for face description is motivated by the fact that faces can be seen as a composition of micro-patterns which are properly described by this operator and, consequently, it has become a very popular technique in recent years. In this work, we show a method to calculate the most important or Principal Local Binary Patterns for recognizing faces. To do this, the attribute evaluator algorithm of the data mining tool Weka is used. Furthermore, since we assume that each face region has a different influence on the recognition process, we have designed a 9-region mask and obtained a set of optimized weights for this mask by means of the data mining tool RapidMiner. Our proposal was tested with the FERET database and obtained a recognition rate varying between 90% and 94% when using only 9 uniform Principal Local Binary Patterns, for a database of 843 individuals; thus, we have reduced both the dimension of the feature vectors needed for completing the recognition tasks and the processing time required to compare all the faces in the database.

The effect of adding processed PVC on the rheology of PVC plastisols

In this paper the possibility of recycling the PVC resulting from the rotational moulding of plastisols is studied. Parts of processed PVC were ground with liquid nitrogen into four fractions of different sizes which were added to a plastisol at different concentrations. A study of the influence of the amount and size of the recycled PVC in the viscosity of the plastisol and in the gelation and fusion processes was carried out. Furthermore, samples were taken at different temperatures and observed by SEM (scanning electron microscopy). Results obtained for plastisols with the recycled PVC show a marked increase in the viscosity and moduli reached during gelation with time, which are more marked as the amount of recycled PVC increase and the particle size decrease. However, plastisols including recycled PVC show and adequate processability if they are used immediately after their preparation.