Dependence of Gelation and Fusion Behavior of Poly(vinyl chloride) Plastisols upon Particle Size and Size Distribution

Abstract

ABSTRACT:Poly(vinyl chloride) (PVC) plastisol is a suspension of small particles of PVC resin in plasticizer. The processing of plastisol typically involves flow at room temperature during coating or mold filling, and gelation and fusion as the plastisol is heated to form the final product. This paper explores the effect of the particle size distribution on the gelation and fusion behavior. For this purpose a commercial PVC resin was air-classified into fractions of different particle size. Samples were then reconstituted to have known particle size distributions. Particular emphasis is placed on the effect of the fine particle fraction on the material behavior. The progress of gelation and fusion were followed by measurement of the viscoelastic properties as a function of treatment temperature using a mechanical spectrometer. Characteristic changes in the viscoelastic behavior were associated with changes in morphology, observed with a scanning electron microscope, enabling qualitative discrimination of the gelation and fusion processes. The larger fraction of fine particles gave higher values of G' and G". It seems that the fine particles promote the interparticulate bonding, when the particles start fusing together.KEY WORDS Poly(vinyl chloride) I Plastisol I Particle Size Distribution I Gelation-Fusion I Particulate Morphology I Viscoelastic Properties 1 Both the average particle size and the particle size distribution of poly(vinyl chloride) (PVC) dispersion resins have been recognized as important material variables pertinent to PVC plastisol behavior. The flow behavior at room temperature is profoundly influenced by these variables. Therefore, they are important in regard to processability. The types of flow behavior encountered in these systems, such as thixotropy, shear-thinning and dilatancy have been investigated previously. 1 The oscillatory measurements were also carried out to characterize the dynamic responses. 2 On the other hand, less attention was paid to the effect of particle size and size distribution on gelation and fusion. Since gelation and fusion are also important steps in plastisol processing, we have undertaken this study. gelation and fusion. 5 These observations elucidated the mechanism of the diffusion of plasticizer into resin particles, the presence and disappearance of particulate structure and the temperature range of the melting of the PVC crystallites. In addition, the progress of interparticle bonding was postulated to explain the accompanying development of mechanical strength.Our previous studies demonstrated the effectiveness of viscoelastic measurements for characterizing gelation and fusion behavior. 3 -5 Morphology was also examined of samples taken at different stages of When the plasticizer is taken up by the resin particles, a large amount of interparticle voids are present; these voids disappear, of course, when the particulate structure disappears. However, some defects are present up until the fusion is complete; the latter state is reached when the mechanical ...

Plastisol gelation and fusion rheological aspects

“…The importance of diffusion processes is clearly confirmed by the results of García and Marcilla10–13 showing the tremendous influence of particle size and polymer molar mass on modulus and viscosity changes on such systems. An increase of particle size has qualitatively the same effect as an increase of plasticizer molar mass.…”

“…“Gelation” could be first associated to the loss of tackiness,1 that is, presumably to the disappearance of the liquid phase constituted of almost pure plasticizer. It is also possible to associate “gelation” to the disappearance of the granular morphology 1, 11–13. However, rheological measurements of T min considered as the temperature of the onset of “gelation” and T max where “gelation” is generally considered complete, are the most common ways for characterizing this phenomenon 1–5, 14, 15…”

Investigation of PolyVinyl Chloride Plastisol Tissue-Mimicking Phantoms for MR- and Ultrasound-Elastography

“…PVCP is a combination of a PVC colloidal suspension in a liquid ester plasticizer, the role of which is to soften the final material. These gels are formed through the gelation-fusion process (Nakajima, Isner and Daniels, 1981). In the current study, after mixing the PVC resin suspension (40% to 80%) and the plasticizer (a Bis(2-ethylhexyl) adipate) (Plastileurre Soft and Softener, Bricoleurre, Mont-Saint-Aignan, France), the solution is heated.…”

The Effect of Curing Temperature and Time on the Acoustic and Optical Properties of PVCP

“…Preventing bubble formation or premature solidifying during pouring into the mould was also a significant challenge. These difficulties encountered while following the fabrication protocol S1 may be related to the composition of the PVCplasticizer suspension used, as the effect of the particle size and distribution on PVCP viscoelasticity is a well reported phenomenon [23]. The fabrication method suggested by the provider of the PVCP suspension utilizes a microwave oven.…”