How the morphology of poly (vinyl chloride) compounds affects toughness and weatherability (original) (raw)

Processing-morphology-property studies of poly(vinyl chloride)

Polymer Engineering and Science, 1974

Recent morphological studies of plasticized and unplasticified poly (vinyl chloride) (PVC) are reviewed. Suspension polymerized PVC contains particles in a number of different size ranges 100-200A, 1000-5000A, 1~ and larger. The larger size particles are broken down during plasticization but both the 1OOA and the lOOOA suspension articles retain their idenparticles is a function of the processing conditions. In particular, the size of the lOOA particle increases with plasticizer content and is most distinct as characterized both by small angle x-ray scattering and electron microscopy for milling temperatures in the 160-170°C. range. Consideration is given to the effect of these particles, their structure, and interrelationship on the rheological properties of the resins. tity. The visibility, and presumaby, Y coalescence of these

Structural aspects of suspension poly(vinyl chloride): The thermal aspects of rigid suspension PVC

Journal of Polymer Science Part B: Polymer Physics, 1994

The structural aspects of rigid suspension poly (vinyl chloride), PVC, have been investigated on the basis of two independent series of suspension PVC samples, polymerized at temperatures between 26 and 84°C. The reproducibility of the suspension polymerization process and the importance of the polymerization temperature with respect to the macro-and microstructure is demonstrated. Quantitative examination of the grain structure by small angle neutron scattering, Brunauer-Emmett-Teller absorption technique, and mercury porosimetry clarifies the gradual increase of the specific surface on lowering the polymerization temperature. A detailed WAXS study shows an increasing degree of crystallinity on lowering the polymerization temperature, which can be associated with the corresponding increase of the syndiotacticity. Furthermore, the presence of a polymerization history in the PVC powders with respect to the crystallinity is evidenced. This effect seems to be related to chain mobility restrictions during the polymerization process and is determined by the difference between the polymerization temperature and the glass-transition temperature ( T,) of rigid PVC. This so-called Tg effect is indicative of the fact that no appreciable swelling of PVC by its monomer occurs. 0 1994 John Wiley & Sons, Inc. Keywords: poly(viny1 chloride) polymerisation conversion tacticity molar mass polymerization temperature microstructure macrostructure wide angle x-ray scattering small-angle neutron scattering Brunauer-Emmett-Teller absorption technique

Improving the Long-Term Performance of Poly(Vinyl Chloride)

Chemistry and Chemical Technology, 2022

1 Since neat PVC is rigid, in all applications a plasticizer is added. Migration of the plasticizer results in brittleness of flexible PVC and environmental pollution. We have used three types of cross-linking agent blended with commercial PVC, plasticizer and thermal stabilizer. Heat treatments at 100 С, 121 С and 136 C were performed. We made tensile tests, dynamic friction tests, wear rate determination, scratch resistance determination, water absorption tests and SEM analysisto make selection of compositions suitable for sufficient crosslinking for long term applications.

Structure and degradation of commercial poly(vinyl chloride) obtained at different temperatures

Macromolecules, 1993

The influence of microstructure on thermal degradation behavior was studied for four commercial poly(viny1 chloride) (PVC) resins with different polymerization temperatures and for two low molecular weight fractions. The samples were characterized by determining tacticity and the content of labile chlorine, i.e., internal allylic and tertiary chlorine. The degradation rates were measured both in nitrogen and in an atmosphere containing HCl, and the polyene sequence distributions were monitored by W-visible spectroscopy. It was found that there is a strong relation between the content of labile chlorine and the dehydrochlorination rate in nitrogen. For tacticity, on the other hand, the relation is much weaker. When degradation was performed in an atmosphere containing HC1, the dehydrochlorination rate was increased and the polyene sequence distribution was shifted toward longer polyenes. It is concluded that labile chlorine contributes most to the initial degradation rate and that tacticity is of minor importance. Furthermore, the presence of HCl in the sample, which depends on the dehydrochlorination rate, is an important factor determining the degradation behavior.

Viscoelastic properties of polyvinylchloride: influence of crystallinity

Viscoelastic behavior of PVC gels/sols in a wide range of PVC concentration c was examined in various plasticizers having different solubility toward PVC. The gel point c g decreased with decreasing solubility, possibly due to enhanced formation of PVC crystallites (crosslinking points in the gels) in poorer plasticizers. The exponent characterizing the power-law behavior of the critical gel (G'~G''~ω n), n = 0.75, was insensitive to the plasticizer solubility. The exponent z (= 2.52 ± 0.14), characterizing the equilibrium modulus G e of the well developed gels (G e~ε z with ε =c-c g /c g) was also insensitive to the plasticizer solubility. However, the magnitude of the normalized modulus c-1 G e was smaller in poor plasticizers, suggesting some heterogeneity in the gel network structure therein. The other exponent γ characterizing the viscosity η of the sols (η~ε γ) moderately increases from 1.2 to 1.9 with increasing solubility. Comparison of the normalized viscosity and compliance in different plasticizers suggested that the sol structure was heterogeneous and this heterogeneity sensitively increased with decreasing solubility.

An unusual crystallization peak of poly (vinyl chloride

Journal of Applied Polymer Science, 1997

Owing to an efficient quenching process that ensure r-poly(vinyl chloride) to be amorphous enough, crystallization of rPVC at lower temperatures has been found in samples with various processing histories. Through a modified Avrami analysis, kinetics of the isothermal crystallization at these low temperatures was studied, proving that the crystal growth in the studied temperature range was controlled by segment mobility, which should follow a WLF-type relationship. Such a mechanism is unusual compared to ordinary growth controlled by chain reptation. Also discussed were implications of the results to further crystallization study of PVC and to that of polymers in general. The treatment distinguished itself in that it can give out both spacial growth exponent and dependency of the dimension on time.

A rheological and morphological study of treated PVC

Journal of Applied Polymer Science, 2003

This article reports a rheological and morphological study of poly(vinyl chloride) (PVC) that was subjected to a treatment capable of decreasing the simultaneous mass transfers occurring between liquid food (or simulant) and PVC packaging. The storage modulus (GЈ), loss modulus (GЉ), and the loss angle (tan ␦), have been used to determine the glass transition temperature using a Rheometric Scientific Dynamic Analyzer. Young's modulus was measured on a dynamometer, and a morphological characterization was carried out with an optical microscope. The obtained results show that treated PVC behaves like a composite material, which is in agreement with a previously established model.

Gelation of poly(vinyl chloride) inside a single screw extruder and its effect on product properties

Journal of Vinyl and Additive Technology, 2018

Two resin formulations were extruded through a single screw extruder, equipped with a single flighted screw, rotating at 10 rpm, at different barrel temperature settings, which resulted in different melt temperatures measured in the adapter zone. The extrudates were subsequently subjected to assessments of the gelation level by three different methods: differential scanning calorimetry (DSC), capillary rheometry (CR), and solvent absorption (SA). The pros and cons of these methods are discussed. It appears that DSC is the most accurate technique for the quantitative determination of the gelation degree (GD), with the drawback that the specimen size is very small. The CR technique, based on measurement of entrance pressure, is also capable of providing reasonable estimates of GD, with some potential inaccuracies as a result of difficulties associated with measurement or assessment of temperature rise. The SA technique provided qualitative assessments of GD in agreement with the other two methods. Ultimate tensile strength, elongation at break, solid density, and color change were also measured and were correlated to melt temperatures and the corresponding GD. Extruded specimens having GDs in the range of 60%-90% possessed satisfactory properties for both resin formulations.