Untersuchungen an kautschukmodifiziertem PVC

Abstract

ZUSAMMENFASSUNG:An Mischungen verschiedener Pfropfkautschuke auf ABS-, MBS-und AMBS-Basis rnit PVC werden die Beziehungen zwischen chemischer Zusammensetzung, morphologischem Aufbau und Eigenschaften untersucht. Mit steigendem Pfropfungsgrad lassen sich die Pfropfkautschuke besser in PVC dispergieren, und der WeiBbruch der Mischungen verringert sich unter gleichzeitiger Abnahme der Schlagzahigkeit. Die besten Eigenschaften erhalt man bei einer KautschukteilchengroBe von etwa 200 nm; die chemische Zusammensetzung von ABS-Kautschuken ist fur eine 75 S/25 AN-Pfropfkomponente optimal, die auf Grund der Ubereinstimmung ihres Loslichkeitsparameters (6 = 9,8) mit dem PVC-Wert (6 = 9,6) auch gute Vertraglichkeit The composition-morphology-property relationships are investigated for a series of ABS-, MBS-and AMBS-graft copolymer blends with PVC. The dispersibility of the graft copolymers in PVC improves with increasing grafting levels, while both impact resistance and tendency to stress whitening decrease. With respect to particle size, an optimum in the properties is found for particles of 200nm. The grafting composition in ABS polymers giving the best results is a 75 S/25 AN copolymer, which is highly compatible with PVC. This high compatibility coincides with the good agreement between the solubility parameters for this SAN copolymer (6=9,8) and PVC (6=9,6). In MBS polymers increasing styrene levels lead to more transparent blends with PVC because of better matching of the refractive indices. However, impact strengths decrease at the same time because of deteriorating compatibility. Methyl methacrylate, having just the opposite effects to styrene, can be favourably used in combination with styrene or SAN by a stepwise addition of the graft monomers which is shown to result in optimum properties for MBS or AMBS polymers.Electron micrographs of the stress whitened areas reveal that the degree of crazing is negligible in comparison to other rubber modified thermoplastics. Instead of crazes, many cavities within the graft copolymer particles are found which correlate in size and frequency with the extent of stress whitening. Measurements of the density decrease in the stress whitened areas agree quantitatively with evaluations of the volume increase determined from the changes of the particles sizes in the electron micrographs. An analysis of the polymerization of the scattered light shows that shear bands or birefringence effects can be excluded as the cause of stress whitening. Based on the direct observation of the stress whitened areas and on the dependence of the scattering on wavelength and angle, the light scattering effects must be caused by the accumulation of the cavitiesin bandlike zones. These zones mark the otherwise invisible shear bands occurring on strong deformations of the PVC matrix. The initiation of the shear bands is facilitated by the incorporation of the graft copolymer particles which in this way enhance the impact strength of PVC.

Mechanical properties and deformation behaviors of acrylonitrile‐butadiene‐styrene under Izod impact test and uniaxial tension at various strain rates

“…For ABS, it is well known that the deformation mechanisms include crazing [33, 34], shear yielding [35], cavitiation of rubber particles, and the induced yielding in matrix [36]. Combining the results of TEM and SEM obtained here, it is found that craze, cavitation of rubber particles, and the induced shear yielding in SAN matrix coexist in ABS‐L blend under impact condition.…”

Synthesis and characterization of high‐impact polystyrene using a multifunctional cyclic peroxide as the initiator

“…HIPS is formed by 6–15 wt % of a rubber dispersed in the form of particles into a polystyrene (PS) matrix where the dispersion is stabilized by the interfacial agent composed of a graft copolymer (rubber ‐g‐ PS) formed “ in situ” during the HIPS synthesis 2, 3. HIPS can be obtained by dissolving an appropriate amount of a rubber, usually polybutadiene (PB) or styrene–butadiene copolymers (SB or SBS), in styrene, followed by the in situ polymerization of the styrene monomer.…”

Rubber–Plastic Blends: Structure–Property Relationship

“…However, a single size distribution of very small particles makes the ABS resins stiff, glossy, and less tough, while big particles impair stiffness and gloss, but improve toughness. The optimum mean particle size for a combination of toughness, stiffness, and surface gloss is about 0.3-0.5 μm [206]. Gloss is largely dependent on particle size [207].…”

“…The proportion of grafted SAN in the interface depends on the total amount of AN added and on the distribution of the grafted polymer between internal and external grafts. The proportion of graft copolymer included rises with increasing particle size and decreases with cross-link den sity [206]. Emulsion-grafted small particles exhibit a closed shell of graft copolymer on their surface.…”