Gy. Bertalan

Role of interfacial layers in the properties of particle-filled polyolefin systems

Abstract Modified interfacial layers were studied in polypropylene—calcium carbonate systems compounded in a single-step process with a surface-active agent and an elastomer simultaneously. Samples with etched and non-etched surfaces were investigated by dielectric spectroscopy and scanning electron microscopy. An increase in the thickness of the interfacial layer was brought about by the increasing elastomer content of the system. However, when the concentration of the latter exceeded a critical upper limit, a new disperse elastomer phase could be observed in the matrix. The value of the critical concentration depends upon the type of elastomer and it is a characteristic parameter for a given polymer—elastomer system. Deformations and failure in the composite system are determined by the interfacial layer. A thick elastomer interphase around the filler particles acts as a bumper layer and stops the crazes. The interactions between the components and the change in the mechanical properties induced by the presence of named additives were also investigated by mechanical spectroscopy.

Thermoanalytical study of nucleating effects in polypropylene composites: III. Intumescent flame retardant containing polypropylene

Engineering application of polypropylene requires the employment of flame retardants. Reactive compounding of ammonium-polyphosphate and synergist additives with polypropylene is an effective way for forming flame retardant polypropylene. Both the ammonium-polyphosphate and the additives used for improving its performance effect the crystallization and melting behavior of polypropylene. Encapsulation of flame retardant additives with appropriate elastomer, in order to improve their water resistancy, causes further changes in degree of crystallinity and consequently in the mechanical properties.

Effect of interface modification on the photo-stability of pigmented polyethylene films

The deterioration of differently stabilised and pigmented high density polyethylene films was investigated by DSC and UV spectroscopy methods in the course of accelerated photo-ageing and compared to earlier XPS and gel-content results. Unexpectedly quick destruction of phthalocyanine containing film was observed and explained by the adsorptive removal of the stabiliser from the polymer matrix. In the pigment (filler)-solvent-stabiliser model systems the high susceptibility of hindered phenol type heat-stabiliser to adsorb on talc and phthalocyanine pigment was proved by UV spectroscopic measurements. Surface coating of the talc and pigment with a reactive surfactant considerable reduced the adsorption capacity and thus improved the photo-stability of the pigmented film.

Role of interface modification in filled and flame-retarded polymer systems

New reactive surfactants (RS) and synergistic reactive surfactants (SRS), containing reactive groups and longer unsaturated apolar hydrocarbon chains have been synthesised and applied in filled and flame-retarded polymer systems, respectively. These additives are capable of reactions with the polymer matrix and the disperse phase as well. The reaction of these compounds with polyolefins was proven on model system by surface analysis, while their reaction with fillers was demonstrated by DSC. The interface modification in filled/reinforced polymer systems and polymer blends resulted in improved mechanical properties, while in pigmented PE it contributed to higher photostability. Furthermore, the efficiency of intumescent flame retardant additives in polyolefins could be enhanced.

Modified interfaces in multicomponent polypropylene fibers

Increased strength, adsorption capacity and improved resistance against a flame of split film polypropylene fibers could be achieved by applying particulate additives with modified interphases. In the presence of an elastomer interlayer a high drawing ratio could be achieved. A reactive surfactant additive was more appropriate for increasing the tensile strength of filled fibers, while oil adsorbent fibers required fillers covered with non-reactive surfactants for improving the adsorption capacity. Model experiments using XPS and DSC methods and SEM analysis were applied for studying the cause of these effects. The migration of flame retardant additives to the surface of PP fibers could be followed using the XPS method. This advantageous effect can be promoted by silicone interphase.

Thermoanalytical study of nucleating effects in polypropylene composites. II. Filler and elastomer containing polypropylene

Interfacial structure plays an important role in the performance of polypropylene composites. Transcrystalline interfacial layer were determined in talc filled polypropylene. The crystallization and melting behaviour of talc and CaCC3 filled polypropylene could be modified with smaller amount of additives like elastomer and surfactants. Through the effect of these additives the structure of interface and the degree of crystallinity could be controlled in filled polypropylene.

Structure-property relationship in flame retardant polymers

Mg(OH)2 and ammonium polyphosphate (APP) based flame retarded polyethylene (PE) and polypropylene (PP) compounds were prepared in a plastograph and the influence of additive systems on the microstructure, mechanical, and melt characteristics of the compounds was investigated by DSC, Raman microscopy, and rheological measurements. A high loading of Mg(OH)2 has a nucleating and crystallinity reducing effect in low density PE. The crystallinity reducing effect was explained by formation of a partially ordered but noncrystallized interfacial region around the flame retardant (FR) particles. The nucleating effect was hindered when the particles were embedded in elastomer. The nucleating effect of APP in PP was also reduced when a polyol layer surrounded it. The incorporation of boroxo siloxane (BSil) elatomer FR synergist, introduced additionally to the above additives, resulted in a further nucleating effect, and increased the melt viscosity. Polymer layered montmorillonite, applied instead of BSil elastomer, did not influence the crystallization; however, it increased the melt viscosity and improved the flame retardancy.

THERMAL ANALYSIS OF FIBRE FORMING POLYMERS Multiphase systems

Different levels of fibre technologies and application, from synthesis to degradation has been studied using the methods of thermal analysis. Recent results of these studies on synthetic and natural fibres are summarized. The effect of chemical and physical modification of polyolefin fibres as well as the synthesis of polymer emulsion used as additive in fibre technologies could be followed by DSC, DMA, TG methods.

Mechanism and kinetics of the hydrochloric acid initiated polymerization of ?-caprolactam: 2. Identification of the kinetic model

SummaryA quantitative description of the hydrochloric acid initiated polymerization of caprolactam (CL) based on the previously proposed mechanism is given. Essential parameters were identified by strategy mainly based on principal component analysis. Our kinetic model is in good agreement with experiments and describes specific features of the kinetics of the process with the suggested parameters.

Mechanism and kinetics of hydrochloric acid initiated ?-caprolactam polymerization: 1. The role of stereoelectronic control and acid catalysis

A mechanistic scheme is suggested for lactam polymerisation initiated by hydrochloric acid on the basis of the general mechanism put forward earlier by Bertalan et al. According to this mechanism during the polymerization conditions are created which can initiate further polymerizations resulting in a characteristic inflection type kinetic curve. Experimental results can be well interpreted qualitatively on the basis of this mechanism, and therefore it can serve as a starting point also for a quantitative kinetic model.