Filler flocculation was followed for silica filled compounds containing various alkoxy silanes and non-silane type polar additives. The methodology employed in this paper permitted a quantitative characterization of filler flocculation and polymer-filler interactions after heating the compound under conditions that simulated vulcanization. With the addition of trialkoxy silanes, the reduction of filler flocculation and the degree of polymer-filler interactions were found to depend on the type and the concentration of silane added, and on the mixing drop temperature (Td) used. Greater polymer-filler interactions and flocculation suppression were obtained with a compound containing a tetrasulfane when compared to that containing either a disulfane or a monofunctional-silane. Polar additives such as an amine compound and a sugar alcohol did not reduce the silica flocculation during simulated vulcanization because they were dewetted from the silica surface upon heating. The filler flocculation process was monitored by following the change of dynamic storage moduli using an on-line rheometer. The flocculation process order and process constant were extracted from the non-linear regression analysis of the kinetic data. These kinetic parameters were used to quantify the suppression of filler flocculation by the additives used. Filler flocculation was found not to be affected by the vulcanization process because it occurred prior to the onset of cure.

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The change in Mooney viscosity (ML1+4) with aging was followed for silica filled compounds containing various silanes and polar additives. Several mechanisms for the aging stability are postulated and evaluated through experimentation. The type of silane or polar additive used can cause the ML1+4 to increase or even decrease during aging. When bis(triethoxy silanes) are used in silica filled rubbers, the ML1+4 growth during aging is caused by hydrolysis. Silica-silica bridging was found to be responsible for the ML1+4 growth in rubber compounds containing a more thermally stable polysulfide or a sulfur-free bis(triethoxy silane). When the bis(triethoxy silane) is bis(3-triethoxysilylpropyl) tetrasulfide (TESPT), a fraction of TESPT is attached to the unsaturated rubber to give polymer-silica attachments. These attachments further enhance the hydrolytic ML1+4 increase during aging. Chemical coating of the silica with a monofunctional silane or a physical coating with a trialkyl amine compound effectively stops the ML1+4 increase upon aging. The prevention of ML1+4 growth is so efficient that a reduction in the ML1+4 can be realized by absorption of ambient moisture. The extent of ML1+4 reduction caused by moisture depends on the degree of hydrophobation of the coated silicas. Hydrolytic stability was also studied with an amine or a sugar fatty acid ester that formed either strong or weak polar associations to the silica.

SynopsisThe preparation, analysis, testing, and structure determination of ultrahigh impact rubbertoughened polycaprolactams (nylon 6) are described. Partially unsaturated hydrocarbon rubbers were used for this purpose. They were functionalized by reaction either in solution or in bulk with maleic anhydride to give rubbery "ene" adducts containing varying amounts of pendent succinic anhydride. Tough, rigid, thermoplastic engineering resins with notched Izod impact strengths of 750-1000 J/m were prepared by briefly melt-blending these adducts with nylon 6. Properties of the blends could be affected by the type and amount of elastomer used, the anhydride content, the type of nylon, the mixing conditions and the test conditions. Fractionation by coacervation in m-cresol/cyclohexane of a typical resin containing 20% by weight of functionalized rubber showed approximately 35% of a rubber-nylon graft, along with a few percent of free rubber dispersed in the nylon 6 matrix. A comb-block copolymer structure for the graft and a model for its formation are proposed, consistent with analyses of the fractions. Some of the blends prepared with partially hydrogenated medium vinyl polybutadiene-maleic anhydride adducts displayed a retention of impact properties at low temperatures which was superior to that obtainable with a similarly prepared EPDM-modified nylon 6. Transmission electron microscopy of a blend containing an anhydride-modified hydrogenated medium vinyl polybutadiene showed a morphology consisting of a nylon matrix containing finely dispersed, irregularly shaped, 0.03-0.55 pm rubber domains in which were found even smaller domains of nylon. INTRODUCTIONIn the unmodified state polycaprolactam, nylon 6, resin has a sufficient combination of good tensile and flexural properties, high heat distortion temperature, and an appreciable notched Izod impact strength on the order of 50 J/m that it is considered to be among the first "engineering resins." By chemically grafting the nylon to a dispersed rubber, heterophase blends with impact strengths on the order of lo00 J/m, well in exces of so-called "high impact" resins, can be obtained, and the blends might be more properly named " ultra-high impact" resins.Toughened blends of nylon 6 were prepared in 1974 by Ide and Hasegawa,' who recognized that the dispersion of polypropylene in nylon 6 was improved when the PP was first functionalized by grafting with maleic anhydride. They 2332LAWSON, HERGENROTHER, AND MATLOCK attributed this to the presence of an interfacial agent which was formed through the reaction of the anhydride with amine chain ends. The impact strengths of their blends approached ca. 250-325 J/m. Blends of nylon 6 and rubber which show toughening have been described by Cimmino et a1.,2 Martuscelli et al.,3 and G r e~o .~ In these reports, the blends were prepared from nylon 6 and an EPM copolymer grafted with maleic anhydride in the presence of peroxide; in some cases the blends were prepared by the in s i b polymerization of caprolactam in the presence of ...

synopsisCopolymers of poly(ethy1ene terephthalate) (PET) containing 1-24% poly(diethy1ene glyco1)terephthalate (PDEGT) were prepared and characterized by infrared spectra. The energy and entropy of activation for the thermal degradation were measured for these copolymers and for the PDEGT. These activation energies and entropies were found to decrease steadily with increasing diethylene glycol content. From these measurements the mechanism of degradation of PDEGT was found to be different from that of PET. Fibers prepared from seven different copolymeric compositions were heat-aged a t 121OC and 204°C for 24 hr. From the changes observed in intrinsic viscosity, per cent ether, hydroxyl and carboxyl endgroups during heat aging it became apparent that the mechanisms for decomposition are operative below melt temperatures and can rapidly destroy such copolymers.