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 ...

SynopsisThe influence of ferrocene on the flammability and smoke generation behavior and thermal characteristics of poly(viny1 chloride) (PVC) and poly(viny1 alcohol) (PVA) was examined in order to understand the basis of ferrocene's activity as a flame-retardant and smoke-suppressant additive. Ferrocene increased char formation in PVC by 20-60% while increasing the limiting oxygen index (0.Z.) by 15-19'36. Little char was found either with or without ferrocene in PVA, which had little improvement in 0.1. Visible smoke was significantly decreased by ferrocene in PVA and in PVC of low to moderate molecular weight, but was unchanged in high molecular weight PVC.Thermogravimetric analyses and thermal degradation experiments showed that ferrocene promotes early weight loss and crosslinking in PVC. This effect is coincidental with the formation of ferricenium cation, which was identified by its visible spectrum and which may be a possible catalyst. Smoke inhibition of PVA by ferrocene occurs predominantly through gas-phase processes, while in PVC evidence and analogy for activity in both the gas phase and condensed phase are found.0.1. of PVC appeared to vary with molecular weight of the polymer.

X-ray photoelectron spectroscopy (XPS or ESCA) was used to examine the outermost 100 A˚ of selected elastomer substrates, and to classify the predominant reactions that occur there between the substrates and trichloroisocyanuric acid (TCICA). About four monolayers deep, this surface region represents the locus of interfacial and adhesive processes. From these experiments, we concluded the following: (1) at the outermost surface of NR, substitution reactions of TCICA predominate, but a minor amount of addition is also evident; (2) addition and substitution reactions compete on the surfaces of the butadiene-containing polymers, BR and SBR; (3) no detectable functionalization by TCICA takes place on EPDM or CIIR — polymers which lack sufficient olefinic sites for surface modification; (4) isocyanuric acid or other nitrogenous residues are present on treated surfaces before washing; (5) reconstruction of functionalized surfaces may occur upon swelling for extended periods; (6) surface oxygen levels in these experiments were variable, and could not be relied upon as indicators of the functionalization chemistry.

Most of the flame-retardant technology now used with elastomers has been known for some time. Advances have been made in recent years in the understanding of elastomer combustion and inhibition mechanisms, in the measurement and control of visible smoke generation from elastomers, and the toxic effects of combustion atmospheres. By integrating existing technology with recent developments and the likely advances of the future, elastomeric materials will continue to receive acceptance for a wide variety of applications. Author's note: A review stressing quantitative aspects of polymer combustion has recently appeared.

A methodology was developed to estimate individual hysteresis contributions arising from the carbon black network, polymer free chain ends and effective polymer network chains. The estimation technique was applied to rubber compounds formulated with linear polymers of varied number-average molecular weight (Mn) from each of three different series. The three series corresponded to polymers modified with either zero, one or two tin ends per chain. In general, the relative hysteresis contributions depend on strain amplitude and Mn. For unmodified polymers at strain amplitudes from 0.02 to 0.07, and with Mn in the neighborhood of 150 kg/mole, each of the three hysteresis sources contributes about one-third of the total tan δ. With respect to shear loss modulus (G″), the carbon black network contributes about 60%, while free chain ends and the effective polymer network chains each contribute about 20%. At the same Mn and strain conditions, tin end-modified polymers reduce G″ and tan δ by as much as 60%, in comparison to their unmodified counterparts. The benefit is achieved primarily through reductions of up to 85% in the carbon black network contribution to hysteresis. Since the hysteresis contribution from free chain ends is not reduced so much by tin end-modification, the greatest potential for additional tan δ benefits lies in further free chain end reduction. In addition, it was found that tin end-modification has no measurable effect on the hysteresis contribution from effective network chains. Further, the analysis showed that an ineffective polymer network chain provides approximately ten times the hysteresis and one-half the elasticity of an effective network chain, at the test conditions of the current study. In general, the quantitative results, and some qualitative results as well, will change with compound composition and with temperature. Consequently, the development of a methodology, one that allows estimation of individual hysteresis contributions from different sources, is a major component of the present study.