EXXPOLB nietallocene catalyst technology fcaturing very high-productivity catalyst systems is expected to provide ethylene polymer compositions that show excellent oxidative stability based on their minimal unsaturation contcnt and low innocuous metal residue of a non-acidic nature. Mctallocene ethylene polymers such as inLLDPE should bc comparable to the most stablc, commercial polyethylencs such as liiicar low-density polyethylenes (LLDPE) from the UNIPOL@ gas phase PE process.As background, the oxidation behavior and stabilization casc of "total residue" polyolefins based on Ziegler-Natta or Cr catalysis systcms are reviewed. The interacting effects of polymer stnictiire (i.e., tertiary hydrogcn and unsaturation) and catalyst residue are discussed in tctms of competing degradation reactionsc.g., chain brcakage, chain cnlargcmcnt (or cross-linking) and chain branching. The metal (Ti, V and Al) and chlorine residucs from Ziegler-Natta catalyst systcms and the Cr residue for Cr catalyst systems can play a role in adversely affecting polymer oxidativc stability. The residue levels and thcir naturc govcm whether thcrc is an appreciable crfcct on oxidativc stability, and therefore the stabilization requirements.Discussed are themio-oxidative studies undcr melt processing conditions which compare sclccted EXXPOL@/UNIPOL@ niLLDPEs with several state-of-the-art Ti/Mg and Cr catalyzed LLDPE from thc UNIPOL'Y gas phasc PE process and a high-pressure, low-density polyethylene (HP-LDPE). Standard inclt flow and discoloration tests are combined with specialized experimcnts using dynamic oscillatory shear rhcometry and size exclusion chromatographyvisconietry to illustrate perfomiancc shifts due to polymer composition differences undcr melt proccssing conditions. The advantages of dynamic niclt rheonietry are illustrated in tcims of scnsitivity to subtle degradation changes in molecular structure. EXXPOL@/UNIPOL@ niLLDPE having low unsaturation and metal residue which are non-catalytic to auto-oxidation show excellent intrinsic oxidative stability. The discoloration resistance of EXXPOL'B/UNIPOL@ mLLDPE is high, comparable with HP-LDPE and the high-activity Cr catalyzcd LLDPE. Stabilization case for EXXPOL@/UNlPOL'~ inLLDPE is equivalcnt to product counterparts (similar MI and density) made using high-activity, state-of-the-art Cr or Ti/Mg catalyst systenis designed for use in the UNIPOL@ gas phasc PE process.
The pressure‐volume‐temperature behavior for both solid and molten polypropylene was determined for pressures up to 618 atmospheres. These data were measured with a newly developed compressibility device capable of obtaining precise and accurate data. Compressibilities calculated from the experimental data compared favorably to the limited existing literature data. Constants were determined for the Spencer‐Gilmore polymer equation of state for both the solid and molten material.
synopsisThe application of infrared spectrometry in the overtone and combination regions (1.0-2.7 p wavelengths) for determining chemical groups in polymeric materials was studied. Various groups such as C&, NH, and C=O were assigned to spectra of polyethylene, polypropylene, nylon 66, polyisobutylene, polystyrene, polyvinyl acetate, polyvinyl chloride and a polyvinylidene-polyvinyl chloride copolymer. The technique for sample preparation and experimental procedure is given. It is suggested that these spectra assignments in the overtone and combination regions can be used to obtain relative degradation measurements, determine water adsorption, quantitatively measure physical polymer blends, and finally to study polymer reaction kinetics.
Prior research on the melting behavior of ethylene copolymers and branched polyethylenes could not be effectively evaluated since there were large differences in the levels of comonomer contents. The present research was undertaken to determine additional data so that an overall evaluation could be made. A consideration of the experimental data of the present work and earlier research data showed that methyl side groups caused less diffuse melting and less melting point depression than either ethyl groups or polyethylene branches. In addition, it was found that the Flory equation can be used to describe the relation of melting point depression to foreign group concentration for propylene copolymers. The equation did not hold for 1‐butene‐ethylene copolymers or branched polyethylenes. For these materials the Wunderlich modification of the Flory equation applied. Activity values for both 1‐butene‐ethylene copolymers and branched polyethylenes gave a common correlation with foreign groups. Enthalpy and entropy fusion data for ethylene copolymers and branched polyethylenes were also determined. It was also shown that good agreement was found between crystallinities for these materials determined independently by differential thermal analysis and x‐ray analysis.
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