RHEOLOGICAL STUDIES ON REACTION INJECTION MOLDING PROCESS WITH A SLIT MEASURING SYSTEM

A non-reacting system and a reacting system are run with an on-line slit rheometer devel-oped by the authors.It is found that the polyurethane-urea system behaves slightly elastic and theZaremba-Fromm-Dewitt model may be employed to describe its rheological behaviors.After the geltime,the inside pressure of the testing materials varies dramatically.Reports in this respect have notbeen found in literature,as yet its mechanism warrants further studies.

Investigation on UV-curing Reprocessable Thermosets Bearing Hindered Urea Bonds and Their Composites with Modified Zinc Oxide Nanoparticles

In this study,a series of hindered urea bond(HUB)containing polyurethane-urea methacrylate prepolymers and a none HUB containing polyurethane methacrylate prepolymer were prepared using isobornyl methacrylate as the reactive diluent via one-pot procedure.The prepolymers were characterized fully by various techniques.Then,their thermosets were fabricated via UV curing in presence of a photo initiator,and their mechanical property and thermal behavior were investigated and compared.Different from the none HUB containing thermoset,the HUB containing thermosets(defined as PUT)could be recycled and reprocessed by hot press under relatively mild conditions with high recovery ratio of mechanical property.Furthermore,zinc oxide(ZnO)nanoparticles were modified with 3-(trimethoxysilyl)propyl methacrylate and the modified ZnO(defined as ZnO-TPM)was dispersed and polymerized into PUT matrix to prepare their nanocomposites.The influence of ZnO-TPM on the mechanical performance of the composites was evaluated,which indicated that the Young’s modulus and tensile strength increased gradually to the maximum values at ZnO-TPM content of 1 wt%and then decreased.The composites also displayed good reprocessability with improved recovery ratio compared to the pure PUT sample.In addition,the composite materials exhibited strong UV absorption capacity,implying their potential application in the circumstance where UV-shielding was required.

Preparation and properties of poly HTBN-based urethane urea/organo reactive montmorillonite nanocomposites

With ultrasonic assistant mixing way, an intercalated mixture of polyol/ organo reactive montmorillonite （ORMMT） was pretreated. The prepolymer composed MMT clay was prepared by reaction of polyol/ORMMT mixture with toluene diisocyanate （TDI）. The resultant prepolymer reacted with extender （DMTDA） and then the polyur- ethane-urealorgano reactive montmorillonite （PUUIORMMT） nanocomposites were obtained. The structure, morphology and properties of PUU/ORMMT nanocomposites were characterized by FT-IR, TEM, AFM, strain-stress machine, TGA, and dynamic mechanical analysis （DMA）. The results showed that when tl-m OMMT content is 3%, the PUU/ORMMT nanocomposities performed super mechanical properties. Because of the presence of ORMMT, both Tg of the soft segment and tan5 of the PUU increased, and the decomposition temperature for the first step and the second step increased respectively. TEM images showed that the organophilic MMT particles in the PUU composite exhibit a high degree of intercalation and exfoliation.