A new type of controlled release fertilizers coated with polyurea was prepared. The granulated urea was firstly changed into a liquid urea by heating as the coating liquid. By spraying uniformly the urea was coated with the polyurea synthesized by the reaction of isocyanates with a liquid urea. The effects of different modifiers on N release characteristics of polyurea-coated urea (PCU) were st...

We summarize the results of the response of monolithic steel plates and steel-polyurea bilayer plates to impulsive blast loads produced in direct pressure-pulse experiments, focusing on the deformation and failure modes of the plates. In these experiments, an impulsive pressure pulse is applied to a steel plate through water or soft polyurethane that simulates shock loading with a peak pressure...

0167-6636/$ see front matter 2009 Elsevier Ltd doi:10.1016/j.mechmat.2009.09.009 * Corresponding author. Address: University of Ca Mechanical and Aerospace Engineering, 4909 Eng 9500 Gilman Drive, La Jolla, CA 92093-0416, USA. T E-mail address: [email protected] (S. Nemat-Nasser). Results of computationalmodeling and simulation of the response ofmonolithicDH-36 steel plates and bilayer steel-polyure...

Herein, we report on the synthesis and characterization of enzymatically labile polyureas for use as a tissue-engineered ligament scaffold. Polyureas were selected due to their excellent tensile properties, fatigue resistance, and highly tunable nature. Incorporation of a collagenase-sensitive peptide into the backbone of the polyurea provided a means to confer cell-responsive degradation to th...

Abstract Polyurea as one kind of polymer is widely used in the field protective under blast and impact loading. matrix with nanofillers has superior mechanical properties than pure polyurea. In this work, order to develop polyurea thermal stability high properties, using Silicon carbide (SiC) nanofillers, nanocomposites different content SiC nanoparticles were prepared via in-situ polymerizatio...

The concept of spraying thick layer of polymer material onto metal plate has recently received considerable interest in many civilian and military applications. There are numerous analytical and numerical solutions for single thin plates (membrane) made of either a steel or an elastomer. However, solutions for composite plate made of both of the above constituents are lacking. The objective of ...

This paper addresses the applicability of the Time–Temperature Superposition Principle in the dynamic response of a polyurea polymer at high strain rates and different temperatures. Careful and extensive measurements in the time domain of the relaxation behavior and subsequent deduction of a master-relaxation curve establish the mechanical behavior for quasistatic deformations over a time range...

4.1 CHAPTER SUMMARY The effect of the variables of polydimethylsiloxane (PDMS) soft segment length, hard segment type and content as well as choice of chain extender (its MW and symmetry) on the morphology of segmented polyurethane and polyurea copolymers was investigated. The methods of dynamic mechanic analysis, small angle x-ray scattering, atomic force microscopy, and mechanical testing wer...

Dynamic mechanical analysis (DMA) and ultrasonic measurements were carried out to study the temperature and frequency dependences of viscoelastic properties of polyurea. Master curves of Young’s storage and loss moduli were developed from the DMA data. Relaxation spectra were subsequently calculated by means of two approximate models, and the apparent activation energy of molecular rearrangemen...