title: Rheology of urethane dimethacrylate and diluent formulations.
abstract: OBJECTIVE
  The purpose of this study was to measure the viscosity of resin formulations and investigate the relationship between diluent percentage and temperature.
  
  
  METHODS
  Resin formulations were prepared using UDMA and either TEGDMA or HEMA, or HPMA, as diluents at different percentages. Viscosities were obtained with a Bohlin Rheometer at 23 degrees C for all formulations, and at 37 and 60 degrees C for selected formulations.
  
  
  RESULTS
  The viscosity of the formulations exhibited Newtonian behaviour and decreased as the percentage of the diluent monomer increased, especially up to 40% of diluent. Linear regressions relating log(viscosity) and mass percent diluent, were obtained in the range 20-80% diluent. Viscosity also decreased as the temperature increased. Activation energies were calculated from Arrhenius plots, and ranged from 16.2-23.4 kJ mol-1.
  
  
  CONCLUSIONS
  The viscosity of the resins controls the flow properties and thus has a significant effect on the deployment of the respective monomers.
authors.affiliation: University of Manchester Dental School, UK. n.silikas@stud.man.ac.uk
authors.forename: N
authors.initials: N
authors.lastname: Silikas
authors.forename: D C
authors.initials: DC
authors.lastname: Watts
mesh_terms: D008689:Methacrylates / Q000737:chemistry*; D011092:Polyethylene Glycols / Q000737:chemistry; D011109:Polymethacrylic Acids / Q000737:chemistry; D011140:Polyurethanes / Q000737:chemistry*; D012117:Resins, Synthetic / Q000737:chemistry*; D012212:Rheology; D014783:Viscosity
chemical_list: D008689:Methacrylates; D011109:Polymethacrylic Acids; D011140:Polyurethanes; D012117:Resins, Synthetic; C029824:urethane dimethacrylate luting resin; C020946:triethylene glycol dimethacrylate; D011092:Polyethylene Glycols; C005044:hydroxyethyl methacrylate; C032802:hydroxypropyl methacrylate