There are a number of the techniques. Depends on the magnitude of the heat conductivity and temperature range mostly.. For example simple procedure with thermal analyzer - 10.1016/0040-6031(88)87254-X; 10.1016/0040-6031(85)85081-4. Same device, another principles - 10.1016/0040-6031(94)85058-5; 10.1007/s10973-015-4429-z; 10.1016/j.est.2016.02.010. Laser flash technique - 10.1068/htjr061, see also ASTM 1461 standart