Detection and characterisation of crystals in a polymer or polymer mixture is best performed using wide angle X-ray scattering (WAXS). The ordering, close packed crystals give a diffraction pattern due to coherent scattering from the regular array of atoms (molecules) in the crystal. The diffraction peaks are characteristic of crystal type and atom spacing and can be compared with known patterns from the same polymers.The X-ray peaks can be used to calculate crystallinity and peak width can be used to calculate the crystal thickness. WAXS is performed on the material without any change being made.

Differential scanning calorimetry (DSC) can be used to detect the melting enthalpy as a sample of the polymer mixture is heated at a controlled rate. The melting temperature can be measured from the onset or peak of the melting endotherm and compared with known melting temperatures for each of the  polymers in the mixture. The area under the melting peak (melting enthalpy) can be used to calculate crystallinity if known enthalpies for pure crystals of the same polymer are available to ratio. An uncertainty is, because the polymer mixture must be heated (changed) and the crystals melted, that means the sample changes during the DSC scan.

Polymer mixtures usually crystallise as the pure components. A mixture of two polymers is likely to form crystals of each polymer separately upon crystallisation, even if the polymers are miscible in the mixture before crystallisation. Crystal structures are ordered and close packed, requiring elimination of foreign materials from crystallising structures, thus a mixture of two miscible polymers will phase separate during crystallisation.

I'm not really sure how you think to correlate time and cristallization. Anyway, polymer blends crystallization can be characterized by DSC, there is some methods which can be used for crystallinity determination.

NMR, especially solid state CP-MAS.

Detection and characterisation of crystals in a polymer or polymer mixture is best performed using wide angle X-ray scattering (WAXS). The ordering, close packed crystals give a diffraction pattern due to coherent scattering from the regular array of atoms (molecules) in the crystal. The diffraction peaks are characteristic of crystal type and atom spacing and can be compared with known patterns from the same polymers.The X-ray peaks can be used to calculate crystallinity and peak width can be used to calculate the crystal thickness. WAXS is performed on the material without any change being made.

Differential scanning calorimetry (DSC) can be used to detect the melting enthalpy as a sample of the polymer mixture is heated at a controlled rate. The melting temperature can be measured from the onset or peak of the melting endotherm and compared with known melting temperatures for each of the  polymers in the mixture. The area under the melting peak (melting enthalpy) can be used to calculate crystallinity if known enthalpies for pure crystals of the same polymer are available to ratio. An uncertainty is, because the polymer mixture must be heated (changed) and the crystals melted, that means the sample changes during the DSC scan.

Polymer mixtures usually crystallise as the pure components. A mixture of two polymers is likely to form crystals of each polymer separately upon crystallisation, even if the polymers are miscible in the mixture before crystallisation. Crystal structures are ordered and close packed, requiring elimination of foreign materials from crystallising structures, thus a mixture of two miscible polymers will phase separate during crystallisation.

You can perform DCS analysis as well as X-ray diffraction. From DSC you can obtain information not only on the crystallization temperature shifts, but you can also take information from the rate of crystallization by measuring the time that this process need from the beginning of the peak to the end.

XRD, DSC and solid state NMR can be used 

As we use in our work, DSC is a proper choice with reliable results.

DSC, NMR, X-Ray. Dipends of the matrix. For me DSC it's more easy and fast tecniques for crystallization study.

among above mentioned methods which one is most accurate for initial crystallization

As mentioned by the others, coupling DSC and XRD can be a good choice. DSC can be used in non-isothermal and isothermal methods to study the crystallization. non-isothermal method (increasing temperature with a defined rate from low temperature to above melting point and subsequent cooling) can give you an idea of the crystallization rate and melting enthalpy while isothermal crystallization method (raping cooling to the desired temperature after melting) can be used to study the effect of time on the crystallization at any desired temperature. Although there are few polymer pairs that can co-crystallize, but blending can affect the crystal types that are formed during crystallization of phases. Here, coupling XRD with DSC results can help you to determine whether new crystals (initiated at the interface of the phases) were formed during crystallization or not.

Moreover, using a polarizing microscope equipped with a hot-plate, you can get beautiful images of your crystals (if their size is large enough)!!

Characterisation of crystals in a polymer or polymer mixture is determined form WAXS.  The diffraction peaks are characteristic of crystal type and atom spacing and can be compared with known patterns from the same polymers.The X-ray peaks can be used to calculate crystallinity and peak width can be used to calculate the crystallite size. 

The melting temperature can be measured from Differential scanning calorimetry (DSC) noting the onset or peak of the melting endotherm and compared with known melting temperatures for each of the polymers in the mixture. 

You can see examples in this paper

Journal of Thermal Analysis and Calorimetry, September 2005

Polymorphous transitions in cocoa butter

D. Fessas, M. Signorelli, A. Schiraldi

http://link.springer.com/article/10.1007%2Fs10973-005-6934-y

http://link.springer.com/article/10.1007%2Fs10973-005-6934-y