Percentage of crystallinity

This relationship is sketched in Fig. 4.7a, which emphasizes that P, must vary linearly with 6 and that P, ° must be available, at least by extrapolation. The heat of fusion is an example of a property of the crystalline phase that can be used this way. It could be difficult to show that the value of AH is constant per unit mass at all percentages of crystallinity and to obtain a value for AHj° for a crystal free from defects. Therefore, while conceptually simple, the actual utilization of Eq. (4.37) in precise work may not be easy. 

The properties of commercial polypropylene vary widely according to the percentage of crystalline isotactic polymer and the degree of polymerization. Polypropylenes with a 99% isotactic index are currently produced. 

Figure 1. Variation of the percentage of crystallinity of zeolites ZSM-48 and EU-1 as a function of the AI2O3 content in the following precursor gel phases ...

Figure 2. Variation of the percentage of crystallinity of zeolite ZSM-48 synthesized from 5Na20 xHMBr2 O.5AI2O3 60sic>2 3OOOH2O gels (200 °c, 66 h), as a function of HMBr2 content O- ZSM-48 + cristobalite.

Percentage of crystallinity for zeolites ZSM-48 and function of Na20 content in the gel. 

Figure 3. Variation of percentage of crystallinity of zeolite EU-1 synthesized from 10Na2O xHMBr2 1.5AI2O3 60SiO2 3OOOH2O gels...

Once again, it should be pointed out that the exact shape of the modulus-temperature curve of a crystalline polymer depends on the thermal history of the sample, particularly on the rate of cooling from the melt and annealing treatment. Two crystalline polymers are mechanically equivalent," for practical purposes, if they have the same values of Tg, Tm chain length, percentage of crystallinity, and crystalline structure. Because this is rarely the case, semicrystalline polymers exhibit a wide spectrum of properties. 

The density of crystalline polyethylene is 0.996 g/cm, while the density of amorphous polyethylene is 0.866 g/cm. Calculate the percentage of crystallinity in a sample of linear polyethylene of density 0.970 g/cm and in a sample of branched polyethylene of density 0.917. Why do the two samples have considerably different crystallinities 7 ... 

Figure 3. Variation with time of percentage of crystalline sulfur (Sa + Sp) expressed as a percentage of the total free sulfur in Thiokol/sulfur materials. 1 Thiokol LP-31. 2 Thiokol LP-32. 3 Thiokol LP-33.

A new approach for the synthesis of mesostructured zeolitic materials (namely UL-TS-1 and UL-ZSM-5) is reported. The materials were obtained in the solid state by heating TPAOH-impregnated mesoporous materials for several days. Various techniques including XRD, N2 adsorption, UV-visible, FTIR, TEM and Si MAS NMR were used to monitor the physicochemical properties of these materials as a function of crystallization time. The increase in the percentage of crystallinity is correlated with the corresponding variations in micropore and mesopore volumes, BET and BJH surface areas. The results indicate that the mesopore walls consist of zeolite nanocrystals. Depending on crystallization time, a range of materials from totally amorphous up to 80% crystalline is observed, while some of mesopores are preserved. 

Figure 13.22 Effect of crystallinity on the modulus-temperature curve. The numbers of the curves are rough approximations of the percentage of crystallinity. Modulus units = dynes/cm. (From Nielsen, L.E., Mechanical Properties of Polymers and Composites, Vol. 2, Marcel Dekker, New York, 1974. With permission.)...

Fig. 19.18. Plot of infrared splitting function vs X-ray diffraction percentage of crystallinity of a series of calcium phosphate. . VI O, VII . Vlll XIII A, 1 2 A, 3. (Termine and Posner, 1966.)...

The thermal parameters of the crystallization temperature T ), melting temperature (Tin), crystallization enthalpy (A/fc), heat of fusion (AiA), supercooling temperature (AT = T - Tc) and percentage of crystallinity (Zc) were obtained and reported in Table 8.1. 

---