Melting peak temperature

The mixture of oligomers was heated in a flask to 200°C in a mineral bath (the DSC peak melting temperature of the oligomers was 230°C) while stirring and removing water formed with a vacuum pump to form high-molecular-weight nylon-6,6. 

Figure 19 (a) Peak melting temperature as a function of the branch content in ethylene-octene copolymers (labelled -O, and symbol —B (symbol, ) and -P (symbol, A) are for ethylene-butene and ethylene-propylene copolymers, respectively) and obtained from homogeneous metallocene catalysts show a linear profile, (b) Ziegler-Natta ethylene-octene copolymers do not show a linear relationship between peak melting point and branch content [125]. Reproduced from Kim and Phillips [125]. Reprinted with permission of John Wiley Sons, Inc. 

Figure 20 Linear dependence of peak melting temperature with branch content in terms of comonomer (left hexene right octene) content from the work of Mirabella and Crist [126]. Reproduced from Mirabella and Crist [126]. Copyright 2004, John Wiley Sons, Inc. Reprinted with permission of Wiley-Liss, Inc., a subsidiary of John Wiley Sons, Inc.

With MAO activation, Zr- and Hf-FI catalysts 1 and 3 exhibit fairly high reactivity toward propylene and produce propylene oligomers [64, 65], Conversely, the corresponding Ti-FI catalyst/MAO 2 forms semicrystalline PP (1 °C polymerization), which displays a peak melting temperature of 97 °C, indicative of the formation of a stereoregular polymer. To our surprise, microstructural analysis by 13C NMR indicates that the resultant polymer is syndiotactic (rr 19%), and that a chain-end control mechanism is responsible for the observed stereocontrol, regardless of the C2 symmetric catalyst ([28] for the first report on syndiospecific propylene... 

The melting behavior of the two resins also reveals structural differences. The physical blend has a peak melting temperature (TJ of 126 °C with a heat of fusion of 104 J g, consistent with the high density fraction of the sample. The diblock sample has similar crystallinity, with heat of fusion of 104 J g-1, reflecting the similar compositions of the two samples. However, the diblock sample displays a lower peak melting temperature, with 7 m = 122 °C. This depression of peak melting temperature is also consistent with OBC architecture. 

The heat capacity is the amount of energy required to increase the temperature of a unit mass of material. It is commonly measured using a differential scanning calorimeter (DSC). The heat capacity depends on the resin type, additives such as fillers and blowing agents, degree of crystallinity, and temperature. A temperature scan for the resin will reveal the Tg for amorphous resins and the peak melting temperature and heat of fusion for semicrystalline resins. The heat capacities for LDPE and PS resins are shown in Fig. 4.15. 

In the case of co-polymers with cyclic olefins other than NB, Naga et al. performed the co-polymerizations of ethylene or propylene with cyclopentene by using a number of bridged metallocene catalysts, and then investigated the peak melting temperatures and crystalline structures of the resultant co-polymers, all containing cyclopentane units. In 2004, Waymouth and Lavoie reported on the catalytic properties of a series of... 

Fig. 53. Eflect of heating rate on the peak melting temperature of sample 2 O, unrestrained , restrained...

Table 9.3 shows step one of the double fractionation of LLDPE carried out with propane at 130°C. The increasing pressure profile began at 250 bar (3,600 psia) and increased to 675 bar (9,800 psia) in increments of —25 bar. The parent LLDPE with a polydispersity of 5.0 has been separated into fractions with a molecular weight range from about 10,000 to 200,000 and polydispersi-ties of 1.2 to 1.6. There is only a weak dependence of enthalpy of fusion ( usion) peak melting temperature on molecular weight. The results are consistent with the notion that molecular weight is the dominant factor in liquid-gas equilibrium. The values, which reflect the crystallinity of... 

Composition (wt%) Dose (kGy) Peak melting temperature (°C) Enthalpy of melting (J/g) ... 

T, peak melting temperature T, peak crystallization temperature. [From Reference 48 with permission from Wiley Interscience.]... 

The DSC trace for UHMWPE shows two key features. The first feature of the DSC curve is the peak melting temperature (T ), which occurs at around 137°C and corresponds to the point at which the majority of the crystalline regions have melted. The melt temperature reflects the thickness of the crystals, as well as their perfection. Thicker and more perfect polyethylene crystals will tend to melt at a higher temperature than smaller crystals. 

Sample Name Peak Crystallization Temperature (T) °C AH. (1/g) Peak Melting Temperature AH (1/g) Percentage Crystallinity (%)... 

---