Nucleating agents, analysis

Polypropylene molecules repeatedly fold upon themselves to form lamellae, the sizes of which ate a function of the crystallisa tion conditions. Higher degrees of order are obtained upon formation of crystalline aggregates, or spheruHtes. The presence of a central crystallisation nucleus from which the lamellae radiate is clearly evident in these stmctures. Observations using cross-polarized light illustrates the characteristic Maltese cross model (Fig. 2b). The optical and mechanical properties ate a function of the size and number of spheruHtes and can be modified by nucleating agents. Crystallinity can also be inferred from thermal analysis (28) and density measurements (29). 

In addition to requiring nucleating agents to promote crystallization, glass ceramics usually must be heat-treated at the critical nucleating, crystallization, and annealing temperatures to restructure the glass (Fig. 1). These temperatures can be conveniently determined, to a first approximation, by differential thermal analysis (DTA)i (Fig. 2). 

More recently, Kotek at al. studied the effects of untreated (denoted as Cl) and stearate-treated calcium carbonate particles (denoted as C2) of 1.3 p.m on the tensile properties of P-PP. Moreover, stearate-coated calcium carbonate particles of 0.075 p,m (denoted as C3) are also used (44). The p-nucleating agent employed is based on an amide of dicarboxylic acid. The critical concentration of p-nucleator needed to achieve 61% P-PP is 0.03 wt% on the basis of the XRD analysis. With further increase in the p-nucleator content to 0.1 wt% (supercritical), the p-PP content increases, but very slightly, to 65%. Furthermore, the K value also depends... 

The overall nucleation and crystalhzation rates of PLA tmder heterogeneous conditions are relatively higher than in homogenous conditions. The nucleation and crystallization rates of propylene-ethylene copolymer are increased tmder isothermal conditions. Addition of nucleating agent accelerates crystallization. Avrami equation is in popular use in the analysis of isothermal crystallization kinetics of polymers ... 

Starch acts as the nucleating agent for poly(e-caprolactone) ciystallization. According to the Avrami theory, starch functioned as a nucleating agent to improve the ciystallinity rate of PCL. However, the XRD analysis revealed that the ciystallinity decreased Because mobility constraints existed in the PCL chains with the increasing starch concentration, the ciystallization ability of PCL decreased ... 

This chapter contains analysis of applications of nucleating agents in various manufactured final products. The aim of this chapter is to suggest the most suitable nucleating agents for (Afferent products applications. 

Most nucleating agents belong to some of the safest additives used in the plastics industry. For this reason analysis of their health and safety will be short and pointed. 

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