Nucleation additives

Most expandable polystyrene processes involve aqueous suspension systems in which pentane fractions of petroleum are introduced before, during, or after polymerization of styrene. Water-free systems may also be used. Particle size is controlled by suspension polymerization or by chopping fine filaments. The quenched pellet process for expandable polystyrene can consume off-size particles and is a convenient way to add colorants and cell-nucleating additives. 

Fillon et al. [12] proposed an efficiency factor for the evaluation of nucleating additives for polymers ... 

Tc-value of the system with the nucleating additive i.e. 125°C for the PP system with 1.05 %wt. talc and carbon black (Table 1.4), Tc-value of the reference system i.e. 110°C for the system in Table 1.4,... 

Fillon et al. [12] report a NE-value of 32% for PP with 1 %wt. of talc as nucleating additive. The difference between both NE values is not too bad considering the Tc2,max approximation, the differences in the used experimental methods and the different PP systems investigated. 

Large segment of the book discusses use and selection of nucleating agents for different processing methods, different polymers and specific products. These sections contain practical know-how on use of nucleating additives in different enviromnents. 

Good solubility and diffusion of the nucleating agent in PVDF was noticed because the crystalhzation of the additive and the crystallization of PVDF on the additive surface was shifted to the right at short times.These observations show that the most effective nucleating additives will dissolve at low concentrations, dissolve completely at the polymer processing temperature, which takes care of their good dispersion in the polymer, and crystallize above crystalhzation temperature of polymer. 

Efficiency of nucleating additive ean also be measured by the size of spherulite, since it is added to decrease the spheralite size. " The other usefiil method eonsists of addition of small amount of nucleating agent (0.02 wt%) and observing its effect on increase of crystallization temperature. Nucleation efficiency was also estimated using the following equation ... 

High denier polypropylene yams can be produced with certain nucleating additives that permit requisite degrees of shape and length retention, and thus acceptable resilience... 

Processing of many polymers benefits from the use of nucleating additives. Below we will report on the most common solutions for nucleation of individual polymers. 

Nucleating additives, such as, amotphous nano-silicon dioxide, nano-talc, alkali and alkaline earth salts of aromatic caiboxylic acids (e.g., sodium benzoates, salicylates), salts of ahphatic acids (e.g., sodium acetate), and nano particles of clay impart clarity and transparency to PET. ... 

Concentrates (also known as masterbatches) of bicyclic dicaiboxylate salt (e.g., disodium bicyclo[2.2.1]heptane-2,3-dicarboxylate, commercial product known as HPN-68) are nucleating additives used to facilitate typical thermoplastic manufacturing processes. " They impart high peak crystallization temperatures. They are suitable for use in small and large appliances. ... 

Some nucleating additives may agglomerate under the influence of moisture. ... 

The solubihty of additive also affects haze. At higher concentrations, part of nucleating additive may be imdissolved and this rrray cause the increase in haze value. ... 

HDPE immiscibly blends with hutyl ruhher [14] to provide improved chemical resistance, compression set and high-temperatnre mechanical properties versus nnvnlcanised hlends. LDPE and HDPE blend immiscibly with ethylene copolymers to improve environmental stress crack resistance, tonghness, filler acceptance, film tear resistance, improved flexibility and so on. In polyolefin, polybntene-1 forms miscible blends with PP [15,16]. The addition of PP to polybutene-1 increases the crystallisation rate of polyhntene-1 and would have utility as a nucleation additive. 

Several additional compounds may be added to the basic components to improve fire protection in intumescent coating formulations. For example, vitrifying agents can increase the thermal resistance of the intumescent char, whereas nucleating additives can help to control cell size in the char [1,2]. 

The recommended heat treatment for Ti-17 depends on process history. For a-P processed material, the heat treatment consists of a double solution treatment followed by aging. The first solution treatment should be done at 815 to 860 °C (1500 to 1575 °F) for 4 h, followed by rapid air cooling. The higher temperature (855 C, or 1575 °F) produces higher toughness as a result of an increased amount of acicular or, which precipitates both during cooling and subsequent heat treatment.The second solution treatment is done at 800 °C (1475 °F) and nucleates additional acicular a and pro-... 

C. Marco, M.A. G6mez, G. Ellis, and J.M. Arribas, Highly efficient nucleating additive for isotactic polypropylene studied by differential scanning calorimetry. Journal of Applied Polymer Science, 84(9) 1669-1679, March 2002. 

Polyisobutylene has been added to HDPE and LDPE to improve toughness, tear resistance and environmental stress rupture resistance. Commercial systems include Allied Chemical s ET polymers and BASF s Lupolen . Polypropylene/poly(butene-l) blends have been shown to exhibit miscibility and utility in films has been noted with some commercial activity [43, 44].Increased crystallization rate of poly( 1 -butene) with PP addition offers a blend approach as a nucleation additive [45]. Poly(l-butene)/LDPE blends have been employed as peelable films in packaging applications [46]. 

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