A-crystal nucleating agent

Barium bromide is very soluble in methanol, yet almost insoluble in ethanol. Repotted uses of barium bromide include fabrication of phosphors, for example from Bap2, BaBi2 2H O and EuBy (6) as a crystallization nucleating agent to control supercooling of CaBi2 solutions (7) and in the production... 

PLA based compositions with a plasticizer and a crystal nucleating agent have been reported (18). Plasticizers are collected in Table 3.2. 

The crystallization behavior of PLA was also studied in the presence of a crystal nucleating agent, ethylene-bishydroxystearamide (EBH) by Tang et al. 

A crystal nucleating agent that is suitable for promoting the crystallization of polyester, particularly phenylphosphorric acid metal salts can be produced in errviromnentally friendly process."... 

PCL was also blended with poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) copolymers on a small two-roll mill for 5 min at 140 °C (12% HV) or 128 °C (20% HV). The blends were injection moulded to produce tensile test samples. Samples were prepared in the presence of 1 wt % hydroxyapatite as a crystal nucleating agent and to reduce sample preparation time. For both copolymers, the addition of PCL (10 wt %) reduced the initial modulus and tensile strength (Table 12). Samples containing 90 wt % of PCL exhibited properties very similar to those of PCL and the effects were attributed to phase separation from the blends brought about by PHBV crystallisation at temperatures exceeding T for PCL. That is, the samples show immiscibility. Even blends containing 10 wt % PCL samples aimealed in aqueous media or in an oven showed the presence of crystalline PCL. 

In conclusion, the polymer interface can induce some limited number of nucleation events, but does not cause transcrystallinity, as some other crystal surfaces do. Consequently, the amorphous droplet surfaces, either in the solid or molten state, only act as a weak nucleating agent [Bartezak et al., 1987]. 

Wanamaker, C.L., Tolman, W.B. and Htilmyer, M.A. (2009) 2-Biopolymers poly(D-lactide)-poly(menthide)-poly(D-lactide) triblock copolymers as crystal nucleating agents for poly(L-lactide). Macromolecular Symposia, 283-284,130-138. 

Kose and Kondo studied tbe size effects of cellulose nanofibres on the crystallization behaviour of PLA. They discovered that the smaller size of cellulose nanofibres on tbe nanoscale does not necessarily make a better nucleating agent for PLA. Table 9.1 summarizes the Avrami kinetic parameters for the isothermal crystallization of the PLA and PLA biocomposites with different types of nanocelluloses as compared to PLA composites with talc and nanoclay. With the addition of unmodified and silylated CNCs as nucleating agents, the t 2 value increases with increasing T similar to that of nanoclay and com starch, but opposite to that of talc. Comparing the... 

Hyperfom HPN 210 M is a new nucleating agent for injection molded high-density polyethylene apphcations. It improves mechanical performance to the levels approaching those of polypropylene impact copolymers. It increases stiffness by up to 50%, heat distortion temperature by 10-40°C, and productivity. It has ability to create lamellar crystal orientation of PE in the polymer flow direction reducing shrinkage. ... 

Isotactic polypropylene composites with tetra-needle-shaped zinc oxide whisker were prepared via melt blending in a twin-screw extruder. The whisker is a p-nucleating agent, which offers higher crystallization temperature, smaller sphemlites, and faster crystalhzation rate than can be obtained in neat iPP. The addition of whisker also increases heat deflection temperature and thermal degradation temperature of iPP composite. ... 

A polymeric implantable device from a PLLA/PDLA blend such as a stent with improved fracture toughness is disclosed. A stereocomplex nucleating agent (a combination of PLLA/PDLA) results in an increase in nucleation density and reduced crystal size, which increases fracture toughness of the formed device. ... 

In the DSC cooling of PP from the melt, crystallization occurs. The minimum of the exothermic peak defines the crystallization temperature. This temperature is an indication of how rapidly the PP crystallizes. The higher the temperature, the more rapid the crystallization. Nucleating agents added to PP increase the crystallization rate of PP, resulting in a higher crystallization temperature. PP crystallizes such that crystalline structures called spherulites are formed. Nucle-ation results in the formation of smaller spherulites than would otherwise have been formed. This, importantly, results in increased clarity and stiffness but also imparts some possibly undesirable features, such as warpage or brittleness. 

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