Crystallinity nucleating agents

The crystalline nucleating agent for polyolefin resin composition for bottle production comprises l,3 2,4-bis(3, 4 -dimethylbenzylidene) sorbitol and a phosphoric acid ester metal salt compoimd. ... 

Bulk devitrification tends to originate at small inclusions and particulates (e.g., insoluble crystalline nucleating agents) inside the glass. Whereas interfacial and surface devitrification are typically difficult to control, bulk devitrification can be... 

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 the PP-PA system, the DSC thermograms showed two peaks corresponding to nylon and PP. For the compatibilized system the crystallization peak of nylon remains unaltered, while that of PP shifted toward a higher temperature in the case of PPacr, and for PPmal, the shift was to lower temperatures (Fig. 1). This may be due to the fact that PPacr was acting as the nucleating agent. The average crystallinity of the blend was also decreased by the incorporation of compatibilizer. The mechanical properties of these blends was improved by the addition of PPmal and PPacr as compatibilizers (Table 1). 

Nucleating agents are used to improve the clarity of crystalline polymers such as polypropylene. Species such as diparamethyl-dibenzylidene sorbitol are... 

Many industrial semi-crystalline polymer materials like polypropylene, polyamides, or polyesters contain nucleating agents or clarifiers which form needle-shaped aggregates already in the polymer melt. "For this purpose the pattern is desmeared using the measured primary beam. For a less involved treatment it may be sufficient to know the integral width of the primary beam profile in fiber direction. 

A number of organic pigments can cause warping of certain thick-walled, large-area, non-axially symmetrical injection-molded parts such as bottle crates, where they act as nucleating agents for partially crystalline polymers. 

A number of organic pigments cause distortion in certain types of polyolefins, especially in HDPE. Pigments act as nucleating agents in such partially crystalline plastics i.e., they promote crystallization, which creates stress within the plastic product (Sec. 1.6.4.3). These pigments also enhance the shrinkage of polyolefins, particularly in the direction of the flow. 

Microstructure-property correlations in dynamically vulcanized thermoplastic elastomers based on polypropylene (PP)/EPDM have shown that clay was nearly exfoliated and randomly distributed into the continuous polypropylene phase [23]. SEM photomicrographs revealed that the size of rubber particles increased with clay incorporation. Also, the clay layers act as nucleating agents, resulting in higher crystallization temperature and reduced degree of crystallinity. 

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