Abstract
Nanocomposites of isotactic polypropylene with 1–5 wt.% of fibrillated PTFE (PP/T) were prepared, and their crystallization during cooling under elevated pressure, in a wide pressure range, up to 300 MPa, as well as the resulting structure, were examined. The crystallization peak temperatures of PP/T, especially with 3 and 5 wt.% of PTFE, exceeded by up to 13 °C those of neat PP. Moreover, a fine-grain structure was formed in PP/T in the entire pressure range, which proved the ability of the fibrillated PTFE to nucleate crystallization of PP in the γ-form under elevated pressure. This also resulted in a higher crystallinity level developed in the γ-domain, before the temperature range of the α-domain was reached during cooling. Hence, the γ-content increased in comparison to that in neat PP, under the pressure up to 200 MPa, especially under 50–100 MPa.
Highlights
All-polymer composites, including self-reinforced composites, are an interesting group of materials
Our study focused on nonisothermal crystallization of isotactic polypropylene (iPP) with fibrillated PTFE during cooling, in a broad pressure range, up to 300 MPa
Nonisothermal crystallization of the polypropylene with 1–5 wt.% of fibrillated PTFE (PP/T) during cooling in a broad pressure range, up to 300 MPa, and the structure formed during the crystallization, were studied
Summary
All-polymer composites, including self-reinforced composites, are an interesting group of materials The advantages of these materials include relatively low weight; easy recycling ability, e.g., reprocessing by remelting; and the possibility of tuning adhesion between the components [1,2]. Such composites can be obtained by filling polymers with ready-made fibers or by the formation of fibers in a matrix, in situ during processing [2]. Poly(tetrafluoroethylene) (PTFE) nanofibrils were formed during the shearing of PTFE powder particles with reduced entanglement density during compounding with melts of other polymers, including isotactic polypropylene (iPP), high density polyethylene (HDPE), low density polyethylene, poly(oxymethylene), and atactic polystyrene [3,4,5,7]. It is worth mentioning that PTFE particles strongly nucleated the crystallization of iPP [12]
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