Crystallization Behavior Of Materials Research Articles

Effect of silver particles on the crystal structure and the mechanical, optical and antibacterial properties of various polypropylene based plastomers and elastomers

In composite materials consisting of silver particles and a polypropylene matrix, the silver must migrate to the surface of the materials in order to exert on antibacterial effect. Substrates with various crystal structures may have different interactions with the silver particles, which can significantly impact the antibacterial performance. The research described in this paper investigates the influence of silver particles on the crystallization behavior of materials with varying crystallinity capabilities by selecting various polypropylene-based plastics and elastomers (Homopolymer polypropylene (PPH-T03), random poly(propylene/ethylene) copolymers (PPR-YPR503 and PPR-P340R), polyolefin elastomers (VERSIFY3000 (POE-1) and VERSIFY3401 (POE-2)), and ethylene propylene diene monomer for polymers (EPDM4725 and EPDM4770)). The research results indicated that the silver only entered the amorphous regions of the PP rather than entering the crystal regions, where they can more easily migrate to the material surface, resulting in a higher antibacterial effect. Therefore, the antibacterial degree of PP-Ag was as high as 99.9%. Silver can enter the micro-crystals of both the random copolymer polypropylene, (PPR-YPR503, PPR-1) and the random copolymer polypropylene, (PPR-P340R, PPR-2,) with a stronger effect on PPR-2. More silver entered the micro-crystals of PPR-2, and it was difficult for the silver ions to migrate out of the crystalline regions to exhibit antibacterial properties. The antibacterial degree of PPR-1-Ag was higher than that of PPR-2-Ag (77.8% vs. 66.7%). Similarly, silver had a greater impact on the lamellar structure of the polyolefin elastomer (VERSIFY3401, POE-2) compared to the polyolefin elastomer (VERSIFY3000, POE-1). In comparison with POE-2-Ag, POE-1-Ag exhibited a higher antibacterial degree (79.6% vs. 57.4%). Research on the two types of ethylene propylene diene monomer (EPDM) composite materials indicated that EPDM-1 exhibited a lower Mooney viscosity and poorer flowability. The EPDM-1 tended to encapsulate the silver within its molecular chains, thereby impeding the migration of silver to the surface. The optical performance analysis indicated that silver antibacterial agents had little impact on the optical properties of PP-Ag, PPR-1, PPR-2, POE-1, POE-2 and the EPDMs. We suggest that this research provides theoretical guidance for selecting highly antibacterial polypropylene materials.

Crystallization Behavior of Poly(ε-Caprolactone)-Hollow Glass Microspheres Composites for Rotational Molding Technology

Composites suitable for rotational molding technology based on poly(ε-caprolactone) (PCL) and filled with hollow glass microspheres (HGM) or functionalized hollow glass microspheres (HGMf) were prepared via melt-compounding. The functionalization of glass microspheres was carried out by a silanization treatment in order to improve the compatibility between the inorganic particles and the polymer matrix and achieve a good dispersion of glass microspheres in the matrix and an enhanced filler–polymer adhesion. The crystallization behavior of materials was studied by DSC under isothermal and non-isothermal conditions and the nucleating effect of the glass microspheres was proven. In particular, the presence of silanized glass microspheres promoted faster crystallization rates and higher nucleation activity, which are enhanced by 75% and 50%, respectively, comparing neat PCL and the composite filled with 20 wt% HGMf. The crystalline and supermolecular structure of PCL and composites crystallized from the melt was evaluated by WAXD and SAXS, highlighting differences in terms of crystallinity index and structural parameters as a function of the adopted crystallization conditions.