Surface Studies of UV Irradiated Polypropylene Films Modified with Mineral Fillers Designed as Piezoelectric Materials

Abstract

Isotactic-polypropylene (i-PP) films with inorganic minerals such as Sillikolloid, perlite, or glass beads were prepared. The obtained polymeric films were subjected to an orientation process. Moreover, this paper includes results how the artificial accelerated weathering influences surface properties of the unoriented and oriented i-PP films with the mineral fillers. Changes in the ultraviolet (UV) treated polymeric films were studied with attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR), X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), and by measuring contact angles. The results revealed that photooxidation of i-PP was more effective in the presence of the fillers and depended on the type of the filler but not on its amount. Moreover, the oriented samples experienced more effective photooxidation compared with the unoriented ones. In all studied samples the same photoproducts were detected, suggesting the same route of polymer photooxidation with and without the filler. These polymeric films were produced for potential applications in the devices in which piezoelectric effect can be used.Polymers 2020, 12, 562 2 of 18 in their structures. This ordered charge arises from an unordered electric charge being in this material or implemented to the material during polarization. In the case of semi-crystalline polymers, the polar crystalline phase is oriented under a strong electric field at elevated temperature. The amorphous phase, also present in such polymers, maintains the polarization of molecular dipoles in the crystalline phase. Semi-crystalline poly(vinylidene fluoride) (PVDF) is the most known piezopolymer with its piezoelectric charge constant, d 33 about 20-28 pC/N [1-4]. The piezoelectric charge constant, d 33 , is the quantity which refers to the piezoelectric effect and is defined as the charged density generated upon applied stress. Generally, the higher d 33 value the better piezoelectric properties of a material [1,4].PVDF copolymers, polyamides, Parylene-C, liquid crystal polymers belong to the semi-crystalline polymers exhibiting piezoelectric properties [1,2].Amorphous polymers have to possess molecular dipoles in their structure. Heating the amorphous polymers above the glass transition temperature, T g , and applying a strong electric field orients the present molecular dipoles. Afterwards, lowering the temperature in the presence of the electric field makes the molecular dipoles frozen, and the material becomes polarized. The mobility of polymer chains is greater above T g and reduces below T g . The stiffness and brittleness are the characteristics of polymers below T g in a glassy state, while elasticity and softness are typical of polymers above T g in a rubbery state.Amorphous bulk polymers encompass polyimides and polyacrylonitrile [1,2]. Combination of piezoceramics and polymers results in the formation of polymer composites in which the piezoceramics particles are dispersed in the polymer matrix. The aim of such procedure is to obtain...

Corona Charging of Isotactic-Polypropylene Composites

“…The particle size was 6 μm—d97 and 15 μm—d50. The filler particles had the shape of round grains and lamellar aggregates [ 14 , 21 , 22 , 23 ].…”

“…The particle size was less than 20 μm—60%, 20–32 μm—23.8%, 32–40 μm—5.4%, 40–63 μm—9.9%, 63–100 μm—0.6%. The perlite particles looked like crushed bubbles [ 15 , 21 , 22 ].…”

“…Glass beads MinTron 7 ™ consisted of 48–60% of SiO 2 , 20–30% of Al 2 O 3 , 3–7% of Fe 2 O 3 , and 5–9% of alkali oxides The particle size was 20–30 μm—d90 and 5–9 μm—d50. The filler particles had regular spherical shapes [ 15 , 21 , 22 , 24 ].…”

“…A detailed description of the materials was included in previous works [ 14 , 15 , 21 , 22 , 23 , 24 ].…”

UV Polymerization of Methacrylates—Preparation and Properties of Novel Copolymers

“…Thus, it dissociates into radicals that initiate the polymerization of monomers with a defined structure [1,2]. Among the monomers, the most frequently used monomers are acrylate and methacrylate monomers, newly synthesized or commercially available [3][4][5][6][7][8][9][10].…”