Effects of particle type on thermal and mechanical properties of polyoxymethylene nanocomposites

Abstract

The effects of particle size of titanium dioxide (TiO 2 ) on mechanical, thermal, and morphological properties of pure polyoxymethylene (POM) and POM/TiO 2 nanocomposites were investigated and compared with the results for nanoparticle ZnO in the same matrix, reported in a previous paper. POM/TiO 2 nanocomposites with varying concentration of TiO 2 were prepared by the melt mixing technique in a twin screw extruder, the same method that used for blending the homogeneous ZnO nanocomposites. The dispersion of TiO 2 particles in POM nanocomposites was studied by scanning electron microscopy (SEM). The agglomeration, as observed by the mechanical properties of TiO 2 particles in the polymer matrix, increased with increasing TiO 2 content, a result not found for ZnO even at lower particle sizes. Increasing the filler content of POM/TD32.4 and POM/TD130 (130 nm) nanocomposites resulted in a decrease in tensile strength. The Young modulus, stress at break and impact strength of TiO 2 nanocomposite did not improve with increasing filler contents, in opposition to the better agglomeration conditions of ZnO nanocomposite even at lower particle sizes. Because of agglomeration, the POM/ TD32.4 nanocomposites had lower mechanical properties and lower degradation temperature than the POM/TD130 ones. The sizes of nanoparticles determined the agglomeration, but however, the agglomeration also depended on the type of nanoparticles, even when using the same matrix (POM) and the same mixing method. TiO 2 nanoparticles were more difficult to mix and were more agglomerated in the POM matrix as compared to ZnO nanoparticles, regardless of the size of the nanoparticles.

Investigation on morphology and properties of melt compounded polyoxymethylene/carbon nanotube composites

“…These observations from the DSC measurements indicate the fact that the carbon nanotubes act as nucleation sites in the composites to promote the crystallization behavior of polymer and thereby increase crystallization temperature and crystallinity. However, the increase is not pronounced, which is in good agreement with previous studies …”

“…Second heating regime was performed similar to the first heating and these measurements were used for determination of melting temperatures and crystallinities, respectively. The degree of crystallinity of the materials was determined by means of the ratio between the measured melting enthalpy and the enthalpy of a 100% crystalline POM that is taken as 326 J/g …”

“…The degree of crystallinity of the materials was determined by means of the ratio between the measured melting enthalpy and the enthalpy of a 100% crystalline POM that is taken as 326 J/g. 20…”

Structure and Morphology of Polyoxymethylene

“…Since weak intermolecular interactions exist between polymer chains, the a) data from ref. [66]; b) data from ref. [1]; c) data from ref.…”

Modification of polyoxymethylene for increased thermal resistance

“…Consequently, improved thermal resistance of POM is an important issue to broaden application possibilities of the polymer. Various approaches have been used to increase thermal stability of POM, i.e., modification with (1) organic compounds, containing active H atom, such as crosslinked melamine‐formaldehyde polycondensate, acting as formaldehyde absorbent by the addition reaction of the hydrogen on the amine groups of its molecules with formaldehyde produced by decomposition of POM , (2) low‐molecular organic compounds, for instance bisphenol‐A and amine to form in situ benzoxazines via the Mannich reaction, allowing control of formaldehyde generation , (3) high molecular compounds with higher thermal stability than POM itself, for instance acrylonitrile‐butadiene‐styrene copolymer, acting also as toughening agent , (4) noncombustible inorganic minerals like bentonite , montmorillonite clay , zinc oxide (ZnO) , titanium dioxide acting as impermeable heat resistant barriers. Although it is known that simultaneous use of various additives can synergistically influence properties of the composite materials, only few attempts have been made to investigate combined effects of previously proven organic and inorganic compounds to increase thermal stability of POM.…”