Photodegradation of talc‐filled polypropylene

Abstract

Injection‐molded talc‐filled polypropylene (PP) composites have been exposed to ultraviolet (UV) radiation in the laboratory for periods up to 26 weeks. The extent of chemical degradation has been assessed by means of Fourier transform infrared spectroscopy (FTIR) and gel permeation chromatography (GPC), and the results correlated with the mechanical properties. In the early stages of exposure, the photo‐oxidation is faster in the talc‐filled composites than in the unfilled polymer, but this trend is reversed for exposures longer than ∼12 weeks. Scanning electron microscopy (SEM) inspection has revealed that surface cracks caused by photodegradation in the filled PP occur in the surface exposed to the UV source only, resulting in much less deterioration in tensile properties when compared with the unfilled polymer which degrades significantly at the unexposed surface also. Measurements of melting temperatures by differential scanning calorimetry (DSC) gave a consistent picture of degradation with that obtained by FTIR and GPC studies. DSC analyses have also shown that an increase in the melting enthalpy for both the unfilled and filled grades occurs during exposure.

Estudo do efeito do tipo de polipropileno na fotodegradação da blenda polipropileno/poliestireno de alto impacto

“…Partindo dessas afirmações, fica claro que o conhecimento da deterioração causada pelo meio ambiente nas propriedades do material é um aspecto fundamental para que se possa projetar componentes adequados para as aplicações específicas. A necessidade de se prever a vida útil de produtos quando expostos à radiação UV tem incentivado muitos estudos de envelhecimento acelerado em laboratório [2][3][4][5][6] . Apesar dos mecanismos de fotodegradação da maioria dos polímeros serem bem estabelecidos, o comportamento das blendas poliméricas frente à radiação UV ainda é um campo a ser explorado.…”

Effect of Nano-CaCO3 and Talc on Property and Weathering Performance of PP Composites

“…The incorporation of talc into composites resulted in a higher tensile strength than the composites containing NCC only. This is because the plate-like talc particles acted as the main reinforcing filler, which makes it more difficult to debond the PP matrix during the tensile test [16,18]. The tensile strength of NCC-talc hybrid filled composites also tended to decrease as the NCC contents increased.…”

“…Namely, the addition of NCC decreased impact strength values. Thus, we believe that the incorporation of NCC together with talc into PP matrix makes NCC dispersion more difficult compared with NCC only [10,16]. After 250, 500, and 1,000 h of accelerated weathering tests, impact strength values of the whole composites seemed to decrease; this decrease was especially pronounced for pure PP.…”

Fotodegradação do polipropileno: Um processo essencialmente heterogêneo

“…De acordo com o perfil de degradação mostrado na Figura 12, em compósitos de PP os efeitos do envelhecimento ocorreram apenas na superfície exposta, enquanto no PP puro ambas as superfícies foram degradadas. A degradação apenas na face exposta de compósitos de PP com talco foi observada também por microscopia eletrônica 42,43 . Como o material não degradado é o maior responsável em manter a integridade mecânica do produto, o desempenho de compósitos de PP foi superior ao do polímero puro.…”