Influence of thermooxidative aging on the static and dynamic mechanical properties of long‐glass‐fiber‐reinforced polyamide 6 composites

Abstract

The static and dynamic mechanical properties, thermal behaviors, and morphology of pure long-glass-fiber-reinforced samples [polyamide 6 (PA6)/long glass fiber (LGF)] with different thermal exposure times at 160 C were studied by comparison with stabilized samples in this study. The aging mechanism of the PA6/LGF samples under heat and oxygen was studied with the methods of thermal Fourier transform infrared (FTIR), differential scanning calorimetry, dynamic mechanical analysis, scanning electron microscopy (SEM), and so on. The results indicate that the static mechanical strength, melting temperature, and crystallization temperature decreased because of the decomposition of the macromolecular chain of PA6 resin and the debonding of the interface between the glass fibers and matrix. The glass-transition temperature and crystallinity also increased and decreased, respectively, after aging. The macromolecular chain decomposition dominated in the subsequent aging process; this resulted in many sharp and brittle microcracks appearing on the surfaces of the aged samples, as shown by SEM and the FTIR spectra. The existence of stabilizers endowed the PA6/LGF composites with better retention of static and dynamic mechanical properties. The reason was that the metal ions of the copper salt antioxidant acted as an anti-aging catalyst in the reinforced PA6 system. V C 2013 Wiley Periodicals, Inc. J. Appl.Polym. Sci. 2014, 131, 39594.

Influence of Thermo-Oxidative Ageing on the Thermal and Dynamical Mechanical Properties of Long Glass Fibre-Reinforced Poly(Butylene Terephthalate) Composites Filled with DOPO

“…Then, the decrease in E g ’ and tan δ max are due to the molecular degradation over the whole period of ageing. The peak intensity (tan δ max ) at T g is considered to reflect the extent of the mobility of the macromolecular chain segments [25]. The lower value of tan δ max implies that the mobility of molecular and damping properties are reduced after thermo-oxidative ageing.…”

“…The damping effects are relatively weak below T g . The widespread transition around T g can be due to the short hard-segment units and could have also been related to an interface of the polymer weakly adsorbed on the surfaces of the filler of the glass fibre [25]. Obviously, even though both thermal embrittlement and oxidative embrittlement would make the chain relaxation much more difficult, because of the cross-linking of the molecule chains, the aggregation of weakness assembles in the amorphous regions to make the chain relaxation much more difficult.…”

Thermal‐oxidative aging effects on the properties of long glass fiber reinforced polyamide 10T composites

“…Crystallinity of the specimen is characterized from equation χ=Δ H m /Δ H 0 , where χ is crytallinity, Δ H m is the melting enthalpy and Δ H 0 is the balanced melting enthalpy for 100% crystallographic PA10T . Δ H 0 is a fixed value once computed, thus the larger the Δ H m value is observed, the higher the crytallinity of composites will be.…”

“…In the past years, a lot of studies used brittle strength and segmental motion of materials, as an indication of aging. Zuo et al studied the static and dynamic mechanical properties of long‐glass‐fiber reinforced PA6 composite which was exposed at 160°C for a long time. The found that the T g of the composites shifted to higher temperature with the increasing aging time.…”

Comparison in composite performance after thermooxidative aging of injection molded polyamide 6 with glass fiber, talc, and a sustainable biocarbon filler

“…In the end, the outcomes are the same: a loss of thermomechanical properties and increase in end‐group concentrations that results in a decrease in the degree of crystallinity and alterations to the exposed surface morphology (micro‐cracks, discolouration) . For a few decades, PA 6‐based composites, for example, glass fiber (GF) or clay‐filled composites have been the topic of many studies considering their high commercial interest, specifically for automotive applications . Zuo et al .…”