A study about silane modification and interfacial ultraviolet aging of hemp fiber reinforced polypropylene composites

摘要

Interfacial adhesion and the potential degradation are critical to service life and performances of plant fiber polymer composites. In this paper, the interfacial ultraviolet (UV) aging was studied by silane modification of hemp fiber on UV aging of the reinforced polypropylene (PP) composites. Three silane agents of 3-(Trimethoxysilyl)propyl methacrylate (MPS), N-[3-(Trimethoxysilyl)propyl]aniline (PAPS), and (3-Aminopropyl)-triethoxysilane (APS) were selected to obtain different interfacial adhesion. The composite degradation was characterized by surface observations, surface degradations, and tensile tests. The results show that functional group of silane agent has considerable effects on UV aging of the polymer composites. For APS, the composites have higher interfacial adhesion and exhibit slower surface whitening, cracking, degradation, and less mechanical properties deteriorations than others. After 8 weeks aging, its fracture stress and fracture strain decreased of 5.3% and 8.0%, respectively. Because aniline of PAPS is incompatible with PP matrix, the composites have a relative weak interfacial adhesion and shows faster surface whitening, cracking, and degradation. While aniline absorbs UV radiation strongly and may retard the interfacial degradation, thus its fracture stress hardly decreased after 8 weeks. However, ester group in MPS absorbs UV radiation and may get degraded leading to the decline of interfacial chain slips. Thus, fracture strains of the composites decrease greatest of 35.2%. It is concluded that interfacial adhesion and potential degradation are critical in UV aging. A "suitable" modifier improves not only initial mechanical properties but also the weathering resistance of plant fiber polymer composites.