To improve the interfacial compatibility between bamboo powder and polypropylene (PP), the effects of maleic anhydride-grafted polypropylene (MAPP) on the physico-mechanical properties and rheological behavior of 33 wt% bamboo powder/PP foamed composites were investigated. The results showed that the mechanical properties, water resistance, and surface wettability of MAPP-treated composites improved significantly, and the optimum content of MAPP was 9%. The density of 9% MAPP-treated composite was 0.845 g/cm 3 and its specific bending and tensile and notched impact strengths increased by 22.9%, 29.6%, and 49.0%, respectively, and the water absorption decreased from 8.80% to 1.92%, compared to the untreated composite. The frequency sweep results indicated that both the modulus and complex viscosity of the 9% MAPP-treated composite reached minimum values, and the slope of the lgG'-lgf curve for the treated composite increased by 15.9% compared with that of the untreated analogue. ESEM results indicated that the MAPP-treated composite had better bamboo powder dispersion and better interfacial compatibility. FTIR and XPS analyses confirmed the esterification between anhydride groups of MAPP and hydroxyl groups of bamboo powder. XRD studies showed the degree of crystallinity for the MAPP-treated composite increased to 26.52%, compared to 21.05% for the untreated composite.

To make full use of bamboo resources in China and explore the foaming mechanism of bamboo powder-polypropylene (PP) foamed composites, a foamed composite of 54 wt% PP and 13 wt% HMSPP containing 33 wt% bamboo powder blends was prepared by injection moulding. Effects of chemical foaming agents (CFA) on the mechanical properties and rheological behavior of foamed composites were investigated. The mechanical measurements and ESEM test results indicated that the composite with 1% modified exothermic FA had smaller cell size and better cell distribution compared with endothermic FA. It also had better physico-mechanical properties, with a decrease of 14.2% in density and an increase of 16.8% to 40.2% in the specific tensile, bending, and notched impact strength compared with the non-foamed composite. The frequency sweep results indicated that all composites had a shearthinning behavior, and both the modulus and complex viscosity of composite with 1% exothermic FA decreased compared with those of the non-foamed composite. The shear rate scans revealed that the non-Newtonian fluid index increased with the increase of exothermic FA content. The viscous activation energy of the modified composite with 1% exothermic FA was 46.41KJ•mol -1 . This was an increase of 8.9% compared with that of the non-foamed analogue.

Color and physico-mechanical properties change from 10 months of natural outdoor weathering for injection molded bamboo flour (BF)/polypropylene (PP) foamed composites were investigated. The composite surface morphology, before and after exposure, was observed by using environmental scanning electron microscopy (ESEM). Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) were used to characterize the chemical structures. Natural weathering was shown to cause more discoloration and surface deterioration, while the physicomechanical properties, rheological behavior, and thermal stability were less negatively affected for composites with higher BF amount ranging from 0 to 35 wt%. The rheological behavior results indicated decreases in the storage and loss moduli and the complex viscosity of weathered composites. Crossover frequency was found to increase and the average molecular weight decreased. The initial thermal decomposition temperature declined in foamed PP by 25 C and in 35% BF/PP foamed composite by 6 C, indicating a slight decline in thermal stability, as shown by thermogravimetric (TG) analysis. Photodegradation, photooxidation, and matrices chain scission in the composites were confirmed by FTIR and XPS analyses.

No abstract

The effect of outdoor natural weathering on the properties of injection molded 33 wt% bamboo powder (BP)=polypropylene (PP) foamed composites with and without the antioxidant and hindered amine light stabilizers (HALS) were investigated. The composites containing the antiaging agents had higher color stability, slightly greater retentions of flexural modulus, tensile and notched impact strengths, higher creep resistance, and better rheological stability than the reference composite. The antiaging agents of pentaerythritol tetrakis(3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate) and poly-(n-hydroxyethyl-2,2,6,6-tetramethyl-4-hydroxy-piperidyl succinate) had more beneficial effect than n-octadecyl-b-(4-hydroxy-3,5-ditert-butyl-phenyl)-propionate and bis(2,2,6,6-tetramethyl-4-piperidinyl)sebacate. After 12 months of exposure, ᭝E* decreased from 22.8 of the reference composite to 9.9 of the composite with the antiaging agents. Rheological behavior results indicated that the storage modulus, complex viscosity, and non-Newtonian fluid index of composites containing the antiaging agents were slightly increased. Natural weathering caused less decreases in the storage and loss moduli, crossover modulus, relaxation time, and average molecular weight for composites containing the antiaging agents than those for the reference composite. Environmental scanning electron microscopy (ESEM) observation confirmed the improved surface durability for composites containing the antiaging agents.