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In this work, high-density polyethylene (HDPE)-based nanocomposites having different concentrations of Sepiolite (1-10 wt %) and compatibilizer, that is, PE-graft-maleic anhydride (PE-g-MA) of varying molecular weight and maleic anhydride content were prepared by melt compounding. The influence of Sepiolite amount and compatibilizer polarity and molar mass on the crystallization behavior [differential scanning calorimeter (DSC) and X-ray diffraction (XRD)], rheological properties (oscillatory rheometer) and dimensional stability [dynamic mechanical analyzer (DMA) and heat deflection temperature (HDT)] of the nanocomposites was investigated. It was found that Sepiolite did not affect the crystallization behavior of HDPE. The rheological results show that the incorporation of Sepiolite into HDPE matrix up to 10 wt % increases the complex viscosity of polymer. Storage modulus and loss modulus both in oscillatory rheometry and in DMA were highest for nanocomposite prepared using 10 wt % Sepiolite owing to the improved mechanical restrain by the dispersed phase. In the presence of compatibilizer, the values of storage modulus and loss modulus were lower as compared to uncompatibilized nanocomposites at same loading of Sepiolite. The reduction in modulus is more pronounced in composites prepared using compatibilizer of lower molar mass as compared to those prepared using higher molar mass compatibilizer.

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Polypropylene composites were prepared using natural fibers such as pigeon pea stalk fibers and banana peel. Aerobic biodegradation studies in compost have been carried out as per ASTM with composites prepared where cellulose and polypropylene has been taken as positive and negative reference respectively. Various analytical tools like SEM, TGA, XRD, DSC and Color have been used to study the change after biodegradation in composites. Highest fiber loaded composites i.e. 40 wt% depicted highest biodegradation in comparison to 10 and 20 wt% loading of untreated fiber in polypropylene. In comparison to untreated fiber composites, maximum biodegradation was observed in treated fiber composites with same amount of the fiber loading.

Potato peel powder (POPL), which is biodegradable, has been used as filler material in polypropylene (PP) matrix in varying concentration from 10 to 40% by weight to prepare biocomposites and investigated water absorption, physicomechanical and thermal properties. Scanning electron microscopy and X-ray diffraction has been used for morphological characterization and crystallization studies. Flexural modulus of biocomposites increased by 40% compared with neat PP at 30% loading of POPL. Flexural strength also increased with increasing filler loading. Tensile strength of biocomposites has been observed to be comparable with neat PP up to 20% filler loading and increase in tensile modulus up to 40% was seen in biocomposites with 20% filler loading. Impact strength of biocomposites up to 20% filler loading was found to be at par with neat PP. Use of MA-g-PP compatibilizer in the biocomposites yielded better physico-mechanical and thermal properties than biocomposites without compatibilizer. V C 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 42445.

This study covers the micro- and macrostructural changes that take place prior to and after foaming in polypropylene (PP). Four industrial grades of PP with varying molecular weights and amorphous contents were considered. Batch foaming of the samples was carried out using supercritical CO2 at three different temperatures, keeping the saturation pressure constant. A straight correlation between the cell size and the density of foams was drawn. Differential scanning calorimetry measurements in coherence with wide-angle X-ray analysis gave unique insights into the crystallinity of foams. Furthermore, dynamic mechanical analysis (DMA) showed shifts in the transition peaks of foamed PPs as compared with their corresponding unfoamed states. The tensile properties of foams of impact copolymers, foamed at low temperature, possessed superior tensile toughness to that of the foams obtained from homopolymers and random copolymers. This tensile characteristic of foams was in coherence with the DMA analysis.

Cotton stalk as commercially viable bio fiber for preparing bio‐composites is explored of late, and the effects of various chemical treatments of cotton stalk fiber on mechanical, rheological and morphological properties of Polypropylene (PP)‐Cotton stalk (CS) bio‐composites are reported in this study. PP‐CS bio‐composites were prepared by varying the amount of cotton stalk from 10 to 50% by melt mixing in twin screw extruder and then injection molded to make specimen. PP‐CS bio‐composites with 50 wt% untreated CS were found to have maximum improvement in tensile modulus (83%), flexural modulus (120%), impact strength (39%). Similar to tensile and flexural modulus, the storage modulus of the PP‐CS composites was also increased with incorporation of CS into the PP matrix. To further increase the interaction between CS and PP matrix, four different chemical treatments (alkali, silane, permanganate solution and stearic acid) were tested for mechanical properties of CS‐PP bio‐composites. Among them KMnO4 treatment was found most effective on overall enhancement of bio‐composite properties. Chemically treated CS‐PP bio‐composites could be an economic viable option to prepare high quality low cost composites for suitable applications in various interior parts of automotives and house hold products. POLYM. COMPOS., 39:E286–E296, 2018. © 2017 Society of Plastics Engineers