Mohammad Dalour Hossen Beg

Polyurethane types, synthesis and applications – a review

Polyurethanes (PUs) are a class of versatile materials with great potential for use in different applications, especially based on their structure–property relationships. Their specific mechanical, physical, biological, and chemical properties are attracting significant research attention to tailoring PUs for use in different applications. Enhancement of the properties and performance of PU-based materials may be achieved through changes to the production process or the raw materials used in their fabrication or via the use of advanced characterization techniques. Clearly, modification of the raw materials and production process through proper methods can produce PUs that are suitable for varied specific applications. The present study aims to shed light on the chemistry, types, and synthesis of different kinds of PUs. Some of the important research studies relating to PUs, including their synthesis method, characterization techniques, and research findings, are comprehensively discussed. Herein, recent advances in new types of PUs and their synthesis for various applications are also presented. Furthermore, information is provided on the environmental friendliness of the PUs, with a specific emphasis on their recyclability and recoverability.

Oil palm bio-fiber-reinforced polypropylene composites: effects of alkali fiber treatment and coupling agents

The major challenge for natural fiber composites is their inherent poor adhesion between fiber and the matrix, high moisture absorption, and UV degradation. Lignin and hemicelluloses are the major composites of natural fiber which are responsible for UV degradation and moisture absorption, respectively. In this study, the lignocelluloses (oil palm empty fruit bunch) were treated with alkaline peroxide to separate lignin and hemicelluloses. Composites were produced with treated and untreated fibers using up to 45% fiber with polypropylene matrix using twin-screw extruder followed by injection molding. To improve the interfacial bonding, maleic anhydride grafted polypropylene (MAPP) was used as a coupling agent in the formulation. Properties of composites were evaluated using tensile testing, flexural testing, impact testing, SEM, and FTIR. The tensile, flexural, and impact properties were found to be improved with alkaline peroxide-treated fiber composites compared to untreated fiber composites. Addition of coupling agent (MAPP) also found to provide improved properties of composites.

Oil palm fiber reinforced polypropylene composites: effects of fiber loading and coupling agents on mechanical, thermal, and interfacial properties:

This study investigates the effects of fiber type, fiber loading, and coupling agent on the performance of oil palm biomass (OPB) fiber composites. Fiber composition and fiber morphology were evaluated by scanning electron microscope (SEM) and Energy-dispersive X-ray spectroscopy (EDAX). Grinded fiber was compounded into polypropylene by means of a twin-screw compounder. Maleated polypropylene (MAPP) was used as a coupling agent during compounding. The incorporated fiber contents for OPB composites were up to 40% (by weight). The compounded samples were prepared into test specimens by injection moulder. The composites were characterized by tensile testing, flexural testing, impact testing, melt flow index, SEM, thermogravimetric analysis (TGA), and differential scanning calorimeter (DSC). The most significant effect on strength and modulus were found by the addition of coupling agent. This was attributed to the thermodynamic segregation of the MAPP toward the interface, resulting in the formation of covalent bonding to the –OH groups of the fiber surface. Composites with MAPP also provided better thermal stability.

Laccase application in medium density fibreboard to prepare a bio-composite

Laccase efficacy as a biological tool for the removal of lignin in pulp industries is evident and has scope for a wider application. In this research study, rubber wood (Hevea brasiliensis) fibres were treated with laccase enzyme to study its effect on the fibre surface and the enzyme hydrolysis lignin (EHL) was collected as a byproduct. Collected EHL was concentrated (con) until the solution reached a 3% solid content. Fibre surface modification was studied by FESEM, FTIR and XRD. A distinct fibre surface with an improved crystallinity index was observed. EHL and Con-EHL were analyzed on a viscometer, FTIR, DSC, and TGA. Con-EHL exhibits a lower stretching energy at the benzene range compared to EHL and a curing pattern similar to UF was reported. To evaluate the capability of modified fibre and Con-EHL, 6 mm medium density fibreboard (MDF) of 810 kg m−3 were prepared by using 10% Con-EHL solution (by weight of fibre). The MDF boards exhibit higher mechanical strength and have passed the ASTM D1037 standard for internal bonding and modulus of rupture.

Characterization of alkali-treated kenaf fibre-reinforced recycled polypropylene composites

In this study, composites were produced using alkali-treated kenaf fibre and recycled polypropylene to improve the interfacial bonding between them. Maleic anhydride grafted polypropylene was used at a ratio of 1:10 to the fibre as a coupling agent. Blends are mixed together by means of a twin screw extruder and test specimens for mechanical testing were prepared through injection moulding machine. Fibre density, tensile property, elemental analysis, structural and morphological changes due to treatment was observed and their effects on the properties of the formulated composites were analyzed. Characterization of the composites was done by the tensile, flexural, impact and melt flow index tests. Thermogravimetric analysis and differential scanning calorimetry analysis were carried out to evaluate the thermal properties of the composites. Experiment showed that best tensile strength (TS) was found at 40% loading of fibre and alkali treatment of fibre enhanced the TS by 57%. Activation energies were calculated through Broido’s equation. It was also found that recycled polypropylene degrades at one stage, while composites degrade at two stages. Incorporating fibres decrease the activation energies of the composites but both coupling agent and treatment of fibres in that case enhance activation energies by 11 kJ mol−1 and 29 kJ mol−1, respectively, in the second stage. Field emission scanning electron microscope of the fractured surface showed that treatment of fibre improves the interfacial bonding between fibres and matrix. Density and water uptake of the composites were also studied in this study.

Effects of different coupling agents on the mechanical and interfacial properties of oil palm fiber reinforced polypropylene composites

This study investigates the effects of fiber loading and coupling agent on the performance of EFB fiber composites of oil palm biomass. The dried EFBs were ground in random sizes for composite production. Fiber composition and fiber morphology were evaluated by SEM and EDAX. Ground fiber was compounded with PP by means of a twin-screw compounder for the preparation of EFB/PP composites. Two types of MAPP were used as a coupling agent during compounding. The incorporated fiber contents for EFB composites were 10—40% (by weight). The test specimens were prepared by injection molding. The composites were characterized by melt flow index and mechanical testing such as TS, TM, FS, FM, and IS. Surface morphology was studied by SEM.

Thermo-mechanical and morphological properties of short natural fiber reinforced poly (lactic acid) biocomposite: Effect of fiber treatment

Untreated oil palm empty fruit bunch (REFB), alkali treated EFB (AEFB), ultrasound treated EFB (UEFB) and simultaneous ultrasound-alkali treated EFB (UAEFB) short fibers were incorporated in poly(lactic acid) (PLA) for fabricating bio-composites. The REFB fiber-PLA (REPC) and treated EFB (TEFB) fiber-PLA (TEPC) composites were prepared and characterized. Glass transition temperature, crystal melting temperature, decomposition temperature, melt flow index, density and mechanical properties (tensile strength, tensile modulus and impact strength) of TEPC are found to be higher than those of REPC. The observed crystallization temperature of TEPC is lower than that of REPC. Among all samples, TEPC prepared from UAEFB fiber shows better performances than other samples fabricated by REFB and AEFB fibers. Scanning electron microscopy, Fourier transform infrared spectroscopy and XRD analyses well support all the observed results.

Preparation and Characterization of Poly(lactic acid)-Based Composites Reinforced with Poly Dimethyl Siloxane/Ultrasound-Treated Oil Palm Empty Fruit Bunch

Oil palm empty fruit bunch fiber and polylactic acid were used to produce composites by melting cast method. Fiber loading was considered up to 40 wt%. Oil palm empty fruit bunch fibers were treated using ultrasound and polydimethylsiloxane to improve the interfacial adhesion. The structure and surface properties of the fibers were analyzed by Fourier transform infrared spectroscopy, X-ray diffraction, scanning electron microscopy, and contact angle measurement. Moreover, Fourier transform infrared spectroscopy, tensile, flexural, X-ray diffraction, contact angle, differential scanning calorimetry, and thermogravimetric analysis were used to investigate composites’ properties. The analysis revealed that polydimethylsiloxane treatment composites show reduced wettability with increased crystallinity. GRAPHICAL ABSTRACT

Mechanical and degradation characteristics of natural silk and synthetic phosphate glass fiber reinforced polypropylene composites

Degradable phosphate glass fiber is a synthetic fiber and silk is one of the strongest natural fibers. In this study, composites are fabricated from PP reinforced with phosphate glass fiber and silk fiber using compression molding. Tensile testing, flexural testing and impact testing are carried out to evaluate the composites mechanical properties. It has been found that silk fiber composites provided higher tensile strength (46 MPa), bending strength (50 MPa), and impact strength (17 kJ/m2) compared to glass fiber composites which are respectively 39 MPa, 46 MPa, and 8 kJ/m2. Degradation studies are carried out by accelerated weathering as well as by natural weathering. After weathering, the mechanical properties are evaluated and it has been found that phosphate glass fiber/PP composites degrade more rapidly compared to silk/PP composites.

Effect of matrix modification by natural rubber on the performance of silk-reinforced polypropylene composites

Silk fiber-reinforced polypropylene (PP) matrix composites were prepared by compression molding. Tensile strength, tensile modulus, bending strength, bending modulus, impact strength (IS), and hardness of the prepared composite (20 wt%) were found to be 54.7 MPa, 1826.2 MPa, 58.3 MPa, 3750.7 MPa, 17.6 kJ/m2, and 95, respectively. To improve the biodegradable character of the composite, natural rubber (NR) was blended (10, 25, and 50 wt%) with PP using extruder, and thin films were prepared by heat press for composite fabrication. Silk fiber-reinforced blended PP plus NRbased composites (20 wt% fiber) were fabricated and characterized. It was found that the mechanical properties of the composites decreased with the increase of NR in PP but IS improved significantly. The IS improved by 48% when 25% NR was incorporated in PP for the silk-based composites. The water uptake property of the composites was investigated. Degradation of all the composites was studied using simulating weathering, thermal degradation, and soil degradation tests. The study makes it clear that mechanical properties of silk/PP composites are greater than those of silk/PP plus NR composites. But silk/PP plus NR composites are more degradable than silk/PP composites, that is, silk/PP composites retain their strength for a longer period than silk/PP plus NR composites.