Muhammad Imran

Toughening of Polylactic Acid Nanocomposites: A Short Review

Polylactic acid (PLA) is a thermoplastic derived from renewable resources, which degrades to nontoxic compounds in landfills. With current advances in the field of nanotechnology, development of layered silicate-based PLA nanocomposites successfully created a sustainable material with enhanced physical, thermal and chemical properties, holding the future as an alternative to petroleum-based materials. However, the toughness of PLA in its pristine state and nanocomposites is often insufficient. As such, there has been tremendous effort in developing ways to improve this with incorporation of plasticizers and impact modifiers. In this review, we summarize approaches in toughening of PLA and its nanocomposites.

Functionalization Effects of Single- Walled Carbon Nanotubes as Templates for the Synthesis of Silica Nanorods and Study of Growing Mechanism of Silica

Silica nanorods were successfully prepared through a sol-gel process in the presence of carboxylic-functionalized single-walled carbon nanotubes (C-SWCNTs). The effect of chemical functionalization of single-walled carbon nanotubes (SWCNTs) on the growth of the silica layer was investigated using pristine SWCNTs (P-SWCNTs) and C-SWCNTS. The C-SWCNTs served as a unique template to fabricate silica hybrid composite materials. The crystalline formation and growing mechanism of the silica layer on C-SWCNTs were explained by the hydrolysis and chemical bonding between silica precursors and carboxylated SWCNTs. The C-SWCNTs, as templates, were successfully encapsulated using silica, and used templates were removed by oxidation at high temperature. Finally, silica nanorods/nanowires were synthesized in forms of mold, and this silica fabrication mechanism could be applied for large-scale production of silica nanomaterials and highly flexible nanocomposites. The sequence of a silica encapsulation process of C-SWCNTs and removed C-SWCNTs was characterized using SEM, TEM, EDX, FT-IR and Raman spectroscopy, XRD, and electrical analysis.

Recent Developments in the Chemical Recycling of PET

Poly(ethylene terephthalate), more commonly known as PET in the packaging industry and generally referred to as ‘polyester‘ in the textile industry, is an indispensable material with immense applications owing to its excellent physical and chemical properties. On the other hand, due to its increasing consumption and non-biodegradability, PET waste disposal has created serious environmental and economic concerns. Thus, management of PET waste has become an important social issue. In view of the increasing environmental awareness in the society, recycling remains the most viable option for the treatment of waste PET. Among the various methods of PET recycling (primary or ‘in-plant’, secondary or mechanical, tertiary or chemical, quaternary involving energy recovery), only chemical recycling conforms to the principles of sustainable development because it leads to the formation of the raw materials from which PET is originally made. Chemical recycling utilizes processes such as hydrolysis, methanolysis, glycloysis, ammonolysis and aminolysis. In a large collection of researches for the chemical recycling of PET, the primary objective is to increase the monomer yield while reducing the reaction time and/or carrying out the reaction under mild conditions. Continuous efforts of researchers have brought great improvements in the chemical recycling processes. This paper reviews methods for the chemical recycling of PET with special emphasis on glycolytic depolymerization with ethylene glycol. It covers the researches, including the works by the authors, on various processes and introduces recent developments to increase monomer yield. Processes including suband supercritical, catalytic, and microwave-assisted depolymerization are discussed. This paper also presents the impact of the new technologies such as nanotechnology on the future developments in the chemical recycling of PET.

Ethylene Copolymer Toughened Polylactic Acid Nanocomposites

Polylactic acid (PLA)/montmorillonite (MMT) nanocomposites toughened with Biostrong (an ethylene copolymer from DuPont) was developed. PLA, Biostrong and MMT were melt blended using twin-screw extruder followed by injection molding. Impact strength improved with 2 phr MMT in PLA/Biostrong. Flexural modulus of PLA/Biostrong nanocomposites increased while the strength decreased with MMT. PLA chains were intercalated in MMT. Presence of Biostrong and MMT improved the thermal stability and crystallinity (Xc) of PLA. The storage modulus (E) values of PLA at 25–50°C dropped with Biostrong while incorporation of MMT compensated the loss. The biodegradation rate and permeability of PLA/Biostrong nanocomposites decreased with MMT.

Epoxidized natural rubber toughened polyamide 6/organically modified montmorillonite nanocomposites

The organically modified montmorillonite (OMMT)-filled polyamide 6 (PA6) nanocomposites were toughened with epoxidized natural rubber (ENR). The PA6, ENR (15–30 wt%) and OMMT (4 parts per hundered (phr)) were melt compounded using counterrotating twin-screw extruder followed by the injection molding. X-ray diffraction (XRD) results indicated that the OMMT platelets in PA6/ENR/OMMT nanocomposites were well dispersed. The Fourier transform infrared (FT-IR) spectra showed graft esterification reaction between PA6 and ENR during processing. It was found that the addition of ENR (up to 20% wt) increased the impact strength and elongation at break of the nanocomposites. Scanning electron microscopy (SEM) images revealed well-dispersed ENR particles. Differential scanning calorimetry (DSC) results showed that the presence of ENR and OMMT had negligible effect on the glass transition of PA6 with a slight decrease in crystallization temperature and crystallinity in PA6/ENR/OMMT nanocomposites.

Epoxidized natural rubber–toughened polypropylene/organically modified montmorillonite nanocomposites

The objective of this study is to toughen organically modified montmorillonite (OMMT)-filled polypropylene (PP) nanocomposites with epoxidized natural rubber (ENR). PP, ENR (10–20 wt%), OMMT (6 wt%) and maleated PP (PP-g-MA; 10 wt%) were melt blended using counterrotating twin extruder, followed by injection molding to prepare test samples. X-ray diffraction results revealed that the OMMT platelets in PP/OMMT nanocomposites were intercalated and the incorporation of ENR into the nanocomposites further increased the d-spacing of OMMT layers. The Fourier transform infrared spectra showed that the maleic anhydride group in PP-g-MA reacted in situ with the epoxy groups of ENR, which demonstrates the occurrence of grafting reaction. With slight decrease in stiffness and strength, the addition of 20 wt% ENR increased the impact strength of PP/ENR/OMMT nanocomposites by 521% compared to PP/OMMT nanocomposites. Scanning electron microscopy images revealed that the ENR particle size increased with increasing ENR contents in PP/ENR/OMMT nanocomposites. Differential scanning calorimetry results revealed that the presence of ENR and OMMT had slightly increased the crystallization temperature as well as the degree of crystallinity of PP. Thermogravimetric analysis showed that the blending of ENR decreased the thermal stability of PP/OMMT nanocomposites.

Dual Sink Efficient Balanced Energy Technique for Underwater Acoustic Sensor Networks

Underwater Acoustic Sensor Networks are considered to provide efficient monitoring tasks in aquatic environment but due to limited battery resource of sensor nodes, network lifetime collapses. Energy balancing is the major issue in low network lifetime. High energy consumption creates energy holes and ultimately leads to shorter network lifetime. Therefore, energy consumption must be balanced to increase network life time. To overcome these concerns a technique should be designed that minimizes the energy consumption and prolong network lifetime. This paper presents a Dual Sink Efficient and Balanced Energy consumption Technique (DSEBET) for UASNs. DSEBET overcomes the problem of limited network lifetime and high energy consumption over long distance. Dual sinks underwater model is established. DSEBET first establishes links between nodes on the basis of their optimum distance value and then picks relay nodes on the basis of their minimum distance Nj value for the transmission of data. In the data transmission phase every nodes have equal energy levels numbers (ELNs). Long distance nodes from one sink will share their data to other sink if come in range of sink otherwise they will establish a multi hop path for transmission of data to the respective sink.

Recent Developments in PA6/PP Nanocomposites

An overview of the recent developments in PA6/PP blend nanocomposites is presented in this paper with an emphasis on their mechanical, thermal and morphological properties. The role of organoclay as a reinforcing agent and polyethylene octene (POE) as an elastomer are discussed in detail. The organoclay increases the strength and stiffness while the POE elastomer increases the impact toughness of the nanocomposites. The effects of various parameters such as PA6/PP blend ratio, organoclay loading and the concentration of elastomer on the nanocomposites properties are also examined. The exfoliated state of organoclay platelets along with the fine particle size and uniform dispersion of POE demonstrate the nanocomposite with improved properties. These materials are attracting considerable interest in polymer research community because they exhibit substantial improvement in properties at low filler contents.

Carcinoma breast, late presentation-a big concern

Objectives: To study the different presentation patterns and their treatment options in advanced carcinoma breast. Design: A retrospective observational study Settings: North Surgical Ward, Mayo Hospital, Lahore, from November 2004 to April 2006. Patients and Methods: In total, 156 patients with carcinoma breast, confirmed histopathologically by biopsy and /or FNAC, were included in this study. Information was gathered from them using a structured questionnaire. Results: The peak incidence of carcinoma breast was found to be between 31- 45 years of age. Majority of these patients presented in stage II (22%). Maximum number of patients presented in stage III (56%). However stage IV disease was also found in 12% of patients` population. But stage I disease was least commonly presented disease (10%). And infiltrative ductal carcinoma was the most prevalent (94%) histologic type. Modified radical mastectomy was the surgical treatment adopted in about 72% of cases with adjuvant or neoadjuvant chemotherapy. Conclusion: Advance stage breast lump with local or locoregional spread remained the commonest mode of presentation of carcinoma breast . And infiltrative ductal carcinoma is the commonest histologic variant. Majority of the of patients with carcinoma breast in Pakistan still present in advanced stages where almost no cosmetically more acceptable surgical procedure can be carried out.