Tiam Ting Tee

Review of Nanocellulose Polymer Composite Characteristics and Challenges

ABSTRACT The nanosize cellulose has emerged in the last two decades as an efficient strategy to improve the structural and functional properties of polymer composite. This review focuses to explore the unique mechanical–thermal properties of cellulose-based nanocomposites particularly on the various reinforcing mechanisms of nanocellulose. The promising reinforcing capabilities of nanocellulose mainly lie in their intrinsic chemical natures, aspect ratio, and degree of crystallinity. In this article, the potential factors deteriorating the aspect ratio and crystallinity have been systematically reviewed. Some relevant suggestions/solutions were also widely exploited toward tailoring the generating problems. GRAPHICAL ABSTRACT

Evaluation performance of multiple plasticizer systems on the physicomechanical, crystallinity and thermogravimetry of polyvinyl chloride

Abstract The flexibility of polyvinyl chloride (PVC) materials is crucial in the production of urine bags and urinary tubing. However, the combination and concentration of plasticizers offers a variation of the plasticizing efficiency to the PVC matrix. In this study, several types of plasticizers, namely dioctyl adipate (DOA), diisononyl phthalate (DINP), dioctyl terephthalate (DOTP) and epoxidized soybean oil (ESO) were added into the PVC matrix to enhance the flexibility of PVC compounds. Increasing the plasticizer loading level improved elongation at break of PVC compounds, whereas the tensile strength, hardness and specific gravity deteriorated. In addition, DOA added to PVC compounds exhibited the highest plasticizing effect with the highest elongation at break results at lower percentages of plasticizer (≤50%). This is due to the linear chain of the DOA plasticizer promoting the slippage effect of polymer chains during stretching and thus imparting a higher flexibility. In addition, a higher loading level of plasticizer in PVC compounds also produced a marginal increment on the crystallinity and thermal stability of PVC compounds. Overall, DINP/DOA added to PVC compounds exhibited the highest flexibility effect (elongation at break) at higher percentages, but lowered tensile strength and crystallinity.

Interactions of montmorillonite and electron beam irradiation in enhancing the properties of alumina trihydrate–added polyethylene and ethylene vinyl acetate blends

This study aims at investigating the effects of electron beam irradiation on the montmorillonite and alumina trihydrate–added low-density polyethylene and ethylene vinyl acetate blends. The mechanical, flammability and electrical resistivity of the montmorillonite and alumina trihydrate–added low-density polyethylene and ethylene vinyl acetate blends were investigated. The addition of montmorillonite provided the reinforcing effect to the alumina trihydrate–added low-density polyethylene and ethylene vinyl acetate, whereby the tensile strength of 150 kGy and 250 kGy irradiated samples gradually increased with increasing of montmorillonite composition (i.e. 5 phr to 20 phr). Furthermore, the addition of montmorillonite into low-density polyethylene and ethylene vinyl acetate blends increased the limiting oxygen index and thermal decomposition temperatures of samples, thus improving the flame retardancy and thermal stability. The increasing of montmorillonite and irradiation dosage promoted the char formation during combustion. Besides, the increasing of montmorillonite loading levels gradually decreased the surface and volume resistivities of the polymer blends. The high irradiation dosages (i.e. 150 kGy and 250 kGy) were found to slightly decrease the electrical resistivity of the alumina trihydrate–added low-density polyethylene and ethylene vinyl acetate blends especially at high loading of montmorillonite. The irradiation effect improved the mobility of montmorillonite ions in polymer matrix, subsequently causing the reduction of the electrical resistivity of the polymer blends. The storage capacity of electrical charges of samples was slightly declined with the increasing of montmorillonite loading levels and irradiation dosages as shown by the dielectric constant results. The dielectric loss tangent of samples slightly increased at the increasing of montmorillonite loading level. However, the dielectric loss tangent was declined with increasing of irradiation dosages.

Roles of Calcium, Zinc, Copper and Titanium Compounds on the Degradation of Polymers

In this article, the influences of the metallic filler content upon the thermal degradability of polymer composites such as initial degradation temperature, maximum degradation temperature and char content have been critically reviewed using thermogravimetric analysis. Besides that, the review on the relationship between activation energies of polymer/metal composites, which was obtained from various degrade models, and the content of metallic fillers have also been defined. Other thermal properties such as glass transition temperature (Tg) and melting temperature (Tm) have also been reviewed based on the evaluation of differential scanning calorimetry (DSC) analysis. GRAPHICAL ABSTRACT

Interaction simulation and experimental physico-mechanical analysis of distinct polarity blends of polyethylene and polyvinyl alcohol

Abstract This paper aimed to investigate the interaction of distinct polarity polymer blends of polyethylene and polyvinyl alcohol (PVOH). Molecular mechanics and dynamics simulation were employed to determine the stability of polyethylene and PVOH complexes. It was found that the binding energies ΔE for all complexes of polyethylene and PVOH are negative values indicating that the interactions between both components are favorable to achieve a lower energy hierarchy. Such interactions are induced by the high polarity hydroxyl groups of PVOH which caused weak distortion to the dipole moment of inherently non-polar polyethylene. Furthermore, the molecular simulation results were compared with tensile strength, X-ray diffraction and morphology analyses. Tensile strength analysis revealed there was a reduction of magnitude for varying PVOH before achieving a maximum value. Adding small quantities of PVOH in polyethylene as the different polar elements would affect the ordered structure within the blends. Nevertheless, the reduction is insignificant due to the polarity of PVOH which has a slightly distorted polar network of polyethylene. The addition of PVOH (5–15 parts per hundred) into a polyethylene matrix has significantly reduced the crystallinity of the polyethylene matrix by disturbing the highly ordered arrangement structures.

Investigation of enhancing effect of nano-montmorillonite on fire-retardant added low-density polyethylene–ethylene vinyl acetate hybrid system

In this study, nano-montmorillonite (NMMT) was incorporated in alumina trihydrate (ATH) added low-density polyethylene–ethylene vinyl acetate (LDPE-EVA) for enhancing the mechanical and electrical properties of the hybrid blends. The Young’s modulus of 50 phr ATH added LDPE-EVA (LE) blends has improved significantly, when the NMMT loading level increased from 5 to 15 phr. This is because the intercalation of NMMT particles reduces the cavities while enhancing the interfacial adhesion between the particle surface and LE matrix as observed via morphology analysis. The good interfacial adhesion could effectively transfer the stress from polymer matrix to filler’s particles during straining and improved the mechanical properties. On the other hand, the volume resistivity of 5 phr added LE blends was gradually decreased as the loading level of ATH has increased from 50 to 150 phr. The surface and volume resistivity of LE blends exhibited that high polarity of ATH and NMMT molecules could increase the mobility of charges in passages through polymer matrix and surface. Thus, the incorporation of ATH and NMMT could reduce the electrical resistance of LE blends. In addition, the increasing of ATH loading level also improved fire resistivity of LE blends as indicated by the promising limiting oxygen index. This is because the endothermic reaction of ATH during combustion process could reduce the temperature of polymer blends while releasing water vapour and the formation of alumina char. Furthermore, the increasing of NMMT loading level in ATH-added LE blends was found to slightly increase the fire retardancy. This is due to the addition of NMMT that could promote the dripping characteristics and charring effect during combustion and subsequently improve the fire retardancy of ATH added LE blends.

Evaluation of Microwave Activity on Starch-Based Nanocomposites Reinforced at Different Loading Fraction Organic-to-Inorganic Nanofillers

ABSTRACT When subjected to microwave ageing, the microwave-induced improvement in properties is more significant for sample containing higher loading fraction of cellulose nanofiller. This is due to cellulose nanofiller has greater reactivity to microwave energy through activation of dipole–dipole interaction at the polar interface. The strengthening effects on interface were observed to magnify as a function of microwave power and irradiation time. Nevertheless, the higher montmorillonite fraction tended to inhibit such improvement effect due to the occurrence of intramolecular repulsion between montmorillonite and polysaccharides with insufficient irradiation time, facilitating the water absorption and uneven stress transfer. GRAPHICAL ABSTRACT

Current Development of Electron Beam Irradiation of Natural Rubber–Polymer Blends

ABSTRACT The application of electron beam irradiation in polymers blend with natural rubber such as thermoplastic polymers, specialty polymers, and thermoset polymers are discussed in this paper for the aspects of physical, mechanical, and thermal properties. The interaction of additives and irradiation for natural rubber blends were also been analyzed. The addition of cross-linking agent such as trimetylolpropane trimethacrylate with appropriate amount could enhance the mechanical properties of the polymer–natural rubber blend and lower the optimum dose of electron beam irradiation. In short, electron beam is another potential aspect worth for study in natural rubber research area. GRAPHICAL ABSTRACT

Factorial design investigation on two-way quaternary factors of thermal aging of chlorinated nitrile latex tensile properties

This study aims at investigating the quaternary factors, namely zinc di-N-butyl dithiocarbonmate (ZDBC), sulfur, zinc oxide (ZnO), and potassium hydroxide (KOH) on the tensile strength and elongation of chlorinated nitrile latex film. Full factorial design analysis was employed to examine the factors and their combination two-way interactions with the tensile properties. The factors’ effect on the variability or the stability of the resulting latex films were analyzed as well. The results showed that KOH, which was used to adjust the pH of the latex system greatly affected the tensile strength of the latex film, whereas sulfur has minor influence on tensile strength. Meanwhile, KOH also interacted in combination with ZnO and sulfur to affect the elongation of the latex films. Addition of KOH changed the pH by affecting the electronic repulsion and gelling stability of the latex matrix. Consequently, the variability in tensile strength and elongation of latex film were according to the amount of KOH. Finally, the simple mathematical models with a regression range 0.73–0.86 were developed to relate the factors and the tensile properties of the latex.

Full Factorial Design Analysis on Mechanical Properties of Electron Beam Irradiated-Flame Retarded LDPE/EVA Composites

This study aims to investigate the effect of three factors, namely alumina trihydrate (ATH), montmorillonite (MMT) and irradiation dosage on the mechanical properties (tensile strength and elongation at break) of flame-retarded LDPE-EVA composites. In this study, full factorial design analysis was used to examine the effects of factors and their combination interactions on mechanical properties. ATH is the most significant factor in affecting the tensile strength of LDPE-EVA blends due to the poor compatibility effect between ATH particles and LDPE-EVA matrix. However, MMT is the least significant factor on tensile strength of LDPE-EVA composites. ATH was the most significant in affecting the elongation at break of LDPE-EVA blends. This is because the increasing of ATH amount in LDPE-EVA matrix could restrict the mobolity of polymer chains in LDPE-EVA matrix. However, the factor of irradiation dosage was found to be insignificant in affecting the elongation at break of LDPE-EVA blends.