Manus Seadan

Effect of Nanoclay Addition on Morphology and Elastomeric Properties of Dynamically Vulcanized Natural Rubber/Polypropylene Nanocomposites

Abstract Thermoplastic vulcanizate (TPV) nanocomposites based on 60/40 (%wt) natural rubber (NR)/polypropylene (PP) blends were prepared by melt blending in an internal mixer. Sodium montmorillonite (Na-MMT) was first added in natural rubber latex to obtain natural rubber/clay masterbatch, which was subsequently dynamically crosslinked while mixing with molten PP. The effect of Na-MMT content were examined concerning elastomeric properties of NR/PP blends dynamically vulcanized using phenolic resin as a curing agent. Morphology characterization observed by X-ray diffraction (XRD), transmission electron microscopy (TEM) and 3D microfocus X-ray computerized tomography showed that the dynamic vulcanization with nanoclay addition changed the blend morphology from a co-continuous-like structure to droplet-like phase one, and the clay remained within NR phase in intercalated and aggregated forms. Furthermore, the presence of clay induced the decrease in crosslinking of NR, but promoted the mixing between NR and PP during dynamic vulcanization. This suggested that nanoclay worked as a kind of morphology modifier during dynamic vulcanization. The addition of clay marginally enhanced the 100 % modulus and tensile strength, but led to the decrease of the elongation at break. The optimal level of tensile strength improvement was obtained with loading of 5 phr clay. The permanent set of the NR/PP/Clay TPV nanocomposites was well maintained at the acceptable level as elastomer. The resistances to oil and heat were improved with incorporation of clay, proportional to clay loading. The experimental results indicated that the nanoclay had a positive effect on improving the 60/40 NR/PP blend morphology, which provided a little benefit to strength of the TPVs. However, the addition of nanoclay offered an improvement in oil and thermal resistances due to a combined effect of the clay dispersion and improved morphology of NR and PP blends.

Impact property enhancement of poly (lactic acid) with different flexible copolymers

The objective of this work was to improve the impact property of Poly (lactic acid) (PLA) by blending with different copolymers. Six flexible copolymers, namely, acrylonitrile butadiene styrene (ABS) powder, Biomax, polybutyrate adipate co-terephthalate (PBAT), polyether block amide (PEBAX), ethylene-vinyl acetate (EVA) and ethylene acrylic elastomer (EAE), with loading less than 20wt% were used and compared. The rheological, mechanical and morphological properties of samples were investigated by melt flow index, tensile testing, impact testing and scanning electron microscope (SEM), respectively. It was found that PLA added 20wt% EAE showed the highest impact strength (59.5 kJ/m2), which was 22 times higher than neat PLA. The elongation at break was also increased by 12 folds compared to neat PLA. The SEM images showed good interface and distribution for PLA containing 20wt% EAE, 15 phr Biomax and 20 wt% PEBAX.

Sustainable Biocomposites from Rice Flour and Sisal Fiber: Effect of Fiber Loading, Length and Alkali Treatment

Abstract Rice flour was modified with water and glycerol in single-screw extruder to obtain bioplastic of low manufacturing cost. Sisal fibers were used as reinforcing fillers to enhance rice flour-based bioplastic properties. The effects of short sisal fiber content (5 to 20 wt.%), length (0.2 to 6 mm) and alkali treatment (5% w/v NaOH) on the moisture content, tensile properties, impact properties, dynamic mechanical properties and morphology of the biocomposites were studied. The results showed that incorporation of the sisal fibers with a fixed fiber length into the bioplastics improved moisture resistance, tensile strength, impact strength and storage modulus, and that the improvement level increased with increasing sisal fiber content. The optimum reinforcement was achieved at 20 wt.% of fiber loading and 4 mm long fibers. The tensile strength of the biocomposite was about 4 times more than that of the neat rice flour-based bioplastic. The use of 5% NaOH aqueous solution further improved the moisture resistance and mechanical properties of the biocomposites, mainly resulting from better interfacial adhesion between the sisal fiber and rice flour matrix. Furthermore, the performance of the rice flour-based bioplastics synergistically combined with the sisal fibers suggests that they have great potential in development of environmentally friendly/sustainable biomaterial products from renewable resources.

Effect of Glycerol and Reactive Compatibilizers on Poly(butylene succinate)/Starch Blends

A one-step process in an internal mixer was used to prepare Poly(butylene succinate) (PBS)/high-loading modified tapioca starch (30-40 wt%) blends with low glycerol content (10-20 wt% of starch) as a plasticizer. To promote a good compatibility, two reactive agents, maleic anhydride (MA)/peroxide and methylene diphenyl diisocyanate (MDI), were selected and compared. The mechanical properties, morphology, and Molau test of the blends were investigated. The compatibility of PBS/starch blends was improved by both reactive agents at the suitable plasticizer loading (glycerol 10 wt% of starch). It was demonstrated that increasing mechanical properties resulted in good adhesion of PBS/starch interface and small evenly dispersed starch particles. MA/peroxide of 0.20/0.01 phr/phr and MDI of 0.2 phr were sufficient to improve the mechanical properties of PBS/starch (60:40 and 70:30) blends at 10 wt% glycerol (of starch). The results from the Molau test confirmed the formation of graft-copolymer at the interface when compatibilizers were added.

Effect of PDLA and Amide Compounds as Mixed Nucleating Agents on Crystallization Behaviors of Poly (l-lactic Acid)

The improvement of the rate of crystallization and crystallinity of poly (l-lactic acid) (PLLA) is one of the key performance elements for PLLA to perform better at the higher temperature than its heat deflection temperature (around 60 °C). The organic nucleating agent compounds are one of the interesting choice as they can offer the clarity of products. On the other hand, the nucleated PLLA can be prepared using a low molecular weight poly (d-lactic acid) (PDLA). The aim of this work was to explore the effect of an unsaturated amide compound and PDLA as single and mixed nucleating agents used for PLLA. The crystallization rate and kinetics were investigated and compared for the synthetic unsaturated amide compound (N,N′-ethylenebis (10-undecenamide) (EBU)) and commercial hydrazide compound (tetramethylenedicarboxylic dibenzoylhydrazide (TMC-306)). PLLA samples was prepared by melt-mixing with TMC or EBU incorporated with peroxide. The influence of different nucleating agents loading on thermal properties, crystallization behaviors, and rheological properties of PLLA were explored by differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA). The results showed that the addition of EBU or TMC 0.5 phr could pronouncedly increase the crystallinity of PLLA from 3.80% to 24.84% and 8.61%, respectively. The crystallization peak appeared at 112.3 °C in the cooling scan at the rate 7 °C/min when addition EBU and peroxide into PLLA. This indicated that EBU acted as an efficient nucleating agent for PLLA. In isothermal crystallization run at 110 °C, it was found that the overall crystallization rate of nucleated PLLA with TMC or EBU was much faster than neat PLLA. The crystallization half-time indicated that the existence of TMC or EBU could slightly decrease to 2.90 and 1.96 min, respectively compared to neat PLLA (4.60 min). Finally, a low molecular weight PDLA with different contents between 3 and 7 wt % was added in PLLA with EBU and peroxide to investigate the effect of mixed nucleating agents. The crystallization rate of the incorporation of PDLA/EBU/peroxide into PLLA was discussed with the proposed crystallization mechanism. The results revealed the stereocomplex temperature peak at 207 °C as well as normal melting temperature of PLLA. The kinetics of growth crystallization, the crystallization half-time of PLLA at 110 °C was reduced from 4.60 min to 1.96 min (when adding EBU alone) and to 2.62 min (when using mixed PDLA and EBU).

Facile Preparation and Characterization of Short-Fiber and Talc Reinforced Poly(Lactic Acid) Hybrid Composite with In Situ Reactive Compatibilizers

Hybrid composites of fillers and/or fibers reinforced polymer was generally produced by masterbatch dilution technique. In this work, the simplified preparation was introduced for the large volume production of 30 wt % short-fiber and talcum reinforced polymer hybrid composite by direct feeding into twin-screw extruder. Multifunctional epoxide-based terpolymer and/or maleic anhydride were selected as in situ reactive compatibilizers. The influence of fiber and talcum ratios and in situ reactive compatibilizers on mechanical, dynamic mechanical, morphological and thermal properties of hybrid composites were investigated. The morphological results showed the strong interfacial adhesion between fiber or talcum and Poly(lactic acid) (PLA) matrix due to a better compatibility by reaction of in situ compatibilizer. The reactive PLA hybrid composite showed the higher tensile strength and the elongation at break than non-compatibilized hybrid composite without sacrificing the tensile modulus. Upon increasing the talcum contents, the modulus and storage modulus of hybrid composites were also increased while the tensile strength and elongation at break were slightly decreased compared to PLA/fiber composite. Talcum was able to induce the crystallization of PLA hybrid composites.

Partially Dynamically Vulcanized Thermoplastic Elastomer Based on Natural Rubber-Polypropylene-Clay Nanocomposites

Thermoplastic vulcanizate (TPV) nanocomposites based on 60/40 (%wt) natural rubber (NR)/polypropylene (PP) blends were prepared by dynamic vulcanization. Sodium montmorillonite (Na-MMT) was use as a filler to improve TPV properties. The addition effect of Na-MMT on the TPV properties was examined. The results indicated that the blend exhibited a co-continuous phase structure. The presence of clay in the NR phase decreased crosslinking level of NR, but improved mixing of NR and PP during dynamic vulcanization. The addition of clay marginally enhanced the 100% modulus and tensile strength, but decreased elongation at break due to more homogeneous blend morphology. The optimal level of tensile strength improvement was obtained when loading of clay was 5 phr. The permanent set of the blends did not changed significantly with the clay dispersion. The storage modulus and resistance to oil and heat improved with incorporation of clay, proportional to clay loading.

Response of Modified Poly(lactic acid) to Microwave Radiation

The frozen instant food packaging is the one of disposal product, which produced from petroleum–based plastic and has been accumulated worldwide pressuring on the environment. Therefore, the biodegradable plastics have become key candidates in this application. Poly(lactic acid) (PLA) was regarded as one of the most promising biodegradable polymer due to its good mechanical properties. The aim of this work was to study on the freezability and microwavability of PLA through crosslink reaction. For the improvement of the processibility of PLA, hyperbranched polymer (HBP) and polypropylene glycol (PPG) were used as plasticizer. Then the crosslinking of PLA was introduced by addition of peroxide (Luperox101) and triallyl isocyanurate (TAIC) in an internal mixer. Neat and modified PLA samples were characterized and testing for mechanical properties. From the gel content results, it was showed the increased value with the increased content of TAIC due to the denser crosslinked structure of polymer. This result was confirmed by FT-IR spectra. All modified PLA samples showed the higher %strain at break than neat PLA. In addition, impact resistance in frozen state showed the results of modified PLA with 0.1wt% of peroxide and 0.15 wt% of TAIC, was higher than neat PLA. Moreover, this composition also showed the highest microwave response and heat accumulation was suppressed when the specimen was immersed in the water during the test. From the results obtained in this work, the further investigation is needed to pursue and elucidate the relationship between the polymer structure and heat absorption when materials undergo the microwave radiation.

Properties of Compatibilized SAN/NR Blends

The blend of poly(styrene-co-acrylonitrile) (SAN) and natural rubber (NR) is immiscible and incompatible which lead to poor mechanical properties. Many methods can be carried out to improve the compatibility. In this work, the potential of various reactive compatibilizers in SAN and NR blend was explored. The morphological and mechanical properties were compared. The melt blending of SAN and NR were prepared in an internal mixer with various types of reactive agent such as styrene-co-maleic anhydride (SMA), maleic anhydride (MA), peroxide and mixed reactive agents. The morphological textures of the blends were investigated by scanning electron microscope. Mechanical properties including tensile strength, impact strength and elongation at break were measured. The results of morphological observations revealed that SAN/NR blend with reactive agent, the mixture of SMA and MA show the smallest and the most uniform dispersed NR particles, where the size of NR particle is about 1 µm. The mechanical properties of the blends revealed impact strength and elongation at break were increased with addition of reactive agents. SAN/NR blend with the mixture of SMA and MA showed the highest elongation at break but it had lower impact strength than the blend with SMA.

Reactive Blends of Poly(butylene adipate-co-terephthalate) and Thermoplastic Starch

The blend of poly(butylene adipate-co-terephthalate) (PBAT) and thermoplastic starch (TPS) are a promising way to get a new class of bio-compostible plastic, balance the cost effective issue and good mechanical properties. Blends of both polymers are immiscible in nature. Therefore, to make the blend to be more compatible, some block-copolymer compatibilizer can be introduced. Reactive blend is one of effective ways to create such compatibilization at the interface. The objective of this work was to study the reactive blends of PBAT/TPS in comparison to the physical blend. The reactive blends were prepared in both an internal mixer and a twin-screw extruder. For reactive blends in twin-screw extruder, PBAT, starch, glycerol and reactive agent were all pre-mixed and blended in an extruder on one step process. The weight ratio of PBAT:TPS (starch + glycerol) was fixed at 60:40. The reactive agent maleic anhydride (MA) and peroxide (Luperox® 101) were used at very low level 0-0.1 phr. The mechanical properties, morphology and flows property of blends were characterized using tensile machine, scanning electron microscope (SEM) and melt flow indexer (MFI). The internal mixer torque showed a decrease in a final torque value of TPS when MA being added, confirming the chain scsision reaction of TPS. The finer morphogy and better mechanical properties were obtained in the reactive blend with 0.1 phr of MA and 0.1 phr of peroxide.