A new approach in compatibilization of the poly(lactic acid)/thermoplastic starch (PLA/TPS) blends

tIn this study, a new compatibilizer was synthesized to improve the compatibility of the poly(lacticacid)/thermoplastic starch blends. The compatibilizer was based on maleic anhydride grafted poly-ethylene glycol grafted starch (mPEG-g-St), and was characterized using Fourier transform infraredspectroscopy (FTIR), dynamic mechanical thermal analysis (DMTA) and back titration techniques. Theresults indicated successful accomplishment of the designed reactions and formation of a starch coredstructure with many connections to m-PEG chains. To assess the performance of synthesized compati-bilizer, several PLA/TPS blends were prepared using an internal mixer. Consequently, their morphology,dynamic-mechanical behavior, crystallization and mechanical properties were studied. The compatibi-lizer enhanced interfacial adhesion, possibly due to interaction between free end carboxylic acid groupsof compatibilizer and active groups of TPS and PLA phases. In addition, biodegradability of the sampleswas evaluated by various methods consisting of weight loss, FTIR-ATR analysis and morphology. Theresults revealed no considerable effect of compatibilizer on biodegradability of samples

Effect of weathering on physical and mechanical properties of hybrid nanocomposite based on polyethylene, woodflour and nanoclay

Wood plastic composites have received increasing attention during the last decades, because of many advantages related to their use. However the durability of Wood plastic composites after ultraviolet exposure has become a concern. In this research, hybrid nanocomposites of polyethylene and woodflour with different concentrations of nanoclay were fabricated using melt compounding followed by injection molding. Specimens were exposed for 2000 h to ultraviolet radiation and moisture cycling in a laboratory weathering device to simulate the effects of exposure to sunlight and rain. Physical and mechanical properties of the nanocomposites were evaluated, before and after weathering. The results indicated that the water absorption of wood plastic composites increased after weathering but nanoclay reduced the intensity of weathering to some extent, through decreasing of water absorption. Also results showed that weathering decreased modulus of elasticity values, however good dispersion of clay layers resulted in fewer drop of modulus of elasticity values. Fourier transform infrared spectroscopy showed that lowest carbonyl index is related to the nano wood plastic composites with 2wt% nanoclay. Also X-Ray diffraction patterns revealed that intercalation morphology has been formed for nano particles

Oxygen-barrier films based on low-density polyethylene/ ethylene vinyl alcohol/ polyethylene-grafted maleic anhydride compatibilizer

In this research, high oxygen-barrier films were organized based on low-density polyethylene (LDPE)/ ethylene vinyl alcohol (EVOH)/ polyethylene-grafted maleic anhydride (LDPE-g-MA) compatibilizer. The effects of 10–30 wt. % EVOH and 0–10 wt. % LDPE-g-MA loadings on the properties of final films were evaluated. The morphology of specimens was observed by using scanning electron microscopy (SEM). Oxygen transfer rate (OTR) results revealed that the addition of EVOH up to 30 wt. % to neat LDPE could significantly decrease oxygen permeability. The LDPE-g-MA which increased the permeability needed to be fine-tuned its amount based on the EVOH loading in different samples. The experimental results revealed that the addition of 30 wt. % EVOH to the LDPE matrix without adding LDPE-g-MA gave the best oxygen barrier properties. Elastic modulus and tensile strength increased with incorporation of EVOH and LDPE-g-MA into the polyethylene matrix. On the other hand, elongation-at-break decreased with the addition of EVOH and increased with the introduction of compatibilizer to the samples. Incorporation of EVOH and LDPE-g-MA into the LDPE matrix and increasing their amounts led to higher storage modulus and zero shear rate viscosity, but lowered the frequency value at the intersection point of storage modulus (G') and loss modulus (G''). The only exception was that in the samples without compatibilizer, the increase in the EVOH content resulted in a lower zero shear rate viscosity and a higher frequency value at the intersection point of G' and G''

An investigation on non-isothermal crystallization behavior and morphology of polyamide 6/ poly(ethylene-co-1-butene)-graft-maleic anhydride/organoclay nanocomposites

Nanocomposites based on polyamide 6 (PA6) and poly(ethylene-co-1-butene)-graft-maleic anhydride (EB-g- MAH) blends have been prepared via melt mixing. The effect of blend ratio and organoclay concentration on the crystallization and melting behavior of specimens were studied. Three types of commercial organo-modified clay (Cloisite 30B, Cloisite 15A and Cloisite 20A) were employed to assess the importance of the nanoclay polarity and gallery distance. The crystallization behavior was investigated using differential scanning calorimetry (DSC) and wide angle X-ray diffraction spectroscopy (WAXD). The strong interactions between amine end groups of PA6 and maleic anhydride groups of EB-g-MAH led to complete inhibition of EB-g-MAH crystallization according to the DSC results. A transformation from the α form to the γ form crystals of PA6, induced by both organoclays and EB-g-MAH, was monitored by WAXD and DSC. Small angle X-ray scattering (SAXS) was used to evaluate the morphology of nanocomposites. Moreover, transmission electron microscopy (TEM) was conducted to determine the location of organoclays and indicated that the organoclays mainly present in the PA6 matrix and rarely distribute in the EB-g-MAH phase in the case of low polarity organoclays. It was also evidenced that the organoclay with the most affinity to PA6 (Cloisite 30B) had the largest effect on the thermal and crystallization behavior of this phase in the blend

Effect of weathering on the properties of hybrid composite based on polyethylene, woodflour, and nanoclay

Hybrid composites of polyethylene/wood flour/nanoclay with different concentrations of nanoclay were fabricated using melt compounding followed by injection molding. Composites were weathered in a xenon-arc type accelerated weathering apparatus for 2000 h. Physical properties of the composites were evaluated by colorimetery and water absorption before and after weathering. Changes in surface chemistry were monitored using spectroscopic techniques. The results indicated that water absorption of the composites increased after weathering, but nanoclay can reduce the intensity of weathering to some extent by decreasing water absorption. Weathering increased the degree of color change and lightness of the samples; however, the lightness of the samples containing nanoclay was less than that of neat wood-plastic composites. Fourier transform infrared spectroscopy revealed a lower carbonyl index of composites containing nanoclay. X-ray diffraction patterns revealed that the nanocomposites formed were intercalated. The order of intercalation for samples containing 2 wt% nanoclay was higher than that of 4 wt% at the same maleic anhydride grafted polyethylene content, due to some agglomeration of the nanoclay

Investigating the effect of graphene oxide nanosheets on the barrier properties of high density polyethylene coated by layer-by-layer assembly method

Hypothesis: A nanocomposite layer including graphene nanosheets could be used to enhance the barrier properties of high density polyethylene through a layer-by-layer assembly method. Planar graphene nanoparticles help to decrease the gas permeability of polyethylene substrates by making a tortuous pathway for gas molecules transmittance.Methods: Two different methods were used to increase the barrier properties of high density polyethylene and the results were compared with each other. In the first method, a thin film of polymer nanocomposite including graphene oxide nanoparticles and polyvinyl alcohol was coated on the surface of high density polyethylene film using a film applicator. The effective variables in this method were the weight fraction of graphene oxide particles in polyvinyl alcohol and thickness of the nanocomposite layer. In the second method, a layer-by-layer assembly was used. Chitosan solution acted as a positive charge and graphene oxide suspension in water was utilized as a negative charge.Findings: In high density polyethylene samples coated by polyvinyl alcohol nanocomposite (10 micrometers), the oxygen transmittance rate decreased drastically to 3 cm3m2 bar. This decrease was expected due to the structure of polyvinyl alcohol and its inherent barrier properties. By adding graphene oxide into polyvinyl alcohol, the permeability values showed a slight decrease and reached 0.8 cm3 m2 bar.Statistical analysis based on the surface response method for the layer-by-layer method showed that permeability depends on pH, number of bilayers and graphene concentration. At high pH, the graphene oxide sheets take on a smoother and more stretched shape and are more likely to aggregate, which increases permeability

Design and Characterization of Novel Potentially Biodegradable Triple-Shape Memory Polymers Based on Immiscible Poly(l-lactide)/Poly(ɛ-caprolactone) Blends

In this study, covalently cross-linked network strategy has been applied to prepare new triple-shape memory polymers (TSPs) based on poly(l-lactide) (PLA)/poly(ɛ-caprolactone) (PCL) blends. The TSPs were fabricated by adding di-cumyl peroxide, with triallyl isocyanurate as a coagent for performing the cross-linking reaction. The differential scanning calorimetry (DSC) analysis demonstrated that all the PLA/PCL blends show two melting points (T m,PCL and T m,PLA ), which can be employed as the transition temperature (T trans ) to induce triple-shape memory behavior. The scanning electron microscopy (SEM) analysis indicated that there are two immiscible morphologies: co-continuous structure and matrix-droplet. The influence of temperature on the crystalline phase changes was analyzed by X-ray diffraction at various temperatures. The results revealed that during the heating–cooling cycle, the degree of crystallinity decreased when the temperature increased and at higher temperature, the crystallization peaks of PCL disappeared. Multiple thermal–mechanical tests were performed and the results showed that the composition ratio of the two phases plays an important role in the triple-shape memory behavior. The results confirmed that the excellent shape memory behavior was obtained for the sample containing 50 wt% PCL

Nanocomposites based on poly(L-lactide)/poly(epsilon-caprolactone) blends with triple-shape memory behavior: Effect of the incorporation of graphene nanoplatelets (GNps)

In this study, a novel thermally actuated triple-shape memory polymer (triple-SMP) based on poly(L-lactide) (PLA)/poly(ε-caprolactone) (PCL)/graphene nanoplatelets (GNps) nanocomposite was prepared by facile solution mixing method and the design of which was based on two well-separated melting temperatures. In order to improve the dispersion of GNps in the matrix, functionalization reactions were carried out on the GNPs surface. Functionalization was confirmed by various techniques including FTIR, Raman and TGA analysis. TEM micrographs revealed an exfoliated morphology for the functionalized GNps (FGNps) and a homogenous dispersion in the matrix. The crystallinity behaviour of nanocomposites was investigated by DSC and variable temperature XRD (VT-XRD) analysis and an increase in crystallinity was observed. Dynamic mechanical analysis (DMA) showed that the presence of FGNps improves the fixity and recovery ratios because of increase in crystallinity and thermal conductivity. The best shape memory behavior was obtained for PLA50/PCL50/FGNp 1.5 nanocomposite