Thermal and structural studies of polypropylene blended with esterified industrial waste lignin

Microwave-assisted chemical modification of lignin was achieved through esterification using maleic anhydride. Modified lignin (ML) was blended in different proportions up to 25 mass% with polypropylene (PP) using Brabender electronic Plasticorder at 190 °C. The structural and thermal properties of blends were investigated by thermogravometric analysis (TG), differential scanning calorimetry (DSC), wide-angle X-ray diffraction (WAXD) and scanning electron microscopy (SEM). TG analysis showed increased thermal stability of blends due to antioxidant property of ML, which opposed oxidative degradation of PP. DSC analysis indicted slight depression in a glass transition temperature and melting temperature of blends due to partial miscible blend behavior between PP and ML. All blends showed higher crystallization temperatures and continuously reducing percentage crystallinity with increasing ML proportion in the blends. WAXD analysis indicated that PP crystallized in β polymeric form in addition to α-form in the presence of ML. However, proportion of β-form did not show linear relation with increase in ML proportion, thus ML acts as β nucleating agent in the PP matrix. SEM analysis showed good dispersion/miscibility in PP matrix indicating modification in lignin is useful.     

Flame retardant polypropylene through the joint action of sepiolite and polyamide 6

The influence of the incorporation of polyamide-6 (PA) and natural sepiolite nanoparticles on both the thermal degradation and fire behaviour of polypropylene (PP) matrix has been investigated by thermogravimetric analysis (TGA) and mass loss calorimetry. For that purpose, PP/PA blends and nanocomposites thereof were prepared by melt processing. TGA results evidenced that the use of maleic anhydride grafted-polypropylene (MA-g-PP) as compatibilizer led to a significant improvement in thermal stability under air. Such improvement was linked to the formation of a char layer preventing the thermo-oxidative degradation of PP. Interestingly, the thermal resistance of this char layer was further improved by adding 5 wt% of natural sepiolite leading to important increase of time to ignition and reduction of peak of heat release rate (pHRR) during mass loss calorimeter test.     

Thermal degradation and crystallisation studies of reactively compatibilised polymer blends

The thermal degradation and crystallisation behaviours of polyamide12/isotactic polypropylene (PA12/PP) blends were studied. Effects of blend ratio and compatibiliser concentration on the thermal degradation properties of the blends were analysed. The activation energy for degradation in compatibilised and uncompatibilised blends computed using Horowitz-Metzger equation was reported. The blend ratio as well as the presence of compatibiliser has significant effect on the thermal stability of the blends. Phase morphology was found to be one of the decisive factors that affected the thermal stability of both uncompatibilised and compatibilised blends. Melting and crystallisation behaviours of the blends in the presence and absence of compatibiliser were evaluated. It was observed that blending has no significant effect on the melting and crystallisation properties of PA12 and PP. Compatibilisation of 70/30 and 50/50 PA12/PP blends didn't affect the crystallisation and melting behaviours of PA12 and PP even though some discrepancies were observed.     

Thermal degradation studies in poly(vinyl chloride)/poly(methyl methacrylate) blends

The miscibility, morphology, and thermal properties of poly(vinyl chloride) (PVC) blends with different concentrations of poly(methyl methacylate) (PMMA) have been studied. The interaction between the phases was studied by FTIR and by measuring the glass transition temperature (T_g) of the blends using differential scanning calorimetry. Distribution of the phases at different compositions was studied through scanning electron microscopy. The FTIR and SEM results show little interaction and gross phase separation. The thermogravimetric studies on these blends were carried out under inert atmosphere from ambient to 800 °C at different heating rates varying from 2.5 to 20 °C/min. The thermal decomposition temperatures of the first and second stage of degradation in PVC in the presence of PMMA were higher than the pure. The stabilization effect on PVC was found most significant with 10 wt% PMMA content in the PVC matrix. These results agree with the isothermal degradation studies using dehydrochlorination and UV-vis spectroscopic results carried out on these blends. Using multiple heating rate kinetics the activation energies of the degradation process in PVC and its blends have been reported.     

Thermal and photo induced reactions in blends of polypropylene and poly(methyl methacrylate)

Thermal Volatilization Analysis (TVA) demonstrates that poly(methyl methacrylate) (PMMA) is stabilized by blending with polypropylene (PP). Although well-defined radical reactions occur in both polymers under 2537 Å radiation, there is no evidence of the formation of block or graft copolymers when blends of the two are irradiated. Preirradiation suppresses the amount of monomeric methyl methacrylate formed on subsequent thermal degradation. The missing methyl methacrylate units appear in the chain fragment fraction. The characteristics of the thermal degradation of blends of unirradiated PP with preirradiated PMMA are similar to those of unirradiated rather than pre-irradiated blends, thus emphasizing the importance of the PP component in determining the thermal stability of blends after irradiation. These observations are discussed mechanistically.     

Thermal behaviour of compatibilised polypropylene nanocomposite: Effect of processing conditions

The thermal properties and fire behaviour of polypropylene (PP) nanocomposites were investigated using differential scanning calorimetry, dynamic-mechanical analysis, thermogravimetric analysis and glow wire test. In order to study the morphological structure of the materials obtained, TEM and XRD analyses were also carried out. The nanocomposites were prepared using the melt intercalation technique in a co-rotating intermeshing twin screw extruder. Particular attention was given to studying the influence of different processing conditions (barrel temperature profile and screw rate) and compositions of PP-nanoclay blends (clay content, use of compatibiliser) on the thermal properties of the nanocomposites.The results show that all the properties analysed were strongly influenced by the nanocomposite composition; instead, the processing conditions greatly affect only the dynamic-mechanical properties. DSC curves show that the crystallinity is deeply influenced by the presence of the clay in the matrix, owing to the fact that the filler acts as nucleating agent. DMA curves show that materials processed at low temperature profile and high shear stress, i.e. when a good clay dispersion is achieved, are characterised by an enhanced modulus, thus indicating that the incorporation of clay into the PP matrix remarkably enhances its stiffness and has good reinforcing effects. TGA traces in oxidizing atmosphere show a drastic shift of the weight loss curve towards higher temperature and no variation of the onset temperature (i.e. the temperature at which degradation begins). The TGA analyses in inert atmosphere show instead marked increase of this parameter (about 200 °C) and no shift of weight loss curves. Glow wire results highlight that polymer nanocomposites are characterised by enhanced fire behaviour.     

Morphology, thermal stability and visco-elastic properties of polystyrene-poly(vinyl chloride) blends

The morphology, thermal and mechanical properties of polystyrene (PS) blends with 2.5-20 wt% of poly(vinyl chloride) (PVC) have been studied. The measurement of the glass transition temperature (T_g) from the maxima of tan δ data using dynamic mechanical thermal analysis showed that the blends were incompatible and homogenously distributed only within a limited range of PVC contents in PS. The value of the storage modulus was found to increase initially but then decreased with further addition of PVC in the matrix. Distribution of the phases in the virgin and degraded blends was also studied through scanning electron microscopy. The thermogravimetric studies on these blends were carried out under inert atmosphere from ambient to 800 °C at different heating rates varying from 2.5 to 20 °C/min. The thermal decomposition temperatures of blends were found higher than that of pure PS which indicated the stabilizing effects of PVC on PS. The effect varies with the heating rates and the composition of the blends and the phenomenon has been explained due to changing morphology of the blends with composition and the degradation time which affect the interfacial interaction between the degrading products from the polymer components. The kinetic parameters of the degradation process calculated from a method described by Ozawa have been reported for these blends.     

Influence of additives on recycled polymer blends

Polymer systems based on polymer waste offer promising way to increase recycling in the society. Since fillers play a major role in determining the properties and behavior of polymer composites, recycled polymers can also be combined with fillers to enhance the stiffness and thermal stability. In this study, blends of recycled polyethylene and recycled polypropylene with mica and glass fiber were prepared by melt blending technique. The effect of the particle loading, filler type, and filler–matrix interaction on thermal degradation and thermal transition of processed systems were investigated. Thermogravimetric analysis, differential thermogravimetric analysis, and differential scanning calorimetry were used in this investigation. Comparative analysis shows that both fillers produced different effects on thermal properties of the processed systems. These results were confirmed by calculating the activation energy for thermal degradation and thermal transition using Kissinger and Flynn–Wall expressions.     

Properties of immiscible and ethylene-butyl acrylate-glycidyl methacrylate terpolymer compatibilized poly (lactic acid) and polypropylene blends

Poly(lactic acid) (PLA) and polypropylene (PP) blends of various proportions were prepared by melt-compounding. The miscibility, phase morphology, thermal behavior, and mechanical and rheological properties of the blends were investigated. The blends were immiscible systems with two typical morphologies, spherical droplet and co-continuous, and could be obtained at various compositions. Complex viscosity, storage modulus and loss modulus depend on the PP content. Thermal degradation of all blends led to two weight losses, for PLA and PP. The incorporation of PP improved the thermal stability of the blend. The effect of compatibilizer (ethylene-butyl acrylate-glycidyl methacrylate terpolymer, EBA-GMA) on the morphology and mechanical properties of 70/30 w/w PLA/PP blends was investigated. The tensile strength of these blends reached a maximum for 2.5 wt% EBA-GMA, and impact strength increased with increasing EBA-GMA content, suggesting that EBA-GMA is an effective compatibilizer for PLA/PP blends.     

Polymer packaging waste recycling: study of the pyrolysis of two blends via TGA

Journal of Thermal Analysis and Calorimetry - The aim of this work is the evaluation of thermal degradation temperatures of two polymeric blends constituted by polyethylene PE, polypropylene PP,...     

Accelerated weathering of unbleached and bleached Kraft wood fibre reinforced polypropylene composites

In this paper, combined moisture/ultraviolet (UV) weathering performance of unbleached and bleached Kraft wood fibre reinforced polypropylene (PP) composites was studied. Composites containing 40 wt% fibre with 3 wt% of a maleated polypropylene (MAPP) coupling agent were fabricated using extrusion followed by injection moulding. Composite mechanical properties were evaluated, before and after accelerated weathering for 1000 h, by tensile and impact testing. Differential scanning calorimetry (DSC), X-ray diffraction (XRD), thermogravimetric analysis (TGA) and scanning electron microscopy (SEM) were also carried out to assess the changes occurring during accelerated weathering. Bleached fibre composites initially showed higher tensile and impact strengths, as well as higher thermal stability and greater crystallinity. During accelerated weathering, both unbleached and bleached fibre composites reduced tensile strength (TS) and Young's modulus (YM), with the extent of the reduction found to be similar for both unbleached and bleached fibre composites. Evidence supported that the reduction of TS and YM was due to PP chain scission, degradation of lignin and reduced fibre-matrix interfacial bonding.     

PPESK/PES共混物热性能及动态机械性能研究

采用熔融共混法制备了不同重量比例的新型含二氮杂萘酮结构聚芳醚砜酮(PPESK)与聚醚砜(PES)共混物.利用热失重(TGA)及动态热机械仪(DMTA)对该共混物的热性能及动态机械性能进行了研究.研究结果表明,在氮气氛围中,PPESK热分解分为两步反应进行,反应级数n=1,说明PPESK在氮气氛围中的热分解反应类型与β(升温速率)无关而与材料物性有关;采用Ozawa方法得出在15%热失重前,热分解活化能的平均值为240 kJ/mol;随着升温速率的提高,PPESK热降解速率有减缓趋势.在280℃以前,PPESK储能模量值随温度变化较小,保持在较高值,温度在280~330℃之间,储能模量值降低幅度突变.另外,PPESK中加入PES会降低其储能模量值及其热稳定性.     

Mechanical properties of polypropylene (PP) + high‐density polyethylene (HDPE) binary blends: Non‐isothermal degradation kinetics of PP + HDPE (80/20) Blends

In this study, the mechanical properties and non‐isothermal degradation kinetics of polypropylene (PP), high‐density polyethylene (HDPE) with dilauroyl peroxide and their blends in different mixture ratios were investigated. The effects of adding dilauroyl peroxide (0–0.20 wt%) on the mechanical and thermal properties of PP + HDPE blends have been studied. On the other hand, the kinetics of the thermal degradation and thermal oxidative degradation of PP + HDPE (80/20 wt%) blends were studied in different atmospheres, to analyze their thermal stability. The kinetic and thermodynamic parameters such as the activation energy, E_a, the pre‐exponential factor, A, the reaction order, n, the entropy change, the enthalpy change, and the free energies of activated complex related to PP, HDPE, and blend systems were calculated by means of the several methods on the basis of the single heating rate. A computer program was developed for automatically processing the data to estimate the reaction parameters by using different models. Most appropriate method was determined for each decomposition step according to the least‐squares linear regression. Copyright © 2013 John Wiley & Sons, Ltd.     

Thermal stability and ageing properties of sulphur and gamma radiation vulcanized natural rubber (NR) and carboxylated styrene butadiene rubber (XSBR) latices and their blends

The thermal stability of natural rubber (NR) and carboxylated styrene butadiene rubber (XSBR) latices and their blends was studied by thermogravimetric methods. Ageing characteristics of these latex blends were studied by applying hot air oven thermal ageing for seven days at 70 °C. The mechanical properties of the aged samples were studied. Thermal degradation and ageing properties of these individual latices and their blends were investigated with special reference to blend ratio and vulcanization techniques. As the XSBR content in the blends increased their thermal stability was also found to increase. Among sulphur and radiation-vulcanized samples, radiation cured possesses higher thermal stability due to the higher thermal stability of carbon-carbon crosslinks. DTG curves were used for the determination of different stages involved in the degradation. Activation energy for degradation was determined from Coats-Redfern plot. The properties of aged samples were found to decrease due to chain depletion. However, the moduli of XSBR and NR/XSBR blends were found to increase owing to the formation of crosslinks upon ageing.     

Characterization of poly(vinyl acetate)/sugar cane bagasse lignin blends and their photochemical degradation

The acetone-soluble lignin fraction (ASLF) of sugar cane bagasse, from a sugar and alcohol factory residue, was obtained after extraction with formic acid and used to prepare blends with poly(vinyl acetate) (PVAc) by casting. PVAc and ASLF/PVAc blends were irradiated with ultraviolet light (Hg lamp). Blend formation and the irradiation effects were examined through thermal analysis (TG and DSC), scanning electron microscopy, and atomic force microscopy. The DSC results show PVAc glass transition temperature (T _g) shifts because of both, irradiation and ASLF incorporation. Non-irradiated pure PVAc presented a smooth surface, while after UV irradiation, light surface spots are observed. ASLF/PVAc 10/90 and 5/95 blends did not exhibit differences before and after UV irradiation, suggesting that lignin protects PVAc from photochemical degradation.     

TG-FTIR study of the thermal degradation of polyoxymethylene (POM)/thermoplastic polyurethane (TPU) blends

A series of blends of polyoxymethylene (POM)/thermoplastic polyesterurethane (TPU) has been obtained by mechanical processing using a double screw extruder. The thermal stability and the thermal degradation profiles of POM/TPU blends were investigated by thermogravimetric analysis (TG) coupled on-line with Fourier transform infrared spectroscopy (FTIR). It was found that incorporation of TPU into POM matrix resulted in increase of thermal stability of blends in comparison with pristine materials. The thermal degradation of TPU in inert gas atmosphere proceeds in two steps while the thermal degradation of POM is basically a one step process with a substage in a higher temperature range. The most abundant volatile products of the thermal degradation were identified; the possibly routes of their formation have been presented. This revised version was published online in July 2006 with corrections to the Cover Date.     

Study of the miscibility and the thermal degradation of PVC/PMMA blends

The aim of this paper is to study the miscibility and the thermal degradation of PVC/PMMA blends. For that purpose, blends of variable compositions from 0 to 100 wt% were prepared with and without plasticizer. Their physico-chemical characterization was carried out by differential scanning calorimetric analysis (DSC) and Fourier transform infrared spectroscopy (FTIR). Their thermal degradation under nitrogen at 185°C was studied and the HCl evolved from PVC was measured by the pH method. Degraded samples were characterized, after purification, by FTIR and UV-visible spectroscopy. The DSC analysis showed polymer miscibility up to 60 wt% of PMMA. This miscibility is due to a specific interaction of hydrogen bonding type between carbonyl groups (C=O) of PMMA and hydrogen from (CHCl) groups of PVC as evidenced by FTIR analysis. On the other hand, it was found that PMMA exerted a stabilizing effect on the thermal degradation of PVC by reducing the zip dehydrochlorination and by leading to the formation of short polyenes.     

Thermal and Mechanical Properties of Esterified Lignin in Various Polymer Blends

Lignin is an abundant polymeric renewable material and thus a promising candidate for incorporation in various commercial thermoplastic polymers. One challenge is to increase the dispersibility of amphiphilic lignin in lipophilic thermoplastic polymers We altered Kraft lignin using widely available and renewable fatty acids, such as oleic acid, yielding more than 8 kg of lignin ester as a light brown powder. SEC showed a molecular weight of 5.8 kDa with a PDI = 3.80, while the T_g of the lignin ester was concluded to 70 °C. Furthermore, the lignin ester was incorporated (20%) into PLA, HDPE, and PP to establish the thermal and mechanical behavior of the blends. DSC and rheological measurements suggest that the lignin ester blends consist of a phase-separated system. The results demonstrate how esterification of lignin allows dispersion in all the evaluated thermoplastic polymers maintaining, to a large extent, the tensile properties of the original material. The impact strength of HDPE and PLA blends show substantial loss upon the addition of the lignin ester. Reconverting the acetic acid side stream into acetic anhydride and reusing the catalyst, the presented methodology can be scaled up to produce a lignin-based substitute to fossil materials.     

Effect of lignin content on thermal degradation of wood pulp

A series of pulps containing between 3.6 and 23% of lignin was prepared by a careful delignification of a high-yield bisulfite pulp. The pulps were subjected to isothermal pyrolysis in a Perkin-Elmer TGS-1 thermobalance. The measurements were carried out at 8 different temperatures from 325 to 360°C under nitrogen atmosphere. The results obtained indicate that the effect of lignin on degradation depends strongly on temperature. Below 330°C, the rate of degradation varied only little with lignin. This variation becomes more important at temperatures above 330°C in that the rate of degradation increases with decreasing lignin content. The apparent activation energy of degradation ranges from 41.4 kcal mol^?1 at 23% of lignin to 67.0 kcal mol^?1 at 3.7% of lignin.     

Multiwalled carbon nanotube promotes crystallisation while preserving co-continuous phase morphology of polycarbonate/polypropylene blend

The influence of multiwalled carbon nanotubes (MWCNTs) on phase morphology, lamellar structure, thermal stability, melting behaviour and isothermal crystallisation kinetics of polycarbonate/polypropylene (PC/PP) blend nanocomposites has been investigated. Both neat blends and PC/PP (60/40)/MWCNT nanocomposites were prepared by melt mixing method. Morphological analyses were performed by high-resolution X-ray micro-computed tomography and scanning electron microscopy. The co-continuous morphology of the blend was retained irrespective of MWCNT loading. In addition, a substantial refinement in the co-continuous structure was observed. Wide angle and small angle X-ray scattering studies were used to analyse the structural properties of the blend nanocomposites. The addition of MWCNT increases the long period of polypropylene. The influence of addition of MWCNT on the crystallisation temperature and equilibrium melting temperature (Tm°) of polypropylene was followed. The MWCNTs promote crystallisation rate of polypropylene in the blend nanocomposites.