Tg Depression Research Articles

Effect of counterions on the water sorption and glass transition properties of maltobionate salts

AbstractThe purpose of this study was to clarify the effect of counterions on the water sorption and glass transition properties of maltobionate salts. Sodium maltobionate (NaMb), potassium maltobionate (KMb), and magnesium maltobionate (MgMb2) were employed, and the values for calcium maltobionate (CaMb2) and maltose were taken from the literature. The water sorption isotherm of the samples was characterized using the Guggenheim-Anderson-de Boer model. The glass transition temperature (Tg) and freeze-concentrated glass transition temperature (Tg’) were evaluated by differential scanning calorimetry. The effect of water content on the Tg was analyzed using the Gordon-Taylor model. The order of the anhydrous Tg values of maltobionate salts was: KMb < NaMb < maltose < MgMb2 < CaMb2. The anhydrous Tg of the divalent cation forms (MgMb2 and CaMb2) was much higher than that of the monovalent cation forms (NaMb and KMb). The anhydrous Tg will be affected by the plasticizing effect and electrostatic effect of cations. The Tg depression induced by water plasticizing was greater for KMb than for the other maltobionate salts. The order of Tg’ values of freeze-concentrated maltobionate salts was: KMb < maltose < NaMb < MgMb2 < CaMb2. This trend was almost the same as that seen for anhydrous Tg, but the range of the Tg’ values (242.2–257.8 K) was much lower than that of the anhydrous Tg (346.9–421.3 K). The Tg’ appears to be affected by the strength of ionic interactions and amount of unfrozen water.

Improvement of the glass transition temperature in novel molybdenum carbide doped polyaniline nanocomposites

Several studies have revealed that the glass transition temperature (Tg) of polymer nanocomposites (PNCs) may change upon the loading of even a small number of nanoparticles (NPs). However, the exact phenomenon behind such shifting in Tg is still not well known. This study uses experimental and MD simulation approaches to explore the physics of the Tg of polyaniline (PANI) nanocomposite with molybdenum carbide (Mo2C) nanoparticles at different weight percentage loading of NPs. The experimental study shows that, at a lower wt-% loading of NPs, the Tg of the resulting PNCs decreases slowly, and above a particular loading wt-%* (30 wt-%), the depression in Tg becomes more serious. The SEM images show that for wt-% < wt-%*, NPs remain diffuse in the polymer matrix, and for wt-%t > wt-%* a large number of NPs surround the polymer. The MD simulation reveals a slow increase in the diffusion of polymer and NPs for wt-% < wt-%* and a sudden increase for wt-%t > wt-%*. The measurement of the radius of gyration of the polymer reveals swelling of the polymer for wt-% < wt-%* and contraction of the polymer for wt-%t > wt-%*. Moreover, the variations of the diffusion constants and the radius of gyration of the polymer are consistent with the Tg behaviour of PNCs.

Molecular Dynamics Simulation of the Influence of External Electric Fields on the Glass Transition Temperature of the Ionic Liquid 1-Ethyl-3-methylimidazolium Bis(trifluoromethylsulfonyl)imide

We present the results of molecular dynamics simulations of the ionic liquid (IL) 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide [C2C1im][NTf2] in the presence of external electric fields (EEFs) of varying strengths to understand the effects of EEFs on the glass transition temperature Tg. We compute Tg with an automated and objective method and observe a depression in Tg when cooling the IL within an EEF above a critical strength. The effect is reversible, and glasses prepared with EEFs recover their original zero-field Tg when heated. By examining the dynamics and structure of the liquid phase, we find that the EEF lowers the activation energy for diffusion, reducing the energetic barrier for movement and consequently Tg. We show that the effect can be leveraged to drive an electrified nonvapor compression refrigeration cycle.

Effects of water-soluble additive on the release profile and pharmacodynamics of triptorelin loaded in PLGA microspheres

A satisfactory drug release profile for gonadotropin-releasing hormone (GnRH) agonist drugs is high initial release followed by small amount of drug release per day. In the present study, three water-soluble additives (NaCl, CaCl2 and glucose) were selected to improve the drug release profile of a model GnRH agonist drug-triptorelin from PLGA microspheres. The pore manufacturing efficiency of the three additives was similar. The effects of three additives on drug release were evaluated. Under the optimal initial porosity, the initial release amount of microspheres containing different additives was comparable, this ensured a good inhibitory effect on testosterone secretion in the early stage. For NaCl or CaCl2 containing microspheres, the drug remaining in the microsphere depleted rapidly after the initial release. The testosterone concentration gradually returned to an uncontrolled level. However, for glucose containing microspheres, it was found that the addition of glucose could not only increase the initial release of the drug but also assist in the subsequent controlled drug release. A good and long-time inhibitory effect on testosterone secretion was observed in this formulation. The underlying cause why the incorporation of glucose delayed the subsequent drug release was investigated. SEM results showed that considerable pores in glucose containing microspheres were healed during the microspheres incubation. After thermal analysis, an obvious glass transition temperature (Tg) depression was observed in this formulation. As Tg decreased, polymer chains are able to rearrange at lower temperatures. This, morphologic change was reflected in the gradual closure of the pores, and is the likely reason that drug release slowed down after the initial release. HIGHLIGHTS The addition of glucose could not only increase the burst release of the drug but also delay the subsequent drug release. High initial burst and a sustained drug release helped obtain a good inhibitory effect on testosterone secretion. As Tg decreased, polymer chain was prone to rearrange. Morphologic change was reflected in the gradual closure of the pores. This was the reason that drug release slowed down after the initial burst.

Physical stability of co-freeze-dried powders made from NaCl and maltodextrins – Impact of NaCl on glass transition temperature, water vapour sorption isotherm and water vapour sorption kinetics

NaCl is commonly added into food powders as a humectant or taste enhancer with little consideration of its impact on the physical properties and stability of powders. In this study, maltodextrins of dextrose equivalence (DE) 5, 20 and 45 and 10%w/w NaCl were first dissolved in water and then freeze-dried to produce powder mixtures. After freeze drying, maltodextrin DE 20-NaCl and maltodextrin DE 45-NaCl mixtures were amorphous based on powder X-ray diffraction and scanning electron microscopy-energy dispersive X-ray spectroscopy analyses while NaCl partially recrystallized in the maltodextrin DE 5 mixture. Compared to the corresponding pure maltodextrin, freeze-dried maltodextrin DE 5-NaCl blend had a lower glass transition temperature (Tg). Furthermore, the Tg depression effect of NaCl increased with maltodextrin molecular weight. Also, freeze-dried maltodextrin 20/45-NaCl mixtures had greater hygrocapacities than their respective maltodextrins throughout the aw range investigated (0.05–0.50). The impact of molecular mixing via freeze drying versus dry mixing on the sorption behaviour of maltodextrin-NaCl blends was also investigated. Freeze-dried maltodextrin-NaCl absorbed the most moisture (from 20% to 70%RH), followed by dry-mixed blends, which absorbed more moisture than predicted after 60, 50 and 40%RH for maltodextrin DE 5, 20 and 45-NaCl mixtures, respectively. In all, formulating NaCl with maltodextrin caused freeze-dried maltodextrin-NaCl blends to be more temperature- and moisture-sensitive.

Single-Ion Conducting Polymer Electrolytes Based on Random Polyurethane–Urea with Different Diisocyanate Structures for Lithium Batteries

Polyurethane–urea ionomers based on poly(ethylene oxide) (PEO) with various hard segment contents were synthesized from diisocyanates with different symmetries and planarities. The influence of the random copolymer microphase structure (including the phase separation morphology and hydrogen bonding behavior) on the ion states and ion migration was investigated. The soft phase could maintain a low glass transition temperature to yield samples with good ionic conductivity when the hard segment was less than 48 wt %. Furthermore, the hard phase and hydrogen bonds could provide good mechanical strength. Fourier transform infrared spectroscopy and small-angle X-ray scattering confirmed that ionomers with a smaller degree of phase separation had a high fraction of ions in isolated ion pairs. Coupled with faster segmental dynamics and ion mobility from the depressed Tg, the polyurethane–urea ionomer simultaneously showed high strength and ionic conductivity. After plasticization, the prepared single-ion conductor was successfully tested in lithium cells, demonstrating outstanding discharge capacity (166 mAh g–1), Coulombic efficiency (96.5%), and retention (92.6% after 100 cycles) at 0.1 C and high temperature.

Moisture effects leading to Tg depression in GFRP composites: An analysis

Eighteen ply hand laid-up, epoxy resin-E-glass composite samples were exposed to different ageing environments. These included hydrothermal immersion, hygrothermal treatment and ageing processes carried out in the open, outdoors. Low temperature Differential scanning calorimetry (DSC) was employed to compute the Glass Transition Temperature (Tg) of the treated test specimens. These Tg values were compared with the as-cured Tg values of the samples. A Tg depression was observed in samples treated in all the ageing processes, higher depressions being associated with higher periods of exposure. Severe ageing conditions outdoors, accounted for the highest Tg depressions.

Role of hydrogen bonding in wheat gluten protein systems plasticized with glycerol and water

Many biopolymers are stiff and brittle and require plasticizers. To optimize the choice and amount of plasticizer, the mechanisms behind plasticization need to be understood. For polar biopolymers, such as polysaccharides and proteins, plasticization depends to a large extent on the hydrogen bond network. In this study, glycerol-plasticized protein systems based on wheat gluten were investigated, in combination with the effects of water. The methodology was based on a combination of mechanical tests and molecular dynamics simulations (MD). The simulations accurately predicted the glycerol content where the experimental depression in glass transition temperature (Tg) occurred (between 20 and 30 wt% plasticizer). They also predicted the strong water-induced depression in Tg. Detailed analysis revealed that in the dry system, the main effect of glycerol was to break protein-protein hydrogen bonds. In the moist system, glycerol was partly outcompeted by water in forming hydrogen bonds with the protein, making the glycerol plasticizer less effective than in dry conditions. These results show that MD can successfully predict the plasticizer concentration at which the onset of efficient plasticization occurs. MD can therefore be an important tool for understanding plasticizer mechanisms, even in a complex system, on a level of detail that is impossible with experiments.

Effect of processing techniques and residual solvent on the thermal/mechanical properties of epoxy‐cellulose nanocrystal nanocomposites

AbstractEpoxy nanocomposites reinforced with 0–5 wt% cellulose nanocrystal (CNC) were fabricated by solution casting method. The CNCs were first dispersed in the hardener together with a co‐solvent and subsequently mixed with epoxy monomer using two different protocols: bulk mixing and dropwise mixing. The dropwise mixing resulted in more homogeneously‐dispersed CNCs and provided better mechanical properties, particularly higher tensile strength, tensile modulus, and work of fracture with increasing CNC content. Investigation of various CNC/hardener mixtures with different solvent content showed that the residual solvent in the composite mixture had an impact on the curing behavior of the nanocomposite epoxy and may have lowered its crosslinking density, leading to Tg depression. However, the presence of the solvent was shown to be essential for the preparation of a well‐dispersed CNC phase in the hardener solution, and to form homogenous composite mixtures. Our results show that the reinforcement effect due to higher CNC concentration is more significant than the solvent effect in the hardener system and shows greater improvement in mechanical properties. The CNC component reversed the solvent plasticizing effect through its superior mechanical reinforcing effects, and the dropwise mixing process led to better dispersion compared with the bulk mixing process.

Thermodynamic and Kinetic Transitions of Liquids in Nanoconfinement.

Core principles of chemistry are ubiquitously invoked to shed light on the nature of molecular level interactions in nanoconfined fluids, which play a pivotal role in a wide range of processes in geochemistry, biology, and engineering. A detailed understanding of the physicochemical processes involved in the flow, structural transitions, and freezing or melting behavior of fluids confined within nanometer-sized pores of solid materials is thus of enormous importance for both basic research and technological applications.This Account provides a perspective on new insights into the thermodynamic and kinetic transitions of nanoconfined fluids in their stable and metastable forms. After briefly introducing the unique properties of mesoporous silicas from the SBA, MCM, and FDU families that serve as the confinement matrices, combining highly ordered single and bimodal mesopore architectures with tunable pore sizes in the ∼2-15 nm range and narrow size distributions, recent studies on melting/freezing behavior of water confined in these host matrices are reviewed. While differential scanning calorimetry (DSC) reveals a linear relationship between melting point depression and pore size (independent of the pore shape), as predicted by the Gibbs-Thomson relation, variable temperature 2H wide-line nuclear magnetic resonance (NMR) spectroscopy studies confirm the core-shell model of water and give evidence for a layer-by-layer freezing mechanism, which gives rise to an apparent fragile-to-strong transition in the solidification dynamics.In contrast to the freezing/melting behavior of water, the effect of nanoconfinement on the glass transition of supercooled liquids is nonuniversal and the glass transition temperature Tg can either increase or decrease with the dimensionality and extent of confinement. This nonuniversal behavior is exemplified by the two glass-forming molecular liquids, glycerol and ortho-terphenyl (OTP). While glycerol shows an increase in Tg and a pronounced slowdown of the rotational dynamics of the constituent molecules due to a change in the molecular packing between the bulk and the confined liquid, OTP displays a linear and confining-media-dependent depression of Tg with increased confinement that is strongly influenced by the pore-liquid interface characteristics.This Account concludes with a focus on recent experimental evidence of extreme spatial and dynamical heterogeneity in both freezing and glass transition processes. This discovery was enabled by the unique mesoporous structures of SBA-16 and FDU-5, possessing bimodal architectures with two interconnected pore types of different size and shape (spherical and cylindrical). For the very first time, two melting points for water and two glass transitions for supercooled OTP, corresponding to a specific pore type, were observed. Collectively, these observations strongly suggest a close mechanistic connection between the local fluctuations in the structure and dynamics of nanoconfined liquids. While the findings reviewed in this Account provide new insights into thermodynamic and kinetic transitions of fluids, there remain many unanswered questions regarding the effects of nanoconfinement on the fundamental properties of fluids, which offer exciting future opportunities in chemical research.

Molecular Interactions of Poly (methylmethacrylate), Poly (vinyl alcohol), Poly(ethylene glycol), Chitosan, Cellulose and Starch Polymers with Iodine

The interactions betweenpoly(methylmethacrylate)(PMMA),poly(vinylalcohol) (PVA) poly(ethyleneglycol)(PEG)as industrial biopolymers andchitosan, cellulose, starch as natural biopolymers with iodine(I2)were investigated using diethyl ether as a solvent. 5% of I2 was added to each polymer and soaked in thesolvent. The interactions were investigated using concepts of the activation energy(Ea), Decisivefactor (Df)and the changing in the glass transition temperature (?Tg,s). Therefore, the differential scanning calorimeter(DSC) was used to monitorthe thermal transitions. The optical microscope(OM) device was used to studythe surface morphologies.Resultsshowed a clear depression in the glass transition temperatures (Tg,s) for allpolymers( as well as new colors appear) except cellulose still unaffected .It appears that cellulose moleculescoated with a film prevent iodine to diffuse through the network structure of cellulose thus no effected itscolor or its Tg which indicates that molecular structure of cellulose quite different from that of starch and forthis fact cellulose not soluble by a solvent and undigested in the human body. The depression inTg valuesof polymers indicate that iodine ruptures the engineering bonds of the polymers. The most effected Tg is ofchitosan (lowered by 40.23?C, this mean that iodine ruptures both hydrogen bonding through nitrogen andoxygen atoms in chitosan molecule.From Tg values, it seems that iodine can acts as moderate plasticizer, by diffusing through the net of syntheticand natural biopolymers ruptures their secondary bonds result in depression of their Tg except in case ofcellulose.The order of Tg depression is:Chitosan (40.23)>PMMA (27.89)>starch (22.29)>PVA (13.89) >PEG (5.78)>cellulose (0)Which showed no distinguish between natural and synthetic biopolymers.From Tg values calculation of the energy given by the addition of iodine to the polymers was done andshown the following order:chitosan(27.394)>PMMA(18.442) =starch(18.414)>PVA(9.316 )>PEG(4.315)>cellulose( 0 )

Characterizing moisture uptake and plasticization effects of water on amorphous amylose starch models using molecular dynamics methods

Dynamics and thermophysical properties of amorphous starch were explored using molecular dynamics (MD) simulations. Using the OPLS3e force field, simulations of short amylose chains in water were performed to determine force field accuracy. Using well-tempered metadynamics, a free energy map of the two glycosidic angles of an amylose molecule was constructed and compared with other modern force fields. Good agreement of torsional sampling for both solvated and amorphous amylose starch models was observed. Using combined grand canonical Monte Carlo (GCMC)/MD simulations, a moisture sorption isotherm curve is predicted along with temperature dependence. Concentration-dependent activation energies for water transport agree quantitatively with previous experiments. Finally, the plasticization effect of moisture content on amorphous starch was investigated. Predicted glass transition temperature (Tg) depression as a function of moisture content is in line with experimental trends. Further, our calculations provide a value for the dry Tg for amorphous starch, a value which no experimental value is available.

Thermal characteristics and flame retardance behavior of phosphoric acid-containing poly(methacrylates) synthesized by RAFT polymerization

The RAFT polymerization of strongly acidic, cross-linkable ethylene glycol methacrylate phosphate (EGMP) is described without protecting the acidic groups, with applications towards fire retardant polymers. After achieving the optimized polymerization conditions, we synthesized organo-soluble phosphoric acid-containing copolymers with methyl methacrylate (MMA) and bio-based isobornyl methacrylate (IBMA) with Mn in the range of 7.2−9.5 kg mol−1 and relatively low dispersities of 1.40−1.55. Additionally, we showed that it was possible to reinitiate RAFT polymerization from a P(EGMP)-rich macro-chain transfer agent with MMA and IBMA. DSC revealed Tg depression of copolymers as a function of EGMP concentration, which shows the plasticizing effect of EGMP. Rheology revealed cross-liking behavior of HEMAP-rich samples at 120 ℃. Thermogravimetric analysis (TGA) showed a one-step decomposition for PMMA and a two-step decomposition for PIBMA copolymers. In addition, the incorporation of 28 mol% EGMP slowed down the decomposition rate, improved the decomposition temperature (Td) by 41 ℃, and notably increased the limiting oxygen index (LOI) from ∼17.6 to over 24. Among all samples, the EGMP-rich polymer (FEGMP = 0.71, FMMA = 0.29) exhibited prominent flame retardancy with the highest LOI value of 34. This result is invariably due to the strong acidity of phosphoric acid groups which notably leads to interesting flame retardancy properties.

The Effect of Extender Particle Size on the Glass Transition Temperature of Model Epoxy Coatings.

Inorganic extenders are important constituents of 2K thermosetting epoxy-amine coatings and their physical properties play an important role in the final properties of the organic coatings. The effects of extender particle size and loading (i.e., the amount of extender in component A or in the total formulation) on the glass transition temperature (Tg) of model epoxy-amine coatings were studied in this work with differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA). The obtained results show that the particle size and loading of feldspar particles (from 25 wt% to 70 wt%) do not influence the glass transition temperature of the model epoxy-amine coating significantly. In general, the smaller the particle size the lower the glass transition temperature of the coating but this depression in Tg seems negligible when seen relative to the change in extender particle size. Similar observations are reported for two model coatings having the same lamda (Λ) value but with silica of very different particle sizes (i.e., nanosilica and micron sized silica).

Internal plasticization of poly(vinyl) chloride using glutamic acid as a branched linker to incorporate four plasticizers per anchor point

ABSTRACTInternal plasticization of polyvinyl chloride (PVC) using thermal azide‐alkyne Huisgen dipolar cycloaddition between azidized PVC and electron‐poor acetylenediamides incorporating a branched glutamic acid linker resulted in incorporation of four plasticizing moieties per attachment point on the polymer chain. A systematic study incorporating either alkyl or polyethylene glycol esters provided materials with varying degrees of plasticization, with depressed Tg values ranging from −1 °C to 62 °C. Three interesting trends were observed. First, Tg values of PVC bearing various internal plasticizers were shown to decrease with increasing chain length of the plasticizing ester. Second, branched internal plasticizers bearing triethylene glycol chains had lower Tg values compared to those with similar length long‐chain alkyl groups. Finally, thermogravimetric analysis of these internally plasticized PVC samples revealed that these branched internal plasticizers bearing alkyl chains are more thermally stable than similarity branched plasticizers bearing triethylene glycol units. These internal tetra‐plasticizers were synthesized and attached to PVC‐azide in three simple synthetic steps. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019, 57, 1821–1835

Polymer-Polymer Interfacial Perturbation on the Glass Transition of Supported Low Molecular Weight Polystyrene Thin Films.

Clarifying interfacial perturbation on polymer relaxation is important for polymer material development. Herein we investigated polymer-polymer interfacial perturbation on low molecular weight (MW) polystyrene (PS) thin film (15-180 nm) glass transition by depositing various polymers atop PS films. Overall, rubbery topcoats induced Tg depression of PS thin film (below 60 nm), whileglassy topcoats induced Tg elevation of PS thin film (below 30 nm). Importantly, for the rubbery topcoat, Tg perturbation strength is largely dependent on the Tg difference between interfacial polymers and a larger Tg difference would induce stronger perturbation, while for the glassy topcoat this dependence is inconspicuous. Meanwhile, the interfacial perturbation length during PS glass transition by rubbery topcoats is estimated to be around 8 nm, while it is considered to be about 3.5 nm for glassy topcoats. The different interfacial perturbation length induced by disparate topcoats was accounted for by their different perturbation strength on adjacent PS molecules and disparate interfacial roughness. The results can promote the understanding of polymer interfacial perturbation and benefit the design and development of polymer-based materials.

Raising glass transition temperature of polymer nanofilms as a function of negative interface energy.

Based on a thermodynamic approach, glass transition temperature (Tg) of substrate-supported polymer nanofilms (s-PNFs) is investigated for carbon-chain polymers, taking the role of the interface energy into consideration. Relative to the Tg depression, originating from the positive interface energy due to the weak interfacial van der Waals interactions, the Tg raise is reversely induced by the negative interface energy, induced by the hydrogen bonds formed between the side-chains of polymers and the surface hydroxyl groups of substrates. Moreover, the Tg raise can be reinforced for s-PNFs with simple side-chains. The model predictions agree well with available experimental or simulation results.

Foaming of polystyrene and poly(methyl methacrylate) multilayered thin films with supercritical carbon dioxide

A multilayer film consisting of 32 alternating layers of poly(methyl methacrylate) (PMMA) and polystyrene (PS) produced by forced assembly multiplying co-extrusion has been foamed using supercritical CO2 as a physical blowing agent. Foamability was first assessed by foaming under an induced temperature gradient. Foams were then generated under isothermal conditions at 60, 70, 80, and 90 ⁰C and 100, 200, and 300 bar using a special mold. PMMA layers were found to foam at 60, 70, 80, and 90 ⁰C while PS layers displayed porous morphology only in foams generated at 80 and 90 ⁰C. The films were observed to display delamination during foaming which became more severe in foams generated from higher temperatures with longer saturation times. Preferential foaming in the PMMA over the PS layers is discussed and is linked to the differences in the CO2 sorption and the depression of Tg in the respective polymers.

Novel Orally Disintegrating Tablets Produced Using a High-Pressure Carbon Dioxides Process.

It is well known that high-pressure carbon dioxide (CO2) lowers the glass transition temperature (Tg) of polymers. We therefore investigated whether Tg depression of high-pressure CO2 results in interparticle bridging of a polymer and the tablet characteristics that makes the manufacture of an orally disintegrating tablet (ODT) possible. Copolyvidone (Kollidon®) and polyvinyl caprolactam-polyvinyl acetate-polyethylene glycol graft copolymer (Soluplus®) were examined and found to exhibit a large Tg depression. Placebo ODTs were prepared and hardness, disintegration rate, porosity, and change in thickness and appearance were evaluated before and after the high-pressure CO2 treatment. This enabled the establishment of the optimal conditions for pressure, temperature, and treatment time under pressure. Experimental results showed that it was possible to manufacture ODTs comprising Kollidon® as a water-soluble polymer with CO2 treatment under the suitable conditions such as temperature at 45°C, pressure lower than 8 MPa, and a treatment time shorter than 30 min, which is a new ODT manufacturing process called "Carbon Dioxide Assisted Tablet Formation Scheme" (CATS). In comparison to the conventional processes, which require high temperatures or humidity, CATS is expected to be applicable to drugs that are unstable at high temperature and humidity, and to functional drug particles used for bitter taste masking, sustained release, and other uses.

Effect of Aspect Ratio on Electrical, Rheological and Glass Transition Properties of PC/MWCNT Nanocomposites.

Since the discovery of carbon nanotubes (CNT), significant research works have focused on the application of CNT as conductive filler to polymer nanocomposites which can be used in several fields such as electrostatic dissipation (ESD), electrostatic painting and electromagnetic interference shielding (EMI-shielding). However, the main challenge in the large-scale manufacturing of this technology is the poor electrical conductivity of polymer nanocomposites produced by injection molding process. This study aims to investigate the effect of CNT aspect ratio in improving the electrical conductivity of injection molded nanocomposites. In this work, three types of multiwall carbon nanotubes with different lengths were melt-mixed with polycarbonate in a twin screw extruder followed by injection and compression molding. Results show that nanocomposites with higher CNT aspect ratio exhibit higher electrical conductivity. Longer nanotubes form a stronger conductive network during secondary agglomeration which can withstand the high shear forces during injection molding. Higher melt viscosity and storage modulus were observed in nanocomposites with higher CNT aspect ratio which is attributed to the effective constriction of polymer chains by longer nanotubes. It was also found that Tg of the composites increased with nanotube aspect ratio and the addition of CNT causes degradation which leads to the general Tg depression of polycarbonate.