Onset Degradation Temperature Research Articles

Effects of high‐temperature optimization and resin coating treatment on the mechanical, thermal, and morphological properties of natural kenaf fiber‐filled engineering plastic composites

AbstractIn this study, kenaf natural fibers were coated with acetone‐thinned epoxy resin before compounding with high‐temperature polyethylene terephthalate (PET). Thus, composites of sodium hydroxide treated and epoxy‐resin coated kenaf fibers (KF) reinforced PET (CTKF‐PET) were manufactured using extrusion and compression molding techniques at an optimized 10 wt% constant fiber loading and processing temperatures of 240, 250, and 260°C, and were characterized for mechanical, thermal, and morphological performances. The obtained results showed an optimum processing temperature of 240°C with maximum mechanical and thermal properties with good interfaces between the coated fillers and the matrix, compared to those obtained at 250 and 260°C. Thermogravimetric analysis recorded maximum onset degradation and decomposition temperatures of 338.9 and 381°C with 9.5% and 13% improvements respectively after resin coating which positively impacted the constituent coated composites compared to the uncoated KF. Differential scanning calorimetry glass transition (Tg) and melting temperatures (Tm) for the CKF‐PET composites was maximum at 119.0 and 262.8°C with 2.18% and 2.8% improvements respectively compared to uncoated composites. The overall properties of all coated kenaf‐reinforced PET (CKF‐PET) and coated‐treated (CTKF‐PET) composites were higher with improved morphological properties irrespective of the processing temperature compared to the raw kenaf (KF‐PET) composites. Hence, natural fibers can be treated with resin coating to improve the thermal stabilities of natural fiber engineering plastic composites, and the interfacial adhesion between the coated‐KF and the engineering plastic matrix. The resultant composites are suitable for high‐temperature engineering applications such as the automotive and construction industries.

Effect of reprocessing on the service life properties of glass fiber-reinforced in-house polypropylene waste composites

Reprocessing of synthetic fiber-reinforced thermoplastics for reuse in the design of structural components applications is important owing to their non-biodegradability. This study evaluates the effect of reprocessing on the service life properties of in-house polypropylene wastes reinforced with E-glass fiber. Composite materials containing 10 mm length glass fiber (GF) and recycled polypropylene were manufactured with 10 wt% GF and subjected to five reprocessing cycles via extrusion and compression molding under similar conditions. Properties such as mechanical, melt flow index (MFI), thermogravimetric analysis (TGA), Fourier transform infrared (FTIR) spectroscopy, x-ray diffraction (XRD), and scanning electron microscopy (SEM) analysis were used to analyze the effect of reprocessing on the composites. The results obtained revealed that the composites’ properties diminished with successive reprocessing. The thermal study showed reductions in the thermal stabilities with a drop in onset degradation temperature from 338.07 to 245.15 °C after five runs, indicating an increase in the polymer chain molecular movement and less rigidity due to shorter chains provided by X-ray diffraction analysis with reduced peak intensities, average crystallite sizes, and degree of crystallinities but no destruction of the main functional groups was observed with the spectral studies. An increase in the MFI (6 g/10–17.88 g/10 min) indicated the possible loss of complex viscosity and damage in molecular weight for the reprocessed matrix. Reinforced in-house PP plastics can, therefore, be reprocessed twice only for the same product except with the addition of either virgin PP or other materials to compensate for the lost properties and help manufacturers save costs.

Effect of glass fiber loading and reprocessing cycles on the mechanical, thermal, and morphological properties of isotactic polypropylene composites

AbstractIn this study, a preliminary finding is carried out to obtain the optimum E‐glass fiber content in polypropylene (PP) plastic products using loadings of 5, 10, 20, 30, and 40 wt%. The formulation with the optimum loading of 10 wt% glass fiber was reprocessed 10 times via extrusion and compression molding techniques to simulate actual recycling and impacts on service life properties such as mechanical, toughness, chemical, thermal, composition, and morphology. In the result, mechanical properties were lost after each reprocessing without effect on the chemical properties and elemental compositions. The thermal studies showed a decrease in degradation temperatures with the onset degradation temperature (TOnset) for the one‐time reprocessed PP recorded at 336.93°C with a maximum rate of weight loss (TMax) at 427.68°C which further reduced to 259.90°C (TMax of 388.47°C) after 10 extrusion run showing one‐step decomposition patterns. This work provides that glass fiber‐reinforced plastics should not be reprocessed beyond 3 times except when refreshed with the addition of virgin PP to make up for the lost property. This will be very useful for manufacturers who want to simultaneously save costs (retain profit margin) and maintain the environment.

Thermogravimetric analysis for the characterization and comparative analysis of polyvinyl chloride (PVC) wall panel

In this paper, thermogravimetric analysis of different types/grades of polyvinyl chloride (PVC) wall panel is carried out using thermogravimetric analyzer. The data output from the analyzer is subjected to data analysis software i.e., OriginPro 2018, from which thermal attributes are find out for different grades of PVC wall panel i.e., soft PVC, hard PVC, WPVC and SPVC. The thermogravimetric attributes i.e., onset degradation temperature Ti, final degradation temperature Tf,, reaction interval and the peak temperature TP from the derivative thermogravimetric curve for the four basic types of PVC were comparatively analyzed for the characterization purpose. Beside the thermal characterization, the thermogravimetric analysis also disclosed the compositional attributes of the four types of PVC wall panel. The analysis in this paper characterized the SPVC as the most thermally stable PVC wall panel followed by hard, soft and WPVC.

Polypropylene and Graphene Nanocomposites: Effects of Selected 2D-Nanofiller’s Plate Sizes on Fundamental Physicochemical Properties

The authors developed a nanocomposite using polypropylene (PP) and graphene nanoplatelets (GNPs) with a melt mixing method. Virgin PP was filled with three sets of GNPs with a fixed thickness (15 nm) and surface area (50–80 m2/g). The selected H-type GNPs had three different sizes of 5, 15 and 25 µm. The nanocomposites were made by loading GNPs at 1, 2 and 3 wt.%. Mechanical analysis was carried out by performing tensile, flexural and impact strength tests. The crystalline, micro-structural, thermal and dynamic mechanical properties were assessed through XRD, FESEM, PLM, DSC, TGA and DMA tests. It was observed that all three types of GNPs boosted the mechanical strength of the polymer composite. Increasing the nanofiller size decreased the tensile strength and the tensile modulus, increased the flexural strength and flexural modulus, and increased the impact strength. Maximum tensile strength (≈41.18 MPa) resulted for the composite consisting 3 wt.% H5, whereas maximum flexural (≈50.931 MPa) and impact (≈42.88 J/m) strengths were observed for nanocomposite holding 3 wt.% H25. Graphene induced the PP’s crystalline phases and structure. An improvement in thermal stability was seen based on the results of onset degradation (TD) and melting (Tm) temperatures. Graphene increased the crystallization (Tc) temperatures, and acted like a nucleating agent. The experimental analysis indicated that the lateral size of graphene plays an important role for the nanocomposite’s homogeneity. It was noted that the small-sized GNPs improved dispersion and decreased agglomeration. Thus overall, small-sized GNPs are preferable, and increasing the lateral size hardly establishes feasible characteristics in the nanocomposite.

Thermomechanical and Pre-Ignition Properties of Multicomponent Poly(Vnylidene Fluoride)/Aluminum Oxide/Single-Walled Carbon Nanotube Hybrid Nanocomposites

Poly(vinylidene fluoride), PVDF is a piezoelectric semi-crystalline fluoroplastic that is widely used in the electronics and semiconductor industry for packaging, sensors, and actuators. PVDF nanocomposites containing single-walled carbon nanotubes, SWCNTs and fumed alumina, Al2O3 were prepared in dimethylformamide, and their thermal and dynamic mechanical properties were determined by using thermogravimetric analysis, TGA, differential scanning calorimetry, DSC and dynamic mechanical analysis, DMA. It was observed from differential scanning calorimetry that the matrix’s degree of crystallinity and enthalpy of melting was reduced in the presence of the nanofillers to about 7.1%, compared to the neat PVDF whose degree of crystallinity was determined to be about 51.3%. The melting temperature, Tm obtained by DSC measurements was also reduced from 171.6 °C to 162.7 °C at high SWCNT loadings. The onset degradation temperature was also lowered in the presence of the nanofillers, especially alumina particulates. Dynamic mechanical analysis of the composites showed a significant improvement in the storage modulus of about 18 GPa in the presence of SWCNT. The glass transition temperature, Tg was significantly increased from −42.6 °C to −33.2 °C due to reinforcement with SWCNT. The reinforcement of PVDF with SWCNT and alumina resulted in greater char retention at 600 °C.

Tetraphenylsilane-based oligo(azomethine)s containing 3,4-ethylenedioxythiophene units along their backbone: Optical, electronic, thermal properties and computational simulations

A series of three new oligo-poly(azomethine)s (o-PAzMs) were successfully synthesized, incorporating tetraphenylsilane (TPS) and 3,4-ethylenedioxythiophene (EDOT) moieties with Mn and Mw between 3.9 and 5.4 kDa and 8.3–11.6 kDa, respectively. The silylated o-PAzMs were highly soluble in low-boiling point solvents such as CHCl3, THF, and CH2Cl2. All three materials are highly thermally stable, with onset temperatures of degradation of at least 250 °C and with TDT10% between 340 and 460 °C. The glass transition temperature values agree with the flexibility of the repetitive units and showed values between 125 and 155 °C. The absorption and emission of the o-PAzMs were observed in the blue-violet UV–vis region (350–550 nm) with moderate Stokes shifts (48–71 nm). The oligomers are π-conjugated wide-band gap materials (2.83–2.73 eV), where the high electronic transitions would be associated with disruption of π-conjugation, which is promoted by the TPS core and (d-p)π orbital interactions. This disruption controls the effect from the EDOT unit rich donor on HOMO (−5.79 eV to −5.71 eV) and LUMO (−2.98 eV to −2.89 eV) energy values. Furthermore, DFT and TDDFT calculations were performed to theoretically characterize the observed UV–Vis transitions and frontier molecular orbitals (MOs) energies.

Effect of cross‐linking on the mechanical properties, degree of crystallinity and thermal stability of polyethylene vitrimers

AbstractMaleic anhydride‐grafted‐polyethylene was dynamically cross‐linked via reactive melt blending with 4,4′‐dithiodianiline. Thermal and mechanical properties of polyethylene vitrimers with different cross‐linking density were investigated. The results indicate that the degree of crystallinity decreased with increasing cross‐linking density. This behavior was directly related to short‐term and long‐term mechanical properties: vitrimers showed a decrease in yield strength and creep performance. The yield strength of PE vitrimers decreased linearly in relation to the degree of crystallinity. Polarized optical microscopy revealed that the cross‐links inhibit the growth of spherulites structure in polyethylene vitrimers. Thermogravimetric analysis indicated an increase in the onset degradation temperature and decomposition rate for vitrimers with increased cross‐linking density. The stiffness of the vitrimers decreased with increasing cross‐linking density which led to higher damping properties. Finally, it was demonstrated that reprocessing of polyethylene vitrimer was possible without significant impact in mechanical properties.

Recycled Multi-Material Packaging Reinforced with Flax Fibres: Thermal and Mechanical Behaviour.

In this work, the use of a recycled mix stemming from the treatment of multilayer aseptic packaging used in the food and beverage industry is proposed as the matrix for short fibre composites reinforced with flax fibres, to generate value-added materials in contrast to the more common end-of-life scenario including energy recovery. This is expected to be a preferred choice in the waste hierarchy at the European level. A commercially available material (EcoAllene) obtained from multilayer packaging recycling was compounded with short flax fibres up to 30 wt.% by twin screw extrusion, with a view to enhancing its poor mechanical profile and broadening its applications. Composites were in depth analyzed by thermogravimetric analysis and differential scanning calorimetry, which highlighted the complex nature of this recycled product, a limited nucleation ability of flax fibres and a lower thermal stability due to the premature degradation of natural hemicellulose and cellulose, though featuring in any case onset degradation temperatures higher than 300 °C. Composites’ mechanical properties were assessed in tension, bending and impact conditions, with remarkable improvements over the neat matrix in terms of stiffness and strength. In particular, at 30 wt.% fibre content and with 5 wt.% of maleated coupling agent, an increase in tensile and flexural strength values by 92% and 138% was achieved, respectively, without compromising the impact strength. The effectiveness of flax fibres confirmed by dynamo-mechanical analysis is beneficial to the exploitation of these composites in automotive interiors and outdoor decking applications.

Estimation of rheological percolation threshold and influence of fibre length on properties of polypropylene/sisal fibre composites having near critical fibre length

In this paper, the rheological percolation threshold and the hardness of Polypropylene/Sisal fibre (PP/SF) composites were correlated. Power law fit was implemented for the estimation of rheological percolation threshold. Further, the performance properties of PP/SF composites having near-critical length fibre (NCLF) and short fibre were investigated in terms of thermomechanical, rheological, and dynamic mechanical parameters. The Shore D hardness data revealed that the rheological percolation threshold of the prepared composites remained in the range of 20–30 wt% of sisal fibre. Moreover, sisal fibre had an undeniable impact on the dynamic mechanical properties of the prepared composites. Further, the rise in the onset degradation temperature by 40 °C proved the improvement in thermal stability of the prepared composites. It was also found that PP/SF composite having 20 wt% of near critical length fibre had properties equivalent to that of PP/SF composite having 40 wt% of short fibre (fibre length less then critical fibre length). • Correlation between Rheological Percolation threshold and Shore D hardness. • PP/SF composites having near critical length fibres. • Effect of fibre length on performance properties of PP/SF composites.

Effect of zirconia nanoparticles modified by silane coupling agent on some properties of epoxy coating

Effect of zirconia nanoparticles (zirconia NPs/ZrO2 NPs) modified by 3 wt.% (glycidyloxypropyl) triethoxysilane – GPTES (m-ZrO2 NPs) on some properties of epoxy coating such as mechanical properties, thermal stability and anti-corrosion performance was investigated. The obtained results indicated that the addition of zirconia nanoparticles to epoxy coating could enhance the properties of this coating. The addition of 2 wt.% of pure ZrO2 NPs (u-ZrO2 NPs) to the epoxy matrix could increase the mechanical properties (hardness and adhesion to the steel substrate) by approximately 10 %, the onset temperature of thermal degradation of the epoxy/u-ZrO2 NPs coating was 4.4 oC higher, and the anti-corrosion performance of epoxy coating was improved in comparison with the neat epoxy coating. Organically modified ZrO2 NPs had higher improvement for epoxy coating’s properties than pure ZrO2 NPs. The epoxy coating filled with m-ZrO2 NPs had 19.7 % higher in relative hardness, 88.73 % more in adhesion to steel substrate, 25.6 oC higher in the onset temperature of thermal degradation, and higher anti-corrosion performance in comparison with the epoxy coating filled with 2 wt.% of pure zirconia nanoparticles. The cross-section FESEM images of the epoxy/m-ZrO2 NPs coating showed that m-ZrO2 NPs could regularly disperse in epoxy polymer matrix while unmodified zirconia nanoparticles (u-ZrO2 NPs) were agglomerated to big cluster in the epoxy coating. This was the reason for the high performance of the epoxy coating filled with zirconia NPs modified by GPTES.

Biodegradable PLA-based Biocomposites with Spent Coffee Grounds as Degradation Accelerator : Hydrolytic Degradation and Characterization Research

The goal of this study was to evaluate the effect of spent coffee grounds (SCG) biofiller on the morphological, thermal, mechanical and hydrolytic degradation characteristics of poly(lactic acid) (PLA) based biocomposites. The PLA-based biocomposite films were fabricated by using a high-viscosity kneading and hot-pressing machine. The PLA/SCG biocomposites were analyzed with SEM, DSC, TGA, UTM and hydrolytic degradation test. Aggregation in the PLA matrix is a result of increasing SCG concentrations. In the thermal properties, it was described that the cold crystallization temperature (Tcc) decreased as SCG was added to PLA. When SCG was incorporated to PLA, the degradation onset temperature (Tonset) revealed a diminish. The elastic modulus increased while tensile strength of PLA diminished as SCG was applied. Through hydrolysis analysis, the decomposition of PLA was accelerated with the addition of SCG. This research confirmed the possibility of devloping an eco-friendly packaging material with high degradability as SCG hasten the breakdown of PLA.

Polyvinylidene fluoride‐poly(vinyl acetate)‐natural graphite blend nanocomposites: Investigations of electroactive phase formation, electrical, thermal, and wetting properties

AbstractSolution blended polyvinylidene fluoride (PVDF)‐20 wt% poly(vinyl acetate) (PVAc)‐natural graphite (NtGr) blend nanocomposites exhibit a very low electrical percolation threshold of less than 0.5 wt% NtGr due to the formation of graphite nanosheets. The electroactive gamma phase induced with and without NtGr in PVDF‐20 wt% PVAc blend film is confirmed by X‐ray diffraction, fourier transform infrared spectroscopy, and differential scanning calorimetry analyzes. The onset degradation temperature corresponding to PVDF in PVDF‐20 wt% PVAc blend nanocomposites is increased by 27°C when 1 wt% NtGr is incorporated into the blend, suggesting enhanced thermal stability of blend nanocomposites. Due to an increase in surface roughness of PVDF‐20 wt% PVAc‐3 wt% NtGr as evidence by field emission scanning electron microscopy analysis, the water contact angle increases to 141.6° from 83.44° for PVDF‐20 wt% PVAc blend. AC conductivity analysis suggests hopping conduction in PVDF‐20 wt% PVAc‐x wt% NtGr (x = 1, 3, 5) blend nanocomposites. The interjunction capacitance increases with graphite loading in the blend.

Polyvinylidene fluoride‐natural graphite flexible composite films: Formation of graphite nanosheets, electroactive phase, analysis of electrical and thermal properties

AbstractSolution blending technique has been employed to synthesize polyvinylidene fluoride (PVDF)‐natural graphite composite films. The surface tension of the solvent has been observed to play an important role in the reduction of graphite particle size and their dispersion in the polymer matrix as N‐N‐dimethylacetamide (DMAc) employed PVDF‐x wt% natural graphite (x = 3, 5) films exhibit higher conductivity than that of N‐N‐dimethylformamide (DMF) employed films of same composition. The dispersion of probe sonicated graphite particles in PVDF matrix has been observed to be better when DMAc solvent is used in comparison to DMF employed composite as revealed by optical microscope images. The electrical percolation threshold in PVDF‐natural graphite composites is identified below 0.5 wt% natural graphite due to remarkable reduction in the particle size of graphite which improved the network formation between them. FESEM analysis confirms the formation of graphite nanosheets. The coexistence of non‐polar α and electroactive γ phases of PVDF in the composites is confirmed by FTIR, XRD, and DSC analyses. Maximum fraction of γ phase, as calculated from FTIR, is 88% in PVDF‐3 wt% natural graphite composite. Thermal annealing of PVDF‐3 wt% natural graphite at 120°C for 5 h results in enhanced electroactive γ phase in the nanocomposite. The onset degradation temperature of PVDF is increased by 4°C in PVDF‐5 wt% natural graphite suggesting enhanced thermal stability of the composite. Room temperature I–V characteristics of PVDF‐x wt% natural graphite (x = 5, 7) composite supports space charge limited conduction to be the dominant mechanism of charge transport.

A promising antimicrobial bionanocomposite based poly(3-hydroxybutyrate-co-3-hydroxyvalerate) reinforced silver doped zinc oxide nanoparticles

A bionanocomposite based on biosynthesized poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) and reinforced with silver@zinc oxide (Ag–ZnO) was synthesized in variable loadings of Ag–ZnO using the in-situ casting dissolution technique. The degradable biopolymer PHBV had been biosynthesized from date waste as a renewable carbon source. The fabricated products were investigated as promising antibacterial materials. The Ag–ZnO nanoparticles were also synthesized using the green method in the presence of Gum Arabic. The Ag–ZnO nanoparticles were loaded within the PHBV biopolymer backbone at concentration of 1%, 3%, 5% and 10%, PHBV/Ag–ZnO(1,3,5,10%). The chemical structure, morphology, physical and thermal properties of the PHBV/Ag–ZnO bionanocomposites were assessed via common characterization tools of FTIR, TGA, XRD, SEM and EDX. One step of the degradation process was observed in the range of 200–220 °C for all the obtained materials. The onset degradation temperature of the bionanocomposites have been noticeably increased with increasing the nanofiller loading percentage. In addition, fabricated products were investigated for their interesting antibacterial performance. A detailed biological screening for the obtained products was confirmed against some selected Gram-positive and Gram-negative strains S. aureus and E. coli, respectively. Overall, the bionanocomposite PHBV/Ag–ZnO(10%) was the most potent against both types of the selected bacteria. The order of bacterial growth inhibition on the surface of the fabricated bionanocomposites was detected as follows: PHBV/Ag–ZnO(10%) > PHBV/Ag–ZnO(5%) > PHBV/Ag–ZnO(3%) > PHBV/Ag–ZnO(1%).

A Comparative Study on the Addition of MgO and Mg(OH)2 Nanoparticles into PCL Electrospun Fibers

AbstractIn this work, a comparative study between the morphology, the thermal and the mechanical properties of poly(ɛ‐caprolactone) (PCL)‐based electrospun fiber mats reinforced with both MgO and Mg(OH)2 nanoparticles, is carried out. Both MgO and Mg(OH)2 nanoparticles have been added in a range of concentrations such as 0.5, 1, 5, 10, 20 wt% with respect to the PCL matrix, with the aim of improving their mechanical properties in comparison with neat PCL electrospun fibers. From the morphological point of view, electrospun fibers are randomly collected and an increase in the average fiber diameter with the addition of nanoparticles is observed. The addition of both types of nanoparticles lower the onset degradation temperature as well as the maximum degradation temperature of neat ePCL of about 50 °C with the higher content of nanoparticles. Furthermore, PCL electrospun nanofiber mats show a degree of crystallinity of 53%, which is quite high. However, the addition of 20 wt% of both MgO and Mg(OH)2 lowers the crystallinity of the reinforced electrospun fibers to 50% and 43% for PCL + MgO 20 wt% and Mg(OH)2 20 wt%, respectively.

Assessment of curcumin incorporated chickpea flour/PEO (polyethylene oxide) based electrospun nanofiber as an antioxidant and antimicrobial food package

This study aimed to obtain curcumin encapsulated nanofibers as a potential food package and analyze physical properties and functional attributes, including antioxidant and antimicrobial activities. Due to their non-toxic and biodegradable characteristics, chickpea flour/PEO were used as an external support matrix for curcumin. In this context, the effects of curcumin and heating methods (conventional and microwave) on solution and film properties were investigated. The SEM (Scanning Electron Microscope) images showed that the fiber morphology of the microwave-treated samples was as smooth as those of conventionally-treated ones. Neither the addition of curcumin nor the different heat treatments had any significant impact on the water vapor permeability of the samples. However, the addition of curcumin shifted the onset degradation temperatures of the samples (T5%) by nearly 20 °C. Both the DPPH (2,2-Diphenyl-1-picrylhydrazyl) and ABTS (2,2′-Azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt) scavenging activities of the curcumin-containing and microwave-treated (CUR/MW) samples were higher than those of the conventionally-treated (CUR/CON) samples. Although CUR/MW film had an antimicrobial effect on E.coli (ATCC 11229), it did not have any effect on S.aureus (ATCC 43300). Therefore, microwave heating could be preferred instead of conventional heating owing to the former’s time and energy efficiency characteristics and its higher level of contribution to film characteristics. It should also be noted that the addition of curcumin improved the functionality of the nanofiber films.

Effect of epoxy concentrations on thermo-mechanical properties of kenaf fiber – recycled poly (ethylene terephthalate) composites

The effect of different concentrations of epoxy surface coating treatment on the thermal and mechanical properties of kenaf fiber reinforced recycled poly (ethylene terephthalate) (RPET) composites was studied. Silane-treated kenaf fibers (SKF) were epoxy-coated with optimized coating concentrations (in the ratios of 1:4, 1:5, and 1:6 epoxy to acetone solutions) to improve the thermal degradation/decomposition resistance and interfacial bonding with RPET matrix. The different epoxy coated-silane treated kenaf fibers 1:4 ESKF, 1:5 ESKF, and 1:6 ESKF were compounded with RPET at an optimized temperature of 240°C, and their constituents’ composites KF/RPET, 1:4 ESKF/RPET, 1:5 ESKF/RPET, and 1:6 ESKF/RPET were subjected to thermal, mechanical and microstructural investigation. The obtained results showed some remarkable effects of epoxy concentrations on the chemical and surface structures of the treated fibers. Thermal properties of both ESKF and ESKF/RPET composites were more stable and improved with different concentrations of epoxy treatment compared to the untreated counterparts. 1:4 ESKF and 1:5 ESKF were the most thermally stable with onset degradation and DTG decomposition temperatures of 331.6°C and 381.7°C, and 324.0°C and 388.7°C respectively. Mechanical properties of the epoxy-coated composites were higher and further improved with epoxy concentrations and fiber loadings compared to uncoated composites. Hence, the epoxy concentration of 1:4 gave the maximum tensile and impact properties, and at 10 wt. % fiber loading within the lower loading regions, followed by 1:5 with outstanding flexural properties. The coated-treated composites showed strong fiber/matrix bonding with no evidence of fiber decomposition compared to the untreated composites with poor fiber/matrix interaction. The current research findings are original and valid for improving the thermal degradation resistance and stability of natural fibers, and the mechanical properties of natural fiber reinforced engineering thermoplastic composites. The epoxy coated – silane-treated textile kenaf fibers reinforced with recycled PET composites have the potentials to be utilized in high-temperature industrial and engineering applications.

Heat capacity and index of refraction of polyzwitterions

Specific heat capacities and indices of refraction were measured for a series of six sulfobetaine zwitterionic polymers and compared to topological and group contribution models. Poly(sulfobetaine methacrylate) (PSBMA), poly(sulfobetaine acrylate) (PSBA), poly(ethyl sulfobetaine methacrylate) (PESBMA), poly(sulfobetaine methacrylamide) (PSBMAm), poly(sulfobetaine 2-vinylpyridine) (PSB2VP) and poly(sulfobetaine 4-vinylpyridine) (PSB4VP) were specially synthesized with changes of chemical structure in order to study effects of either the polymer backbone or the side group on their properties. Temperature modulated differential scanning calorimetry (TMDSC) as well as quasi-isothermal TMDSC were used to determine the temperature dependent specific heat capacity, cp(T) from 30 to 200 °C. The solid state specific heat capacities were measured for all the polyzwitterions, while liquid state heat capacity measurements were limited to PSBA and PESBMA. Ellipsometry at wavelengths from 300 nm to 3000 nm was used to measure the index of refraction for polyzwitterion thin films at room temperature. Theoretical room temperature values of cp and n were calculated for the polyzwitterions using topological and group contribution methods and compared to the measured values. The measured index of refraction values agree well with predictions for the polyzwitterions. However, for the solid state heat capacity, the model produces accurate prediction only for PSB2VP and PSB4VP. The discrepancy between the measured and predicted cp values is most likely due to the reduction of vibrational degrees of motion in the solid state for some of the polyzwitterions due to physical crosslinking.

Performance of SiO2 Filled Functional Polypropylene Substrates for 5th Generation Communication

Three grades of functional polypropylene (FPP)/silica (SiO2) (FPPASP16 xSiO2 y, FPPASP17 xSiO2 y and FPPASP18 xSiO2 y) and their crosslinked FPP/SiO2 (CLFPPASP16 xSiO2 y, CLFPPASP17 xSiO2 y and CLFPPASP18 xSiO2 y) nanocomposites were satisfactorily made for applying as fifth generation (5 G) mobile communication substrates. Significantly smaller linear thermal expansion coefficient (LCTE) but larger dielectric constant (εr), dielectric loss (tan δ) and onset degradation temperature (DTonset) were acquired for CLFPPa xSiO2 y than those of the corresponding FPPa xSiO2 y sequence having identical SiO2 loadings. It is worth emphasizing that substantially smaller εr, tan δ and LCTE values were acquired for every FPPa xSiO2 y and CLFPPa xSiO2 y sequence filled with appropriate SiO2 loadings. Quite small εr/tan δ ( 2.41/0.00539, 2.36/0.00361, 2.53/0.00653, 2.52/0.00671, 2.46/0.00461 and 2.62/0.00821, all measured at 1 MHz) and LCTE (∼140 ppm/°C, 152 ppm/°C, 75 ppm/°C, 127 ppm/°C, 142 ppm/°C and 56 ppm/°C) values suitable for 5 G communication were acquired for FPPASP16 95SiO2 5, FPPASP17 94SiO2 6, FPPASP18 95SiO2 5, CLFPPASP16 95SiO2 5, CLFPPASP17 94SiO2 6 and CLFPPASP18 95SiO2 5 filled with optimum loadings of SiO2 nanoparticles, respectively. All free volume properties estimated for every FPPa xSiO2 y and CLFPPa xSiO2 y sequence enlarged to a largest value as the SiO2 loadings approached the corresponding optimum value. Possible reasons accounting for these substantially diminished dielectric and LCTE and improved thermal degradation properties of the FPPa xSiO2 y and CLFPPa xSiO2 y films are proposed.