Thermal and mechanical properties of compression‐molded pMDI‐reinforced PCL/gluten composites

Many biopolymers and synthetic polymers composites were developed by different researchers for environmental protection and for cost reduction. One of these composites is polycaprolactone (PCL) and vital wheat gluten or wheat flour composites were prepared and compatibilized with polymeric diphenylmethane diisocyanate (pMDI) by blending and compression‐molding. PCL/pMDI blend exhibited glass transition (T_g) at ?67°C (0.20 J/g/°C) and vital gluten at 63°C (0.45 J/g/°C), whereas no T_g was recorded for wheat flour. Although T_g was unmistakable for either PCL or gluten, all composite exhibited one T_g, which is strong indication of interaction between PCL and the fillers. Several samples amongst the blended or compression‐molded composites exhibited no T_g signifying another confirmation of interaction. The ΔH of the endothermic (melting) and the exothermic (crystallization) for PCL was decreased as the percentage of gluten or flour increased, whereas the overall ΔH was higher for all composites compared to the theoretical value. The presence of pMDI appeared to strengthen the mechanical properties of the composites by mostly interacting with the filler (gluten or flour) and not as much with PCL. The FTIR analysis ruled out covalent interaction between PCL, pMDI, or the fillers but suggested the occurrence of physical interactions. Based on the data presented here and the data published earlier, the presence of pMDI did not change the nature of interaction between PCL and gluten, but it improved the mechanical properties of the composite. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Microstructure determination and thermal studies of n‐acryloylcarbazole/vinyl acetate copolymers

Copolymers of N‐acryloylcarbazole (A) and vinyl acetate (V) were synthesized by bulk polymerization using benzoyl peroxide (BPO) as free‐radical initiator at 65°C in different in‐feed ratios. The composition of the copolymer was determined by ¹H‐NMR spectrum. The comonomer reactivity ratios, determined by Kelen–Tudos (KT) and nonlinear error‐in‐variables (EVM) methods, were r_A= 16.75 ± 1.38, r_V = 0.015 ± 0.002, and r_A = 16.36, r_V = 0.015, respectively. Complete spectral assignments of the ¹H and ¹³C{¹H} NMR spectra of the copolymers were done by the help of distortionless enhancement by polarization transfer (DEPT) and two‐dimensional NMR techniques such as heteronuclear single quantum coherence (HSQC) and total correlation spectroscopy (TOCSY). The methine and methylene carbon resonances were found to be compositional as well as configurational sensitive. The signals obtained were broad pertaining to the restricted rotation of bulky carbazole group. The thermal stability and glass‐transition temperatures (T_g) of the copolymers were found to be dependant on polymer composition and characteristic of rotational rigidity of the polymer chain. Variation in the values of T_g with the copolymer composition was found to be in good agreement with theoretical values obtained from Johnston and Barton equations. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 2720–2733, 2007     

Fabrication,characterization, and properties of poly(ethylene‐co‐vinyl acetate)/magnetite nanocomposites

Poly(ethylene‐co‐vinyl acetate) (EVA)/magnetite (Fe₃O₄) nanocomposite was prepared with different loading of Fe₃O₄ nanoparticles. The mixing and compounding were carried out on a two‐roll mixing mill and the sheets were prepared in a compression‐molding machine. The effect of loading of nanoparticles in EVA was investigated thoroughly by different characterization technique such as transmission electron microscopy (TEM), X‐ray diffraction (XRD), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), limiting oxygen index (LOI), and technological properties. TEM analysis showed the uniform dispersion of filler in the polymer matrix and the dispersion of filler decreased with increase in filler content. XRD of the nanocomposite revealed the more ordered structure of the polymer chain. An appreciable increase in glass transition temperature was observed owing to the restricted mobility of Fe₃O₄‐filled EVA nanocomposite. TGA and flame resistance studies indicated that the composites attain better thermal and flame resistance than EVA owing to the interaction of filler and polymer segments. Mechanical properties such as tensile strength, tear resistance, and modulus were increased for composites up to 7 phr of filler, which is presumably owing to aggregation of Fe₃O₄ nanoparticle at higher loading. The presence of Fe₃O₄ nanoparticles in the polymer matrix reduced the elongation at break and impact strength while improved hardness of the composite than unfilled EVA. The change in technological properties had been correlated with the variation of polymer–filler interaction estimated from the swelling behavior. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40116.     

Synthesis,characterizations, and mechanical properties of structurally modified poly(vinyl alcohol)

Poly(vinyl alcohol) (PVA) was structurally modified with two different types of chemicals under nitrogen atmosphere in the presence of Sb₂O₃ as a catalyst at 80°C in an aqueous medium. An FTIR and NMR spectrum confirmed the structural modification of PVA. DSC and TGA counseled the thermal properties of structurally modified PVA. Urea modified PVA exhibited higher mechanical strength than the pristine PVA. The FTIR‐relative intensities of olefin formation and ketone formation were increased with the increase of weight of water. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

A study of nano‐mechanical and macro‐mechanical properties of ethylene vinyl acetate

Nano‐ and macro‐mechanical properties of ethylene vinyl acetate (EVA) with various amounts of vinyl acetate (VA) have been investigated. Nano‐mechanical properties (modulus and hardness) were obtained using nano‐indentation measurements while macro‐mechanical properties were determined using tensile test measurements. A decrease in Young's modulus and hardness was observed with increasing VA content for both nano‐ and macro‐mechanical measurements. An increase in Young's modulus and hardness was observed as a function of the draw ratio keeping the VA content constant. The difference between macro‐ and nano‐mechanical properties as a function of VA content and draw ratio is explained in terms of crystallinity and chain orientation. POLYM. ENG. SCI., 2008. © 2007 Society of Plastics Engineers     

Influence of fumed silica on the flame‐retardant properties of ethylene vinyl acetate/aluminum hydroxide composites

The flammability and synergistic flame‐retardant effects of fumed silica (SiO₂) in ethylene vinyl acetate (EVA)/aluminum hydroxide (ATH) blends were studied with limiting oxygen index measurements, UL 94 testing, cone calorimeter testing (CONE), and thermogravimetric analysis (TGA). The results show that the addition of a given amount of fumed SiO₂ can apparently improve UL 94 rating. The CONE data indicated that the addition of fumed SiO₂ greatly reduced the heat release rate. The TGA data showed that this synergistic flame‐retardant mechanism of fumed SiO₂ in the EVA/ATH materials was mainly due to the physical process. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Thermal behavior of vinyl ester resin matrix composites reinforced with alkali‐treated jute fibers

The thermal behavior of vinyl ester resin matrix composites reinforced with jute fibers treated for 2, 4, 6, and 8 h with 5% NaOH was studied with Thermo‐gravimetric analysis and differential scanning calorimetry. The moisture desorption peak shifted to a higher temperature, from 37 to 58.3°C, for all the treated‐fiber composites because of improved wetting of the fibers by the resin and stronger bonding at the interface. The degradation temperature of the vinyl ester resin in the composites was lowered to 410.3°C from that of the neat resin, 418.8°C. The X‐ray diffraction studies showed increased crystallinity of the treated fibers, which affected the enthalpy of the α‐cellulose and hemicellulose degradation. The hemicellulose degradation temperature remained the same (299.7°C) in all the treated‐fiber composites, but the enthalpy associated with the hemicellulose degradation showed an increasing trend in the treated composites with a small increase in the weight loss. This could be attributed to the increased hydrogen bonding between the more accessible ? OH groups of the hemicellulose in the noncrystalline region of the jute fiber and the resin. The degradation temperature of α‐cellulose was lowered from 364.2 to 356.8°C in the treated composites. The enthalpy of α‐cellulose degradation showed a decreasing trend with a lowering of the weight loss. The crystalline regions of the fiber, consisting of closely packed α‐cellulose chains, were bonded with the resin mainly on the surface through hydrogen bonds and became more resistant to thermal degradation; this reduced the weight loss. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 123–129, 2004     

Effect of curing on the corrosion protective properties of thin organosilane films on aluminium

Film properties and corrosion protection given by thin organosilane films (bis-1,2-(triethoxysilyl)ethane: BTSE) on aluminium were investigated as a function of curing. The thickness was determined using spectroscopic ellipsometry (SE). Impedance spectra, modelled by an electrical equivalent circuit, show three time constants. The variation of the elements in these three time constants as a function of the immersion time in a NaCl solution indicate the structure of the film after curing. It can be concluded that the barrier properties of the organosilane films are influenced more by the curing temperature than by the curing time.     

Novel organic–inorganic hybrid coatings prepared by the sol–gel process: corrosion and mechanical properties

(Hyperbranched polyurethane‐urea)/[(3‐aminopropyl)triethoxysilane]‐ZnO (HBPUU‐APTES‐ZnO) hybrid coatings were synthesized using an inexpensive mixing technique by varying the APTES‐modified ZnO concentration. The mechanical and surface properties of the hybrid coating films were studied and compared with unmodified and modified ZnO. The corrosion, solvent and abrasion resistance show significant enhancement in HBPUU‐APTES‐ZnO hybrids and their properties are increased with increasing APTES‐ZnO concentration. This hybrid coating has opened up an opportunity for automotive topcoat application. Copyright © 2012 Society of Chemical Industry     

Effect of vinyl acetate content on the mechanical and thermal properties of ethylene vinyl acetate/MgAl layered double hydroxide nanocomposites

Ethylene vinyl acetate (EVA)/Mg‐Al layered double hydroxide (LDH) nanocomposites using EVA of different vinyl acetate contents (EVA‐18 and EVA‐45) have been prepared by solution blending method. X‐ray diffraction and transmission electron microscopic studies of nanocomposites clearly indicate the formation of exfoliated/intercalated structure for EVA‐18 and completely delaminated structure for EVA‐45. Though EVA‐18 nanocomposites do not show significant improvement in mechanical properties, EVA‐45 nanocomposites with 5 wt % DS‐LDH content results in tensile strength and elongation at break to be 25% and 7.5% higher compared to neat EVA‐45. The data from thermogravimetric analysis show that the nanocomposites of EVA‐18 and EVA‐45 have ≈10°C higher thermal decomposition temperature compared to neat EVA. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Structure and thermo-mechanical properties study of polyurethane-urea/glycidoxypropyltrimethoxysilane hybrid coatings

A series of organic–inorganic hybrid coatings were prepared using polyurethane (PU)-urea and glycidoxypropyltrimethoxysilane (GPTMS) To prepare this first acid terminated saturated polyester, having 230 hydroxyl value and acid value 25 mg/KOH, were reacted with coupling agent GPTMS at different concentrations in the presence of base catalyst and each of them were further reacted with isophorone diisocyanate (IPDI) at NCO/OH ratio of 1.6:1 for 4–5 h at 70–80 °C These prepolymers were casted on tin foil and cured at ambient conditions for 6 h and prepared the hybrid coating free films by amalgamation. These free films were stored in the room temperature for 40 days and used for further characterization. The coating without and with different concentrations of GPTMS were named as base polymer and hybrid coatings, respectively. FTIR spectroscopy was used for the structural analysis of the coatings. Thermogravimetric analysis (TGA) showed that thermal stability of the hybrids was significantly higher than the base polymer. The onset degradation temperature of the base polymer starts at 268.9 °C, while it ranges from 279.1 °C to 290.8 °C for the hybrids based on the concentration of GPTMS used. The glass transition temperature (T_g) and storage modulus as determined from DMTA were higher for hybrid coatings as compared to base polymer. T_g of base polymer was 42.3 °C while it varies between 65.8 °C to 83.5 °C for hybrids.     

Fabrication and properties of nano‐ZnO/glass‐fiber‐reinforced polypropylene composites

Polypropylene (PP) is widely used in many fields, such as automobiles, medical devices, office equipment, pipe, and architecture. However, its high brittle transformation temperature, low mechanical strength, dyeing properties, antistatic properties, and poor impact resistance, considerably limit its further applications. Nano‐ZnO treated by KH550 coupling agent and glass fibers (GFs) were introduced in order to improve the mechanical performance and flowability of PP in this research. The crystallization behavior and microstructure of nano‐ZnO/GFs/PP hybrid composites were analyzed by differential scanning calorimetry, transmission electron microscopy, and scanning electron microscopy. The effect of crystallization behavior on the mechanical properties of the nanocomposites was investigated and analyzed. The results indicated that nano‐ZnO surface‐coupled by KH550 could be uniformly dispersed in the PP matrix. The incorporation of nano‐ZnO and GFs resulted in increases of the crystallization temperature and crystallization rate of PP and a decrease of the crystallization degree. The introduction of nano‐ZnO and GFs also enhanced the tensile strength and impact toughness of the hybrid composites and improved their fluidity. Composites containing 2% of nano‐ZnO and 40% of GFs possessed the optimum mechanical properties. J. VINYL ADDIT. TECHNOL., 2010. © 2010 Society of Plastics Engineers     

Nonisothermal cure kinetics of diglycidylether of bisphenol‐A/amine system reinforced with nanosilica particles

Epoxy‐silica nanocomposites were obtained from directly blending diglycidylether of bisphenol‐A (DGEBA)‐based epoxy and nanoscale silica (NS) and then curing with 4,4′‐diaminodiphenylamine (DDA). The effect of amount of nanosilica (NS) particles as catalyst on the mechanism and kinetic parameters of cure reaction of DGEBA/DDA system was studied. The kinetics parameters were obtained from nonisothermal differential scanning calorimeter (DSC) data using the Kissinger and Ozawa equations. The exothermic peak was shifted toward lower temperatures in DGEBA/DDA/NS system with increasing the amount of nanoslica particles. However, the existence of NS particles with hydroxyl groups in the structure in the mixture of DGEBA/DDA catalyzes the cure reaction and increases the rate constant. The activation energy of cure reaction of DGEBA/DDA system obtained from two methods were in good agreement, and showed a decrease when NS particles were present in the mixture. The mechanism of reaction of DGEBA with DDA was carried out by isothermal curing in the oven at 130°C and measuring the disappearance peak of epoxide group at 916 cm^?1 using FTIR. The diffusive behavior of two systems was investigated during water sorption at 25°C and the experimental results fitted well to Fick's law. Diffusion coefficient of cured sample from DGEBA/DDA/10% NS blend decreased in comparison with the sample without NS particles. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 3855–3863, 2007     

Thermal and crystallization properties of PBT/ABAS blends

Blends of poly(butylene terephthalate) (PBT) with poly(acrylonitrile‐butyl acrylate‐styrene) (ABAS) were characterized by differential scanning calorimetry, infrared, thermogravimetric analysis, and wide‐angle X‐ray diffraction (WAXD) studies. Addition of ABAS polymer to PBT improved the thermal stability of PBT. Infrared studies showed that ABAS polymer chemically interacts with PBT. The crystallization behavior of PBT was modified in the presence of ABAS polymer. The ABAS polymer showed inappreciable effect on melting behavior of PBT but decreased its crystallization. WAXD studies showed some modification in PBT peaks and a peak with increasing intensity corresponding to the β‐crystalline form of PBT. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Thermal and chemical stabilization of ethylene/vinyl acetate/vinyl alcohol (EVA‐OH) terpolymers under nitroplasticizer environments

In this study, we compare the aging behaviors of cross‐linked ethylene/vinyl acetate/vinyl alcohol terpolymers, also referred to as EVA‐OH, when they are either immersed in nitroplasticizer (NP) liquid or exposed to NP vapor at different temperatures. While thermogravimetric analysis and differential scanning calorimetry are used to probe the thermal stability of aged NP and polymers, Fourier transform infrared, gel permeation chromatography, ultra‐violet/vis, and nuclear magnetic resonance are used to probe their structural changes over the aging process. The study confirms that NP degrades through C? N cleavage, and releases HONO molecules at a slightly elevated temperature (<75°C). As these molecules accumulate in the vapor phase, they react among themselves to create an acidic environment. Therefore, these chemical constituents in the NP vapor significantly accelerate the hydrolysis of EVA‐OH polymer. When the hydrolysis occurs in both vinyl acetate and urethane groups and the scission at the cross‐linker progresses, EVA‐OH becomes vulnerable to further degradation in the NP vapor environment. Through the comprehensive characterization, the possible degradation mechanisms of the terpolymers are proposed. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41450.     

DSC study of foamable poly (vinyl chloride‐co‐vinyl acetate) plastisols of different commercial plasticizers

In this article the characterization of the thermal behavior of foamable PVC (Poly (vinyl chloride)) plastisols from 20 different plasticizers has been studied by differential scanning calorimetry (DSC). The interactions between the resin and the plasticizer as well as the decomposition of the azodicarbonamide (ADC)—the chemical blowing agent (CBA) used—have been analyzed. The latter process is of crucial importance for the knowledge of plasticized PVC flexible foam formation. Clear effects of the chemical nature of the plasticizers and their molecular weight (M_w) have been observed, both in the interactions (swelling and early stages of gelation) between the resin and the plasticizer, as well as in the temperature of the ADC decomposition and the shape of the DSC peak. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Rheological and mechanical performance of ethyl‐vinyl acetate/poly(vinyl chloride) formulations

A range of powdered ethyl‐vinyl acetate (EVA) copolymers and poly(vinyl chloride) (PVC) formulations were compounded at PVC:EVA ratios of 100:0, 60:40, 50:50, 40:60, and 0:100. Two grades of EVA with 20% and 27% of vinyl acetate (VAc) (EVA I and EVA II) and two grades of PVC with K values of 56 and 71 (PVC I and PVC II) were used in the investigation. Mechanical analysis was performed on injection molded samples of these blends, and the results showed that the tensile and flexural moduli decreased significantly with increasing EVA concentration. Rheological analysis was performed by using dual capillary rheometry, and the results showed only slight changes in shear viscosity with increasing EVA content, even at lower shear rates. Dynamic mechanical thermal analysis showed partial miscib lity of the PVC and EVA over the range of concentrations studied.     

Friction properties of sisal fiber/nano‐silica reinforced phenol formaldehyde composites

The friction‐resistant sisal fiber/nano‐silica phenol formaldehyde resin composites were prepared through compression molding. To enhance the bonding between the sisal fiber (SF) and polymer matrix, SF were treated with different surface modifiers. The worn surfaces of composites were observed by scanning electron microscope (SEM). The result shows that the matrix of nano‐silica phenol formaldehyde resin can relieve the heat fade of the friction materials. Meanwhile sisal fibers treated with borax have effectively improved the friction and wear properties of the composites when the fiber content was 15%. POLYM. COMPOS. 36:433–438, 2015. © 2014 Society of Plastics Engineers     

Tin‐containing layered double hydroxides: Synthesis and application in poly(vinyl chloride) cable formulations

Layered double hydroxides (LDHs) and Sn‐containing LDHs have been synthesized using a co‐precipitation method, and the resulting products have been characterized by X‐ray diffraction (XRD), transmission electron microscopy (TEM), Fourier‐transform infrared spectroscopy (FTIR) and Brunauer‐Emmett‐Teller(BET) surface area measurement, clearly showing that Sn‐containing LDH hybrids have been successfully prepared. TEM shows the ‘house‐of‐cards’ structure of the Sn‐LDHs produced, resulting from the edge‐to‐face interaction of the LDH layers. Higher tin levels lead to an additional magnesium hydroxystannate, MgSn(OH)₆, (‘MHS’) phase that is present in the form of approximately 40‐nm cubic particles in an LDH/MHS hybrid structure. FTIR and XRD suggest that, at low levels of Sn, the Sn⁴⁺ may exist in the form of amorphous hydrated tin(IV) oxide rather than being incorporated into the LDH lattice. These powders have been compounded into poly(vinyl chloride) (PVC), and their fire performance has been evaluated using limited oxygen index and cone calorimeter techniques. Peak rate of heat release and smoke parameter can be reduced by 64% and 81%, respectively, when replacing 10 wt% of the primary ATH fire‐retardant filler by the synthesized Sn‐LDHs, while keeping the total fire‐retardant loading at 100 phr. Thermogravimetric analysis indicates that Sn‐LDH is an effective char promoter for PVC. Copyright © 2011 John Wiley & Sons, Ltd.     

Effect of nano‐SiO2 on granule characteristic and fusion process of Poly(vinyl chloride‐co‐vinyl acetate)/nano‐SiO2 composite resin

Poly(vinyl chloride‐co‐vinyl acetate) (PVVA)/nano‐SiO₂ composite resin was prepared by radical suspension polymerization of the monomers in the presence of fumed nano‐SiO₂ particles premodified with γ‐methylacryloxypropyl trimethoxysilane. The cool dioctyl phthalate absorption percentage, granule porosity, and specific surface area of the composite resin were enhanced through incorporation of nano‐SiO₂ into the PVVA. Scanning electron microscope pictures showed the resin had higher porosity. PVVA/nano‐SiO₂ composite resin was mixed with pure PVC resin to form a mixture sample (polymer‐composite blend [PCB]) and the mixture was fused in the torque rheometer. The rheological test results indicated that, at a certain nano‐SiO₂ content, the fusion speed of PCB was accelerated and the fusion temperature of PCB was decreased, owing to nano‐SiO₂ dispersed evenly in the polymer matrix. When excessive nano‐SiO₂ was loaded, the fusion torque, the fusion time, and the fusion temperature of PCB were all increased. These properties are correlative to the dispersive density of nano‐SiO₂ in the polymer matrix. This study also demonstrated that the introduction of small amounts of nano‐SiO₂ into the resin increased the impact strength and tensile strength of PCB simultaneously. J. VINYL ADDIT. TECHNOL., 20:230–236, 2014. © 2014 Society of Plastics Engineers