VINYL ADDIT Research Articles

Low volatile monofunctional reactive diluents for radiation curable formulations

AbstractIn the last decades the importance of UV curable formulations has increased continuously. Their fast curing speed, solvent‐free polymerization conditions, and the formation of hard and highly crosslinked photopolymer networks represent major benefits. Commercial UV resins generally consist of multi‐functional vinyl oligomers, photoinitiators, additives, and reactive diluents. Mono‐ and multi‐functional reactive diluents serve as thinners to lower the overall resin viscosity and to improve processability. However, many monofunctional reactive diluents like isobornyl (meth)acrylate or benzyl (meth)acrylate exhibit high volatility, often already at room temperature. This causes adverse effects such as unpleasant odor, potential health risks, and changing resin composition during processing. A new group of monomers that show high potential for replacing traditional highly volatile reactive diluents are salicylate (meth)acrylates. In this work, salicylate‐based thinners are synthesized, polymerized, and characterized with respect to their viscosity, volatility, thermal stability, photoreactivity, and thermomechanical properties of their homopolymers. Additionally, a first example of their diluting effect in a highly viscous difunctional polyester urethane methacrylate is demonstrated with 30 wt% of a cycloaliphatically and an aromatically substituted salicylate methacrylate. The polymers of the diluted resin exhibit similarly high glass transition temperatures of 110 and 126 °C, which are in the range of the polymers of the undiluted resin.

Highly efficient vinylic addition polymerization of 5-vinyl-2-norbornene using benzylic palladium complexes as precatalysts

A very small amount of a palladium benzylic complex as initiator brings about the vinylic addition polymerization of the reluctant 5-vinyl-2-norbornene.

Living/Controlled Vinyl Addition Polymerization of Cyclopropenes Catalyzed by Palladium Complex

Living/Controlled Vinyl Addition Polymerization of Cyclopropenes Catalyzed by Palladium Complex

Poly (vinyl alcohol) modification of poly(vinylidene fluoride) microfiltration membranes for oil/water emulsion separation via an unconventional radiation method

Owing to inherent hydrophobicity, most polymer membranes suffer from serious fouling by organic pollutants, which severely deteriorates separation performances and reduce membrane lifetimes. Thus, surface hydrophilic modifications are essential to the development and application of various polymer membranes. Here, an unconventional but simple one-step approach was used to modify the surface of poly(vinylidene fluoride) (PVDF) membranes to produce good hydrophilicity and underwater superoleophobicity. This method directly anchored hydrophilic poly(vinyl alcohol) (PVA) onto PVDF membrane surfaces under γ-ray irradiation but without any vinyl additives. The obtained modified PVDF membranes possessed excellent separation performances for various oil-in-water emulsions, with oil rejection up to 99.5% and filtration flux up to 6.9 × 102 L m−2 h−1 bar−1 under ultralow pressure (0.084 bar). In addition, oil fouling was confirmed to be almost reversible on modified PVDF membranes, which made the flux recovery remarkably improved, from 33% of pristine PVDF membrane to 98% of modified membranes, and they also exhibited outstanding oil-fouling resistance to high viscosity oils. This study demonstrated that this unconventional radiation method was facile and effective for tailoring the performance of polymer membranes with saturated functional compounds, which could benefit the development of various functional membranes and other materials.

Pd(acac)(PR3)(PhCN)][BF4] and [Pd(acac)(S)2][BF4] (R = phenyl, 2-methoxyphenyl; S = benzonitrile, pyridine): Synthesis, characterization, reactivity and catalytic behavior. Crystal structure of Pd(κ2-O,O′-acac)(κ1-C-acac)(P(2-MeOC6H4)3)

The Pd(II)complexes [Pd(acac)(PR3)(PhCN)][BF4] and [Pd(acac)(S)2][BF4] (acac = acetylacetonate; R = phenyl, 2-methoxyphenyl; S = benzonitrile, pyridine, CD3CN) were synthesized by the reaction of Pd(acac)2 or Pd(acac)2·PR3 with 2 equiv. of BF3·OEt2 in the presence of appropriate ligands (S). The structural features of the complexes were analyzed by NMR and FTIR spectroscopies. Computed FTIR spectra was in agreement with the corresponding experimental data, the correlation between ν(CN) of the κ1-nitrile ligands and DFT-calculated geometrical features of the complexes was proposed. Complex Pd (κ2-O,O′-acac)(κ1-C-acac)(TOMPP) (TOMPP = tris(ortho-methoxyphenyl)phosphine) was characterized by X-ray diffractometry. XRD, 1H and 31P NMR analyses were consistent with formation of three unequally populated rotamers of Pd(κ2-O,O′-acac)(κ1-C-acac)(TOMPP) in CDCl3 which differ in the orientation of the endo-(2-methoxy)phenyl ring in exo2 conformation of coordinated TOMPP. Reaction of [Pd(acac)(PR3)(PhCN)]BF4 with L (L = pyridine, morpholine, TOMPP) in the majority of cases gave mixtures of [Pd(acac)(PR3)(L)]BF4, [Pd(acac)(L)2]BF4, and [Pd(acac)(PR3)2]BF4 as result of sequence of ligand substitution reactions. The cationic palladium catalyst precursors were found to be active catalysts for phenylacetylene polymerization and oligomerization. Only cationic pre-catalysts with bulky TOMPP ligand gave high-molecular weight polyphenylacetylene. Catalysts with less bulky substituents mostly formed phenylacetylene oligomers. When activated with BF3⋅OEt2, these palladium complexes can also be used as catalysts for the vinyl addition polymerization of norbornene with activities 104–107 gpolymer molPd h−1.

A Facile and Green Approach Toward Preparation of Nanocellular Poly(Butylene Succinate)/Hydroxyl‐Functionalized Graphene Composite Foam Induced by Nonisothermal Crystallization

In this article, a facile and green strategy of nonisothermal crystallization induction was proposed to produce nanocellular biodegradable polymer composite foams, which was demonstrated by a composite system of poly(butylene succinate) (PBS) modified by hydroxyl‐functionalized graphene (HG) and chain extender. Nanocellular foams of chain extended PBS (CPBS) and CPBS/HG composite were prepared successfully with supercritical CO2. Two significant phenomena about the preparation of nanobubbles in CPBS and CPBS/HG composite foams were found. One was that the nanobubbles generated at the temperature region of crystallization transition and the other was that chain extension played a critical function in the generation of nanobubbles. As the foaming temperature switched from 86 to 85°C, an interesting microbubble to nanobubble transition in CPBS and CPBS/HG foams was observed. Due to the generation of nanobubbles and the enhancement of volume expansion ratio, an excellent thermal insulation performance was achieved by CPBS/HG foams. J. VINYL ADDIT. TECHNOL., 26:461–474, 2020. © 2020 Society of Plastics Engineers

Low‐Density Polyethylene/Poly(Lactic Acid) Blends Reinforced by Waste Wood Flour

The main purpose of this work was the valorization of waste wood flour as reinforcement in order to develop new wood‐based polymer composites (WBPCs). For that purpose, low‐density polyethylene/poly(lactic acid) (LDPE/PLA) blends were prepared in presence of poly(ethylene‐co‐glycidyl methacrylate) (PE‐g‐GMA) as compatibilizer and reinforced with 0–40 wt% of wood flour. The tensile properties, Charpy impact strength, morphology, and thermal properties (differential scanning calorimetry (DSC) and thermogravimetric analysis [TGA, DTG]) of the LDPE/PLA/PE‐g‐GMA (20/80/5) composites were characterized. The results showed that Young's modulus increased with increasing the wood flour content and the composites are brittle. Globally, stress at break, elongation at break, and Charpy impact decreased with increasing the content of wood flour. Morphological investigation revealed a good interfacial adhesion between LDPE/PLA/PE‐g‐GMA blend and wood flour. The stability of composites was affected by the incorporation of 10 wt% of wood flour and varied slightly with the increase in load. The values of speed of maximal weight loss of the composites were lower than that obtained for the blend without wood flour. The dispersion of wood flour decreased the onset degradation temperature of PLA, while the rate of thermal degradation of composites was improved. On the other hand, the degree of crystallinity of composites increased by the addition of wood flour indicating the possibility that wood flour can act as nucleating agent. Finally, the water absorption of the composites depends on the immersion time, the nature, and the content of the load. J. VINYL ADDIT. TECHNOL., 26:443–451, 2020. © 2020 Society of Plastics Engineers

Effectofsiwak Extractson The Hardnessproperty of Vinyl Addition Cured Silicone Maxillofacial Prosthetic Material

Aims: The study aims to evaluate the hardness of the vinyl addition silicone maxillofacial material under the influence of disinfection and immersion time.  Materials and Methods: 40 samples of (20*15*3.5)mm were fabricated from the maxillofacial elastomer and divided into 4 groups of disinfection solutions (three concentrations of siwak extract: 1%  , 2%  and 5%), and  Chlorehexidine was used as a commercial disinfectant , each group was subdivided into 2 immersion periods (15 and 30 hours), the hardness of the samples was measured before immersion and considered as self control and also the hardness was measured at the end of each immersion period by the use of Shore-A durometer. Results: A significant difference was observed in hardness means after immersion and also there were significant differences between groups of disinfection in which siwak extract 1% observed the least value and chlorehexidine the highest one. Conclusions: long immersion period 30 hours increased the hardness of the maxillofacial elastomer more than the shorter period 15 hours and the disinfection with the extracts of Siwakwere  better  than chlorhexidine when the hardness is the factor.

Organopalygorskite and Molybdenum Sulfide Combinations to Produce Mechanical and Processing Enhanced Flame‐Retardant PE/EVA Blend Composites with Low Magnesium Hydroxide Loading

The effect of organopalygorskite (OPGS), molybdenum sulfide (MoS2), and magnesium hydroxide (MH) combinations on fire retardant and flammability characteristics of low‐density polyethylene/ethylene vinyl acetate (LDPE/EVA) blends was investigated using the limited oxygen index (LOI), horizontal burning test (UL‐94), and cone calorimeter measurements. The combination of OPGS with exfoliated MoS2 nanosheets is employed to reduce the conventional hydroxide content and enhance the PE/EVA blend flame‐retardant properties with a notable improvement in mechanical and processing characteristics. The flame‐retardant properties of the composites were compared with a reference PE/EVA sample with 55 wt% of MH, which is commonly used for wire coating. The effect of each additive and the use of a maleated polyethylene (PEgMA) as a compatibilizing agent on PE/EVA flame‐retardant properties were analyzed. The results of the LOI and UL‐94 tests confirmed that the addition of OPGS combined with MoS2 substantially increases the LOI value (26%) and reduces the burning rate (66%) and the pHRR (83%) compared with neat polymer blend and passes V‐0 rating during UL‐94 vertical test, which were very similar to the values obtained for the reference sample with higher MH content. In addition, the results indicate that the addition of these additives simultaneously increases the tensile modulus with mechanical properties even higher than the reference sample. Most important, the results indicated that these additive combination allows to reduce the total MH filler content to achieve the flame‐retardant requirements and with enhanced mechanical properties and with higher melt flow rates and lower viscosities facilitating the processing of the polymer composites at lower pressure in the processing extruder. Therefore, this additives combination provides a favorable way to obtain efficient flame‐retardant materials with halogen‐free, low smoke, and easy processing characteristics. J. VINYL ADDIT. TECHNOL., 26:434–442, 2020. © 2020 Society of Plastics Engineers

Influence of Electron Beam Irradiation on High‐Temperature Mechanical Properties of Ethylene Vinyl Acetate/Carbon Fibers Composites

The purpose of this study was to investigate the effect of carbon fiber (CF) and electron‐beam (EB) radiation on high‐temperature mechanical properties of ethylene‐vinyl acetate (EVA). Polymer composites were prepared by mixing on a two‐roll mill. After compression molding, the samples were irradiated between 60 and 180 kGy, and dynamic mechanical analysis (DMA) was used to characterize physical properties. The effects of filler content and radiation level on the mechanical properties of EVA/CF were evaluated. The shear stress and modulus were observed to increase with increasing of the filler level. However, there was a dramatic decrease in creep compliance. It was also shown that introduction of irradiation on EVA composite increases the shear stress and the real part of the dynamic shear modulus G' due to the increase in molecular weight and cross‐linking of the polymer after irradiation. J. VINYL ADDIT. TECHNOL., 26:325–335, 2020. © 2019 Society of Plastics Engineers

Twenty Years of the Polyvinyl Chloride Sustainability Challenges

Intense campaigning pressure on the UK polyvinyl chloride (PVC) sector up to the late 1990s forced strategic engagement with sustainable development. Simplified outcomes from a detailed, consensus‐based analysis by science‐based NGO The Natural Step (TNS) took the form of five TNS sustainability challenges for PVC published in 2000. UK manufacturing companies initially used these challenges to direct strategic progress. The challenges have since been progressively taken up across European PVC value chains. The VinylPlus® program uses an updated version of the five challenges as a basis for voluntary commitments and transparent auditing of progress against published targets. Initial framing of the five TNS sustainability challenges for PVC was drafted consciously for generic relevance to other materials. Assessing the sustainability performance of some alternative materials to PVC against the five sustainability challenges reveals different sustainability performance in a range of potential applications. This highlights the danger inherent in automatic selection or deselection of materials in the absence of assessment of options on a “level playing field” of sustainability principles. The five TNS sustainability challenges for PVC remain valid today and into the longer‐term future as a basis for making stepwise, profitable progress toward the goal of sustainability for PVC and other materials. J. VINYL ADDIT. TECHNOL., 26:390–402, 2020. © 2019 Society of Plastics Engineers

A Comprehensive Study on Physical, Mechanical, and Thermal Properties of Poly(Ethylene Terephthalate) Filled by Micro‐ and Nanoglass Flakes

Polyethylene terephthalate (PET) composites containing micro‐ and nanoglass flakes were prepared by melt blending. The percentage of nanoglass flakes was varied from 0.5, 1, 2, and 3 wt% and the concentration of microglass flakes was 1, 3, and 5 wt%. The effect of glass flake on morphology, physical, mechanical, and thermal properties of PET was studied using scanning electron microscopy (SEM), energy‐dispersive X‐ray analysis (EDXA), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), dynamic mechanical thermal analysis (DMTA), X‐ray diffraction (XRD), and tensile test. The observations showed that both types of particles were dispersed in PET, homogeneously, though microglass flakes had better dispersion compared with their nanosized counterparts. According to DSC thermogram, the crystallization rate and temperature of PET increased with incorporation of both types of glass flakes. The crystallization rate of PET was increased from 31.41% to 34.25% with the addition of 1 wt% of nanoglass flakes. Moreover, the onset of thermal degradation increased more than 9°C with the addition of micro‐ and nanoglass flakes. Based on the mechanical viewpoint, the Young's modulus of PET was improved by the addition of both micro‐ and nanoglass flakes. On the other hand, the tensile strength of PET was decreased from 45.4 MPa to 31.3 MPa using 1 wt% of nanoglass flakes. According to X‐ray diffractometry, using of micro‐ and nanoglass flakes resulted in the decrement of PET crystallites. Whereas, the size of crystallites was lower than microglass flakes, in the case of using nanoglass flakes. J. VINYL ADDIT. TECHNOL., 26:380–389, 2020. © 2019 Society of Plastics Engineers

Radiation Synthesis of Carboxymethyl Cellulose Hydrogels for Removal of Organic Contaminants from Its Aqueous Solution

Preparation of hydrogels based on carboxymethyl cellulose (CMC) using direct radiation grafting technique for removal of organic contaminant such as 4‐chlorophenol and 2,4‐dichlorophenoxyacetic acid (2,4‐D) was carried out. The prepared hydrogels which are composed of individual radiation grafting of methacrylic acid onto CMC to form poly(CMC/MAA) the other hydrogel composed of binary acrylamide/methacrylic acid grafted onto CMC to form poly(CMC/MAA:AAm) hydrogels. The two selected composition poly(CMC/MAA:AAm) (1/60:40 wt%) poly(CMC/MAA) (1:20) wt% hydrogels due to its high chelating properties obtained from our previous work by the same authors. The properties of the selected two prepared hydrogels were evaluated by using different analytical tools such as Fourier transform infrared (FTIR), X‐ray diffraction (XRD), and thermogravimetric analysis (TGA). The gel (%) and the swelling behavior of poly(CMC/MAA:AAm) is higher than poly(CMC/MAAc) hydrogel. It is found that the adsorption capacity of poly(CMC/MAA) hydrogel (1:20 wt%) toward 4‐chlorophenol and 2,4 dichlorophenoxy acetic acid was higher than that of poly(CMC/MAA:AAm) (1/60:40 wt%) hydrogel. Also The obtained results showed that the adsorption capacity of both poly(CMC/MAA:AAm) (1/60:40 wt%) and poly(CMC/MAA) (1:20) wt% hydrogels toward 2,4 dichlorophenoxy acetic acid was higher than of 4‐chlorophenol. J. VINYL ADDIT. TECHNOL., 26:362–369, 2020. © 2019 Society of Plastics Engineers

The crystallization, thermal and mechanical properties of nano‐Sb2O3 filled poly(butylene terephthalate)

Nano‐Sb2O3 particles were modified by a combination modifier of cetyltrimethyl ammonium bromide (CTAB) and KH‐560 via the mechanochemical method based on high‐energy ball milling. Then, the testing specimens of the nano‐Sb2O3/PBT composites of differing compositions were prepared by melting blending technology. The crystallization, thermal, and mechanical properties of composites were characterized by X‐ray diffraction, differential scanning calorimetry, thermogravimetric analyzer, and mechanical performance test. The tensile and impact fracture surfaces of composites were determined by scanning electron microscopy. Besides, the influence of the Sb2O3 nanoparticles surface modification on crystallinity, mechanical properties of the composites, and the interfacial adhesion between nano‐Sb2O3 and PBT was systematically investigated. The results indicate that the main crystalline characteristics of PBT matrix remain unchanged in the nanocomposites. However, the addition of nano‐Sb2O3 particles plays a heterogeneous nucleation and can effectively improve the crystallization of PBT matrix. In addition, the compound modification of the nano‐Sb2O3 can effectively enhance mechanical properties of the composites and interfacial interaction between nano‐Sb2O3 and PBT. The enhanced fracture properties in the nanocomposites were caused by the assisted void formation at the edge of the nano‐Sb2O3 particle. When the nano‐Sb2O3 mass fraction is 3%, the composites show excellent comprehensive performance. The interfacial adhesion parameter B and the half‐debonding angle θ of composites were assessed to quantitatively characterize the interfacial adhesion strength between nano‐Sb2O3 and PBT. Finally, the reinforcement and toughening mechanisms were described. J. VINYL ADDIT. TECHNOL., 26:268–281, 2020. © 2019 Society of Plastics Engineers

Response Surface Analysis of PS/EPDM/PA6 Ternary Blends: Effect of Mixing Sequence, Composition, and Viscosity Ratio on the Mechanical Properties

In this work, effect of three factors on the phase morphology and mechanical properties of ternary blends based on polystyrene (PS)/ethylene‐propylene‐diene terpolymer (EPDM)/polyamide6 (PA6) was investigated by response surface methodology (RSM). Results indicated that among the studied factors (i.e., mixing sequence, composition, and viscosity ratio of the minor phases), the first two have the greatest effect on the impact strength (75.6%) and tensile properties (tensile modulus (84.9%) and yield stress (88.9%); while EPDM/PA6 viscosity ratio has the least effect (≤ 2.1%) on the final mechanical properties. These achievements are, in fact, arising from the considerable changes in the phase morphology and the contribution share predicted by experimental design outputs. However, mixing sequences just affected on the size of dispersed particles, but samples with different compositions presented different morphology types. According to the mechanical characterization of PS/EPDM/PA6 blends, the maximum impact strength and tensile properties were not obtained simultaneously. Optimal levels of input factors, aimed to balance impact strength and tensile properties, are M1 simultaneous mixing sequence, C1 composition (70/10/20), and V1 viscosity ratio (PA6 with low viscosity). J. VINYL ADDIT. TECHNOL., 26:282–290, 2020. © 2019 Society of Plastics Engineers

Enhancement of Photostabilization of Poly(vinyl chloride) Doped with Sulfadiazine Tin Complexes

New sulfadiazine tin complexes were synthesized in 67–80% yields from the reaction of sulfadiazine, and different organotin(IV) chlorides and their structures were established. The synthesized complexes were used as additives at a low concentration (0.5% by weight) to enhance poly(vinyl chloride) (PVC) photostability. The PVC samples containing sulfadiazine tin complexes (thickness = 40 μm) were fabricated and irradiated with ultraviolet light at room temperature for 300 h. The changes that occurred within the PVC samples upon irradiation were investigated by inspecting the loss in weight, reduction in the average molecular weight, formation of small degradation fragments containing polyene, carbonyl, and hydroxyl moieties, and changes in the ultraviolet absorption intensity of polymeric materials. The surface morphology of irradiated PVC samples was investigated using optical, atomic force, and scanning electron microscopies. There were lesser changes within the PVC samples with sulfadiazine tin complexes compared to the blank PVC sample. The dimethyltin(IV) complex was found to be the most efficient additive in stabilizing PVC against irradiation. The role played by the complexes in reducing the photodegradation of PVC was investigated, and a mechanism was proposed. J. VINYL ADDIT. TECHNOL., 26:370–379, 2020. © 2019 Society of Plastics Engineers

Fabrication of Damping Material over Broad Temperature Range: Blending Amorphous Styrene‐Butadiene‐Styrene Triblock Copolymer with Semi‐Crystalline Syndiotactic 1,2‐Polybutadiene

Broad‐temperature‐range (−85.4 to 96.2 °C) damping material was fabricated by blending amorphous styrene‐butadiene‐styrene triblock copolymer (SBS) with semicrystalline syndiotactic 1,2‐polybutadiene (s‐PB). According to dynamic mechanical thermal analysis (DMTA) analysis, SBS/s‐PB blends exhibited three consecutive damping peaks at −85.4, 2.7, and 96.2 °C. The peaks at −85.4 and 96.2 °C were associated with the glass transition of polybutadiene and polystyrene in SBS, and peak at 2.7 °C belonged to the glass transition of s‐PB. The analysis of rheological behavior and thermal properties showed that the mobility and thermal stability of SBS/s‐PB blends improved with the introduction of semi‐crystalline s‐PB. Moreover, regarding the results of DMTA, Fourier transform infrared spectroscopy (FTIR) and Scanning electron microscopy (SEM) measurements, SBS and s‐PB were compatible in the macroscopic scale while they were immiscible in thermodynamic scale. Wide‐angle X‐ray diffraction (WAXD) results present the crystal structure of blends were unchanged. Besides, with the introduction of s‐PB in blends, 100% tensile modulus increased from 3.2 to 5.8 MPa and tear strength increased from 49.2 to 84.2 kN/m. The Kerner–Uemura–Takayanagi model was employed to compare with experimental data. Thus, broad‐temperature‐range damping material was fabricated by blending SBS with s‐PB and the material combined with good processability, thermal stability, and mechanical properties. J. VINYL ADDIT. TECHNOL., 26:336–347, 2020. © 2019 Society of Plastics Engineers

Rheological Properties of Epoxy/Polypyrrole Coating and its Behavior as EMI Material

In this study, we analyze the rheological properties of epoxy/polypyrrole/carbon black coating and its performance as electromagnetic interference shielding efficiency (EMI SE). For this purpose, a commercial epoxy coating was mixed with a conductive polymer, namely polypyrrole. Rheological tests were performed to obtain the flow curve, the storage and loss moduli, the cure time and thixotropic characteristics. Thermal analysis of DSC (cure behavior) and EMI SE were also performed. Epoxy coating showed non‐Newtonian (shear thinning) behavior. The addition of PPy.DBSA reduced the coating fluidity by the increase in consistency index and viscosity. The stress oscillatory amplitude sweep test was performed to determine the linear viscoelastic range. The results of the LVR stress and strain frequency sweep tests were compared to the PPy.DBSA. The results show that LVR and critical crossover change with the percent of Polypyrrole. The cure times obtained by the rheometer and DSC were in good agreement: the addition of polypyrrole reduced the cure time, probably due to the presence of amino groups in the PPy.DBSA, which can react with the oxirane ring in the epoxy resin. The EMI SE attenuation by absorption and reflection mechanism was observed by adding 10 phr of PPy.DBSA. For practical applications, it is necessary to combine polypyrrole with conducting carbon black. The formulation with 1.5 phr of carbon black improves the EMI SE performance to 72%. J. VINYL ADDIT. TECHNOL., 26:348–353, 2020. © 2019 Society of Plastics Engineers

Improving Thermal Stability and Electrical Insulation of Gamma‐Irradiated Silicone Rubber Nanocomposites

Room temperature vulcanized silicone rubber (RTVSR) nanocomposites were prepared by mixing of surface‐modified montmorillonite nanoclay or nano fumed silica, or both of them with RTVSR to improve thermal stability, electrical insulation, and flame retardant. Their tensile strength, elongation, swelling, and solubility properties at different doses of gamma radiation were investigated to study the effect of gamma radiation on the properties of the nanocomposites. The thermal stability, flammability properties, and volume resistivity of the nanocomposites were also investigated. The nanocomposite which containing fumed silica has the best thermal, mechanical properties, electrical insulation and fire retardancy. The thermal characteristics, namely, Tonset, T10%, Tcomp, and Tmax, of the nanocomposite sample containing fumed silica were 22, 23, 13, and 11 °C higher than those of the blank, respectively. The tensile strength (TS) increased when the radiation dose was increased up to 100 kGy, but elongation, swelling, and solubility decreased when the radiation dose was increased up to 150 kGy. It can be generally concluded that the nanocomposites containing fumed silica and irradiated to 100 kGy are characterized by having outstanding mechanical, thermal, fire retardant, and electrical insulation properties and hence, they may have wide industrial applications as good thermal and electrical insulating materials. J. VINYL ADDIT. TECHNOL., 26:354–361, 2020. © 2019 Society of Plastics Engineers

Gelation of Plasticized Polyvinyl Chloride Compounds in a Co‐Kneader

The co‐kneader is a proper tool for processing polyvinyl chloride (PVC) compounds. Gelation of PVC is complex because of a narrow processing window. At low temperature, gelation is incomplete and leads to poor mechanical properties, while at high temperature, degradation may occur. The aim of this study is to gain a fundamental understanding of the gelation process of PVC in co‐kneaders. Careful examination of the gelation state of extruded PVC samples was carried out qualitatively by swelling the extruded samples in acetone and quantitatively by differential scanning calorimetry measurements. Gelation in various conditions of temperature and shear was firstly studied in a capillary device that ensures both pre‐shearing and extrusion through a circular die. This provided a reference basis for comparison with gelation state obtained in the co‐kneader. Samples were collected in the co‐kneader by means of opening the barrel. The gelation state was particularly examined in connection with the measured temperature at a fixed position along the screw at which a temperature sensor was positioned. The obtained results showed that the co‐kneader allows fast gelation with a mixing energy value lower than 200 kJ/kg when the temperature is higher than a critical value of 165°C for the studied formulation. J. VINYL ADDIT. TECHNOL., 2019. © 2019 Society of Plastics Engineers J. VINYL ADDIT. TECHNOL., 26:316–324, 2020. © 2019 Society of Plastics Engineers