Rigid PVC Research Articles

Effects of Organic Based Heat Stabilizer on Properties of Polyvinyl Chloride for Pipe Applications: A Comparative Study with Pb and CaZn Systems.

In this paper, the effects of organic based stabilizers (OBS) are investigated and compared with traditional lead (Pb) and calcium zinc (CaZn) heat stabilizers regarding their processability, mechanical property, and thermal degradation behaviors in rigid PVC pipe applications. In addition, the effects of repeated processing cycles on the degree of gelation and the impact strength of the PVC/OBS, PVC/CaZn, and PVC/Pb are also examined. A repeated processing cycle of those three types of the heat stabilizers up to four cycles was found to increase the degree of gelation and proved no significant effect on the impact strength and heat resistance of the resulting PVC samples. The OBS showed a positive effect on preventing the autocatalytic-typed thermal degradation of the PVC samples. This leads to a longer retention time for the initial color change of the PVC/OBS compared to PVC/Pb or PVC/CaZn systems. This characteristic was related to a more uniform fusion behavior of the PVC/OBS, i.e., the lowest gelation speed and the longest fusion time. The non-isothermal kinetic parameter determined by the Kissinger and Flynn–Wall–Ozawa methods of the dehydrochlorination stage of the PVC/OBS was in satisfactory agreement and continued to compare with the PVC/Pb and PVC/CaZn systems. The results indicated that the OBS might decrease the dehydrochlorination rate of PVC, implying that PVC/OBS was more stable than PVC/Pb and PVC/CaZn systems.

Thermal aging effects on the microstructure of rigid PVC tubes used for water transportation in sub-Saharan region

This paper reports on experiments carried out to highlight the effect of thermal aging on the microstructure of (u-PVC) tube used for freshwater transportation in sub-Saharan region. Two thermal aging protocols the both of 90 days were performed on the (u-PVC) specimens, at respectively 50 and 60 °C. The structural changes undergone by the (u-PVC) were monitored by FTIR-spectroscopy. It has been found that dehydrochlorination is the major event of the aging process. However, the stabilizer system played a key role in HCl-scavenging and chlorine atoms substitution. The aging temperature increased the kinetic of the oxidation reactions but also the stabilizer consumption. Chain scission reactions and structural changes were revealed by DSC-analysis.

Synergistic effect of talc/calcined kaolin binary fillers on rigid PVC: Improved properties of PVC composites

AbstractThis study aims to develop poly(vinyl chloride) (PVC) composites prepared by melt mixing by using a combination of talc and calcined kaolin as filler in order to improve the disadvantages of rigid PVC, which is widely used in industry, such as poor mechanical properties and low thermal stability. In addition, PVC/talc and PVC/calcined kaolin composites were also examined for comparison. The calcined kaolin is modified with urea to increase the surface area (chemical treatment), while the surface of both fillers is coated with stearic acid for good compatibility with PVC (mechanical treatment). Scanning electron microscopy micrographs showed homogeneous distribution of mechanically processed fillers. Attenuated total reflectance–Fourier‐transform infrared spectroscopy analysis revealed successful coating of the fillers with stearic acid. Also, new bands were detected in the spectrum of urea‐treated calcined kaolin, showing an effective chemical treatment. It has been observed that the treatment of fillers improves the mechanical properties of PVC. Thermogravimetric results showed that delaminated calcined kaolin increased the thermal stability of PVC composites. The results of this study proved that binary filler composites combine good properties of both (synergistic effect) and good filler dispersion can be obtained by using stearic acid and urea.

Iterative calculation of local head loss coefficient of emitters in lateral lines

ABSTRACT This study aimed to iteratively set the local head loss coefficient of the Naan® micro-sprinkler, model 7110 Hadar, installed in a lateral irrigation line. To evaluate the total head loss along the lateral line, tests were performed using a rigid PVC pipe with an inner diameter of 15.8 mm, 12 m in length, and 24 micro-sprinklers inserted along the pipe, regularly spaced 0.5 m. In the tests carried out for four micro-sprinkler nozzle diameters (0.9, 1.0, 1.1, and 1.2 mm) and six inlet pressure head values (5, 10, 15, 20, 25, and 30 m) in the line, the pressure head difference between inlet and outlet in the pipe and the discharge of each emitter along the pipe were measured. The head loss computation was performed by the step-by-step procedure, starting from the downstream end to the upstream end of the line; since varying the local head loss coefficient values iteratively, the total head loss measured in the tests was equal to the calculated. For the different working conditions of the inlet pressure head and the micro-sprinkler nozzle diameter, the local head loss coefficient had values from 0.051 to 0.169. Relating the discharge values measured and estimated along the lateral line, the confidence coefficient of 0.9991 was verified, and the calculation procedure was considered optimal.

Determination of elasticity modulus of flexible reinforced PVC hoses material at temperature change based on experimental studies and finite element modeling

A description of laboratory unit and a finite-element mathematical model is given, the joint use of which makes it possible to carry out studies of the stress-strain state of flexible hoses based on plasticized PVC with spiral reinforcement made from rigid PVC. The results of laboratory tests and numerical modeling of PVC hoses during freezing and heating to various temperatures are presented. The result of the study is the determination of the modulus of elasticity of the PVC hose base material depending on temperature.

The Role of Calender Gap in Barrel and Screw Wear in Counterrotating Twin Screw Extruders

It has been known in the industrial sector that in closely intermeshing counterrotating twin screw extruders, large separating forces develop in the calender gap, which push the screws towards the barrel wall. The result is significant wear in the region defined by 30°- and 60°-degree angles from the vertical. In the present investigation, pressures were measured around the barrel in extrusion of two rigid PVC resins in a laboratory extruder of 55 mm diameter and the forces on the screw core were determined. Numerical flow simulations were also carried out using the power-law viscosity parameters of the resins. From the experimental results, it was determined that the resultant forces are in the 30 degree angle direction, and from the computer simulations, the angle is between 18° and 25°. It is argued that the resultant force angle will be somewhat larger in large diameter extruders, due to the additional contribution of gravity.

Synthesis of poly(vinyl chloride)-co-poly(acrylic acid) by precipitation polymerization and its usage as CaCO3 modifier in rigid PVC composites

Incorporating carboxyl group into the poly(vinyl chloride) (PVC) resin can endow PVC with reactivity in some applications. In this work, poly(vinyl chloride)-co-poly(acrylic acid) random copolymer (PVCA) with low average number molecular weight (M n, ∼10 k) is synthesized by precipitation polymerization. By tuning acrylic acid dropping rate, the PVCA copolymer with much more uniform copolymer composition is obtained in comparison to all monomer-in process. Subsequently, the PVCA is utilized as a novel polymer modifier for the surface treatment of CaCO3 particles and its effect on the mechanical properties of obtained rigid PVC composites are evaluated systematically. As a result, the PVAC modified CaCO3 particles exhibit uniform dispersibility and excellent compatibility in PVC matrix. Additionally, the thermal stability is improved significantly owing to the calcium ions on the surface of CaCO3 particles, which scavenge the hydrogen chloride and retard the autocatalytic dehydrochlorination process. Impressively, it also has an enhancement both in tensile strength (ca. 46.4 MPa, and 119.8% elongation at break) and in impact strength (2.7 kJ m−2) in comparison to those modified by commercialized agents such as stearic acid and titanate ester. This work provides valuable insights for the preparation of vinyl chloride copolymers and opens a new application.

Effects of Coagent Functionalities on Properties of Ultrafine Fully Vulcanized Powdered Natural Rubber Prepared as Toughening Filler in Rigid PVC.

Ultrafine fully vulcanized powdered natural rubber (UFPNR) has a promising application as a renewable toughening modifier in polymer matrices. In this work, the effects of acrylate coagents, which had different amounts of functional groups, on properties of UFPNR produced by radiation vulcanization and spray-drying was systematically investigated for the first time. Dipropylene glycol diacrylate (DPGDA), trimethylol propane trimethaacrylate (TMPTMA), and ditrimethylol propane tetraacrylate (DTMPTA) were used as coagents with two, three, and four acrylate groups, respectively. The radiation in the range of 250 to 400 kGy and coagent contents of up to 11 phr were used in the production process. Physical, chemical, and thermal properties of the UFPNR were characterized by swelling analysis, scanning electron microscopy, infrared spectroscopy, thermogravimetric analysis, and differential scanning calorimetry. The properties of UFPNR produced by using different type and content of coagents were compared and discussed. The results revealed that UFPNR with the smallest particle size of 3.6 ± 1.1 μm and the highest thermal stability (Td5 = 349 °C) could be obtained by using DTMPTA, which had the highest amount of functional group. It was proposed that the coagent with the greater number of acrylate groups enhanced the crosslinking of natural rubber as it had more reactive groups. Finally, an application of UFPNR as a toughening filler in rigid PVC was demonstrated with 34% improvement of impact strength.

Year-Round Heap Leaching of Gold in Cryolithozone

The experience of heap leaching (HL) was analyzed in the following cold climate regions: Alaska, Western regions of the United States, Canada, Kazakhstan, and Russia. The disadvantages of the developed domestic mobile units were uncovered, and the potential for creating HL mobile units was assessed to enable a year-round use of the technology, including in the cryolithozone. The results are presented, which were obtained during investigation of the material composition of the study object, i.e., technogenic gold-containing deposits of the Transbaikal region. The main element content of the mineral raw materials of the technogenic deposits was as follows: Au — 0.35 g/m3, Ag — 3.9 g/m3, SiO2 — 69.3 %, Al2O3 — 15.4 %, Fe2O3 — 5.9 %, CaO — 0.21 %, and MgO — 1.15 %. The phase forms of gold included: cyanidable (intergrown) — 2.3 %, “sealed in quartz” — 13.5 %, “enveloped” — 28.6 %, in magnetite — 55.6 %. A continuous process line was developed, which included the following four unit modules: gravity concentration, first stage of leaching (tank leaching), second stage of leaching (heap leaching), and sorption. The layout of the continuous process line (HL option during the period of subzero temperatures) is provided. The optimal values of the main process parameters of gravity concentration, as well as the first and second stages of leaching have been established experimentally. Prior to tank leaching, an active multiple-reagent solution based on sodium chloride, water and ozone compounds was prepared in a sealed electrochemical reactor. The tank was partitioned into three sections, in which the following operations were carried out in series: chemical opening of the gold-containing minerals; chlorine removal from the geomaterial; and tank leaching of gold. The total duration of heap leaching was 365 days, which was achieved by using two technological options: option 1 (195 days) — classic HL method (from early April to mid-October), option 2 (170 days) — heap leaching in stationary concrete cuvettes using engineering solutions during the period of subzero temperatures (from mid-October to the end of March). A schematic layout of the stationary concrete cuvette constructed in a special way and buried within a 5 to 8 m layer of soil above the ground level with shielding of the upper surface of the stack (heat-insulating covering, clay, large pieces of ore, sulfide rocks) is provided. Product solution drainage was used at various heights, and perforated rigid PVC pipes were used for supplying warm air deep inside the material. The recovery of gold from the technogenic raw materials was increased on average by 27.1 % due to a year-round heap leaching with the use of two technological options: 1 — by 28.7 % (from 58.1 to 86.8 %) using a classic HL method, and 2 — by 27.4 % (from 58.1 to 85.5 %) by using HL in stationary concrete cuvettes. It is proposed to utilize the secondary waste of the HL field (total of five types) in the road-building and construction industries.

Preparation of rigid cross-linked PVC foam with excellent thermal insulation through adding high-reflectivity IR opacifier

For polymer foams with low-density, the thermal radiation propagating through the foam still contributes significant to the total thermal transfer. It is very promising to enhance the absorption or reflection of IR radiation by the foam matrix. However, it is still a question which of the reflected infrared or absorbed infrared is more effective in reducing radiative thermal conductivity. In this work, we studied theoretically and experimentally the effectiveness to reduce the radiative thermal conductivity of polymer foams by reflection mode and absorption mode. The relationship between the optical parameters of foam and the heat radiation transmission in the foams was quantitatively investigated. It was found that, taking into account the re-emission, the radiative thermal conductivity was further reduced merely by increasing the absorption coefficient, but in theory it could continue to drop to zero by increasing the reflection fraction. Both the flake aluminum powder (FAP) that mainly reflects infrared and the flake graphite powder (FGP) that mainly absorbs infrared were added to the rigid cross-linked PVC (c-PVC) foam. The results demonstrated that the reduction of radiative thermal conductivity of the c-PVC foam with FAP was more significant than of the c-PVC foam with FGP. The experimental results were in good agreement with the theoretical prediction.

Surface modification of PVC by silica sol

One of the most important and widely used modern materials is polymeric composite materials based on PVC. One of the possible ways to improve the properties and increase the reliability of polymer products is their surface diffusion treatment with liquid nanomodifying components. The study investigated the possibility of using silica sol to strengthen the surface of rigid PVC. It is shown that as a result of diffusion impregnation of PVC in silica sol to a certain degree of saturation and subsequent heat treatment (in order to fix the modifier), the resulting composites have enhanced surface properties. As a result of the diffusion of silica sol into the PVC matrix and its physicochemical interaction with the latter, a modified surface layer is formed with a structure and properties that vary in its thickness. Modifying the surface of finished PVC products without changing the inner part, allows you to strengthen the whole material as a whole and increase its resistance to various external factors. At the same time, the consumption of the modifying additive is significantly reduced in comparison with the adding into the volume of the material, and its effectiveness increases due to the high local concentration on the surface.

Safety assessment of the substance (triethanolamine-perchlorate, sodium salt) dimer, for use in food contact materials.

The EFSA Panelon Food Contact Materials, Enzymes and Processing Aids (CEP) assessed the safety of the substance (triethanolamine-perchlorate, sodium salt) dimer, FCM substance No 1080, intended to be used as a thermal stabiliser at up to 0.15% w/w in rigid poly(vinyl chloride) (PVC) for repeated use bottles in contact with water. No thermal degradation of the substance is expected during the manufacture of the PVC articles. In water, the substance fully dissociates into triethanolamine, sodium (cations) and perchlorate. Therefore, migration would lead to exposure to triethanolamine and perchlorate and not to the substance itself. Specific migration of perchlorate, ethanolamine, diethanolamine and triethanolamine was tested under repeated use conditions covering the requested uses. After the second and third contacts, perchlorate was detected at ca. 0.3 μg/kg food. Ethanolamine, diethanolamine and triethanolamine were not detected in any of the three contacts at an estimated limit of detection of 0.03 mg/kg food. The available invitro studies on the substance confirmed the lack of concern for genotoxicity, as anticipated by the dissociation of the substance into authorised non-genotoxic substances. Therefore, the CEP Panelconcluded that the substance is not of safety concern for the consumer if used, under the condition requested by the applicant, as an additive at up to 0.15% w/w in rigid PVC for repeated use bottles intended for contact with water. Additionally, the migration of triethanolamine and perchlorate should not exceed the specific migration limits (SMLs) of 50 μg/kg food and 2 μg/kg food, respectively, set in the Regulation (EU) 10/2011. This evaluation also covers acidic foods such as fruit juices that can reasonably be foreseen to be in contact.

Extraction of the stabilizer from rigid and plasticized PVC

The efficiency of the developed model for predicting the kinetics of the stabilizer extraction from rigid and plasticized polyvinyl chloride was assessed. The model shows high efficiency in the predicting the kinetics of the stabilizer extraction from rigid polyvinyl chloride. The extraction of the stabilizer from the plasticized polyvinyl chloride proceeds in two stages and the kinetic dependences do not obey the model equation.

Use of copolymer of vinyl chloride with vinyl acetate as a compatibilizer of polyvinyl chloride with low density polyethylene

The influence of a vinyl chloride – vinyl acetate copolymer on the compatibility of polyvinyl chloride and low density polyethylene in the production of rigid PVC films by the calender method is considered.

Is the inferior occlusal plane a reliable anatomic landmark for inferior alveolar nerve block? A study on dry mandibles of Brazilian adults

To investigate the relationship between the mandibular foramen (MF) and the inferior occlusal plane (IOP) of anatomic specimens, in order to guide clinicians in the inferior alveolar nerve block (IANB). Eighty-two dry mandibles (totally or partially toothed) of Brazilian adults were selected, totalizing 66left and 66right antimeres. A flat plate of rigid PVC plastic was placed on the occlusal surfaces of posterior teeth and pressure was then manually applied to simulate the IOP. Following, the perpendicular distance from the IOP to the lowest point of the MF was measured by the use of a digital caliper, adopting negative values inferiorly and positive values superiorly. Regarding the antimeres, the majority of the lowest limits of the MF was below the IOP (right: 86.4%, left: 81.8%) with a mean of -4.2mm (±4.8) in the right and -4.1mm (±4.8) in the left ones, without any statistical significance. Considering both sexes, no statistically significant difference was obtained between them. The IOP seems not to be a good anatomical landmark to localize the MF and, its turn, to guide clinicians during the IANB for Brazilian adults, given the marked topographic variations.

Absorción Acústica de Jardines Verticales

Los jardines verticales forman parte de una de las tendencias tecnológicas constructivas más modernas, conocidas como “Greenery Systems”. Estas son aplicadas cada vez con más frecuencia en aquellas construcciones donde se priorizan consideraciones energéticas y ecológicas conciliables con el medio ambiente. Algunas de las características relevantes que presentan son la mejora del aislamiento térmico, el filtrado de polución ambiental, la absorción acústica, la retención de agua y una estética amigable. Los jardines verticales pueden poseer características acústicas disímiles entre ellos, debido a que dependen del tipo de soporte, sustrato y vegetación utilizada. Por ese motivo en la actualidad los datos existentes son muy variados e incompletos, y resulta necesario ampliar los mismos para disponer de mayores variantes constructivas con aplicación práctica. En este trabajo se estudió la absorción acústica de un sistema de jardín vertical del tipo modular. Cada módulo fue realizado sobre una base rígida de PVC, revestida de material fibroso, con el cual se conformaron bolsillos. En ellos se alojó el sustrato y la vegetación. Las especies vegetales que se utilizaron son algunas de las más difundidas en la región, a fin de lograr una buena adaptación y un mantenimiento sencillo.

Structural Changes Undergone During Thermal Aging and/or Processing of Unstabilized, Dry-blend and Rigid PVC, Investigated by FTIR-ATR and Curve Fitting

Structural Changes Undergone During Thermal Aging and/or Processing of Unstabilized, Dry-blend and Rigid PVC, Investigated by FTIR-ATR and Curve Fitting

A marine biofilm flow cell for in situ determination of drag and biofilm structure

It is not straightforward to link biofilm parameters to frictional drag, because of the heterogeneous distribution and viscoelasticity of the produced matrix. Here we present the design and calibration of a flow cell in which marine biofilms can be cultured under flow and then assessed for drag, structural and mechanical properties. The flow cell test section comprised a rectangular channel constructed by sandwiching together rigid PVC panels and side panels of clear acrylic, which allow natural light to enter. The Fanning friction factor (Cf) of the flow cell was found by measuring the pressure drop (ΔP) at various flow velocities (u). Flow cell calibration was carried out using a clean inert marine coating, and various roughness grades of sandpaper sheets to find Cf for each rigid roughness. ΔP was proportional to u2, indicating flow was turbulent (R2 = 0.99). The top panel of the flow cell can be substituted with a clear acrylic lid to allow simultaneous measurement of Cf and biofilm physico-mechanical properties by optical coherence tomography (OCT). Here, we demonstrated that the flow cell can be used to image microbial fouling using OCT. Future experiments will assess physico-mechanical and drag properties of marine fouling biofilms under flow.

Evaluation of the physical, mechanical and kinetic properties of some cereals and leguminous seeds in Benin republic

In order to design a seeder for direct sowing, a seed characterization study was conducted. The objective was to assess the physical, mechanical and kinetic properties of the most cultivated cereals and leguminous in Benin. Two varieties of Zea mays, four varieties of Vigna unguiculata, one variety of Arachis hypogea, one variety of Cajanus cajan and two varieties of Glycine maxwere studied. It was noticeda variation in physical parameters not only between species but also between varieties of the same species. All sphericity coefficients are greater than 0.7 with C. cajan which is more spherical (0.91±0.03) against the DMR ESR-W/QPM and 85 TZSR-W varieties of Z. mays which are the least spherical with 0.72±0.10 and 0.71±0.11 respectively. The rupture force generally increased from 14 to 720 N. Vigna TVX 32-36 is the most resistant with 633.3±75.72 N against 16.0±2.0 N for Arachis TS32-1 the least resistant. Overall, the falling speed decreased from 1.67 to 0 m/s on the rigid PVC, from 1.36 to 0 m/s on the black plate and from 1.67 to 0 m/s on the transparent hose when the angle of inclination increases from 20° to 70° relative to vertical. These parameters are essential for good sizing of the distribution system and the seed descent channels for a seeder. They can also be used for grains calibration and other use in agricultural engineering and food processing.Keywords: Seeds, physical properties, mechanical properties, kinetic properties, Benin

A novel treatment method of PVC-medical waste by near-critical methanol: Dechlorination and additives recovery

Before PVC-medical waste is subjected to a waste-to-energy recovery process, the dechlorination and the recovery of additives such as plasticizer, stabilizer, and lubricant are quite important and attractive. In this work, a novel process was developed for the dechlorination and the recovery of additives from PVC-medical waste such as tube for transfusion (TFT) and sample collector for urine (SCFU) by using near-critical methanol (NCM). Reaction temperature, solid-to-liquid ratio, and reaction time have significant effect on the dechlorination of TFT and SCFU in NCM. The order of dechlorination efficiency of the samples at the same reaction conditions is as follows: TFT > Pure PVC > SCFU. When reaction temperature was controlled at 250 °C (solid-to-liquid ratio of 1:10 g/mL, reaction time of 60 min), the dechlorination efficiency reached 90%. Plasticizer such as dibutyl phthalate (DBP), dioctyl phthalate (DOP), and dimethyl phthalate (DMP) could be efficiently extracted and recovered from TFT at 250 °C by the NCM process. The recovery efficiency of DBP, DOP, and DMP decreased significantly with increasing temperature due to the further decomposition and other secondary reactions. High level of hexadecanoic acid methyl ester and octadecanoic acid methyl ester can be obtained from SCFU at 250 °C by the NCM process because of the esterification between methanol and hexadecanoic acid/octadecanoic acid, which are the important stabilizers and lubricants generally used in rigid PVC. It is noteworthy that methanol can be circulated and reused in the NCM process. This result showed that the NCM process was beneficial for both the dechlorination and the additives recovery from PVC-medical waste, and had a widespread application prospect for the waste management of PVC wastes.