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.

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.

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.

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.

Sintesis Merkaptoetil Karboksilat sebagai Bahan Baku Stabiliser Termal Polivinil Klorida: Variasi Sumber Asam Lemak

Abstrak. Merkaptoetil karboksilat merupakan bahan baku stabiliser termal polivinil klorida atau polyvinyl chloride (PVC) berbasis timah organik. Stabiliser termal perlu ditambahkan ke dalam resin PVC sebelum diekstrusi untuk mencegah kerusakan karena pengerjaan panas. Stabiliser termal PVC dari timah organik dikenal sangat efektif, khususnya untuk aplikasi PVC kaku seperti pipa dan bingkai jendela. Penelitian ini bertujuan mengevaluasi sintesis merkaptoetil karboksilat dari asam lemak dan merkapto etanol dengan variasi sumber asam lemak yang meliputi asam lemak sawit, dedak padi dan biji kapuk. Percobaan dilakukan dalam sebuah reaktor partaian (batch) dengan asam kuat sebagai katalis. Percobaan dilakukan pada temperatur 60-80°C dan ekses merkapto etanol 10%. Kinerja sintesis dievaluasi melalui pengukuran kadar gugus merkaptan dan angka asam dalam produk serta perolehan produk. Pada rentang temperatur 60-80°C, ketiga asam lemak memberikan produk dengan kadar merkaptan pada rentang 6,4-7,8%. Temperatur 70°C merupakan temperatur terbaik karena menghasilkan produk dengan kadar merkaptan tertinggi tanpa memadat selama penyimpanan. Pada temperatur ini, produk memiliki angka asam pada rentang 11-41 mg KOH/g dan perolehan pada rentang 70-81%. Ketiga sumber asam lemak memberikan produk dengan kadar merkaptan yang mencukupi untuk dapat digunakan sebagai bahan baku stabiliser PVC. Mempertimbangkan kualitas produk dan ketersediaan di pasaran, distilat asam lemak sawit dipandang sebagai bahan baku yang paling baik. Kata kunci: asam lemak, merkaptoetil karboksilat, polivinil klorida, stabiliser termal. Abstract. Synthesis of Mercaptoethyl Carboxylate as Raw Materials for Polyvinyl Chloride Thermal Stabilizer: Variation in Fatty Acid Source. Mercaptoethyl carboxylate is a raw material for organotin-based polyvinyl chloride (PVC) thermal stabilizer. Thermal stabilizers need to be added to the PVC resin before extruded to prevent degradation due to heat treatment. Organotin PVC stabilizers are known to be very effective, especially for rigid PVC applications such as pipes and frames. This study was aimed to evaluate the synthesis of mercaptoethyl carboxylate from fatty acids and mercaptoethanol with various sources of fatty acids including palm, rice bran and kapok seed fatty acids. The experiment was carried out in a batch reactor with a strong acid as a catalyst. The experiments were conducted at 60-80°C and 10% mercapto ethanol excess. The performance of synthesis was evaluated by measuring mercaptan and acid contents and yield. In the range of 60-80°C, all three fatty acids provided products with mercaptan levels in the range of 6.4-7.8%. A temperature of 70°C is the best temperature as it gave a product with the highest mercaptan content without solidification during storage. At this temperature, the product had acid values in the range 11-41 mg KOH/g and yields in the range of 70-81%. Considering product quality and availability in the market, palm fatty acid distillate was seen as the best raw material. Keywords: fatty acid, mercaptoethyl carboxylate, polyvinyl chloride, thermal stabilizer. Graphical Abstract