POLYVINYL CHLORIDE (PVC) THERMAL CO-STABILIZER BASED ON PALM FATTY ACID

• Main Author: Dwi Aprilia, Elsa
• Format: Theses
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/87335
• Institution: Institut Teknologi Bandung

Polyvinyl chloride (PVC) is one of the most versatile polymers and ranks as the third-largest volume thermoplastic globally. PVC comes in various types used in different applications, tailored to particle size and K-value. PVC is easy to process and mold, its hardness can be adjusted, and it is not easily broken. However, this polymer is susceptible to heat damage. Thermal degradation in PVC, known as dehydrochlorination, occurs due to the presence of labile chloride atoms, specifically allylic and tertiary chlorides. Allylic chloride atoms form when the polymerization reaction is terminated, while tertiary chloride atoms form during polymerization with branching. Heating PVC causes these labile chloride atoms in the long PVC chain to release as HCl, generating new chloride atoms. The formed HCl acts as a catalyst for subsequent degradation reactions. Dehydrochlorination leads to discoloration and a decrease in mechanical strength, reducing performance and shortening the lifespan of PVC. Stabilizers are added to PVC resin to counteract dehydrochlorination during processing. Organic metal compound stabilizers, such as Ca/Zn carboxylates, are commonly used in the industry and serve as alternatives to lead-based stabilizers, which are being phased out due to environmental concerns. Ca/Zn stabilizers exhibit a "zinc burning" effect, which compromises their long-term stability. To enhance the stabilizing effect, metal compound stabilizers are supplemented with co-stabilizers. Pentaerythritol (PE) is a popular co-stabilizer due to its cost-effectiveness, good color retention, and long-term thermal stability. The performance of PE is attributed to its multiple hydroxyl groups. However, PE's high melting point means it remains solid at PVC processing temperatures, complicating distribution and slowing the stabilization reaction rate. Converting PE into monoester form is a solution to lower its melting point while retaining hydroxyl groups, thus maintaining its co-stabilizing role. This study focuses on synthesizing PE monoester as a co-stabilizer in a metal compound stabilizer system (Ca/Zn carboxylate). Palm fatty acid distillate (PFAD) is used as the carboxylic acid source. The synthesis of monoester involves varying reaction temperature, molar ratio of PFAD to PE, stirring method, and catalyst. The product is characterized through FTIR analysis, acid value, iodine value, and hydroxyl value. The co-stabilizing effect is evaluated through static and dynamic tests using calcium/zinc stearate as the metal compound stabilizer. The study finds that the optimal operating conditions for the esterification process are at a temperature of 150°C, with a PFAD to PE molar ratio of 1:4, using an overhead stirrer, and H2SO4 as the catalyst. These conditions produce a homogeneous product with a yield of 30.6%, a low acid value of 2.2 mg KOH/g, an iodine value of 29.7 g I2/100 g, a hydroxyl value of 59.3 mg KOH/g, an induction time increase of 243.1%, and a stability time increase of 266.3%.