Copolymer

ABS (Acrylonitrile-Butadiene-Styrene) is an amorphous terpolymer thermoplastic widely used for its combination of stiffness, toughness and excellent surface finish. Its three monomers contribute distinct properties: acrylonitrile (chemical resistance), butadiene (impact), styrene (processability). ## Key properties - Density: 1.04 – 1.07 g/cm³ - Continuous service temperature: -20 to 80 °C - HDT (Heat Deflection Temperature): 80 – 100 °C - Impact resistance: 200 – 500 J/m (notched Izod) - Mold shrinkage: 0.4 – 0.7 % (very low, typical of amorphous) ## Molding parameters - Melt temperature: 220 – 260 °C - Mold temperature: 40 – 80 °C - Pre-drying: 4 h at 80 – 90 °C (hygroscopic, absorbs 0.2 – 0.5 % moisture) - Moderate-to-high injection speed ## Typical applications - Appliances (vacuum cleaner housings, monitors) - Automotive (interior, grilles, panels) - Electronics (PC, phone housings) - Toys (LEGO® is ABS) - Non-sterile medical equipment ## Common defects Splay (silver streaks) from poorly removed moisture, brittleness from over-degradation in melt, yellow streaks on white parts from poor mixing, and poor paint adhesion without pre-treatment (flame or primer). ## Variants and blends - High-impact, high-flow, platable, FR (flame-retardant) ABS grades - PC/ABS: dominant blend in automotive interior and electronics - ASA: like ABS but UV-resistant (acrylate replaces butadiene)

Monomer is the small chemical molecule, with at least a double bond or a reactive functional group, that serves as the building block of polymers via the polymerization reaction. The plastics industry always starts from monomers, generally derived from petroleum or natural gas. ## High-volume monomers - Ethylene (CH₂=CH₂) → polyethylene (PE) - Propylene (CH₂=CH-CH₃) → polypropylene (PP) - Vinyl chloride (CH₂=CHCl) → PVC - Styrene (C₆H₅-CH=CH₂) → polystyrene (PS), ABS, SAN - Acrylonitrile, butadiene → ABS - Caprolactam → polyamide 6 (nylon 6) - Ethylene terephthalate → PET ## Polymerization mechanisms - Addition: the monomer's double bond opens to form chains (PE, PP, PS, PVC) - Condensation: two monomers react releasing a small molecule (water, ethanol). PA, PET, PC, PBT - Ring-opening: caprolactam → PA 6 - Catalysts: Ziegler-Natta, metallocene (PP), peroxides (PE), Phillips (HDPE) ## Monomer vs. polymer - Monomer: small molecule, e.g. styrene (liquid at room temp, soluble in water) - Polymer: macromolecule with thousands to millions of repeat units, e.g. polystyrene (solid at room temp) ## Industrial importance Monomer purity and quality determine the final polymer's properties. Residual monomer in the finished polymer may cause: - Unpleasant odor (residual styrene in PS) - Migration into food contact (vinyl chloride in PVC) - FDA / EU regulatory limits ## Residual monomer Typical levels in commercial polymers: <50 ppm for food grade, <200 ppm for industrial. Steam-stripping reduces residual.

Polymer is a macromolecule formed by the repeated covalent bonding of many small units called monomers. It is the molecular foundation of all plastics, rubbers, fibers and many biological materials (proteins, cellulose, DNA). ## Classification by origin - Natural: cellulose, starch, proteins, natural rubber, lignin - Synthetic: PE, PP, PVC, PS, PET, PA, PC, ABS… (most of the market) - Semi-synthetic: rayon, cellulose acetate, modified natural rubber derivatives ## Classification by architecture - Linear: straight chains (HDPE, PA 66, PS) - Branched: chains with branches (LDPE, ABS) - Crosslinked: PE-X, vulcanized rubber, thermosets - Dendritic: tree-like structures (specialty) ## Classification by thermal response - Thermoplastics: melt and reshape reversibly (PP, PE, PA, PC) - Thermosets: chemically cured, do not remelt (epoxy, phenolic) - Elastomers: flexible, recover shape after deformation (rubber, TPE) ## Classification by composition - Homopolymers: single monomer type (PE, PP-H) - Copolymers: two or more monomers (ABS = acrylonitrile + butadiene + styrene) - Blends: two polymers physically mixed (PC/ABS, PA/PPS) ## Key properties governed by structure - Molecular weight: stiffness and processability - Molecular-weight distribution: process window and toughness - Crystallinity: stiffness, opacity, shrinkage - Chain polarity: chemical resistance, adhesion, transparency

Thermoplastic is a polymer that softens and re-melts when heated above its melting or glass-transition temperature and solidifies again on cooling — with no permanent chemical reaction. This reversibility is what enables injection molding, extrusion and mechanical recycling of most plastics. ## Thermoplastic vs. thermoset - Thermoplastic: linear or branched chains without chemical crosslinks. Melts and can be remolded (PP, PE, ABS, PC, PA, PET, POM). - Thermoset: crosslinks chemically during cure (phenolic, epoxy, melamine resins). Cannot be remelted; reheating only degrades it. ## Classification of thermoplastics - Commodity: PP, PE-HD/LD, PS, PVC, PET → high volume, low cost - Engineering: ABS, PA (nylon), PC, POM, PMMA, PBT → improved mechanical properties - High-performance: PEEK, PPS, PSU, PEI, LCP → high service temperature, high cost - By structure: amorphous (PC, PS, ABS) vs. semi-crystalline (PP, PE, PA, POM) ## Processability Almost any thermoplastic can be injection-molded, extruded, thermoformed, blow-molded and roto-molded. Semi-crystalline grades require precise mold temperature to control crystallinity; amorphous grades tolerate wider windows. ## Recyclability and reuse Thermal reversibility allows scrap (regrind) to be ground and reprocessed up to 20 – 30 % mixed with virgin resin with no major property loss, depending on the polymer. Additives, cross-contamination with other resins, and accumulated thermal degradation limit the number of cycles.