I. 5: Additives for Plastics (Ref. A. Kumar and R. K I.5: Additives for Plastics (Ref. A. Kumar and R.K. Gupta, McGraw-Hill 1998) Plasticizers Fillers Coupling Agent Antioxidant and stabilizer Nucleating agent

Plastic Additives Function Types of additives (สารเสริมสภาพพลาสติก) Mechanical Properties Filler (สารตัวเติม) Impact modifier (สารปรับปรุงการกระแทก) Nucleating agent (สารก่อนิวเคลียส) Plasticizer - (สารเสริมสภาพพลาสติก) Fiber(เส้นใยเสริมแรง) Increase strength, reduce cost Increase impact resistance Increase no. of crystals Increase softness Increase strength and stiffness Surface Properties Anti-fogging(สารต้านการเกิดฝ้า) - Antistatic(สารต้านไฟฟ้าสถิต) Coupling agent(สารประสาน) Lubricant(สารหล่อลื่น) Prevent fog formation on the plastic film Prevent electrostatic discharge Improve interaction between fillers or fibers and polymers Prevent sticking

(สารคงสภาพแสง) Chemical Properties Antioxidant(สารกันออกซิเดชัน) -Moo Biocide(สารต้านจุลชีพ) - Fire retardant - Teuy (สารถ่วงการติดไฟ) UV stabilizer -Top (สารคงสภาพแสง) Prevent polymer degradation from oxidation Prevent damage from bacteria and fungi Reduce damage from catching fire Prevent degradation by UV light Aesthetic Biocide(สารต้านจุลชีพ) Colorant(สารให้สี) - Sine Nucleating agent (สารก่อนิวเคลียส) Fragrance(สารให้กลิ่น) Glossing agent (สารเพิ่มความสว่าง) Prevent rotten smell Add colors Improve transparency Improve aroma Add gloss and shine

Processing Foaming agent(สารฟู) Crosslinking agent (สารก่อพันธะเชื่อมโยง) Anti-foaming agent (สารลดฟอง) Emulsifier(สารก่ออิมัลชัน) Thermal stabilizer (สารคงสภาพทางความร้อน) Plasticizer (สารเสริมสภาพพลาสติก) Mold release (สารหล่อลื่น) Thickener(สารเพิ่มเนื้อ) Produce plastic foam Form crosslink reaction Reduce foam and bubbles Stabilize emulsion Prevent thermal degradation Reduce melt viscosity Prevent polymer sticking to mold Increase viscosity

Various additives to polyvinyl chloride

Plasticizers External plasticizer: low MW. Liq. that help increase mobility of high MW entangled polymers - the plasticizer reduces the polymer-polymer chain 2nd bonding softer, more easily deformable mass - performance – need plasticizer with low volatility MWsolvent < MWplasticizer < < MWpolymer

Internal plasticizer: making copolymer with soft polymer  get desirable product property at a particular temp. (whereas external plasticizer—get desirable product at a wider range of temp.) Example of internal plasticizer

Ex. PVC: has lots of external plasticizer and additives ex Ex. PVC: has lots of external plasticizer and additives ex. DOP (dioctyl phathalate) Unplasticized PVC -- rigid material used for pipes and fittings Plasticized PVC -- depend on level of plasticizer leather-like upholstery wire and cable covering shower curtains packaging film ex. Plastisols: 100 parts DOP phr + stabilizer + pigments low vis. suspension (~vis of plasticizer) melt film (flexible solid) suspension of PVC beads in plasticizer

Efficiency of plasticizer Select plasticizer with high solubility in & high compatibility to Polymer Matrix The more similar structure  the higher solubility, compatibility Ex. -Plasticizers have to stay inside the matrix w/o migration or blooming Plasticizer: Schematic drawing of polymer dissolution

สารประสาน (Coupling Agents) สารประสานหรือสารช่วยยึด (coupling agents or adhesion promoters) -function as a bridge/binder between polymers and fillers by forming a strong interaction between the two phases How to use coupling agents: 1. coating/adjusting the surfaces of fillers & fibers first, then mix with polymers 2. Mix the coupling agent directly with polymer and filler during compounding process (sometimes called compatibilizer)

Examples of some silane coupling agents

ฟิลเลอร์ (Fillers) Filler: solid additives put into polymers to reduce cost (extenders) or improve mechanical properties of polymers (active fillers) - Examples of เอกซ์เทนเดอร์ (extenders) or inert fillers are CaCO3 , talc, kaolin, wood dust - Examples of ฟังก์ชันแนลฟิลเลอร์ (functional fillers) or active fillers are reinforcing fillers –(reinforcing filler is functional filler to increase strength, especially tensile strength) Some polymers use large amount of fillers: PVC (พอลิไวนิลคลอไรด์), rubber(ยาง) Some polymers use low amount of fillers: PE, PMMA

Selection of Fillers Depends on price properties of fillers Required properties of products ex. For high tensile strength product, fillers need to be + hard/strong compared to polymer matrix + with high aspect ratio + disperse well in polymer matrices For high clarity, fillers need to + have similar refractive index as the polymer + Or need to be small in the nanometer range (nanoparticles) For high quality surface, filler size has to be small and round, or platy For low moisture adsorption, filler needs to absorb low moisture and have strong interaction with polymer.

Shapes and aspect ratios of different types of fillers

แอนติออกซิแดนซ์ (Antioxidant) Oxidation Mechanism When polymers react with oxygen, they form peroxide bonds (O-O). These bonds easily break into free radical (อนุมูลอิสระ) and break the polymer chains.

Roles of Different Types of Antioxidants

Anti-Oxidant Mechanism

Heat stabilizer (สเตบิไลเซอร์) In the polymer processing process, polymers are exposed to high temperature. The degradation of polymer during processing leads to changes in the color of polymers. Heat stabilizer is added to polymers to avoid degradation during processing related to high temperature.

BOX 2.2:Thermal degradation of some commercial polymers

BOX 2.2:Thermal degradation of some commercial polymers (con’t)

BOX 2.2:Thermal degradation of some commercial polymers (con’t)

สารก่อผลึก (Nucleating Agent) Nucleating agent helps in forming polymer crystals quickly thus having small crystal size. (ref. Milliken®, SpecialChem S.A.)

In the processing point of view: Appearance: Since light can pass through small crystals better than large crystals, nucleating agent thus - helps improve penetration of light through the polymer film and - improve clarity of the film. In the processing point of view: Small crystals shrinks in mold less than big crystals when cooled - plastic products can be removed from molds faster. - products maintain shape better when cooled