Material Chemistry: Polymers (Plastics): The most common packaging material. Chemistry involves: Polymerization: How monomers (like ethylene, propylene, terephthalic acid) link to form chains (polyethylene, polypropylene, PET). Additives: Chemicals added to modify properties (e.g., plasticizers for flexibility, antioxidants to prevent degradation, UV stabilizers, slip agents, antimicrobials, colorants). Understanding their chemistry is vital for safety and performance. Structure-Property Relationships: How molecular structure (chain length, branching, crystallinity) affects mechanical strength, barrier properties, thermal behavior, and processability. Metals (Aluminum, Steel): Chemistry involves: Corrosion: Oxidation reactions and how coatings/lacquers (polymers, epoxies) prevent it. Coatings: Chemistry of lacquers applied to prevent metal-product interaction and corrosion. Recycling: Chemistry of melting, refining, and dealing with coatings/contaminants. Glass: Chemistry involves: Composition: Primarily silica (SiO?) with modifiers (soda ash Na?CO?, limestone CaCO?) to lower melting point and increase durability. Surface Treatments: Chemical coatings to improve strength, lubricity, or barrier properties. Chemical Inertness: Why glass is highly resistant to interaction with contents. Paper & Board: Chemistry involves: Fibers: Cellulose chemistry and how pulping/bleaching processes affect it. Coatings & Treatments: Chemistry of barrier coatings (e.g., PE, PLA, waxes, fluorochemicals), sizing agents (to control water absorption), and wet-strength resins. Inks & Adhesives: Chemistry of printing inks and glues used on paper. Barrier Properties & Permeation: Permeation: The process of gases (O?, CO?, N?), water vapor, aromas, or organic compounds dissolving into and diffusing through a packaging material. Chemistry's Role: The chemical structure of the material (e.g., polarity, crystallinity, free volume) dictates its permeability. For example: Highly polar materials (like EVOH) are excellent O? barriers but poor moisture barriers. Non-polar materials (like PP, PE) are good moisture barriers but poor O? barriers. Multi-layer structures combine chemistries to achieve optimal barriers (e.g., PET/Adhesive/EVOH/Adhesive/PE). Migration & Interaction: Migration: The transfer of chemical substances from the packaging material into the product (food, drug, cosmetic). This is a major safety concern. Sources: Monomers, additives (plasticizers, antioxidants), degradation products, printing inks, adhesives, contaminants. Chemistry's Role: Understanding the factors influencing migration: Chemical Nature: Polarity, molecular weight, solubility of the migrant and the product. Diffusion: How migrant molecules move through the polymer matrix. Partitioning: How the migrant distributes between the packaging and the product at the interface. Scalping/Absorption: The reverse process – absorption of desirable components (flavors, aromas, active ingredients) from the product into the packaging, reducing product quality. Degradation & Stability: Polymer Degradation: Chemical breakdown of packaging materials due to: Heat: Thermal oxidation (chain scission, crosslinking). Light (UV): Photo-oxidation, leading to embrittlement, discoloration, loss of barrier. Oxygen: Oxidation reactions. Moisture: Hydrolysis (especially for esters like PET or PLA). Chemistry's Role: Understanding degradation mechanisms and formulating stabilizers (antioxidants, UV absorbers) to prevent it. Also, studying how degradation products might migrate. Sustainability Chemistry: Recyclability: Designing polymers with compatible chemistries for efficient recycling streams. Understanding chemical contamination issues (e.g., inks, adhesives, barrier layers hindering recycling). Biodegradable/Compostable Materials: Chemistry of polymers derived from renewable resources (PLA, PHA, starch blends) and their enzymatic/hydrolytic degradation pathways under specific conditions. Renewable Feedstocks: Developing polymers from bio-based sources (sugars, plant oils) instead of fossil fuels. Reduction: Chemistry enabling thinner, stronger materials or active packaging that reduces material use/food waste. Analytical Chemistry in Packaging: Identification & Quantification: Using techniques like GC-MS, HPLC, FTIR, NMR, ICP-MS to identify and measure: Monomers, additives, and migrants in packaging materials. Migrants in the product (food simulant testing). Degradation products. Contaminants. Material Characterization: Determining molecular weight, crystallinity, thermal properties (DSC, TGA), surface properties. Migration Testing: Conducting experiments (often using food simulants) under controlled time/temperature conditions to measure migration levels and ensure compliance with regulations (e.g., FDA, EU). Why Packaging Chemistry Matters:

Safety: Preventing harmful chemical migration into food, drugs, or medical devices. Quality & Shelf-Life: Maintaining product flavor, color, texture, potency, and efficacy by protecting against oxygen, moisture, light, and microbial growth. Performance: Ensuring the package functions correctly (seal integrity, strength, processability). Regulatory Compliance: Meeting strict global regulations for materials in contact with food, pharmaceuticals, etc. Sustainability: Developing materials that are recyclable, compostable, or derived from renewable resources, and minimizing environmental impact. Innovation: Enabling new packaging technologies like active packaging (oxygen scavengers, antimicrobials), intelligent packaging (sensors), and high-performance barriers.