Resin

A material data sheet (technical data sheet, TDS) is the document a resin supplier publishes for a specific grade, listing its tested properties and the conditions used to measure them. It is the starting reference for choosing a material and for setting up a molding process — not a guarantee for every part. ## What it contains - Rheological / processing: melt flow rate (MFR/MFI), recommended melt and barrel temperature, mold temperature, drying time/temperature and target moisture content, injection speed/pressure guidance. - Mechanical: tensile strength and modulus, elongation, flexural and impact (Izod/Charpy) values. - Thermal: heat deflection temperature (HDT), melting or softening point, continuous use temperature. - Physical: density / specific weight, mold contraction (shrinkage) — often different along and across flow, water absorption, flammability (UL94). ## How to read it Each value comes with a test standard (ISO or ASTM) and conditions; numbers are only comparable when the standards match. Most data is measured on dried virgin resin on standardized specimens, so real parts with regrind, fillers, weld lines or thin walls can differ. Use the sheet for drying and start-up settings, then confirm with your own process and parts. ## Related terms - See also: resin, moisture content, specific weight, contraction, regrind ## What is a material data sheet? A supplier document for a specific resin grade listing its tested mechanical, thermal, physical and processing properties, together with the test standards and conditions used to measure them. ## What information is on a material data sheet? Melt flow rate, recommended melt/mold temperatures, drying conditions and moisture target, density/shrinkage, plus tensile, flexural, impact and heat-deflection values — each tied to an ISO or ASTM test method. ## Why are data sheet values different from my real parts? Because the sheet is measured on dried virgin resin using standardized specimens; regrind, fillers, moisture, weld lines, wall thickness and your actual process all shift the real-world results.

A pellet (granule) is a small, uniform piece of resin — typically a 2–5 mm cylinder, lens or sphere — and the standard form in which thermoplastic is supplied to an injection molder. Pellets pour freely from the hopper, feed evenly into the screw, and melt consistently, which is exactly why raw plastic is pelletized rather than sold as powder or random chunks. ## Why plastic comes as pellets - Free flow & metering: uniform size gives steady, bridge-free feeding and repeatable melt in the barrel. - Built-in formulation: most pellets are already compounded — base polymer plus stabilizers, additives, reinforcements or color. Color can also be added as a masterbatch (highly pigmented pellets) blended with natural pellets. - Handling & storage: predictable bulk density makes dosing, drying and conveying repeatable; pellets are easier to dry than powder. ## Pellet vs other feed forms - virgin resin: first-use pellets straight from the producer, never melted. - regrind: reclaimed sprues/runners/scrap ground into flakes — irregular vs uniform pellets, so it flows and melts less consistently and is usually blended at a controlled ratio. - Powder/flake/repro: used in some processes but harder to feed evenly than pellets. ## What it means for molding Because pellets are the input, their dryness (moisture), bulk density and consistency drive shot-to-shot stability. Mixed pellet sizes, dust or excess regrind upset feeding and melting; that is why molders control storage, drying and regrind ratio. See pellet process for how pellets are made. ## Related terms - See also: resin, virgin resin, regrind, pellet process, hopper ## What is a plastic pellet? A small, uniform granule of thermoplastic resin — usually a 2–5 mm cylinder, lens or sphere — that is the standard feedstock for injection molding because it flows and melts consistently. ## Why is plastic supplied as pellets? Uniform pellets feed freely from the hopper into the screw and melt evenly, they can carry a complete compounded formulation (additives, reinforcement, color), and their predictable bulk density makes drying and dosing repeatable. ## What is the difference between a pellet and regrind? A pellet is a clean, uniform virgin granule; regrind is reclaimed scrap ground into irregular flakes. Regrind flows and melts less consistently, so it is usually blended with virgin pellets at a controlled percentage.

A plastic is a synthetic or semi-synthetic material whose backbone is a polymer — long chains of repeating molecular units — usually combined with additives that tune color, stability, flow and strength. The word "plastic" refers to its plasticity: when heated it can be shaped and then set into a solid part, which is exactly what injection molding exploits. ## Plastic vs polymer vs resin - polymer: the pure long-chain molecule (e.g. polyethylene). - Plastic: the usable material = polymer + additives, the everyday term for the finished compound. - resin: in a molding shop, the pelletized plastic fed into the machine. In practice molders use "resin," "plastic" and "material" almost interchangeably. ## The two families that matter for molding - thermoplastic: softens when heated and re-solidifies when cooled, reversibly — so it can be melted, molded, reground and re-melted. Virtually all injection molding uses thermoplastics. - thermoset: cures into a permanent crosslinked network and cannot be re-melted (e.g. epoxy, phenolic). Molded by different processes. ## Structure that drives behavior Thermoplastics are either amorphous (random chains — PC, ABS, PS: gradual softening, lower shrink, often clear) or semi-crystalline (ordered regions — PP, PA, POM: sharp melting, higher shrink, chemical resistance). This structure sets melt behavior, viscosity, shrinkage and where the molding process window lives. ## Related terms - See also: polymer, thermoplastic, thermoset, resin, additive ## What is plastic made of? A base polymer — long repeating molecular chains, usually from petrochemicals or increasingly bio/recycled sources — blended with additives such as stabilizers, colorants, lubricants and reinforcements to reach usable properties. ## What is the difference between a plastic and a polymer? A polymer is the pure long-chain molecule; a plastic is the usable material made from that polymer plus additives. In molding, the pelletized plastic fed to the machine is usually called resin. ## What kinds of plastic are used in injection molding? Almost always thermoplastics, which melt and re-solidify reversibly — split into amorphous grades (PC, ABS, PS) and semi-crystalline grades (PP, PA, POM); thermosets cure permanently and use other processes.

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

Virgin resin is plastic pellet that has never been melted or processed before — first-use material straight from the polymer producer, with no regrind or recycled content. It is the baseline against which a molder judges every other feedstock, because its properties match the material data sheet exactly. ## Why molders use virgin resin - Known, full properties: chains are at their original molecular weight, so strength, color and flow are as specified — no thermal history has degraded them. - Consistency: lot-to-lot behavior is predictable, which stabilizes the process and reduces scrap. - Regulated parts: medical, food-contact, optical and many cosmetic or safety parts often require 100 % virgin for traceability and purity. ## Virgin vs regrind vs recycled - Virgin: first use, never melted. - regrind: the shop's own runners/sprues/rejects ground up and re-fed — one extra heat history, usually blended with virgin at a controlled ratio (often 10–30 %). - Post-consumer recycled (PCR): reclaimed from used products; variable quality, frequently blended with virgin to hit a recycled-content target. ## The virgin/regrind balance Each reheating shortens polymer chains and can shift color and viscosity, so adding regrind saves cost and waste but too high a ratio degrades the part. Molders pick a blend percentage the part can tolerate, keep regrind clean and dry (it absorbs moisture fast), and run pure virgin where regulations or cosmetics demand it. ## Related terms - See also: resin, regrind, pellet, material data sheet, molded part ## What is virgin resin? Plastic resin in its first-use state — pellets from the producer that have never been melted, ground or recycled — so its mechanical, optical and flow properties match the data sheet exactly. ## What is the difference between virgin resin and regrind? Virgin resin has no prior heat history; regrind is the shop's own scrap (runners, sprues, rejects) ground and re-fed, carrying one extra melt cycle. Regrind is usually blended into virgin at a controlled percentage. ## Why use virgin resin instead of regrind? For full, predictable properties and lot consistency, and because medical, food-contact and optical parts often require 100 % virgin for purity and traceability; regrind saves cost but degrades slightly with each reheat.