| Application and resin compatibility | Recommended polymer matrix, end use, processing method, and any application-specific restrictions. | Confirm that the modifier is intended for the actual resin and product, such as rigid PVC profiles, pipe, or molded parts. Compare candidates in the same formulation and process. | Prefer candidates supported by application-relevant test data rather than a general-purpose claim. |
| Impact performance | Notched impact strength, specimen dimensions, notch details, test temperature, conditioning, and test standard. | Use the same method and conditions for all candidates. ASTM D256 and ISO 180 are different methods; results should not be treated as directly interchangeable without a validated correlation. | Choose the candidate that meets the product’s impact requirement consistently, including at the relevant service temperature. |
| Modifier loading | Recommended dosage, normally expressed as phr where applicable; phr means parts by weight per 100 parts of resin. | Compare impact results at the same loading, or compare the loading needed to reach the same impact target. Keep other formulation ingredients constant. | A lower required loading can be useful only if processing, appearance, and other properties remain acceptable. |
| Low-temperature performance | Impact results at the specified low-temperature test points, with conditioning time and specimen details. | Compare results at identical temperatures and test conditions. Do not infer low-temperature performance from room-temperature data alone. | Require test data at the lowest temperature relevant to storage, transport, or end use. |
| Weathering and color retention | Exposure method, exposure duration, light source, water cycle, and measured changes such as color or impact retention. | For accelerated weathering, compare results only when the exposure procedure and evaluation method are the same. Accelerated exposure does not by itself establish a precise outdoor service life. | For outdoor products, request weathering data on the finished formulation or a clearly defined representative specimen. |
| Stiffness and heat performance | Flexural or tensile properties and, where relevant, Vicat softening temperature or another specified heat-resistance measure. | Check the trade-off between impact improvement and stiffness or heat performance using matched formulations and test methods. ISO 306 and ASTM D1525 are standard methods for Vicat testing. | Reject options that improve impact but cause the finished product to miss its required stiffness or heat-performance limits. |
| Processing behavior | Recommended processing window, fusion or melt behavior where relevant, torque or pressure observations, output, and surface quality. | Run a controlled production or pilot trial using the same equipment settings and formulation. Record stability, die or mold deposits, surface appearance, and scrap rate. | Good laboratory impact results should be supported by stable processing on the intended production line. |
| Batch consistency | Certificate of analysis (CoA), lot identification, specification limits, and historical variation for agreed critical properties. | Review multiple recent lots rather than relying on a single sample. Confirm that the CoA methods and limits match the purchasing specification. | Prefer suppliers that provide traceable lot data and promptly investigate out-of-specification results. |
| Physical properties and handling | Appearance, bulk density, moisture or volatile content, particle-size information if specified, packaging, and storage guidance. | Compare measurement methods and acceptance limits. Confirm that packaging and handling instructions suit the site’s storage and feeding equipment. | Clear specifications and practical handling guidance reduce avoidable variability in storage and dosing. |
| Quality-system evidence | Current quality-management certification, document control, change-control process, complaint handling, and corrective-action records. | Verify certificate scope and validity with the issuing body where appropriate. Ask how changes to product, process, or production site are communicated. | Look for documented controls and timely notification of changes, not certification claims alone. |
| Supply continuity | Production-site information, lead times, capacity planning, inventory policy, shipment performance, and contingency arrangements. | Assess continuity against the buyer’s forecast and risk tolerance. Confirm whether alternate production or logistics arrangements are qualified. | Favor a supplier able to explain and document how supply interruptions would be managed. |
| Technical support and documentation | Current technical data sheet (TDS), safety data sheet (SDS), application guidance, test reports, and access to technical troubleshooting. | Check revision dates, product identification, test conditions, and whether the data apply to the proposed grade and application. | Reliable technical support should provide specific, traceable answers and support validation trials. |
| Commercial and regulatory fit | Delivered cost, minimum order quantity, payment and delivery terms, and declarations required for the intended market. | Compare total landed cost and verify that any regulatory or customer-specific documentation is current and applicable to the finished product. | Do not treat a general compliance statement as proof of suitability for every product, market, or use. |
| Fair-comparison rule | Published figures are meaningful only when the grade, formulation, dosage, specimen preparation, conditioning, and test method are comparable. Confirm current specifications with the supplier and validate shortlisted candidates in the intended formulation and process. |
