Every polyester mat spec sheet lists the same numbers: gram weight, tensile strength, elongation, heat resistance. Yet identical numbers from different suppliers often perform very differently on a membrane line. The reason sits in how the factory measures them — and whether the numbers reflect the roll you actually receive. This guide shows buyers how to test polyester mat quality before purchase, which tests matter most, and what target values to demand. A 20-minute test routine can prevent months of production trouble.
Test 1: Gram Weight (Basis Weight)
Gram weight tells you how much material sits in every square meter. To measure it, cut a sample of known area — typically 100 × 100 mm — dry it, weigh it, and convert the result to g/m². A 120g polyester mat should deliver 120 g/m², a 140g mat 140 g/m², and so on. Producers usually allow a tolerance of about ±5 percent; anything wider signals poor process control. This number matters commercially first: gram weight drives cost per square meter directly, and slight reductions in weight quietly raise profit margins at your expense. Our gram weight guide explains what 120g, 140g and 160g options each deliver in practice.
Test 2: Tensile Strength (MD and CD)
Tensile strength measures how much force the mat resists before it breaks. Testers cut a 50 mm wide strip, clamp both ends, and pull at a constant speed until rupture. The standard strip method for textile fabrics appears in ASTM D5035. Because a mat behaves differently along its length than across its width, test both directions: machine direction (MD) and cross direction (CD). For Guanlong’s spunbond polyester mat, typical values reach ≥230 N/5cm in MD and ≥200 N/5cm in CD. Low MD strength creates tears during coating; low CD strength invites splitting when workers unroll and lay the membrane on site.
Test 3: Elongation at Break
Elongation at break describes how far the mat stretches before it fails. During service, roof movement, thermal cycling and structural settlement all pull on the membrane, so the carrier needs room to flex. A spunbond polyester mat typically shows ≥13 percent elongation at 120g and ≥18 percent at 140g. Cotton or brittle carriers fail this test early, which explains why producers keep switching to polyester. When you review a test report, look for elongation measured together with tensile strength — the two values tell the real story. Finished-membrane standards such as EN 12311-1 for bitumen sheets rely on this same principle.
Test 4: Bitumen (Oil) Absorption
Bitumen absorption shows how well the mat takes up coating. Testers dip a sample into molten bitumen under controlled conditions and measure the weight gain. A high-absorption polyester mat saturates quickly and evenly, which shortens dwell time on the coating line and improves the bond between carrier and coating. Poor absorption produces dry spots, delamination risk and uneven thickness. Guanlong’s spunbond polyester mat carries an “excellent” bitumen absorption rating, and you can verify this property with a simple immersion test before committing to a full order.
Three More Checks Worth Doing
Beyond the four core tests, add three quick checks. First, heat resistance: the mat should tolerate at least 150°C without shrinking or stiffening, because SBS and APP coating lines run hot. Second, dimensional stability: measure the sample before and after heating to confirm uniform shape. Third, visual inspection: hold the roll up to light and look for holes, lumps, fiber clumps and uneven edges. These properties all trace back to the production process, which follows standard nonwoven principles that the Wikipedia overview of nonwoven fabrics summarizes.
How to Test Before You Commit
Put this routine to work before you sign anything. First, request a certificate of analysis (CoA) that states the test methods used. Next, ask for sample rolls from two or three different production batches and repeat the tests yourself or through an independent lab. After that, run a trial on your own coating line and check the finished membrane, not just the mat. A supplier who hesitates to share data usually has a reason. Weifang Guanlong Waterproof Materials Co., Ltd. publishes typical values openly, supports customer testing, and customizes width from 1.0 to 1.2 meters across its polyester mat range. For the technical background on why these numbers matter, read our article on how polyester mat strength translates into membrane performance, or contact our team for samples and test reports.
FAQ
Q1: What is the most important polyester mat quality test?
Tensile strength in both MD and CD, because it predicts coating-line performance and on-site handling. Combine it with gram weight, because a light mat rarely holds the promised strength.
Q2: What tolerance should I expect on gram weight?
About ±5 percent for a well-controlled line. Values beyond that range suggest inconsistent production, and they will show up as thickness variation in your finished membrane.
Q3: How do I test bitumen absorption myself?
Cut a sample of known weight, immerse it in molten bitumen at a controlled temperature for a set time, drain it, and weigh it again. The weight gain ratio indicates absorption capacity.
Q4: Which tensile value matters more: MD or CD?
Both matter, but for different reasons. MD strength resists tension during coating, while CD strength prevents splitting during unrolling and installation. Demand minimums in both directions.
Q5: What should a certificate of analysis include?
Gram weight, tensile strength (MD/CD), elongation at break, heat resistance and bitumen absorption, plus the test methods used and batch numbers. Without methods, numbers are just decoration.
