Intrinsic Viscosity estimation of PET from MFR tests
Intrinsic Viscosity (I.V.) is a quantity related to the molecular weight of plastics and is typically monitored as a part of Quality Control procedures for materials like PET (poly-ethylene-terephthalate) and PA (poly-amides aka nylons). This is important since properties during processing and properties of the finished product show a significant dependence on it. Additionally, I.V. has some historical importance – it was defined in experimental Physics/Chemistry at the time of establishing the very existence of polymer molecules.
Even though the most common testing methods for I.V. imply the use of solvents (sometimes highly toxic), they are still used in the industry. The possibility of alternative methods has been investigated and several published papers exist on this subject.
As a starting point, the user still needs to measure I.V. by traditional procedures on a couple of reference samples. Then, in order to calibrate the correlation procedure, the MFR tests are carried out on the same samples. Given a series of samples with similar chemistry and composition, but having differences in the molecular weights, I.V. for each sample can be estimated by the software starting from the measured MFR value.
We were asked to test a series of PET samples by a company that produces and recycles packaging materials. The customer was already testing regular MFR, but was commissioning I.V. tests for each new batch to external laboratories.
The customer was experiencing inconsistent behavior of PET grades for injection molding that came from difference sources and the final product was sometimes affected by small bubbles on the surface. They were looking to resolve this issue by means of more frequent I.V. determinations. Some I.V. data were already available. To assist them, we performed MFR tests on several different samples: some from virgin material and some from recycled material of two different sources. We then utilized the software analysis that performs the empirical correlation.
Significant differences were consistently observed in the I.V. values estimated by the software for the different samples, demonstrating the possibility of discriminating between samples, and of indirectly predicting process behavior with an easy procedure. Interestingly, the required type of testing machine (melt flow tester) is already used by QC operators for standard MFR purposes, so the determination of I.V. with this method doesn’t require significant additional investment.
InstronCEAST MF50多砝码熔体流动速率测试仪根据MFR和MVR方法执行熔体流动速率（熔融指数）的测试，该方法完全符合ASTM D1238规程A，B，C，D和ISO 1133 A和B的规定，用于单砝码和多砝码测试。 多砝码测试最多可以执行5个砝码按递增，递减或自由顺序测试，并具有完全可程控的预热和测量步骤。 所有砝码均预装在机器里并且由机器执行砝码操作，无需操作员干预，从而消除了所有安全隐患。 直接接触式高分辨率编码器可测量活塞位移。 机筒中的温度曲线极其稳定且准确。 其他高级功能包括大触摸屏，用于全面的测试编程，管理和诊断功能，以及基于Windows CE的嵌入式PC，能够存储测试方法和测试结果。 通过USB和以太网端口轻松导出数据。 独特的应力传感器功能可支持压料和驱料功能。 还提供自动熔体切割和料筒清洁配件。
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