Our site uses cookies necessary for its proper functioning. To improve your experience, other cookies may be used: you can choose to disable them. This can be changed at any time via the Cookies link at the bottom of the page.


PENT test versus time to rupture curve for HDPE [PE]

 

Plastic Pipes Conference Association # 2010 Vancouver

E.Nezbedova

The service life for HDPE (PE 80, PE 100) materials used in plastic pipes application covers a time span of up 50 years. The new type of PE 100 (PE 100 RC) should achieve the life time over 100 years. Conventional hydrostatic pressure test to qualify a new resin must last 104 hours (ISO 1167). In the last twenty years two accelerated tests that produce the same type of brittle fracture that occurs in pipes after long time in service were developed and standardized (PENT and FNCT tests). In contrast to FNCT, PENT enables to follow the kinetics of slow crack growth (SCG) and estimates some relevant parameters (time for SCG initiation, rate of SCG and time to failure). These experimentally data, which can be described by exponential relationship in combination with numerical simulation of slow crack growth enable to described the part of time to rupture curve that is responsible for service lifetime. This procedure can substitute time consuming and expensive testing.

Please note that the whole article content is available on PPCA website only :

Related papers

2016 Berlin : Residual stress distribution in the extruded polyolefin pipes

Author(s) : Pavel Hutař, Jan Poduška, Jaroslav Kučera, Eva Nezbedová, Andreas Frank, Jiří Sadílek, Gerald Pinter

Residual stresses can significantly influence the lifetime of polymer pipes. Therefore, realistic estimation of residual hoop stress can contribute to accurate lifetime estimations. The previously used “accurate method” is quite time consuming and needs a lot of specimens to be prepared and treated. A simplified...

2012 Barcelona : Comparison of accelerated tests for PE grades lifetime assessment

Author(s) : Andreas Frank, Gerald Pinter, Mridula Kapur, E. Nezbedová

Results from cracked round bar tests (CRB) and pennsylvania notch tests (PENT) for several polyethylene (PE) pipe grades are compared. The CRB tests were conducted at 23 °C and 80 °C, the PENT tests only at 80 °C. A material ranking based on the CRB tests was in good accordance to PENT failure times, although a...

2006 Washington DC : Analysis of the Fracture Behaviour of Multi-Layer Pipes

Author(s) : Nezbedova, Vlach, Knesl

A multilayer pipe consisting of two different layers, namely of PE and PPH, was analysed. The relevant numerical model based on the Finite Element Method (FEM) was used to calculate the stress and strain distribution and to estimate the fracture characteristics. As variables the thickness of the material layers and...

2006 Washington DC : Effect of Processing on the Lifetime of Pipe HDPE Grade

Author(s) : Sindelar, Nezbedova, Buran

The influence of processing conditions on molecular structure and microstructure of highdensity polyethylene pipe material has been studied. By modifying the segment arrangement and package of additives, conditions during pelletising in the extruder have been changed. Structural analyses obtained by gel permeation...

2006 Washington DC : Full Notch Creep Test - ISO Round Robin Test

Author(s) : Niebergall, Mertlova, Nezbedova

Full Notch Creep Test (FNCT) is widely used to characterize the slow crack growth behavior of particularly pipe and blow moulding PE materials, especially in Europe. However, the validity of the FNCT data is not satisfactory, as the results show large variability so far. Among other SCG tests, which exist and are...

2004 Milan : Effect of structural parameters on RCP in polyethylene

Author(s) : Eva Nezbedová, Pavel Šindelář and Petr Bohatý

Changing the catalyst composition, it allowed us to alter placement of comonomer from lower to higher polymer molecular weight fractions together with a certain reduction of molecular weight distribution (MWD). Using this catalyst several polymer samples differing in level of branching, in comonomer unit placement and...

2001 Munich : Structural and Fracture Methods as Means of Predicting the Lifetime of HDPE Pipes

Author(s) : Nezbedova, Zahradnickova, Salajka

High-density polyethylene (HDPE) is being used more and more in critical long-term application, such as in pipes for the distribution of water and gas. For this reason it is important to have a strong understanding of those parameters which control the fracture behaviour of HDPE. The main parameters are : i. Chain...

1998 Gothenburg : Relationship between Toughness and Structural Parameter of PE-Copolymers

Author(s) : Nezbedova, Salajka, Kucera

Structural and morphological parameters together with processing conditions determine the type of fracture behaviour of polyethylenes. Long time brittle failure which occurs under low stresses and at room temperature limits the lifetime of polyethylens used as pipes for water and gas distribution. In order to...

Fracture Mechanics - Analysis of Multiplayer

Author(s) : Nezbedova, Knesl, Sestakova, Vlach

Members of the Association

BOREALISBOROUGEFormosa Plastics CorporationHanwha TotalEnergiesINEOS O&PIRPCKorea Petrochemical IND. Co., LTD (KPIC)LyondellBasellORLEN UnipetrolPetroChina Dushanzi Petrochemical CompanyPRIME POLYMERSABICSCG Chemicals & Thai PolyethyleneSinopecTASNEE