Sub-Committee of Experts on the Transport of Dangerous Goods

Forty-firstsession

Geneva, 25 June – 4 July 2012

Item 2 (b)of the provisional agenda

Explosives and related matters:
Screening test for substances that may have explosive properties

Changes to screening test for substances that may have explosive properties

Transmitted by the expert from Japanand by the International Council of Chemical Associations (ICCA)

Background

1. At the thirty-eight session the expert from Japan and ICCA jointly proposed to discuss exclusion of adiabatic calorimetry from the screening procedure described in subsection20.3.3.3 of the Manual of Tests and Criteria, where both adiabatic calorimetry and differential scanning calorimetry(DSC) are allowed to be used to measure the exothermic decomposition energy for the substances that may have explosive properties (ST/SG/AC.10/C.3/2010/60).

2.  The intention of this proposal was to improve the reliability of the screening test by standardizing the exothermic decomposition energy measurement.

3.  The proposal was accepted and this issue was discussed with further rationale at the thirty-ninth session after being reviewed by experts at the IGUS-EOS meeting (Washington DC, April, 2011) where no counterargument was presented against limiting the calorimetric method to DSC.

4.  At the thirty-ninth session, some experts expressed difficulty in limiting the calorimetric method to DSC. However, there was wide support for the proposal and a formal proposal for the forty-first session was anticipated (see ST/SG/AC.10/C.3/78, para. 20).

Discussion

5. This proposal to amend 20.3.3.3 of the Manual of Tests and Criteria has no intention to affect the choice of suitable calorimetric technique to evaluate thermal stability of substances such as determining SADT (Self Accelerating Decomposition Temperature). It only refers to suitable calorimetric technique to estimate exothermic decomposition energies of substances.

6. As described in ST/SG/AC.10/C.3/2010/60, it was experimentally observed that there were considerable disagreements between two exothermic decomposition energies of the very same samples; Q_DSC and Q_adia, measured by DSC and adiabatic calorimetry, respectively.

7. For the above reason, it is considered that allowing two different methods based on different principles to coexiston an equal basis makes it difficult to accomplish standardization of the exothermic decomposition energy measurement that is essential to improve the reliability of the screening test for substances that may have explosive properties.

8. In informal document INF.21 (thirty-ninth session), it was demonstrated that DSC has the advantage over adiabatic calorimetry in the measurement of the exothermic decomposition energy due to DSC’s approach in which heat loss and heat capacity are implicitly accounted for.

9.  Therefore, we consider that subsection 20.3.3.3 should be amended to indicate that DSC is a recommended method to measure exothermic decomposition energies of substances.

Proposal

10.  In 20.3.3.3 of the Manual of Tests and Criteria, it is proposed to amend the first sentence and add a new sentence after the first sentence as follows: “20.3.3.3   Thermal stability and exothermic decomposition energy may be estimated using a suitable calorimetric technique such as differential scanning calorimetry or adiabatic calorimetry. For estimating exothermic decomposition energy, a suitable calorimetric technique such as differential scanning calorimetry may be used.In using….”

联合国危险货物运输专家和全球化学品统一分类和标签制度专家委员会

危险货物运输专家分委员会

第四十一次会议

日内瓦， 2012年6月25日 – 2012年7月4日

议程第2 (b) 项

爆炸物和相关内容：对可能有爆炸性质的物质的筛选试验

 对可能有爆炸性质的物质筛选试验的修改

由日本专家和化学协会国际理事会(ICCA)提交

背景

1.  按照试验和标准手册20.3.3.3节，绝热量热仪和差示扫描量热仪（DSC）都可以作为放热分解能的测试手段，用于筛选可能具有爆炸性的物质。第38次会议上，日本和ICCA联合提议，将绝热量热仪从上述筛选程序中删除(ST/SG/AC.10/C.3/2010/60)。

2.  该提案的目的在于通过放热分解能测试方法的标准化，以此提高筛选试验的可靠性。

3.  IGUS-EOS会议上（华盛顿特区，2011年4月），参会专家在审阅提案后，对于将量热方法限定为DSC并无反对意见。此后， 39次会议接受了该提案，并就该问题的基本原理进行了进一步的讨论。

4.  第39次会议上，对于将量热方法限定为DSC，一些专家表示具有一定难处。不过，该提案还是获得了广泛的支持，并希望在41次会议上能够看到有正式文件提交。(见 ST/SG/AC.10/C.3/78，第20段)

 讨论

5.  本提案对于试验和标准手册的20.3.3.3节进行修订，目的只是在于选择合适的量热技术用于评估物质的放热分解能。但无意于影响在评价物质热稳定性（如SADT，自加速分解温度）时，对合适量热技术的选择。

6. 正如ST/SG/AC.10/C.3/2010/60中所述，通过DSC和绝热量热仪进行分别测试发现，即使是同一样品，获得的两个放热分解能Q_DSC 和 Q_adia,也存在很大的差异。

7. 基于上述原因，不难发现基于不同理论的两种不同方法同时存在于同一规则中，使放热分解能的测量标准化难以实现，而放热分解能的测量标准化对于提高潜在爆炸性物质的筛选试验是非常重要的。

8. 在39次会议上的非正式文件INF.21，说明了DSC在放热分解能测量方面比绝热量热仪更有优势，原因在于DSC方法的热损失率和热容对结果影响不大。

9.  由此，我们认为20.3.3.3节应该得到修订，来表明在放热分解能测试方面DSC是推荐的方法。

提议

10. 对于试验标准和手册的20.3.3.3节，建议修改第一句，并在第一句之后增加新句子如下：

“20.3.3.3 热稳定性和放热分解能可用适当的量热方法进行评估，如差示扫描量热法或绝热量热法。对于放热分解能的评估，可以使用合适的量热技术进行，如差示扫描量热法。在使用……