Irradiation crosslinking is an important link in the production process of heat shrinkable pipe. The purpose of irradiation is to make the semi-finished product in the 60CoY ray or electric accelerator of high-energy electron beam radiation, the formation of a cross-linked network, that is, through irradiation processing so that the material to obtain a "shape memory effect."

Y radiation and electric beam radiation processing

Y-Ray is a high-energy photon, strong penetration ability, commonly used in large-size products and special-shaped parts of the radiation processing, the use of stacking or hanging basket transport irradiation. However, the Y-source dosage rate is low, the irradiation period is long, and the accompanying radiation oxidation is serious. Electric Beam is a high-energy charged particle, in the material penetration capacity is limited, more suitable for thin tubes, tablets, membranes and other products irradiation processing, electron beam dosage rate is high, radiation is instantaneous completion, accompanied by less radiation oxidation. At present, with the continuous improvement of power of industrial accelerator, especially energy, electron beam radiation processing has been more and more widely used in the irradiation production of thermal shrinkage products.

Cross-linked degree and performance

The cross-crosslinking degree determines the expansion process of the heat shrinkable tube and the shrinkage performance of the product. Cross-linked is not up to the requirements to improve the properties of the material, expansion stretching is difficult to ensure the uniformity of the product size, shrinkage can not fully restore to the expansion of the pre-tensile dimensions. Cross-linked through high will make the product hard and brittle even in the expansion of the stretching process cracking. For the optimal irradiation crosslinking degree of different materials, it must be determined by expansion stretching and heat shrinkage experiments.

The effect of high crosslinking degree uniformity on the performance of the product can not be ignored. Because of the low crosslinking degree, low strength, poor temperature resistance, expansion stretching, these places are first expanded and stretched, resulting in uneven stretching or cracking, especially when the large multiple expansion stretching is more likely to occur this phenomenon.

In order to ensure the quality of irradiation, in addition to the accelerator energy inhomogeneity, scanning inhomogeneity and other performance indicators to meet the requirements, but also the accelerator beam technology and equipment need to be studied. Accelerator electric beam irradiation can take the following measures or processes for quality control: it is advisable to monitor the absorbed dose during irradiation, and "8" type irradiation can be used for continuous irradiation of heat shrinkable tubes, and rotational irradiation can be used for intermittent heat shrinkable tubes.

热缩管的辐照工艺

辐照交联是热缩管生产过程中的重要环节。辐照的目的是使半成品在60CoY射线或电了加速器的高能电子束辐射下，高分了间形成交联网络，即通过辐照加工使材料获得“形状记忆效应”。

Y辐射和电予束辐射加工

Y射线是高能光子，穿透能力强，常用于大尺寸制品和异型件的辐射加工，采用堆照或吊篮输送辐照。但Y源剂量率较低，辐照周期长，伴随的辐射氧化严重。电予束是高能荷电粒子，在物质中的穿透能力有限，较适合薄型的管、片、膜等制品的辐照加工，电子束剂量率高，辐射是瞬间完成的，伴随的辐射氧化少。目前，随着工业用加速器功率特别是能量的不断提高，电子束辐射加工在热缩制品辐照生产中得到越来越广泛的应用。

交联度与性能

交联度高低决定了热缩管的扩张工艺性和产品的收缩性能。交联度过低达不到改善材料性能的要求，扩张拉伸时很难保证产品尺寸的均匀性，收缩时不能完全恢复到扩张拉伸前的外形尺寸。交联度过高又会使制品发硬变脆甚至在扩张拉伸过程中开裂。对于不同的材料最佳辐照交联度具体要达到多少，必须通过扩张拉伸和热收缩实验才能确定。

交联度高的均匀性对制品性能的影响也不可忽视。因为交联度低的地方，强度低，耐温性能差，扩张拉伸时，这些地方被首先扩张拉伸，从而造成扩张拉伸不均匀或开裂，特别是在大倍数扩张拉伸时更容易发生这种现象。

为保证辐照的质量，除加速器能量不均匀度、扫描不均匀度等性能指标满足要求外，还需要对加速器束下工艺及装置进行研究。加速器电予束辐照可采取以下措施或工艺进行质量控制：辐照过程中宜接监测吸收剂量；对于热缩管连续辐照可采用“8”字型辐照，对于断续热缩管可采用旋转辐照。