Commonly used environmental friendly flame retardants in heat shrinkable materials

In the production process of heat-shrinkable sleeve and other heat-shrinkable materials, flame retardants are often added to meet the requirements of product flame retardant. However, with the increasing awareness of global safety and environmental protection, people have higher and higher requirements for fire safety and product flame retardant. Halogen-free, low smoke, low toxicity environment-friendly flame retardants have become the pursuit of people. The goal. Then, what are the commonly used environmental friendly flame retardants in heat shrinkable materials?

At present, nearly 80% of the flame retardants used in plastic modification in China are halogen-containing flame retardants. Polybrominated diphenyl ethers and polybrominated biphenyls are the representatives. The brominated flame retardants have high efficiency, low dosage, little influence on the properties of materials and moderate price. Compared with other types of flame retardants, their efficiency/price ratio is more superior. 70%-80% of the electronic and electrical products for export in our country use this kind of flame retardant. However, the bromine-antimony flame retardant system produces a lot of smoke and corrosive gases during pyrolysis and combustion. In recent years, some European Union countries believe that the combustion of bromine flame retardants will produce toxic and carcinogenic PBDD and PBDF. In February 2003, the European Union issued two bans, RoHS and WEEE. RoHs (The Restriction of Hazrd OusSubstances Directive),It stipulates that all electronic and electrical equipment sold in European Union countries shall not contain PBBs and PBDEs as of January 1, 2006.

Common environmental friendly flame retardants in heat shrinkable materials:

Environmental friendly brominated flame retardants

1, ten bromo two phenyl ethane 8010

8010 is not a polybrominated diphenyl ether, and it is absolutely impossible to produce PBDD or PBDF in combustion; the relative molecular weight of 8010 is 971; the content of bromine is 82%, which is equivalent to the content of bromine in DBDPO (83%), so its flame retardancy is basically the same; the initial melting point is 345 and its thermal stability is higher than that of DBDPO (305); its light resistance and non-permeability are better than DBDPO, and most acceptable. Expensive is that its flame retardant plastic can be recycled, which is not the characteristics of many brominated flame retardants. 8010 industrial products are white crystalline powder with average particle size of 3 micron, free flow and micro-granularity. It is easy to disperse in plastic modification and the color of plastic products is free. Moreover, the cost of industrialization is equivalent to that of DBDPO, which is the most ideal substitute for DBDPO. As an additive brominated flame retardant, 8010 also needs to be used with antimony compounds in the use process, and the proportion of antimony compounds is the same as that of DBDPO/antimony compounds. Compared with DBDPO, 8010 is more suitable for engineering plastics with high temperature and high viscosity characteristics.

2. Brominated epoxy resin

Brominated epoxy resin used as flame retardant is also called tetrabromobisphenol A epoxy resin oligomer. Its bromine content can reach 50%, and its molecular weight is between 1000 and 45000. It can be divided into EP and EC types. Compared with EP and EC types, the former has better light resistance, but lower bromine content, while the latter has better impact strength. Commercial brominated epoxy resin is a mixture of opalescent semi-transparent wafer and white powder. Domestic brominated epoxy resin has irritating odor, while Israeli Dead Sea bromide products have no odor. Brominated epoxy resin has satisfactory melt flow rate, high flame retardant efficiency, excellent thermal stability and light stability, and can give flame retardant substrates good mechanical properties, products do not frost. Low phase molecular weight brominated epoxy resin is suitable for flame retardant ABS and HIPS, and high phase molecular weight is suitable for flame retardant ABS/PC alloy and engineering plastics such as PC, PET, PBT. It needs to be used in combination with antimony.

3, brominated polystyrene

The development of brominated polystyrene is similar to that of brominated epoxy resin, and it is also a fast developing flame retardant in recent years. Brominated polystyrene is white or light yellow powder or granule, bromine content is about 60%. The thermal decomposition temperature is higher than 310 C. It has the advantages of high molecular weight, good thermal stability, good dispersion and compatibility in polymers, easy processing and no frost. Brominated polystyrene is named brominated polystyrene and polybrominated styrene according to their synthetic routes. It can be seen from the nomenclature that brominated polystyrene is accomplished by brominating polystyrene. Polybrominated styrene is protected by vinyl bond first, then brominated, and then restored by vinyl bond. The brominated styrene was polymerized again. Whether solvent is used in the synthesis process can be divided into solvent method and non solvent method. As solvent consumption is low, it is usually synthesized by solvent method.

Two. Phosphorus flame retardants

1. Red phosphorus Masterbatch

Among the non-halogen flame retardants, red phosphorus is a better flame retardant, which has the advantages of less addition and wide use. Ordinary red phosphorus is easy to absorb moisture and has poor compatibility with macromolecule materials. It is especially easy to cause spontaneous combustion and can not be used in practice. Microencapsulated red phosphorus flame retardant reduces the activity of red phosphorus and solves the compatibility. The content of red phosphorus is about 85%, but the problem of spontaneous combustion has not been effectively solved, and the dust pollution is serious.

Red phosphorus masterbatch is a dark red particle, which is composed of red phosphorus and inorganic flame retardants such as aluminium hydroxide and expansive graphite. The safety problem has been solved. It has low smoke, high flame retardant efficiency, no dust pollution, excellent processing performance, low density, good thermal stability, less decline in physical properties of products, no frost, no migration, no corrosion in the process of processing. In particular, the product has a high resistance to leakage trace index (CTI), which has obvious advantages in the application of electronic and electrical appliances.

The main disadvantage of red phosphorus masterbatch is the tone problem. Besides dark red and black, it can not give products more color choices.

Red phosphorus masterbatch is used for flame retardant of general plastics, rubber, polyethylene, polypropylene and other oxygen-deficient materials.

热缩材料中常用的环保阻燃剂

在热缩套管及其他热缩材料生产过程中，经常会通过添加阻燃剂来达到产品阻燃的要求，然而随着全球安全环保意识的日益加强，人们对防火安全及制品阻燃的要求越来越高，无卤、低烟、低毒的环保型阻燃剂已成为人们追求的目标。那么，热缩材料中常用的环保阻燃剂有哪些呢？

目前国内塑料改性用阻燃剂近80%为含卤阻燃剂，其中以多溴二苯醚和多溴联苯类物质为代表，溴系阻燃剂效率高、用量少，对材料的性能影响小，且价格适中。和其它类型的阻燃剂相比，其效能/价格比更具有优越性，我国供出口电子电气类产品中70%～80%都用此类阻燃剂。但溴-锑阻燃体系在热裂解及燃烧时会生成大量的烟尘及腐蚀性气体，而且近年欧盟一些国家认为溴系阻燃剂燃烧时会产生有毒致癌的多溴代苯并恶瑛(PBDD)和多溴代二苯并呋喃(PBDF)，2003年2月，欧盟出台了RoHS和WEEE两个禁令，其中RoHs是限制有害物质的禁令(The Restriction of Hazrd OusSubstances Directive)，它规定自2006年1月1日起，在欧盟国家销售的所有电子电气设备，不能含有多溴联苯及多溴二苯醚。  

热缩材料中常见的环保型阻燃剂：

一、环保型溴系阻燃剂  

1、十溴二苯乙烷8010

8010不属于多溴二苯醚，在燃烧中绝对不可能产生PBDD或PBDF;8010的相对分子量为971;溴含量82%，和DBDPO含溴量相当(83%)，因此阻燃性能基本一致;初熔点345℃，热稳定性较DBDPO(305℃)高;它的耐光性以及不易渗析的特点都优于DBDPO，最可贵的是其阻燃的塑料可以回收使用，这是许多溴系阻燃剂所不具备的特点。8010工业品为平均粒度3μm、自由流动、微颗粒化的白色结晶粉末，在塑料改性中容易分散，塑料制品颜色自由。而且工业化成本和DBDPO相当，是DBDPO最为理想的替代品。作为添加型溴系阻燃剂，8010在使用过程也需要和锑化物配合使用，配合比例和DBDPO/锑化物比例相同;和DBDPO相比，8010更适用于高温高粘特性的工程塑料。

2、溴化环氧树脂

阻燃剂用溴化环氧树脂又称为四溴双酚A环氧树脂齐聚物，溴含量可达50%，分子量在1000~45000之间，分为EP型和EC型;EP型和EC型相比，前者的耐光性较好，但溴含量较低，而后者阻燃的ABS和HIPS具有较好的抗冲强度。商业品溴化环氧树脂是乳黄色半透名晶片和白色粉末的混合物，国产溴化环氧树脂有刺激性气味，而以色列死海溴产品则无气味。溴化环氧树脂具有令人满意的熔体流速和较高的阻燃效率，优良的热稳定性和光稳定性，且能赋予阻燃基材良好的机械性能，产品不起霜。低相分子量溴化环氧树脂适用于阻燃ABS和HIPS，高相分子量者适合于阻燃ABS/PC合金和PC，PET，PBT等工程塑料。它在使用过程需要和锑化物配合使用。

3、溴化聚苯乙烯

溴化聚苯乙烯的发展与溴化环氧树脂相类似，也是近年发展较快的一个阻燃剂品种。溴化聚苯乙烯为白色或淡黄色粉末或颗粒，溴含量在60%左右。热分解温度大于310℃，具有分子量大，热稳定性好，在高聚物中分散性和混容性好，易于加工，不起霜等优点。溴化聚苯乙烯依据其合成途径分别命名为溴化聚苯乙烯和聚溴化苯乙烯，从命名上可以看出溴化聚苯乙烯是通过对聚苯乙烯进行溴化来完成的;聚溴化苯乙烯是通过将苯乙烯首先进行烯键保护，然后进行溴化，再将烯键恢复，合成溴化苯乙烯，再次进行聚合完成的。从合成过程是否使用溶剂，又可以分为溶剂法和非溶剂法。由于溶剂法耗溴量少，所以人们通常采用溶剂法进行合成。

二、磷系阻燃剂

1、红磷母粒

在非卤阻燃剂中，红磷是一种较好的阻燃剂，具有添加量少、用途广泛等优点。普通红磷易吸潮，与高分子材料相容性差，特别容易引起自燃，不能实际使用。微胶囊化红磷阻燃剂，降低了红磷的活性，解决了相容性，红磷含量在85%左右，但自燃问题并没有得到有效的解决，粉尘污染严重。

红磷母粒是红磷与氢氧化铝、膨胀性石墨等无机阻燃剂复配使用、以基体树脂为载体的暗红色粒子，安全问题得到了解决。它低烟、阻燃效率高;无粉尘污染，加工性能优异;低密度、热稳定性好、制品物理性能下降少;加工过程中不起霜、不迁移、不腐蚀模具。特别是制品具有高耐漏电痕迹指数(CTI)，在电子电器应用上优势明显。

红磷母粒的主要缺点是色调问题，除了暗红和黑色外，无法赋予制品更多的颜色选择。

红磷母粒用于通用塑料、橡胶、聚乙烯、聚丙烯等缺少氧元素的材料的阻燃，最好与氢氧化镁、氢氧化铝复配使用;用于PET、PC、PBT、PA等富含氧元素的材料的阻燃，可单独使用;在加工过程中，为了达到红磷的最好分散性，可复配一定量的分散剂。

2、间苯二酚双(二苯磷酸酯)ReofosRDP

间苯二酚双(二苯磷酸酯)是高分子量有机膦系阻燃剂，表观为清澈液体;它磷含量高，磷含量为10.8%。具有高阻燃性，低添加量，对成品物性影响小的特点。它具有阻燃和增塑双重功能，可使阻燃剂完全实现无卤化、改善塑料成型中的流动加工性能和降低烧蚀，改善热老化性能，提高热变形温度，并可抑制燃烧后的残余物。

三、氮系阻燃剂

氮系阻燃剂为三聚氰胺及其与磷的化合物，主要是三聚氰胺、三聚氰胺氰尿酸和三聚氰胺磷酸酯，是阻燃剂市场最具有发展潜力的品种。氮系阻燃剂一般为白色晶状细粉末，粒径10μm～50μm，容易分散。密度1.5cm～1.7g/cm。作为阻燃剂新品种，氮系阻燃剂有很多优点：高效阻燃;不含卤素;无腐蚀作用，因而减少了机械被腐蚀问题;耐紫外光照;电性能好，在电子电器制品中优势最为明显;不褪色，不喷霜;可回收再利用。氮系阻燃剂目前主要应用在聚烯烃和聚酰胺中，不需要和其它阻燃剂配合使用。

四、无机阻燃剂

无机阻燃剂以氢氧化铝和氢氧化镁为主，目前国外已大量使用无机阻燃剂，其中美国、日本、西欧无机阻燃剂消费量分别占阻燃剂总消费量的60%、64%、50%。

氢氧化铝和氢氧化镁都为白色粉末，相对密度在2.4左右，粒径1～20μm。氢氧化铝开始脱水温度200℃，氢氧化镁开始脱水温度340℃。氢氧化镁热分解温度高，比氢氧化铝高出140℃，可以使添加氢氧化镁的合成材料能承受更高的加工温度，利于加快挤塑速度，缩短模塑时间，同时亦有助于提高阻燃效率。氢氧化镁粒径细，对设备磨损小，利于延长加工设备使用寿命。由于氢氧化镁与氢氧化铝相比有许多优点，因此氢氧化镁所占比例越来越大。氢氧化镁与同类无机阻燃剂相比，具有更好的抑烟效果。氢氧化镁在生产、使用和废弃过程中均无有害物质排放，而且还能中和燃烧过程中产生的酸性与腐蚀性气体。