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条件设定
来源: | 作者:profed5ca94 | 发布时间: 2021-02-01 | 1582 次浏览 | 分享到:
PA分为芳香族聚酰胺和脂肪族聚酰胺,纯芳香族聚酰胺的熔融温度接近分解温度,不利于加工,故芳香族聚酰胺通常会在聚合过程中引入脂肪族成分,脂肪族聚酰胺分子中 —CONH— 是亲水基团,使聚酰胺具有亲水性,吸水性随分子中 —GH2— 比例的增加而减少,在相对湿度50%的平衡吸湿在2.0%左右,但在熔融状态下所充许的含湿量仅为0.15%,最好能小于0.10%。干燥方法可任选择一种:
2.2加工条件设定规则
2.2.1 PA类
2.2.1.1干燥
PA分为芳香族聚酰胺和脂肪族聚酰胺,纯芳香族聚酰胺的熔融温度接近分解温度,不利于加工,故芳香族聚酰胺通常会在聚合过程中引入脂肪族成分,脂肪族聚酰胺分子中 —CONH— 是亲水基团,使聚酰胺具有亲水性,吸水性随分子中 —GH2— 比例的增加而减少,在相对湿度50%的平衡吸湿在2.0%左右,但在熔融状态下所充许的含湿量仅为0.15%,最好能小于0.10%。干燥方法可任选择一种:
PA材料干燥好的物料在常温常压下最长放置时间不得超过60分钟。
2.2.1.2加工特性

注射工艺调整时将根据物料的不同,结合不同材料的熔点(PA6:223℃/PA66:254℃)及熔体流动状况,按模腔内的具体流向来确定调整方案。PA属于结晶型材料,在低于熔点时材料无流动的可能性,一旦材料温度达到熔点温度,流动性能极好。易于成型。
模温选择根据制件的最终使用要求而定,要求高刚性、高硬度时选用高的模温(80℃-120℃);要求柔韧性好时选用较低的模温(40℃-60℃),当塑件柔韧性好时对尺寸装配要求可放至最宽。

2.2.1.2退火/调湿后处理
调湿处理既将刚制成的塑料制件放入沸水或醋酸钾熔液中(醋酸钾熔液的配制为:水100份+醋酸钾1.25份),加热一定时间后取出使其自然冷却,加热时间跟据制件的壁厚给予确定,最长不超过60min。经过处理的塑件结晶率大大提高且极其均匀、细腻,故而整体强度有了很大的改善。根据制件的不同进行对比,找到最佳的处理工艺条件。退火后处理工艺参见表2方式。


2.2.2 聚酯类
2.2.2.1干燥
聚酯类(PBT、PET)属热熔比大的材料,在相对湿度50%的平均吸湿小于0.36%,但在熔融状下所充许的含湿量仅为0.02%,最好能小于0.01%。干燥方法可任选择一种:
干燥好的物料在常温常压下最长放置时间不得超过30分钟。

2.2.2.2加工特性
温度适应范围宽,工艺调整时选用调节压力来提升熔指比升温来改变流动性更有效。属易于加工的品种。但要考虑阻燃体系(阻燃体系含有一定少量的析出,处在非常活泼状态)的适应温度,当温差过大时,阻燃体系极易造成析出,使模塑过程中增加了清理模具时间,给连续生产带来不便。由于阻燃级PBT的体系活泼状态促使材料熔融过程中转化为气体的物质量较其它工程塑料多,故模具也应采用有合理排气通道的浇注填充系统,以利于气体的排出。聚酯类制件的后处理工艺参见表2方式。


2.2.3 PC类
2.2.3.1干燥
聚碳酸酯(PC)在相对湿度50%的平衡吸湿小于0.20%,吸水率小。但在熔融状态下所充许的含湿量仅为0.02%,最好能小于0.01%。干燥方法可任选择一种:
高于材料的上限温度时塑料开始少量软化、结块。PC干燥好的物料在常温常压下最长放置时间不得超过15分钟。

2.2.3.2加工特性
聚碳酸酯熔融温度高、粘度大,最大的特点是提高熔融温度所得的粘度降低远远高于提高射压而得到的粘度下降;所以在进行工艺调整时有效的方法是在物料的许可范围内升高料温,增加流动速率;温度每升高28℃时熔体流速增加1倍,剪切应力下降4倍;能很有效地减少注射成型制件内的残余压力。

2.2.3.3退火后处理
操作方法是将刚制成的塑件放入烘箱中加热一定时间后取出使其自然冷却,将内在集中的应力分散消除,PC选用的退火温度100℃~110℃×1小时,PC合金选用的退火温度85℃~100℃×1小时。经过退火后的塑件可放在四氯化碳、环已烷等溶剂中浸泡1-2分钟检查,与没经过退火的塑件进行对比,根据制件的不同找到最佳的退火工艺条件。


2.2.4 LTFPP类
聚丙烯(PP)熔融温度低、结晶速度慢,在相对湿度50%的平衡吸湿小于0.20%。原有的分子结构几乎不吸水。但鉴于用于高要求制件时,可考虑采用干燥处理使所得制品外观更好。
PP(属聚烯烃类)结晶型材料,热熔比大,典型的没到晶点温度时材料无位移流动的可能性,达到熔点温度即可流动。工艺调整时选用调节压力来提升熔指比升温来改变流动性更有效,加工温度范围宽,易于加工成型。
成型过程中模具温度对材料的结晶速度有决定性的影响,所以生产时应跟据制件不同的使用条件及尺寸要求要特别加以关注模温
针对塑件使用环境恶劣、尺寸精度要求高、塑件结构复杂的制件,应验证制件是否存在内应力。操作方法是将刚制成的塑件放入沸水中一定时间(10~20)min后取出使其自然冷却,将内在集中的应力分散消除,使结晶对尺寸所带来的影响得以固定。经过退火后的塑件在尺寸精度、综合机械性能上都是最佳状态,平时查对可将制件放入95℃中浸泡2min,拿出待其自然冷却,没发生翘曲表明已完全退火,在使用中将不会变形。




Conditions set


2.2 Processing conditions set rules


2.2.1 PA Class


2.2.1.1 Drying


PA is divided into aromatic polyamide and the aliphatic polyamide, aromatic polyamide pure melting temperature close to the decomposition temperature is not conducive to processing, so aromatic polyamide polymerization process is usually introduced in the aliphatic component, aliphatic polyamide molecules in-CONH-group is hydrophilic, so Polyamide is hydrophilic, water absorption with the elements in-GH2-ratio increases and reduces the relative humidity of 50% of the balance of moisture absorption of 2.0%, but in the molten state by filling the promise was only 0.15% moisture, preferably less than 0.10%. Drying method can either choose one:


PA material drying good material to place in the longest time under normal temperature and pressure should not exceed 60 minutes.


2.2.1.2 processing characteristics


Injection process adjustment will be based on different materials, combining different materials, the melting point (PA6: 223 ℃ / PA66: 254 ℃) and the melt flow conditions, according to the specific cavity flow to determine the adjustment program. PA is crystalline material, below the melting point in the flow of material without the possibility, once the material temperature reaches the melting point temperature, excellent flow properties. Easy to shape.


Mold temperature selected according to workpiece, end-use requirements may be, for high rigidity, high hardness, when used high mold temperature (80 ℃ -120 ℃); good flexibility required when opt for a lower mold temperature (40 ℃ -60 ℃ ), when the plastic parts with good flexibility when assembling size requirement can be put to the widest.


2.2.1.2 Annealing / after humidity treatment


Conditioned for both the newly made plastic workpieces into boiling water or molten potassium acetate (Preparation of molten potassium acetate: water 100 + 1.25 cent potassium acetate), heated to a certain time after the removal of natural cooling, According to the heating time to determine the thickness of workpieces, a maximum of 60min. Treated plastic parts greatly improve the crystallization rate and very uniform, fine, Guer overall strength has greatly improved. Compared according to different workpieces, to find the best treatment conditions. Table 2 after annealing treatment process approach.






2.2.2 Polyester


2.2.2.1 Drying


Polyester (PBT, PET) is a hot melt material than the larger, 50% in the average relative humidity is less than 0.36% moisture, but melted under the full promise of the moisture content of only 0.02%, preferably small at 0.01%. Drying method can either choose one:


Good material drying in the longest storage time under normal temperature and pressure should not exceed 30 minutes.


2.2.2.2 processing characteristics


Wide range of temperature adaptation, technology selection adjustment means adjusting the pressure to improve melt fluidity than the temperature to change more effectively. Species are easy to process. But we must consider flame retardant system (flame retardant system contains a certain small amount of precipitation, in a very lively state) to adapt the temperature, when the temperature difference is too large, the flame retardant system is very likely to precipitate an increase during the molding mold cleaning time to continuous production inconvenience. Flame Retardant PBT system as active status to promote the process of material into molten material on the gas more than other engineering plastics, it also should be reasonable mold channel gating filled exhaust system, to facilitate the discharge of gas. Polyester workpiece, way after the treatment process Table 2.


2.2.3 PC class


2.2.3.1 Drying


Polycarbonate (PC) in the balance of 50% relative humidity is less than 0.20% moisture absorption, water absorption small. However, it allows the molten state, the moisture content by only 0.02%, preferably less than 0.01%. Drying method can either choose one:


Higher than the maximum temperature of plastic materials began a small amount of softening, agglomeration. PC drying good material to place in the longest time under normal temperature and pressure should not exceed 15 minutes.


2.2.3.2 processing characteristics


Polycarbonate high melting temperature, viscosity, the biggest advantage is to increase the viscosity of lower melting temperature is much higher than income increased injection pressure and get the viscosity decreases; so effective during the adjustment process is in materials increase the extent permitted by the melt temperature, increase the flow rate; temperature rise 28 ℃, each increase of 1 times the melt flow rate, shear stress decreased by 4 times; can be very effective in reducing injection molding residual pressure within.


2.2.3.3 after annealing treatment


How is just made of plastic parts into the oven to heat after a certain time out to natural cooling, spread the elimination of internal stress concentration, PC selected annealing temperature 100 ℃ ~ 110 ℃ × 1 小时, PC alloy chosen annealing temperature of 85 ℃ ~ 100 ℃ × 1 小时. After annealing of plastic parts can be placed on carbon tetrachloride, cyclohexane and other solvents soak 1-2 minutes, checking, and no plastic parts after annealing are compared, according to different workpieces to find the best annealing conditions.






2.2.4 LTFPP class


Polypropylene (PP) with low melting temperature, crystallization is slow, the relative humidity of 50% of the balance is less than 0.20% moisture. The original molecular structure is almost non-absorbent. However, given the high demands for the workpiece, may be considered drying and makes the product look better.


PP (is a polyolefin) crystalline materials, hot melt ratio, typically not to the crystal point temperature flow of material without the possibility of displacement to achieve the melting temperature can be mobile. Adjust the pressure adjustment process used to enhance the melting temperature means to change the liquidity ratio of more effective processing temperature range, ease of processing molding.


Molding process the mold temperature on the crystallization rate of the material have a decisive impact, their production should be used with different conditions, according to workpiece and size requirements to give special attention to the mold temperature


Poor environment for the use of plastic parts, size, high precision, plastic structure of complex parts, should verify the existence of internal stress of workpiece. How is just made of plastic parts in boiling water in a certain time (10 ~ 20) min after the removal to natural cooling, spread the elimination of internal stress concentration, so that crystallization of the impact of size can be fixed. After annealed in size precision plastic parts, integrated mechanical performance is best, usually check into the workpiece can be immersed in 95 ℃ 2min, out let it cool naturally, did not happen warp that has been completely annealed , will not deform in use.