CPVC Pipe Compound High Chlorine Impact Modifiers
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Solution Overview
Problem
Current CPVC pipes fail to meet the higher safety and performance standards required for continuous service under elevated pressure and temperature conditions over a 50-year period, with a hydrostatic design basis (HDB) of 1250 psi at 100,000 hours, necessitating a reformulation to enhance notched Izod impact strength and heat distortion temperature.
Innovation Solution
A CPVC compound with a high chlorine content (66.5-70 wt.%) combined with specific amounts of high rubber impact modifiers, organotin stabilizers, chlorinated polyethylene, and inert fillers, such as carbon black or titanium dioxide, is formulated to achieve a HDB of at least 1250 psi and meet the cell class 2-4-4-8 requirements, providing improved safety and reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional CPVC formulation is used, then manufacturing cost and processing ease are maintained, but hydrostatic design basis and impact strength are insufficient for 50-year continuous service
Solution Approach 1:
The patent applies parameter changes by precisely controlling the chlorine content within 66.5-70 wt.% and impact modifier within 5-6 phr ranges. These narrowed parameter specifications transform the formulation from conventional broad ranges to optimized narrow ranges, achieving HDB of at least 1250 psi while maintaining manufacturing feasibility through defined processing parameters.
Solution Approach 2:
The patent creates a composite CPVC material system combining multiple components: CPVC resin (66.5-70 wt.% Cl), impact modifier (5-6 phr), stabilizer (1.25-3 phr), chlorinated polyethylene (1.5-3 phr), and inert filler (1-7 phr). This composite formulation achieves synergistic effects that produce HDB ≥1250 psi, exceeding conventional single-component CPVC formulations.
2Strength
If higher impact modifier content is used, then notched Izod impact strength is improved, but tensile strength and processing control deteriorate
Solution Approach 1:
The patent applies partial action by using a moderate amount of impact modifier (5-6 phr) rather than excessive quantities. This optimized dosage provides sufficient impact strength improvement while avoiding the negative effects of over-modification, maintaining tensile strength and processing control. The formulation achieves balance rather than maximizing single parameter.
Solution Approach 2:
The patent changes the impact modifier concentration parameter to a narrow range of 5-6 phr, which optimizes the balance between impact strength and tensile strength. This precise parameter control prevents the trade-off deterioration by identifying the optimal concentration point where both properties are satisfied.
3Temperature
If chlorine content is increased beyond 70 wt.%, then heat distortion temperature is improved, but processing difficulty and cost increase
Solution Approach 1:
The patent optimizes the chlorine content parameter to the range 66.5-70 wt.%, which provides sufficient heat distortion temperature for continuous service at elevated temperatures while maintaining processing ease and cost-effectiveness. This narrowed parameter range avoids the diminishing returns and increased complexity associated with higher chlorine contents.
Data Source
AI summary
CPVC pipe in diameters in the range from 15 mm (0.5 inch) to 15.24 cm (6 ins), to carry hot and cold aqueous streams under 690 KPa (100 psi) pressure and 82.2° C. (180° F.) in continuous service, is extruded from a compound in which the CPVC has a high Cl content in the range from 66.5%-70%, when modified with either of two specific impact high rubber modifiers in an amount greater than 5 parts but no more than 6 parts per 100 parts of CPVC. Extruded CPVC pipe provides a HDB measured according to ASTM D2837-01 which is 25% or more greater than that required for commercial pipe as specified in ASTM D2846. As a result, both SDR-11 and SDR-13.5 pipe are produced which provide a HDB of at least 1250 psi (8.62 MPa) at the 100,000 hr intercept.